[Federal Register Volume 74, Number 239 (Tuesday, December 15, 2009)]
[Rules and Regulations]
[Pages 66495-66546]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E9-29537]



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Part V





Environmental Protection Agency





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40 CFR Chapter I



Endangerment and Cause or Contribute Findings for Greenhouse Gases 
Under Section 202(a) of the Clean Air Act; Final Rule

Federal Register / Vol. 74, No. 239 / Tuesday, December 15, 2009 / 
Rules and Regulations

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Chapter I

[EPA-HQ-OAR-2009-0171; FRL-9091-8]
RIN 2060-ZA14


Endangerment and Cause or Contribute Findings for Greenhouse 
Gases Under Section 202(a) of the Clean Air Act

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Administrator finds that six greenhouse gases taken in 
combination endanger both the public health and the public welfare of 
current and future generations. The Administrator also finds that the 
combined emissions of these greenhouse gases from new motor vehicles 
and new motor vehicle engines contribute to the greenhouse gas air 
pollution that endangers public health and welfare under CAA section 
202(a). These Findings are based on careful consideration of the full 
weight of scientific evidence and a thorough review of numerous public 
comments received on the Proposed Findings published April 24, 2009.

DATES: These Findings are effective on January 14, 2010.

ADDRESSES: EPA has established a docket for this action under Docket ID 
No. EPA-HQ-OAR-2009-0171. All documents in the docket are listed on the 
www.regulations.gov Web site. Although listed in the index, some 
information is not publicly available, e.g., confidential business 
information (CBI) or other information whose disclosure is restricted 
by statute. Certain other material, such as copyrighted material, is 
not placed on the Internet and will be publicly available only in hard 
copy form. Publicly available docket materials are available either 
electronically through www.regulations.gov or in hard copy at EPA's 
Docket Center, Public Reading Room, EPA West Building, Room 3334, 1301 
Constitution Avenue, NW., Washington, DC 20004. This Docket Facility is 
open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding 
legal holidays. The telephone number for the Public Reading Room is 
(202) 566-1744, and the telephone number for the Air Docket is (202) 
566-1742.

FOR FURTHER INFORMATION CONTACT: Jeremy Martinich, Climate Change 
Division, Office of Atmospheric Programs (MC-6207J), Environmental 
Protection Agency, 1200 Pennsylvania Ave., NW., Washington, DC 20460; 
telephone number: (202) 343-9927; fax number: (202) 343-2202; e-mail 
address: [email protected]. For additional information regarding 
these Findings, please go to the Web site http://www.epa.gov/climatechange/endangerment.html.

SUPPLEMENTARY INFORMATION: 

Judicial Review

    Under CAA section 307(b)(1), judicial review of this final action 
is available only by filing a petition for review in the U.S. Court of 
Appeals for the District of Columbia Circuit by February 16, 2010. 
Under CAA section 307(d)(7)(B), only an objection to this final action 
that was raised with reasonable specificity during the period for 
public comment can be raised during judicial review. This section also 
provides a mechanism for us to convene a proceeding for 
reconsideration, `` `[i]f the person raising an objection can 
demonstrate to EPA that it was impracticable to raise such objection 
within [the period for public comment] or if the grounds for such 
objection arose after the period for public comment (but within the 
time specified for judicial review) and if such objection is of central 
relevance to the outcome of this rule.' '' Any person seeking to make 
such a demonstration to us should submit a Petition for Reconsideration 
to the Office of the Administrator, Environmental Protection Agency, 
Room 3000, Ariel Rios Building, 1200 Pennsylvania Ave., NW., 
Washington, DC 20004, with a copy to the person listed in the preceding 
FOR FURTHER INFORMATION CONTACT section, and the Associate General 
Counsel for the Air and Radiation Law Office, Office of General Counsel 
(Mail Code 2344A), Environmental Protection Agency, 1200 Pennsylvania 
Ave., NW., Washington, DC 20004.
    Acronyms and Abbreviations. The following acronyms and 
abbreviations are used in this document.

ACUS Administrative Conference of the United States
ANPR Advance Notice of Proposed Rulemaking
APA Administrative Procedure Act
CAA Clean Air Act
CAFE Corporate Average Fuel Economy
CAIT Climate Analysis Indicators Tool
CASAC Clean Air Scientific Advisory Committee
CBI Confidential Business Information
CCSP Climate Change Science Program
CFCs chlorofluorocarbons
CFR Code of Federal Regulations
CH4 methane
CO2 carbon dioxide
CO2e CO2-equivalent
CRU Climate Research Unit
DOT U.S. Department of Transportation
EO Executive Order
EPA U.S. Environmental Protection Agency
FR Federal Register
GHG greenhouse gas
GWP global warming potential
HadCRUT Hadley Centre/Climate Research Unit (CRU) temperature record
HCFCs hydrochlorofluorocarbons
HFCs hydrofluorocarbons
IA Interim Assessment report
IPCC Intergovernmental Panel on Climate Change
MPG miles per gallon
MWP Medieval Warm Period
N2O nitrous oxide
NAAQS National Ambient Air Quality Standards
NAICS North American Industry Classification System
NASA National Aeronautics and Space Administration
NF3 nitrogen trifluoride
NHTSA National Highway Traffic Safety Administration
NOAA National Oceanic and Atmospheric Administration
NOI Notice of Intent
NOX nitrogen oxides
NRC National Research Council
NSPS new source performance standards
NTTAA National Technology Transfer and Advancement Act of 1995
OMB Office of Management and Budget
PFCs perfluorocarbons
PM particulate matter
PSD Prevention of Significant Deterioration
RFA Regulatory Flexibility Act
SF6 sulfur hexafluoride
SIP State Implementation Plan
TSD technical support document
U.S. United States
UMRA Unfunded Mandates Reform Act of 1995
UNFCCC United Nations Framework Convention on Climate Change
USGCRP U.S. Global Climate Research Program
VOC volatile organic compound(s)
WCI Western Climate Initiative
WRI World Resources Institute

TABLE OF CONTENTS

I. Introduction
    A. Overview
    B. Background Information Helpful To Understand These Findings
    1. Greenhouse Gases and Transportation Sources Under CAA Section 
202(a)
    2. Joint EPA and Department of Transportation Proposed 
Greenhouse Gas Rule
    C. Public Involvement
    1. EPA's Initial Work on Endangerment
    2. Public Involvement Since the April 2009 Proposed Endangerment 
Finding
    3. Issues Raised Regarding the Rulemaking Process
II. Legal Framework for This Action
    A. Section 202(a) of the CAA--Endangerment and Cause or 
Contribute
    1. The Statutory Framework
    2. Summary of Response to Key Legal Comments on the 
Interpretation of the CAA Section 202(a) Endangerment and Cause or 
Contribute Test

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    B. Air Pollutant, Public Health and Welfare
III. EPA's Approach for Evaluating the Evidence Before It
    A. The Science on Which the Decisions Are Based
    B. The Law on Which the Decisions Are Based
    C. Adaptation and Mitigation
    D. Geographic Scope of Impacts
    E. Temporal Scope of Impacts
    F. Impacts of Potential Future Regulations and Processes that 
Generate Greenhouse Gas Emissions
IV. The Administrator's Finding That Emissions of Greenhouse Gases 
Endanger Public Health and Welfare
    A. The Air Pollution Consists of Six Key Greenhouse Gases
    1. Common Physical Properties of the Six Greenhouse Gases
    2. Evidence That the Six Greenhouse Gases Are the Primary Driver 
of Current and Projected Climate Change
    3. The Six Greenhouse Gases Are Currently the Common Focus of 
the Climate Change Science and Policy Communities
    4. Defining Air Pollution as the Aggregate Group of Six 
Greenhouse Gases Is Consistent With Evaluation of Risks and Impacts 
Due to Human-Induced Climate Change
    5. Defining the Air Pollution as the Aggregate Group of Six 
Greenhouse Gases Is Consistent With Past EPA Practice
    6. Other Climate Forcers Not Being Included in the Definition of 
Air Pollution for This Finding
    7. Summary of Key Comments on Definition of Air Pollution
    B. The Air Pollution Is Reasonably Anticipated To Endanger Both 
Public Health and Welfare
    1. The Air Pollution Is Reasonably Anticipated To Endanger 
Public Health
    2. The Air Pollution Is Reasonably Anticipated To Endanger 
Public Welfare
V. The Administrator's Finding That Greenhouse Gases From CAA 
Section 202(a) Sources Cause or Contribute to the Endangerment of 
Public Health and Welfare
    A. The Administrator's Definition of the ``Air Pollutant''
    B. The Administrator's Finding Whether Emissions of the Air 
Pollutant From Section 202(a) Source Categories Cause or Contribute 
to the Air Pollution That May Be Reasonably Anticipated To Endanger 
Public Health and Welfare
    C. Response to Key Comments on the Administrator's Cause or 
Contribute Finding
    1. The Administrator Reasonably Defined the ``Air Pollutant'' 
for the Cause or Contribute Analysis
    2. The Administrator's Cause or Contribute Analysis Was 
Reasonable
VI. Statutory and Executive Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From 
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations
    K. Congressional Review Act

I. Introduction

A. Overview

    Pursuant to CAA section 202(a), the Administrator finds that 
greenhouse gases in the atmosphere may reasonably be anticipated both 
to endanger public health and to endanger public welfare. Specifically, 
the Administrator is defining the ``air pollution'' referred to in CAA 
section 202(a) to be the mix of six long-lived and directly-emitted 
greenhouse gases: carbon dioxide (CO2), methane 
(CH4), nitrous oxide (N2O), hydrofluorocarbons 
(HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride 
(SF6). In this document, these six greenhouse gases are 
referred to as ``well-mixed greenhouse gases'' in this document (with 
more precise meanings of ``long lived'' and ``well mixed'' provided in 
Section IV.A).
    The Administrator has determined that the body of scientific 
evidence compellingly supports this finding. The major assessments by 
the U.S. Global Climate Research Program (USGCRP), the 
Intergovernmental Panel on Climate Change (IPCC), and the National 
Research Council (NRC) serve as the primary scientific basis supporting 
the Administrator's endangerment finding.\1\ The Administrator reached 
her determination by considering both observed and projected effects of 
greenhouse gases in the atmosphere, their effect on climate, and the 
public health and welfare risks and impacts associated with such 
climate change. The Administrator's assessment focused on public health 
and public welfare impacts within the United States. She also examined 
the evidence with respect to impacts in other world regions, and she 
concluded that these impacts strengthen the case for endangerment to 
public health and welfare because impacts in other world regions can in 
turn adversely affect the United States.
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    \1\ Section III of these Findings discusses the science on which 
these Findings are based. In addition, the Technical Support 
Document (TSD) accompanying these Findings summarizes the major 
assessments from the USGCRP, IPCC, and NRC.
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    The Administrator recognizes that human-induced climate change has 
the potential to be far-reaching and multi-dimensional, and in light of 
existing knowledge, that not all risks and potential impacts can be 
quantified or characterized with uniform metrics. There is variety not 
only in the nature and potential magnitude of risks and impacts, but 
also in our ability to characterize, quantify and project such impacts 
into the future. The Administrator is using her judgment, based on 
existing science, to weigh the threat for each of the identifiable 
risks, to weigh the potential benefits where relevant, and ultimately 
to assess whether these risks and effects, when viewed in total, 
endanger public health or welfare.
    The Administrator has considered how elevated concentrations of the 
well-mixed greenhouse gases and associated climate change affect public 
health by evaluating the risks associated with changes in air quality, 
increases in temperatures, changes in extreme weather events, increases 
in food- and water-borne pathogens, and changes in aeroallergens. The 
evidence concerning adverse air quality impacts provides strong and 
clear support for an endangerment finding. Increases in ambient ozone 
are expected to occur over broad areas of the country, and they are 
expected to increase serious adverse health effects in large population 
areas that are and may continue to be in nonattainment. The evaluation 
of the potential risks associated with increases in ozone in attainment 
areas also supports such a finding.
    The impact on mortality and morbidity associated with increases in 
average temperatures, which increase the likelihood of heat waves, also 
provides support for a public health endangerment finding. There are 
uncertainties over the net health impacts of a temperature increase due 
to decreases in cold-related mortality, but some recent evidence 
suggests that the net impact on mortality is more likely to be adverse, 
in a context where heat is already the leading cause of weather-related 
deaths in the United States.
    The evidence concerning how human-induced climate change may alter 
extreme weather events also clearly supports a finding of endangerment, 
given the serious adverse impacts that can result from such events and 
the increase in risk, even if small, of the occurrence and intensity of 
events such as hurricanes and floods. Additionally, public health is 
expected to be

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adversely affected by an increase in the severity of coastal storm 
events due to rising sea levels.
    There is some evidence that elevated carbon dioxide concentrations 
and climate changes can lead to changes in aeroallergens that could 
increase the potential for allergenic illnesses. The evidence on 
pathogen borne disease vectors provides directional support for an 
endangerment finding. The Administrator acknowledges the many 
uncertainties in these areas. Although these adverse effects provide 
some support for an endangerment finding, the Administrator is not 
placing primary weight on these factors.
    Finally, the Administrator places weight on the fact that certain 
groups, including children, the elderly, and the poor, are most 
vulnerable to these climate-related health effects.
    The Administrator has considered how elevated concentrations of the 
well-mixed greenhouse gases and associated climate change affect public 
welfare by evaluating numerous and far-ranging risks to food production 
and agriculture, forestry, water resources, sea level rise and coastal 
areas, energy, infrastructure, and settlements, and ecosystems and 
wildlife. For each of these sectors, the evidence provides support for 
a finding of endangerment to public welfare. The evidence concerning 
adverse impacts in the areas of water resources and sea level rise and 
coastal areas provides the clearest and strongest support for an 
endangerment finding, both for current and future generations. Strong 
support is also found in the evidence concerning infrastructure and 
settlements, as well ecosystems and wildlife. Across the sectors, the 
potential serious adverse impacts of extreme events, such as wildfires, 
flooding, drought, and extreme weather conditions, provide strong 
support for such a finding.
    Water resources across large areas of the country are at serious 
risk from climate change, with effects on water supplies, water 
quality, and adverse effects from extreme events such as floods and 
droughts. Even areas of the country where an increase in water flow is 
projected could face water resource problems from the supply and water 
quality problems associated with temperature increases and 
precipitation variability, as well as the increased risk of serious 
adverse effects from extreme events, such as floods and drought. The 
severity of risks and impacts is likely to increase over time with 
accumulating greenhouse gas concentrations and associated temperature 
increases and precipitation changes.
    Overall, the evidence on risk of adverse impacts for coastal areas 
provides clear support for a finding that greenhouse gas air pollution 
endangers the welfare of current and future generations. The most 
serious potential adverse effects are the increased risk of storm surge 
and flooding in coastal areas from sea level rise and more intense 
storms. Observed sea level rise is already increasing the risk of storm 
surge and flooding in some coastal areas. The conclusion in the 
assessment literature that there is the potential for hurricanes to 
become more intense (and even some evidence that Atlantic hurricanes 
have already become more intense) reinforces the judgment that coastal 
communities are now endangered by human-induced climate change, and may 
face substantially greater risk in the future. Even if there is a low 
probability of raising the destructive power of hurricanes, this threat 
is enough to support a finding that coastal communities are endangered 
by greenhouse gas air pollution. In addition, coastal areas face other 
adverse impacts from sea level rise such as land loss due to 
inundation, erosion, wetland submergence, and habitat loss. The 
increased risk associated with these adverse impacts also endangers 
public welfare, with an increasing risk of greater adverse impacts in 
the future.
    Strong support for an endangerment finding is also found in the 
evidence concerning energy, infrastructure, and settlements, as well 
ecosystems and wildlife. While the impacts on net energy demand may be 
viewed as generally neutral for purposes of making an endangerment 
determination, climate change is expected to result in an increase in 
electricity production, especially supply for peak demand. This may be 
exacerbated by the potential for adverse impacts from climate change on 
hydropower resources as well as the potential risk of serious adverse 
effects on energy infrastructure from extreme events. Changes in 
extreme weather events threaten energy, transportation, and water 
resource infrastructure. Vulnerabilities of industry, infrastructure, 
and settlements to climate change are generally greater in high-risk 
locations, particularly coastal and riverine areas, and areas whose 
economies are closely linked with climate-sensitive resources. Climate 
change will likely interact with and possibly exacerbate ongoing 
environmental change and environmental pressures in settlements, 
particularly in Alaska where indigenous communities are facing major 
environmental and cultural impacts on their historic lifestyles. Over 
the 21st century, changes in climate will cause some species to shift 
north and to higher elevations and fundamentally rearrange U.S. 
ecosystems. Differential capacities for range shifts and constraints 
from development, habitat fragmentation, invasive species, and broken 
ecological connections will likely alter ecosystem structure, function, 
and services, leading to predominantly negative consequences for 
biodiversity and the provision of ecosystem goods and services.
    There is a potential for a net benefit in the near term \2\ for 
certain crops, but there is significant uncertainty about whether this 
benefit will be achieved given the various potential adverse impacts of 
climate change on crop yield, such as the increasing risk of extreme 
weather events. Other aspects of this sector may be adversely affected 
by climate change, including livestock management and irrigation 
requirements, and there is a risk of adverse effect on a large segment 
of the total crop market. For the near term, the concern over the 
potential for adverse effects in certain parts of the agriculture 
sector appears generally comparable to the potential for benefits for 
certain crops. However, The body of evidence points towards increasing 
risk of net adverse impacts on U.S. food production and agriculture 
over time, with the potential for significant disruptions and crop 
failure in the future.
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    \2\ The temporal scope of impacts is discussed in more detail in 
Section III.C. The phrase ``near term'' as used in this document 
generally refers to the current time period from and the next few 
decades. The phrase ``long term'' generally refers to a time frame 
extending beyond that to approximately the middle to the end of this 
century.
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    For the near term, the Administrator finds the beneficial impact on 
forest growth and productivity in certain parts of the country from 
elevated carbon dioxide concentrations and temperature increases to 
date is offset by the clear risk from the observed increases in 
wildfires, combined with risks from the spread of destructive pests and 
disease. For the longer term, the risk from adverse effects increases 
over time, such that overall climate change presents serious adverse 
risks for forest productivity. There is compelling reason to find that 
the support for a positive endangerment finding increases as one 
considers expected future conditions where temperatures continue to 
rise.
    Looking across all of the sectors discussed above, the evidence 
provides compelling support for finding that greenhouse gas air 
pollution endangers the public welfare of both current and

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future generations. The risk and the severity of adverse impacts on 
public welfare are expected to increase over time.
    The Administrator also finds that emissions of well-mixed 
greenhouse gases from the transportation sources covered under CAA 
section 202(a) \3\ contribute to the total greenhouse gas air 
pollution, and thus to the climate change problem, which is reasonably 
anticipated to endanger public health and welfare. The Administrator is 
defining the air pollutant that contributes to climate change as the 
aggregate group of the well-mixed greenhouse gases. The definition of 
air pollutant used by the Administrator is based on the similar 
attributes of these substances. These attributes include the fact that 
they are sufficiently long-lived to be well mixed globally in the 
atmosphere, that they are directly emitted, and that they exert a 
climate warming effect by trapping outgoing, infrared heat that would 
otherwise escape to space, and that they are the focus of climate 
change science and policy.
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    \3\ Section 202(a) source categories include passenger cars, 
heavy-, medium and light-duty trucks, motorcycles, and buses.
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    In order to determine if emissions of the well-mixed greenhouse 
gases from CAA section 202(a) source categories contribute to the air 
pollution that endangers public health and welfare, the Administrator 
compared the emissions from these CAA section 202(a) source categories 
to total global and total U.S. greenhouse gas emissions, finding that 
these source categories are responsible for about 4 percent of total 
global well-mixed greenhouse gas emissions and just over 23 percent of 
total U.S. well-mixed greenhouse gas emissions. The Administrator found 
that these comparisons, independently and together, clearly establish 
that these emissions contribute to greenhouse gas concentrations. For 
example, the emissions of well-mixed greenhouse gases from CAA section 
202(a) sources are larger in magnitude than the total well-mixed 
greenhouse gas emissions from every other individual nation with the 
exception of China, Russia, and India, and are the second largest 
emitter within the United States behind the electricity generating 
sector. As the Supreme Court noted, ``[j]udged by any standard, U.S. 
motor-vehicle emissions make a meaningful contribution to greenhouse 
gas concentrations and hence, * * * to global warming.'' Massachusetts 
v. EPA, 549 U.S. 497, 525 (2007).
    The Administrator's findings are in response to the Supreme Court's 
decision in Massachusetts v. EPA. That case involved a 1999 petition 
submitted by the International Center for Technology Assessment and 18 
other environmental and renewable energy industry organizations 
requesting that EPA issue standards under CAA section 202(a) for the 
emissions of carbon dioxide, methane, nitrous oxide, and 
hydrofluorocarbons from new motor vehicles and engines. The 
Administrator's findings are in response to this petition and are for 
purposes of CAA section 202(a).

B. Background Information Helpful To Understand These Findings

    This section provides some basic information regarding greenhouse 
gases and the CAA section 202(a) source categories, as well as the 
ongoing joint-rulemaking on greenhouse gases by EPA and the Department 
of Transportation. Additional technical and legal background, including 
a summary of the Supreme Court's Massachusetts v. EPA decision, can be 
found in the Proposed Endangerment and Contribution Findings (74 FR 
18886, April 24, 2009).
1. Greenhouse Gases and Transportation Sources Under CAA Section 202(a)
    Greenhouse gases are naturally present in the atmosphere and are 
also emitted by human activities. Greenhouse gases trap the Earth's 
heat that would otherwise escape from the atmosphere, and thus form the 
greenhouse effect that helps keep the Earth warm enough for life. Human 
activities are intensifying the naturally-occurring greenhouse effect 
by adding greenhouse gases to the atmosphere. The primary greenhouse 
gases of concern that are directly emitted by human activities include 
carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, 
perfluorocarbons, and sulfur hexafluoride. Other pollutants (such as 
aerosols) and other human activities, such as land use changes that 
alter the reflectivity of the Earth's surface, also cause climatic 
warming and cooling effects. In these Findings, the term ``climate 
change'' generally refers to the global warming effect plus other 
associated changes (e.g., precipitation effects, sea level rise, 
changes in the frequency and severity of extreme weather events) being 
induced by human activities, including activities that emit greenhouse 
gases. Natural causes also, contribute to climate change and climatic 
changes have occurred throughout the Earth's history. The concern now, 
however, is that the changes taking place in our atmosphere as a result 
of the well-documented buildup of greenhouse gases due to human 
activities are changing the climate at a pace and in a way that 
threatens human health, society, and the natural environment. Further 
detail on the state of climate change science can be found in Section 
III of these Findings as well as the technical support document (TSD) 
that accompanies this action (www.epa.gov/climatechange/endangerment.html).
    The transportation sector is a major source of greenhouse gas 
emissions both in the United States and in the rest of the world. The 
transportation sources covered under CAA section 202(a)--the section of 
the CAA under which these Findings occur--include passenger cars, 
light- and heavy-duty trucks, buses, and motorcycles. These 
transportation sources emit four key greenhouse gases: carbon dioxide, 
methane, nitrous oxide, and hydrofluorocarbons. Together, these 
transportation sources are responsible for 23 percent of total annual 
U.S. greenhouse gas emissions, making this source the second largest in 
the United States behind electricity generation.\4\
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    \4\ The units for greenhouse gas emissions in these findings are 
provided in carbon dioxide equivalent units, where carbon dioxide is 
the reference gas and every other greenhouse gas is converted to its 
carbon dioxide equivalent by using the 100-year global warming 
potential (as estimated by the Intergovernmental Panel on Climate 
Change (IPCC). assigned to each gas. The reference gas used is 
CO2, and therefore Global Warming Potential (GWP)-
weighted emissions are measured in teragrams of CO2 
equivalent (Tg CO2 eq.). In accordance with UNFCCC 
reporting procedures, the United States quantifies greenhouse gas 
emissions using the 100-year time frame values for GWPs established 
in the IPCC Second Assessment Report.
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    Further discussion of the emissions data supporting the 
Administrator's cause or contribute finding can be found in Section V 
of these Findings, and the detailed greenhouse gas emissions data for 
section 202(a) source categories can be found in Appendix B of EPA's 
TSD.
2. Joint EPA and Department of Transportation Proposed Greenhouse Gas 
Rule
    On September 15, 2009, EPA and the Department of Transportation's 
National Highway Safety Administration (NHTSA) proposed a National 
Program that would dramatically reduce greenhouse gas emissions and 
improve fuel economy for new cars and trucks sold in the United States. 
The combined EPA and NHTSA standards that make up this proposed 
National Program would apply to passenger cars, light-duty trucks, and 
medium-duty passenger vehicles, covering model years 2012 through 2016. 
They proposed to require these vehicles to meet an estimated combined 
average

[[Page 66500]]

emissions level of 250 grams of carbon dioxide per mile, equivalent to 
35.5 miles per gallon (MPG) if the automobile industry were to meet 
this carbon dioxide level solely through fuel economy improvements. 
Together, these proposed standards would cut carbon dioxide emissions 
by an estimated 950 million metric tons and 1.8 billion barrels of oil 
over the lifetime of the vehicles sold under the program (model years 
2012-2016). The proposed rulemaking can be viewed at (74 FR 49454, 
September 28, 2009).

C. Public Involvement

    In response to the Supreme Court's decision, EPA has been examining 
the scientific and technical basis for the endangerment and cause or 
contribute decisions under CAA section 202(a) since 2007. The science 
informing the decision-making process has grown stronger since our work 
began. EPA's approach to evaluating the science, including comments 
submitted during the public comment period, is further discussed in 
Section III.A of these Findings. Public review and comment has always 
been a major component of EPA's process.
1. EPA's Initial Work on Endangerment
    As part of the Advance Notice of Proposed Rulemaking: Regulating 
Greenhouse Gas Emissions under the Clean Air Act (73 FR 44353) 
published in July 2008, EPA provided a thorough discussion of the 
issues and options pertaining to endangerment and cause or contribute 
findings under the CAA. The Agency also issued a TSD providing an 
overview of all the major scientific assessments available at the time 
and emission inventory data relevant to the contribution finding 
(Docket ID No. EPA-HQ-OAR-2008-0318). The comment period for that 
Advance Notice was 120 days, and it provided an opportunity for EPA to 
hear from the public with regard to the issues involved in endangerment 
and cause or contribute findings as well as the supporting science. EPA 
received, reviewed and considered numerous comments at that time and 
this public input was reflected in the Findings that the Administrator 
proposed in April 2009. In addition, many comments were received on the 
TSD released with the Advance Notice and reflected in revisions to the 
TSD released in April 2009 to accompany the Administrator's proposal. 
All public comments on the Advance Notice are contained in the public 
docket for this action (Docket ID No. EPA-HQ-OAR-2008-0318) accessible 
through www.regulations.gov.
2. Public Involvement Since the April 2009 Proposed Endangerment 
Finding
    The Proposed Endangerment and Cause or Contribute Findings for 
Greenhouse Gases (Proposed Findings) was published on April 24, 2009 
(74 FR 18886). The Administrator's proposal was subject to a 60-day 
public comment period, which ended June 23, 2009, and also included two 
public hearings. Over 380,000 public comments were received on the 
Administrator's proposed endangerment and cause or contribute findings, 
including comments on the elements of the Administrator's April 2009 
proposal, the legal issues pertaining to the Administrator's decisions, 
and the underlying TSD containing the scientific and technical 
information.
    A majority of the comments (approximately 370,000) were the result 
of mass mail campaigns, which are defined as groups of comments that 
are identical or very similar in form and content. Overall, about two-
thirds of the mass-mail comments received are supportive of the 
Findings and generally encouraged the Administrator both to make a 
positive endangerment determination and implement greenhouse gas 
emission regulations. Of the mass mail campaigns in disagreement with 
the Proposed Findings most either oppose the proposal on economic 
grounds (e.g., due to concern for regulatory measures following an 
endangerment finding) or take issue with the proposed finding that 
atmospheric greenhouse gas concentrations endanger public health and 
welfare. Please note that for mass mailer campaigns, a representative 
copy of the comment is posted in the public docket for this Action 
(Docket ID No. EPA-HQ-OAR-2009-0171) at www.regulations.gov.
    Approximately 11,000 other public comments were received. These 
comments raised a variety of issues related to the scientific and 
technical information EPA relied upon in making the Proposed Findings, 
legal and procedural issues, the content of the Proposed Findings, and 
the implications of the Proposed Findings.
    In light of the very large number of comments received and the 
significant overlap between many comments, EPA has not responded to 
each comment individually. Rather, EPA has summarized and provided 
responses to each significant argument, assertion and question 
contained within the totality of the comments. EPA's responses to some 
of the most significant comments are provided in these Findings. 
Responses to all significant issues raised by the comments are 
contained in the 11 volumes of the Response to Comments document, 
organized by subject area (found in docket EPA-HQ-OAR-2009-0171).
3. Issues Raised Regarding the Rulemaking Process
    EPA received numerous comments on process-related issues, including 
comments urging the Administrator to delay issuing the final findings, 
arguing that it was improper for the Administrator to sever the 
endangerment and cause or contribute findings from the attendant 
section 202(a) standards, arguing the final decision was preordained by 
the President's May vehicle announcement, and questioning the adequacy 
of the comment period. Summaries of key comments and EPA's responses 
are discussed in this section. Additional and more detailed responses 
can be found in the Response to Comments document, Volume 11. As noted 
in the Response to Comments document, EPA also received comments 
supporting the overall process.
a. It Is Reasonable for the Administrator To Issue the Endangerment and 
Cause or Contribute Findings Now
    Though the Supreme Court did not establish a specific deadline for 
EPA to act, more than two and a half years have passed since the remand 
from the Supreme Court, and it has been 10 years since EPA received the 
original petition requesting that EPA regulate greenhouse gas emissions 
from new motor vehicles. EPA has a responsibility to respond to the 
Supreme Court's decision and to fulfill its obligations under current 
law, and there is good reason to act now given the urgency of the 
threat of climate change and the compelling scientific evidence.
    Many commenters urge EPA to delay making final findings for a 
variety of reasons. They note that the Supreme Court did not establish 
a deadline for EPA to act on remand. Commenters also argue that the 
Supreme Court's decision does not require that EPA make a final 
endangerment finding, and thus that EPA has discretionary power and may 
decline to issue an endangerment finding, not only if the science is 
too uncertain, but also if EPA can provide ``some reasonable 
explanation'' for exercising its discretion. These commenters interpret 
the Supreme Court decision not as rejecting all policy reasons for 
declining to undertake an endangerment finding, but rather as 
dismissing solely the policy reasons EPA set forth in 2003. Some 
commenters cite language in the

[[Page 66501]]

Supreme Court decision regarding EPA's discretion regarding ``the 
manner, timing, content, and coordination of its regulations,'' and the 
Court's declining to rule on ``whether policy concerns can inform 
EPA\'\s actions in the event that it makes'' a CAA section 202(a) 
finding to support their position.
    Commenters then suggest a variety of policy reasons that EPA can 
and should make to support a decision not to undertake a finding of 
endangerment under CAA section 202(a)(1). For example, they argue that 
a finding of endangerment would trigger several other regulatory 
programs--such as the Prevention of Significant Deterioration (PSD) 
provisions--that would impose an unreasonable burden on the economy and 
government, without providing a benefit to the environment. Some 
commenters contend that EPA should defer issuing a final endangerment 
finding while Congress considers legislation. Many commenters note the 
ongoing international discussions regarding climate change and state 
their belief that unilateral EPA action would interfere with those 
negotiations. Others suggest deferring the EPA portion of the joint 
U.S. Department of Transportation (DOT)/EPA rulemaking because they 
argue that the new Corporate Average Fuel Economy (CAFE) standards will 
effectively result in lower greenhouse gas emissions from new motor 
vehicles, while avoiding the inevitable problems and concerns of 
regulating greenhouse gases under the CAA.
    Other commenters argue that the endangerment determination has to 
be made on the basis of scientific considerations only. These 
commenters state that the Court was clear that ``[t]he statutory 
question is whether sufficient information exists to make an 
endangerment finding,'' and thus, only if ``the scientific uncertainty 
is so profound that it precludes EPA from making a reasoned judgment as 
to whether greenhouse gases contribute to global warming,'' may EPA 
avoid making a positive or negative endangerment finding. Many 
commenters urge EPA to take action quickly. They note that it has been 
10 years since the original petition requesting that EPA regulate 
greenhouse gas emissions from motor vehicles was submitted to EPA. They 
argue that climate change is a serious problem that requires immediate 
action.
    EPA agrees with the commenters who argue that the Supreme Court 
decision held that EPA is limited to consideration of science when 
undertaking an endangerment finding, and that we cannot delay issuing a 
finding due to policy concerns if the science is sufficiently certain 
(as it is here). The Supreme Court stated that ``EPA can avoid taking 
further action only if it determines that greenhouse gases do not 
contribute to climate change or if it provides some reasonable 
explanation as to why it cannot or will not exercise its discretion to 
determine whether they do'' 549 U.S. at 533. Some commenters point to 
this last provision, arguing that the policy reasons they provide are a 
``reasonable explanation'' for not moving forward at this time. 
However, this ignores other language in the decision that clearly 
indicates that the Court interprets the statute to allow for the 
consideration only of science. For example, in rejecting the policy 
concerns expressed by EPA in its 2003 denial of the rulemaking 
petition, the Court noted that ``it is evident [the policy 
considerations] have nothing to do with whether greenhouse gas 
emissions contribute to climate change. Still less do they amount to a 
reasoned justification for declining to form a scientific judgment'' 
Id. at 533-34 (emphasis added).
    Moreover, the Court also held that ``[t]he statutory question is 
whether sufficient information exists to make an endangerment finding'' 
Id. at 534. Taken as a whole, the Supreme Court's decision clearly 
indicates that policy reasons do not justify the Administrator avoiding 
taking further action on the question here.
    We also note that the language many commenters quoted from the 
Supreme Court decision about EPA's discretion regarding the manner, 
timing and content of Agency actions, and the ability to consider 
policy concerns, relate to the motor vehicle standards required in the 
event that EPA makes a positive endangerment finding, and not the 
finding itself. EPA has long taken the position that it does have such 
discretion in the standard-setting step under CAA section 202(a).
b. The Administrator Reasonably Proceeded With the Endangerment and 
Cause or Contribute Findings Separate From the CAA Section 202(a) 
Standard Rulemaking
    As discussed in the Proposed Findings, typically endangerment and 
cause or contribute findings have been proposed concurrently with 
proposed standards under various sections of the CAA, including CAA 
section 202(a). EPA received numerous comments on its decision to 
propose the endangerment and cause or contribute findings separate from 
any standards under CAA section 202(a).
    Commenters argue that EPA has no authority to issue an endangerment 
determination under CAA section 202(a) separate and apart from the 
rulemaking to establish emissions standards under CAA section 202(a). 
According to these commenters, CAA section 202(a) provides only one 
reason to issue an endangerment determination, and that is as the basis 
for promulgating emissions standards for new motor vehicles; thus, it 
does not authorize such a stand-alone endangerment finding, and EPA may 
not create its own procedural rules completely divorced from the 
statutory text. They continue by stating that while CAA section 202(a) 
says EPA may issue emissions standards conditioned on such a finding, 
it does not say EPA may first issue an endangerment determination and 
then issue emissions standards. In addition, they contend, the 
endangerment proposal and the emissions standards proposal need to be 
issued together so commenters can fully understand the implications of 
the endangerment determination. Failure to do so, they argue, deprives 
the commenters of the opportunity to assess the regulations that will 
presumably follow from an endangerment finding. They also argue that 
the expected overlap between reductions in emissions of greenhouse 
gases from CAA section 202(a) standards issued by EPA and CAFE 
standards issued by DOT calls into question the basis for the CAA 
section 202(a) standards and the related endangerment finding, and that 
EPA is improperly motivated by an attempt to trigger a cascade of 
regulations under the CAA and/or to promote legislation by Congress.
    EPA disagrees with the commenters' claims and arguments. The text 
of CAA section 202(a) is silent on this issue. It does not specify the 
timing of an endangerment finding, other than to be clear that 
emissions standards may not be issued unless such a determination has 
been made. EPA is exercising the procedural discretion that is provided 
by CAA section 202(a)'s lack of specific direction. The text of CAA 
section 202(a) envisions two separate actions by the Administrator: (1) 
A determination on whether emissions from classes or categories of new 
motor vehicles cause or contribute to air pollution that may reasonably 
be anticipated to endanger, and (2) a separate decision on issuance of 
appropriate emissions standards for such classes or categories. The 
procedure followed in this rulemaking, and the companion rulemaking 
involving emissions standards for light duty motor vehicles, is 
consistent with CAA section 202(a). EPA will issue final emissions 
standards for new motor

[[Page 66502]]

vehicles only if affirmative findings are made concerning contribution 
and endangerment, and such emissions standards will not be finalized 
prior to making any such determinations. While it would also be 
consistent with CAA section 202(a) to issue the greenhouse gas 
endangerment and contribution findings and emissions standards for new 
light-duty vehicles in the same rulemaking, e.g., a single proposal 
covering them and a single final rule covering them, nothing in CAA 
section 202(a) requires such a procedural approach, and nothing in the 
approach taken in this case violates the text of CAA section 202(a). 
Since Congress was silent on this issue, and more than one procedural 
approach may accomplish the requirements of CAA section 202(a), EPA has 
the discretion to use the approach considered appropriate in this case. 
Once the final affirmative contribution and endangerment findings are 
made, EPA has the authority to issue the final emissions standards for 
new light-duty motor vehicles; however, as the Supreme Court has noted, 
the agency has `significant latitude as to the manner, timing, [and] 
content * * * of its regulations . * * *' Massachusetts v. EPA, 549 
U.S. at 533. That includes the discretion to issue them in a separate 
rulemaking.
    Commenters' argument would also lead to the conclusion that EPA 
could not make an endangerment finding for the entire category of new 
motor vehicles, as it is doing here, unless EPA also conducted a 
rulemaking that set emissions standards for all the classes and 
categories of new motor vehicles at the same time. This narrow 
procedural limitation would improperly remove discretion that CAA 
section 202(a) provides to EPA.
    EPA has the discretion under CAA section 202(a) to consider classes 
or categories of new motor vehicles separately or together in making a 
contribution and endangerment determination. This discretion would be 
removed under commenters' interpretation, by limiting this to only 
those cases in which EPA was also ready to issue emissions standards 
for all of the classes or categories covered by the endangerment 
finding. However, nothing in the text of CAA section 202(a) places such 
a limit on EPA's discretion in determining how to group classes or 
categories of new motor vehicles for purposes of the contribution and 
endangerment findings. This limitation would not be appropriate, 
because the issues of contribution and endangerment are separate and 
distinct from the issues of setting emissions standards. EPA, in this 
case, is fully prepared to go forward with the contribution and 
endangerment determination, while it is not ready to proceed with 
rulemaking for each and every category of new motor vehicles in the 
first rulemaking to set emissions standards. Section 202(a) of the CAA 
provides EPA discretion with regard to when and how it conducts its 
rulemakings to make contribution and endangerment findings, and to set 
emissions standards, and the text of CAA section 202(a) does not 
support commenters attempt to limit such discretion.
    Concerns have been raised that the failure to issue the proposed 
endangerment finding and the proposed emissions standard together 
preclude commenters from assessing and considering the implications of 
the endangerment finding and the regulations that would likely flow 
from such a finding. However, commenters have failed to explain how 
this interferes in any way with their ability to comment on the 
endangerment finding. In fact it does not interfere, because the two 
proposals address separate and distinct issues. The endangerment 
finding concerns the contribution of new motor vehicles to air 
pollution and the effect of that air pollution on public health or 
welfare. The emissions standards, which have been proposed (74 FR 
49454, September 28, 2009), concern the appropriate regulatory 
emissions standards if affirmative findings are made on contribution 
and endangerment. These two proposals address different issues. While 
commenters have the opportunity to comment on the proposed emissions 
standards in that rulemaking, they have not shown, and cannot show, 
that they need to have the emissions standards proposal before them in 
order to provide relevant comments on the proposed contribution or 
endangerment findings. Further discussion of this issue can be found in 
Section II of these Findings, and discussion of the timing of this 
action and its relationship to other CAA provisions and Congressional 
action can be found in Section III of these Findings and Volume 11 of 
the Response to Comments document.
c. The Administrator's Final Decision Was Not Preordained by the 
President's May Vehicle Announcement
    EPA received numerous comments arguing that the President's 
announcement of a new ``National Fuel Efficiency Policy'' on May 19, 
2009 seriously undermines EPA's ability to provide objective 
consideration of and a legally adequate response to comments objecting 
to the previously proposed endangerment findings.
    Commenters' conclusion is based on the view that the President's 
announced policy requires EPA to promulgate greenhouse gas emissions 
standards under CAA section 202(a), that the President's and 
Administrator Jackson's announcement indicated that the endangerment 
rulemaking was but a formality and that a final endangerment finding 
was a fait accompli. Commenters argue that this means the result of 
this rulemaking has been preordained and the merits of the issues have 
been prejudged.
    EPA disagrees. Commenters' arguments wholly exaggerate and 
mischaracterize the circumstances. In the April 24, 2009 endangerment 
proposal EPA was clear that the two steps in the endangerment provision 
have to be satisfied in order for EPA to issue emissions standards for 
new motor vehicles under CAA section 202(a) (74 FR at 18888, April 24, 
2009). This was repeated when EPA issued the Notice of Upcoming Joint 
Rulemaking to Establish Vehicle GHG Emissions and CAFE Standards (74 FR 
24007 May 22, 2009) (Notice of Intent or NOI). This was repeated again 
when EPA issued proposed greenhouse gas emissions standards for certain 
new motor vehicles (74 FR 49454, September 28, 2009). EPA has 
consistently made it clear that issuance of new motor vehicle standards 
requires and is contingent upon satisfaction of the two-part 
endangerment test.
    On May 19, 2009 EPA issued the joint Notice of Intent, which 
indicated EPA's intention to propose new motor vehicle standards. All 
of the major motor vehicle manufacturers, their trade associations, the 
State of California, and several environmental organizations announced 
their full support for the upcoming rulemaking. Not surprisingly, on 
the same day the President also announced his full support for this 
action. Commenters, however, erroneously equate this Presidential 
support with a Presidential directive that requires EPA to prejudge and 
preordain the result of this rulemaking.
    The only evidence they point to are simply indications of 
Presidential support. Commenters point to a press release, which 
unsurprisingly refers to the Agency's announcement as delivering on the 
President's commitment to enact more stringent fuel economy standards, 
by bringing ``all stakeholders to the table and [coming] up with a 
plan'' for solving a serious problem. The plan that was announced, of 
course, was a plan to conduct notice and comment

[[Page 66503]]

rulemaking. The press release itself states that President Obama ``set 
in motion a new national policy,'' with the policy ``aimed'' at 
reducing greenhouse gas emissions for new cars and trucks. What was 
``set in motion'' was a notice and comment rulemaking described in the 
NOI issued by EPA on the same day. Neither the President nor EPA 
announced a final rule or a final direction that day, but instead did 
no more than announce a plan to go forward with a notice and comment 
rulemaking. That is how the plan ``delivers on the President's 
commitment'' to enact more stringent standards. The announcement was 
that a notice and comment rulemaking would be initiated with the aim of 
adopting certain emissions standards.
    That is no different from what EPA or any other agency states when 
it issues a notice of proposed rulemaking. It starts a process that has 
the aim of issuing final regulations if they are deemed appropriate at 
the end of the public process. The fact that an Agency proposes a 
certain result, and expects that a final rule will be the result of 
setting such a process in motion, is the ordinary course of affairs in 
notice and comment rulemakings. This does not translate into prejudging 
the final result or having a preordained result that de facto negates 
the public comment process. The President's press release of May 19, 
2009 was a recognition that this notice and comment rulemaking process 
would be set in motion, as well as providing his full support for the 
Agency to go forward in this direction; it was no more than that.
    The various stakeholders who announced their support for the plan 
that had been set in motion all recognized that full notice and comment 
rulemaking was part of the plan, and they all reserved their rights to 
participate in such notice and comment rulemaking. For example, see the 
letter of support from Ford Motor Company, which states that ``Ford 
fully supports proposal and adoption of such a National Program, which 
we understand will be subject to full notice-and-comment rulemaking, 
affording all interested parties including Ford the right to 
participate fully, comment, and submit information, the results of 
which are not pre-determined but depend upon processes set by law.''
d. The Notice and Comment Period Was Adequate
    Many commenters argue that the 60-day comment period was 
inadequate. Commenters claim that a 60-day period was insufficient time 
to fully evaluate the science and other information that informed the 
Administrator's proposal. Some commenters assert that because the 
comment period for the Proposed Finding substantially overlapped with 
the comment period for the Mandatory Greenhouse Gas Reporting Rule, as 
well as Congress' consideration of climate legislation, their ability 
to fully participate in the notice and comment period was ``seriously 
compromised.'' Moreover, they continue, because EPA had not yet 
proposed CAA section 202(a) standards, there was no valid reason to 
fail to extend the comment period. Several commenters and other 
entities had also requested that EPA extend the comment period.
    Some commenters assert that the notice provided by this rulemaking 
was ``defective'' because the Federal Register notice announcing the 
proposal had an error in the e-mail address for the docket. At least 
one commenter suggests that this error deprives potential commenters of 
their Due Process under the Fifth Amendment of the Constitution, citing 
Armstrong v. Manzo, 380 U.S. 545, 552 (1965), and that failure to 
``correct'' the minor typographical error in the e-mail address and 
extend the comment period would make the rule ``subject to reversal'' 
in violation of the CAA, Administrative Procedure Act (APA), the Due 
Process clause of the Constitution, and EO 12866.
    Finally, for many of the same reasons that commenters argue a 60-
day comment period was inadequate, several commenters request that EPA 
reopen and/or extend the comment period. One commenter requests that 
the comment period be reopened because there was new information 
regarding data used by EPA in the Proposed Findings. In particular, the 
commenter alleges that it recently became aware that one of the sources 
of global climate data had destroyed the raw data for its data set of 
global surface temperatures. The commenter argues that this alleged 
destruction of raw data violates scientific standards, calls into 
question EPA's reliance on that data in these Findings, and 
necessitates a reopening of the proceedings. Other commenters request 
that the comment period be extended and/or reopened due to the release 
of a Federal government document on the impact of climate change in the 
United States near the end of the comment period, as well as the 
release of an internal EPA staff document discussing the science.
    The official public comment period on the proposed rule was 
adequate. First, a 60-day comment period satisfies the procedural 
requirements of CAA section 307 of the CAA, which requires a 30-day 
comment period, and that the docket be kept open to receive rebuttal or 
supplemental information as follow-up to any hearings for 30 days 
following the hearings. EPA met those obligations here--the comment 
period opened on April 24, 2009, the last hearing was on May 21, 2009 
and the comment period closed June 23, 2009.
    Second, as explained in letters denying requests to extend the 
comment period, a very large part of the information and analyses for 
the Proposed Findings had been previously released in July 30, 2008, as 
part of the Advance Notice of Proposed Rulemaking: Regulating 
Greenhouse Gas Emissions under the Clean Air Act (ANPR) (73 FR 44353). 
The public comment period for the ANPR is discussed above in Section 
I.C.1 of these Findings. The Administrator explained that the comment 
period for that ANPR was 120 days and that the major recent scientific 
assessments that EPA relied upon in the TSD released with the ANPR had 
previously each gone through their own public review processes and have 
been publicly available for some time. In other words, EPA has provided 
ample time for review, particularly with regard to the technical 
support for the Findings. See, for example, EPA Letter to Congressman 
Issa dated June 17, 2009, a copy of which is available at http://epa.gov/climatechange/endangerment.html.
    Moreover, the comment period was not rendered insufficient merely 
because other climate-related proceedings were occurring 
simultaneously.
    While one commenter suggests that the convergence of several 
different climate-related activities has ``seriously compromised'' 
their ability to participate in the comment process, that commenter was 
able to submit an 89 page comment on this proposal alone. Moreover, it 
is hardly rare that more than one rule is out for comment at the same 
time. As noted above, EPA has received a substantial number of 
significant comments on the Proposed Findings, and has thoroughly 
considered and responded to significant comments.
    EPA finds no evidence that a typographical error in the docket e-
mail address of the Federal Register notice announcing the proposal 
prevented the public from having a meaningful opportunity to comment, 
and therefore deprived them of due process. Although the minor error--
which involved a word processing auto-correction that turned a short 
dash into a long dash--appeared in the FR version of the Proposed 
Findings, the e-mail address is correct

[[Page 66504]]

in the signature version of the Proposed Findings posted on EPA's Web 
site until publication in the Federal Register, and in the 
``Instructions for Submitting Written Comments'' document on the Web 
site for the rulemaking. EPA has received over 190,000 e-mails to the 
docket e-mail address to date, so the minor typographical error 
appearing in only one location has not been an impediment to interested 
parties' e-mailing comments. Moreover, EPA provided many other avenues 
for interested parties to submit comments in addition to the docket e-
mail address, including via www.regulations.gov, mail, and fax; each of 
these options have been utilized by many commenters. EPA is confident 
that the minor typographical error did not prevent anyone from 
submitting written comments, by e-mail or otherwise, and that the 
public was provided ``meaningful participation in the regulatory 
process'' as mentioned in EO 12866.
    Our response regarding the request to reopen the comment period due 
to concerns about alleged destruction of raw global surface data is 
discussed more fully in the Response to Comments document, Volume 11. 
The commenter did not provide any compelling reason to conclude that 
the absence of these data would materially affect the trends in the 
temperature records or conclusions drawn about them in the assessment 
literature and reflected in the TSD. The Hadley Centre/Climate Research 
Unit (CRU) temperature record (referred to as HadCRUT) is just one of 
three global surface temperature records that EPA and the assessment 
literature refer to and cite. National Oceanic and Atmospheric 
Administration (NOAA) and National Aeronautics and Space Administration 
(NASA) also produce temperature records, and all three temperature 
records have been extensively peer reviewed. Analyses of the three 
global temperature records produce essentially the same long-term 
trends as noted in the Climate Change Science Program (CCSP) (2006) 
report ``Temperature Trends in the Lower Atmosphere,'' IPCC (2007), and 
NOAA's study \5\ ``State of the Climate in 2008''. Furthermore, the 
commenter did not demonstrate that the allegedly destroyed data would 
materially alter the HadCRUT record or meaningfully hinder its 
replication. The raw data, a small part of which has not been public 
(for reasons described at: https://www.uea.ac.uk/mac/comm/media/press/2009/nov/CRUupdate), are available in a quality-controlled (or 
homogenized, value-added) format and the methodology for developing the 
quality-controlled data is described in the peer reviewed literature 
(as documented at http://www.cru.uea.ac.uk/cru/data/temperature/).
---------------------------------------------------------------------------

    \5\ Peterson, T.C., and M.O. Baringer (Eds.) (2009) State of the 
Climate in 2008. Bull. Amer. Meteor. Soc., 90, S1-S196.
---------------------------------------------------------------------------

    The release of the U.S. Global Climate Research Program (USGCRP) 
report on impacts of climate change in the United States in June 2009 
also did not necessitate extending the comment period. This report was 
issued by the USGCRP, formerly the Climate Change Science Program 
(CCSP), and synthesized information contained in prior CCSP reports and 
other synthesis reports, many of which had already been published (and 
were included in the TSD for the Proposed Findings). Further, the 
USGCRP report itself underwent notice and comment before it was 
finalized and released.
    Regarding the internal EPA staff paper that came to light during 
the comment period, several commenters submitted a copy of the EPA 
staff paper with their comments; EPA's response to the issues raised by 
the staff paper are discussed in the Response to Comments document, 
Volume 1. The fact that some internal agency deliberations were made 
public during the comment period does not in and of itself call into 
question those deliberations. As our responses to comments explain, EPA 
considered the concerns noted in the staff paper during the proposal 
stage, as well as when finalizing the Findings. There was nothing about 
those internal comments that required an extension or reopening of the 
comment period.
    Thus, the opportunity for comment fully satisfies the CAA and 
Constitutional requirement of Due Process. Cases cited by commenters do 
not indicate otherwise. The comment period and thorough response to 
comment documents in the docket indicate that EPA has given people an 
opportunity to be heard in a ``meaningful time and a meaningful 
matter.'' Armstrong v. Manzo, 380 U.S. 545, 552 (1965). Interested 
parties had full notice of the rulemaking proceedings and a significant 
opportunity to participate through the comment process and multiple 
hearings.
    For all the above reasons, EPA's denial of the requests for 
extension or reopening of the comment period was entirely reasonable in 
light of the extensive opportunity for public comment and heavy amount 
of public participation during the comment period. EPA has fully 
complied with all applicable public participation requirements for this 
rulemaking.
e. These Findings Did Not Necessitate a Formal Rulemaking Under the 
Administrative Procedure Act
    One commenter, with the support of others, requests that EPA 
undertake a formal rulemaking process for the Findings, on the record, 
in accordance with the procedures described in sections 556-557 of the 
Administrative Procedure Act (APA). The commenter requests a multi-step 
process, involving additional public notice, an on-the-record 
proceeding (e.g., formal administrative hearing) with the right of 
appeal, utilization of the Clean Air Scientific Advisory Committee 
(CASAC) and its advisory proceedings, and designation of 
representatives from other executive branch agencies to participate in 
the formal proceeding and any CASAC advisory proceeding.
    The commenter asserts that while EPA is not obligated under the CAA 
to undertake these additional procedures, the Agency nonetheless has 
the legal authority to engage in such a proceeding. The commenter 
believes this proceeding would show that EPA is ``truly committed to 
scientific integrity and transparency.'' The commenter cites several 
cases to argue that refusal to proceed on the record would be 
``arbitrary and capricious'' or would be an ``abuse of discretion.'' 
The allegation at the core of the commenter's argument is that profound 
and wide-ranging scientific uncertainties exist in the Proposed 
Findings and in the impacts on health and welfare discussed in the TSD. 
To support this argument, the commenter provides lengthy criticisms of 
the science. The commenter also argues that the regulatory cascade that 
would be ``unleashed'' by a positive endangerment finding warrants the 
more formal proceedings.
    Finally, the commenter suggests that EPA engage in ``formal 
rulemaking'' procedures in part due to the Administrative Conference of 
the United States' (ACUS) recommended factors for engaging in formal 
rulemaking. The commenter argues that the current action is 
``complex,'' ``open-ended,'' and the costs that errors in the action 
may pose are ``significant.''
    EPA is denying the request to undertake an ``on the record'' formal 
rulemaking. EPA is under no obligation to follow the extraordinarily 
rarely used formal rulemaking provisions of the APA. First, CAA section 
307(d) of the CAA clearly states that the rulemaking provisions of CAA 
section 307(d), not APA sections 553 through 557, apply to certain 
specified actions, such as this

[[Page 66505]]

one. EPA has satisfied all the requirements of CAA section 307(d). 
Indeed, the commenter itself ``is not asserting that the Clean Air Act 
expressly requires'' the additional procedures it requests. Moreover, 
the commenter does not discuss how the suggested formal proceeding 
would fit into the informal rulemaking requirements of CAA section 
307(d) that do apply.
    Formal rulemaking is very rarely used by Federal agencies. The 
formal rulemaking provisions of the APA are only triggered when the 
statute explicitly calls for proceedings ``on the record after 
opportunity for an agency hearing.'' United States v. Florida East 
Coast Ry. Co., 410 U.S. 224, 241 (1973). The mere mention of the word 
``hearing'' does not trigger the formal rulemaking provisions of the 
APA. Id. The CAA does not include the statutory phrase required to 
trigger the formal rulemaking provisions of the APA (and as noted above 
the APA does not apply in the first place). Congress specified that 
certain rulemakings under the CAA follow the rulemaking procedures 
outlined in CAA section 307(d) rather than the APA ``formal 
rulemaking'' commenter suggests.
    Despite the inapplicability of the formal rulemaking provisions to 
this action, commenters suggest that to refuse to voluntarily undertake 
rulemaking provisions not preferred by Congress would make EPA's 
rulemaking action an ``abuse of discretion.'' EPA disagrees with this 
claim, and cases cited by the commenter do not indicate otherwise. To 
support the idea that an agency decision to engage in informal 
rulemaking could be an abuse of discretion, commenter cites Ford Motor 
Co. v. FTC, 673 F.2d 1008 (9th Cir. 1981). In Ford Motor Co., the court 
ruled that the FTC's decision regarding an automobile dealership should 
have been resolved through a rulemaking rather than an individualized 
adjudication. Id. at 1010. In that instance, the court favored 
``rulemaking'' over adjudication--not ``formal rulemaking'' over the 
far more common ``informal rulemaking.'' The case stands only for the 
non-controversial proposition that sometimes agency use of 
adjudications may rise to an abuse of discretion where a rulemaking 
would be more appropriate--whether formal or informal. The Commenter 
does not cite a single judicial opinion stating that an agency abused 
its discretion by following the time-tested and Congressionally-favored 
informal rulemaking provisions of the CAA or the APA instead of the 
rarely used formal APA rulemaking provisions.
    The commenter also alludes to the possibility that the choice of 
informal rulemaking may be ``arbitrary and capricious. EPA disagrees 
that the choice to follow the frequently used, and CAA required, 
informal rulemaking procedures is arbitrary and capricious. The 
commenter cites Vermont Yankee Nuclear Power Corp. v. NRDC, 435 U.S. 
519 (1978) for the proposition that ``extremely compelling 
circumstances'' could lead to a court overturning agency action for 
declining to follow extraneous procedures. As the commenter notes, in 
Vermont Yankee the Supreme Court overturned a lower court decision for 
imposing additional requirements not required by applicable statutes. 
Even if the dicta in Vermont Yankee could be applied contrary to the 
holding of the case in the way the commenter suggests, EPA's decision 
to follow frequently used informal rulemaking procedures for this 
action is highly reasonable.
    As for the ACUS factors the commenter cites in support of its 
request, as the commenter notes, the ACUS factors are mere 
recommendations. While EPA certainly respects the views of ACUS, the 
recommendations are not binding on the Agency. In addition, EPA has 
engaged in a thorough, traditional rulemaking process that ensures that 
any concerns expressed by the commenter have been addressed. EPA has 
fully satisfied all applicable law in their consideration of this 
rulemaking.
    Finally, as explained in Section III of these Findings and the 
Response to Comments document, EPA's approach to evaluating the 
evidence before it was entirely reasonable, and did not require a 
formal hearing. EPA relied primarily on robust synthesis reports that 
have undergone peer review and comment. The Agency also carefully 
considered the comments received on the Proposed Findings and TSD, 
including review of attached studies and documents. The public has had 
ample opportunity to provide its views on the science, and the record 
supporting these final findings indicates that EPA carefully considered 
and responded to significant public comments. To the extent the 
commenter's concern is that a formal proceeding will help ensure the 
right action in response to climate change is taken, that is not an 
issue for these Findings. As discussed in Section III of these 
Findings, this science-based judgment is not the forum for considering 
the potential mitigation options or their impact.

II. Legal Framework for This Action

    As discussed in the Proposed Findings, two statutory provisions of 
the CAA govern the Administrator's Findings. Section 202(a) of the CAA 
sets forth a two-part test for regulatory action under that provision: 
Endangerment and cause or contribute. Section 302 of the CAA contains 
definitions of the terms ``air pollutant'' and ``effects on welfare''. 
Below is a brief discussion of these statutory provisions and how they 
govern the Administrator's decision, as well as a summary of 
significant legal comments and EPA's responses to them.

A. Section 202(a) of the CAA--Endangerment and Cause or Contribute

1. The Statutory Framework
    Section 202(a)(1) of the CAA states that:
    The Administrator shall by regulation prescribe (and from time to 
time revise) standards applicable to the emission of any air pollutant 
from any class or classes of new motor vehicles or new motor vehicle 
engines, which in [her] judgment cause, or contribute to, air pollution 
which may reasonably be anticipated to endanger public health or 
welfare.
    Based on the text of CAA section 202(a) and its legislative 
history, the Administrator interprets the two-part test as follows. 
Further discussion of this two-part test can be found in Section II of 
the preamble for the Proposed Findings. First, the Administrator is 
required to protect public health and welfare, but she is not asked to 
wait until harm has occurred. EPA must be ready to take regulatory 
action to prevent harm before it occurs. Section 202(a)(1) requires the 
Administrator to ``anticipate'' ``danger'' to public health or welfare. 
The Administrator is thus to consider both current and future risks. 
Second, the Administrator is to exercise judgment by weighing risks, 
assessing potential harms, and making reasonable projections of future 
trends and possibilities. It follows that when exercising her judgment 
the Administrator balances the likelihood and severity of effects. This 
balance involves a sliding scale; on one end the severity of the 
effects may be of great concern, but the likelihood low, while on the 
other end the severity may be less, but the likelihood high. Under 
either scenario, the Administrator is permitted to find endangerment. 
If the harm would be catastrophic, the Administrator is permitted to 
find endangerment even if the likelihood is small.
    Because scientific knowledge is constantly evolving, the 
Administrator may be called upon to make decisions while recognizing 
the uncertainties and

[[Page 66506]]

limitations of the data or information available, as risks to public 
health or welfare may involve the frontiers of scientific or medical 
knowledge. At the same time, the Administrator must exercise reasoned 
decision making, and avoid speculative inquiries. Third, as discussed 
further below, the Administrator is to consider the cumulative impact 
of sources of a pollutant in assessing the risks from air pollution, 
and is not to look only at the risks attributable to a single source or 
class of sources. Fourth, the Administrator is to consider the risks to 
all parts of our population, including those who are at greater risk 
for reasons such as increased susceptibility to adverse health effects. 
If vulnerable subpopulations are especially at risk, the Administrator 
is entitled to take that point into account in deciding the question of 
endangerment. Here too, both likelihood and severity of adverse effects 
are relevant, including catastrophic scenarios and their probabilities 
as well as the less severe effects. As explained below, vulnerable 
subpopulations face serious health risks as a result of climate change.
    In addition, by instructing the Administrator to consider whether 
emissions of an air pollutant cause or contribute to air pollution, the 
statute is clear that she need not find that emissions from any one 
sector or group of sources are the sole or even the major part of an 
air pollution problem. The use of the term ``contribute'' clearly 
indicates a lower threshold than the sole or major cause. Moreover, the 
statutory language in CAA section 202(a) does not contain a modifier on 
its use of the term contribute. Unlike other CAA provisions, it does 
not require ``significant'' contribution. See, e.g., CAA sections 
111(b); 213(a)(2), (4). To be sure, any finding of a ``contribution'' 
requires some threshold to be met; a truly trivial or de minimis 
``contribution'' might not count as such. The Administrator therefore 
has ample discretion in exercising her reasonable judgment in 
determining whether, under the circumstances presented, the cause or 
contribute criterion has been met. Congress made it clear that the 
Administrator is to exercise her judgment in determining contribution, 
and authorized regulatory controls to address air pollution even if the 
air pollution problem results from a wide variety of sources. While the 
endangerment test looks at the entire air pollution problem and the 
risks it poses, the cause or contribute test is designed to authorize 
EPA to identify and then address what may well be many different 
sectors or groups of sources that are each part of--and thus 
contributing to--the problem.
    This framework recognizes that regulatory agencies such as EPA must 
be able to deal with the reality that ``[m]an's ability to alter his 
environment has developed far more rapidly than his ability to foresee 
with certainty the effects of his alterations.'' See Ethyl Corp v. EPA, 
541 F.2d 1, 6 (DC Cir.), cert. denied 426 U.S. 941 (1976). Both ``the 
Clean Air Act `and common sense * * * demand regulatory action to 
prevent harm, even if the regulator is less than certain that harm is 
otherwise inevitable.' '' See Massachusetts v. EPA, 549 U.S. at 506, 
n.7 (citing Ethyl Corp.).
    The Administrator recognizes that the context for this action is 
unique. There is a very large and comprehensive base of scientific 
information that has been developed over many years through a global 
consensus process involving numerous scientists from many countries and 
representing many disciplines. She also recognizes that there are 
varying degrees of uncertainty across many of these scientific issues. 
It is in this context that she is exercising her judgment and applying 
the statutory framework. As discussed in the Proposed Findings, this 
interpretation is based on and supported by the language in CAA section 
202(a), its legislative history and case law.
2. Summary of Response to Key Legal Comments on the Interpretation of 
the CAA Section 202(a) Endangerment and Cause or Contribute Test
    EPA received numerous comments regarding the interpretation of CAA 
section 202(a) set forth in the Proposed Findings. Below is a brief 
discussion of some of the key adverse legal comments and EPA's 
responses. Other key legal comments and EPA's responses are provided in 
later sections discussing the Administrator's findings.
    Additional and more detailed summaries and responses can be found 
in the Response to Comments document. As noted in the Response to 
Comments document, EPA also received comments supporting its legal 
interpretations.
a. The Administrator Properly Interpreted the Precautionary and 
Preventive Nature of the Statutory Language
    Various commenters argue either that the endangerment test under 
CAA section 202(a) is not precautionary and preventive in nature, or 
that EPA's interpretation and application is so extreme that it is 
contrary to what Congress intended in 1977, and effectively guarantees 
an affirmative endangerment finding. Commenters also argue that the 
endangerment test improperly shifts the burdens to the opponents of an 
endangerment finding and is tantamount to assuming the air pollution is 
harmful unless it is shown to be safe.
    EPA rejects the argument that the endangerment test in CAA section 
202(a) is not precautionary or preventive in nature. As discussed in 
more detail in the proposal, Congress relied heavily on the en banc 
decision in Ethyl when it revised section 202(a) and other CAA 
provisions to adopt the current language on endangerment and 
contribution. 74 FR 18886, 18891-2. The Ethyl court could not have been 
clearer on the precautionary nature of a criteria based on 
endangerment. The court rejected the argument that EPA had to find 
actual harm was occurring before it could make the required 
endangerment finding. The court stated that:

    The Precautionary Nature of ``Will Endanger.'' Simply as a 
matter of plain meaning, we have difficulty crediting petitioners' 
reading of the ``will endanger'' standard. The meaning of 
``endanger'' is not disputed. Case law and dictionary definition 
agree that endanger means something less than actual harm. When one 
is endangered, harm is threatened; no actual injury need ever occur. 
Thus, for example, a town may be ``endangered'' by a threatening 
plague or hurricane and yet emerge from the danger completely 
unscathed. A statute allowing for regulation in the face of danger 
is, necessarily, a precautionary statute. Regulatory action may be 
taken before the threatened harm occurs; indeed, the very existence 
of such precautionary legislation would seem to demand that 
regulatory action precede, and, optimally, prevent, the perceived 
threat. As should be apparent, the ``will endanger'' language of 
Section 211(c)(1)(A) makes it such a precautionary statute. Ethyl at 
13 (footnotes omitted).

    Similarly, the court stated that ``[i]n sum, based on the plain 
meaning of the statute, the juxtaposition of CAA section 211 with CAA 
sections 108 and 202, and the Reserve Mining precedent, we conclude 
that the ``will endanger'' standard is precautionary in nature and does 
not require proof of actual harm before regulation is appropriate.'' 
Ethyl at 17. It is this authority to act before harm has occurred that 
makes it a preventive, precautionary provision.
    It is important to note that this statement was in the context of 
rejecting an argument that EPA had to prove actual harm before it could 
adopt fuel control regulations under then CAA section 211(c)(1). The 
court likewise rejected the argument that EPA had to show that such 
harm was ``probable.''

[[Page 66507]]

The court made it clear that determining endangerment entails judgments 
involving both the risk or likelihood of harm and the severity of the 
harm if it were to occur. Nowhere did the court indicate that the 
burden was on the opponents of an endangerment finding to show that 
there was no endangerment. The opinion focuses on describing the burden 
the statute places on EPA, rejecting Ethyl's arguments of a burden to 
show actual or probable harm.
    Congress intentionally adopted a precautionary and preventive 
approach. It stated that the purpose of the 1977 amendments was to 
``emphasize the preventive or precautionary nature of the act, i.e., to 
assure that regulatory action can effectively prevent harm before it 
occurs; to emphasize the predominate value of protection to public 
health.'' \6\ Congress also stated that it authorized the Administrator 
to weigh risks and make projections of future trends, a ``middle road 
between those who would impose a nearly impossible standard of proof on 
the Administrator before he may move to protect public health and those 
who would shift the burden of proof for all pollutants to make the 
pollutant source prove the safety of its emissions as a condition of 
operation.'' Leg. His. at 2516.
---------------------------------------------------------------------------

    \6\ The Supreme Court recognized that the current language in 
section 202(a), adopted in 1977, is ``more protective'' than the 
1970 version that was similar to the section 211 language before the 
DC Circuit in Ethyl. Massachusetts v. EPA, 549 U.S. at 506, fn 7.
---------------------------------------------------------------------------

    Thus, EPA rejects commenters' arguments. Congress intended this 
provision to be preventive and precautionary in nature, however it did 
not shift the burden of proof to opponents of an endangerment finding 
to show safety or no endangerment. Moreover, as is demonstrated in the 
following, EPA has not shifted the burden of proof in the final 
endangerment finding, but rather is weighing the likelihood and 
severity of harms to arrive at the final finding. EPA has not applied 
an exaggerated or dramatically expanded precautionary principle, and 
instead has exercised judgment by weighing and balancing the factors 
that are relevant under this provision.
b. The Administrator Does Not Need To Find That the Control Measures 
Following an Endangerment Finding Would Prevent at Least a Substantial 
Part of the Danger in Order To Find Endangerment
    Several commenters argue that it is unlawful for EPA to make an 
affirmative endangerment finding unless EPA finds that the regulatory 
control measures contemplated to follow such a finding would prevent at 
least a substantial part of the danger from the global climate change 
at which the regulation is aimed. This hurdle is also described by 
commenters as the regulation ``achieving the statutory objective of 
preventing damage'', or ``fruitfully attacking'' the environmental and 
public health danger at hand by meaningfully and substantially reducing 
it. Commenters point to Ethyl Corp. v. EPA, 541 F.2d 1 (DC Cir. 1976) 
(en banc) as support for this view, as well as portions of the 
legislative history of this provision.
    Commenters contend that EPA has failed to show that this required 
degree of meaningful reduction of endangerment would be achieved 
through regulation of new motor vehicles based on an endangerment 
finding. In making any such showing, commenters argue that EPA would 
need to account for the following: (1) The fact that any regulation 
would be limited to new motor vehicles, if not the subset of new motor 
vehicles discussed in the President's May 2009 announcement, (2) any 
increase in emissions from purchasers delaying purchases of new 
vehicles subject to any greenhouse gas emissions standards, or 
increasing the miles traveled of new vehicles with greater fuel 
economy, (3) the fact that only a limited portion of the new motor 
vehicle emissions of greenhouse gases would be controlled, (4) the fact 
that CAFE standards would effectively achieve the same reductions, and 
(5) the fact that any vehicle standards would not themselves reduce 
global temperatures. Some commenters refer to EPA's proposal for 
greenhouse gas emissions standards for new motor vehicles as support 
for these arguments, claiming the proposed new motor vehicle emission 
standards are largely duplicative of the standards proposed by the 
National Highway Traffic Safety Administration (NHTSA), and the 
estimates of the impacts of the proposed standards confirm that EPA's 
proposed standards cannot ``fruitfully attack'' global climate change 
(74 FR 49454, September 28, 2009).
    Commenters attempt to read into the statute a requirement that is 
not there. EPA interprets the endangerment provision of CAA section 
202(a) as not requiring any such finding or showing as described by 
commenters. The text of CAA section 202(a) does not support such an 
interpretation. The endangerment provision calls for EPA, in its 
judgment, to determine whether air pollution is reasonably anticipated 
to endanger public health or welfare, and whether emissions from 
certain sources cause or contribute to such air pollution. If EPA makes 
an affirmative finding, then it shall set emissions standards 
applicable to emissions of such air pollutants from new motor vehicles. 
There is no reference in the text of the endangerment or cause or 
contribute provision to anything concerning the degree of reductions 
that would be achieved by the emissions standards that would follow 
such a finding. The Administrator's judgment is directed at the issues 
of endangerment and cause or contribute, not at how effective the 
resulting emissions control standards will be.
    As in the several other similar provisions adopted in the 1977 
amendments, in CAA section 202(a) Congress explicitly separated two 
different decisions to be made, providing different criteria for them. 
The first decision involves the air pollution and the endangerment 
criteria, and the contribution to the air pollution by the sources. The 
second decision involves how to regulate the sources to control the 
emissions if an affirmative endangerment and contribution finding are 
made. In all of the various provisions, there is broad similarity in 
the phrasing of the endangerment and contribution decision. However, 
for the decision on how to regulate, there are a wide variety of 
different approaches adopted by Congress. In some case, EPA has 
discretion whether to issue standards or not, while in other cases, as 
in CAA section 202(a), EPA is required to issue standards. In some 
cases, the regulatory criteria are general, as in CAA section 202(a); 
in others, they provide significantly more direction as to how 
standards are to be set, as in CAA section 213(a)(4).
    As the Supreme Court made clear in Massachusetts v. EPA, EPA's 
judgment in making the endangerment and contribution findings is 
constrained by the statute, and EPA is to decide these issues based 
solely on the scientific and other evidence relevant to that decision. 
EPA may not ``rest[] on reasoning divorced from the statutory text,'' 
and instead EPA's exercise of judgment must relate to whether an air 
pollutant causes or contributes to air pollution that endangers. 
Massachusetts v. EPA, 549 U.S. at 532. As the Supreme Court noted, EPA 
must ``exercise discretion within defined statutory limits.'' Id. at 
533. EPA's belief one way or the other regarding whether regulation of 
greenhouse gases from new motor vehicles would be ``effective'' is 
irrelevant in making the endangerment and contribution decisions before 
EPA. Id. Instead ``[t]he statutory question is

[[Page 66508]]

whether sufficient information exists to make an endangerment finding'' 
Id. at 534.
    The effectiveness of a potential future control strategy is not 
relevant to deciding whether air pollution levels in the atmosphere 
endanger. It is also not relevant to deciding whether emissions of 
greenhouse gases from new motor vehicles contribute to such air 
pollution. Commenters argue that Congress implicitly imposed a third 
requirement, that the future control strategy have a certain degree of 
effectiveness in reducing the endangerment before EPA could make the 
affirmative findings that would authorize such regulation. There is no 
statutory text that supports such an interpretation, and the Supreme 
Court makes it clear that EPA has no discretion to read this kind of 
additional factor into CAA section 202(a)'s endangerment and 
contribution criteria. In fact, the Supreme Court rejected similar 
arguments that EPA had the discretion to consider various other factors 
besides endangerment and contribution in deciding whether to deny a 
petition. Massachusetts v. EPA, 549 U.S. at 532-35.
    Commenters point to language from the Ethyl case to support their 
position, noting that the DC Circuit referred to the emissions control 
regulation adopted by EPA under CAA section 211(c) as one that would 
``fruitfully attack'' the environmental and public health danger by 
meaningfully and substantially reducing the danger. It is important to 
understand the context for this discussion in Ethyl. The petitioner 
Ethyl Corp. argued that EPA had to show that the health threat from the 
emissions of lead from the fuel additive being regulated had to be 
considered in isolation, and the threat ``in and of itself'' from the 
additive had to meet the test of endangerment in CAA section 211(c). 
EPA had rejected this approach, and had interpreted CAA section 
211(c)(1) as calling for EPA to look at the cumulative impact of lead, 
and to consider the impact of lead from emissions related to use of the 
fuel additive in the context all other human exposure to lead. The 
court rejected Ethyl's approach and supported EPA's interpretation. The 
DC Circuit noted that Congress was fully aware that the burden of lead 
on the body was caused by multiple sources and that it would be of no 
value to try and determine the effect on human health from the lead 
automobile emissions by themselves. The court specifically noted that 
``the incremental effect of lead emissions on the total body lead 
burden is of no practical value in determining whether health is 
endangered,'' but recognized that this incremental effect is of value 
``in deciding whether the lead exposure problem can fruitfully be 
attacked through control of lead additives.'' Ethyl, 541 F.2d at 31 fn 
62. The court made clear that the factor that was critically important 
to determining the effectiveness of the resulting control strategy--the 
incremental effect of automobile lead emissions on total body burden--
was irrelevant and of no value in determining whether the endangerment 
criteria was met. Thus it is clear that the court in Ethyl did not 
interpret then CAA section 211(c)(1)(A) as requiring EPA to make a 
showing of the effectiveness of the resulting emissions control 
strategy, and instead found just the opposite, that the factors that 
would determine effectiveness are irrelevant to determining 
endangerment.
    Commenters also cite to the legislative history, noting that 
Congress referred to the ``preventive or precautionary nature of the 
Act, i.e., to assure that regulatory action can effectively prevent 
harm before it occurs.'' Leg. Hist. at 2516. However, this statement by 
Congress is presented as an answer to the question on page 2515, 
``Should the Administrator act to prevent harm before it occurs or 
should he be authorized to regulate an air pollutant only if he finds 
actual harm has already occurred.'' Leg. Hist. at 2515. In this 
context, the discussion on page 2516 clearly indicates that there is no 
opportunity for prevention or precaution if the test is one of actual 
harm already occurring. This discussion does not say or imply that even 
if the harm has not occurred, you can not act unless you also show that 
your action will effectively address it. This discussion concerns the 
endangerment test, not the criteria for standard setting. The criteria 
for standard setting address how the agency should act to address the 
harm, and as the Ethyl case notes, the factors relevant to how to 
``fruitfully attack'' the harm are irrelevant to determining whether 
the harm is one that endangers the public health or welfare.
    As with current CAA section 202(a), there is no basis to conflate 
these two separate decisions and to read into the endangerment criteria 
an obligation that EPA show that the resulting emissions control 
strategy or strategies will have some significant degree of harm 
reduction or effectiveness in addressing the endangerment. The 
conflating of the two decisions is not supported in the text of this 
provision, by the Supreme Court in Massachusetts v. EPA, by the DC 
Circuit in Ethyl, or by Congress in the legislative history of this 
provision. It would be an unworkable interpretation, calling for EPA to 
project out the result of perhaps not one, but even several, future 
rulemakings stretching over perhaps a decade or decades. Especially in 
the context of global climate change, the effectiveness of a control 
strategy for new motor vehicles would have to be viewed in the context 
of a number of future motor vehicle regulations, as well as in the 
larger context of the CAA and perhaps even global context. That would 
be an unworkable and speculative requirement to impose on EPA as a 
precondition to answering the public health and welfare issues before 
it, as they are separate and apart from the issues involved with 
developing, implementing and evaluating the effectiveness of emissions 
control strategies.
c. The Administrator Does Not Need To Find There Is Significant Risk of 
Harm
    Commenters argue that Congress established a minimum requirement 
that there be a ``significant risk of harm'' to find endangerment. They 
contend that this requirement stemmed from the Ethyl case, and that 
Congress adopted this view. According to the commenters, the risk is 
the function of two variables: the nature of the hazard at issue and 
the likelihood of its occurrence. Commenters argue that Congress 
imposed a requirement that this balance demonstrate a ``significant 
risk of harm'' to strike a balance between the precautionary nature of 
the CAA and the burdensome economic and societal consequences of 
regulation.
    There are two basic problems with the commenters' arguments. First, 
commenters equate ``significant risk of harm'' as the overall test for 
endangerment, however the Ethyl case and the legislative history treat 
the risk of harm as only one of the two components that are to be 
considered in determining endangerment.--, The two components are the 
likelihood or risk of a harm occurring, and the severity of harm if it 
were to occur. Second, commenters equate it to a minimum statutory 
requirement. However, while the court in the Ethyl case made it clear 
that the facts in that case met the then applicable endangerment 
criteria, it also clearly said it was not determining what other facts 
or circumstances might amount to endangerment, including cases where 
the likelihood of a harm occurring was less than a significant risk of 
the harm.
    In the EPA rulemaking that led to the Ethyl case, EPA stated that 
the requirement to reduce lead in gasoline ``is based on the finding 
that lead

[[Page 66509]]

particle emissions from motor vehicles present a significant risk of 
harm to the health of urban populations, particularly to the health of 
city children'' (38 FR 33734, December 6, 1973). The court in Ethyl 
supported EPA's determination, and addressed a variety of issues. 
First, it determined that the ``will endanger'' criteria of then CAA 
section 211(c) was intended to be precautionary in nature. It rejected 
arguments that EPA had to show proof of actual harm, or probable harm. 
Ethyl, 541 F.2d at 13-20. It was in this context, evaluating 
petitioner's arguments on whether the likelihood of a harm occurring 
had to rise to the level of actual or probable harm, that the court 
approved of EPA's view that a significant risk of harm could satisfy 
the statutory criteria. The precautionary nature of the provision meant 
that EPA did not need to show that either harm was actually occurring 
or was probable.
    Instead, the court made it clear that the concept of endangerment 
is ``composed of reciprocal elements of risk and harm,'' Ethyl at 18. 
This means ``the public health may properly be found endangered both by 
a lesser risk of a greater harm and by a greater risk of lesser harm. 
Danger depends upon the relation between the risk and harm presented by 
each case, and cannot legitimately be pegged to `probable' harm, 
regardless of whether that harm be great or small.'' The Ethyl court 
pointed to the decision by the 8th Circuit in Reserve Mining Co. v. 
EPA, 514 F.2d 492 (8th Cir, 1975), which interpreted similar language 
under the Federal Water Pollution Control Act, where the 8th Circuit 
upheld an endangerment finding in a case involving ``reasonable medical 
concern,'' or a ``potential'' showing of harm. This was further 
evidence that a minimum ``probable'' likelihood of harm was not 
required.
    The Ethyl court made it clear that there was no specific magnitude 
of risk of harm occurring that was required. ``Reserve Mining 
convincingly demonstrates that the magnitude of risk sufficient to 
justify regulation is inversely proportional to the harm to be 
avoided.'' Ethyl at 19. This means there is no minimum requirement that 
the magnitude of risk be ``significant'' or another specific level of 
likelihood of occurrence. You need to evaluate the risk of harm in the 
context of the severity of the harm if it were to occur. In the case 
before it, the Ethyl court noted that ``the harm caused by lead 
poisoning is severe.'' Even with harm as severe as lead poisoning, EPA 
did not rely on ``potential'' risk or a ``reasonable medical concern.'' 
Instead, EPA found that there was a significant risk of this harm to 
health. This finding of a significant risk was less than the level of 
``probable'' harm called for by the petitioner Ethyl Corporation but 
was ``considerably more certain than the risk that justified regulation 
in Reserve Mining of a comparably `fright-laden' harm.'' Ethyl at 19-
20. The Ethyl court concluded that this combination of risk (likelihood 
of harm) and severity of harm was sufficient under CAA section 211(c). 
``Thus we conclude that however far the parameters of risk and harm 
inherent in the `will endanger' standard might reach in an appropriate 
case, they certainly present a `danger' that can be regulated when the 
harm to be avoided is widespread lead poisoning and the risk of that 
occurrence is `significant'.'' Ethyl at 20.
    Thus, the court made it clear that the endangerment criteria was 
intended to be precautionary in nature, that the risk of harm was one 
of the elements to consider in determining endangerment, and that the 
risk of harm needed to be considered in the context of the severity of 
the potential harm. It also concluded that a significant risk of harm 
coupled with an appropriate severity of the potential harm would 
satisfy the statutory criteria, and in the case before it the 
Administrator was clearly authorized to determine endangerment where 
there was a significant risk of harm that was coupled with a severe 
harm such as lead poisoning.
    Importantly, the court also made it clear that it was not 
determining a minimum threshold that always had to be met. Instead, it 
emphasized that the risk of harm and severity of the potential harm had 
to be evaluated on a case by case basis. The court specifically said it 
was not determining ``however far the parameters of risk and harm * * * 
might reach in an appropriate case.'' Ethyl at 20. Also see Ethyl fn 17 
at 13. The court recognized that this balancing of risk and harm ``must 
be confined to reasonable limits'' and even absolute certainty of a de 
minimis harm might not justify government action. However, ``whether a 
particular combination of slight risk and great harm, or great risk and 
slight harm constitutes a danger must depend on the facts of each 
case.'' Ethyl at fn 32 at 18.\7\
---------------------------------------------------------------------------

    \7\ Commenters point to Amer. Farm Bureau Ass'n v. EPA, 559 F.3d 
512, 533 (DC Cir. 2009) as supporting their argument. However, in 
that case the Court made clear that EPA's action was not subject to 
the endangerment criterion in CAA section 108 but instead was 
subject to CAA section 109's requirement that the primary NAAQS be 
requisite to protect the public health with an adequate margin of 
safety. Under that provision and its case law, the Court upheld 
EPA's reasoned balancing of the uncertainty regarding the link 
between non-urban thoracic coarse PM and adverse health effects, the 
large population groups potentially exposed to these particles, and 
the nature and degree of the health effects at issue. Citing to 
EPA's reasoning at 71 FR 61193 in the final PM rule, the court 
explained that EPA need not wait for conclusive proof of harm before 
setting a NAAQS under section 109 for this kind of coarse PM. The 
Court's reference to EPA's belief that there may be a significant 
risk to public health is not stated as any sort of statutory 
minimum, but instead refers to the Agency's reasoning at 71 FR 
61193, which displays a reasoned balancing of possibility of harm 
and severity of harm if it were to occur.
---------------------------------------------------------------------------

    In some cases, commenters confuse matters by switching the 
terminology, and instead refer to effects that ``significantly harm'' 
the public health or welfare. As with the reference to ``significant 
risk of harm,'' commenters fail to recognize that there are two 
different aspects that must be considered, risk of harm and severity of 
harm, and neither of these aspects has a requirement that there be a 
finding of ``significance.'' The DC Circuit in Ethyl makes clear that 
it is the combination of these two aspects that must be evaluated for 
purposes of endangerment, and there is no requirement of 
``significance'' assigned to either of the two aspects that must 
instead be evaluated in combination. Congress addressed concerns over 
burdensome economic and societal consequences in the various statutory 
provisions that provide the criteria for standard setting or other 
agency action if there is an affirmative endangerment finding. Those 
statutory provisions, for example, make standard setting discretionary 
or specify how cost and other factors are to be taken into 
consideration in setting standards. However, the issues of risk of harm 
and severity of harm if it were to occur are separate from the issues 
of the economic impacts of any resulting regulatory provisions (see 
below).
    As is clear in the prior summary of the endangerment findings and 
the more detailed discussion later, the breadth of the sectors of our 
society that are affected by climate change and the time frames at 
issue mean there is a very wide range of risks and harms that need to 
be considered, from evidence of various harms occurring now to evidence 
of risks of future harms. The Administrator has determined that the 
body of scientific evidence compellingly supports her endangerment 
finding.

B. Air Pollutant, Public Health and Welfare

    The CAA defines both ``air pollutant'' and ``effects on welfare.'' 
We provide both definitions here again for convenience.
    Air pollutant is defined as:

[[Page 66510]]

    ``Any air pollution agent or combination of such agents, including 
any physical, chemical, biological, radioactive (including source 
material, special nuclear material, and byproduct material) substance 
or matter which is emitted into or otherwise enters the ambient air. 
Such term includes any precursors to the formation of any air 
pollutant, to the extent the Administrator has identified such 
precursor or precursors for the particular purpose for which the term 
``air pollutant'' is used.'' CAA section 302(g). As the Supreme Court 
held, greenhouse gases fit well within this capacious definition. See 
Massachusetts v. EPA, 549 U.S. at 532. They are ``without a doubt'' 
physical chemical substances emitted into the ambient air. Id. at 529.
    ``Regarding `effects on welfare', the CAA states that [a]ll 
language referring to effects on welfare includes, but is not limited 
to, effects on soils, water, crops, vegetation, man-made materials, 
animals, wildlife, weather, visibility, and climate, damage to and 
deterioration of property, and hazards to transportation, as well as 
effects on economic values and on personal comfort and well-being, 
whether caused by transformation, conversion, or combination with other 
air pollutants.'' CAA section 302(h).
    As noted in the Proposed Findings, this definition is quite broad. 
Importantly, it is not an exclusive list due to the use of the term 
``includes, but is not limited to, * * * .'' Effects other than those 
listed here may also be considered effects on welfare. Moreover, the 
terms contained within the definition are themselves expansive.
    Although the CAA defines ``effects on welfare'' as discussed above, 
there are no definitions of ``public health'' or ``public welfare'' in 
the CAA. The Supreme Court has discussed the concept of public health 
in the context of whether costs of implementation can be considered 
when setting the health based primary National Ambient Air Quality 
Standards. Whitman v. American Trucking Ass'n, 531 U.S. 457 (2001). In 
Whitman, the Court imbued the term with its most natural meaning: ``the 
health of the public. Id. at 466. In the past, when considering public 
health, EPA has looked at morbidity, such as impairment of lung 
function, aggravation of respiratory and cardiovascular disease, and 
other acute and chronic health effects, as well as mortality. See, 
e.g., Final National Ambient Air Quality Standard for Ozone, (73 FR 
16436, 2007).
    EPA received numerous comments regarding its proposed 
interpretations of air pollutant and public health and welfare. 
Summaries of key comments and EPA's responses are discussed in Sections 
IV and V of these Findings. Additional and more detailed summaries and 
responses can be found in the Response to Comments document. As noted 
in the Response to Comments document, EPA also received comments 
supporting its legal interpretations.

III. EPA's Approach for Evaluating the Evidence Before It

    This section discusses EPA's approach to evaluating the evidence 
before it, including the approach taken to the scientific evidence, the 
legal framework for this decision making, and several issues critical 
to determining the scope of the evaluation performed.

A. The Science on Which the Decisions Are Based

    In 2007, EPA initiated its assessment of the science and other 
technical information to use in addressing the endangerment and cause 
or contribute issues before it under CAA section 202(a). This 
scientific and technical information was developed in the form of a TSD 
in 2007. An earlier draft of this document was released as part of the 
ANPR published July 30, 2008 (73 FR 44353). That earlier draft of the 
TSD relied heavily on the IPCC Fourth Assessment Report of 2007, key 
NRC reports, and a limited number of then-available synthesis and 
assessment products of the U.S. Climate Change Science Program (CCSP; 
now encompassed by USGCRP). EPA received a number of comments 
specifically focused on the TSD during the 120-day public comment 
period for the ANPR.
    EPA revised and updated the TSD in preparing the Proposed Findings 
on endangerment and cause or contribute. Many of the comments received 
on the ANPR were reflected in the draft TSD released in April 2009 that 
served as the underlying scientific and technical basis for the 
Administrator's Proposed Findings, published April 24, 2009 (74 FR 
18886). The draft TSD released in April 2009 also reflected the 
findings of 11 new synthesis and assessment products under the U.S. 
CCSP that had been published since July 2008.
    The TSD that summarizes scientific findings from the major 
assessments of the USGCRP, the IPCC, and the NRC accompanies these 
Findings. The TSD is available at www.epa.gov/climatechange/endangerment.html and in the docket for this action. It also includes 
the most recent comprehensive assessment of the USGCRP, Global Climate 
Change Impacts in the United States,\8\ published in June 2009. In 
addition, the TSD incorporates up-to-date observational data for a 
number of key climate variables from the NOAA, and the most up-to-date 
emissions data from EPA's annual Inventory of U.S. Greenhouse Gas 
Emissions and Sinks, published in April, 2009.\9\ And finally, as 
discussed in Section I.B of these Findings, EPA received a large number 
of public comments on the Administrator's Proposed Findings, many of 
which addressed science issues either generally or specifically as 
reflected in the draft TSD released with the April 2009 proposal. A 
number of edits and updates were made to the draft TSD as a result of 
these comments.\10\
---------------------------------------------------------------------------

    \8\ Karl, T., J. Melillo, and T. Peterson (Eds.) (2009) Global 
Climate Change Impacts in the United States. Cambridge University 
Press, Cambridge, United Kingdom.
    \9\ U.S. EPA (2009) Inventory of U.S. Greenhouse Gas Emissions 
and Sinks: 1990-2007. EPA-430-R-09-004, Washington, DC.
    \10\ EPA has placed within the docket a separate memo ``Summary 
of Major Changes to the Technical Support Document'' identifying 
where within the TSD such changes were made relative to the draft 
TSD released in April 2009.
---------------------------------------------------------------------------

    EPA is giving careful consideration to all of the scientific and 
technical information in the record, as discussed below. However, the 
Administrator is relying on the major assessments of the USGCRP, IPCC, 
and NRC as the primary scientific and technical basis of her 
endangerment decision for a number of reasons.
    First, these assessments address the scientific issues that the 
Administrator must examine for the endangerment analysis. When viewed 
in total, these assessments address the issue of greenhouse gas 
endangerment by providing data and information on: (1) The amount of 
greenhouse gases being emitted by human activities; (2) how greenhouse 
gases have been and continue to accumulate in the atmosphere as a 
result of human activities; (3) changes to the Earth's energy balance 
as a result of the buildup of atmospheric greenhouse gases; (4) 
observed temperature and other climatic changes at the global and 
regional scales; (5) observed changes in other climate-sensitive 
sectors and systems of the human and natural environment; (6) the 
extent to which observed climate change and other changes in climate-
sensitive systems can be attributed to the human-induced buildup of 
atmospheric greenhouse gases; (7) future projected climate change under 
a range of different scenarios of changing greenhouse gas emission 
rates; and (8) the projected risks and impacts to

[[Page 66511]]

human health, society and the environment.
    Second, as indicated above, these assessments are recent and 
represent the current state of knowledge on the key elements for the 
endangerment analysis. It is worth noting that the June 2009 assessment 
of the USGCRP incorporates a number of key findings from the 2007 IPCC 
Fourth Assessment Report; such findings include the attribution of 
observed climate change to human emissions of greenhouse gases, and the 
future projected scenarios of climate change for the global and 
regional scales. This demonstrates that much of the underlying science 
that EPA has been utilizing since 2007 has not only been in the public 
domain for some time, but also has remained relevant and robust.
    Third, these assessments are comprehensive in their coverage of the 
greenhouse gas and climate change problem, and address the different 
stages of the emissions-to-potential-harm chain necessary for the 
endangerment analysis. In so doing, they evaluate the findings of 
numerous individual peer-reviewed studies in order to draw more general 
and overarching conclusions about the state of science. The USGCRP, 
IPCC, and NRC assessments synthesize literally thousands of individual 
studies and convey the consensus conclusions on what the body of 
scientific literature tells us.
    Fourth, these assessment reports undergo a rigorous and exacting 
standard of peer review by the expert community, as well as rigorous 
levels of U.S. government review and acceptance. Individual studies 
that appear in scientific journals, even if peer reviewed, do not go 
through as many review stages, nor are they reviewed and commented on 
by as many scientists. The review processes of the IPCC, USGCRP, and 
NRC (explained in fuller detail in the TSD and the Response to Comments 
document, Volume 1) provide EPA with strong assurance that this 
material has been well vetted by both the climate change research 
community and by the U.S. government. These assessments therefore 
essentially represent the U.S. government's view of the state of 
knowledge on greenhouse gases and climate change. For example, with 
regard to government acceptance and approval of IPCC assessment 
reports, the USGCRP Web site states that: ``When governments accept the 
IPCC reports and approve their Summary for Policymakers, they 
acknowledge the legitimacy of their scientific content.'' \11\ It is 
the Administrator's view that such review and acceptance by the U.S. 
Government lends further support for placing primary weight on these 
major assessments.
---------------------------------------------------------------------------

    \11\ http://www.globalchange.gov/publications/reports/ipcc-reports.
---------------------------------------------------------------------------

    It is EPA's view that the scientific assessments of the IPCC, 
USGRCP, and the NRC represent the best reference materials for 
determining the general state of knowledge on the scientific and 
technical issues before the agency in making an endangerment decision. 
No other source of information provides such a comprehensive and in-
depth analysis across such a large body of scientific studies, adheres 
to such a high and exacting standard of peer review, and synthesizes 
the resulting consensus view of a large body of scientific experts 
across the world. For these reasons, the Administrator is placing 
primary and significant weight on these assessment reports in making 
her decision on endangerment.
    A number of commenters called upon EPA to perform a new and 
independent assessment of all of the underlying climate change science, 
separate and apart from USGCRP, IPCC, and NRC. In effect, commenters 
suggest that EPA is either required to or should ignore the attributes 
discussed above concerning these assessment reports, and should instead 
perform its own assessment of all of the underlying studies and 
information.
    In addition to the significant reasons discussed above for relying 
on and placing primary weight on these assessment reports, EPA has been 
a very active part of the U.S. government climate change research 
enterprise, and has taken an active part in the review, writing, and 
approval of these assessments. EPA was the lead agency for three 
significant reports under the USGCRP \12\, and recently completed an 
assessment addressing the climate change impacts on U.S. air quality--a 
report on which the TSD heavily relies for that particular issue. EPA 
was also involved in review of the IPCC Fourth Assessment Report, and 
in particular took part in the approval of the summary for policymakers 
for the Working Group II Volume, Impacts, Adaptation and 
Vulnerability.\13\ The USGCRP, IPCC, and NRC assessments have been 
reviewed and formally accepted by, commissioned by, or in some cases 
authored by, U.S. government agencies and individual government 
scientists. These reports already reflect significant input from EPA's 
scientists and the scientists of many other government agencies.
---------------------------------------------------------------------------

    \12\ CCSP (2009) Coastal Sensitivity to Sea-Level Rise: A Focus 
on the Mid-Atlantic Region. A Report by the U.S. Climate Change 
Science Program and the Subcommittee on Global Change Research. 
[James G. Titus (Coordinating Lead Author), K. Eric Anderson, Donald 
R. Cahoon, Dean B. Gesch, Stephen K. Gill, Benjamin T. Gutierrez, E. 
Robert Thieler, and S. Jeffress Williams (Lead Authors)], U.S. 
Environmental Protection Agency, Washington DC, USA, 320 pp. CCSP 
(2008) Preliminary review of adaptation options for climate-
sensitive ecosystems and resources. A Report by the U.S. Climate 
Change Science Program and the Subcommittee on Global Change 
Research. [Julius, S.H., J.M. West (eds.), J.S. Baron, B. Griffith, 
L.A. Joyce, P. Kareiva, B.D. Keller, M.A. Palmer, C.H. Peterson, and 
J.M. Scott (Authors)]. U.S. Environmental Protection Agency, 
Washington, DC, USA, 873 pp. CCSP (2008) Analyses of the effects of 
global change on human health and welfare and human systems. A 
Report by the U.S. Climate Change Science Program and the 
Subcommittee on Global Change Research. [Gamble, J.L. (ed.), K.L. 
Ebi, F.G. Sussman, T.J. Wilbanks, (Authors)]. U.S. Environmental 
Protection Agency, Washington, DC, USA.
    \13\ IPCC (2007) Climate Change 2007: Impacts, Adaptation and 
Vulnerability. Contribution of Working Group II to the Fourth 
Assessment Report of the Intergovernmental Panel on Climate Change, 
M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and 
C.E. Hanson, Eds., Cambridge University Press, Cambridge, UK, 976pp.
---------------------------------------------------------------------------

    EPA has no reason to believe that the assessment reports do not 
represent the best source material to determine the state of science 
and the consensus view of the world's scientific experts on the issues 
central to making an endangerment decision with respect to greenhouse 
gases. EPA also has no reason to believe that putting this significant 
body of work aside and attempting to develop a new and separate 
assessment would provide any better basis for making the endangerment 
decision, especially because any such new assessment by EPA would still 
have to give proper weight to these same consensus assessment reports.
    In summary, EPA concludes that its reliance on existing and recent 
synthesis and assessment reports is entirely reasonable and allows EPA 
to rely on the best available science.\14\ EPA also recognizes that 
scientific research is very active in many areas addressed in the TSD 
(e.g., aerosol effects on climate, climate feedbacks such as water 
vapor, and internal and external climate forcing mechanisms), as well 
as for some emerging issues (e.g., ocean acidification and climate 
change effects on water quality). EPA recognizes the potential 
importance of new scientific research, and the value of an ongoing 
process to take more recent science into account. EPA reviewed new 
literature in

[[Page 66512]]

preparation of this TSD to evaluate its consistency with recent 
scientific assessments. We also considered public comments received and 
studies incorporated by reference. In a number of cases, the TSD was 
updated based on such information to add context for assessment 
literature findings, which includes supporting information and/or 
qualifying statements. In other cases, material that was not 
incorporated into the TSD is discussed within the Response to Comments 
document.
---------------------------------------------------------------------------

    \14\ It maintains the highest level of adherence to Agency and 
OMB guidelines for data and scientific integrity and transparency. 
This is discussed in greater detail in EPA's Response to Comments 
document.
---------------------------------------------------------------------------

    EPA reviewed these individual studies that were not considered or 
reflected in these major assessments to evaluate how they inform our 
understanding of how greenhouse gas emissions affect climate change, 
and how climate change may affect public health and welfare. Given the 
very large body of studies reviewed and assessed in developing the 
assessment reports, and the rigor and breadth of that review and 
assessment, EPA placed limited weight on the much smaller number of 
individual studies that were not considered or reflected in the major 
assessments. EPA reviewed them largely to see if they would lead EPA to 
change or place less weight on the judgments reflected in the 
assessment report. While EPA recognizes that some studies are more 
useful or informative than others, and gave each study it reviewed the 
weight it was due, the overall conclusion EPA drew from its review of 
studies submitted by commenters was that the studies did not change the 
various conclusions or judgments EPA would draw based on the assessment 
reports.
    Many comments focus on the scientific and technical data underlying 
the Proposed Findings, such as climate change science and greenhouse 
gas emissions data. These comments cover a range of topics and are 
summarized and responded to in the Response to Public Comments 
document. The responses note those cases where a technical or 
scientific comment resulted in an editorial or substantive change to 
the TSD. The final TSD reflects all changes made as a result of public 
comments.

B. The Law on Which the Decisions Are Based

    In addition to grounding these determinations on the science, they 
are also firmly grounded in EPA's legal authority. Section II of these 
Findings provides an in-depth discussion of the legal framework for the 
endangerment and cause or contribute decisions under CAA section 
202(a), with additional discussion in Section II of the Proposed 
Finding (74 FR 18886, 18890, April 24, 2009). A variety of important 
legal issues are also discussed in Sections III, IV, and V of these 
Findings, as well as in the Response to Comments document, Volume 11. 
Section IV and V of these Findings explain the Administrator's 
decisions, and how she exercised her judgment in making the 
endangerment and contribution determinations, based on the entire 
scientific record before her and the legal framework structuring her 
decision making.

C. Adaptation and Mitigation

    Following the language of CAA section 202(a), in which the 
Administrator, in her judgment, must determine if greenhouse gases 
constitute the air pollution that may be reasonably anticipated to 
endanger public health or welfare, EPA evaluated, based primarily on 
the scientific reports discussed above, how greenhouse gases and other 
climate-relevant substances are affecting the atmosphere and climate, 
and how these climate changes affect public health and welfare, now and 
in the future. Consistent with EPA's scientific approach underlying the 
Administrator's Proposed Findings, EPA did not undertake a separate 
analysis to evaluate potential societal and policy responses to any 
threat (i.e., the endangerment) that may exist due to anthropogenic 
emissions of greenhouse gases. Risk reduction through adaptation and 
greenhouse gas mitigation measures is of course a strong focal area of 
scientists and policy makers, including EPA; however, EPA considers 
adaptation and mitigation to be potential responses to endangerment, 
and as such has determined that they are outside the scope of the 
endangerment analysis.
    The Administrator's position is not that adaptation will not occur 
or cannot help protect public health and welfare from certain impacts 
of climate change, as some commenters intimated. To the contrary, EPA 
recognizes that some level of autonomous adaptation \15\ will occur, 
and commenters are correct that autonomous adaptation can affect the 
severity of climate change impacts. Indeed, there are some cases in the 
TSD in which some degree of adaptation is accounted for; these cases 
occur where the literature on which the TSD relies already uses 
assumptions about autonomous adaptation when projecting the future 
effects of climate change. Such cases are noted in the TSD. We also 
view planned adaptation as an important near-term risk-minimizing 
strategy given that some degree of climate change will continue to 
occur as a result of past and current emissions of greenhouse gases 
that remain in the atmosphere for decades to centuries.
---------------------------------------------------------------------------

    \15\ The IPCC definition of adaptation: ``Adaptation to climate 
change takes place through adjustments to reduce vulnerability or 
enhance resilience in response to observed or expected changes in 
climate and associated extreme weather events. Adaptation occurs in 
physical, ecological and human systems. It involves changes in 
social and environmental processes, perceptions of climate risk, 
practices and functions to reduce potential damages or to realize 
new opportunities.'' The IPCC defines autonomous adaptation as 
``Adaptation that does not constitute a conscious response to 
climatic stimuli but is triggered by ecological changes in natural 
systems and by market or welfare changes in human systems.''
---------------------------------------------------------------------------

    However, it is the Administrator's position that projections of 
adaptation and mitigation in response to risks and impacts associated 
with climate change are not appropriate for EPA to consider in making a 
decision on whether the air pollution endangers. The issue before EPA 
involves evaluating the risks to public health and welfare from the air 
pollution if we do not take action to address it. Adaptation and 
mitigation address an important but different issue--how much risk will 
remain assuming some projection of how people and society will respond 
to the threat.
    Several commenters argue that it is arbitrary not to consider 
adaptation in determining endangerment. They contend that because 
endangerment is a forward-looking exercise, the fundamental inquiry 
concerns the type and extent of harm that is believed likely to occur 
in the future. Just as the Administrator makes projections of potential 
harms in the future, these commenters contend that the Administrator 
needs to consider the literature on adaptation that addresses the 
likelihood and the severity of potential effects. Commenters also note 
that since adaption is one of the likely impacts of climate change, it 
is irrational to exclude it from consideration when the goal is to 
evaluate the risks and harms in the real world in the future, not the 
risks and harms in the hypothetical scenario that result if you ignore 
adaptation.
    According to commenters, the Administrator must consider both 
autonomous adaptation and anticipatory adaptation. They contend that 
literature on adaptation makes it clear there is a significant 
potential for adaptation, and that it can reduce the likelihood or 
severity of various effects, including health effects, and could even 
avert what might otherwise constitute endangerment. Commenters note 
that EPA considered the adaptation of species in nature, and it is 
arbitrary to not also consider adaptation by humans. Moreover, they 
argue that there is great

[[Page 66513]]

certainty that adaptation will occur, and thus EPA is required to 
address it and make projections. They recommend that EPA look to 
historic responses to changes in conditions as an analogue in making 
projections, recognizing that life in the United States is likely to be 
quite different 50 or 100 years from now, irrespective of climate 
change.
    Commenters argue that adaption needs to be considered because it is 
central to the statutory requirements governing the endangerment 
inquiry. EPA is charged to determine the type and extent of harms that 
are likely to occur, and they argue that this can not rationally be 
considered without considering adaptation. Since some degree of 
adaptation is likely to occur, they continue that such a projection of 
future actual conditions requires consideration of adaption to evaluate 
whether the future conditions amount to endangerment from the air 
pollution.
    According to commenters, the issue therefore is focused on human 
and societal adaptation, which can come in a wide variety of forms, 
ranging from changes in personal behavioral patterns to expenditures of 
resources to change infrastructure, such as building and maintaining 
barriers to protect against sea level rise.
    With regard to mitigation, commenters argue that EPA should 
consider mitigation strategies and their potential to alleviate harm 
from greenhouse gas emissions. They contend that it is unreasonable for 
EPA to assume that society will not undertake mitigation.
    Section 202(a) of the CAA reflects the basic approach of many CAA 
sections--the threshold inquiry is whether the endangerment and cause 
or contribute criteria are satisfied, and only if they are met do the 
criteria for regulatory action go into effect. This reflects the basic 
separation of two different decisions--is this a health and welfare 
problem that should be addressed, and if so what are the appropriate 
mechanisms to address it? There is a division between identifying the 
health and welfare problem associated with the air pollution, and 
identifying the mechanisms used to address or solve the problem.
    In evaluating endangerment, EPA is determining whether the risks to 
health and welfare from the air pollution amount to endangerment. As 
commenters recognize, that calls for evaluating and projecting the 
nature and types of risks from the air pollution, including the 
probability or likelihood of the occurrence of an impact and the degree 
of adversity (or benefit) of such an impact. This issue focuses on how 
EPA makes such an evaluation in determining endangerment--does EPA look 
at the risks assuming no planned adaptation and/or mitigation, although 
EPA projects some degree is likely to occur, or does EPA look at the 
risks remaining after some projection of adaptation and/or mitigation?
    These two approaches reflect different views of the core question 
EPA is trying to answer. The first approach most clearly focuses on 
just the air pollution and its impacts, and aims to separate this from 
the human and societal responses that may or should be taken in 
response to the risks from the air pollution. By its nature, this 
separation means this approach may not reflect the actual conditions in 
the real world in the future, because adaptation and/or mitigation may 
occur and change the risks. For example, adaptation would not change 
the atmospheric concentrations, or the likelihood or probability of 
various impacts occurring (e.g., it would not change the degree of sea 
level rise), but adaptation has the potential to reduce the adversity 
of the effects that do occur from these impacts. Mitigation could 
reduce the atmospheric concentrations that would otherwise occur, 
having the potential to reduce the likelihood or probability of various 
impacts occurring. Under this approach, the evaluation of risk is 
focused on the risk if we do not address the problem. It does not 
answer the question of how much risk we project will remain after we do 
address the problem, through either adaptation or mitigation or some 
combination of the two.
    The second approach, suggested by commenters, would call for EPA to 
project into the future adaptation and/or mitigation, and the effect of 
these measures in reducing the risks to health or welfare from the air 
pollution. Commenters argue this will better reflect likely real world 
conditions, and therefore is needed to allow for an appropriate 
determination of whether EPA should, at this time, make an affirmative 
endangerment finding. However, this approach would not separate the air 
pollution and its impacts from the human and societal responses to the 
air pollution. It would intentionally and inextricably intertwine them. 
It would inexorably change the focus from how serious is the air 
pollution problem we need to address to how good a job are people and 
society likely to do in addressing or solving the problem. In addition 
it would dramatically increase the complexity of the issues before EPA.
    The context for this endangerment finding is a time span of several 
decades into the future. It involves a wide variety of differing health 
and welfare effects, and almost every sector in our society. This 
somewhat unique context tends to amplify the differences between the 
two different approaches. It also means that it is hard to cleanly 
implement either approach. For example, it is hard under the first 
approach to clearly separate impacts with and without adaption, given 
the nature of the scientific studies and information before us. Under 
the second approach it would be extremely hard to make a reasoned 
projection of human and societal adaptation and mitigation responses, 
because these are basically not scientific or technical judgments, but 
are largely political judgments for society or individual personal 
judgments.
    However, the context for this endangerment finding does not change 
the fact that at their core the two different approaches are aimed at 
answering different questions. The first approach is focused on 
answering the question of what are the risks to public health and 
welfare from the air pollution if we do not take action to address it. 
The second approach is focused on answering the question of how much 
risk will remain assuming some projection of how people and society 
will respond.
    EPA believes that it is appropriate and reasonable to interpret CAA 
section 202(a) as calling for the first approach. The structure of CAA 
section 202(a) and the various other similar provisions indicate an 
intention by Congress to separate the question of what is the problem 
we need to address from the question of what is the appropriate way to 
address it. The first approach is clearly more consistent with this 
statutory structure. The amount of reduction in risk that might be 
achieved through adaptation and/or mitigation is closely related to the 
way to address a problem, and is not focused on what is the problem 
that needs to be addressed. It helps gauge the likelihood of success in 
addressing a problem, and how good a job society may do in reducing 
risk; it is not at all as useful in determining the severity of the 
problem that needs to be addressed.
    The endangerment issue at its core is a decision on whether there 
is a risk to health and welfare that needs to be addressed, and the 
second approach would tend to indicate that the more likely a society 
is to solve a problem, the less likely there is a problem that needs to 
be addressed. This would mask the issue and provide a directionally 
wrong signal. Assume two different situations, both presenting the same 
serious risks to

[[Page 66514]]

public health or welfare without consideration of adaptation or 
mitigation. The more successful society is projected to be in solving 
the serious problem in the future would mean the less likely we would 
be to make an endangerment finding at the inception identifying it as a 
problem that needs to be addressed. This is much less consistent with 
the logic embodied in CAA section 202(a), which separates the issue of 
whether there is a problem from the issue of what can be done to 
successfully address it.
    In addition, the second approach would dramatically increase the 
complexity of the issues to resolve, and would do this by bringing in 
issues that are not the subject of the kind of scientific or technical 
judgments that Congress envisioned for the endangerment test. The 
legislative history indicates Congress was focused on issues of science 
and medicine, including issues at the frontiers of these fields. It 
referred to data, research resources, science and medicine, chemistry, 
biology, and statistics. There is no indication Congress envisioned 
exercising judgment on the very different types of issues involved in 
projecting the political actions likely to be taken by various local, 
State, and Federal governments, or judgments on the business or other 
decisions that are likely to be made by companies or other 
organizations, or the changes in personal behavior that may be 
occasioned by the adverse impacts of air pollution. The second approach 
would take EPA far away from the kind of judgments Congress envisioned 
for the endangerment test.

D. Geographic Scope of Impacts

    It is the Administrator's view that the primary focus of the 
vulnerability, risk, and impact assessment is the United States. As 
described in Section IV of these Findings, the Administrator gives some 
consideration to climate change effects in world regions outside of the 
United States. Given the global nature of climate change, she has also 
examined potential impacts in other regions of the world. Greenhouse 
gases, once emitted, become well mixed in the atmosphere, meaning U.S. 
emissions can affect not only the U.S. population and environment, but 
other regions of the world as well. Likewise, emissions in other 
countries can affect the United States. Furthermore, impacts in other 
regions of the world may have consequences that in turn raise 
humanitarian, trade, and national security concerns for the United 
States.
    Commenters argue that EPA does not have the authority to consider 
international effects. They contend that the burden is on EPA is to 
show endangerment based on impacts in the United States. They note that 
EPA proposed this approach, which is the only relevant issue for EPA. 
The purpose of CAA section 202(a), as the stated purpose of the CAA, 
commenters note, is to protect the quality of the nation's air 
resources and to protect the health and welfare of the U.S. population. 
Thus, they continue, international public health and welfare are not 
listed or stated, and are not encompassed by these provisions. 
Moreover, they argue that Congress addressed international impacts 
expressly in two other provisions of the CAA. They note that under CAA 
section 115, EPA considers emissions of pollutants that cause or 
contribute to air pollution that is reasonably anticipated to endanger 
public health or welfare in a foreign country, and that CAA section 
179B addresses emissions of air pollutants in foreign countries that 
interfere with attainment of a National Ambient Air Quality Standards 
(NAAQS) in the United States. Because Congress intentionally addressed 
international impacts in those provision, commenters argue that the 
absence of this direction in CAA section 202(a) means that EPA is not 
to consider international effects when assessing endangerment under 
this provision.
    Commenters fail to recognize that EPA's consideration of 
international effects is directed at evaluating their impact on the 
public health and welfare of the U.S. population. EPA is not 
considering international effects to determine whether the health and 
welfare of the public in a foreign country is endangered. Instead, 
EPA's consideration of international effects for purposes of 
determining endangerment is limited to how those international effects 
impact the health and welfare of the U.S. population.
    The Administrator looked first at impacts in the United States 
itself, and determined that these impacts are reasonably anticipated to 
endanger the public health and the welfare of the U.S. population. That 
remains the Administrator's position, and by itself supports her 
determination of endangerment. The Administrator also considered the 
effects of global climate change outside the borders of the United 
States and evaluated them to determine whether these international 
effects impact the U.S. population, and if so whether it impacts the 
U.S. population in a manner that supports or does not support 
endangerment to the health and welfare of the U.S. public. She is not 
evaluating international effects to determine whether populations in a 
foreign country are endangered. The Administrator is looking at 
international effects solely for the purpose of evaluating their 
effects on the U.S. population.
    For example, the U.S. population can be impacted by effects in 
other countries. These international effects can impact U.S. economic, 
trade, and humanitarian and national security interests. These would be 
potential effects on the U.S. population, brought about by the effects 
of climate change occurring outside the United States. It is fully 
reasonable and rational to expect that events occurring outside our 
borders can affect the U.S. population.
    Thus, commenters misunderstand the role that international effects 
played in the proposal. The Administrator is not evaluating the impact 
of international effects on populations outside the United States; she 
is considering what impact these international effects could have on 
the U.S. population. That is fully consistent with the CAA's stated 
purpose of protecting the health and welfare of this nation's 
population.

E. Temporal Scope of Impacts

    An additional parameter of the endangerment analysis is the 
timeframe. The Administrator's view is that the timeframe over which 
vulnerabilities, risks, and impacts are considered should be consistent 
with the timeframe over which greenhouse gases, once emitted, have an 
effect on climate. Thus the relevant time frame is decades to centuries 
for the primary greenhouse gases of concern. Therefore, in addition to 
reviewing recent observations, the underlying science upon which the 
Administrator is basing her findings generally considers the next 
several decades--the time period out to around 2100, and for certain 
impacts, the time period beyond 2100. How the accumulation of 
atmospheric greenhouse gases and resultant climate change may affect 
current and future generations is discussed in section IV in these 
Findings. By current generations we mean a near-term time frame of 
approximately the next 10 to 20 years; by future generations we mean a 
longer-term time frame extending beyond that. Some public comments were 
received that questioned making an endangerment finding based on 
current conditions, while others questioned EPA's ability to make an 
endangerment finding based on future projected conditions. Some of 
these comments are likewise addressed in Section IV in these Findings; 
and all comments on these temporal issues are addressed in the Response 
to Comments document.

[[Page 66515]]

F. Impacts of Potential Future Regulations and Processes That Generate 
Greenhouse Gas Emissions

    This action is a stand-alone set of findings regarding endangerment 
and cause or contribute for greenhouse gases under CAA section 202(a), 
and does not contain any regulatory requirements. Therefore, this 
action does not attempt to assess the impacts of any future regulation. 
Although EPA would evaluate any future proposed regulation, many 
commenters argue that such a regulatory analysis should be part of the 
endangerment analysis.
    Numerous commenters argue that EPA must fully consider the adverse 
and beneficial impacts of regulation together with the impacts of 
inaction, and describe this balancing as ``risk-risk analysis,'' 
``health-health analysis,'' and most predominantly ``risk tradeoff 
analysis.'' Commenters argue that EPA's final endangerment finding 
would be arbitrary unless EPA undertakes this type of risk trade-off 
analysis.
    Commenters specifically argue that EPA must consider the economic 
impact of regulation, including the Prevention of Significant 
Deterioration (PSD) permitting program for major stationary sources 
because it is triggered by a CAA section 202(a) standard, when 
assessing whether there is endangerment to public welfare. In other 
words, they argue that the Administrator should determine if finding 
endangerment and regulating greenhouse gases under the CAA would be 
worse for public health and welfare than not regulating. Commenters 
also argue that the reference to ``public'' health or welfare in CAA 
section 202, as well as the fact that impacts on the economy should be 
considered impacts to welfare, especially requires EPA to consider the 
full range of possible impacts of regulation. Commenters provide 
various predictions regarding how regulating greenhouse gases under the 
CAA more broadly will impact the public, industry, states the overall 
economy, and thus, they conclude, public health and welfare. Examples 
of commenters' predictions include potential adverse impacts on (1) the 
housing industry and the availability of affordable housing, (2) jobs 
and income due to industry moving overseas, (3) the agriculture 
industry and its ability to provide affordable food, and (4) the 
nation's energy supply. They also cite to the letter from the Office of 
Management and Budget provided with the ANPR, as well as interagency 
comments on the draft Proposed Findings, in support of their argument.
    At least one commenter argues that EPA fails to discuss the public 
health or welfare benefits of the processes that produce the emissions. 
The commenter contends that for purposes of CAA section 202(a), this 
process would be the combustion of gasoline or other transportation 
fuel in new motor vehicles, and that for purposes of other CAA 
provisions with similar endangerment finding triggers, the processes 
would be the combustion of fossil fuel for electric generation and 
other activities. The commenter continues that EPA's decision to limit 
its analysis to the perceived detrimental aspects of emissions after 
they enter the atmosphere--as opposed to the possible positive aspects 
of emissions because of the processes that create the emissions--is 
based on EPA's overly narrow interpretation of both the meaning of the 
term ``emission'' in CAA section 202(a) (and therefore in other 
endangerment finding provisions) and the intent of these provisions. 
The commenter states that logically, it makes little sense to limit the 
definition of the term ``emission'' to only the ``air pollutants'' that 
are emitted. The commenter concludes that when EPA assesses whether the 
emission of greenhouse gases endanger public health and welfare, EPA 
must assess the dangers and benefits on both sides of the point where 
the emissions occur: in the atmosphere where the emissions lodge and, 
on the other side of the emitting stack or structure, in the processes 
that create the emissions. Otherwise, EPA will not be able to 
accurately assess whether the fact that society emits greenhouse gases 
is a benefit or a detriment. The commenter states that because 
greenhouse gas emissions, particularly carbon dioxide emissions, are so 
closely tied with all facets of modern life, a finding that greenhouse 
gas emissions endanger public health and welfare is akin to saying that 
modern life endangers public health or welfare. The commenter states 
that simply cannot be true because the lack of industrial activity that 
causes greenhouse gas emissions would pose other, almost certainly more 
serious health and welfare consequences.
    Finally, some commenters argue that the impact of regulating under 
CAA section 202(a) supports making a final, negative endangerment 
finding. These commenters contend that the incredible costs associated 
with using the inflexible regulatory structure of the CAA will harm 
public health and welfare, and therefore EPA should exercise its 
discretion and find that greenhouse gases do not endanger public health 
and welfare because once EPA makes an endangerment finding under CAA 
section 202(a), it will be forced to regulate greenhouse gases under a 
number of other sections of the CAA, resulting in regulatory chaos.
    At their core, these comments are not about whether commenters 
believe greenhouse gases may reasonably be anticipated to endanger 
public health or welfare, but rather about commenters' dissatisfaction 
with the decisions that Congress made regarding the response to any 
endangerment finding that EPA makes under CAA section 202(a). These 
comments do not discuss the science of greenhouse gases or climate 
change, or the impacts of climate change on public health or welfare. 
Instead they muddle the rather straightforward scientific judgment 
about whether there may be endangerment by throwing the potential 
impact of responding to the danger into the initial question. To use an 
analogy, the question of whether the cure is worse than the illness is 
different than the question of whether there is an illness in the first 
place. The question of whether there is endangerment is like the 
question of whether there is an illness. Once one knows there is an 
illness, then the next question is what to do, if anything, in response 
to that illness.
    What these comments object to is that Congress has already made 
some decisions about next steps after a finding of endangerment, and 
commenters are displeased with the results. But if this is the case, 
commenters should take up their concerns with Congress, not EPA. EPA's 
charge is to issue new motor vehicle standards under CAA section 202(a) 
applicable to emissions of air pollutants that cause or contribute to 
air pollution which may reasonably be anticipated to endanger public 
health or welfare. It is not to find that there is no endangerment in 
order to avoid issuing those standards, and dealing with any additional 
regulatory impact.
    Indeed, commenters' argument would insert policy considerations 
into the endangerment decision, an approach already rejected by the 
Supreme Court. First, as discussed in Section I.B of these Findings, in 
Massachusetts v. EPA, the court clearly indicated that the 
Administrator's decision must be a ``scientific judgment.'' 549 U.S. at 
534. She must base her decision about endangerment on the science, and 
not on policy considerations about the repercussions or impact of such 
a finding.
    Second, in considering whether the CAA allowed for economic 
considerations to play a role in the promulgation of the NAAQS, the

[[Page 66516]]

Supreme Court rejected arguments that because many more factors than 
air pollution might affect public health, EPA should consider 
compliance costs that produce health losses in setting the NAAQS. 
Whitman v. ATA, 531 U.S. at 457, 466 (2001). To be sure, the language 
in CAA section 109(b) applicable to the setting of a NAAQS is different 
than that in CAA section 202(a) regarding endangerment. But the 
concepts are similar--the NAAQS are about setting standards at a level 
requisite to protect public health (with an adequate margin of safety) 
and public welfare, and endangerment is about whether the current or 
projected future levels may reasonably be anticipated to endanger 
public health or welfare. In other words, both decisions essentially 
are based on assessing the harm associated with a certain level of air 
pollution.
    Given this similarity in purpose, as well as the Court's 
instructions in Massachusetts v. EPA that the Administrator should base 
her decision on the science, EPA reasonably interprets the statutory 
endangerment language to be analogous to setting the NAAQS. Therefore, 
it is reasonable to interpret the endangerment test as not requiring 
the consideration of the impacts of implementing the statute in the 
event of an endangerment finding as part of the endangerment finding 
itself.\16\
---------------------------------------------------------------------------

    \16\ Indeed, some persons may argue that due to the similarities 
between setting a NAAQS and making an endangerment finding, EPA 
cannot consider the impacts of implementation of the statute.
---------------------------------------------------------------------------

    Moreover, EPA does not believe that the impact of regulation under 
the CAA as a whole, let alone that which will result from this 
particular endangerment finding, will lead to the panoply of adverse 
consequences that commenters predict. EPA has the ability to fashion a 
reasonable and common-sense approach to address greenhouse gas 
emissions and climate change. The Administrator thinks that EPA has and 
will continue to take a measured approach to address greenhouse gas 
emissions. For example, the Agency's recent Mandatory Greenhouse Gas 
Reporting Rule focuses on only the largest sources of greenhouse gases 
in order to reduce the burden on smaller facilities.\17\
---------------------------------------------------------------------------

    \17\ Note that it is EPA's current position that these Final 
Findings do not make well-mixed greenhouse gases ``subject to 
regulation'' for purposes of the CAA's Prevention of Significant 
Deterioration (PSD) and title V programs. See, e.g., memorandum 
entitled ``EPA's Interpretation of Regulations that Determine 
Pollutants Covered By Federal Prevention of Significant 
Deterioration (PSD) Permit Program'' (Dec. 18, 2008). While EPA is 
reconsidering this memorandum and is seeking public comment on the 
issues raised in it generally, including whether a final 
endangerment finding should trigger PSD, the effectiveness of the 
positions provided in the memorandum was not stayed pending that 
reconsideration. Prevention of Significant Deterioration (PSD): 
Reconsideration of Interpretation of Regulations That Determine 
Pollutants Covered by the Federal PSD Permit Program, 74 FR 515135, 
51543-44 (Oct. 7, 2009). In addition, EPA has proposed new temporary 
thresholds for greenhouse gas emissions that define when PSD and 
title V permits are required for new or existing facilities. 
Prevention of Significant Deterioration and Title V Greenhouse Gas 
Tailoring Rule (74 FR 55292, October 27, 2009). The proposed 
thresholds would ``tailor'' the permit programs to limit which 
facilities would be required to obtain PSD and title V permits. As 
noted in the preamble for the tailoring rule proposal, EPA also 
intends to evaluate ways to streamline the process for identifying 
GHG emissions control requirements and issuing permits. See the 
Response to Comments Document, Volume 11, and the Tailoring Rule, 
for more information.
---------------------------------------------------------------------------

    We also note that commenters' approach also is another version of 
the argument that EPA must consider adaptation and mitigation in the 
endangerment determination. Just as EPA should consider whether 
mitigation would reduce endangerment, commenters argue we should 
consider whether mitigation would increase endangerment. But as 
discussed previously, EPA disagrees and believes its approach better 
achieves the goals of the statute.
    Finally, EPA simply disagrees with the commenter who argues that 
because we are better off now than before the industrial revolution, 
greenhouse gases cannot be found to endanger public health or welfare. 
As the DC Circuit noted in the Ethyl decision, ``[m]an's ability to 
alter his environment has developed far more rapidly than his ability 
to foresee with certainty the effects of his alterations.'' See Ethyl 
Corp., 541 F.2d at 6. The fact that we as a society are better off now 
than 100 years ago, and that processes that produce greenhouse gases 
are a large part of this improvement, does not mean that those 
processes do not have unintended adverse impacts. It also was entirely 
reasonable for EPA to look at ``emissions'' as the pollution once it is 
emitted from the source into the air, and not also as the process that 
generates the pollution. Indeed, the definition of ``air pollutant'' 
talks in terms of substances ``emitted into or otherwise enter[ing] the 
ambient air'' (CAA section 302(g)). It is entirely appropriate for EPA 
to consider only the substance being emitted as the air pollution or 
air pollutant.

IV. The Administrator's Finding That Greenhouse Gases Endanger Public 
Health and Welfare

    The Administrator finds that elevated concentrations of greenhouse 
gases in the atmosphere may reasonably be anticipated to endanger the 
public health and to endanger the public welfare of current and future 
generations. The Administrator is making this finding specifically with 
regard to six key directly-emitted, long-lived and well-mixed 
greenhouse gases: Carbon dioxide, methane, nitrous oxide, 
hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride. The 
Administrator is making this judgment based on both current 
observations and projected risks and impacts into the future. 
Furthermore, the Administrator is basing this finding on impacts of 
climate change within the United States. However, the Administrator 
finds that when she considers the impacts on the U.S. population of 
risks and impacts occurring in other world regions, the case for 
endangerment to public health and welfare is only strengthened.

A. The Air Pollution Consists of Six Key Greenhouse Gases

    The Administrator must define the scope and nature of the relevant 
air pollution for the endangerment finding under CAA section 202(a). In 
this final action, the Administrator finds that the air pollution is 
the combined mix of six key directly-emitted, long-lived and well-mixed 
greenhouse gases (henceforth ``well-mixed greenhouse gases''), which 
together, constitute the root cause of human-induced climate change and 
the resulting impacts on public health and welfare. These six 
greenhouse gases are carbon dioxide, methane, nitrous oxide, 
hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride.
    EPA received public comments on this definition of air pollution 
from the Proposed Findings, and summarizes responses to some of those 
key comments below; fuller responses to public comments can be found in 
EPA's Response to Comments document, Volume 9. The Administrator 
acknowledges that other anthropogenic climate forcers also play a role 
in climate change. Many public comments either supported or opposed 
inclusion of other substances in addition to the six greenhouse gases 
for the definition of air pollution. EPA's responses to those comments 
are also summarized below, and in volume 9 of the Response to Comments 
document.
    The Administrator explained her rationale for defining air 
pollution under CAA section 202(a) as the combined mix of the six 
greenhouse gases in the Proposed Findings. After review of the public 
comments, the Administrator is using the same definition of the air 
pollution in the

[[Page 66517]]

final finding, for the following reasons: (1) These six greenhouse gas 
share common properties regarding their climate effects; (2) these six 
greenhouse gases have been estimated to be the primary cause of human-
induced climate change, are the best understood drivers of climate 
change, and are expected to remain the key driver of future climate 
change; (3) these six greenhouse gases are the common focus of climate 
change science research and policy analyses and discussions; (4) using 
the combined mix of these gases as the definition (versus an individual 
gas-by-gas approach) is consistent with the science, because risks and 
impacts associated with greenhouse gas-induced climate change are not 
assessed on an individual gas approach; and (5) using the combined mix 
of these gases is consistent with past EPA practice, where separate 
substances from different sources, but with common properties, may be 
treated as a class (e.g., oxides of nitrogen).
1. Common Physical Properties of the Six Greenhouse Gases
    The common physical properties relevant to the climate change 
problem shared by the six greenhouse gases include the fact that they 
are long-lived in the atmosphere. ``Long-lived'' is used here to mean 
that the gas has a lifetime in the atmosphere sufficient to become 
globally well mixed throughout the entire atmosphere, which requires a 
minimum atmospheric lifetime of about one year.\18\ Thus, this 
definition of air pollution is global in nature because the greenhouse 
gas emissions emitted from the United States (or from any other region 
of the world) become globally well mixed, such that it would not be 
meaningful to define the air pollution as the greenhouse gas 
concentrations over the United States as somehow being distinct from 
the greenhouse gas concentrations over other regions of the world.
---------------------------------------------------------------------------

    \18\ The IPCC also refers to these six GHGs as long-lived. 
Methane has an atmospheric lifetime of roughly a decade. One of the 
most commonly used hydrofluorocarbons (HFC-134a) has a lifetime of 
14 years. Nitrous oxide has a lifetime of 114 years; sulfur 
hexafluoride over 3,000 years; and some PFCs up to 10,000 to 50,000 
years. Carbon dioxide in the atmosphere is sometimes approximated as 
having a lifetime of roughly 100 years, but for a given amount of 
carbon dioxide emitted a better description is that some fraction of 
the atmospheric increase in concentration is quickly absorbed by the 
oceans and terrestrial vegetation, some fraction of the atmospheric 
increase will only slowly decrease over a number of years, and a 
small portion of the increase will remain for many centuries or 
more.
---------------------------------------------------------------------------

    It is also well established that each of these gases can exert a 
warming effect on the climate by trapping in heat that would otherwise 
escape to space. These six gases are directly emitted as greenhouse 
gases rather than forming as a greenhouse gas in the atmosphere after 
emission of a pre-cursor gas. Given these properties, the magnitude of 
the warming effect of each of these gases is generally better 
understood than other climate forcing agents that do not share these 
same properties (addressed in more detail below). The ozone-depleting 
substances that include chlorofluorocarbons (CFCs) and 
hydrochlorofluorocarbons (HFCs) also share the same physical attributes 
discussed here, but for reasons discussed throughout the remainder of 
this section are not being included in the Administrator's definition 
of air pollution for this finding.
2. Evidence That the Six Greenhouse Gases Are the Primary Driver of 
Current and Projected Climate Change
a. Key Observations Driven Primarily by the Six Greenhouse Gases
    The latest assessment of the USGCRP, as summarized in EPA's TSD, 
confirms the evidence presented in the Proposed Findings that current 
atmospheric greenhouse gas concentrations are now at elevated and 
essentially unprecedented levels as a result of both historic and 
current anthropogenic emissions. The global atmospheric carbon dioxide 
concentration has increased about 38 percent from pre-industrial levels 
to 2009, and almost all of the increase is due to anthropogenic 
emissions. The global atmospheric concentration of methane has 
increased by 149 percent since pre-industrial levels (through 2007); 
and the nitrous oxide concentration has increased 23 percent (through 
2007). The observed concentration increase in these gases can also be 
attributed primarily to anthropogenic emissions. The industrial 
fluorinated gases have relatively low concentrations, but these 
concentrations have also been increasing and are almost entirely 
anthropogenic in origin.
    Historic data show that current atmospheric concentrations of the 
two most important directly emitted, long-lived greenhouse gases 
(carbon dioxide and methane) are well above the natural range of 
atmospheric concentrations compared to at least the last 650,000 years. 
Atmospheric greenhouse gas concentrations have been increasing because 
anthropogenic emissions are outpacing the rate at which greenhouse 
gases are removed from the atmosphere by natural processes over 
timescales of decades to centuries. It also remains clear that these 
high atmospheric concentrations of greenhouse gases are the unambiguous 
result of human activities.
    Together the six well-mixed greenhouse gases constitute the largest 
anthropogenic driver of climate change.\19\ Of the total anthropogenic 
heating effect caused by the accumulation of the six well-mixed 
greenhouse gases plus other warming agents (that do not meet all of the 
Administrator's criteria that pertain to the six greenhouse gases) 
since pre-industrial times, the combined heating effect of the six 
well-mixed greenhouses is responsible for roughly 75 percent, and it is 
expected that this share may grow larger over time, as discussed below.
---------------------------------------------------------------------------

    \19\ As summarized in EPA's TSD, the global average net effect 
of the increase in atmospheric greenhouse gas concentrations, plus 
other human activities (e.g., land use change and aerosol 
emissions), on the global energy balance since 1750 has been one of 
warming. This total net heating effect, referred to as forcing, is 
estimated to be +1.6 (+0.6 to +2.4) Watts per square meter (W/
m2), with much of the range surrounding this estimate due 
to uncertainties about the cooling and warming effects of aerosols. 
The combined radiative forcing due to the cumulative (i.e., 1750 to 
2005) increase in atmospheric concentrations of CO2, 
CH4, and N2O is estimated to be +2.30 (+2.07 
to +2.53) W/m2. The rate of increase in positive 
radiative forcing due to these three GHGs during the industrial era 
is very likely to have been unprecedented in more than 10,000 years.
---------------------------------------------------------------------------

    Warming of the climate system is unequivocal, as is now evident 
from observations of increases in global average air and ocean 
temperatures, widespread melting of snow and ice, and rising global 
average sea level. Global mean surface temperatures have risen by 0.74 
[deg]C (1.3 [deg]F) (0.18 [deg]C) over the last 100 years. 
Eight of the 10 warmest years on record have occurred since 2001. 
Global mean surface temperature was higher during the last few decades 
of the 20th century than during any comparable period during the 
preceding four centuries.
    The global surface temperature record relies on three major global 
temperature datasets, developed by NOAA, NASA, and the United Kingdom's 
Hadley Center. All three show an unambiguous warming trend over the 
last 100 years, with the greatest warming occurring over the past 30 
years.\20\ Furthermore, all three datasets show that eight of the 10 
warmest years on record have occurred since 2001; that the 10 warmest 
years have all occurred in the past 12 years; and that the 20 warmest 
years have all occurred since 1981. Though most of the warmest years on 
record have occurred in the last decade in all available datasets, the 
rate of warming has, for a short time in the

[[Page 66518]]

Hadley Center record, slowed. However, the NOAA and NASA trends do not 
show the same marked slowdown for the 1999-2008 period. Year-to-year 
fluctuations in natural weather and climate patterns can produce a 
period that does not follow the long-term trend. Thus, each year may 
not necessarily be warmer than every year before it, though the long-
term warming trend continues.\21\
---------------------------------------------------------------------------

    \20\ See section 4 of the TSD for more detailed information 
about the three global temperature datasets.
    \21\ Karl T. et al., (2009).
---------------------------------------------------------------------------

    The scientific evidence is compelling that elevated concentrations 
of heat-trapping greenhouse gases are the root cause of recently 
observed climate change. The IPCC conclusion from 2007 has been re-
confirmed by the June 2009 USGCRP assessment that most of the observed 
increase in global average temperatures since the mid-20th century is 
very likely \22\ due to the observed increase in anthropogenic 
greenhouse gas concentrations. Climate model simulations suggest 
natural forcing alone (e.g., changes in solar irradiance) cannot 
explain the observed warming.
---------------------------------------------------------------------------

    \22\ The IPCC Fourth Assessment Report uses specific terminology 
to convey likelihood and confidence. Likelihood refers to a 
probability that the statement is correct or that something will 
occur. ``Virtually certain'' conveys greater than 99 percent 
probability of occurrence; ``very likely'' 90 to 99 percent; 
``likely'' 66 to 90 percent. IPCC assigns confidence levels as to 
the correctness of a statement. ``Very high confidence'' conveys at 
least 9 out of 10 chance of being correct; ``high confidence'' about 
8 out of 10 chance; ``medium confidence'' about 5 out of 10 chance. 
The USGCRP uses the same or similar terminology in its reports. See 
also Box 1.2 of the TSD. Throughout this document, this terminology 
is used in conjunction with statements from the IPCC and USGCRP 
reports to convey the same meaning that those reports intended. In 
instances where a word such as ``likely'' may appear outside the 
context of a specific IPCC or USGCRP statement, it is not meant to 
necessarily convey the same quantitative meaning as the IPCC 
terminology.
---------------------------------------------------------------------------

    The attribution of observed climate change to anthropogenic 
activities is based on multiple lines of evidence. The first line of 
evidence arises from our basic physical understanding of the effects of 
changing concentrations of greenhouse gases, natural factors, and other 
human impacts on the climate system. The second line of evidence arises 
from indirect, historical estimates of past climate changes that 
suggest that the changes in global surface temperature over the last 
several decades are unusual.\23\ The third line of evidence arises from 
the use of computer-based climate models to simulate the likely 
patterns of response of the climate system to different forcing 
mechanisms (both natural and anthropogenic).
---------------------------------------------------------------------------

    \23\ Karl T. et al. (2009).
---------------------------------------------------------------------------

    The claim that natural internal variability or known natural 
external forcings can explain most (more than half) of the observed 
global warming of the past 50 years is inconsistent with the vast 
majority of the scientific literature, which has been synthesized in 
several assessment reports. Based on analyses of widespread temperature 
increases throughout the climate system and changes in other climate 
variables, the IPCC has reached the following conclusions about 
external climate forcing: ``It is extremely unlikely (<5 percent) that 
the global pattern of warming during the past half century can be 
explained without external forcing, and very unlikely that it is due to 
known natural external causes alone'' (Hegerl et al., 2007). With 
respect to internal variability, the IPCC reports the following: ``The 
simultaneous increase in energy content of all the major components of 
the climate system as well as the magnitude and pattern of warming 
within and across the different components supports the conclusion that 
the cause of the [20th century] warming is extremely unlikely (<5 
percent) to be the result of internal processes'' (Hegerl et al., 
2007). As noted in the TSD, the observed warming can only be reproduced 
with models that contain both natural and anthropogenic forcings, and 
the warming of the past half century has taken place at a time when 
known natural forcing factors alone (solar activity and volcanoes) 
would likely have produced cooling, not warming.
    United States temperatures also warmed during the 20th and into the 
21st century; temperatures are now approximately 0.7 [deg]C (1.3 
[deg]F) warmer than at the start of the 20th century, with an increased 
rate of warming over the past 30 years. Both the IPCC and CCSP reports 
attributed recent North American warming to elevated greenhouse gas 
concentrations. The CCSP (2008g) report finds that for North America, 
``more than half of this warming [for the period 1951-2006] is likely 
the result of human-caused greenhouse gas forcing of climate change.''
    Observations show that changes are occurring in the amount, 
intensity, frequency, and type of precipitation. Over the contiguous 
United States, total annual precipitation increased by 6.1 percent from 
1901-2008. It is likely that there have been increases in the number of 
heavy precipitation events within many land regions, even in those 
where there has been a reduction in total precipitation amount, 
consistent with a warming climate.
    There is strong evidence that global sea level gradually rose in 
the 20th century and is currently rising at an increased rate. It is 
very likely that the response to anthropogenic forcing contributed to 
sea level rise during the latter half of the 20th century. It is not 
clear whether the increasing rate of sea level rise is a reflection of 
short-term variability or an increase in the longer-term trend. Nearly 
all of the Atlantic Ocean shows sea level rise during the last 50 years 
with the rate of rise reaching a maximum (over 2 mm per year) in a band 
along the U.S. east coast running east-northeast.
    Satellite data since 1979 show that annual average Arctic sea ice 
extent has shrunk by 4.1 percent per decade. The size and speed of 
recent Arctic summer sea ice loss is highly anomalous relative to the 
previous few thousands of years.
    Widespread changes in extreme temperatures have been observed in 
the last 50 years across all world regions including the United States. 
Cold days, cold nights, and frost have become less frequent, while hot 
days, hot nights, and heat waves have become more frequent.
    Observational evidence from all continents and most oceans shows 
that many natural systems are being affected by regional climate 
changes, particularly temperature increases. However, directly 
attributing specific regional changes in climate to emissions of 
greenhouse gases from human activities is difficult, especially for 
precipitation.
    Ocean carbon dioxide uptake has lowered the average ocean pH 
(increased the acidity) level by approximately 0.1 since 1750. 
Consequences for marine ecosystems may include reduced calcification by 
shell-forming organisms, and in the longer term, the dissolution of 
carbonate sediments.
    Observations show that climate change is currently affecting U.S. 
physical and biological systems in significant ways. The consistency of 
these observed changes in physical and biological systems and the 
observed significant warming likely cannot be explained entirely due to 
natural variability or other confounding non-climate factors.
b. Key Projections Based Primarily on Future Scenarios of the Six 
Greenhouse Gases
    There continues to be no reason to expect that, without substantial 
and near-term efforts to significantly reduce emissions, atmospheric 
levels of greenhouse gases will not continue to climb, and thus lead to 
ever greater rates of climate change. Given the long atmospheric 
lifetime of the six greenhouse gases, which range from roughly a decade 
to centuries, future atmospheric greenhouse gas

[[Page 66519]]

concentrations for the remainder of this century and beyond will be 
influenced not only by future emissions but indeed by present-day and 
near-term emissions. Consideration of future plausible scenarios, and 
how our current greenhouse gas emissions essentially commit present and 
future generations to cope with an altered atmosphere and climate, 
reinforces the Administrator's judgment that it is appropriate to 
define the combination of the six key greenhouse gases as the air 
pollution.
    Most future scenarios that assume no explicit greenhouse gas 
mitigation actions (beyond those already enacted) project increasing 
global greenhouse gas emissions over the century, which in turn result 
in climbing greenhouse gas concentrations. Under the range of future 
emission scenarios evaluated by the assessment literature, carbon 
dioxide is expected to remain the dominant anthropogenic greenhouse 
gas, and thus driver of climate change, over the course of the 21st 
century. In fact, carbon dioxide is projected to be the largest 
contributor to total radiative forcing in all periods and the radiative 
forcing associated with carbon dioxide is projected to be the fastest 
growing. For the year 2030, projections of the six greenhouse gases 
show an increase of 25 to 90 percent compared with 2000 emissions. 
Concentrations of carbon dioxide and the other well-mixed gases 
increase even for those scenarios where annual emissions toward the end 
of the century are assumed to be lower than current annual emissions. 
The radiative forcing associated with the non-carbon dioxide well-mixed 
greenhouse gases is still important and increasing over time. Emissions 
of the ozone-depleting substances are projected to continue decreasing 
due to the phase-out schedule under the Montreal Protocol on Substances 
that Deplete the Ozone Layer. Considerable uncertainties surround the 
estimates and future projections of anthropogenic aerosols; future 
atmospheric concentrations of aerosols, and thus their respective 
heating or cooling effects, will depend much more on assumptions about 
future emissions because of their short atmospheric lifetimes compared 
to the six well-mixed greenhouse gases.
    Future warming over the course of the 21st century, even under 
scenarios of low emissions growth, is very likely to be greater than 
observed warming over the past century. According to climate model 
simulations summarized by the IPCC, through about 2030, the global 
warming rate is affected little by the choice of different future 
emission scenarios. By the end of the century, projected average global 
warming (compared to average temperature around 1990) varies 
significantly depending on emissions scenario and climate sensitivity 
assumptions, ranging from 1.8 to 4.0 [deg]C (3.2 to 7.2 [deg]F), with 
an uncertainty range of 1.1 to 6.4 [deg]C (2.0 to 11.5 [deg]F).
    All of the United States is very likely to warm during this 
century, and most areas of the United States are expected to warm by 
more than the global average. The largest warming is projected to occur 
in winter over northern parts of Alaska. In western, central and 
eastern regions of North America, the projected warming has less 
seasonal variation and is not as large, especially near the coast, 
consistent with less warming over the oceans.
3. The Six Greenhouse Gases Are Currently the Common Focus of the 
Climate Change Science and Policy Communities
    The well-mixed greenhouse gases are currently the common focus of 
climate science and policy analyses and discussions. For example, the 
United Nations Framework Convention on Climate Change (UNFCCC), signed 
and ratified by the United States in 1992, requires its signatories to 
``develop, periodically update, publish and make available * * * 
national inventories of anthropogenic emissions by sources and removals 
by sinks of all greenhouse gases not controlled by the Montreal 
Protocol, using comparable methodologies * * *'' 24 25 To 
date, the focus of UNFCCC actions and discussions has been on the six 
greenhouse gases that are the same focus of these Findings.
---------------------------------------------------------------------------

    \24\ Due to the cumulative purpose of the statutory language, 
even if the Administrator were to look at the atmospheric 
concentration of each greenhouse gas individually, she would still 
consider the impact of the concentration of a single greenhouse gas 
in combination with that caused by the other greenhouse gases.
    \25\ The range of uncertainty in the current magnitude of black 
carbon's climate forcing effect is evidenced by the ranges presented 
by the IPCC Fourth Assessment Report (2007) and the more recent 
study by Ramanathan, V. and Carmichael, G. (2008) Global and 
regional climate changes due to black carbon. Nature Geoscience, 
1(4): 221-227.
---------------------------------------------------------------------------

    Because of these common properties, it has also become common 
practice to compare these gases on a carbon dioxide equivalent basis, 
based on each gas's warming effect relative to carbon dioxide (the 
designated reference gas) over a specified timeframe. For example, both 
the annual Inventory of U.S. Greenhouse Gases and Sinks published by 
EPA and the recently finalized EPA Mandatory Greenhouse Gas Reporting 
Rule (74 FR 56260), use the carbon dioxide equivalent metric to sum and 
compare these gases, and thus accept the common climate-relevant 
properties of these gases for their treatment as a group. This is also 
common practice internationally as the UNFCCC reporting guidelines for 
developed countries, and the Clean Development Mechanism procedures for 
developing countries both require the use of global warming potentials 
published by the IPCC to convert the six greenhouse gases into their 
respective carbon dioxide equivalent units.
4. Defining Air Pollution as the Aggregate Group of Six Greenhouse 
Gases Is Consistent With Evaluation of Risks and Impacts Due to Human-
Induced Climate Change
    Because the well-mixed greenhouse gases are collectively the 
primary driver of current and projected human-induced climate change, 
all current and future risks due to human-induced climate change--
whether these risks are associated with increases in temperature, 
changes in precipitation, a rise in sea levels, changes in the 
frequency and intensity of weather events, or more directly with the 
elevated greenhouse gas concentrations themselves--can be associated 
with this definition of air pollution.
5. Defining the Air Pollution as the Aggregate Group of Six Greenhouse 
Gases Is Consistent With Past EPA Practice
    Treating the air pollution as the aggregate of the well-mixed 
greenhouse gases is consistent with other provisions of the CAA and 
previous EPA practice under the CAA, where separate emissions from 
different sources but with common properties may be treated as a class 
(e.g., particulate matter (PM)). This approach addresses the total, 
cumulative effect that the elevated concentrations of the six well-
mixed greenhouse gases have on climate, and thus on different elements 
of health, society and the environment.\24\
    EPA treats, for example, PM as a common class of air pollution; PM 
is a complex mixture of extremely small particles and liquid droplets. 
Particle pollution is made up of a number of components, including 
acids (such as nitrates and sulfates), organic chemicals, metals, and 
soil or dust particles.
6. Other Climate Forcers Not Being Included in the Definition of Air 
Pollution for This Finding
    Though the well-mixed greenhouse gases that make up the definition 
of air pollution for purposes of making the endangerment decision under 
CAA section 202(a) constitute the primary

[[Page 66520]]

driver of human-induced climate change, there are other substances 
emitted from human activities that contribute to climate change and 
deserve careful attention, but are not being included in the air 
pollution definition for this particular action. These substances are 
discussed immediately below.
a. Black Carbon
    Several commenters request that black carbon be included in the 
definition of air pollution because of its warming effect on the 
climate. Black carbon is not a greenhouse gas, rather, it is an aerosol 
particle that results from the incomplete combustion of carbon 
contained in fossil fuels and biomass, and remains in the atmosphere 
for only about a week. Unlike any of the greenhouse gases being 
addressed by this action, black carbon is a component of particulate 
matter (PM), where PM is a criteria air pollutant under section 108 of 
the CAA. The extent to which black carbon makes up total PM varies by 
emission source, where, for example, diesel vehicle PM emissions 
contain a higher fraction of black carbon compared to most other PM 
emission sources. Black carbon causes a warming effect primarily by 
absorbing incoming and reflected sunlight (whereas greenhouse gases 
cause warming by trapping outgoing, infrared heat), and by darkening 
bright surfaces such as snow and ice, which reduces reflectivity. This 
latter effect, in particular, has been raising concerns about the role 
black carbon may be playing in observed warming and ice melt in the 
Arctic.
    As stated in the April 2009 Proposed Findings, there remain some 
significant scientific uncertainties about black carbon's total climate 
effect,\25\ as well as concerns about how to treat the short-lived 
black carbon emissions alongside the long-lived, well-mixed greenhouse 
gases in a common framework (e.g., what are the appropriate metrics to 
compare the warming and/or climate effects of the different substances, 
given that, unlike greenhouse gases, the magnitude of aerosol effects 
can vary immensely with location and season of emissions). 
Nevertheless, the Administrator recognizes that black carbon is an 
important climate forcing agent and takes very seriously the emerging 
science on black carbon's contribution to global climate change in 
general and the high rates of observed climate change in the Arctic in 
particular. As noted in the Proposed Findings, EPA has various pending 
petitions under the CAA calling on the Agency to make an endangerment 
finding and regulate black carbon emissions.
b. Other Climate Forcers
    There are other climate forcers that play a role in human-induced 
climate change that were mentioned in the Proposed Findings, and were 
the subject of some public comments. These include the stratospheric 
ozone-depleting substances, nitrogen trifluoride (NF3), 
water vapor, and tropospheric ozone.
    As mentioned above, the ozone-depleting substances (CFCs and HCFCs) 
do share the same physical, climate-relevant attributes as the six 
well-mixed greenhouse gases; however, emissions of these substances are 
playing a diminishing role in human-induced climate change. They are 
being controlled and phased out under the Montreal Protocol on 
Substances that Deplete the Ozone Layer. Because of this, the major 
scientific assessment reports such as those from IPCC focus primarily 
on the same six well-mixed greenhouse gases included in the definition 
of air pollution in these Findings. It is also worth noting that the 
UNFCCC, to which the United States is a signatory, addresses ``all 
greenhouse gases not controlled by the Montreal Protocol.'' \26\ One 
commenter noted that because the Montreal Protocol controls production 
and consumption of ozone-depleting substances, but not existing banks 
of the substances, that CFCs should be included in the definition of 
air pollution in this finding, which might, in turn, create some future 
action under the CAA to address the banks of ozone-depleting substances 
as a climate issue. However, the primary criteria for defining the air 
pollution in this finding is the focus on the core of the climate 
change problem, and concerns over future actions to control depletion 
of stratospheric ozone are separate from and not central to the air 
pollution causing climate change.
---------------------------------------------------------------------------

    \26\ UNFCCC, Art. 4.1(b).
---------------------------------------------------------------------------

    Nitrogen trifluoride also shares the same climate-relevant 
attributes as the six well-mixed greenhouse gases, and it is also 
included in EPA's Mandatory Greenhouse Gas Reporting Rule (FR 74 
56260). However, the Administrator is maintaining the reasoning laid 
out in the Proposed Findings to not include NF3 in the 
definition of air pollution for this finding because the overall 
magnitude of its forcing effect on climate is not yet well quantified. 
EPA will continue to track the science on NF3.
    A number of public comments question the exclusion of water vapor 
from the definition of air pollution because it is the most important 
greenhouse gas responsible for the natural, background greenhouse 
effect. The Administrator's reasoning for excluding water vapor, was 
described in the Proposed Findings and is summarized here with 
additional information in Volume 10 of the Response to Comments 
document. First, climate change is being driven by the buildup in the 
atmosphere of greenhouse gases. The direct emissions primarily 
responsible for this are the six well-mixed greenhouse gases. Direct 
anthropogenic emissions of water vapor, in general, have a negligible 
effect and are thus not considered a primary driver of human-induced 
climate change. EPA plans to further evaluate the issues of emissions 
of water that are implicated in the formation of contrails and also 
changes in water vapor due to local irrigation. At this time, however, 
the findings of the IPCC state that the total forcing from these 
sources is small and that the level of understanding is low.
    Water produced as a byproduct of combustion at low altitudes has a 
negligible contribution to climate change. The residence time of water 
vapor is very short (days) and the water content of the air in the long 
term is a function of temperature and partial pressure, with emissions 
playing no role. Additionally, the radiative forcing of a given mass of 
water at low altitudes is much less than the same mass of carbon 
dioxide. Water produced at higher altitudes could potentially have a 
larger impact. The IPCC estimated the contribution of changes in 
stratospheric water vapor due to methane and other sources, as well as 
high altitude contributions from contrails, but concluded that both 
contributions were small, with a low level of understanding. The report 
also addressed anthropogenic contributions to water vapor arising from 
large scale irrigation, but assigned it a very low level of 
understanding, and suggested that the cooling from evaporation might 
outweigh the warming from its small radiative contribution.
    Increases in tropospheric ozone concentrations have exerted a 
significant anthropogenic warming effect since pre-industrial times. 
However, as explained in the Proposed Findings, tropospheric ozone is 
not a long-lived, well-mixed greenhouse gas, and it is not directly 
emitted. Rather it forms in the atmosphere from emissions of pre-cursor 
gases. There is increasing attention in climate change research and the 
policy community about the extent to which further reductions in 
tropospheric ozone levels may help

[[Page 66521]]

slow down climate change in the near term. The Administrator views this 
issue seriously but maintains that tropospheric ozone is sufficiently 
different such that it deserves an evaluation and treatment separate 
from this finding.
7. Summary of Key Comments on Definition of Air Pollution
a. It Is Reasonable for the Administrator To Define the Air Pollution 
as Global Concentrations of the Well-Mixed Greenhouse Gases
    Many commenters argue that EPA does not have the authority to 
establish domestic rights and obligations based on environmental 
conditions that are largely attributed to foreign nations and entities 
that are outside the jurisdiction of EPA under the CAA. They contend 
that in this case, the bulk of emissions that would lead to mandatory 
emissions controls under the CAA would not and could not be regulated 
under the CAA. They state that CAA requirements cannot be enforced 
against foreign sources of air pollution, and likewise domestic 
obligations under the CAA cannot be caused by foreign emissions that 
are outside the United States. The commenters argue that EPA committed 
procedural error by not addressing this legal issue of authority in the 
proposal.
    Commenters cite no statutory text or judicial authority for this 
argument, and instead rely entirely on an analogy to the issues 
concerning the exercise of extra-territorial jurisdiction. The text of 
CAA section 202(a), however, does not support this claim. Nothing in 
CAA section 202(a) limits the term air pollution to those air pollution 
matters that are caused solely or in large part by domestic emissions. 
The only issue under CAA section 202(a) is whether the air pollution is 
reasonably anticipated to endanger, and whether emissions from one 
domestic source category--new motor vehicles--cause or contribute to 
this air pollution. Commenters would read into this an additional cause 
or contribute test--whether foreign sources cause or contribute to the 
air pollution in such a way that the air pollution is largely 
attributable to the foreign emissions, or the bulk of emissions causing 
the air pollution are from foreign sources. There is no such provision 
in CAA section 202(a). Congress was explicit about the contribution 
test it imposed, and the only source that is relevant for purposes of 
contribution is new motor vehicles. Commenters suggest an ill-defined 
criterion that is not in the statute.
    In addition, as discussed in Section II of these Findings, Congress 
intentionally meant the agency to judge the air pollution endangerment 
criteria based on the ``cumulative impact of all sources of a 
pollutant,'' and not an incremental look at just the endangerment from 
a subset of sources. Commenters' arguments appear to lead to this 
result. Under the commenters' approach, in those cases where the bulk 
of emissions which form the air pollution come from foreign sources, 
EPA apparently would have no authority to make an endangerment finding. 
Logically, EPA would be left with the option of identifying and 
evaluating the air pollution attributable to domestic sources alone, 
and determining whether that narrowly defined form of air pollution 
endangers public health or welfare. This is the kind of unworkable, 
incremental approach that was rejected by the court in Ethyl and by 
Congress in the 1977 amendments adopting this provision.
    The analogy to extra-territorial jurisdiction is also not 
appropriate. The endangerment finding itself does not exercise 
jurisdiction over any source, domestic or foreign. It is a judgment 
that is a precondition for exercising regulatory authority. Under CAA 
section 202(a), any exercise of regulatory authority following from 
this endangerment finding would be for new motor vehicles either 
manufactured in the United States or imported into the United States. 
There would be no extra-territorial exercise of jurisdiction. The core 
issues for endangerment focus on impacts inside the United States, not 
outside the United States. In addition, the contribution finding is 
based solely on the contribution from new motor vehicles built in or 
imported to the United States. The core judgments that need to be made 
under CAA section 202(a) are all focused on actions and impacts inside 
the United States. This does not raise any concerns about an extra-
territorial exercise of jurisdiction. The basis for the endangerment 
and contribution findings is fully consistent with the principles 
underlying the desire to avoid exercises of extra-territorial 
jurisdiction. Any limitations on the ability to exercise control over 
foreign sources of emissions does not, however, call into question the 
authority under CAA section 202 to exercise control over domestic 
sources of emissions based on their contribution to an air pollution 
problem that is judged to endanger public health or welfare based on 
impacts occurring in the United States or otherwise affecting the 
United States and its citizens.
    In essence, commenters are concerned about the effectiveness of the 
domestic control strategies that can be adopted to address a global air 
pollution problem that is caused only in part by domestic sources of 
emissions. While that is a quite valid and important policy concern, it 
does not translate into a legal limitation on EPA's authority to make 
an endangerment finding. Neither the text nor the legislative history 
of CAA section 202(a) support such an interpretation and Congress 
explicitly separated the decision on endangerment from the decision on 
what controls are required or appropriate once an affirmative 
endangerment finding has been made. The effectiveness of the resulting 
regulatory controls is not a relevant factor to determining 
endangerment.
    EPA also committed no procedural flaw as argued by commenters. The 
proposal fully explored the interpretation of endangerment and cause or 
contribution under CAA section 202(a), and was very clear that EPA was 
considering air pollution to mean the elevated global concentration of 
greenhouse gases in the atmosphere, recognizing that these atmospheric 
concentrations were the result of world wide emissions, not just or 
even largely U.S. emissions. The separation of the effectiveness of the 
control strategy from the endangerment criteria, and the need to 
consider the cumulative impact of all sources in evaluating 
endangerment was clearly discussed. Commenters received fair notice of 
EPA's proposal and the basis for it.
    Similarly, some commenters argue that EPA's proposal defines air 
pollution as global air pollution, but EPA is limited to evaluating 
domestic air only; in other words that EPA may only regulate domestic 
emissions with localized effects. They argue this limitation derives 
from the purpose of the CAA--to enhance the quality of the Nation's air 
resources, recognizing that air pollution prevention and control focus 
on the sources of the emissions, and are the primary responsibility of 
States and local governments. Therefore, commenters continue, that 
``air pollution'' has to be air pollution that originates domestically 
and is to be addressed only at the domestic source. Sections 115 and 
179B of the CAA, as discussed below, reflect this intention as well. 
The result, they conclude, is that ``air pollution'' as used in CAA 
section 202(a), includes only pollution that originates domestically, 
where the effects occur locally. They argue EPA has improperly 
circumvented this by a ``local-global-local'' analysis that injects

[[Page 66522]]

global air pollution into the middle of the endangerment test.
    The statutory arguments made by the commenters attempt to read an 
unrealistic limitation into the general provisions discussed. The 
issues are similar in nature to those raised by the commenters arguing 
that EPA has no authority to establish domestic rights and obligations 
based on environmental conditions that are largely attributable to 
emissions from foreign nations and entities that are outside the 
jurisdiction of EPA under the CAA. In both cases, the question is 
whether EPA has authority to make an endangerment finding when the air 
pollution of concern is a relatively homogenous atmospheric 
concentration of greenhouse gases. According to the commenters, 
although this global pool includes the air over the United States, and 
leads to impacts in the United States and on the U.S. population, 
Congress prohibited EPA from addressing this air pollution problem 
because of its global aspects.
    The text of the CAA does not specifically address this, as the term 
air pollution is not defined. EPA interprets this term as including the 
air pollution problem involved in this case--elevated atmospheric 
concentration of greenhouse gases that occur in the air above the 
United States as well as across the globe, and where this pool of 
global gases leads to impacts in the United States and on the U.S. 
population. This is fully consistent with the statutory provisions 
discussed by commenters. This approach seeks to protect the Nation's 
air resources, as clearly the Nation's air resources are an integral 
part of this global pool. The Nation's air resources by definition are 
not an isolated atmosphere that only contains molecules emitted within 
the United States, or an atmosphere that bears no relationship to the 
rest of the globe's atmosphere. There is no such real world body of 
air. Protecting the Nation's resources of clean air means to protect 
the air in the real world, not an artificial construct of ``air'' that 
ignores the many situations where the air over our borders includes 
compounds and pollutants emitted outside our borders, and in this case 
to ignore the fact that the air over our borders will by definition 
have elevated concentrations of greenhouse gases only when the air 
around the globe also has such concentrations. The suggested narrow 
view of ``air pollution'' does not further the protection of the 
Nation's air resources, but instead attempts to limit such protection 
by defining these resources in a scientifically artificial way that 
does not comport with how the air in the atmosphere is formed or 
changes over time, how it relates to and interacts with air around the 
globe, and how the result of this can affect the U.S. population.
    The approach suggested by commenters fails to provide an actual 
definition for EPA to follow--for example, would U.S. or domestic ``air 
pollution'' be limited to only those air concentrations composed of 
molecules that originated in the United States? Is there a degree of 
external gases or compounds that could be allowed? Would it ignore the 
interaction and relationship between the air over the U.S. borders and 
the air around the rest of the globe? The latter approach appears to be 
the one suggested by commenters. Commenters' approach presumably would 
call for EPA to only consider the effects that derive solely from the 
air over our borders, and to ignore any effects that occur within the 
United States that are caused by air around the globe. However the air 
over the United States will by definition affect climate change only in 
circumstances where the air around the world is also doing so. The 
impacts of the air over the United States cannot be assessed separately 
from the impacts from the global pool, as they occur together and work 
together to affect the climate. Ignoring the real world nature of the 
Nation's air resources, in the manner presumably suggested by the 
commenters, would involve the kind of unworkable, incremental, and 
artificially isolating approach that was rejected by the court in Ethyl 
and by Congress in 1977. Congress intended EPA to interpret this 
provision by looking at air pollutants and air pollution problems in a 
broad manner, not narrowly, to evaluate problems within their broader 
context and not to attempt to isolate matters in an artificial way that 
fails to account for the real world context that lead to health and 
welfare impacts on the public. Commenters' suggested interpretation 
fails to implement this intention of Congress.
    Commenters in various places refer to the control of the pollution, 
and the need for it to be aimed at local sources. That is addressed in 
the standard setting portion of CAA section 202(a), as in other similar 
provisions. The endangerment provision does not address how the air 
pollution problem should be addressed--who should be regulated and how 
they should be regulated. The endangerment provision addresses a 
different issue--is there an air pollution problem that should be 
addressed? In that context, EPA rejects the artificially narrow 
interpretation suggested by the commenters, and believes its broader 
interpretation in this case is reasonable and consistent with the 
intention of Congress.
b. Consideration of Greenhouse Gases as Air Pollution Given Their 
Impact Is Through Climate Rather Than Direct Toxic Effects
    A number of commenters argue that carbon dioxide and the other 
greenhouse gases should not be defined as the air pollution because 
these gases do not cause direct human health effects, such as through 
inhalation. Responses to such comments are summarized in Section IV.B.1 
of these Findings in the discussion of the public health and welfare 
nature of the endangerment finding.
c. The Administrator's Reliance on the Global Temperature Data Is a 
Reasonable Indicator of Human-Induced Climate Change
    We received many comments suggesting global temperatures have 
stopped warming. The commenters base this conclusion on temperature 
trends over only the last decade. While there have not been strong 
trends over the last seven to ten years in global surface temperature 
or lower troposphere temperatures measured by satellites, this pause in 
warming should not be interpreted as a sign that the Earth is cooling 
or that the science supporting continued warming is in error. Year-to-
year variability in natural weather and climate patterns make it 
impossible to draw any conclusions about whether the climate system is 
warming or cooling from such a limited analysis. Historical data 
indicate short-term trends in long-term time series occasionally run 
counter to the overall trend. All three major global surface 
temperature records show a continuation of long-term warming. Over the 
last century, the global average temperature has warmed at the rate of 
about 0.13 [deg]F (0.072 [deg]C) per decade in all three records. Over 
the last 30 years, the global average surface temperature has warmed by 
about 0.30 [deg]F (0.17 [deg]C) per decade. Eight of the 10 warmest 
years on record have occurred since 2001 and the 20 warmest years have 
all occurred since 1981. Satellite measurements of the troposphere also 
indicate warming over the last 30 years at a rate of 0.20 to 0.27 
[deg]F (0.11 [deg]C to 0.15 [deg]C) per decade. Please see the relevant 
volume of the Response to Comments document for more detailed 
responses.
    Some commenters indicate the global surface temperature records are 
biased by urbanization, poor siting of instruments, observation 
methods, and

[[Page 66523]]

other factors. Our review of the literature suggests that these biases 
have in many cases been corrected for, are largely random where they 
remain, and therefore cancel out over large regions. Furthermore, we 
note that though the three global surface temperature records use 
differing techniques to analyze much of the same data, they produce 
almost the same results, increasing our confidence in their legitimacy. 
The assessment literature has concluded that warming of the climate 
system is unequivocal. The warming trend that is evident in all of the 
temperature records is confirmed by other independent observations, 
such as the melting of Arctic sea ice, the retreat of mountain glaciers 
on every continent, reductions in the extent of snow cover, earlier 
blooming of plants in the spring, and increased melting of the 
Greenland and Antarctic ice sheets. Please see the relevant volume of 
the Response to Comments document for more detailed responses.
    A number of commenters argue that the warmth of the late 20th 
century is not unusual relative to the past 1,000 years. They maintain 
temperatures were comparably warm during the Medieval Warm Period (MWP) 
centered around 1000 A.D. We agree there was a Medieval Warm Period in 
many regions but find the evidence is insufficient to assess whether it 
was globally coherent. Our review of the available evidence suggests 
that Northern Hemisphere temperatures in the MWP were probably between 
0.1 [deg]C and 0.2 [deg]C below the 1961-1990 mean and significantly 
below the level shown by instrumental data after 1980. However, we note 
significant uncertainty in the temperature record prior to 1600 A.D. 
Please see the relevant volume of the Response to Comments document for 
more detailed responses.
d. Ability To Attribute Observed Climate Change to Anthropogenic, Well-
Mixed Greenhouse Gases
    Many commenters question the link between observed temperatures and 
anthropogenic greenhouse gas emissions. They suggest internal 
variability of the climate system and natural forcings explain observed 
temperature trends and that anthropogenic greenhouse gases play, at 
most, a minor role. However, the attribution of most of the recent 
warming to anthropogenic activities is based on multiple lines of 
evidence. The first line of evidence arises from our basic physical 
understanding of the effects of changing concentrations of greenhouse 
gases, natural factors, and other human impacts on the climate system. 
Greenhouse gas concentrations have indisputably increased and their 
radiative properties are well established. The second line of evidence 
arises from indirect, historical estimates of past climate changes that 
suggest that the changes in global surface temperature over the last 
several decades are unusual. The third line of evidence arises from the 
use of computer-based climate models to simulate the likely patterns of 
response of the climate system to different forcing mechanisms (both 
natural and anthropogenic). These models are unable to replicate the 
observed warming unless anthropogenic emissions of greenhouse gases are 
included in the simulations. Natural forcing alone cannot explain the 
observed warming. In fact, the assessment literature \27\ indicates the 
sum of solar and volcanic forcing in the past half century would likely 
have produced cooling, not warming. Please see the relevant volume of 
the Response to Comments for more detailed responses.
---------------------------------------------------------------------------

    \27\ Solomon, S., D. Qin, M. Manning, R.B. Alley, T. Berntsen, 
N.L. Bindoff, Z. Chen, A. Chidthaisong, J.M. Gregory, G.C. Hegerl, 
M. Heimann, B. Hewitson, B.J. Hoskins, F. Joos, J. Jouzel, V. 
Kattsov, U. Lohmann, T. Matsuno, M. Molina, N. Nicholls, J. 
Overpeck, G. Raga, V. Ramaswamy, J. Ren, M. Rusticucci, R. 
Somerville, T.F. Stocker, P. Whetton, R.A. Wood and D. Wratt (2007) 
Technical Summary. In: Climate Change 2007: The Physical Science 
Basis. Contribution of Working Group I to the Fourth Assessment 
Report of the Intergovernmental Panel on Climate Change [Solomon, 
S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, 
and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, 
United Kingdom and New York, NY, USA. Karl, T. et al. (2009).
---------------------------------------------------------------------------

B. The Air Pollution Is Reasonably Anticipated To Endanger Both Public 
Health and Welfare

    The Administrator finds that the elevated atmospheric 
concentrations of the well-mixed greenhouse gases may reasonably be 
anticipated to endanger the public health and welfare of current and 
future generations. This section describes the major pieces of 
scientific evidence supporting the Administrator's endangerment 
finding, discusses both the public health and welfare nature of the 
endangerment finding, and addresses a number of key issues the 
Administrator considered when evaluating the state of the science as 
well as key public comments on the Proposed Findings. Additional detail 
can be found in the TSD and the Response to Comments document.
    As described in Section II of these Findings, the endangerment test 
under CAA section 202(a) does not require the Administrator to identify 
a bright line, quantitative threshold above which a positive 
endangerment finding can be made. The statutory language explicitly 
calls upon the Administrator to use her judgment. This section 
describes the general approach used by the Administrator in reaching 
the judgment that a positive endangerment finding should be made, as 
well as the specific rationale for finding that the greenhouse gas air 
pollution may reasonably be anticipated to endanger both public health 
and welfare.
    First, the Administrator finds the scientific evidence linking 
human emissions and resulting elevated atmospheric concentrations of 
the six well-mixed greenhouse gases to observed global and regional 
temperature increases and other climate changes to be sufficiently 
robust and compelling. This evidence is briefly explained in more 
detail in Section V of these Findings. The Administrator recognizes 
that the climate change associated with elevated atmospheric 
concentrations of carbon dioxide and the other well-mixed greenhouse 
gases have the potential to affect essentially every aspect of human 
health, society and the natural environment. The Administrator is 
therefore not limiting her consideration of potential risks and impacts 
associated with human emissions of greenhouse gases to any one 
particular element of human health, sector of the economy, region of 
the country, or to any one particular aspect of the natural 
environment. Rather, the Administrator is basing her finding on the 
total weight of scientific evidence, and what the science has to say 
regarding the nature and potential magnitude of the risks and impacts 
across all climate-sensitive elements of public health and welfare, now 
and projected out into the foreseeable future.
    The Administrator has considered the state of the science on how 
human emissions and the resulting elevated atmospheric concentrations 
of well-mixed greenhouse gases may affect each of the major risk 
categories, i.e., those that are described in the TSD, which include 
human health, air quality, food production and agriculture, forestry, 
water resources, sea level rise and coastal areas, the energy sector, 
infrastructure and settlements, and ecosystems and wildlife. The 
Administrator understands that the nature and potential severity of 
impacts can vary across these different elements of public health and 
welfare, and that they can vary by region, as well as over time.
    The Administrator is therefore aware that, because human-induced 
climate change has the potential to be far-reaching and multi-
dimensional, not all

[[Page 66524]]

risks and potential impacts can be characterized with a uniform level 
of quantification or understanding, nor can they be characterized with 
uniform metrics. Given this variety in not only the nature and 
potential magnitude of risks and impacts, but also in our ability to 
characterize, quantify and project into the future such impacts, the 
Administrator must use her judgment to weigh the threat in each of the 
risk categories, weigh the potential benefits where relevant, and 
ultimately judge whether these risks and benefits, when viewed in 
total, are judged to be endangerment to public health and/or welfare.
    This has a number of implications for the Administrator's approach 
in assessing the nature and magnitude of risk and impacts across each 
of the risk categories. First, the Administrator has not established a 
specific threshold metric for each category of risk and impacts. Also, 
the Administrator is not necessarily placing the greatest weight on 
those risks and impacts which have been the subject of the most study 
or quantification.
    Part of the variation in risks and impacts is the fact that 
climbing atmospheric concentrations of greenhouse gases and associated 
temperature increases can bring about some potential benefits to public 
health and welfare in addition to adverse risks. The current 
understanding of any potential benefits associated with human-induced 
climate change is described in the TSD and is taken into consideration 
here. The potential for both adverse and beneficial effects are 
considered, as well as the relative magnitude of such effects, to the 
extent that the relative magnitudes can be quantified or characterized. 
Furthermore, given the multiple ways in which the buildup of 
atmospheric greenhouse gases can cause effects (e.g., via elevated 
carbon dioxide concentrations, via temperature increases, via 
precipitation increases, via sea level rise, and via changes in extreme 
events), these multiple pathways are considered. For example, elevated 
carbon dioxide concentrations may be beneficial to crop yields, but 
changes in temperature and precipitation may be adverse and must also 
be considered. Likewise, modest temperature increases may have some 
public health benefits as well as harms, and other pathways such as 
changes in air quality and extreme events must also be considered.
    The Administrator has balanced and weighed the varying risks and 
effects for each sector. She has judged whether there is a pattern 
across the sector that supports or does not support an endangerment 
finding, and if so whether the support is of more or less weight. In 
cases where there is both a potential for benefits and risks of harm, 
the Administrator has balanced these factors by determining whether 
there appears to be any directional trend in the overall evidence that 
would support placing more weight on one than the other, taking into 
consideration all that is known about the likelihood of the various 
risks and effects and their seriousness. In all of these cases, the 
judgment is largely qualitative in nature, and is not reducible to 
precise metrics or quantification.
    Regarding the timeframe for the endangerment test, it is the 
Administrator's view that both current and future conditions must be 
considered. The Administrator is thus taking the view that the 
endangerment period of analysis extend from the current time to the 
next several decades, and in some cases to the end of this century. 
This consideration is also consistent with the timeframes used in the 
underlying scientific assessments. The future timeframe under 
consideration is consistent with the atmospheric lifetime and climate 
effects of the six well-mixed greenhouse gases, and also with our 
ability to make reasonable and plausible projections of future 
conditions.
    The Administrator acknowledges that some aspects of climate change 
science and the projected impacts are more certain than others. Our 
state of knowledge is strongest for recently observed, large-scale 
changes. Uncertainty tends to increase in characterizing changes at 
smaller (regional) scales relative to large (global) scales. 
Uncertainty also increases as the temporal scales move away from 
present, either backward, but more importantly forward in time. 
Nonetheless, the current state of knowledge of observed and past 
climate changes and their causes enables projections of plausible 
future changes under different scenarios of anthropogenic forcing for a 
range of spatial and temporal scales.
    In some cases, where the level of sensitivity to climate of a 
particular sector has been extensively studied, future impacts can be 
quantified whereas in other instances only a qualitative description of 
a directional change, if that, may be possible. The inherent 
uncertainty in the direction, magnitude, and/or rate of certain future 
climate change impacts opens up the possibility that some changes could 
be more or less severe than expected, and the possibility of 
unanticipated outcomes. In some cases, low probability, high impact 
outcomes (i.e., known unknowns) are possibilities but cannot be 
explicitly assessed.
1. The Air Pollution Is Reasonably Anticipated To Endanger Public 
Health
    The Administrator finds that the well-mixed greenhouse gas air 
pollution is reasonably anticipated to endanger public health, for both 
current and future generations. The Administrator finds that the public 
health of current generations is endangered and that the threat to 
public health for both current and future generations will likely mount 
over time as greenhouse gases continue to accumulate in the atmosphere 
and result in ever greater rates of climate change.
    After review of public comments, the Administrator continues to 
believe that climate change can increase the risk of morbidity and 
mortality and that these public health impacts can and should be 
considered when determining endangerment to public health under CAA 
section 202(a). As described in Section IV.B.1 of these Findings, the 
Administrator is not limited to only considering whether there are any 
direct health effects such as respiratory or toxic effects associated 
with exposure to greenhouse gases.
    In making this public health finding, the Administrator considered 
direct temperature effects, air quality effects, the potential for 
changes in vector-borne diseases, and the potential for changes in the 
severity and frequency of extreme weather events. In addition, the 
Administrator considered whether and how susceptible populations may be 
particularly at risk. The current state of science on these effects 
from the major assessment reports is described in greater detail in the 
TSD, and our responses to public comments are provided in the Response 
to Comments Documents.
a. Direct Temperature Effects
    It has been estimated that unusually hot days and heat waves are 
becoming more frequent, and that unusually cold days are becoming less 
frequent, as noted above. Heat is already the leading cause of weather-
related deaths in the United States. In the future, severe heat waves 
are projected to intensify in magnitude and duration over the portions 
of the United States where these events already occur. Heat waves are 
associated with marked short-term increases in mortality. Hot 
temperatures have also been associated with increased morbidity. The 
projected warming is therefore projected to increase heat related 
mortality and

[[Page 66525]]

morbidity, especially among the elderly, young and frail. The 
populations most sensitive to hot temperatures are older adults, the 
chronically sick, the very young, city-dwellers, those taking 
medications that disrupt thermoregulation, the mentally ill, those 
lacking access to air conditioning, those working or playing outdoors, 
and socially isolated persons. As warming increases over time, these 
adverse effects would be expected to increase as the serious heat 
events become more serious.
    Increases in temperature are also expected to lead to some 
reduction in the risk of death related to extreme cold. Cold waves 
continue to pose health risks in northern latitudes in temperature 
regions where very low temperatures can be reached in a few hours and 
extend over long periods. Globally, the IPCC projects reduced human 
mortality from cold exposure through 2100. It is not clear whether 
reduced mortality in the United States from cold would be greater or 
less than increased heat-related mortality in the United States due to 
climate change. However, there is a risk that projections of cold-
related deaths, and the potential for decreasing their numbers due to 
warmer winters, can be overestimated unless they take into account the 
effects of season and influenza, which is not strongly associated with 
monthly winter temperature. In addition, the latest USGCRP report 
refers to a study that analyzed daily mortality and weather data in 50 
U.S. cities from 1989 to 2000 and found that, on average, cold snaps in 
the United States increased death rates by 1.6 percent, while heat 
waves triggered a 5.7 percent increase in death rates. The study 
concludes that increases in heat-related mortality due to global 
warming in the United States are unlikely to be compensated for by 
decreases in cold-related mortality.
b. Air Quality Effects
    Increases in regional ozone pollution relative to ozone levels 
without climate change are expected due to higher temperatures and 
weaker circulation in the United States relative to air quality levels 
without climate change. Climate change is expected to increase regional 
ozone pollution, with associated risks in respiratory illnesses and 
premature death. In addition to human health effects, tropospheric 
ozone has significant adverse effects on crop yields, pasture and 
forest growth, and species composition. The directional effect of 
climate change on ambient particulate matter levels remains less 
certain.
    Climate change can affect ozone by modifying emissions of 
precursors, atmospheric chemistry, and transport and removal. There is 
now consistent evidence from models and observations that 21st century 
climate change will worsen summertime surface ozone in polluted regions 
of North America compared to a future with no climate change.
    Modeling studies discussed in EPA's Interim Assessment \28\ show 
that simulated climate change causes increases in summertime ozone 
concentrations over substantial regions of the country, though this was 
not uniform, and some areas showed little change or decreases, though 
the decreases tend to be less pronounced than the increases. For those 
regions that showed climate-induced increases, the increase in maximum 
daily 8-hour average ozone concentration, a key metric for regulating 
U.S. air quality, was in the range of 2 to 8 ppb, averaged over the 
summer season. The increases were substantially greater than this 
during the peak pollution episodes that tend to occur over a number of 
days each summer. The overall effect of climate change was projected to 
increase ozone levels, compared to what would occur without this 
climate change, over broad areas of the country, especially on the 
highest ozone days and in the largest metropolitan areas with the worst 
ozone problems. Ozone decreases are projected to be less pronounced, 
and generally to be limited to some regions of the country with smaller 
population.
---------------------------------------------------------------------------

    \28\ U.S. EPA (2009) Assessment of the Impacts of Global Change 
on Regional U.S. Air Quality: A Synthesis of Climate Change Impacts 
on Ground-Level Ozone. An Interim Report of the U.S. EPA Global 
Change Research Program. U.S. Environmental Protection Agency, 
Washington, DC, EPA/600/R-07/094.
---------------------------------------------------------------------------

c. Effects on Extreme Weather Events
    In addition to the direct effects of temperature on heat- and cold-
related mortality, the Administrator considers the potential for 
increased deaths, injuries, infectious diseases, and stress-related 
disorders and other adverse effects associated with social disruption 
and migration from more frequent extreme weather. The Administrator 
notes that the vulnerability to weather disasters depends on the 
attributes of the people at risk (including where they live, age, 
income, education, and disability) and on broader social and 
environmental factors (level of disaster preparedness, health sector 
responses, and environmental degradation). The IPCC finds the following 
with regard to extreme events and human health:
    Increases in the frequency of heavy precipitation events are 
associated with increased risk of deaths and injuries as well as 
infectious, respiratory, and skin diseases. Floods are low-probability, 
high-impact events that can overwhelm physical infrastructure, human 
resilience, and social organization. Flood health impacts include 
deaths, injuries, infectious diseases, intoxications, and mental health 
problems.
    Increases in tropical cyclone intensity are linked to increases in 
the risk of deaths, injuries, waterborne and food borne diseases, as 
well as post-traumatic stress disorders. Drowning by storm surge, 
heightened by rising sea levels and more intense storms (as projected 
by IPCC), is the major killer in coastal storms where there are large 
numbers of deaths. Flooding can cause health impacts including direct 
injuries as well as increased incidence of waterborne diseases due to 
pathogens such as Cryptosporidium and Giardia.
d. Effects on Climate-Sensitive Diseases and Aeroallergens
    According to the assessment literature, there will likely be an 
increase in the spread of several food and water-borne pathogens among 
susceptible populations depending on the pathogens' survival, 
persistence, habitat range and transmission under changing climate and 
environmental conditions. Food borne diseases show some relationship 
with temperature, and the range of some zoonotic disease carriers such 
as the Lyme disease carrying tick may increase with temperature.
    Climate change, including changes in carbon dioxide concentrations, 
could impact the production, distribution, dispersion and allergenicity 
of aeroallergens and the growth and distribution of weeds, grasses, and 
trees that produce them. These changes in aeroallergens and subsequent 
human exposures could affect the prevalence and severity of allergy 
symptoms. However, the scientific literature does not provide 
definitive data or conclusions on how climate change might impact 
aeroallergens and subsequently the prevalence of allergenic illnesses 
in the United States.
    It has generally been observed that the presence of elevated carbon 
dioxide concentrations and temperatures stimulate plants to increase 
photosynthesis, biomass, water use efficiency, and reproductive effort. 
The IPCC concluded that pollens are likely to increase with elevated 
temperature and carbon dioxide.

[[Page 66526]]

e. Summary of the Administrator's Finding of Endangerment to Public 
Health
    The Administrator has considered how elevated concentrations of the 
well-mixed greenhouse gases and associated climate change affect public 
health by evaluating the risks associated with changes in air quality, 
increases in temperatures, changes in extreme weather events, increases 
in food and water borne pathogens, and changes in aeroallergens. The 
evidence concerning adverse air quality impacts provides strong and 
clear support for an endangerment finding. Increases in ambient ozone 
are expected to occur over broad areas of the country, and they are 
expected to increase serious adverse health effects in large population 
areas that are and may continue to be in nonattainment. The evaluation 
of the potential risks associated with increases in ozone in attainment 
areas also supports such a finding.
    The impact on mortality and morbidity associated with increases in 
average temperatures which increase the likelihood of heat waves also 
provides support for a public health endangerment finding. There are 
uncertainties over the net health impacts of a temperature increase due 
to decreases in cold-related mortality, but there is some recent 
evidence that suggests that the net impact on mortality is more likely 
to be adverse, in a context where heat is already the leading cause of 
weather-related deaths in the United States.
    The evidence concerning how human-induced climate change may alter 
extreme weather events also clearly supports a finding of endangerment, 
given the serious adverse impacts that can result from such events and 
the increase in risk, even if small, of the occurrence and intensity of 
events such as hurricanes and floods. Additionally, public health is 
expected to be adversely affected by an increase in the severity of 
coastal storm events due to rising sea levels.
    There is some evidence that elevated carbon dioxide concentrations 
and climate changes can lead to changes in aeroallergens that could 
increase the potential for allergenic illnesses. The evidence on 
pathogen borne disease vectors provides directional support for an 
endangerment finding. The Administrator acknowledges the many 
uncertainties in these areas. Although these adverse effects, provide 
some support for an endangerment finding, the Administrator is not 
placing primary weight on these factors.
    Finally, the Administrator places weight on the fact that certain 
groups, including children, the elderly, and the poor, are most 
vulnerable to these climate-related health effects.
f. Key Comments on the Finding of Endangerment to Public Health
    EPA received many comments on public health issues and the proposed 
finding of endangerment to public health.
i. EPA's Consideration of the Climate Impacts as Public Health Issues 
Is Reasonable
    Several commenters argue that EPA may only consider the health 
effects from direct exposure to pollutants in determining whether a 
pollutant endangers public health. The commenters state that EPA's 
proposal acknowledges that there is no evidence that greenhouse gases 
directly cause health effects, citing 74 FR 18901. To support their 
claim that EPA can only consider health effects that result from direct 
exposure to a pollutant, commenters cite several sources, discussed 
below.
    Clean Air Act and Legislative History. Several commenters argue 
that the text of the CAA and the legislative history of the 1977 
amendments demonstrate that Congress intended public health effects to 
relate to risks from direct exposure to a pollutant. They also argue 
that by considering health effects that result from welfare effects, 
EPA was essentially combining the two categories into one, contrary to 
the statute and Congressional intent.
    Commenters state that the CAA, including CAA section 202(a)(1), 
requires EPA to consider endangerment of public health separately from 
endangerment of public welfare. Commenters note that while the CAA does 
not provide a definition of public health, CAA section 302(h) addresses 
the meaning of ``welfare,'' which includes weather and climate. Thus, 
they argue, Congress has instructed that effects on weather and climate 
are to be considered as potentially endangering welfare--not human 
health. They continue that Congress surely knew that weather and 
climatic events such as flooding and heat waves could affect human 
health, but Congress nonetheless classified air pollutants' effects on 
weather and climate as effects on welfare.
    Commenters also argue that the legislative history confirms that 
Congress intended for the definition of ``public health'' to only 
include the consequences of direct human exposure to ambient air 
pollutants. They note an early version of section 109(b) would have 
required only a single NAAQS standard to protect ``public health,'' 
with the protection of ``welfare'' being a co-benefit of the single 
standard. Commenters note that the proponents of this early bill 
explained, ``[i]n many cases, a level of protection of health would 
take care of the welfare situation'' Sen. Hearing, Subcommittee on Air 
and Water Pollution, Comm. On Public Works (Mar. 17, 1970) (statement 
of Dr. Middleton, Comm'r, Nat'l Air Pollution Control Admin., HEW), 
1970 Leg. Hist. 1194. Commenters state that the Senate bill that 
ultimately passed rejected this combined standard, requiring separate 
national ambient air quality standards and national ambient air quality 
goals. Commenters contend that Congress intended that the national 
ambient air quality goals be set ``to protect the public health and 
welfare from any known or anticipated effects associated with'' air 
pollution, including the list of ``welfare'' effects currently found in 
CAA section 302(h), such as effects on water, vegetation, animals, 
wildlife, weather and climate. Commenters note the Senate Committee 
Report stated that the national ambient air quality standards were 
created to protect public health, while the national ambient air 
quality goals were intended to address broader issues because ``the 
Committee also recognizes that man's natural and man-made environment 
must be preserved and protected. Therefore, the bill provides for the 
setting of national ambient air quality goals at levels necessary to 
protect public health and welfare from any known or anticipated adverse 
effects of air pollution--including effects on soils, water, 
vegetation, man-made materials, animals, wildlife, visibility, climate, 
and economic values.'' Commenters argue this statement is clearly the 
source of the current definition of welfare effects in CAA section 
302(h), which also includes ``personal comfort and well being.'' They 
argue the Senate bill contemplated the NAAQS would include only direct 
health effects, while the goals would encompass effects on both the 
public health and welfare. Commenters continue that considering both 
public health effects and welfare effects under a combined standard, as 
the Administrator attempts to do in the proposed endangerment finding, 
would resurrect the combined approach to NAAQS that the Senate 
emphatically rejected.
    The commenters also cite language from the House Report in support 
of their view that Congress only intended that EPA consider direct 
health effects

[[Page 66527]]

when assessing endangerment to public health: ``By the words `cause or 
contribute to air pollution,' the committee intends to require the 
Administrator to consider all sources of the contaminant which 
contributes to air pollution and to consider all sources of exposure to 
the contaminant--food, water, air, etc.--in determining health risks'' 
7 H.R. Rep. No. 95-294, at 49-50 (1977). Commenters also cite language 
in the Senate Report: ``Knowledge of the relationship between the 
exposure to many air pollution agents and acute and chronic health 
effects is sufficient to develop air quality criteria related to such 
effects'' S. Rep. No. 91-1196, at 7 (1970).
    The specific issue here is whether an effect on human health that 
results from a change in climate should be considered when EPA 
determines whether the air pollution of well-mixed greenhouse gases is 
reasonably anticipated to endanger public health. In this case, the air 
pollution has an effect on climate. For example the air pollution 
raises surface, air, and water temperatures. Among the many effects 
that flow from this is the expectation that there will be an increase 
in the risk of mortality and morbidity associated with increased 
intensity of heat waves. In addition, there is an expectation that 
there will be an increase in levels of ambient ozone, leading to 
increased risk of morbidity and mortality from exposure to ozone. All 
of these are effects on human health, and all of them are associated 
with the effect on climate from elevated atmospheric concentrations of 
greenhouse gases. None of these human health effects are associated 
with direct exposure to greenhouse gases.
    In the past, EPA has not had to resolve the issue presented here, 
as it has been clear whether the effects relate to public health or 
relate to public welfare, with no confusion over what category was at 
issue. In those cases EPA has routinely looked at what effect the air 
pollution has on people. If the effect on people is to their health, we 
have considered it an issue of public health. If the effect on people 
is to their interest in matters other than health, we have considered 
it public welfare.
    For example, there are serious health risks associated with 
inhalation of ozone, and they have logically been considered as public 
health issues. Ambient levels of ozone have also raised the question of 
indirect health benefits through screening of harmful UVB rays. EPA has 
also considered this indirect health effect of ozone to be a public 
health issue.\29\ Ozone pollution also affects people by impacting 
their interests in various vegetation through foliar damage to trees, 
reduced crop yield, adverse impacts on horticultural plants, and the 
like. EPA has consistently considered these issues when evaluating the 
public welfare based NAAQS standards under CAA section 109.
---------------------------------------------------------------------------

    \29\ As discussed later, in the past EPA took the position that 
this kind of potential indirect beneficial impact on public health 
should not be considered when setting the primary health based NAAQS 
for ozone. This was not based on the view that it was not a 
potential public health impact, or that it was a public welfare 
impact instead of a public health impact. Instead EPA was 
interpreting the NAAQS standard setting provisions of section 109, 
and argued that they were intended to address only certain public 
health impacts, those that were adverse, and were not intended to 
address indirect, beneficial public health impacts. This 
interpretation of section 109 was rejected in ATA v. EPA, 175 F.3d 
1027 (1999) reh'g granted in part and denied in part, 195 F.3d 4 (DC 
Cir. 1999). The court made it clear that the potential indirect 
beneficial impact of ambient ozone on public health from screening 
UVB rays needed to be considered when setting the NAAQS to protect 
public health.
---------------------------------------------------------------------------

    In all of these situations the use of the term ``public'' has 
focused EPA on how people are affected by the air pollution. If the 
effect on people is to their health then we have considered it a public 
health issue. If the effect on people is to their interest in matters 
other than health, then we have treated it as a public welfare issue.
    The situation presented here is somewhat unique. The focus again is 
on the effect the air pollution has on people. Here the effect on 
people is to their health. However this effect flows from the change in 
climate and effects on climate are included in the definition of 
effects on welfare. That raises the issue of how to categorize the 
health effects--should we consider them when evaluating endangerment to 
public health? When we evaluate endangerment to public welfare? Or 
both?
    The text of the CAA does not resolve this question. While Congress 
defined ``effects on welfare,'' it did not define either ``public 
health'' or ``public welfare''. In addition, the definition of 
``effects on welfare'' does not clearly address how to categorize 
health effects that flow from effects on soils, water, crops, 
vegetation, weather, climate, or any of the other factors listed in CAA 
section 302(h). It is clear that effects on climate are an effect on 
welfare, but the definition does not address whether health impacts 
that are caused by these changes in climate are also effects on 
welfare. The health effects at issue are not themselves effects on 
soils, water, crops, vegetation, weather, or climate. They are instead 
effects on health. They derive from the effects on climate, but they 
are not themselves effects on climate or on anything else listed in CAA 
section 302(h). So the definition of effects on welfare does not 
address whether an effect on health, which is not itself listed in CAA 
section 302(h), is also an effect on welfare if it results from an 
effect on welfare. The text of the CAA also does not address the issue 
of direct and indirect health effects. Contrary to commenters' 
assertions, the legislative history does not address or resolve this 
issue.
    In this context, EPA is interpreting the endangerment provision in 
CAA section 202(a) as meaning that the effects on peoples' health from 
changes to climate can and should be included in EPA's evaluation of 
whether the air pollution at issue endangers public health. EPA is not 
deciding whether these health effects also could or should be 
considered in evaluating endangerment to public welfare.
    The stating of the issue makes the answer seem straightforward. If 
air pollution causes sickness or death, then these health effects 
should be considered when evaluating whether the air pollution 
endangers public health. The term public health is undefined, and by 
itself this is an eminently reasonable way to interpret it. This 
focuses on the actual effect on people, as compared to ignoring that 
and focusing on the pathway from the air pollution to the effect. The 
question then becomes whether there is a valid basis in the CAA to take 
the different approach suggested by commenters, an approach contrary to 
the common sense meaning of public health.
    Notably, the term ``public welfare'' is undefined. While it clearly 
means something other than public health, there is no obvious 
indication whether Congress intended there to be a clear boundary 
between the two terms or whether there might be some overlap where some 
impacts could be considered both a public health and a public welfare 
impact. Neither the text nor the legislative history resolves this 
issue. Under either approach, EPA believes the proper interpretation is 
that these effects on health should be considered when evaluating 
endangerment to public health.
    If we assume Congress intended that effects on public welfare could 
not include effects on public health and vice versa, then the effects 
at issue here should most reasonably be considered in the public health 
category. Indisputably they are health effects, and the plain meaning 
of the term public health would call for their inclusion in that term. 
The term public welfare is

[[Page 66528]]

undefined. If Congress intended that public welfare not include matters 
included in the public health category, then a reasonable 
interpretation of this undefined term would include those effects on 
welfare that impact people in ways other than impacting their health.
    The definition of ``effects on welfare'' does not clearly address 
how to categorize health effects that flow from effects on water, soil, 
land, climate, or weather. As noted above, the definition does not 
address whether health impacts that are caused by these changes in 
climate are also ``effects on welfare.'' Certainly effects on health 
are not included in the list in CAA section 302(h). The lack of clarity 
in the definition of effects on welfare, combined with the lack of 
definition of public welfare, do not warrant interpreting the term 
public health differently from its straightforward and common sense 
meaning.
    The inclusion of the phrase ``effects on * * * personal comfort and 
well-being'' as an effect on welfare supports this view. The term would 
logically mean something other than the different term public health. 
The term ``well-being'' is not defined, and generally has a broader and 
different connotation of positive physical, emotional, and mental 
status. The most straightforward meaning of this term, in a context 
where Congress used the different term public health in a wide variety 
of other provisions, would be to include effects on people that do not 
rise to the level of health effects, but otherwise impact their 
physical, emotional, and mental status. This gives full meaning to both 
terms.
    The term well-being is a general term, and in isolation arguably 
could include health effects. However there is no textual basis to say 
it would include some health effects but not others, as argued by 
commenters. If sickness impacts your well-being, then it impacts your 
well-being whether it results directly or indirectly from the pollution 
in the air. Nothing in CAA section 302(h) limits the term well-being to 
indirect impacts on people, or to health effects that occur because of 
other welfare effects, such as climate change. It is listed as its own 
effect on welfare. Instead of interpreting well-being as including all 
health effects, or some health effects, the much more logical way to 
interpret this provision in the context of all of the other provisions 
of the CAA is to interpret it as meaning effects on people other than 
health effects.
    Thus, if Congress intended to draw a strict line between the two 
categories of public health and public welfare, for purposes of 
determining endangerment under CAA section 202(a), then EPA believes 
that its interpretation is a reasonable and straightforward way to 
categorize the health effects at issue here. This gives weight to the 
common sense meaning of the term public health, where the terms public 
health and public welfare are undefined and the definition of effects 
on welfare is at best ambiguous on this issue.
    In the alternative, if Congress did not intend any such bright line 
between these two categories and there could be an overlap, then it is 
also reasonable for EPA to include these health effects in its 
consideration of whether the air pollution endangers public health. 
Neither approach condenses or conflates the two different terms. Under 
either approach EPA's interpretation, as demonstrated in this 
rulemaking, would still consider numerous and varied effects from 
climate change as indisputable impacts on public welfare and not 
impacts on public health. In addition, this interpretation will not 
change the fact that in almost all cases impacts on public health would 
not also be considered impacts on public welfare.
    Prior EPA actions. Several commenters argue that EPA's decision to 
include health impacts that occur because of climate change is 
inconsistent with its past approach, which has been to treat indirect 
health effects as welfare effects. Commenters contend that in the 
latest Criteria Document for ozone EPA listed tropospheric ozone's 
effects on UVB-induced human diseases, as well as its effects on 
climate change, as welfare effects, even though the agency acknowledged 
significant health effects such as sunburn and skin cancer. Commenters 
also argue that EPA listed ``risks to human health'' from toxins 
released by algal blooms due to excess nitrogen as ``ecological and 
other welfare effects'' in the recent Criteria Document for oxides of 
nitrogen and sulfur. Finally, commenters argue that EPA's proposed 
action was contrary to the Agency decision to list new municipal solid 
waste landfills as a source category under CAA section 111. Commenters 
state that EPA listed climate change as a welfare effect in that 
action, (citing 56 FR 24469).
    The Agency's recent approach regarding UVB-induced health effects 
is consistent with the endangerment findings, and demonstrates that the 
Agency considers indirect effects on human health as public health 
issues rather than public welfare issues. While the ozone Criteria 
Document may have placed the discussion of UV-B related health effects 
among chapters on welfare effects, in evaluating the evidence presented 
in the Criteria Document for purposes of preparing the policy 
assessment document, EPA staff clearly viewed UVB-induced effects as 
human health effects that were relevant in determining the public 
health based primary NAAQS for ozone, rather than welfare effects, 
regardless of which chapter in the Criteria Document described those 
effects. The evaluation of the UVB-related evidence is discussed with 
other human health effects evidence. The policy assessment document 
noted that Chapter 10 of the Criteria Document, ``provides a thorough 
analysis of the current understanding of the relationship between 
reducing tropospheric [ozone] concentrations and the potential impact 
these reductions might have on UV-B surface fluxes and indirectly 
contributing to increased UV-B related health effects.'' See, Review of 
the National Ambient Air Quality Standards for Ozone: Policy Assessment 
of Scientific and Technical Information, p 3-36 (January 2007) 
(emphasis added).
    EPA repeated this view in the 2007 proposed ozone NAAQS rule. In 
presenting its evaluation of the human health evidence for purposes of 
setting the public health based primary NAAQS, EPA stated: ``This 
section also summarizes the uncertainty about the potential indirect 
effects on public health associated with changes due to increases in 
UV-B radiation exposure, such as UV-B radiation-related skin cancers, 
that may be associated with reductions in ambient levels of ground-
level [ozone], as discussed in chapter 10 of the Criteria Document and 
chapter 3 of the Staff Paper.'' 72 FR 37818, 37827. See also, 72 FR 
37837 (``* * * the Criteria Document also assesses the potential 
indirect effects related to the presence of [ozone] in the ambient air 
by considering the role of ground-level [ozone] in mediating human 
health effects that may be directly attributable to exposure to solar 
ultraviolet radiation (UV-B).'')
    Thus, EPA's approach to UV-B related health effects clearly shows 
the Agency has treated indirect health effects not as welfare effects, 
as commenters suggest, but as human health effects that need to be 
evaluated when setting the public health based primary NAAQS. In this 
ozone NAAQS rulemaking, EPA did not draw a line between direct and 
indirect health effects for purposes of evaluating UV-B related health 
effects and the public health based primary NAAQS.

[[Page 66529]]

    Similarly, the NOX/SOX criteria document does 
not establish a precedent that indirect human health effects are 
welfare effects. Toxic algal blooms themselves are a welfare effect, so 
it is not surprising a discussion of algal blooms appears in sections 
dealing with welfare effects. The more relevant question is how EPA 
evaluated information regarding human health risks resulting from algal 
blooms. In the case of the Criteria Document, the role of nitrogen in 
causing algal blooms was unclear. As a result, the Agency did not have 
occasion to evaluate any resulting human health effects and the 
Criteria Document does not support the view that EPA treats indirect 
health effects as anything other than a public health issue.
    Finally, EPA disagrees that its action here is at odds with the 
listing of municipal solid waste landfills under CAA section 111. In 
the landfills New Source Performance Standard (NSPS) EPA did not 
consider health effects resulting from climate change much less draw 
any conclusions about health effects from climate change being health 
or welfare effects. If anything, the landfills NSPS is consistent with 
EPA's approach. In the proposed rule, EPA stated: ``The EPA has 
documented many cases of acute injury and death caused by explosions 
and fires related to municipal landfill gas emissions. In addition to 
these health effects, the associated property damage is a welfare 
effect'' (56 FR 24474). EPA considered injury and death from fires 
resulting from landfill gasses to be health effects. Yet the injury did 
not result from direct exposure to the pollutant (landfill gas). 
Instead, the injury resulted from the combustion of the pollutant--the 
injury is essentially an indirect effect of the pollutant. Yet, as with 
this action, EPA considered the injury as a human health effect.
    Case law. Several commenters argue that EPA's proposed endangerment 
finding was inconsistent with NRDC v. EPA, 902 F.2d 962 (DC Cir 1990). 
Commenters argue that in rejecting the argument that EPA must consider 
the health effects of increased unemployment that could result from a 
more stringent primary NAAQS standard, the DC Circuit explained that, 
``[i]t is only the health effects relating to pollutants in the air 
that EPA may consider.'' Id. at 973. Several commenters further argue 
that EPA later relied on that holding to defend its decision to set a 
primary NAAQS for ozone based solely on direct health effects of ozone. 
Citing, EPA Pet'n for Rehearing, Am. Trucking Ass'n v. EPA, No. 97-1440 
(DC Cir. June 28, 1999) (``ATA I'') (arguing that the primary NAAQS 
should be set through consideration of only ``direct adverse effects on 
public health, and not indirect, allegedly beneficial effects.'')
    The NRDC case is not contrary to EPA's endangerment finding. In 
NRDC, petitioner American Iron and Steel Institute argued that EPA had 
to consider the costs of health consequences that might arise from 
increased unemployment. The court ruled that, ``[c]onsideration of 
costs associated with alleged health risks from unemployment would be 
flatly inconsistent with the statute, legislative history and case law 
on this point.'' 902 F.2d at 973. The cases cited by the court in 
support of its decision all hold that EPA may not consider economic or 
technological feasibility in establishing a NAAQS. The NRDC decision 
does not establish a precedent that the CAA prohibits EPA from 
considering indirect health effects as a public health issue rather 
than a public welfare issue.
    EPA also believes reliance on the Agency's petition for rehearing 
in noted above is misplaced. In that case, EPA did not argue that 
indirect beneficial health effects were not public health issues. 
Instead EPA argued that under the CAA, it did not have to consider such 
indirect beneficial health effects of an air pollutant when setting the 
health based primary NAAQS. EPA was interpreting the NAAQS standard 
setting provisions of CAA section 109, and argued that they were 
intended to address only certain public health impacts, those that were 
adverse, and were not intended to address indirect, beneficial public 
health impacts. The issue in the case was not whether indirect health 
effects are relevant for purposes of making an endangerment decision 
concerning public health, but rather whether EPA must consider such 
beneficial health effects in establishing a primary NAAQS under CAA 
section 109. EPA's interpretation of CAA section 109 was rejected in 
ATA v. EPA, 175 F.3d at 1027 (1999) reh'g granted in part and denied in 
part, 195 F.3d at 4 (DC Cir. 1999). The court made it clear that the 
potential indirect beneficial impact of ambient ozone on public health 
from screening UVB rays needed to be considered when setting the NAAQS 
to protect public health. As discussed above, EPA has done just that as 
noted above in the UV-B context. Moreover, as discussed in Section II 
of these Findings, EPA is doing that here as well (e.g., considering 
any benefits from reduced cold weather related deaths).
ii. EPA's Treatment and Balancing of Heat- vs. Cold-Related Public 
Health Risks Was Reasonable
    A number of public commenters maintain that the risk of heat waves 
in the future will be modulated by adaptive measures. The Administrator 
is aware of the potential benefits of adaptation in reducing heat-
related morbidity and mortality and recognizes most heat-related deaths 
are preventable. Nonetheless, the Administrator notes the assessment 
literature \30\ indicates heat is the leading weather-related killer in 
the United States even though countermeasures have been employed in 
many vulnerable areas. Given projections for heat waves of greater 
frequency, magnitude, and duration coupled with a growing population of 
older adults (among the most vulnerable groups to this hazard), the 
risk of adverse health outcomes from heat waves is expected to 
increase. Intervention and response measures could certainly reduce the 
risk, but as we have noted, the need to adapt supports an increase in 
risk or endangerment. For a general discussion about EPA's treatment of 
adaptation see Section III.C of these Findings.
---------------------------------------------------------------------------

    \30\ Karl et al. (2009).
---------------------------------------------------------------------------

    Several commenters also suggest cold-related mortality will 
decrease more than heat-related mortality will increase, which 
indicates a net reduction in temperature-related mortality. Some 
commenters point to research suggesting migration to warmer climates 
has contributed to the increased longevity of some Americans, implying 
climate warming will have benefits for health. The Administrator is 
very clear that the exact balance of how heat- versus cold-related 
mortality will change in the future is uncertain; however, the 
assessment literature points to evidence suggesting that the increased 
risk from heat would exceed the decreased risk from cold in a warming 
climate. The Administrator does not dispute research indicating the 
benefits of migration to a warmer climate and nor that average climate 
warming may indeed provide health benefits in some areas. These points 
are reflected in the TSD's statement projecting less cold-related 
health effects. The Administrator considers these potential warming 
benefits independent of the potential negative effects of extreme heat 
events which are projected to increase under future climate change 
scenarios affecting vulnerable groups and communities.

[[Page 66530]]

iii. EPA Was Reasonable To Find That the Air Quality Impacts of Climate 
Change Contribute to the Endangerment of Public Health
    Several commenters suggest that air quality effects of climate 
change will be addressed through the CAA's NAAQS process, as 
implemented by the State Implementation Plans (SIP) and national 
regulatory programs. According to these commenters, these programs will 
ensure no adverse impact on public health due to climate change. Though 
climate change may cause certain air pollutant ambient concentrations 
to increase, States will continue to be compelled to meet the 
standards. So, while additional measures may be necessary, and result 
in increased costs, these commenters assert that, ultimately, public 
health will be protected by the continued existence of the NAAQS and 
therefore no endangerment with respect to this particular climate 
change-related impact will occur. One commenter states that EPA 
inappropriately assigns air quality risk to climate change that will be 
addressed through other programs. The CAA provides a mechanism to meet 
the standards and additional control measures consistent with the CAA 
will be adopted in the future, keeping pollution below unhealthy 
levels. The commenters state that the fact that NAAQS are in place that 
require EPA to fulfill its legal obligation to prevent this particular 
form of endangerment to public health.
    EPA does have in place NAAQS for ozone, which are premised on the 
harmfulness of ozone to public health and welfare. These standards and 
their accompanying regulatory regime have helped to reduce the dangers 
from ozone in the United States. However, substantial challenges remain 
with respect to achieving the air quality protection promised by the 
NAAQS for ozone. It is the Administrator's view that these challenges 
will be exacerbated by climate change.
    In addition, the control measures to achieve attainment with a 
NAAQS are a mitigation measure aimed at reducing emissions of ozone 
precursors. As discussed in Section III.C of these Findings, EPA is not 
considering the impacts of mitigation with respect to future reductions 
in emissions of greenhouse gases. For the same reasons, EPA is 
reasonably not considering mitigation in the form of the control 
measures that will need to be adopted in the future to reduce emissions 
of ozone precursors and thereby address the increased ambient ozone 
levels that can occur because of climate change.
    It is important to note that controls to meet the NAAQS are 
typically put in place only after air quality concentrations exceeding 
the standard are detected. Furthermore, implementation of controls to 
reduce ambient concentrations of pollutants occurs over an extended 
time period, ranging from three years to more than twenty years 
depending on the pollutant and the seriousness of the nonattainment 
problem. Thus, while the CAA provides mechanisms for addressing adverse 
health effects and the underlying air quality exacerbation over time, 
it will not prevent the adverse impacts in the interim. Given the 
serious nature of the health effects at issue--including respiratory 
and cardiovascular disease leading to hospital admissions, emergency 
department visits, and premature mortality--this increase in adverse 
impacts during the time before additional controls can be implemented 
is a serious public health concern. Historically, a large segment of 
the U.S. population has lived in areas exceeding the NAAQS, despite the 
CAA and its implementation efforts. Half of all Americans, 158 million 
people, live in counties where air pollution exceeds national health 
standards.\31\ Where attainment of the NAAQS is especially difficult, 
leading to delays in meeting attainment deadlines, the health effects 
of increased ozone due to climate change may be substantial.
---------------------------------------------------------------------------

    \31\ U.S. EPA (2008) National Air Quality: Status and Trends 
Through 2007. EPA-454/R-08-006, November 2008.
---------------------------------------------------------------------------

    It is also important to note that it may not be possible for States 
and Tribes to plan accurately for the impacts of climate change in 
developing control strategies for nonattainment areas. As noted in the 
TSD and EPA's 2009 Interim Assessment report (IA), climate change is 
projected to lead to an increase in the variability of weather, and 
this may increase peak pollution events including increases in ozone 
exceedances. While the modeling studies in the IA all show significant 
future changes in meteorological quantities, there is also significant 
variability across the simulations in the spatial patterns of these 
future changes, making it difficult to select a set of future 
meteorological data for planning purposes. At this time, models used to 
develop plans to attain the NAAQS do not take potential changes in 
future meteorology into consideration. Inability to predict the 
frequency and magnitude of such events could lead to an underestimation 
of the controls needed to bring areas into attainment, and a prolonged 
period during which adverse health impacts continue to occur.
    Even in areas that meet the NAAQS currently, air quality may 
deteriorate sufficiently to cause adverse health effects for some 
individuals. Some at-risk individuals, for example those with 
preexisting health conditions or other characteristics which increase 
their risk for adverse effects upon exposure to PM or ozone, may 
experience health effects at levels below the standard. Current 
evidence suggests that there is no threshold for PM or ozone 
concentrations below which no effects can be observed. Therefore, 
increases in ozone or PM in locations that currently meet the standards 
would likely result in additional adverse health effects for some 
individuals, even though the pollution increase might not be sufficient 
to cause the area to be designated nonattainment. While the NAAQS is 
set to protect public health with an adequate margin of safety, it is 
recognized that in attainment areas there may be individuals who remain 
at greater risk from an increase in ozone levels. The clear risk to the 
public from ozone increases in nonattainment areas, in combination with 
the risk to some individuals in attainment areas, supports the finding 
that overall the public health is endangered by increases in ozone 
resulting from climate change.
    Finally, it is also important to note that not all air pollution 
events are subject to CAA controls under the NAAQS implementation 
provisions. ``Exceptional events'' are events for which the normal 
planning and regulatory process established by the CAA is not 
appropriate (72 FR 13561). Emissions from some events, including some 
wildfires, are not reasonably controllable or preventable. Such 
emissions, however, can adversely impact public health and welfare and 
are expected to increase due to climate change. As described in the 
TSD, PM emissions from wildfires can contribute to acute and chronic 
illnesses of the respiratory system, particularly in children, 
including pneumonia, upper respiratory diseases, asthma and chronic 
obstructive pulmonary disease. The IPCC (Field et al., 2007) reported 
with very high confidence that in North America, disturbances like 
wildfires are increasing and are likely to intensify in a warmer future 
with drier soils and longer growing seasons.
2. The Air Pollution Is Reasonably Anticipated to Endanger Public 
Welfare
    The Administrator also finds that the well-mixed greenhouse gas air 
pollution may reasonably be anticipated to

[[Page 66531]]

endanger public welfare, both for current and future generations.
    As with public health, the Administrator considered the multiple 
pathways in which the greenhouse gas air pollution and resultant 
climate change affect climate-sensitive sectors, and the impact this 
may have on public welfare. These sectors include food production and 
agriculture; forestry; water resources; sea level rise and coastal 
areas; energy, infrastructure, and settlements; and ecosystems and 
wildlife. The Administrator also considered impacts on the U.S. 
population from climate change effects occurring outside of the United 
States, such as national security concerns for the United States that 
may arise as a result of climate change impacts in other regions of the 
world. The Administrator examined each climate-sensitive sector 
individually, informed by the summary of the scientific assessments 
contained in the TSD, and the full record before EPA, and weighed the 
extent to which the risks and impacts within each sector support or do 
not support a positive endangerment finding in her judgment. The 
Administer then viewed the full weight of evidence looking across all 
sectors to reach her decision regarding endangerment to public welfare.
a. Food Production and Agriculture
    Food production and agriculture within the United States is a 
sector that will be affected by the combined effects of elevated carbon 
dioxide concentrations and associated climate change. The Administrator 
considered how these effects, both adverse and beneficial, are 
affecting the agricultural sector now and in the future, and over 
different regions of the United States, taking into account that 
different regions of the country specialize in different agricultural 
products with varying degrees of sensitivity and vulnerability to 
elevated carbon dioxide levels and associated climate change.
    Elevated carbon dioxide concentrations can have a stimulatory 
effect on grain and oilseed crop yield, as may modest temperature 
increases and a longer growing season that results. A report under the 
USGCRP concluded that, with increased carbon dioxide and temperature, 
the life cycle of grain and oilseed crops will likely progress more 
rapidly. However, such beneficial influences need to be considered in 
light of various other effects. For example, the literature indicates 
that elevated carbon dioxide concentrations may also enhance pest and 
weed growth. Pests and weeds can reduce crop yields, cause economic 
losses to farmers, and require management control options. How climate 
change (elevated carbon dioxide, increased temperatures, altered 
precipitation patterns, and changes in the frequency and intensity of 
extreme events) may affect the prevalence of pests and weeds is an 
issue of concern for food production and the agricultural sector. 
Research on the combined effects of elevated carbon dioxide and climate 
change on pests, weeds, and disease is still limited. In addition, 
higher temperature increases, changing precipitation patterns and 
variability, and any increases in ground-level ozone induced by higher 
temperatures, can work to counteract any direct stimulatory carbon 
dioxide effect, as well as lead to their own adverse impacts. There may 
be large regional variability in the response of food production and 
agriculture to climate change.
    For grain and oilseed crop yields, there is support for the view 
that in the near term climate change may have a beneficial effect, 
largely through increased temperature and increased carbon dioxide 
levels. However there are also factors noted above, some of which are 
less well studied and understood, which would tend to offset any near 
term benefit, leaving significant uncertainty about the actual 
magnitude of any overall benefit. The USGCRP report also concluded that 
as temperature rises, these crops will increasingly begin to experience 
failure, especially if climate variability increases and precipitation 
lessens or becomes more variable.
    A key uncertainty is how human-induced climate change may affect 
the intensity and frequency of extreme weather events such as droughts 
and heavy storms. These events have the potential to have serious 
negative impact on U.S. food production and agriculture, but are not 
always taken into account in studies that examine how average 
conditions may change as a result of carbon dioxide and temperature 
increases. Changing precipitation patterns, in addition to increasing 
temperatures and longer growing seasons, can change the demand for 
irrigation requirements, potentially increasing irrigation demand.
    Another key uncertainty concerns the many horticultural crops 
(e.g., tomatoes, onions, fruits), which make up roughly 40 percent of 
total crop value in the United States. There is relatively little 
information on their response to carbon dioxide, and few crop 
simulation models, but according to the literature, they are very 
likely to be more sensitive to the various effects of climate change 
than grain and oilseed crops.
    With respect to livestock, higher temperatures will very likely 
reduce livestock production during the summer season in some areas, but 
these losses will very likely be partially offset by warmer 
temperatures during the winter season. The impact on livestock 
productivity due to increased variability in weather patterns will 
likely be far greater than effects associated with the average change 
in climatic conditions. Cold-water fisheries will likely be negatively 
affected; warm-water fisheries will generally benefit; and the results 
for cool-water fisheries will be mixed, with gains in the northern and 
losses in the southern portions of ranges.
    Finally, with respect to irrigation requirements, the adverse 
impacts of climate change on irrigation water requirements may be 
significant.
    There is support for the view that there may be a benefit in the 
near term in the crop yield for certain crops. This potential benefit 
is subject to significant uncertainty, however, given the offsetting 
impact on the yield of these crops from a variety of other climate 
change impacts that are less well understood and more variable. Any 
potential net benefit is expected to change to a disbenefit in the 
longer term. In addition, there is clear risk that the sensitivity of a 
major segment of the total crop market, the horticultural sector, may 
lead to adverse affects from climate change. With respect to livestock 
production and irrigation requirements, climate change is likely to 
have adverse effects in both the near and long terms. The impact on 
fisheries varies, and would appear to be best viewed as neutral 
overall.
    There is a potential for a net benefit in the near term for certain 
crops, but there is significant uncertainty about whether this benefit 
will be achieved given the various potential adverse impacts of climate 
change on crop yield, such as the increasing risk of extreme weather 
events. Other aspects of this sector are expected to be adversely 
affected by climate change, including livestock management and 
irrigation requirements, and there is a risk of adverse effect on a 
large segment of the total crop market. For the near term, the concern 
over the potential for adverse effects in certain parts of the 
agriculture sector appears generally comparable to the potential for 
benefits for certain crops.
    However, considering the trend over near- and long-term future 
conditions, the Administrator finds that the body of evidence points 
towards increasing risk

[[Page 66532]]

of net adverse impacts on U.S. food production and agriculture, with 
the potential for significant disruptions and crop failure in the 
future.
b. Forestry
    The factors that the Administrator considered for the U.S. forest 
sector are similar to those for food production and agriculture. There 
is the potential for beneficial effects due to elevated concentrations 
of carbon dioxide and increased temperature, as well as the potential 
for adverse effects from increasing temperatures, changing 
precipitation patterns, increased insects and disease, and the 
potential for more frequent and severe extreme weather events. The 
potential beneficial effects are better understood and studied, and are 
limited to certain areas of the country and types of forests. The 
adverse effects are less certain, more variable, and also include some 
of the most serious adverse effects such as increased wildfire, 
drought, and major losses from insects and disease. As with food 
production and agriculture, the judgment to be made is largely a 
qualitative one, balancing impacts that vary in certainty and 
magnitude, with the end result being a judgment as to the overall 
direction and general level of concern.
    According to the underlying science assessment reports, climate 
change has very likely increased the size and number of wildfires, 
insect outbreaks, and tree mortality in the Interior West, the 
Southwest, and Alaska, and will continue to do so. Rising atmospheric 
carbon dioxide levels will very likely increase photosynthesis for 
forests, but the increased photosynthesis will likely only increase 
wood production in young forests on fertile soils. Nitrogen deposition 
and warmer temperatures have very likely increased forest growth where 
water is not limiting and will continue to do so in the near future.
    An increased frequency of disturbance (such as drought, storms, 
insect-outbreaks, and wildfire) is at least as important to forest 
ecosystem function as incremental changes in temperature, 
precipitation, atmospheric carbon dioxide, nitrogen deposition, and 
ozone pollution. Disturbances partially or completely change forest 
ecosystem structure and species composition, cause short-term 
productivity and carbon storage loss, allow better opportunities for 
invasive alien species to become established, and command more public 
and management attention and resources. The combined effects of 
expected increased temperature, carbon dioxide, nitrogen deposition, 
ozone, and forest disturbance on soil processes and soil carbon storage 
remain unclear.
    Precipitation and weather extremes are key to many forestry 
impacts, accounting for part of the regional variability in forest 
response. If existing trends in precipitation continue, it is expected 
that forest productivity will likely decrease in the Interior West, the 
Southwest, eastern portions of the Southeast, and Alaska, and that 
forest productivity will likely increase in the northeastern United 
States, the Lake States, and in western portions of the Southeast. An 
increase in drought events will very likely reduce forest productivity 
wherever such events occur.
    Changes in disturbance patterns are expected to have a substantial 
impact on overall gains or losses. More prevalent wildfire disturbances 
have recently been observed in the United States. Wildfires and 
droughts, among other extreme events (e.g., hurricanes) that can cause 
forest damage, pose the largest threats over time to forest ecosystems.
    For the near term, the Administrator believes the beneficial impact 
on forest growth and productivity in certain parts of the country from 
climate change to be more than offset by the clear risk from the more 
significant and serious adverse effects from the observed increases in 
wildfires, combined with the adverse impacts on growth and productivity 
in other areas of the country and the serious risks from the spread of 
destructive pests and disease. Increased wildfires can also increase 
particulate matter and thus create public health concerns as well. For 
the longer term, the Administrator views the risk from adverse effects 
to increase over time, such that overall climate change presents 
serious adverse risks for forest productivity. The Administrator 
therefore finds there is compelling reason to find that the greenhouse 
gas air pollution endangers U.S. forestry in both the near and long 
term, with the support for a positive endangerment finding only 
increasing as one considers expected future conditions in which 
temperatures continue to rise.
c. Water Resources
    The sensitivity of water resources to climate change is very 
important given the increasing demand for adequate water supplies and 
services for agricultural, municipal, and energy and industrial uses, 
and the current strains on this resource in many parts of the country.
    According to the assessment literature, climate change has already 
altered, and will likely continue to alter, the water cycle, affecting 
where, when, and how much water is available for all uses. With higher 
temperatures, the water-holding capacity of the atmosphere and 
evaporation into the atmosphere increase, and this favors increased 
climate variability, with more intense precipitation and more droughts.
    Climate change is causing and will increasingly cause shrinking 
snowpack induced by increasing temperature. In the western United 
States, there is already well-documented evidence of shrinking snowpack 
due to warming. Earlier meltings, with increased runoff in the winter 
and early spring, increase flood concerns and also result in 
substantially decreased summer flows. This pattern of reduced snowpack 
and changes to the flow regime pose very serious risks to major 
population regions, such as California, that rely on snowmelt-dominated 
watersheds for their water supply. While increased precipitation is 
expected to increase water flow levels in some eastern areas, this may 
be tempered by increased variability in the precipitation and the 
accompanying increased risk of floods and other concerns such as water 
pollution.
    Warmer temperatures and decreasing precipitation in other parts of 
the country, such as the Southwest, can sustain and amplify drought 
impacts. Although drought has been more frequent and intense in the 
western part of the United States, the East is also vulnerable to 
droughts and attendant reductions in water supply, changes in water 
quality and ecosystem function, and challenges in allocation. The 
stress on water supplies on islands is expected to increase.
    The impact of climate change on groundwater as a water supply is 
regionally variable; efforts to offset declining surface water 
availability due to increasing precipitation variability may be 
hampered by the fact that groundwater recharge will decrease 
considerably in some already water-stressed regions. In coastal areas, 
the increased salinization from intrusion of salt water is projected to 
have negative effects on the supply of fresh water.
    Climate change is expected to have adverse effects on water 
quality. The IPCC concluded with high confidence that higher water 
temperatures, increased precipitation intensity, and longer periods of 
low flows exacerbate many forms of water pollution and can impact 
ecosystems, human health, and water system reliability and operating 
costs. These changes will also exacerbate many forms of water 
pollution, potentially making attainment of water quality goals more

[[Page 66533]]

difficult. Water pollutants of concern that are particularly relevant 
to climate change effects include sediment, nutrients, organic matter, 
pathogens, pesticides, salt, and thermal pollution. As waters become 
warmer, the aquatic life they now support will be replaced by other 
species better adapted to warmer water. In the long term, warmer water, 
changing flows, and decreased water quality may result in deterioration 
of aquatic ecosystems.
    Climate change will likely further constrain already over-allocated 
water resources in some regions of the United States, increasing 
competition among agricultural, municipal, industrial, and ecological 
uses. Although water management practices in the United States are 
generally advanced, particularly in the West, the reliance on past 
conditions as the basis for current and future planning may no longer 
be appropriate, as climate change increasingly creates conditions well 
outside of historical observations. Increased incidence of extreme 
weather and floods may also overwhelm or damage water treatment and 
management systems, resulting in water quality impairments. In the 
Great Lakes and major river systems, lower water levels are likely to 
exacerbate challenges relating to water quality, navigation, 
recreation, hydropower generation, water transfers, and bi-national 
relationships.
    The Administrator finds that the total scientific literature 
provides compelling support for finding that greenhouse gas air 
pollution endangers the water resources important for public welfare in 
the United States, both for current and future generations. The 
adequacy of water supplies across large areas of the country is at 
serious risk from climate change. Even areas of the country where an 
increase in water flow is projected could face water resource problems 
from the variability of the supply and water quality problems 
associated with precipitation variability, and could face the serious 
adverse effects from risks from floods and drought. Climate change is 
expected to adversely affect water quality. There is an increased risk 
of serious adverse effects from extreme events of flooding and drought. 
The severity of risks and impacts may only increase over time with 
accumulating greenhouse gas concentrations and associated temperature 
increases and precipitation changes.
d. Sea Level Rise and Coastal Areas
    A large percentage of the U.S. population lives in coastal areas, 
which are particularly vulnerable to the risks posed by climate change. 
The most vulnerable areas are the Atlantic and Gulf Coasts, the Pacific 
Islands, and parts of Alaska.
    According to the assessment literature, sea level is rising along 
much of the U.S. coast, and the rate of change will very likely 
increase in the future, exacerbating the impacts of progressive 
inundation, storm-surge flooding, and shoreline erosion. Cities such as 
New Orleans, Miami, and New York are particularly at risk, and could 
have difficulty coping with the sea level rise projected by the end of 
the century under a higher emissions scenario. Population growth and 
the rising value of infrastructure increases the vulnerability to 
climate variability and future climate change in coastal areas. Adverse 
impacts on islands present concerns for Hawaii and the U.S. 
territories. Reductions in Arctic sea ice increases extreme coastal 
erosion in Alaska, due to the increased exposure of the coastline to 
strong wave action. In the Great Lakes, where sea level rise is not a 
concern, both extremely high and low water levels resulting from 
changes to the hydrological cycle have been damaging and disruptive to 
shoreline communities.
    Coastal wetland loss is being observed in the United States where 
these ecosystems are squeezed between natural and artificial landward 
boundaries and rising sea levels. Up to 21 percent of the remaining 
coastal wetlands in the U.S. mid-Atlantic region are potentially at 
risk of inundation between 2000 and 2100. Coastal habitats will likely 
be increasingly stressed by climate change impacts interacting with 
development and pollution.
    Although increases in mean sea level over the 21st century and 
beyond will inundate unprotected, low-lying areas, the most devastating 
impacts are likely to be associated with storm surge. Superimposed on 
expected rates of sea level rise, projected storm intensity, wave 
height, and storm surge suggest more severe coastal flooding and 
erosion hazards. Higher sea level provides an elevated base for storm 
surges to build upon and diminishes the rate at which low-lying areas 
drain, thereby increasing the risk of flooding from rainstorms. In New 
York City and Long Island, flooding from a combination of sea level 
rise and storm surge could be several meters deep. Projections suggest 
that the return period of a 100-year flood event in this area might be 
reduced to 19-68 years, on average, by the 2050s, and to 4-60 years by 
the 2080s. Additionally, some major urban centers in the United States, 
such as areas of New Orleans are situated in low-lying flood plains, 
presenting increased risk from storm surges.
    The Administrator finds that the most serious risk of adverse 
effects is presented by the increased risk of storm surge and flooding 
in coastal areas from sea level rise. Current observations of sea level 
rise are now contributing to increased risk of storm surge and flooding 
in coastal areas, and there is reason to find that these areas are now 
endangered by human-induced climate change. The conclusion in the 
assessment literature that there is the potential for hurricanes to 
become more intense with increasing temperatures (and even some 
evidence that Atlantic hurricanes have already become more intense) 
reinforces the judgment that coastal communities are now endangered by 
human-induced climate change, and may face substantially greater risk 
in the future. The Administrator has concluded that even if there is a 
low probability of raising the destructive power of hurricanes, this 
threat is enough to support a finding that coastal communities are 
endangered by greenhouse gas air pollution.
    In addition, coastal areas face other adverse impacts from sea 
level rise such as shoreline retreat, erosion, wetland loss and other 
effects. The increased risk associated with these adverse impacts also 
endangers the welfare of current and future generations, with an 
increasing risk of greater adverse impacts in the future.
    Overall, the evidence on risk of adverse impacts for coastal areas 
from sea level rise provides clear support for finding that greenhouse 
gas air pollution endangers the welfare of current and future 
generations.
e. Energy, Infrastructure and Settlements
    The Administrator also considered the impacts of climate change on 
energy consumption and production, and on key climate-sensitive aspects 
of the nation's infrastructure and settlements.
    For the energy sector, the Administrator finds clear evidence that 
temperature increases will change heating and cooling demand, and to 
varying degrees across the country; however, under current conditions 
it is unclear whether or not net demand will increase or decrease. 
While the impacts on net energy demand may be viewed as generally 
neutral for purposes of making an endangerment determination, climate 
change is expected to call for an increase in electricity production, 
especially supply for peak demand. The U.S. energy sector, which relies 
heavily on water for cooling capacity and

[[Page 66534]]

hydropower, may be adversely impacted by changes to water supply in 
reservoirs and other water bodies.
    With respect to infrastructure, climate change vulnerabilities of 
industry, settlement and society are mainly related to extreme weather 
events rather than to gradual climate change. The significance of 
gradual climate change, e.g., increases in the mean temperature, lies 
mainly in changes in the intensity and frequency of extreme events. 
Extreme weather events could threaten U.S. energy infrastructure 
(transmission and distribution), transportation infrastructure (roads, 
bridges, airports and seaports), water infrastructure, and other built 
aspects of human settlements. Moreover, soil subsidence caused by the 
melting of permafrost in the Arctic region is a risk to gas and oil 
pipelines, electrical transmission towers, roads, and water systems. 
Vulnerabilities for industry, infrastructures, settlements, and society 
to climate change are generally greater in certain high-risk locations, 
particularly coastal and riverine areas, and areas whose economies are 
closely linked with climate-sensitive resources. Additionally, 
infrastructures are often connected, meaning that an impact on one can 
also affect others.
    A significant fraction of U.S. infrastructure is located in coastal 
areas. In these locations, rising sea levels are likely to lead to 
direct losses (e.g., equipment damage from flooding) as well as 
indirect effects such as the costs associated with raising vulnerable 
assets to higher levels. Water infrastructure, including drinking water 
and wastewater treatment plants, and sewer and storm water management 
systems, may be at greater risk of flooding, sea level rise and storm 
surge, low flows, saltwater intrusion, and other factors that could 
impair performance and damage costly investments.
    Within settlements experiencing climate change stressors, certain 
parts of the population may be especially vulnerable based on their 
circumstances. These include the poor, the elderly, the very young, 
those already in poor health, the disabled, those living alone, and/or 
indigenous populations dependent on one or a few resources. In Alaska, 
indigenous communities are likely to experience disruptive impacts, 
including shifts in the range or abundance of wild species crucial to 
their livelihoods and well-being.
    Overall, the evidence strongly supports the view that climate 
change presents risks of serious adverse impacts on public welfare from 
the risk to energy production and distribution as well as risks to 
infrastructure and settlements.
f. Ecosystems and Wildlife
    The Administrator considered the impacts of climate change on 
ecosystems and wildlife and the services they provide. The 
Administrator finds clear evidence that climate change is exerting 
major influences on natural environments and biodiversity, and these 
influences are generally expected to grow with increased warming. 
Observed changes in the life cycles of plants and animals include 
shifts in habitat ranges, timing of migration patterns, and changes in 
reproductive timing and behavior.
    The underlying assessment literature finds with high confidence 
that substantial changes in the structure and functioning of 
terrestrial ecosystems are very likely to occur with a global warming 
greater than 2 to 3 [deg]C above pre-industrial levels, with 
predominantly negative consequences for biodiversity and the 
provisioning of ecosystem goods and services. With global average 
temperature changes above 2 [deg]C, many terrestrial, freshwater, and 
marine species (particularly endemic species) are at a far greater risk 
of extinction than in the geological past. Climate change and ocean 
acidification will likely impair a wide range of planktonic and other 
marine calcifiers such as corals. Even without ocean acidification 
effects, increases in sea surface temperature of about 1-3 [deg]C are 
projected to result in more frequent coral bleaching events and 
widespread mortality. In the Arctic, wildlife faces great challenges 
from the effects of climatic warming, as projected reductions in sea 
ice will drastically shrink marine habitat for polar bears, ice-
inhabiting seals, and other animals.
    Some common forest types are projected to expand, such as oak-
hickory, while others are projected to contract, such as maple-beech-
birch. Still others, such as spruce-fir, are likely to disappear from 
the contiguous United States. Changes in plant species composition in 
response to climate change can increase ecosystem vulnerability to 
other disturbances, including wildfires and biological invasion. 
Disturbances such as wildfires and insect outbreaks are increasing in 
the United States and are likely to intensify in a warmer future with 
warmer winters, drier soils and longer growing seasons. The areal 
extent of drought-limited ecosystems is projected to increase 11 
percent per [deg]C warming in the United States. In California, 
temperature increases greater than 2 [deg]C may lead to conversion of 
shrubland into desert and grassland ecosystems and evergreen conifer 
forests into mixed deciduous forests. Greater intensity of extreme 
events may alter disturbance regimes in coastal ecosystems leading to 
changes in diversity and ecosystem functioning. Species inhabiting salt 
marshes, mangroves, and coral reefs are likely to be particularly 
vulnerable to these effects.
    The Administrator finds that the total scientific record provides 
compelling support for finding that the greenhouse gas air pollution 
leads to predominantly negative consequences for biodiversity and the 
provisioning of ecosystem goods and services for ecosystems and 
wildlife important for public welfare in the U.S., both for current and 
future generations. The severity of risks and impacts may only increase 
over time with accumulating greenhouse gas concentrations and 
associated temperature increases and precipitation changes.
g. Summary of the Administrator's Finding of Endangerment to Public 
Welfare
    The Administrator has considered how elevated concentrations of the 
well-mixed greenhouse gases and associated climate change affect public 
welfare by evaluating numerous and far-ranging risks to food production 
and agriculture, forestry, water resources, sea level rise and coastal 
areas, energy, infrastructure, and settlements, and ecosystems and 
wildlife. For each of these sectors, the evidence provides support for 
a finding of endangerment to public welfare. The evidence concerning 
adverse impacts in the areas of water resources and sea level rise and 
coastal areas provide the clearest and strongest support for an 
endangerment finding, both for current and future generations. Strong 
support is also found in the evidence concerning infrastructure and 
settlements, as well ecosystems and wildlife. Across the sectors, the 
potential serious adverse impacts of extreme events, such as wildfires, 
flooding, drought, and extreme weather conditions provide strong 
support for such a finding.
    Water resources across large areas of the country are at serious 
risk from climate change, with effects on water supplies, water 
quality, and adverse effects from extreme events such as floods and 
droughts. Even areas of the country where an increase in water flow is 
projected could face water resource problems from the supply and water 
quality problems associated with temperature increases and 
precipitation variability, and could face the increased risk of serious 
adverse effects from extreme events, such as floods and

[[Page 66535]]

drought. The severity of risks and impacts is likely to increase over 
time with accumulating greenhouse gas concentrations and associated 
temperature increases and precipitation changes.
    Overall, the evidence on risk of adverse impacts for coastal areas 
provides clear support for a finding that greenhouse gas air pollution 
endangers the welfare of current and future generations. The most 
serious potential adverse effects are the increased risk of storm surge 
and flooding in coastal areas from sea level rise and more intense 
storms. Observed sea level rise is already increasing the risk of storm 
surge and flooding in some coastal areas. The conclusion in the 
assessment literature that there is the potential for hurricanes to 
become more intense (and even some evidence that Atlantic hurricanes 
have already become more intense) reinforces the judgment that coastal 
communities are now endangered by human-induced climate change, and may 
face substantially greater risk in the future. Even if there is a low 
probability of increasing the destructive power of hurricanes, this 
threat is enough to support a finding that coastal communities are 
endangered by greenhouse gas air pollution. In addition, coastal areas 
face other adverse impacts from sea level rise such as land loss due to 
inundation, erosion, wetland submergence, and habitat loss. The 
increased risk associated with these adverse impacts also endangers 
public welfare, with an increasing risk of greater adverse impacts in 
the future.
    Strong support for an endangerment finding is also found in the 
evidence concerning energy, infrastructure, and settlements, as well 
ecosystems and wildlife. While the impacts on net energy demand may be 
viewed as generally neutral for purposes of making an endangerment 
determination, climate change is expected to result in an increase in 
electricity production, especially to meet peak demand. This increase 
may be exacerbated by the potential for adverse impacts from climate 
change on hydropower resources as well as the potential risk of serious 
adverse effects on energy infrastructure from extreme events. Changes 
in extreme weather events threaten energy, transportation, and water 
resource infrastructure. Vulnerabilities of industry, infrastructure, 
and settlements to climate change are generally greater in high-risk 
locations, particularly coastal and riverine areas, and areas whose 
economies are closely linked with climate-sensitive resources. Climate 
change will likely interact with and possibly exacerbate ongoing 
environmental change and environmental pressures in settlements, 
particularly in Alaska where indigenous communities are facing major 
environmental and cultural impacts on their historic lifestyles. Over 
the 21st century, changes in climate will cause some species to shift 
north and to higher elevations and fundamentally rearrange U.S. 
ecosystems. Differential capacities for range shifts and constraints 
from development, habitat fragmentation, invasive species, and broken 
ecological connections will likely alter ecosystem structure, function, 
and services, leading to predominantly negative consequences for 
biodiversity and the provision of ecosystem goods and services.
    With respect to food production and agriculture, there is a 
potential for a net benefit in the near term for certain crops, but 
there is significant uncertainty about whether this benefit will be 
achieved given the various potential adverse impacts of climate change 
on crop yield, such as the increasing risk of extreme weather events. 
Other aspects of this sector may be adversely affected by climate 
change, including livestock management and irrigation requirements, and 
there is a risk of adverse effect on a large segment of the total crop 
market. For the near term, the concern over the potential for adverse 
effects in certain parts of the agriculture sector appears generally 
comparable to the potential for benefits for certain crops. However, 
the body of evidence points towards increasing risk of net adverse 
impacts on U.S. food production and agriculture over time, with the 
potential for significant disruptions and crop failure in the future.
    For the near term, the Administrator finds the beneficial impact on 
forest growth and productivity in certain parts of the country from 
elevated carbon dioxide concentrations and temperature increases to 
date is offset by the clear risk from the observed increases in 
wildfires, combined with risks from the spread of destructive pests and 
disease. For the longer term, the risk from adverse effects increases 
over time, such that overall climate change presents serious adverse 
risks for forest productivity. There is compelling reason to find that 
the support for a positive endangerment finding increases as one 
considers expected future conditions where temperatures continue to 
rise.
    Looking across all of the sectors discussed above, the evidence 
provides compelling support for finding that greenhouse gas air 
pollution endangers the public welfare of both current and future 
generations. The risk and the severity of adverse impacts on public 
welfare are expected to increase over time.
h. Impacts in Other World Regions That Can Affect the U.S Population
    While the finding of endangerment to public health and welfare 
discussed above is based on impacts in the United States, the 
Administrator also considered how human-induced climate change in other 
regions of the world may in turn affect public welfare in the United 
States. According to the USGCRP report of June 2009 and other sources, 
climate change impacts in certain regions of the world may exacerbate 
problems that raise humanitarian, trade, and national security issues 
for the United States.\32\ The IPCC identifies the most vulnerable 
world regions as the Arctic, because of the effects of high rates of 
projected warming on natural systems; Africa, especially the sub-
Saharan region, because of current low adaptive capacity as well as 
climate change; small islands, due to high exposure of population and 
infrastructure to risk of sea-level rise and increased storm surge; and 
Asian mega-deltas, such as the Ganges-Brahmaputra and the Zhujiang, due 
to large populations and high exposure to sea level rise, storm surge, 
and river flooding. Climate change has been described as a potential 
threat multiplier with regard to national security issues.
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    \32\ ``In an increasingly interdependent world, U.S. 
vulnerability to climate change is linked to the fates of other 
nations. For example, conflicts or mass migrations of people 
resulting from food scarcity and other resource limits, health 
impacts or environmental stresses in other parts of the world could 
threaten U.S. national security.'' (Karl et al., 2009).
---------------------------------------------------------------------------

    The Administrator acknowledges these kinds of risks do not readily 
lend themselves to precise analyses or future projections. However, 
given the unavoidable global nature of the climate change problem, it 
is appropriate and prudent to consider how impacts in other world 
regions may present risks to the U.S. population. Because human-induced 
climate change has the potential to aggravate natural resource, trade, 
and humanitarian issues in other world regions, which in turn may 
contribute to the endangerment of public welfare in the United States, 
this provides additional support for the Administrator's finding that 
the greenhouse gas air pollution is reasonably anticipated to endanger 
the public welfare of current and future

[[Page 66536]]

generations of the United States population.
i. Summary of Key Public Comments on Endangerment to Public Welfare
    Several public commenters point out the anticipated benefits that 
increasing carbon dioxide levels and temperatures will have on 
agricultural crops. In addition, commenters note how U.S. agricultural 
productivity, in particular, has been steadily rising over the last 100 
years. Responses to major comments are found here and more detailed 
responses are found in the Response to Comments document.
    The Administrator acknowledges that plants including agricultural 
crops respond to carbon dioxide positively based on numerous well-
documented studies. However, previous assessments of food production 
and agriculture have been modified to highlight increasing 
vulnerability, stress, and adverse impacts from climate change over 
time, based on improvements in the understanding of plant physiology, 
concern over impacts on plant pests and pathogens, and the implications 
of changes in average temperatures for temperature extremes and for 
changes in the patterns of precipitation and evaporation. While it is 
still the case today and for the next few years that climate change 
benefits agriculture in some places and harms them in others, the 
Administrator considers that the far larger temperature increases 
expected over coming decades and beyond on the ``business as usual'' 
trajectory will put significant stresses on agriculture and land 
resources in all regions of the United States. The Administrator 
prudently considers increased climate variability associated with a 
warming climate, which may overwhelm the positive plant responses from 
elevated carbon dioxide over time. Further, the effects of climate 
change on weeds, insect pests, and pathogens are recognized as key 
factors in determining plant damage in future decades. The 
Administrator also notes that scientific literature clearly supports 
the finding that drought frequency and severity are projected to 
increase in the future over much of the United States, which will 
likely reduce crop yields because of excesses or deficits of water. 
Vulnerability to extended drought, according to IPCC, has been 
documented as already increasing across North America. Further, based 
on review of the assessment literature, the Administrator considers 
multiple stresses, such as limited availability of water resources, 
loss of biodiversity, and air pollution, which are likely to increase 
sensitivity and reduce resilience in the agricultural sector to climate 
change over time.
    Similar to food production and agriculture, public commenters often 
noted that forest productivity is projected to increase in the coming 
years due to the direct stimulatory effect of carbon dioxide on plant 
growth combined with warmer temperatures and thus extended growing 
seasons. The Administrator notes this phenomenon has been well 
documented by numerous studies but recognizes that increased 
productivity will be associated with significant variation at local and 
regional scales. The Administrator considers that climate strongly 
influences forest productivity and composition, and the frequency and 
magnitude of disturbances that impact forests. Based on the most recent 
IPCC assessment of the scientific literature, several recent studies 
confirm previous findings that temperature and precipitation changes in 
future decades will modify, and often limit, direct carbon dioxide 
effects on plants. For example, increased temperatures may reduce 
carbon dioxide effects indirectly, by increasing water demand. The 
Administrator also considers that new research more firmly establishes 
the negative impacts of increased climate variability. Projected 
changes in the frequency and severity of extreme climate events have 
significant consequences for forestry production and amplify existing 
stresses to land resources in the future.
    Several public commenters maintain that wildfires are primarily the 
result of natural climatic factors and not climate change and dispute 
that they are or will increase in the future. The Administrator notes 
the scientific literature and assessment reports provide several lines 
of evidence that suggest wildfires will likely increase in frequency 
over the next several decades because of climate warming. Wildfires and 
droughts, among other extreme events (e.g., hurricanes) that cause 
forest damage, pose the largest threats over time to forest ecosystems. 
The assessment literature suggests that large, stand-replacing 
wildfires will likely increase in frequency over the next several 
decades because of climate warming and general climate warming 
encourages wildfires by extending the summer period that dries fuels, 
promoting easier ignition and faster spread. Furthermore, current 
climate modeling studies suggest that increased temperatures and longer 
growing seasons will elevate wildfire risk in connection with increased 
aridity.

V. The Administrator's Finding That Emissions of Greenhouse Gases From 
CAA Section 202(a) Sources Cause or Contribute to the Endangerment of 
Public Health and Welfare

    As discussed in Section IV.A of these Findings, the Administrator 
is defining the air pollution for purposes of the endangerment finding 
to be the elevated concentration of well-mixed greenhouse gases in the 
atmosphere. The second step of the two-part endangerment test is for 
the Administrator to determine whether the emission of any air 
pollutant emitted from new motor vehicles cause or contribute to this 
air pollution. This is referred to as the cause or contribute finding, 
and is the second finding by the Administrator in this action.
    Section V.A of these Findings describes the Administrator's 
definition and scope of the air pollutant ``well-mixed greenhouse 
gases.'' Section V.B of these Findings puts forth the Administrator's 
finding that emissions of well-mixed greenhouse gases from new motor 
vehicles contribute to the air pollution which is reasonably 
anticipated to endanger public health and welfare. Section V.C of these 
Findings provides responses to some of the key comments on these 
issues. See Response to Comments document Volume 10 for responses to 
other significant comments on the cause or contribute finding. More 
detailed emissions data summarized in the discussion below can be found 
in Appendix B of the TSD.

A. The Administrator's Definition of the ``Air Pollutant''

    As discussed in the Proposed Findings, to help appreciate the 
distinction between air pollution and air pollutant, the air pollution 
can be thought of as the total, cumulative stock in the atmosphere, 
while the air pollutant, can be thought of as the flow that changes the 
size of the total stock. Given this relationship, it is not surprising 
that the Administrator is defining the air pollutant similar to the air 
pollution; while the air pollution is the concentration (e.g., stock) 
of the well-mixed greenhouse gases in the atmosphere, the air pollutant 
is the same combined grouping of the well-mixed greenhouse gases, the 
emissions of which are analyzed for contribution (e.g., the flow into 
the stock).
    Thus, the Administrator is defining the air pollutant as the 
aggregate group of the same six long-lived and directly-emitted 
greenhouse gases: Carbon dioxide, methane, nitrous oxide, 
hydrofluorocarbons, perfluorocarbons,

[[Page 66537]]

and sulfur hexafluoride. As noted above, this definition of a single 
air pollutant made up of these well-mixed greenhouse gases is similar 
to definitions of other air pollutants that are comprised of substances 
that share common attributes with similar effects on public health or 
welfare (e.g., particulate matter and volatile organic compounds).
    The common attributes shared by these six greenhouse gases are 
discussed in detail in Section IV.A of these Findings, where the 
Administrator defined the ``air pollution'' for purposes of the 
endangerment finding. These same common attributes support the 
Administrator grouping these six greenhouse gases for purposes of 
defining a single air pollutant as well. These attributes include the 
fact that they are all greenhouse gases that are directly emitted 
(i.e., they are not formed through secondary processes in the 
atmosphere from precursor emissions); they are sufficiently long-lived 
in the atmosphere such that, once emitted, concentrations of each gas 
become well mixed throughout the entire global atmosphere; and they 
exert a climate warming effect by trapping outgoing, infrared heat that 
would otherwise escape to space. Moreover, the radiative forcing effect 
of these six greenhouse gases is well understood.
    Furthermore, these six greenhouse gases are currently the common 
focus of climate science and policy. For example, the UNFCCC, signed 
and ratified by the U.S. in 1992, requires its signatories to 
``develop, periodically update, publish and make available * * * 
national inventories of anthropogenic emissions by sources and removals 
by sinks of all greenhouse gases not controlled by the Montreal 
Protocol \33\, using comparable methodologies * * * '' \34\ To date, 
the focus of UNFCCC actions and discussions has been on the six 
greenhouse gases that are the same focus of these findings. As a Party 
to the UNFCCC, EPA annually submits the Inventory of U.S. Greenhouse 
Gas Emissions and Sinks to the Convention, which reports on national 
emissions of anthropogenic emissions of the well-mixed greenhouse 
gases. International discussions about a post-Kyoto agreement also 
focus on the well-mixed greenhouse gases.
---------------------------------------------------------------------------

    \33\ The Montreal Protocol covers ozone-depleting substances 
which may also share physical attributes of the six key greenhouse 
gases in this action, but they do not share other attributes such as 
being the focus of climate science and policy. See section * * *.
    \34\ UNFCCC Art. 4.1(b).
---------------------------------------------------------------------------

    As noted above, grouping of many substances with common attributes 
as a single pollutant is common practice under the CAA. Thus, doing so 
here is not novel. Indeed CAA section 302(g) defines air pollutant as 
``any air pollutant agent or combination of such agents, * * * '' CAA 
Sec.  302(g) (emphasis added). Thus, it is clear that the term ``air 
pollutant'' is not limited to individual chemical compounds. In 
determining that greenhouse gases are within the scope of this 
definition, the Supreme Court described section 302(g) as a 
``sweeping'' and ``capacious'' definition that unambiguously included 
greenhouse gases, that are ``unquestionably `agents' of air 
pollution.'' Massachusetts v. EPA, 549 U.S. at 528, 532, 529 n.26. 
Although the Court did not interpret the term ``combination of'' air 
pollution agents, there is no reason this phrase would be interpreted 
any less broadly. Congress used the term ``any'', and did not qualify 
the kind of combinations that the agency could define as a single air 
pollutant. Congress provided EPA broad discretion to determine 
appropriate combinations of compounds that should be treated as a singe 
air pollutant.\35\
---------------------------------------------------------------------------

    \35\ Indeed, the greenhouse gases hydrofluorocarbons and 
perfluorocarbons each are already a combination of multiple 
compounds.
---------------------------------------------------------------------------

    For the same reasons discussed in Section IV.A above, at this time, 
only carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, 
perfluorocarbons, and sulfur hexafluoride share all of these common 
attributes and thus they are the only substances that the Administrator 
finds to meet the definition of ``well-mixed greenhouse gas'' at this 
time.\36\ Also as noted above, if in the future other substances are 
shown to meet the same criteria they may be added to the definition of 
this single air pollutant.
---------------------------------------------------------------------------

    \36\ The term ``well-mixed greenhouse gases'' is based on one of 
the shared attributes discussed above--these greenhouse gases are 
sufficiently long-lived in the atmosphere such that, once emitted, 
concentrations of each gas become well mixed throughout the entire 
global atmosphere. Defining the air pollutant to be the combination 
of these six well-mixed greenhouse gases is based in part on this 
attribute--after the gases are emitted, they are sufficiently long-
lived in the atmosphere to become well mixed as part of the air 
pollution.
---------------------------------------------------------------------------

    The Administrator is aware that CAA section 202(a) source 
categories do not emit all of the substances meeting the definition of 
well-mixed greenhouse gases. But that does not change the fact that all 
of these greenhouse gases share the attributes that make grouping them 
as a single air pollutant reasonable. As discussed further below, the 
reasonableness of this grouping does not turn on the particular source 
category being evaluated in a contribution finding.

B. The Administrator's Finding Regarding Whether Emissions of the Air 
Pollutant From Section 202(a) Source Categories Cause or Contribute to 
the Air Pollution That May Be Reasonably Anticipated To Endanger Public 
Health and Welfare

    The Administrator finds that emissions of the well-mixed greenhouse 
gases from new motor vehicles contribute to the air pollution that may 
reasonably be anticipated to endanger public health and welfare. This 
contribution finding is for all of the CAA section 202(a) source 
categories and the Administrator considered emissions from all of these 
source categories. The relevant mobile sources under CAA section 202 
(a)(1) are ``any class or classes of new motor vehicles or new motor 
vehicle engines, * * *.'' CAA section 202(a)(1) (emphasis added). The 
new motor vehicles and new motor vehicle engines (hereinafter ``CAA 
section 202(a) source categories'') addressed are: Passenger cars, 
light-duty trucks, motorcycles, buses, and medium and heavy-duty 
trucks. Detailed combined greenhouse gas emissions data for CAA section 
202(a) source categories are presented in Appendix B of the TSD.\37\
---------------------------------------------------------------------------

    \37\ For section 202(a) source categories, only the 
hydrofluorocarbon emissions related to passenger compartment cooling 
are included. Emissions from refrigeration units that may be 
attached to trucks are considered emissions from nonroad engines 
under CAA section 213.
---------------------------------------------------------------------------

    The Administrator reached her decision after reviewing emissions 
data on the contribution of CAA section 202(a) source categories 
relative to both global greenhouse gas emissions and U.S. greenhouse 
gas emissions. Given that CAA section 202(a) source categories are 
responsible for about 4 percent of total global greenhouse gas 
emissions, and for just over 23 percent of total U.S. greenhouse gas 
emissions, the Administrator finds that both of these comparisons, 
independently and together, support a finding that CAA section 202(a) 
source categories contribute to the air pollution that may be 
reasonably anticipated to endanger public health and welfare. The 
Administrator is not placing primary weight on either approach; rather 
she finds that both approaches clearly establish that emissions of the 
well-mixed greenhouse gases from section 202(a) source categories 
contribute to air pollution with may reasonably be anticipated to 
endanger public health and welfare. As the Supreme Court noted, 
``[j]udged by any standard, U.S.

[[Page 66538]]

motor-vehicle emissions make a meaningful contribution to greenhouse 
gas concentrations and hence, * * * to global warming.'' Massachusetts 
v. EPA, 549 U.S. at 525.\38\
---------------------------------------------------------------------------

    \38\ Because the Administrator is defining the air pollutant as 
the combination of well-mixed greenhouse gases, she is not issuing a 
final contribution finding based on the alternative definition 
discussed in the proposed findings (e.g., each greenhouse gas as an 
individual air pollutant).
---------------------------------------------------------------------------

1. Administrator's Approach in Making This Finding
    Section 202(a) of the CAA source categories consist of passenger 
cars, light-duty trucks, motorcycles, buses, and heavy- and medium-duty 
trucks. As noted in the Proposed Findings, in the past the requisite 
contribution findings have been proposed concurrently with proposing 
emission standards for the relevant mobile source category. Thus, prior 
contribution findings often focused on a subset of the CAA section 
202(a) (or other section) source categories. This final cause or 
contribute finding, however, is for all of the CAA section 202(a) 
source categories. The Administrator is considering emissions from all 
of these source categories in the determination.
    Section 202(a) source categories emit the following well-mixed 
greenhouse gases: carbon dioxide, methane, nitrous oxide, and 
hydrofluorocarbons. As the basis for the Administrator's determination, 
EPA analyzed historical data of emissions of the well-mixed greenhouse 
gases for motor vehicles and motor vehicle engines in the United States 
from 1990 to 2007.
    The Proposed Findings discussed a number of possible ways of 
assessing cause or contribute and the point was made that no single 
approach is required by the statute or has been used exclusively in 
previous determinations under the CAA. The Administrator also discussed 
how, consistent with prior cause or contribute findings and the 
science, she is using emissions as a proxy for contributions to 
atmospheric concentrations. This approach is reasonable for the well-
mixed greenhouse gases, because cumulative emissions are responsible 
for the cumulative change in the concentrations in the atmosphere. 
Similarly, annual emissions are a perfectly reasonable proxy for annual 
incremental changes in atmospheric concentrations.
    In making a judgment about the contribution of emissions from CAA 
section 202(a) source categories, the Administrator focused on making a 
reasoned overall comparison of emissions from the CAA section 202(a) 
source categories to emissions from other sources of greenhouse gases. 
This allows a determination of how the CAA section 202(a) source 
categories compare to all of the other sources that together as a group 
make up the total emissions contributors to the air pollution problem. 
The relative importance of the CAA section 202(a) source categories is 
central to making the contribution determination. Both the magnitude of 
these emissions and the comparison of these emissions to other sources 
provide the basis to determine whether the CAA section 202(a) source 
categories may reasonably be judged as contributing to the air 
pollution problem.
    In many cases EPA makes this kind of comparison of source 
categories by a simple percentage calculation that compares the 
emissions from the source category at issue to a larger total group of 
emissions. Depending on the circumstances, a larger percentage often 
means a greater relative impact from that source category compared to 
the other sources that make up the total of emissions, and vice versa. 
However, the actual numerical percentages may have little meaning when 
viewed in isolation. The context of the comparison is needed to ensure 
the information is useful in evaluating the relative impact of one 
source compared to others. For example, the number of sources involved 
and the distribution of emissions across all of the sources can make a 
significant difference when evaluating the results of a percentage 
calculation. In some cases a certain percentage might mean almost all 
other sources are larger or much larger than the source at issue, while 
in other circumstances the same percentage could mean that the source 
at issue is in fact one of the larger contributors to the total.
    The Administrator therefore considered the totality of the 
circumstances in order to best understand the role played by CAA 
section 202(a) source categories. This is consistent with Congress' 
intention for EPA to consider the cumulative impact of all sources of 
pollution. In that context, the global nature of the air pollution 
problem and the breadth of countries and sources emitting greenhouse 
gases means that no single country and no single source category 
dominate or are even close to dominating on a global scale. For 
example, the United States as a country is the second largest emitter 
of greenhouse gases, and emits approximately 18 percent of the world's 
total greenhouse gases. The total emissions of greenhouse gases 
worldwide are from numerous sources and countries, with each country 
and each source category contributing a relatively small percentage of 
the total emissions. That means that the relative ranking of countries 
or sources is not at all obvious from the magnitude of the percentage 
by itself. A country or a source may be a large contributor, in 
comparison to other countries or sources, even though its percentage 
contribution may appear relatively small.
    In this situation, addressing a global air pollution problem may 
call for many different sources and countries to address emissions even 
if none by itself dominates or comes close to dominating the global 
inventory. A somewhat analogous situation can be found in the ozone air 
pollution problem in the United States. Emissions of NOx and volatile 
organic compounds (VOCs) often come from numerous small sources, as 
well as certain large source categories. We have learned that 
successful ozone control strategies often need to take this into 
account, and address both the larger sources of NOx and VOCs as well as 
the many smaller sources, given the breadth of sources that as a group 
lead to the total inventory of VOCs and NOx.
    The global aspects of the greenhouse gas air pollution problem 
amplify this kind of situation many times over, where no single country 
or source category dominates or comes close to dominating the global 
inventory of greenhouse gas emissions. These unique, global aspects of 
the climate change problem tend to support consideration of 
contribution at lower percentage levels of emissions than might 
otherwise be considered appropriate when addressing a more typical 
local or regional air pollution problem. In this situation it is quite 
reasonable to consider emissions from source categories that are more 
important in relation to other sources, even if their absolute 
contribution initially may appear to be small.
    In addition, the Administrator is aware of the fact that the United 
States is the second largest emitter of well-mixed greenhouse gases in 
the world. As the United States evaluates how to address climate 
change, the Administrator will analyze the various sources of emissions 
and the source's share of U.S. emissions. Thus, when analyzing whether 
a source category that emits well-mixed greenhouse gases in the United 
States contributes to the global problem, it is appropriate for the 
Administrator to consider how that source category fits into the larger 
picture of U.S. emissions. This ranking process within the United 
States allows the importance of the source category to

[[Page 66539]]

be seen compared to other U.S. sources, informing the judgment of the 
importance of emissions from this source category in any overall 
national strategy to address greenhouse gas emissions.
    It is in this broader context that EPA considered the contribution 
of CAA section 202(a) sources. This provides useful information in 
determining the importance that should be attached to the emissions 
from the CAA section 202(a) sources.
    In reaching her determination, the Administrator used two simple 
and straightforward comparisons to assess cause or contribute for CAA 
section 202(a) source categories: (1) As a share of total current 
global aggregate emissions of the well-mixed greenhouse gases; and (2) 
as a share of total current U.S. aggregate emissions of the well-mixed 
greenhouse gases.
    Total well-mixed greenhouse gas emissions from CAA section 202(a) 
source categories were compared to total global emissions of the well-
mixed greenhouse gases. The total air pollution problem, as already 
discussed, is the elevated and climbing levels of the six greenhouse 
gas concentrations in the atmosphere, which are global in nature 
because these concentrations are globally well mixed (whether they are 
emitted from CAA section 202(a) source categories or any other source 
within or outside the United States). In addition, comparisons were 
also made to U.S. total well-mixed greenhouse gases emissions to 
appreciate how CAA section 202(a) source categories fit into the larger 
U.S. contribution to the global problem. It is typical for the 
Administrator to consider these kinds of comparisons of emissions of a 
pollutant in evaluating contribution to air pollution, such as the 
concentrations of that same pollutant in the atmosphere (e.g., the 
Administrator analyzes PM2.5 emissions to determine if a 
source category contributes to PM2.5 air pollution). When 
viewed in the circumstances discussed above, both of these comparisons 
provide useful information in determining whether these source 
categories should be judged as contributing to the total air pollution 
problem.
a. Section 202(a) of the CAA--Share of Global Aggregate Emissions of 
the Well-Mixed Greenhouse Gases
    Global emissions of well-mixed greenhouse gases have been 
increasing, and are projected to continue increasing unless the major 
emitters take action to reduce emissions. Total global emissions of 
well-mixed greenhouse gases in 2005 (the most recent year for which 
data for all countries and all greenhouse gases are available) \39\ 
were 38,726 teragrams of CO2-equivlant (TgCO2eq.) 
\40\ This represents an increase in global greenhouse gas emissions of 
about 26 percent since 1990 (excluding land use, land use change and 
forestry). In 2005, total U.S. emissions of well-mixed greenhouse gases 
were responsible for 18 percent of global emissions, ranking only 
behind China, which was responsible for 19 percent of global emissions 
of well-mixed greenhouse gases.
---------------------------------------------------------------------------

    \39\ The source of global greenhouse gas emissions data, against 
which comparisons are made, is the Climate Analysis Indicators Tool 
of the World Resources Institute (WRI) (2007). Note that for global 
comparisons, all emissions are from the year 2005, the most recent 
year for which data for all greenhouse gas emissions and all 
countries are available. WRI (2007) Climate Analysis Indicators Tool 
(CAIT). Available at http://cait.wri.org. Accessed August 5, 2009.
    \40\ One teragram (Tg) = 1 million metric tons. 1 metric ton = 
1,000 kg = 1.102 short tons = 2,205 lbs. Long-lived greenhouse gases 
are compared and summed together on a CO2 equivalent 
basis by multiplying each gas by its Global Warming Potential 
(GWPs), as estimated by IPCC. In accordance with UNFCCC reporting 
procedures, the U.S. quantifies greenhouse gas emissions using the 
100-year time frame values for GWPs established in the IPCC Second 
Assessment Report.
---------------------------------------------------------------------------

    In 2005 emissions of the well-mixed greenhouse gas pollutant from 
CAA section 202(a) source categories represented 4.3 percent of total 
global well-mixed greenhouse gas emissions and 28 percent of global 
transport well-mixed greenhouse gas emissions (Table 1 of these 
Findings). If CAA section 202(a) source categories' emissions of well-
mixed greenhouse gas were ranked against total well-mixed greenhouse 
gas emissions for entire countries, CAA section 202(a) source category 
emissions would rank behind only China, the United States as a whole, 
Russia, and India, and would rank ahead of Japan, Brazil, Germany and 
every other country in the world. Indeed, countries with lower 
emissions than the CAA section 202(a) source categories are members of 
the 17 ``major economies'' ``that meet to advance the exploration of 
concrete initiatives and joint ventures that increase the supply of 
clean energy while cutting greenhouse gas emissions.'' See http://www.state.gov/g/oes/climate/mem/. It would be anomalous, to say the 
least, to consider Japan and these other countries as major players in 
the global climate change community and an integral part of the 
solution, but not find that CAA section 202(a) source category 
emissions contribute to the global problem. Thus, the Administrator 
finds that emission of well-mixed greenhouse gases from CAA section 
202(a) source categories contribute to the air pollution of well-mixed 
greenhouse gases.

 Table 1--Comparison to Global Greenhouse Gas (GHG) Emissions (Tg CO2e)
------------------------------------------------------------------------
                                                        Sec 202(a) share
                                           2005            (percent)
------------------------------------------------------------------------
All U.S. GHG emissions............              7,109               23.5
Global transport GHG emissions....              5,968               28.0
All global GHG emissions..........             38,726                4.3
------------------------------------------------------------------------

b. Section 202(a) of the CAA--Share of U.S. Aggregate Emissions of the 
Well-Mixed Greenhouse Gases
    The Administrator considered compared total emissions of the well-
mixed greenhouse gases from CAA section 202(a) source categories to 
total U.S. emissions of the well-mixed greenhouse gases as an 
indication of the role these sources play in the total U.S. 
contribution to the air pollution problem causing climate change.\41\
---------------------------------------------------------------------------

    \41\ Greenhouse gas emissions data for the United States in this 
section have been updated since the Proposed Findings to reflect 
EPA's most up-to-date information, which includes data for the year 
2007. The source of the U.S. greenhouse gas emissions data is the 
Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2007, 
published in 2009 (hereinafter ``U.S. Inventory'').
---------------------------------------------------------------------------

    In 2007, U.S. well-mixed greenhouse gas emissions were 7,150 
TgCO2eq. The dominant gas emitted was carbon dioxide, mostly 
from fossil fuel combustion. Methane was the second largest well-mixed 
greenhouse gas, followed by N2O, and the fluorinated gases 
(HFCs, PFCs, and SF6). Electricity generation was the 
largest emitting sector (2,445 TgCO2eq or 34 percent of

[[Page 66540]]

total U.S. greenhouse gas emissions), followed by transportation (1,995 
TgCO2eq or 28 percent) and industry (1,386 
TgCO2eq or 19 percent). Emissions from the CAA section 
202(a) source categories constitute the major part of the 
transportation sector. Land use, land use change, and forestry offset 
almost 15 percent of total U.S. emissions through net sequestration. 
Total U.S. well-mixed greenhouse gas emissions have increased by over 
17 percent between 1990 and 2007. The electricity generation and 
transportation sectors have contributed the most to this increase.
    In 2007 emissions of well-mixed greenhouse gases from CAA section 
202(a) source categories collectively were the second largest emitter 
of well-mixed greenhouse gases within the United States (behind the 
electricity generating sector), emitting 1,663 TgCO2eq and 
representing 23 percent of total U.S. emissions of well-mixed 
greenhouse gases (Table 2 of these Findings). The Administrator is 
keenly aware that the United States is the second largest emitter of 
well-mixed greenhouse gases. Part of analyzing whether a sector within 
the United States contributes to the global problem is to see how those 
emissions fit into the contribution from the United States as a whole. 
This informs her judgment as to the importance of emissions from this 
source category in any overall national strategy to address greenhouse 
gas emissions. Thus, it is relevant that CAA section 202(a) source 
categories are the second largest emitter of well-mixed greenhouse 
gases in the country. This is part of the Administrator looking at the 
totality of the circumstances. Based on this the Administrator finds 
that emission of well-mixed greenhouse gases from CAA section 202(a) 
source categories contribute to the air pollution of well-mixed 
greenhouse gases.

               Table 2--Sectoral Comparison to Total U.S. Greenhouse Gas (GHG) Emissions (Tg CO2e)
----------------------------------------------------------------------------------------------------------------
          U.S. emissions                1990         1995         2000         2005         2006         2007
----------------------------------------------------------------------------------------------------------------
Section 202(a) GHG emissions......       1231.9       1364.4       1568.1       1670.5       1665.7       1663.1
Share of U.S. (%).................        20.2%        21.1%        22.4%        23.5%        23.6%        23.3%
Electricity Sector emissions......       1859.1       1989.0       2329.3       2429.4       2375.5       2445.1
Share of U.S. (%).................        30.5%        30.8%        33.2%        34.2%        33.7%        34.2%
Industrial Sector emissions.......       1496.0       1524.5       1467.5       1364.9       1388.4       1386.3
Share of U.S. (%).................        24.5%        23.6%        20.9%        19.2%        19.7%        19.4%
                                   -----------------------------------------------------------------------------
    Total U.S. GHG emissions......       6098.7       6463.3       7008.2       7108.6       7051.1       7150.1
----------------------------------------------------------------------------------------------------------------

C. Response to Key Comments on the Administrator's Cause or Contribute 
Finding

    EPA received numerous public comments regarding the Administrator's 
proposed cause or contribute finding. Below is a brief discussion of 
some of the key comments. Responses to comments on this issue are also 
contained in the Response to Comments document, Volume 10.
1. The Administrator Reasonably Defined the ``Air Pollutant'' for the 
Cause or Contribute Analysis
a. The Supreme Court Held that Greenhouse Gases Fit Within the 
Definition of ``Air Pollutant'' in the CAA
    Several commenters reiterate arguments already rejected by the 
Supreme Court, arguing that greenhouse gases do not fit into the 
definition of ``air pollutant'' under the CAA. In particular, at least 
one commenter contends that EPA must show how greenhouse gases impact 
or materially change ``ambient air'' when defining air pollutant and 
making the endangerment finding. This commenter argues that because 
carbon dioxide is a naturally occurring and necessary element in the 
atmosphere, it cannot be considered to materially change air.
    These and similar arguments were already rejected by the Supreme 
Court in Massachusetts v. EPA, 549 U.S. 497 (2007). Briefs before the 
Supreme Court also argued that carbon dioxide is an essential role for 
life on earth and therefore cannot be considered an air pollutant, and 
that the concentrations of greenhouse gases that are a potential 
problem are not in the ``ambient air'' that people breathe.
    The Court rejected all of these and other arguments, noting that 
the statutory text forecloses these arguments. ``The Clean Air Act's 
sweeping definition of `air pollutant' includes `any air pollution 
agent or combination of such agents, including any physical, chemical * 
* * substance or matter which is emitted into or otherwise enters the 
ambient air . * * *' Sec.  7602(g) (emphasis added). On its face, the 
definition embraces all airborne compounds of whatever stripe, and 
underscores that intent through the repeated use of the word `any.' 
Carbon dioxide, methane, nitrous oxide, and hydrofluorocarbons are 
without a doubt `physical [and] chemical * * * substance[s] which [are] 
emitted into * * * the ambient air.' The statute is unambiguous.''
    547 U.S. at 529-30 (footnotes omitted); see also id. at 530, n26 
(the distinction regarding ambient air, however, finds no support in 
the text of the statute, which uses the phrase ``the ambient air'' 
without distinguishing between atmospheric layer.). Thus, the question 
of whether greenhouse gases fit within the definition of air pollutant 
under the CAA has been decided by the Supreme Court and is not being 
revisited here.
b. The Definition of Air Pollutant May Include Substances Not Emitted 
by CAA Section 202(a) Sources
    Many commenters argue that the definition of ``air pollutant''--
here well-mixed greenhouse gases--cannot include PFCs and SF6 because 
they are not emitted by CAA section 202(a) motor vehicles and hence, 
cannot be part of any ``air pollutant'' emitted by such sources. They 
argue that by improperly defining ``air pollutant'' to include 
substances that are not present in motor vehicle emissions, the Agency 
has exceeded its statutory authority under CAA section 202(a). 
Commenters contend that past endangerment findings under CAA section 
202(a) demonstrate EPA's consistent approach of defining ``air 
pollutant(s)'' in accordance with the CAA's clear direction, to include 
only those pollutants emitted from the relevant source category (citing 
Notice of Proposed Rulemaking for Heavy-Duty Engine and Vehicle 
Standards finding that ``emissions of NOX, VOCs, 
SOX, and PM from heavy-duty trucks can reasonably be 
anticipated to endanger the public health or welfare.'' (65 FR 35436, 
June 2, 2000). Commenters argue that EPA itself is inconsistent in the 
Proposed Findings, sometimes referring

[[Page 66541]]

to ``air pollutant'' as the group of six greenhouse gases, and other 
times falling back on the four greenhouse gases emitted by motor 
vehicles.
    EPA acknowledges that the Proposed Findings could have been clearer 
regarding the proposed definition of air pollutant, and how it was 
being applied to CAA section 202(a) sources, which emit only four of 
the six substances that meet the definition of well-mixed greenhouse 
gases. However, our interpretation does not exceed EPA's authority 
under CAA section 202(a). It is reasonable to define the air pollutant 
under CAA section 202(a) to include substances that have similar 
attributes (as discussed above), even if not all of the substances that 
meet that definition are emitted by motor vehicles. For example, as 
commenters note, EPA has heavy duty truck standards applicable to VOCs 
and PM, but it is highly unlikely that heavy duty trucks emit every 
substance that is included in the group defined as VOC or PM. See 40 
CFR 51.100(s) (defining volatile organic compound (VOC) as ``any 
compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic 
acid, metallic carbides or carbonates, and ammonium carbonate, which 
participates in atmospheric photochemical reactions'', a list of 
exemptions are also included in the definition); 40 CFR 51.100(oo) 
(defining particulate matter (PM) as ``any airborne finely divided 
solid or liquid material with an aerodynamic diameter smaller than 100 
micrometers'').
    In this circumstance the number of substances included in the 
definition of well-mixed greenhouse gases is much smaller than other 
``group'' air pollutants (e.g., six greenhouse gases versus hundreds of 
VOCs), and CAA section 202(a) sources emit an easily discernible number 
of these six substances. However, this does not mean that the 
definition of the well-mixed greenhouse gases as the air pollutant is 
unreasonable. By defining well-mixed greenhouse gases as a single air 
pollutant comprised of six substances with common attributes, the 
Administrator is giving effect to these shared attributes and how they 
are relevant to the air pollution to which they contribute. The fact 
that these six substances share these common, relevant attributes is 
true regardless of the source category being evaluated for 
contribution. Grouping these six substances as one air pollutant is 
reasonable regardless of whether a contribution analysis is undertaken 
for CAA section 202(a) sources that emit one subset of the six 
substances (e.g., carbon dioxide, CH4, N20 and 
HFCs, but not PFCs and SF6), or for another category of 
sources that may emit another subset. For example, electronics 
manufacturers that may emit N2O, PFCs, HFCs, SF6 
and other fluorinated compounds, but not carbon dioxide or 
CH4 unless there is on-site fuel combustion. In other words, 
it is not necessarily the source category being evaluated for 
contribution that determines the reasonableness of defining a group air 
pollutant based on the shared attributes of the group.
    Even if EPA agreed with commenters, and defined the air pollutant 
as the group of four compounds emitted by CAA section 202(a) sources, 
it would not change the result. The Administrator would make the same 
contribution finding as it would have no material effect on the 
emissions comparisons discussed above.
c. It Was Reasonable for the Administrator To Define the Single Air 
Pollutant as the Group of Substances With Common Attributes
    Several commenters disagree with EPA's proposed definition of a 
single air pollutant composed of the six well-mixed greenhouse gases as 
a class. Commenters argue that the analogy to VOCs is misplaced because 
VOCs are all part of a defined group of chemicals, for which there are 
established quantification procedures, and for which there were 
extensive data showing that the group of compounds had demonstrated and 
quantifiable effects on ambient air and human health and welfare, and 
for which verifiable dispersion models existed. They contend this is in 
stark contrast to the entirely diverse set of organic and inorganic 
compounds EPA has lumped together for purposes of the Proposed 
Findings, and for which no model can accurately predict or quantify the 
actual impact or improvement resulting from controlling the compounds. 
Moreover, they argue that the gases EPA is proposing to list together 
as one pollutant are all generated by different processes and, if 
regulated, would require different types of controls; the four gases 
emitted by mobile sources can generally be limited only by using 
controls that are specific to each.
    At least one commenter argues that EPA cannot combine greenhouse 
gases into one pollutant because their common attribute is not a 
``physical, chemical, biological or radioactive property'' (quoting 
from CAA section 302(g)), but rather their effect or impacts on the 
environment. They say this differs from VOCs, which share the common 
attribute of volatility, or PM which shares the physical property of 
being particles.
    As discussed above, the well-mixed greenhouse gases share physical 
attributes, as well as attributes based on sound policy considerations. 
The definition of ``air pollutant'' in CAA section 302(g) does not 
limit consideration of common attributes to those that are ``physical, 
chemical, biological or radioactive property'' as one commenter claims. 
Rather, the definition's use of the adjectives ``physical, chemical, 
biological or radioactive'' refer to the different types of substance 
or matter that is emitted. It is not a limitation on what 
characteristics the Administrator may consider when deciding how to 
group similar substances when defining a single air pollutant.
    The common attributes that the Administrator considered when 
defining the well-mixed greenhouse gases are reasonable. While these 
six substances may originate from different processes, and require 
different control strategies, that does not detract from the fact that 
they are all long-lived, well-mixed in the atmosphere, directly 
emitted, of well-known radiative forcing, and generally grouped and 
considered together in climate change scientific and policy forums. 
Indeed, other group pollutants also originate from a variety of 
processes and a result may require different control technologies. For 
example, both a power plant and a dirt road can result in PM emissions, 
and the method to control such emissions at each source would be 
different. But these differences in origin or control do not undermine 
the reasonableness of considering PM as a single air pollutant. The 
fact that there are differences, as well as similarities, among the 
well-mixed greenhouse gases does not render the decision to group them 
together as one air pollutant unreasonable.
2. The Administrator's Cause or Contribute Analysis Was Reasonable
a. The Administrator Does Not Need To Find Significant Contribution, or 
Establish a Bright Line
    Many commenters essentially argue that EPA must establish a bright 
line below which it would never find contribution regardless of the air 
pollutant, air pollution, and other factors before the Agency. For 
example, some commenters argue that EPA must provide some basis for 
determining de minimis amounts that fall below the threshold of 
``contributing'' to the endangerment of public health and welfare under 
CAA section 202(a).

[[Page 66542]]

Commenters take issue with EPA's statement that it ``need not determine 
at this time the circumstances in which emissions would be trivial or 
de minimis and would not warrant a finding of contribution.'' 
Commenters argue that EPA cannot act arbitrarily by determining that a 
constituent contributing a certain percent to endangerment in one 
instance is de minimis and in another is contributing to endangerment 
of public health and welfare. They request that EPA revise the preamble 
language to make clear that the regulated community can rely on its 
past determinations with respect to ``contribution'' determinations to 
predict future agency action and argue that EPA should promulgate 
guidance on how it determines whether a contribution exceeds a de 
minimis level for purposes of CAA section 202(a) before finalizing the 
proposal.
    The commenters that argue that the air pollution EPA must analyze 
to determine endangerment is limited to the air pollution resulting 
from new motor vehicles also argue that as a result, the contribution 
of emissions from new motor vehicles must be significant. They 
essentially contend that the endangerment and cause or contribute tests 
are inter-related and the universe of both tests is the same. In 
support of their argument, commenters argue that because the clause 
``cause, or contribute to, air pollution'' is in plural form, it must 
be referring back to ``any class or classes of new motor vehicles or 
new motor vehicle engines,'' demonstrating that EPA must consider only 
the emissions from new motor vehicles which emit the air pollution 
which endangers.
    Since the Administrator issued the Proposed Findings, the DC 
Circuit issued another opinion discussing the concept of contribution. 
See Catawba County v. EPA, 571 F.3d 20 (DC Cir. 2009). This decision, 
along with others, supports the Administrator's interpretation that the 
level of contribution under CAA section 202(a) does not need to be 
significant. The Administrator is not required to establish a bright 
line below which she would never find contribution under any 
circumstances. Finally, it is reasonable for the Administrator to apply 
a ``totality-of-the-circumstances test to implement a statute that 
confers broad discretionary authority, even if the test lacks a 
definite `threshold' or `clear line of demarcation to define an open-
ended term.'' Id. at 39 (citations omitted).
    In upholding EPA's PM2.5 attainment and nonattainment 
designation decisions, the DC Circuit analyzed CAA section 107(d), 
which requires EPA to designate an area as nonattainment if it 
``contributes to ambient air quality in a nearby area'' not attaining 
the national ambient air quality standards. Id. at 35. The court noted 
that it had previously held that the term ``contributes'' is ambiguous 
in the context of CAA language. See EDF v. EPA, 82 F.3d 451, 459 (DC 
Cir. 1996). ``[A]mbiguities in statutes within an agency's jurisdiction 
to administer are delegations of authority to the agency to fill the 
statutory gap in reasonable fashion.'' 571 F.3d at 35 (citing Nat's 
Cable & Telecomms. Ass'c v. Brand X Internet Servs, 545 U.S. 967, 980 
(2005)).
    The court then proceeded to consider and reject petitioners' 
argument that the verb ``contributes'' in CAA section 107(d) 
necessarily connotes a significant causal relationship. Specifically, 
the DC Circuit again noted that the term is ambiguous, leaving it to 
EPA to interpret in a reasonable manner. In the context of this 
discussion, the court noted that ``a contribution may simply exacerbate 
a problem rather than cause it * * * '' 571 F.3d at 39. This is 
consistent with the DC Circuit's decision in Bluewater Network v. EPA, 
370 F.3d 1 (DC Cir. 2004), in which the court noted that the term 
contribute in CAA section 213(a)(3) ``[s]tanding alone, * * * has no 
inherent connotation as to the magnitude or importance of the relevant 
`share' in the effect; certainly it does not incorporate any 
`significance' requirement.'' 370 F.3d at 13. The court found that the 
bare ``contribute'' language invests the Administrator with discretion 
to exercise judgment regarding what constitutes a sufficient 
contribution for the purpose of making an endangerment finding. Id. at 
14.
    Finally, in Catawba County, the DC Circuit also rejected 
``petitioners' argument that EPA violated the statute by failing to 
articulate a quantified amount of contribution that would trigger'' the 
regulatory action. 571 F.3d at 39. Although petitioners preferred that 
EPA establish a bright-line test, the court recognized that the statute 
did not require that EPA ``quantify a uniform amount of contribution.'' 
Id.
    Given this context, it is entirely reasonable for the Administrator 
to interpret CAA section 202(a) to require some level of contribution 
that, while more than de minimis or trivial, does not rise to the level 
of significance. Moreover, the approach suggested by at least one 
commenter collapses the two prongs of the test by requiring that 
contribution must be significant because any climate change impacts 
upon which an endangerment determination is made result solely from the 
greenhouse gas emissions of motor vehicles. It essentially eliminates 
the ``contribute'' part of the ``cause or contribute'' portion of the 
test. This approach was clearly rejected by the en banc court in Ethyl. 
541 F.2d at 29 (rejecting the argument that the emissions of the fuel 
additive to be regulated must ``in and of itself, i.e. considered in 
isolation, endanger[ ] public health.''); see also Catawba County, 571 
F.3d at 39 (noting that even if the test required significant 
contribution it would be reasonable for EPA to find a county's addition 
of PM2.5 is significant even though the problem would 
persist in its absence). It is the commenter, not EPA that is ignoring 
the statutory language. Whether or not the clause ``cause, or 
contribute to, air pollution'' refers back to ``any class or classes of 
new motor vehicles or new motor vehicle engines,'' or to ``emission of 
any air pollutant,'' the language of CAA section 202(a) clearly 
contemplates that emission of an air pollutant from any class or 
classes may merely contribute to, versus cause, the air pollution which 
endangers.
    It is also reasonable for EPA to decline to establish a ``bright-
line `objective' test of contribution.'' 571 F.3d at 39. As noted in 
the Proposed Findings, when exercising her judgment, the Administrator 
not only considers the cumulative impact, but also looks at the 
totality of the circumstances (e.g., the air pollutant, the air 
pollution, the nature of the endangerment, the type of source category, 
the number of sources in the source category, and the number and type 
of other source categories that may emit the air pollutant) when 
determining whether the emissions justify regulation under the CAA. Id. 
(It is reasonable for an agency to adopt a totality-of-the-
circumstances test).
    Even if EPA agreed that a level of significance was required to 
find contribution, for the reasons discussed above, EPA would find that 
the contribution from CAA section 202(a) source categories is 
significant. Their emissions are larger than the great majority of 
emitting countries, larger than several major emitting countries, and 
they constitute one of the largest parts of the U.S. emissions 
inventory.
b. The Unique Global Aspects of Climate Change Are an Appropriate 
Consideration in the Contribution Analysis
    Some commenters disagree with statements in the Proposed Findings 
that the ``unique, global aspects of the climate change problem tend to 
support a finding that lower levels of emissions should be considered 
to contribute to the air pollution than might otherwise

[[Page 66543]]

be appropriate when considering contribution to a local or regional air 
pollution problem.'' They argue there is no basis in the CAA or 
existing EPA policy for this position, and that it reveals an apparent 
effort to expand EPA's authority to the ``truly trivial or de minimis'' 
sources that are acknowledged to be outside the scope of regulation, in 
that it expands EPA's authority to regulate pollutants to address 
global effects.
    Commenters also assert that contrary to EPA's position, lower 
contribution numbers are appropriate when looking at local pollution, 
like nonattainment concerns--in other words, in the context of a 
statutory provision like CAA section 213 specifically aimed at 
targeting small source categories to help nonattainment areas meet air 
quality standards. However, they conclude this policy is simply 
inapplicable in the context of global climate change.
    As discussed above, the term ``contribute'' is ambiguous and 
subject to the Administrator's reasonable interpretation. It is 
entirely appropriate for the Administrator to look at the totality of 
the circumstances when making a finding of contribution. In this case, 
the Administrator believes that the global nature of the problem 
justifies looking at contribution in a way that takes account of these 
circumstances. More specifically, because climate change is a global 
problem that results from global greenhouse gas emissions, there are 
more sources emitting greenhouse gases (in terms both of absolute 
numbers of sources and types of sources) than EPA typically encounters 
when analyzing contribution towards a more localized air pollution 
problem. From a percentage perspective, there are no dominating sources 
and fewer sources that would even be considered to be close to 
dominating. The global problem is much more the result of numerous and 
varied sources each of which emit what might seem to be smaller 
percentage amounts when compared to the total. The Administrator's 
approach recognizes this reality, and focuses on evaluating the 
relative importance of the CAA section 202(a) source categories 
compared to other sources when viewed in this context.
    This recognition of the unique totality of the circumstances before 
the Administrator now as compared to previous contribution decisions is 
entirely appropriate. It is not an attempt by the Administrator to 
regulate ``truly trivial or de minimis'' sources, or to regulate 
sources based on their global effects. The Administrator is determining 
whether greenhouse gas emissions from CAA section 202(a) sources 
contribute to an air pollution problem is endangering U.S. public 
health and welfare. As discussed in the Proposed Findings, no single 
greenhouse gas source category dominates on the global scale, and many 
(if not all) individual greenhouse gas source categories could appear 
small in comparison to the total, when, in fact, they could be very 
important contributors in terms of both absolute emissions or in 
comparison to other source categories, globally or within the United 
States. If the United States and the rest of the world are to combat 
the risks associated with global climate change, contributors must do 
their part even if their contributions to the global problem, measured 
in terms of percentage, are smaller than typically encountered when 
tackling solely regional or local environmental issues. The commenters' 
approach, if used globally, would effectively lead to a tragedy of the 
commons, whereby no country or source category would be accountable for 
contributing to the global problem of climate change, and nobody would 
take action as the problem persists and worsens. The Administrator's 
approach, on the contrary, avoids this kind of approach, and is a 
reasonable exercise of her discretion to determine contribution in the 
global context in which this issue arises.
    Importantly, as discussed above, the contribution from CAA section 
202(a) sources is anything but trivial or de minimis under any 
interpretation of contribution. See, Massachusetts v. EPA, 549 U.S. at 
1457-58 (``Judged by any standard, U.S. motor-vehicle emissions make a 
meaningful contribution to greenhouse gas concentrations and hence, * * 
* to global warming'').
c. The Administrator Reasonably Relied on Comparisons of Emissions From 
Existing CAA Section 202(a) Source Categories
i. It Was Reasonable To Use Existing Emissions From Existing CAA 
Section 202(a) Source Categories Instead of Projecting Future Emissions 
From New CAA Section 202(a) Source Categories
    Many commenters argue that EPA improperly evaluated the emissions 
from the entire motor vehicle fleet, and it is required to limit its 
calculation to just emissions from new motor vehicles. Thus the 
emissions that EPA should consider in the cause or contribute 
determination is far less than the 4.3 percent of U.S. greenhouse gas 
emissions attributed to motor vehicles in the Proposed Findings, 
because this number includes both new and existing motor vehicles. One 
commenter calculated the emissions from new motor vehicles as being 1.8 
percent of global emissions, assuming approximately one year of new 
motor vehicle production in the United States (11 million vehicles) in 
a total global count currently of approximately 600 million motor 
vehicles.
    In the Proposed Findings, EPA determined the emissions from the 
entire fleet of motor vehicles in the United States for a certain 
calendar year. EPA explained that, consistent with its traditional 
practice, it used the recent motor vehicle emissions inventory for the 
entire fleet as a surrogate for estimates of emissions for just new 
motor vehicles and engines. This was appropriate because future 
projected emissions are uncertain and current emissions data are a 
reasonable proxy for near-term emissions.
    In effect, EPA is using the inventory for the current fleet of 
motor vehicles as a reasonable surrogate for a projection of the 
inventory from new motor vehicles over the upcoming years. New motor 
vehicles are produced year in and year out, and over time the fleet 
changes over to a fleet composed of such vehicles. This occurs in a 
relatively short time frame, compared to the time period at issue for 
endangerment. Because new motor vehicles are produced each year, and 
continue to emit over their entire life, over a relatively short period 
of time the emission from the entire fleet is from vehicles produced 
after a certain date. In addition, the emissions from new motor 
vehicles are not limited to the emissions that occur only during the 
one year when they are new, but are emissions over the entire life of 
the vehicle.
    In such cases, EPA has traditionally used the recent emissions from 
the entire current fleet of motor vehicles as a reasonable surrogate 
for such a projection instead of trying to project and model those 
emissions. While this introduces some limited degree of uncertainty, 
the difference between recent actual emissions from the fleet and 
projected future emissions from the fleet is not expected to differ in 
any way that would substantively change the decision made concerning 
cause or contribution. There is not a specific numerical bright line 
that must be achieved, and the numerical percentages are not treated 
and do not need to be treated as precise values. This approach provides 
a reasonable and clear indication of the relative magnitudes involved, 
and EPA does not believe that attempting to make future

[[Page 66544]]

projections (for both vehicles and the emissions value they are 
compared to) would provide any greater degree of accuracy or precision 
in developing such a relative comparison.
ii. The Administrator Did Not Have To Use a Subset or Reduced Emissions 
Estimate From Existing CAA Section 202(a) Source Categories
    Several commenters note that although EPA looks at emissions from 
all motor vehicles regulated under CAA section 202(a) in its 
contribution analysis, the Presidential announcement in May 2009 
indicated that EPA was planning to regulate only a subset of 202(a) 
sources. Thus, they question whether the correct contribution analysis 
should look only at the emissions from that subset and not all CAA 
section 202(a) sources. Some commenters also argue that because 
emission standards will not eliminate all greenhouse gas emissions from 
motor vehicles, the comparison should compare the amount of greenhouse 
gas emissions ``reduced'' by those standards to the global greenhouse 
emissions. They also contend that the cost of the new standards will 
cause individual consumers, businesses, and other vehicle purchasers to 
hold on to their existing vehicles to a greater extent, thereby 
decreasing the amount of emissions reductions attributable to the 
standard and appropriately considered in the contribution analysis. 
Some commenters go further and contend that EPA also can only include 
that incremental reduction that the EPA regulations will achieve beyond 
any reductions resulting from CAFE standards that NHTSA will set.
    Although the May announcement and September proposed rule involved 
only the light duty motor vehicle sector, the Administrator is making 
this finding for all classes of new motor vehicles under CAA section 
202(a). Thus, although the announcement and proposed rule involve light 
duty vehicles, EPA is working to develop standards for the rest of the 
classes of new motor vehicles under CAA section 202(a). As the Supreme 
Court noted, EPA has ``significant latitude as to the manner, timing, 
content, and coordination of its regulations with those of other 
agencies. Massachusetts v. EPA, 549 U.S. at 533.
    The argument that the Administrator can only look at that portion 
of emissions that will be reduced by any CAA section 202(a) standards, 
and even then only the reduction beyond those attributable to CAFE 
rules, finds no basis in the statutory language. The language in CAA 
section 202(a) requires that the Administrator set ``standards 
applicable to the emission of any air pollutant from [new motor 
vehicles], which in [her] judgment cause, or contribute to, air 
pollution which [endangers].'' It does not say set ``standards 
applicable to the emission of any air pollutant from [new motor 
vehicles], if in [her] judgment the emissions of that air pollutant as 
reduced by that standard cause, or contribute to, air pollution which 
[endangers].'' As discussed above, the decisions on cause or contribute 
and endangerment are separate and distinct from the decisions on what 
emissions standards to set under CAA section 202(a). The commenter's 
approach would improperly integrate these separate decisions. Indeed, 
because, as discussed above, the Administrator does not have to propose 
standards concurrent with the endangerment and cause or contribute 
findings, she would have to be prescient to know at the time of the 
contribution finding exactly the amount of the reduction that would be 
achieved by the standards to be set. As discussed above, for purposes 
of these findings we look at what would be the emissions from new motor 
vehicles if no action were taken. Current emissions from the existing 
CAA section 202(a) vehicle fleet are an appropriate estimate.
d. The Administrator Reasonably Compared CAA Section 202(a) Source 
Emissions to Both Global and Domestic Emissions of Well-Mixed 
Greenhouse Gases
    EPA received many comments on the appropriate comparison(s) for the 
contribution analysis. Several commenters argue that in order to get 
around the ``problem'' of basing an endangerment finding upon a source 
category that contributes only 1.8 percent annually to global 
greenhouse gas emissions, EPA inappropriately also made comparisons to 
total U.S. greenhouse gas emissions. These commenters argue that a 
comparison of CAA section 202(a) source emissions to U.S. greenhouse 
gas emissions, versus global emissions, is arbitrary for purposes of 
the cause or contribute analysis, because it conflicts with the 
Administrator's definition of ``air pollution,'' as well as the nature 
of global warming. They note that throughout the Proposed Findings, the 
Administrator focuses on the global nature of greenhouse gas. Thus, 
they continue, while the percentage share of motor vehicle emissions at 
the U.S. level may be relevant for some purposes, it is irrelevant to a 
finding of whether these emissions contribute to the air pollution, 
which the Administrator has proposed to define on a global rather than 
a domestic basis. Commenters also accuse EPA of arbitrarily picking and 
choosing when it takes a global approach (e.g., endangerment finding) 
and when it does not (e.g., contribution findings).
    The language of CAA section 202(a) is silent regarding how the 
Administrator is to make her contribution analysis. While it requires 
that the Administrator assess whether emission of an air pollutant 
contributes to air pollution which endangers, it does not limit how she 
may undertake that assessment. It surely is reasonable that the 
Administrator look at how CAA section 202(a) source category emissions 
compare to global emissions on an absolute basis, by themselves. But 
the United States as a nation is the second largest emitter of 
greenhouse gases. It is entirely appropriate for the Administrator to 
decide that part of understanding how a U.S. source category emitting 
greenhouse gases fits into the bigger picture of global climate change 
is to appreciate how that source category fits into the contribution 
from the United States as a whole, where the United States as a country 
is a major emitter of greenhouse gases. Knowing that CAA section 202(a) 
source categories are the second largest emitter of well-mixed 
greenhouse gases in the country is relevant to understanding what role 
they play in the global problem and hence whether they ``contribute'' 
to the global problem. Moreover, the Administrator is not ``picking and 
choosing'' when she applies a global or domestic approach in these 
Findings. Rather, she is looking at both of these emissions comparisons 
as appropriate under the applicable science, facts, and law.
e. The Amount of Well-Mixed Greenhouse Gas Emissions From CAA Section 
202(a) Sources Reasonably Supports a Finding of Contribution
    Many commenters argue that the ``cause or contribute'' prong of the 
Proposal's endangerment analysis fails to satisfy the applicable legal 
standard, which requires more than a minimal contribution to the ``air 
pollution reasonably anticipated to endanger public health or 
welfare.'' They contend that emissions representing approximately four 
percent of total global greenhouse gas emissions are a minimal 
contribution to global greenhouse gas concentrations.
    EPA disagrees. As stated above, CAA section 202(a) source category 
total emissions of well-mixed greenhouse gases are higher than most 
countries in the world; countries that the U.S. and others believe play 
a major role in the

[[Page 66545]]

global climate change problem. Moreover, the percent of global well-
mixed greenhouse gas emissions that CAA section 202(a) source 
categories represent is higher than percentages that the EPA has found 
contribute to air pollution problems. See Bluewater Network, 370 F.3d 
at 15 (``For Fairbanks, this contribution was equivalent to 1.2 percent 
of the total daily CO inventory for 2001.'') As noted above, there is 
no bright line for assessing contribution, but as discussed in the 
Proposed Findings and above, when looking at a global problem like 
climate change, with many sources of emissions and no dominating 
sources from a global perspective, it is reasonable to consider that 
lower percentages contribute than one may consider when looking at a 
local or regional problem involving fewer sources of emissions. The 
Administrator agrees that ``[j]udged by any standard, U.S. motor-
vehicle emissions make a meaningful contribution to greenhouse gas 
concentrations and hence, * * * to global warming.'' Massachusetts v. 
EPA, 549 U.S. at 525.

VI. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

    Under Executive Order (EO) 12866 (58 FR 51735, October 4, 1993), 
this action is a ``significant regulatory action'' because it raises 
novel policy issues. Accordingly, EPA submitted this action to the 
Office of Management and Budget (OMB) for review under EO 12866 and any 
changes made in response to Office of Management and Budget (OMB) 
recommendations have been documented in the docket for this action.

B. Paperwork Reduction Act

    This action does not impose an information collection burden under 
the provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. 
Burden is defined at 5 CFR 1320.3(b). These Findings do not impose an 
information collection request on any person.

C. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) generally requires an agency 
to prepare a regulatory flexibility analysis of any rule subject to 
notice and comment rulemaking requirements under the Administrative 
Procedure Act or any other statute unless the agency certifies that the 
rule will not have a significant economic impact on a substantial 
number of small entities. Small entities include small businesses, 
small organizations, and small governmental jurisdictions.
    For purposes of assessing the impacts of this action on small 
entities, small entity is defined as: (1) A small business as defined 
by the Small Business Administration's (SBA) regulations at 13 CFR 
121.201; (2) a small governmental jurisdiction that is a government of 
a city, county, town, school district, or special district with a 
population of less than 50,000; and (3) a small organization that is 
any not-for-profit enterprise which is independently owned and operated 
and is not dominant in its field.
    Because these Findings do not impose any requirements, the 
Administrator certifies that this action will not have a significant 
economic impact on a substantial number of small entities. This action 
does not impose any requirements on small entities. The endangerment 
and cause or contribute findings do not in-and-of-themselves impose any 
new requirements but rather set forth the Administrator's determination 
on whether greenhouse gases in the atmosphere may reasonably be 
anticipated to endanger public health or welfare, and whether emissions 
of greenhouse gases from new motor vehicles and engines contribute to 
this air pollution. Accordingly, the action affords no opportunity for 
EPA to fashion for small entities less burdensome compliance or 
reporting requirements or timetables or exemptions from all or part of 
the Findings.

D. Unfunded Mandates Reform Act

    This action contains no Federal mandates under the provisions of 
Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), 2 U.S.C. 
1531-1538 for State, local, or tribal governments or the private 
sector. The action imposes no enforceable duty on any State, local or 
tribal governments or the private sector. Therefore, this action is not 
subject to the requirements of sections 202 or 205 of the UMRA.
    This action is also not subject to the requirements of section 203 
of UMRA because it contains no regulatory requirements that might 
significantly or uniquely affect small governments. This finding does 
not impose any requirements on industry or other entities.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. Because this 
action does not impose requirements on any entities, it will not have 
substantial direct effects on the States, on the relationship between 
the national government and the States, or on the distribution of power 
and responsibilities among the various levels of government, as 
specified in Executive Order 13132. Thus, Executive Order 13132 does 
not apply to this action.

F. Executive Order 13175: Consultation and Coordination With Indian 
Tribal Governments

    This action does not have tribal implications, as specified in 
Executive Order 13175 (65 FR 67249, November 9, 2000). This action does 
not have substantial direct effects on one or more Indian tribes, on 
the relationship between the Federal Government and Indian tribes, or 
on the distribution of power and responsibilities between the Federal 
Government and Indian tribes, nor does it impose any enforceable duties 
on any Indian tribes. Thus, Executive Order 13175 does not apply to 
this action.

G. Executive Order 13045: Protection of Children From Environmental 
Health Risks and Safety Risks

    EPA interprets EO 13045 (62 FR 19885, April 23, 1997) as applying 
only to those regulatory actions that concern health or safety risks, 
such that the analysis required under section 5-501 of the EO has the 
potential to influence the regulation. This action is not subject to EO 
13045 because it does not establish an environmental standard intended 
to mitigate health or safety risks. Although the Administrator 
considered health and safety risks as part of these Findings, the 
Findings themselves do not impose a standard intended to mitigate those 
risks.

H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use

    This action is not a ``significant energy action'' as defined in 
Executive Order 13211 (66 FR 28355 (May 22, 2001)), because it is not 
likely to have a significant adverse effect on the supply, 
distribution, or use of energy because it does not impose any 
requirements.

I. National Technology Transfer and Advancement Act

    Section 12(d) of the National Technology Transfer and Advancement 
Act of 1995 (``NTTAA''), Public Law 104-113, 12(d) (15 U.S.C. at 272 
note) directs EPA to use voluntary consensus standards in its 
regulatory activities unless to do so would be inconsistent with 
applicable law or otherwise impractical. Voluntary consensus

[[Page 66546]]

standards are technical standards (e.g., materials specifications, test 
methods, sampling procedures, and business practices) that are 
developed or adopted by voluntary consensus standards bodies. NTTAA 
directs EPA to provide Congress, through OMB, explanations when the 
Agency decides not to use available and applicable voluntary consensus 
standards.
    This action does not involve technical standards. Therefore, EPA 
did not consider the use of any voluntary consensus standards.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations

    Executive Order (EO) 12898 (59 FR 7629, Feb. 16, 1994) establishes 
federal executive policy on environmental justice. Its main provision 
directs federal agencies, to the greatest extent practicable and 
permitted by law, to make environmental justice part of their mission 
by identifying and addressing, as appropriate, disproportionately high 
and adverse human health or environmental effects of their programs, 
policies, and activities on minority populations and low-income 
populations in the United States.
    EPA has determined that these Findings will not have 
disproportionately high and adverse human health or environmental 
effects on minority or low-income populations because it does not 
affect the level of protection provided to human health or the 
environment. Although the Administrator considered climate change risks 
to minority or low-income populations as part of these Findings, this 
action does not impose a standard intended to mitigate those risks and 
does not impose requirements on any entities.

K. Congressional Review Act

    The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the 
Small Business Regulatory Enforcement Fairness Act of 1996, generally 
provides that before a rule may take effect, the agency promulgating 
the rule must submit a rule report, which includes a copy of the rule, 
to each House of the Congress and to the Comptroller General of the 
United States. EPA will submit a report containing this rule and other 
required information to the U.S. Senate, the U.S. House of 
Representatives, and the Comptroller General of the United States. This 
action is not a ``major rule'' as defined by 5 U.S.C. 804(2). This rule 
will be effective January 14, 2010.

    Dated: December 7, 2009.
Lisa P. Jackson,
Administrator.
[FR Doc. E9-29537 Filed 12-14-09; 8:45 am]
BILLING CODE 6560-50-P