Climate Change: Information on Three Air Pollutants' Climate	 
Effects and Emissions Trends (28-APR-03, GAO-03-25).		 
                                                                 
Solar radiation is absorbed by the earth and is subsequently	 
reemitted. The buildup of carbon dioxide and certain other gases 
in the earth's atmosphere traps some of that radiation. This is  
known as the greenhouse effect and is believed to contribute to a
warming of the earth's climate. Concerns are growing that, in	 
addition to carbon dioxide and other conventional greenhouse	 
gases, certain air pollutants may affect the climate. GAO was	 
asked to examine (1) the extent of agreement among scientists	 
regarding the effect on the climate of three air		 
pollutants--black carbon (soot), ground-level ozone, and sulfate 
aerosols--and (2) seven countries' efforts to control these	 
pollutants, trends in these substances in these countries over	 
the past 2 decades, and estimates for the next decade. GAO was	 
also asked to summarize the relationship between economic growth 
and environmental pollution. The seven countries include four	 
that are economically developed--Germany, Japan, the United	 
Kingdom, and the United States--and three that are		 
developing--China, India, and Mexico. These countries were chosen
because they have large economies with a high potential to emit  
these pollutants. The two federal agencies asked to comment	 
generally agreed with the information presented in this report.  
-------------------------Indexing Terms------------------------- 
REPORTNUM:   GAO-03-25						        
    ACCNO:   A06672						        
  TITLE:     Climate Change: Information on Three Air Pollutants'     
Climate Effects and Emissions Trends				 
     DATE:   04/28/2003 
  SUBJECT:   Air pollution					 
	     Air pollution control				 
	     Environmental monitoring				 
	     Environmental policies				 
	     International agreements				 
	     International cooperation				 
	     Economic analysis					 
	     China						 
	     Germany						 
	     India						 
	     Japan						 
	     Mexico						 
	     United Kingdom					 
	     United Nations Framework Convention on		 
	     Climate Change					 
                                                                 

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GAO-03-25

                                       A

Report to Congressional Requesters

April 2003 CLIMATE CHANGE Information on Three Air Pollutants* Climate
Effects and Emissions Trends

GAO- 03- 25

Transmittal Letter 1 Results in Brief 4 Background 6 Scientists Agree on
the Overall Direction of the Three Pollutants*

Climate Impacts, but the Estimates of Impacts Contain Significant
Uncertainties 13 The Three Pollutants Are Generally Declining in
Economically

Developed Countries, but Not in Developing Countries; All Seven Countries
Are Acting to Reduce Emissions 18 Studies of the Effect of Economic Growth
on the Environment

Are Inconclusive 44 Conclusions 51 Agency Comments 52

Appendixes

Appendix I: Scope and Methodology 54

Appendix II: Programs and Measures to Reduce Emissions of Sulfur Dioxide
56

Appendix III: Programs and Measures to Reduce Emissions of Black Carbon or
Particulate Matter 58

Appendix IV: Programs and Measures to Reduce Ground- Level Ozone 59

Appendix V: Summary of Results of Selected Studies on Economic Growth and
Environmental Pollution 61

Appendix VI: GAO Contact and Staff Acknowledgments 62 Tables Table 1:
Comparative Statistics of the Seven Countries

Reviewed 12 Table 2: Results of Selected Studies of Economic Growth and

Environmental Quality 61 Figures Figure 1: Sources and Estimated Mean
Atmospheric Lifetimes of

Selected Substances Affecting Climate 8 Figure 2: Direct Effects of
Several Substances on Climate Change as Reported in the IPCC*s Third
Assessment

Report, 2001 14

Figure 3: Sulfur Dioxide Emissions in Four Developed Countries, 1980- 99
19 Figure 4: Projected Sulfur Dioxide Emissions in Four Developed

Countries, 1990- 2010 20 Figure 5: Sulfur Dioxide Emissions in China and
Mexico,

Selected Years 24 Figure 6: Black Carbon Emissions in the United States,

United Kingdom, Germany, and Japan, 1980- 96 29 Figure 7: Black Carbon
Emissions in China, India, and Mexico, 1980- 96 33

Figure 8: Annually Averaged Global Ozone Concentrations at 5 Kilometers,
Parts per Billion, 1990 38 Figure 9: Projected Annually Averaged Global
Ozone

Concentrations at 5 Kilometers, Parts per Billion, 2025 39 Figure 10:
Number of Areas Exceeding the Ozone Standard, United States and Germany,
1990- 2000 41

Figure 11: Hypothetical Inverted U- Shaped Curve, Showing Relationship
Between Per Capita Income and Environmental Pollution 45 Figure 12:
Estimated Turning Points Found in Selected

Studies of Particulate Matter, Sulfur Dioxide, and Carbon Dioxide 48

Abbreviations

CLRTAP Convention on Long- Range Transboundary Air Pollution EIA Energy
Information Administration EPA Environmental Protection Agency EU European
Union IPCC Intergovernmental Panel on Climate Change UNFCCC United Nations
Framework Convention on Climate Change

This is a work of the U. S. Government and is not subject to copyright
protection in the United States. It may be reproduced and distributed in
its entirety without further permission from GAO. It may contain
copyrighted graphics, images or other materials. Permission from the
copyright holder may be necessary should you wish to reproduce copyrighted
materials separately from GAO*s product.

Transmi tal Lett t er

April 28, 2003 The Honorable W. J. (Billy) Tauzin Chairman Committee on
Energy and Commerce House of Representatives

The Honorable Joe Barton Chairman, Subcommittee on Energy and Air Quality
Committee on Energy and Commerce House of Representatives

The Honorable James C. Greenwood Chairman, Subcommittee on Oversight and
Investigations Committee on Energy and Commerce House of Representatives

Carbon dioxide and certain other gases in the earth*s atmosphere trap the
sun*s heat and prevent it from escaping back into space. This phenomenon,
known as the greenhouse effect, tends to warm the earth*s surface; the
gases that cause it are called greenhouse gases. Most scientists agree
that a change in the earth*s climate could have wide- ranging effects on
economies, ecosystems, and human habitation. Climate change could make
some locations unsuitable for growing traditional crops, which could lead
to economic disruptions, especially in agricultural economies. However,
warming is not the only issue of concern with respect to greenhouse gas

emissions. A buildup of such gases could also alter precipitation
patterns, causing some areas to receive more rain and others to become
drier. Extreme events, such as drought or floods, could become more
frequent. In

addition, if climate change causes sea levels to rise substantially, low-
lying areas might become uninhabitable, forcing the dislocation of entire
populations. Evidence suggests that climate change is the result of both
human actions (such as fossil fuel burning) and natural phenomena (such as
solar variability). However, according to an international panel of
experts, most of the warming observed over the past 50 years is
attributable to human activities.

In recent decades, concentrations of greenhouse gases have built up in the
atmosphere. Concerned about these increased concentrations, the United
States and many other nations entered into a treaty to stabilize
atmospheric concentrations of greenhouse gases at levels that would
prevent dangerous human interference with the climate system.

The United States ratified this treaty, the United Nations Framework
Convention on Climate Change (UNFCCC), in 1992. Of the gases covered by
the treaty, the most important in terms of contribution to warming, are,
in declining order of emissions levels, carbon dioxide, methane, nitrous
oxide, and three types of synthetic (manufactured) gases.

In addition, scientists have recently intensified their efforts to study
the climate effects of substances not included in the Framework
Convention. According to a 2001 comprehensive review 1 of scientific
research on

climate change, additional substances* generally regarded as air
pollutants because they can damage human health and the environment* can
also affect the earth*s climate. Among the substances are the three
treated in this report, listed below. Of these three, sulfate aerosols
exert the greatest influence on climate.

 Sulfate aerosols are produced when sulfur dioxide gas is transformed
through oxidation 2 in the atmosphere into aerosol particles. (An aerosol
is a solid and/ or liquid particle suspended in the air.) Sulfur dioxide
is produced mainly by burning coal and petroleum products that contain
sulfur.

 Black carbon is a type of aerosol produced by the incomplete burning of
substances containing carbon. Significant sources include uncontrolled or
poorly controlled combustion of coal, diesel fuel, and biomass for heating
and cooking, and by the burning of fields and forests. Black carbon
emissions from these sources are accompanied by varying amounts of
particulate organic materials.

1 Intergovernmental Panel on Climate Change (IPCC), 2001. Climate Change
2001: The Scientific Basis. Contribution of Working Group I to the Third
Assessment Report of the Intergovernmental Panel on Climate Change.
Cambridge University Press, Cambridge, United Kingdom and New York, New
York.

2 Oxidation is a type of chemical reaction involving oxygen.

 Tropospheric ozone 3 is formed when nitrogen oxides react with certain
other chemicals in the presence of sunlight. Nitrogen oxides are produced
primarily by cars and other vehicles and by power plants that burn fuel to
generate electricity. On a global scale, methane and carbon monoxide are
also significant precursors to ozone.

You asked us to (1) assess the extent to which the scientific community
agrees on the climate effects of sulfate aerosols, black carbon, and
ozone, as reflected in the 2001 review, and identify important
developments since that review, and (2) identify trends in emissions and
concentrations of these three substances over the past 2 decades in the
United States and six other specified countries, identify projected
estimates in emissions and concentrations of these pollutants in all seven
countries over the next

decade, and determine each country*s actions to reduce these three
pollutants. In addition, you asked us to review the existing literature on
the effect of economic development on a country*s pollution levels to
determine whether, as some researchers have suggested, there is a
systematic connection between growth in income and emissions. As agreed
with your offices, we examined the United States and three other
economically developed countries (Germany, Japan, and the United Kingdom)
and three economically developing countries (China, India, and Mexico).
These countries were chosen because they have large economies with a high
potential to produce the substances we examined.

To obtain information on recent research relating to the climate change
characteristics of the three substances, we relied primarily on the Third
Assessment Report, the most comprehensive source on climate science. We
also contacted scientists in four federal agencies, who were recommended
by staff at the U. S. Climate Change Science Program, which coordinates
and supports government research on climate change. To learn about work
subsequent to the 2001 review, we reviewed published work recommended by
experts in the field. In obtaining data on emissions trends and
projections, we found that data from government and academic 3 Wherever it
is found, ozone is chemically the same, a molecule comprised of three
oxygen

atoms. Its effects depend on its location. In the earth*s upper atmosphere
(called the stratosphere), ozone is beneficial because it prevents
ultraviolet radiation* which is dangerous to human health* from reaching
the earth*s surface. However, at lower levels (called the troposphere), it
is harmful to human health. Ozone in the stratosphere also has impacts on
climate. It is formed by different means than ozone in the troposphere. We
do not discuss stratospheric ozone at length in this report because it is
produced mainly through natural (non- human- induced) processes. Unless
otherwise stated, when we refer to ozone, we are referring to tropospheric
ozone.

sources in the United States and the other six countries varied
considerably in terms of quality and availability. In cases where no other
estimates were available, we used results prepared by leading researchers
in the field. With respect to the types of policy measures reviewed, we
concentrated on regulatory measures and did not include research and
development programs, programs of a voluntary nature, emissions monitoring
requirements, or programs to disseminate information or educate the
public. We further focused on existing programs or programs already
authorized and excluded proposed programs. We also excluded the policies
and measures taking place at the sub- national level (state or province
level, for example), which are separate from, though sometimes

complementary to, national measures. For more information on how we
gathered information for this study, see appendix I.

Results in Brief The scientific community substantially agrees that black
carbon aerosols warm the atmosphere and cool the earth*s surface, while
ozone contributes

to warming the earth, and sulfate aerosols contribute to cooling it,
according to the 2001 review, other scientific literature, and discussions
with atmospheric scientists. However, scientists are uncertain about the
extent of these effects. They believe that the level of uncertainty
associated with these pollutants is moderate for ozone and high for black
carbon and

sulfate aerosols. While carbon dioxide and the other traditional
greenhouse gases generally contribute to temperature and other effects at
a global level, the three substances considered here operate on a
different scale, both in terms of time and geography. These three
substances can have effects over smaller distances and shorter time
frames. In other words,

their impacts tend to be more important locally and regionally, while
having a smaller influence globally. Because of relatively rapid removal
from the atmosphere, their impact may be felt in the short- term, as
opposed to over decades or centuries hence. However, the effects of these
substances are not limited to warming; these substances may also cause
local cooling or may change local precipitation patterns. Since the 2001
review, other research has added to scientists* understanding of the
effects

of black carbon. For example, air and clouds over the Indian Ocean (which
are polluted with black carbon, sulfates, and other aerosols) were found
to absorb the sun*s energy to a far greater extent than expected. These
results suggest that black carbon, the only one of these substances that
absorbs rather than reflects light, may play a more important role in
warming the atmosphere than was estimated in the 2001 review.

All seven countries are taking steps to reduce the amounts of the three
pollutants. In the United States and the other three economically
developed countries we studied, these efforts have been underway for
decades. For example, these countries limit emissions from power plants
that burn coal and other fossil fuels. They also regulate emissions from
automobiles and trucks. In these four countries, the amounts of the three
substances generally declined over the last 2 decades. For example, sulfur
dioxide emissions declined in all four countries and black carbon
emissions

declined in three countries. Although sulfur dioxide emissions are
expected to decline in all of these countries, we found no emissions
projections for black carbon for three of them. Although developed
countries have made progress in reducing domestic ozone concentrations,
global ozone concentrations are likely to increase, owing to rising
emissions of ozone precursors in other countries. In contrast, in China
and the other two developing countries, emission control efforts are more
recent, typically going back only a decade or so. As in the developed
countries, these countries also target power plants and motor vehicles to
control emissions. In the developing countries, the levels of the three
substances varied. Sulfur dioxide emissions decreased in two countries,
but black carbon emissions increased in two countries. We found limited
information on ozone concentrations in developing countries. Most
available data pertain to only a few major cities and is not nationally
representative. Similarly, we were unable to find projections for sulfur
dioxide and black carbon emissions for these countries. The quality of
data, especially for developing countries, is uneven.

The results of empirical and theoretical research on the effect of
economic growth on environmental pollution are inconclusive. This research
has examined the hypothesis that pollution initially worsens as an economy
grows, but then improves as economic growth continues and income rises.
Empirical studies, which analyzed historical data to find such a
relationship across pollutants, have had mixed results. Similarly,
theoretical studies, which sought to identify how economic growth

may affect environmental pollution, have produced various possible
explanations but reached no consensus. Researchers agree that improved
data and more detailed studies will be needed to identify how economic
growth affects environmental pollution. Also, researchers caution that

economic growth does not automatically lead to reduced pollution. They
explain that, while economic growth may be necessary to provide the
resources needed to protect the environment, it is not, by itself,
sufficient to reverse environmental degradation and that appropriate
environmental policies must follow.

Background Although the sun heats the earth*s surface, a large fraction of
the sun*s energy is reflected back into space by clouds, ground surfaces,
ice, and water. However, certain gases in the earth*s atmosphere, such as
carbon

dioxide and methane, trap some of the sun*s heat and prevent it from
returning to space. The trapped energy warms the earth*s climate, much
like glass in a greenhouse. Hence the gases that cause this effect are
often

referred to as greenhouse gases. In response to potential environmental
problems linked to the emissions of various heat- trapping gases, the
United States and many other nations in 1992 signed a treaty aimed at
limiting climate change induced by human activity. This treaty, called the
United Nations Framework Convention on Climate Change, seeks to stabilize
atmospheric concentrations of

greenhouse gases at levels that would prevent dangerous human interference
with the climate system. Under the 1992 convention, the United States and
other parties generally agreed to implement programs aimed at reducing
their emissions of greenhouse gases not covered by

another treaty, the Montreal Protocol. 4 The most important of these
warming gases, in declining order, are carbon dioxide, methane, nitrous
oxide, and three types of synthetic (manufactured) gases* sulfur
hexafluoride, hydrofluorocarbons, and perfluorocarbons.

4 The Montreal Protocol, ratified by the United States in 1988, aims to
reduce the use of substances that deplete stratospheric ozone. Among these
substances are chlorofluorocarbons, which are also potent greenhouse
gases.

In recent years, scientists have focused increased attention on the
climatic role of certain substances that are regarded as air pollutants
(because of their harmful effects on human health and the environment) but
are not covered by the Framework Convention or Montreal Protocol. These
substances are aerosols (including sulfate aerosols and black carbon) and
tropospheric ozone. Scientists have long recognized that these pollutants
can affect climate, but these pollutants were not included in the
Framework Convention. Sulfate and black carbon aerosols differ from
traditional greenhouse gases, such as carbon dioxide and methane, in two
key ways. First, unlike the traditional greenhouse gases, which are evenly
distributed throughout the atmosphere and have global impacts, the effects

of sulfate aerosols and black carbon are greatest near their sources,
although they can have global impacts. Second, whereas traditional
greenhouse gases can remain in the atmosphere for tens to hundreds, or
even thousands, 5 of years, sulfate aerosols, black carbon, and ozone
remain in the atmosphere for much shorter time periods. Figure 1 shows the
sources and estimated mean atmospheric lifetimes of various substances
having an impact on climate.

5 Sulfur hexafluoride and perfluorocarbons, which are man- made greenhouse
gases, have atmospheric lifetimes of several thousand years. They are not
depicted in figure 1.

Figure 1: Sources and Estimated Mean Atmospheric Lifetimes of Selected
Substances Affecting Climate 3b

6 3b

2 2

4 4

Coal Mine 4

Power 2

Plant 3a

5 6

3b 6

3a 2

3b 3b 2

6 6

5 CountyLandfill

4 Substance Major sources Mean atmospheric lifetime 1

1. Sulfate aerosols Combustion of coal and oil (power plants) Days to
weeks

2

Black carbon Incomplete combustion of fuels (diesel vehicles, forest
fires, certain

Days to weeks power plants, cook stoves)

3

Tropospheric ozone Produced in the atmosphere by reactions, in the
presence of sunlight

Days to weeks involving nitrogen oxides and volatile organic compounds,
including methane and carbon monoxide

3a

Nitrogen oxides By- product of combustion (vehicles, power plants)

Days to weeks

3b

Volatile organic compounds Vehicles, industrial processes, trees

Days to weeks

4

Methane a Wetlands, cattle and other ruminant animals, fugitive emissions
from coal mining, landfills

12 years

5

3. Nitrous oxide Agricultural soil management (application of
fertilizers), vehicles

114 years

6

4. Carbon dioxide b Combustion of carbon- containing substances, such as
combustion of coal, oil, or

50 to 200 years natural gas in power plants or gasoline in vehicles; also
from land- use changes

Source: Illustration prepared by GAO with portions using Art Explosion.
For sources of information on lifetimes and sources, see next page.

a Wetlands are a natural, as opposed to man- made, source of methane. We
list them here because wetlands are the largest single source of global
methane emissions. b The lifetime of carbon dioxide depends on rates of
absorption by oceans and vegetation.

Notes: For each substance, we depict only the most important sources.
Additional sources of emissions exist for most of the substances listed
above.

This graphic was prepared by GAO with lifetime data reported in IPCC*s
Third Assessment Report,

2001. Source data reported by EPA, National Air Quality and Trends Report,
1999; EPA, Inventory of U. S. Greenhouse Gas Emissions 1990- 2000; and
Elaine Matthews, *Global Methane Emissions: Historical Trends, Controlling
Factors, and Future Prospects,* in Air Pollution as a Climate Forcing:
Workshop Proceedings, May 2002.

 Sulfate aerosols are created when sulfur dioxide emitted from, for
example, coal- and oil- fired power plants, is oxidized in the atmosphere.
Atmospheric sulfate aerosols have been associated with significant effects
on public health and visibility impairment, and when they are deposited on
earth, they contribute to the acidification of lakes, streams, and
forests. Sulfate aerosol particles also have major effects on clouds,
where they provide additional nuclei around which cloud droplets form.
This can increase the cooling effect of clouds and may also increase the
life spans of clouds. Both developed and developing countries burn coal

to generate electricity, leading to emissions of sulfur dioxide.  Black
carbon, a type of aerosol, is a form of particulate matter and

results from the incomplete combustion of coal, diesel fuel, and biofuels
(such as alcohol or gasohol), and from open biomass burning, (i. e., the
burning of forests and agricultural residues). Because it is dark in
color, black carbon aerosol absorbs the sun*s energy, creating warming in
the

atmosphere and cooling at the earth*s surface, thus modifying climate (in
contrast to the warming caused by traditional greenhouse gases, which
prevent the earth*s heat from escaping into space). Black carbon is
generally released with other pollutants in different proportions.

 Tropospheric ozone is not emitted directly but is formed when emissions
of other pollutants, called precursors, react in the presence of sunlight.
Ozone precursors include nitrogen oxides (mainly nitric oxide and nitrogen
dioxide) and several carbon- containing substances, namely carbon
monoxide, methane, and non- methane volatile organic compounds. Nitrogen
oxides are produced primarily by motor vehicles, other combustion engines,
and electric power plants. Natural sources of nitrogen oxides are
lightning and biological processes in soils. Carbon

monoxide is formed when the carbon in fuels is not burned completely. It
is a product of motor vehicle exhaust and industrial processes. Natural
sources of carbon monoxide include wildfires. Methane is emitted by human
activities, such as coal mining, natural gas and oil

production, livestock production, rice cultivation, and waste disposal. It
also comes from natural sources, including wetlands, and some animals,
such as termites. Volatile organic compounds are produced by motor
vehicles, industrial processes using solvents, and in some cases, by
vegetation, including trees. 6

6 Isoprene and monoterpenes are examples of volatile organic compounds
produced by vegetation.

In reviewing the scientific information on these three substances, we
concentrated on the material covered in the most recent systematic
published review, the IPCC*s Third Assessment Report, which represents the
consensus of many climate scientists. 7 We also included some more
recently published material, notably the large- scale, multi- participant
study of aerosols over the Indian Ocean, known as the INDOEX study, which
was conducted in 1999. We included these results because they come from a
large, well- recognized, international program whose objectives overlap
substantially with many of the subject areas of this report.

The seven countries we reviewed differ greatly in terms of their
population, total area, and per capita income. For example, population
ranged from around 60 million in the United Kingdom 8 to nearly 1.3
billion in China; total area varied from just under 245,000 square
kilometers for the United Kingdom to 9.6 million square kilometers for the
United States; per capita income ranged from $2, 200 in India to $36,300
in the United States. See table 1.

7 IPCC*s Third Assessment Report, 2001. 8 The United Kingdom includes
Great Britain (England, Scotland, and Wales) and Northern Ireland.

Table 1: Comparative Statistics of the Seven Countries Reviewed Estimated
population

Tot al area Per capita income,

Country (2002) (in millions) (square kilometers) 2001 Economically
developed countries

United States 281.0 9, 629, 091 $36, 300 United Kingdom 60.0 244, 820 24,
700 Germany 83.3 357, 021 26, 200 Japan 127. 0 377, 835 27, 200

Economically developing countries

China 1, 284. 3 9, 596, 960 4,301 India 1, 045. 8 3, 287, 590 2,200 Mexico
103.4 1, 972, 550 9, 000 Source: GAO (table), Central Intelligence
Agency*s The World Fact Book, 2002 (data).

Notes: Some figures have been rounded. Estimated gross domestic product
per capita is based on purchasing power parity rates. Purchasing power
parity asserts that a unit of currency, such as a dollar, should be able
to buy the same bundle of goods in all countries.

In the 1960s, scientists determined that emissions of sulfur dioxide from
European power plants were causing the acidification of Scandinavian
lakes. Recognizing that air pollution does not respect national
boundaries,

34 countries, including Germany, the United Kingdom, and the United
States, signed the Convention on Long- Range Transboundary Air Pollution
(CLRTAP) in 1979. Under a subsequent protocol to this convention, the
signatories agreed to reduce their emissions of sulfur dioxide. Later,
they extended the convention to further reduce sulfur dioxide and to
reduce ozone precursors and various other pollutants. 9 There are now 49
parties to the convention.

In addition to commitments under this 1979 convention, several European
countries, including Germany and the United Kingdom, are bound by European
Union (EU) requirements to reduce emissions. For example, a 1996 framework
directive set broad goals for the consistent management of several air
pollutants, including sulfur dioxide, nitrogen oxides, and ozone, in
member nations. In 1999, a supplemental directive established a legally
binding limit on concentrations of sulfur dioxide and nitrogen oxides,

9 The United States is party to some, but not all, of the CLRTAP
protocols. Certain of the protocols extending the convention are not yet
in force.

among other substances, to be achieved by all member countries by 2005.
Another 1999 directive required EU countries to reduce the sulfur content
of liquid fuel. (More information on the various directives can be found
in apps. II, III, and IV.) Each EU member nation is required to transform
the

EU requirements into national legislation for domestic implementation. In
general, the EU emission reduction targets are more stringent than the
CLRTAP targets.

Scientists Agree on the According to the most recent comprehensive review
of scientific research

Overall Direction of on climate change, published in 2001, scientists
generally agree that sulfate

aerosols tend to cool the earth, while black carbon aerosols and ozone
tend the Three Pollutants*

to warm it. However, the extent of these effects is uncertain. Research
Climate Impacts,

published since 2001 has not changed these overall conclusions, but it
does but the Estimates

suggest that the scientific community*s understanding of these effects is
incomplete and needs further exploration.

of Impacts Contain Significant

The extent of the heating and cooling effects of various substances, as
compared to pre- industrial conditions, is typically expressed in watts
Uncertainties

per square meter, which is a measure of energy per unit area. Changes in
the balance between incoming and outgoing solar energy in turn heat or
cool the earth. Specifically, the earth receives 342 watts per square
meter of incoming solar radiation annually at the top of the atmosphere
and reflects about 30 percent back into space, resulting in a net input of
240 watts per square meter. If the climate were in balance, the same

amount of energy that the earth received would be emitted back into space
as infrared radiation. However, warming gases trap some of this outgoing
radiation, thereby changing the balance between incoming and outgoing
radiation. Water vapor is the most significant greenhouse gas; carbon
dioxide is the second most significant. Additional carbon dioxide added to
the atmosphere by human beings since the industrial era has contributed
another 1.46 watts per square meter averaged over the earth*s surface
annually, thereby further warming the climate. Figure 2 shows how the
average effects of the three pollutants we reviewed compare with the
climate effects of carbon dioxide and other conventional greenhouse gases.

Figure 2: Direct Effects of Several Substances on Climate Change as
Reported in the IPCC*s Third Assessment Report, 2001

Watts per square meter

Warming effect 1.8

1.6 1.4

1.46 1.2

1 0.8 0.6

.48 0.4

.34 .35

0.2 .15

.20 0 -0. 2 -0. 4

-. 40 -0. 6 -0. 8

Cooling effect -1

dioxide aMethane

oxide Synthetic

gases ozone

aerosols fossil

aCarbon aNitrous a, b from combustion

greenhouse Tropospheric dSulfate carbon fuel c dBlack Legend

High Best estimate Low Source: Intergovernmental Panel on Climate Change,
Third Assessment Report, 2001. a Estimated uncertainties for these
substances are plus or minus 10 percent. b Synthetic gases include
hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride. c Estimated
uncertainty for ozone is plus or minus 43 percent. d Please see notes
below for a discussion of the uncertainty surrounding sulfate aerosol and
black carbon. Notes: According to the IPCC, the level of scientific
understanding is low for sulfate aerosol and very low for black carbon
aerosol. The uncertainty estimates in the report are a factor of 2 for
each of these

substances. (Factor of 2 means, for example, in the case of sulfate
aerosol, the upper end of the range would be -0.2, which is half the
estimate* the estimate of 0.4 divided by factor of 2* and the lower end of
the range would be -0.8, which is twice the estimate* the estimate of 0. 4
multiplied by factor of 2.) Note that these uncertainty estimates are not
based in statistics, but rather on the range found in the recent
literature.

Positive values indicate a warming effect; negative values indicate a
cooling effect. The values for black carbon include only the burning of
fossil fuels, but not other sources, such as biomass burning, which is
estimated to make a similar- sized contribution to warming. Combustion of
these substances

also emits organic carbon aerosols, which contribute an opposite (cooling)
effect on climate. These are all direct effects. Indirect effects, such as
those operating through clouds, could increase the impacts of both
sulfates and black carbon. Note that these uncertainty estimates are not
based on statistical

analysis, but rather are subjective judgments based on ranges found in
reported studies. In addition, the values for these estimates are
described in the IPCC Third Assessment Report as having different levels
of scientific understanding associated with them: tropospheric ozone*
medium; sulfate* low; and fossil fuel black carbon* very low.

These three pollutants are relatively short- lived and are distributed
only locally or regionally, in contrast to the traditional greenhouse
gases, which persist for many years and are distributed worldwide. In
comparison, the effects of the short- lived substances must be averaged

over time and space.

Sulfate aerosols. According to the 2001 review, scientists generally agree
that sulfate aerosols contribute to cooling the earth. The uncertainty
regarding the climate effects of sulfate aerosols is significantly higher
than for tropospheric ozone. Because these aerosols are light colored,
they do

not absorb sunlight. Consequently, their effect is purely cooling, because
they reflect sunlight back into space and prevent it from reaching the
earth*s surface. This cooling phenomenon is referred to as a direct effect
on the climate. The total amount of sulfate aerosols in the atmosphere is
estimated to be about 10 times larger than the total amount of black
carbon aerosols discussed below.

Scientists have also identified indirect cooling effects of sulfate
aerosols that result from their effect on clouds. Like some other
aerosols, sulfates become the nuclei onto which water vapor condenses,
forming cloud droplets. There, they produce clouds composed of larger
number of smaller droplets, which result in two indirect effects on the
earth*s climate. First, smaller droplets tend not to coalesce as readily
into raindrops. Therefore, clouds composed of smaller droplets are less
likely to produce rainfall and will persist longer. Since clouds scatter
solar energy back out to space, they redirect energy away from the earth,
causing cooling. Second, since smaller cloud droplets scatter more
sunlight per mass than larger cloud droplets, even more solar energy will
be directed away from the earth. Because of both the lessened rainfall
from affected clouds and the changes in local heating of the earth, with
consequent reduction in evaporation,

sulfate aerosols can reduce the amount and change the distribution of
rainfall in affected areas.

Black carbon. According to the 2001 review, scientists generally agree
that black carbon aerosols contribute to warming the atmosphere. As with
sulfate aerosols, the uncertainty associated with black carbon aerosols*
warming effect is high. Much of the uncertainty about black carbon
aerosols* effects is due to questions about how these aerosols mix with

other types of aerosols and cloud droplets. In addition, black carbon is
released in association with other pollutants, such as organic carbon,
which has a cooling effect on climate. The proportions of each can differ
substantially among sources.

According to recently completed research on the effect of aerosols in the
atmosphere above the Indian Ocean, 10 large amounts of aerosols* including
some black carbon* in the air masses coming off the Indian subcontinent
lead to dramatic reductions in the amount of solar radiation reaching the
ocean*s surface and may be reducing precipitation over polluted areas.
While these results appear to be significant for a particular geographic
area and time period, they have yet to be translated into globally
averaged contributions to warming the earth*s surface. Nevertheless, they
suggest that these aerosols may have a larger effect on

warming than was previously recognized. 10 V. Ramanathan et al. *Aerosols,
Climate, and the Hydrological Cycle.* Science, 294, Dec. 7, 2001.

Tropospheric ozone. According to the 2001 review, most scientists agree
that tropospheric ozone 11 contributes to warming the earth. The level of
uncertainty associated with this warming effect is lower than the level
for sulfate aerosols and black carbon but is greater than for carbon
dioxide and other well- mixed greenhouse gases. However, ozone is not
uniformly distributed throughout the troposphere because it is produced in
a very uneven pattern in polluted areas and has a shorter lifetime than
most other greenhouse gases. As figure 2 shows, its estimated warming
effect is about one- quarter of the warming effect of carbon dioxide.

The formation of ozone in the atmosphere is complex. Most tropospheric
ozone is generated by gases, called ozone precursors, that are emitted by
industry, automobiles, and some natural sources, such as lightning and
soil. There are two main classes of ozone precursors: nitrogen oxides
(made up

of nitric oxide and nitrogen dioxide) and certain carbon- containing
gases, such as carbon monoxide and volatile organic compounds, including
methane. Recent research suggests that reducing methane could have a
greater effect in reducing ozone than previously recognized. 12,13 This
discovery is significant, since methane, unlike the other ozone
precursors, lasts in the atmosphere for as long as 10 years. (See fig. 1.)

11 Ozone in the stratosphere also has impacts on climate. It is formed by
different means than ozone in the troposphere. We do not discuss
stratospheric ozone at length in this report because it is produced mainly
through natural (non- human- induced) processes. Ozone in the troposphere
exists in two zones, the boundary layer and the free troposphere. The
significance of these zones is explained in the next section.

12 Arlene Fiore et al. *Linking Air Pollution and Climate Change: The Case
for Controlling Methane.* Geophysical Research Letters, 29( 19), 1919,
2002. 13 Michael Prather et al. *Fresh Air in the 21st Century?*
Geophysical Research Letters,

30( 2), 1100, 2003.

The Three Pollutants The seven countries we reviewed have all enacted
legislation and

implemented regulations to reduce emissions of sulfur dioxide 14 and black
Are Generally

carbon, and concentrations of tropospheric ozone. 15 For the most part,
the Declining in

levels of the three pollutants are declining in the four economically
Economically

developed countries and, to a limited extent, in the three economically
Developed Countries, developing countries.

but Not in Developing Our analysis of measures to control emissions and
concentrations of

Countries; All Seven these substances is organized by pollutant; for each
pollutant, we begin

with the economically developed countries and then turn to the developing
Countries Are Acting countries. Within the first group, we first discuss
the United States because

to Reduce Emissions we found the most complete information about it. We
next discuss the

United Kingdom, Germany, and Japan, in declining order of available
information. For economically developing countries, for similar reasons,
the order is China, India, and Mexico.

Sulfur Dioxide Emissions Of the three substances we reviewed, sulfur
dioxide was the most widely

Declined in Nearly All measured and regulated. Appendix II describes each
country*s regulatory

Countries; All Seven approach to sulfur dioxide emissions in greater
detail.

Countries Are Taking Steps to Reduce Them

Developed Countries Sulfur dioxide emissions have declined and are
expected to continue to decline in the United States, United Kingdom,
Germany, and Japan through at least 2010, owing to a combination of
explicit government policies designed to curb sulfur dioxide emissions,
the development of cleaner power generation and transportation
technologies, and a continuing transition in many countries away from
high- sulfur coal to low- sulfur

coal and natural gas. Figure 3 shows the decline in emissions for the
United States, the United Kingdom, and Germany between 1980 and 1999 14 In
this report, we use sulfur dioxide emissions as a proxy for sulfate
aerosols. This is because sulfate aerosols are the result of the chemical
transformation in the atmosphere of sulfur dioxide emissions, such as
those from power plants and other sources. It is difficult to attribute
sulfate aerosols in the atmosphere to individual countries, but such
attribution is possible with sulfur dioxide because many countries keep
track of their sulfur dioxide emissions.

15 Because ozone is not emitted directly, it is measured in terms of
concentrations.

and for Japan between 1990 and 1999, the only years for which we found
data for that country. As the figure shows, the greatest decline occurred
in Germany. In most of these countries, emissions declined more steeply
between 1990 and 1999 than between 1980 and 1990. Figure 4 shows projected
declines between 1990 and 2010 (1995 and 2010 for Japan). As the figure
indicates, the greatest relative decline is expected to occur in Germany.

Figure 3: Sulfur Dioxide Emissions in Four Developed Countries, 1980- 99
25,000 Thousand metric tonnes

20,000 15,000 10,000

5,000 0

1980 1981

1982 1983

1984 1985

1986 1987

1988 1989

1990 1991

1992 1993

1994 1995

1996 1997

1998 1999

Year

United States United Kingdom Germany Japan

Sources: GAO (graphic); data reported by governments to CLRTAP (U. S., U.
K., and Germany) and data reported by the Japanese government in Japan's
Third National Communication to the UNFCCC, 2002. Notes: A metric tonne is
equivalent to 1.102 short tons (or 2,204 pounds). We were unable to locate
data from Japan for 1980 through 1989.

Figure 4: Projected Sulfur Dioxide Emissions in Four Developed Countries,
1990- 2010 25,000 Thousand metric tonnes

20,000 15,000 10,000

5,000 0

1990 1995 1999 2005 2010 Year

United States United Kingdom Germany Japan

Sources: Prepared by GAO with data reported to CLRTAP (United States,
United Kingdom, and Germany) and data provided by Dr. T. Matsui, Japanese
National Institute of Environmental Studies (Japan).

Notes: Projections of U. S. sulfur dioxide emissions do not include recent
or proposed EPA rulemakings that are likely to decrease sulfur dioxide
emissions in the future. Values from 2000 to 2010 for the United States,
the United Kingdom, and Germany are based on 2010 projections.

Both the United States and European countries have health- based standards
designed to minimize damage to human health caused by sulfur dioxide
emissions. They also have annual emissions limits to control acidification
of the environment caused by these emissions. The United States set its
limits based on an across- the- board, 50- percent reduction in sulfur
dioxide emissions, relative to 1980, from power plants. In contrast, the
European governments set their standards using the *critical loads*

approach, taking into consideration the estimated potential impact of the
emissions on the environment. That is, the Europeans estimate, using
mathematical models, the maximum amount of damage that a particular
ecosystem* such as forests, lakes, and streams* could sustain before long-
term harmful effects occur. Standards aimed at reducing emissions to a
level near the critical load goal are then negotiated among countries.
This type of standard is often referred to as an effects- based standard.
We were unable to find information on how Japan developed its sulfur
dioxide emissions standards.

United States. U. S. emissions of sulfur dioxide decreased from 23.5
million metric tonnes to 17.1 million metric tonnes between 1980 and 1999,
a decrease of about 27 percent, according to U. S. data submitted to the
CLRTAP. The United States projects that sulfur dioxide emissions will
decline even further, to 15.1 million metric tonnes in 2010, representing
about a 36- percent decrease from 1980 levels (See fig. 4.) The decline in
emissions in 2010 may be even greater because U. S. projections take into
account only national policies but not state regulations. They also do not
include proposed new measures.

Sulfur dioxide emissions started to decline in the United States in the
early 1970s, after peaking at about 31 million tons. Federal regulation of
sulfur dioxide emissions essentially began with the Clean Air Act of 1970,
as amended in 1977 and 1990. The act required the Environmental Protection
Agency (EPA) to develop national air quality standards for air pollutants
that may endanger public health and welfare. EPA established such
standards for sulfur dioxide and several other pollutants. The act also
required each state to develop a plan (to be approved by EPA) for meeting
those standards. Under the act, all new or modified large power plants

could emit no more than a specified rate of sulfur dioxide per unit of
fuel consumed. Most new plants responded to this requirement by shifting
to coals with lower sulfur content.

Concern about sulfur dioxide emissions increased again in the late 1970s
and early 1980s, when scientists noticed that lakes and streams,
particularly in the Northeast, were becoming increasingly acidic, thereby
threatening aquatic life. This acidity was traced to sulfur dioxide and
nitrogen oxide emissions from power plants, primarily those located upwind
in the Midwest. The 1990 Clean Air Act Amendments imposed additional
controls on such emissions. One of the programs created under the
amendments was the Acid Rain Program, which employs emissions trading, a
market- based mechanism, to reduce sulfur dioxide emissions.

United Kingdom. According to data submitted to the CLRTAP, the United
Kingdom reduced its sulfur dioxide emissions from just under 4.9 million
metric tonnes in 1980 to about 1.2 million metric tonnes in 1999, a
decrease of about 75 percent. The majority of the reduction was due to an
increase in the use of nuclear and renewable energy, fuel- switching (e.
g., to natural

gas), improvements in efficiency, flue gas desulfurization, 16 and fuel
sulfur reductions. The United Kingdom projects that its sulfur dioxide
emissions will decline even further, from about 1.2 million metric tonnes
in 1999 to 0.6 million metric tonnes in 2010, an additional decrease of
nearly 50 percent. If realized, this decrease would represent an 87-
percent reduction from the 1980 level.

Sulfur dioxide emissions, along with other pollutants, contributed to
several major smog episodes in London during the first 6 decades of the
20th century, with the most significant one occurring in December 1952.
That episode took more than 4,000 lives over 5 days. It also led to the
enactment of legislation in 1956 and 1968 that aimed to reduce emissions
from households. A 1990 law gave the government the power to set emissions
limits and environmental quality standards for industrial plants. A 1995
law introduced a new framework for air quality policy, giving added
prominence to the concept of air quality standards.

In addition, the United Kingdom has international obligations to reduce
sulfur dioxide emissions. As a party to the CLRTAP, the United Kingdom
intends to reduce its annual emissions of sulfur dioxide by at least 80
percent by 2010 from its 1980 level. Furthermore, it must comply with EU
requirements to reduce sulfur dioxide emissions. (See app. II.)

Germany. According to data submitted under the CLRTAP, sulfur dioxide
emissions in the unified Germany declined by nearly 85 percent, from 5.3
million metric tonnes to 0.83 million metric tonnes between 1990 and 1999.
This decline resulted from such factors as the post- 1990 economic
restructuring, the retirement of outdated plants in the former East

Germany, and the use of less sulfur- intensive fuels. Germany reports that
it expects to reduce its sulfur dioxide emissions by about 34 percent
between 1999 and 2010.

16 Flue gas desulfurization equipment removes sulfur oxides from the
combustion gases of a boiler plant before it discharges them to the
atmosphere.

West Germany began to regulate sulfur dioxide in the late 1970s, when it
signed the CLRTAP. It participated in this effort in part out of concern
that sulfur dioxide- induced acidification was killing large numbers of
trees in the forests of southwestern Germany.

West Germany*s emissions of sulfur dioxide declined markedly during the
1980s, mainly because utilities expanded their use of natural gas to
generate electricity, installed flue gas desulfurization technology in
power plants, and substituted less sulfur- intensive fuels at power plants
and in industry. In contrast, emissions in the former East Germany rose
until 1987, mainly because utilities there used lignite (low- grade coal)
to generate electricity.

Germany*s primary legislative instrument to control sulfur dioxide and
other air emissions is a 1974 law, amended in 2000, that regulates
emissions from both large and small combustion facilities. Supporting
ordinances contain detailed regulations and emissions limits for all
facilities covered by the act. Germany is also reducing its sulfur dioxide
emissions under both the CLRTAP and EU directives.

Japan. According to the Japanese government, sulfur dioxide emissions
declined by about 9 percent between 1990 and 1999, or from 0.97 million
metric tonnes to 0.87 million metric tonnes. According to another source*

a researcher from the Japanese government*s National Institute for
Environmental Studies* sulfur dioxide emissions may decline by 27 percent
between 1995 and 2010. 17

Compared with other industrialized countries, particularly the United
States and Germany, Japan uses considerably less coal, relying instead on
nuclear power to generate one- third of its electricity. Nevertheless, in
1968, Japan began to regulate sulfur dioxide and other substances created
by fuel combustion. It set standards for emissions from power plants and
factories and provided for stations in several parts of the country to
monitor emissions of sulfur dioxide and other substances. In the late
1970s, the government required facilities to install scrubbers in their
smokestacks. Japan also reduced its sulfur dioxide emissions through gains
in combustion efficiency and a transition to low- sulfur coal.

17 Four scenarios with reductions ranging from 7 to 37 percent were
prepared by Dr. T. Matsui for the United Nations Environment Program. The
data for Japan in figure 4 show projected emissions reductions in 2010
from an intermediate scenario.

Developing Countries As in the developed countries, China and Mexico saw
an overall decrease in sulfur dioxide emissions during the 1990s, as shown
in figure 5. We were unable to find data for India. Sulfur dioxide
emissions in China declined by 15 percent between 1997 and 2000, in part
as a result of the combination of emission reduction policies and a
decline in coal use. However, emissions increased slightly after 1999.
According to Mexico*s National Greenhouse Gas Inventory, sulfur dioxide
emissions decreased by about 55 percent between 1990 and 1998, though they
increased very slightly between 1993 and 1998. We were unable to find
consistent historical data on sulfur dioxide emissions in India. We were
also unable to find data on projected emissions levels for any of these
three countries. According to U. S. experts, the quality of some of the
data for these countries is uncertain, due in part

to old measuring equipment and techniques.

Figure 5: Sulfur Dioxide Emissions in China and Mexico, Selected Years
25,000 Thousand metric tonnes

20, 000 15, 000 10, 000

5, 000 0

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 year

China Mexico Sources: GAO (graphic); data reported by the Chinese State
Environmental Protection Administration and the Mexican National
Greenhouse Gas Inventory, 1994- 1998. China. China is currently the
world*s largest emitter of sulfur dioxide.

It relies heavily on coal as an energy source, and the country*s sulfur
dioxide emissions rose initially along with rapid industrialization. More
recently, according to the Chinese State Environmental Protection

Administration, emissions of sulfur dioxide declined from 23.4 million
metric tonnes to 20 million metric tonnes between 1997 and 2000.

Although under its current 5- year plan (2001- 2005), China aims to reduce
coal consumption by increasing the share of natural gas and renewable
energy in the total energy supply, the U. S. Department of Energy*s Energy
Information Administration (EIA) projects that coal combustion in China
will increase 60 to 194 percent between 1999 and 2020, depending on
assumptions about economic growth. Thus, sulfur dioxide emissions could
also rise, unless implementation of a 1987 Air Pollution Control Law,
amended in 2001, can slow or reverse this trend. The law is designed to
improve air quality in large- and medium- sized cities through stiffer

penalties, better enforcement, and greater use of market- based methods,
such as the imposition of sulfur dioxide discharge fees. It also provides
incentives for using high quality, low sulfur coal and requires new or
expanded sulfur dioxide- emitting power plants and large- and mediumsized

enterprises to install sulfur dioxide scrubbing equipment.

India. We found limited data on India*s sulfur dioxide emissions.
Specifically, we found estimates from one source for 1980 and 1990, which
showed an 82- percent increase. We found an estimate from another source
for 2000 alone, which is higher than the 1990 estimate from the other
source. However, because these sources used different estimating methods,
their results may not be comparable.

We were also unable to find sulfur dioxide projections for India. However,
the EIA projects that India*s coal consumption will increase 9 to 62
percent between 1999 and 2020, depending on assumptions about economic
growth. It also notes that, because of shortages in generating capacity
and public funds, India will probably continue to rely on old, coal- fired
plants for some time, despite their contribution to the country*s air
quality problems.

Coal accounts for more than half of India*s primary fuel consumption, but
the sulfur content of the coal used is relatively low. Nevertheless, India
has undertaken some steps to reduce sulfur dioxide emissions from coal.
For example, it has improved the combustion efficiency of conventional
coal technologies and has promoted the use of renewable energy
technologies as an alternative to coal. It further adopted national air
quality standards for sulfur dioxide and other pollutants in 1982 and
revised them in 1994. India has also reduced the sulfur content of oil
products. According to the EIA, India*s high levels of pollution do not
result from a lack of effort in

building a sound system of legislation and regulation, but rather from
weak enforcement at the local level.

Mexico. According to the Mexican government, sulfur dioxide emissions
decreased by 67 percent between 1990 and 1992, but started to increase
gradually after 1992. Between 1990 and 1998, however, the net decrease was
55 percent. We were unable to find data on projected sulfur dioxide
trends. However, Mexico has considerably expanded its use of natural gas,
which produces less sulfur than coal, and according to a 2002 report by
the EIA, most new power plants in Mexico are likely to be gas- fired,
although some new coal- fired plants will also be constructed. EIA
projects that coal consumption will grow 62 to 115 percent between 1999
and 2020, depending on assumptions about economic growth. Most of Mexico*s
energy comes from oil, with coal providing only about 4 percent of the

country*s energy requirements. The basic law for reducing air pollution
emissions is the 1988 General Law of Ecological Equilibrium and the
Protection of the Environment. The law provides the framework for air
pollution standards for all major substances. Environmental protection
became a particularly important issue for Mexico in the early 1990s as a
result of negotiations for the North American Free Trade Agreement with
the United States and Canada. In 1992, the Mexican government created a
special office to enforce regulations. This office is charged with
inspecting facilities and issuing

penalties for noncompliance. According to Mexican government officials,
Mexico*s limited financial resources prevent full enforcement of
environmental regulations, despite steadily improving enforcement efforts.
Mexico has also introduced a federal tax incentive program for purchasers

of pollution control equipment. In addition to national legislation, some
air quality initiatives are underway in large cities, where urban air
pollution is a significant problem.

Black Carbon Emissions Scientists have begun to recognize the importance
of black carbon as an

Generally Declined in agent of climate change only within the past few
years. Consequently, most

Developed Countries and countries do not directly track emissions of this
pollutant. Therefore, to

conduct our analysis, we used a global black carbon database developed by
Generally Increased in atmospheric researchers. 18 This database has
several limitations. First, as Developing Countries

with most emissions inventories, estimates in this database are not based
on actual black carbon measurements, but rather are calculated using
information on countries* use of fossil fuel, which is measured, along
with estimates of how the fuel is used. Second, this database does not
contain

historical information on open biomass burning (forest burning or
landclearing), which may account for as much as 50 percent of black carbon
emissions. Finally, emissions estimates are based on limited information
about the characteristics of the fuels and technologies that produce the
emissions.

Black carbon emissions are particularly difficult to track because they
are often produced by activities that are informal and unregulated, and in
developing countries, there is considerable consumption of noncommercial
fuels, such as wood or animal waste. Since these fuels are not reported
the same way as fossil fuels, neither the amounts used nor

the emissions produced are well quantified. Because sophisticated emission
measurements have usually been available only in developed countries,
moreover, there are few measurements of the combustion that produces most
black carbon emissions in developing countries. For these and other
reasons, the black carbon emissions data are highly uncertain. Despite
these weaknesses, this database is currently the only source we found that
contained consistently estimated information on different countries*
emissions.

18 T. C. Bond and D. G. Streets, *Draft Global Black Carbon Inventory,*
2002. Dr. Tami Bond, Visiting Scientist, National Center for Atmospheric
Research, and Dr. David Streets, Senior Scientist, Argonne National
Laboratory, provided both data and commentary on this section.

Black carbon usually comes from the same sources as organic carbon, which
has a cooling effect on climate. It would be difficult to control
emissions of either substance separately; hence, it would therefore be
difficult to control warming by reducing black carbon emissions. Although
countries do not regulate black carbon directly, it is one component of
what regulatory agencies often refer to as particulate matter, 19 and most
of the countries we reviewed do regulate particulate matter. We therefore
collected information on measures to reduce particulate matter,
recognizing that this pollutant is an imperfect proxy for black carbon.

Furthermore, even when particulate matter emissions are reduced, black
carbon levels may not decline because some types of particulate matter,
such as sulfate, do not contain black carbon when emitted.

Developed Countries According to the database we used, the majority of
black carbon emissions in developed countries results from the combustion
of diesel fuel by vehicles, including both on- road vehicles, such as
heavy- duty trucks, and off- road vehicles, including farm and
construction equipment. As figure 6 shows, black carbon emissions from
fossil fuel combustion declined in three of the four developed countries,
more in the United Kingdom and Germany and less in the United States.
During this period they increased in Japan, starting in the early 1980s.
(See app. III for more detail on policy measures to reduce black carbon
emissions.)

19 Particulate matter is the general term used for a mixture of solid
particles and liquid droplets found in the air. It comes from vehicle
emissions, dust, fires, sea salt, and black carbon (soot) from wood and
coal burning. Particulate matter can be either coarse

or fine. Coarse particulate matter is referred to as PM 10 because the
particles have a diameter of 10 micrometers or less. Fine particles,
referred to as PM 2.5 , have a diameter of 2.5 micrometers or less. Black
carbon is a component of PM 2.5 , but this fraction may vary

across countries, depending on fuel sources. Secondary particles can be
formed in the atmosphere from gaseous emissions. For example, sulfates are
a form of particulate matter.

Figure 6: Black Carbon Emissions in the United States, United Kingdom,
Germany, and Japan, 1980- 96 500,000 Metric tonnes 450, 000 400, 000 350,
000 300, 000 250, 000 200, 000 150, 000 100, 000

50, 000 0

1980 1981

19 82

1983 1984

19 85

19 86

1987 1988

19 89

1990 1991

19 92

1993 1994

19 95

19 96

year

United States United Kingdom Germany Japan Source: GAO (graphic), T. C.
Bond and D. G. Streets (data) .

Note: Graphic based on global black carbon database prepared by T. C. Bond
and D. G. Streets for an article entitled, *A Technology- Based Global
Inventory of Black and Organic Carbon Emissions from Combustion,* to be
submitted to the Journal of Geophysical Research.

United States. According to the database we examined, black carbon
emissions in the United States were approximately 4 percent lower in 1996
than in 1980. However, there was a steady increase from 1992 to 1996.
According to this database, about one- half of black carbon emissions in
the United States are from the use of diesel vehicles to transport goods

over long distances and from off- road diesel vehicles. However, the
database may not fully reflect the effects of certain technologies that
were introduced in the 1990s to reduce diesel emissions. Including such
technologies in the database would likely show greater emissions declines

during the 1990s. Gasoline- fueled cars and wood combustion in home
fireplaces and stoves are other, smaller sources of black carbon
emissions.

The United States is the only country for which we found projections of
black carbon emissions. These were developed in support of an EPA
rulemaking 20 relating to large trucks. When the rule is fully implemented
in 2030, black carbon emissions are expected to decrease by an estimated
109,000 tons from the level produced in 1996. 21

The United States has several efforts underway to help reduce emissions of
black carbon and other types of particulate matter. Under the Clean Air
Act, EPA promulgated national air quality standards for particulate matter
in 1971 and has regulated particulate matter emissions from highway motor
vehicle engines. The most recent rule is designed to reduce emissions from
heavy- duty diesel vehicles by improving diesel engines and reducing the
sulfur content of diesel fuel. 22

United Kingdom. According to the database we used, black carbon emissions
from the United Kingdom declined by about one- third between 1980 and
1996. The sources of black carbon emissions in the United Kingdom are
similar to those in the United States, with the majority of emissions
produced by diesel vehicles. Other sources of black carbon emissions are
industrial coke- making 23 and coal- burning in the residential sector,
although residential coal use is declining in the United Kingdom.

The Parliament enacted legislation in 1956 and 1968 to control domestic
sources of particulate matter. The 1956 act aimed to control domestic
sources of smoke pollution by introducing smokeless zones (regions where
smokeless fuel had to be burned) and by making grants to homeowners to
convert their homes from traditional coal fires to heaters fueled by oil,
gas,

20 The 2002 Heavy- duty Diesel Engine Rule is aimed at reducing emissions
from heavy- duty trucks. 21 EPA*s estimate of black carbon emissions for
1996 differs from that found in the Bond and Streets database. This is
because estimates from the two studies are based on different assumptions.

22 The sulfur content of diesel fuel is important because sulfur can
impair the performance of a vehicle*s emissions- reducing device. 23 Coke
is a solid carbonaceous residue derived from low- ash, low- sulfur
bituminous coal. It is used as a fuel (and as a reducing agent) for
smelting iron ore in blast furnaces.

smokeless coal, or electricity. Legislation in 1990 and 1995 brought many
smaller emission sources under air pollution control by local authorities
for the first time. These acts also provided a new statutory framework for
local air quality management. In 1997 the United Kingdom published its
first national air quality strategy, which set air quality standards and
objectives for the pollutants of greatest concern, including particulate
matter. The

United Kingdom changed the particulate objective under this strategy in
2000, in response to a new EU directive and then in 2002 strengthened the
objective once more.

In the transportation sector, the EU in 1992 introduced directives
containing exhaust emission limits (generally referred to as the Euro I
standards) for new medium- and heavy- duty diesel engines. The standards
aimed to reduce emissions of particulate matter, as well as carbon
monoxide, hydrocarbons (including volatile organic compounds), and
nitrogen oxides, all ozone precursors. More stringent emission limits for
these vehicles, called Euro II, came into effect in 1996. Euro III limits
were adopted in 1999, and even more rigorous standards for these vehicles,
Euro IV and Euro V, are expected to take effect in 2005 and 2008,
respectively. The EU also set standards in 2001 for maximum allowable
levels on the sulfur content of diesel fuel. The directive, effective
January 1, 2005, will introduce sulfur- free diesel and gasoline in all EU
member states.

Germany. Black carbon emissions in Germany also declined by about one-
third between 1980 and 1996, according to the Bond and Streets database.
While diesel consumption and emissions increased rapidly during this time,
a phase- out of coal combustion for home heating led to an overall
reduction in black carbon emissions. Other large sources of black carbon
emissions in Germany* much smaller than diesel vehicles* are industrial
coking coal and gasoline vehicles.

Between 1990 and 1996, Germany decreased its emissions of particulate
matter by 86 percent. The decrease occurred primarily because of
developments in eastern Germany after reunification, when many older
industrial and power plants were closed or refitted with new technologies
that remove soot particles. In addition, many installations shifted to the
use of gas and liquid fuels* especially in small combustion appliances*
thereby producing less particulate matter. The Federal Emission Control
Act provides the framework for regulating all air pollutants, and its
ordinances govern both large and small combustion facilities.

Like the United Kingdom, Germany must abide by EU directives aimed at
reducing particulate matter emissions, including the Euro I* III
directives on diesel vehicle emissions. Most diesel vehicles currently
emit much less particulate matter than earlier models, but Germany is
continuing its effort to reduce emissions in the transportation sector.
For example, in 2001 Germany passed legislation to offer tax breaks for
sulfur- free gasoline and diesel fuel starting this year.

Japan. Black carbon emissions in Japan were about 60 percent higher in
1996 than in 1980, according to the database we used. The major source of
these emissions is diesel fuel, the use of which began to increase in
1988. As in the United Kingdom and Germany, coke- making could be an
additional source of black carbon emissions in Japan.

In June 2001, Japan*s legislature enacted a law to further tighten
particulate matter emissions from diesel- powered vehicles to improve air
quality in major urban areas. The law applies to 196 local governments in
Tokyo, Osaka, and four other cities.

Developing Countries The database we used indicates that black carbon
emissions increased between 1980 and 1996 in China and India, as figure 7
shows. It suggests that Mexico*s black carbon emissions are essentially
unchanged over this period. We found no projections of black carbon for
any of these three developing countries.

Figure 7: Black Carbon Emissions in China, India, and Mexico, 1980- 96
1,800,000 Metric tonnes 1, 600, 000 1, 400, 000 1, 200, 000 1, 000, 000
800, 000 600, 000 400, 000 200, 000

0 1980

1981 1982

1983 1984

1985 1986

1987 1988

1989 1990

1991 1992

1993 1994

1995 1996

year

China India Mexico Source: GAO (graphic), T. C. Bond and D. G. Streets
(data) . Note: Graphic based on global black carbon database prepared by
T. C. Bond and D. G. Streets for an article entitled, *A Technology- Based
Global Inventory of Black and Organic Carbon Emissions from Combustion,*
to be submitted to the Journal of Geophysical Research.

China. Emissions of black carbon in China rose by 43 percent between 1980
and 1996, according to the Bond and Streets database. Moreover, according
to that data source, China emits more black carbon than any other nation
in the world* approximately 29 percent of the global total. However, its
per capita emissions are not higher than those of other countries. These
emissions came primarily from coal (especially dirty soft coal) and wood
in the residential sector, coal- burning power plants using older
technologies, on- road and off- road diesel vehicles, and cokemaking
plants in the industrial sector. Emissions increased steeply in the 1980s,
but the growth rate slowed somewhat in the 1990s as China began to switch
from coal to cleaner natural gas and from raw coal to coal briquettes
(which produce fewer emissions) in the residential sector; it also closed
many small industrial coal plants.

Under amendments in 2000 to its Air Pollution Control Law, the government
set a goal of reducing *soot and flue dust* (particulate matter) emissions
to 1995 levels by 2010. According to the law, new or expanded power plants
and large- and medium- sized industrial facilities must install
particulate matter control equipment or take other measures to reduce
emissions. The city of Beijing requires the use of gas in place of coal in
new fuel applications.

In the transportation sector, China has implemented emissions standards
for diesel vehicles. In 2000 and 2001 the government introduced the Euro I
emissions standards for new cars and trucks. The standards, which apply to
the entire country, are based on those standards originally introduced in
Europe in 1992 and limit the amount the amount of particulate matter and
other substances that can be emitted from new diesel vehicles. More
stringent Euro II norms currently apply to Beijing and Shanghai and will
apply to the entire country after 2005.

India. According to the database we used, black carbon emissions in India
rose by just under one- third between 1980 and 1996. Most of this
country*s emissions come from the use of biofuel in the residential
sector, with diesel

vehicles contributing a smaller, but noticeable, fraction. Black carbon
emissions increased between 1980 and 1996, as the population grew and
burned more wood, dung, and agricultural waste for cooking and home
heating. 24 The Environmental Protection Act of 1982 set national
standards for the emissions of various substances. The standards were
revised in 1994. Revisions to the act in 1996 set fuel quality
specifications, including requirements for low- sulfur diesel. In the
capital city of New Delhi, 84, 000

public vehicles were converted from gasoline and diesel to compressed
natural gas, which emits negligible particulate matter. In 2000, the
Indian government introduced Euro I standards for private, non- commercial
vehicles throughout the country. Euro II norms currently apply to New
Delhi and will apply to the entire country after 2010.

Mexico. Black carbon emissions in Mexico remained fairly constant between
1980 and 1996, according to the database we used. Mexico is not a large
consumer of coal, instead relying primarily on oil as its key energy
source. Most of its black carbon emissions come from diesel fuel use.

24 Levels of emissions from biofuels are particularly uncertain because
data are so sparse. Estimates in the Bond and Streets database are
calculated based largely on a limited number of fuel use surveys combined
with socioeconomic data.

However, according to a Mexican government official, in rural areas,
villagers burn propane or biomass for home cooking; biomass produces black
carbon emissions. Older gasoline cars also produce black carbon emissions
in Mexico.

Trends in Surface Ozone The earth*s weather takes place in the lowest
layer of the atmosphere, Concentrations Are Mixed,

called the troposphere, which extends from the earth*s surface to between
but Background Ozone

9,000 and 16,000 meters above the surface. Within the troposphere, ozone
concentrations differ between zones, 25 the boundary layer, which extends
Levels in the Troposphere

from the earth*s surface to roughly 500 to 3,000 meters above the earth*s
Appear to Be Rising, With

surface, and the much larger free troposphere. (The height of the boundary
Implications for both Air

layer can vary by time of day and season: higher in the daytime and in
Quality and Climate summer, and lower in winter and at night.) Ozone in
these two zones has different durations and effects. There are important
interactions between the two zones.

Ozone in the boundary layer generally results from human activity, such as
transportation and fossil fuel combustion. Peak ozone episodes usually
occur in the summer months, under conditions of long periods of bright
sunshine, warm temperatures, light winds, and abundant ozone precursors.
Changing weather patterns contribute to yearly differences in ozone
concentrations from region to region.

Boundary layer ozone lasts only a few days over land, where it gets
deposited on surfaces. Over large bodies of water, such as oceans, it can
last longer, since there are no surfaces for deposition. At high
concentrations ozone can contribute to human respiratory problems and

plant damage. 25 Dr. Loretta J. Mickley, Research Associate, Atmospheric
Chemistry, Division of Engineering and Applied Sciences, Harvard
University, and Dr. Michael Prather, Fred Kavli Chair and Professor,
Department of Earth System Science, University of California Irvine,
provided insights and comments on this section.

The free troposphere is much larger than the boundary layer and extends
several miles above the boundary layer to the top of the troposphere.
Ozone in the free troposphere consists of some naturally occurring ozone
(such as ozone produced by lightning and ozone descending from the
stratosphere), as well as human- generated ozone carried upward from the
boundary layer by wind. Ozone in the free troposphere generally lasts
longer than ozone in the boundary layer* from 1 to several weeks. 26 In
the free troposphere, ozone, like other greenhouse gases, can trap surface
radiation and contribute to warming the earth.

Air is exchanged extensively between the boundary layer and the free
troposphere. Consequently, ozone pollution arising from the boundary
layer* particularly in the northern hemisphere* has contributed to
increased levels of ozone in the free troposphere. Hence, the troposphere*
the source of clean air at the earth*s surface* is showing an increasing
background level of ozone. 27 With the higher concentrations of ozone in
the free troposphere and in remote regions, more ozone can be blown into
populated areas, worsening the local pollution. Ozone pollution has also
been carried to the surface over remote regions, such as the oceans and
the Arctic.

Current estimates of ozone concentrations are based on profiles from ozone
balloons equipped with measuring devices (sondes). However, these sondes
are released from locations that are sparsely distributed around the
globe. Because the information from the sondes is so limited, we used two
types of proxy data to illustrate trends in the free troposphere, where
ozone can affect the climate. First, we used historical data on ozone at
the surface, which regulatory agencies, such as EPA, gather for air
quality purposes. These data are measured at a network of monitoring
stations, mainly in developed countries, and are collected primarily from
urban and suburban areas, where ozone is a major health concern. Second,
we used the results of a global modeling study that depicts ozone
concentrations in the free troposphere.

26 Ozone has a shorter life span in the boundary layer because processes
in that layer can destroy ozone, but these same processes do not occur in
the free troposphere. The processes include deposition and chemical
destruction at night.

27 There are various definitions of background ozone. As used in this
report, background ozone refers to ozone that is produced by human sources
as well as lesser amounts from natural precursor sources* such as volatile
organic compounds from vegetation or nitrogen oxides from lightning* that
travels into a given jurisdiction from elsewhere and is not associated
with local emissions.

Some developed countries have prepared projections of ozone concentrations
at the surface, but because ozone projections prepared for air quality
purposes do not adequately represent ozone increases in the free
troposphere, where it is important for climate, we also used the results
of a

modeling study from the Harvard University Atmospheric Chemistry Modeling
Group. 28 These model results are based on an IPCC scenario that assumes
that in 2025 there will be high population growth; significant income
disparities between developed and developing countries; continued
dominance of fossil fuels, including coal, in developing countries; and
some policy measures in place to control ozone precursors. We used these
results to represent annually averaged ozone concentrations in the free
troposphere over the entire globe in 1990 and 2025. Unlike regional- scale
air quality models, such as those used by regulatory agencies, the Harvard
model is able to project ozone concentrations in the free troposphere and
at a global level, which is of greatest interest for climate change
purposes.

Figure 8 shows calculated ozone concentrations at 5 kilometers (about 3
miles) above sea level for 1990, while figure 9 shows projected
concentrations in 2025. Both maps are based on the Harvard model. A
comparison of the two maps indicates that free tropospheric ozone levels
are expected to increase over the next two decades. Increased emissions of
ozone precursors in Asia lead to higher ozone concentrations aloft,

with possible consequences for climate change. 29 28 We use projections
prepared by Dr. L. J. Mickley of Harvard University*s Atmospheric
Chemistry Modeling Group. The Harvard model has been cited in the IPCC
Third Assessment Report, a peer- reviewed document. (The IPCC is the
premier scientific organization devoted to assessing climate change.) The
projections were produced using a general circulation (climate) model and
depict expected global average ozone concentrations in the free
troposphere in 2025. For comparison purposes, we also include a map
showing tropospheric ozone concentrations in 1990. The Harvard projections
are based on the IPCC Special Report on Emissions Scenarios (IPCC/ SRES)
A2 Marker Scenario. The Harvard model is able to capture in great detail
the physical and chemical processes leading to tropospheric ozone
formation and can also show the long- range movement of ozone and its
precursors.

29 Ozone levels are particularly low over most humid equatorial regions
because, over the humid tropics where nitrogen oxide emissions are
generally low, water vapor is involved in reactions that destroy ozone.

The most significant of the precursors in this scenario is likely to be
methane, 30 also a greenhouse gas, which is projected in the scenario to
increase globally by about 20 percent from its present level. Thus,
methane poses two problems: it can contribute directly to climate change
as a greenhouse gas, and it can indirectly contribute to climate change as
an ozone precursor.

Figure 8: Annually Averaged Global Ozone Concentrations at 5 Kilometers,
Parts per Billion, 1990 1990

Blue areas indicate low ozone concentrations Yellow and red areas i
ndicate high ozone concentrations

Source: L. J. Mickley, Harvard University.

30 Even though global emissions of methane appear to be slowing, it is not
clear that they will have dropped sufficiently to result in reduced
concentrations in the atmosphere.

Figure 9: Projected Annually Averaged Global Ozone Concentrations at 5
Kilometers, Parts per Billion, 2025 2025

Blue areas indicate low ozone concentrations Yellow and red areas i
ndicate high ozone concentrations

Source: L. J. Mickley, Harvard University.

Developed Countries Approaches to boundary layer ozone regulation in the
United States and Europe differ. The U. S. approach is almost exclusively
health- based. That is, its standards are designed to decrease prolonged
human exposures to ozone. By contrast, the European approach, as with
sulfur dioxide regulation, considers the cumulative effect of ozone
concentrations on

human health and the environment. It seeks to reduce these concentrations
below those levels that affect public health and that can cause long- term
damage to the environment. Since the environment can be impaired at lower
concentrations than can human health, ozone concentrations associated with
European goals are lower than in the United States. While the United
States has firm air quality standards for ozone, the EU has non- mandatory
target values for ozone concentrations but mandatory emission ceilings for
ozone precursors, arrived at after a process that takes both local ozone
formation and transboundary transport into

consideration. Neither the United States nor most European countries
consistently meet their ozone standards in polluted areas. We were unable
to find information on how Japan sets its ozone standard.

Cumulative ozone levels in the boundary layer have generally risen over
the past century* particularly because of ozone produced in the northern
hemisphere. However, some developed countries, such as the United States,
the United Kingdom, and Germany, have reported fewer

exceedances of their ozone standards over the past decade. That is, peak
ozone episodes, in which boundary layer ozone concentrations rise
substantially above naturally occurring levels, are becoming somewhat less
frequent and extreme in many developed countries. The governments
attribute the improvement principally to policy measures over the past
decade or so. However, weather conditions and other factors can affect
year- to- year changes. Figure 10 shows that the number of locations
exceeding their respective ozone standards declined by nearly 70 percent
in the United States and by nearly 90 percent in Germany between 1990 and
2000. We were unable to find comparable data for the United Kingdom and
Japan. (More detailed information on ozone policies can be found in app.
IV.)

Figure 10: Number of Areas Exceeding the Ozone Standard, United States and
Germany, 1990- 2000

120 Number of locations exceeding the standard 100 80 60 40 20

0 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 year

United States Germany Sources: GAO (graphic) data reported by the U. S.
EPA and the German Environment Office. Note: The U. S. ozone standard
trend depicted here is 0.12 parts per million averaged over 1 hour. The U.
S. also has an 8- hour ozone standard. The German ozone standard tracked
here is 0.055 parts per million averaged over 8 hours.

United States. Under the Clean Air Act of 1970, EPA was charged with
developing air quality standards for air pollutants that may endanger
public health and welfare. EPA established such standards for ozone and
nitrogen oxides, an ozone precursor, in 1971. In 1979 EPA revised the
ozone

standard to 0.12 parts per million daily maximum over a 1- hour period
that is not to be exceeded more than once per year on average. In 1997 EPA
tightened the standard to 0.08 parts per million averaged over 8 hours.
Although EPA has not yet begun to enforce the new 8- hour standard, it
does track concentrations in terms of this standard. According to EPA,
national ozone levels decreased 21 percent based on the 1- hour standard
and 10 percent based on the 8- hour standard between 1981 and 2000. For 52
metropolitan areas, the trend for 1- hour ozone levels improved between

1981 and 2000. However, beginning in 1994, the rate of improvement started
to level off, and the trend since then has been relatively flat.

The U. S. effort to control ozone has focused mainly on reducing emissions
of nitrogen oxides and volatile organic compounds, the two classes of
ozone precursors. The Clean Air Act requires each state with ozone

concentrations above the standard to develop a plan* known as a state
implementation plan* for reducing ozone formation; EPA must approve this
plan. This reduction can be attained through a mix of regulations in
various sectors, such as the utility, transportation, and industry
sectors* where most emissions occur. The ozone precursor methane is also
controlled under Clean Air Act regulations that require the combustion of
certain landfill gases from large landfills.

United Kingdom. According to United Kingdom government data, peak ozone
concentrations declined by 30 percent during the 1990s. Emissions of
nitrogen oxides declined by 42 percent between 1990 and 1999, while
emissions of volatile organic compounds, another ozone precursor, declined
by 34 percent between 1988 and 1999. The reductions in precursor

emissions are mainly due to stricter regulations, an increasing share of
vehicles fitted with catalytic converters (to control nitrogen oxides,
volatile organic compounds, and carbon monoxide), and reduced nitrogen
oxide emissions from power plants.

Incorporated into the United Kingdom*s framework for improving air quality
are several measures to address ozone formation. Many of these measures
were developed within the framework of the CLRTAP or the EU. For example,
in the transportation sector, implementation of the EU*s Euro I standards
limited emissions of the ozone precursors carbon monoxide, hydrocarbons
(including volatile organic compounds), and

nitrogen oxides from gasoline vehicles. More stringent standards came into
effect in 1997 and 1998, depending on vehicle type, and are known as Euro
II. These were superceded by Euro III standards for the majority of
vehicles in January 2001. A further tightening of the emissions limits,
referred to as Euro IV, will begin in January 2005 and will be fully in
force by January 2007.

Certain convention protocols also limit emissions of nitrogen oxides and
volatile organic compounds. The United Kingdom also has a domestic target
for ozone, which is more stringent than that of the EU.

Germany. According to the German government, peak ozone concentrations
have been declining since the mid- 1990s. Between 1990 and 2000, emissions
of nitrogen oxides declined by 40 percent, and emissions of volatile
organic compounds fell by 49 percent. The reductions were due

both to regulations* mainly in the transportation sector* and to economic
restructuring in the new states of eastern Germany.

Germany, like most other EU countries, has several measures in place for
reducing nitrogen oxides and volatile organic compounds, both ozone
precursors. These include emission- based motor vehicle taxes on heavy
utility vehicles and automobiles and requirements to install advanced
emissions reducing devices (that is, catalytic converters) on vehicles.
Measures in the utility and industry sectors will also increase the
efficiency

of fuel combustion to reduce emissions of nitrogen oxides. Germany is
bound by the same EU directives and CLRTAP protocols as the United
Kingdom.

Japan. According to the Organization for Economic Cooperation and
Development, ozone concentrations have increased in urban areas by about 5
percent since the late 1980s. However, according to Japanese data
submitted under the United Nations Framework Convention on Climate Change,
nitrogen oxide emissions increased by nearly 7 percent between 1990 and
1999, while emissions of volatile organic compounds decreased by just over
3 percent.

In addition to its basic air quality framework, discussed earlier, Japan
has several laws targeted at reducing ozone precursors. The 1968 Air
Pollution Control Law established standards for photochemical oxidants
(ozone) and other substances, including the ozone precursors nitrogen
dioxide and carbon monoxide. In 1992 the government introduced the
Automobile Nitrogen Oxides Law to tighten controls on nitrogen oxide
emissions from vehicles in areas where improvements in emissions were
difficult to realize with existing measures. Among other things, the law
regulates the types of vehicles that can be driven in areas where nitrogen
oxide emissions exceed the environmental standard. The Japanese government
has also set

emission standards for nitrogen oxides for each industrial facility. The
standards vary according to boiler type. Additionally, Japan*s air
pollution control law regulates volatile organic compound emissions from
motor

vehicles. Developing Countries According to the World Health Organization,
some of the poorest air

quality in the world, due in part to ozone pollution, is found in Beijing,
China; New Delhi, India; and Mexico City, Mexico. However, we were unable
to find national data on ozone concentrations for these three countries.
China and Mexico monitor ozone only in selected large metropolitan areas.
In Mexico City, ozone levels have declined slightly since the early 1990s.
We found no information on India. The IPCC reported that emissions of
nitrogen oxides* an ozone precursor* in East

Asia are increasing by about 4 percent per year. This suggests that ozone
levels may rise along with continuing industrialization in that region.

China. Vehicle emissions are one of the major sources of air pollution in
China*s major cities. The country currently has over 40 million vehicles,
and the number is growing by 10 percent annually; in large cities the rate
of growth is even higher. The Euro I vehicle emissions standards in place
around the country limit levels of carbon monoxide, hydrocarbons, and
nitrogen oxides. The Euro II standards, in place in Beijing, aim to
further reduce vehicle emissions in that metropolitan area.

Mexico. Efforts are underway to reduce emissions in the transportation
sector, particularly in Mexico City. Since 1993, the Mexican government
has increased its efforts to inspect motor vehicles. As of 2001, 230 new
car models had undergone emissions inspections. Another program reduces
the number of cars on the road in Mexico City and provides incentives for
the purchase of cars with lower emissions.

India. As in China, India*s Euro I and II performance standards for
automobiles are designed to help reduce emissions of key vehicle- related
ozone precursors.

Studies of the Effect Both empirical and theoretical studies on the
possible connection between

of Economic Growth economic development and environmental quality are
inconclusive overall. Empirical studies, which analyze historical data for
possible connections

on the Environment between economic growth and environmental quality, have
found that

Are Inconclusive emissions for some substances initially increase as
national income rises

and then decrease as a certain level of income is reached. However, these
results are not consistent across all studies and for all substances. 31
Similarly, theoretical studies, which seek to understand the relationship

between economic growth and environmental quality, do not agree on the
major factors underlying this relationship. While acknowledging a probable
relationship between economic growth and environmental quality, the
authors of these studies caution that economic growth does not
automatically result in environmental improvement. They explain that,
while economic growth may enable countries to pay for environmental
protection, growth is not by itself sufficient to reverse environmental

31 Carbon dioxide is not regulated as a pollutant in the United States.

degradation. See appendix V for more information on the studies we
reviewed.

Empirical Studies of the The empirical studies we reviewed did not
consistently find a relationship Relationship between

that showed pollution initially increasing as per capita income increases
Economic Growth and

and then starting to decrease when income rises beyond a certain level.
Environmental Quality Yield

However, such a relationship was found more often for some types of
pollutants than others. Mixed Results

If such a relationship between pollutants and economic growth is presented
graphically, it would form an *inverted U curve,* as shown in figure 11.
The point where the curve changes from an upward slope* pollution
increasing with income* to a downward slope is called the *turning point.*

Figure 11: Hypothetical Inverted U- Shaped Curve, Showing Relationship
Between Per Capita Income and Environmental Pollution

Turning point Environmental pollution

Per capita income

Source: GAO.

In conducting these studies, researchers typically used various measures
of environmental quality, such as a specific pollutant or a composite
measure of environmental quality. 32 In addition, to measure economic
growth, the studies commonly used per capita income, and in most cases,
the income levels were converted to 1985 U. S. dollars either by exchange
rates or purchasing power parity rates. 33 The per capita income level for
the United States for 1985 was $16,410 under both the exchange rate and
purchasing power parity methods; for Japan, it was $10,900 for the former
and $12,340 for the latter; for Mexico, $2, 180 and $4,745; and for China,
$280 and $785.

While overall the results of the studies are not consistent regarding an
*inverted U curve* relationship between pollution and economic growth,
they are more consistent in showing this relationship between pollutants

with localized and near- term effects, such as sulfur dioxide and
particulate matter. On the other hand, studies of substances with global
and long- term effects, such as carbon dioxide, sometimes did not find a
turning point or found a turning point beyond the income levels of the
countries in the study.

32 The source for the environmental data most often used in these studies
was the Global Environmental Monitoring System, compiled by the United
Nations, except for data on carbon dioxide emissions from the U. S. Oak
Ridge National Laboratory. Income data from different countries were often
adjusted to comparable units in terms of exchange rates or purchasing
power. In general, the data could be from as many as 149 economically
developing and developed countries for 1960 through 2000 or any year
during that period. Models differ in the exact specification of their
equations, such as the number and type of other factors that are included
in the model (e. g., international trade, population density)

and the mathematical form of the relationship tested. 33 To compare
incomes across countries, incomes are converted to U. S. dollars in one of
two ways: (1) using the official exchange rate between the dollar and the
other currency or (2) using purchasing power parity rates* an
international dollar that has the same purchasing power in another country
as the dollar has in the United States.

For example, as shown in figure 12, the estimated turning point for sulfur
dioxide in the studies we reviewed using the purchasing power parity
method was typically in the range of $4,000 to $11,000. 34 While these
estimated turning points were higher than per capita incomes in China and
Mexico, they were generally below the per capita incomes in Japan and the
United States in 1985. In addition, some estimated turning points for

particulate matter were in the range of $3,000 to $10,000, which is less
than per capita incomes in Japan, Mexico, and the United States. However,
not all the studies we reviewed found a turning point for pollutants with
localized effects. Specifically, one study found a turning point for
sulfur dioxide at a per capita income level far higher than any country*s
level in 1985, and another study did not find a turning point for
particulate matter. The studies of carbon dioxide we reviewed either
estimated a turning point

in the range of $10, 000 to $63,000, which is above the per capita income
level of most countries, except for a few developed countries, or found
that there was no turning point (for example, because emissions and per
capita incomes increased together).

34 All numbers are presented in 1985 dollars converted by purchasing power
parity.

Figure 12: Estimated Turning Points Found in Selected Studies of
Particulate Matter, Sulfur Dioxide, and Carbon Dioxide 120,000 Per capita
income 100,000

80,000 60,000 40,000 20,000

0 1

2 1

2 Shafik

Stern Cole- Cole- Panayotou

Schmalensee Selden- Selden- Study

PM SO2 CO2

United States Mexico Source: GAO. Note: Cole- 1 and Cole* 2 from Cole,
Rayner, and Bates, *The Environmental Kuznets Curve: An Empirical
Analysis,* Environment and Development Economics (1997)* estimates from
two models; Panayotou from Panayotou, Sachs, and Peterson, *Developing
Countries and the Control of Climate Change: Empirical Evidence,*
Discussion Paper #45, Harvard Institute for International Development
(1999); Schmalensee from Schmalensee, Stoker, and Judson, *World Carbon
Dioxide Emissions: 1950- 2050, *Review of Economics & Statistics (1998);
Selden- 1 and Selden- 2 from Selden and Song, *Environmental Quality and
Development: Is There a Kuznets Curve for Air Pollution Emissions?,*

Journal of Environmental Economics and Management (1994)* two models
estimated; Shafik from Shafik, *Economic Development and Environmental
Quality: An Econometric Analysis,* Oxford Economic Papers (1994); Stern
from Stern and Common, *Is There an Environmental Kuznets Curve

for Sulfur?,* Journal of Environmental Economics and Management (2001).

Researchers suggested reasons an *inverted U* relationship is found more
often for sulfur dioxide and particulates than for carbon dioxide. For
example, they noted that the possible costs of climate change due to
increased carbon dioxide emissions are borne globally and by future

generations rather than locally and currently. Furthermore, the awareness
of the problem of climate change is more recent than the awareness of the
health effects associated with sulfur dioxide and particulates; policies
to

control carbon dioxide emissions were generally not in effect during the
period of time analyzed by these studies.

Various Theoretical Other studies have sought to understand the factors
underlying the

Explanations Have relationship between economic growth and environmental
quality. These

Been Suggested for studies generally agree that income is a proxy for a
number of other

the Relationship of factors that may be influencing environmental quality
as countries develop

economically. These factors include, for example, changes in a country*s
Economic Growth and

economic structure, international trade, and a country*s preference for
Environmental Quality

environmental quality. Nevertheless, researchers do not agree on the
importance and role of any single factor. These three factors are
discussed below.

 Changes in a country*s economic structure. Some studies pointed out that
the relationship between economic growth and environmental quality
reflects changes in an economy*s structure as economies develop and is not
directly due to changes in income. Initially, these studies note,
economies are primarily agrarian and produce little pollution. As these
economies grow, the share of national output based on agriculture
decreases, while the share based on more pollutionintensive manufacturing
increases; hence pollution increases. At the later stages of development,
the share of national output based on manufacturing decreases, while the
share based on less

pollution- intensive services increases; hence, pollution decreases.

 The role of trade. Other studies noted that international trade can
affect patterns of production and environmental quality. That is, trade
allows economically developed countries to emphasize cleaner types of
industries and to rely on imports from less- developed countries for goods
produced by more polluting industries. As a result, the improvement in
some developed countries* environmental indicators is partly due to the
contraction of their more polluting industries and the transfer of these
industries to the less developed countries. However, researchers also
observed that this process* and consequent

improvement in environmental quality* cannot continue indefinitely because
the relocation of polluting industries to other countries cannot continue
indefinitely. 35

 Preference for environmental improvement. According to still other
studies, the relationship between economic growth and environmental
quality reflects a country*s preference for environmental improvement.
That is, environmental improvement could be described as a *luxury good,*
that is, a good that people will seek more of as their incomes grow beyond
subsistence level. Thus, in countries living at subsistence levels,
pollution is accepted as a side effect of economic development, and people
are not willing to reduce their consumption of basic necessities in order
to set aside resources for environmental protection. However, as a
country*s economy grows and incomes increase, people become more willing
to divert a portion of their resources from current consumption to improve
the environment. This economic growth, in turn, leads to stronger support
for environmental legislation and new regulations to protect the
environment.

Studies have also discussed other factors*- such as technology, population
density, political environment, and environmental regulations* that may
play key roles in shaping environmental quality as economies grow.
Regardless of their views, researchers generally agree that better data
and more detailed research are needed to conclusively identify the factors
that either directly, or indirectly through per capita income, influence
environmental quality.

35 The empirical studies we reviewed that examined the role of trade on
environmental quality did not provide support for the suggestion that
exporting polluting industries (sometimes called *environmental dumping*)
accounts for the observed reduction in some pollutants in developed
countries.

Conclusions Of the three substances we reviewed, sulfur dioxide emissions
have received the most attention in the countries we examined. All of
these

countries have undertaken at least some measures to reduce sulfur dioxide
emissions. Past trends and projections in all countries seem to be
affected by economic growth and health concerns. The economically
developed countries began this process much earlier* as far back as the
1970s or 1980s* and they have been more successful thus far in realizing
reductions than the three developing countries. In the developing
countries, sulfur dioxide emissions declined (though in China and Mexico
they have started to increase again), but they may decrease in the future
if new policies are implemented and well enforced. While data on sulfur
dioxide are far from complete, they are more readily available from
country sources than data on the other two substances, particularly in
developing countries. Since sulfate aerosol is a climate cooling agent, it
is likely that reductions in sulfur dioxide emissions will result in some
warming, at least at a regional level.

Black carbon is being addressed indirectly through measures designed to
reduce particulate matter in all of the developed countries and to a
lesser extent in the developing countries. Emissions have begun to decline
in developed countries, with the exception of Japan, according to

the database we used, largely as a result of regulations limiting diesel
fuel emissions, the major source of developed countries* black carbon.
Developing countries have not seen comparable declines in black carbon
emissions, because home heating and cooking largely rely on burning coal
and wood. Because small coal- or wood- burning stoves are widely used in
these countries, black carbon emissions are more widely dispersed than,
for example, sulfur dioxide emissions, which are usually associated with
large power plants. Consequently, developing countries may find it
challenging to control emissions of black carbon, at least for the
foreseeable future. In addition, forest burning and land- clearing, major
sources of black carbon emissions, are more prevalent in developing
countries. Reliable measurements of black carbon from all seven countries
are sparse.

Tropospheric ozone levels are difficult to reduce because they result from
emissions of precursor substances produced by a very diverse range of
sources. Nevertheless, developed countries have had some success over the
past decade in reducing high ozone levels, particularly in major urban and
suburban areas. This trend is likely to continue over the next two
decades, but ozone concentrations in developing countries may continue to

rise along with industrialization for the foreseeable future. The
developing countries we analyzed are only starting to take measures to
reduce ozone and its precursor substances. Consequently, ozone levels in
the free troposphere are likely to increase globally as a result of a net
increase in emissions of its precursors at the surface. Methane is
expected to play a

particularly important role in the formation of ozone in the future. The
results of economic research do not convincingly establish whether a
country*s environmental pollution initially increases and then, with
economic growth, decreases. This type of relationship seems to apply to
some types of pollutants but not to others. Researchers generally agree,
however, that unless the incentives facing producers and consumers change
with higher incomes, pollution will continue to increase as economies
grow. In other words, income growth, while a necessary condition, is not
sufficient to reverse environmental degradation. Environmental policies
must follow to induce appropriate responses and turn the pollution path
around.

Agency Comments We provided a draft of this report to the Secretary of
Energy and the Administrator of EPA for review and comment. The agencies
provided

written clarifying comments, which we incorporated where appropriate. As
arranged with your offices, we plan no further distribution of this report
for 30 days after the date of this letter, unless you publicly announce
its contents earlier. At that time, we will send copies of this report to
the Ranking Minority Members of the Committee on Energy and Commerce,
House of Representatives, and its Subcommittees on Energy and Air Quality
and Oversight and Investigations; the Secretary of Energy; the
Administrators of the Environmental Protection Agency, National
Aeronautics and Space Administration, and National Oceanic and

Atmospheric Administration; the Director, National Science Foundation; the
Director, Climate Change Science Program Office; and other interested
parties. We will make copies available to others upon request. In
addition, copies of this report are available at no cost at our Web site,
www. gao. gov.

If you have any questions about this report, please contact me at (202)
512- 3841. Key contributors to this report are listed in appendix VI.

John B. Stephenson Director, Natural Resources and Environment

Appendi Appendi xes x I

Scope and Methodology To obtain information on recent research relating to
the climate change characteristics of the three substances, we contacted
scientists in four federal agencies: the Department of Commerce*s National
Oceanic and Atmospheric Administration; the Department of Energy; the
National Aeronautics and Space Administration; and the National Science
Foundation. These scientists were recommended by staff at the U. S.
Climate Change Science Program, an interagency research coordinating body.

In analyzing trends for the three pollutants, we found that the
availability and quality of data varied considerably, especially in
developing countries. Except for countries that are members of the EU or
participate in the CLRTAP, governments are not required to report their
emissions of these substances internationally. 1 We found no standardized
system for

calculating and reporting emissions. Moreover, some of the data reported
here are based on direct measurements, while others are estimated using
proxy data (such as fuel use information), which may be less exact than
measured data. Most of the data used in this study, except where noted,
are taken from government sources. Dr. Tami Bond of the National Center
for Atmospheric Research; Dr. Loretta Mickley of Harvard University; Dr.
Michael Prather of the University of California, Irvine; and Dr. David
Streets of Argonne National Laboratory provided comments and insights

on certain sections of the report. The information on foreign countries*
emissions levels and legislation does not reflect our independent
analysis.

To obtain information on policies and measures, we first sought a
comprehensive source of information for each country. Because we found no
such source, we contacted government, academic, and other researchers and
analysts in the United States and the other countries, and the countries*
embassies in the United States. We also gathered information from
government publications, web sites, e- mail correspondence with U. S. and
foreign government officials, and discussions with embassy personnel.
While we tried to make this report as complete as possible, there may be
additional policies and programs underway that are not addressed here.

1 Under the Framework Convention on Climate Change, developed (Annex I)
countries generally report their emissions of sulfur dioxide along with
their emissions of the six conventional greenhouse gases. This is the
source of our data on Japanese sulfur dioxide emissions.

To assess the literature on the relationship between economic growth and
environmental pollution, we conducted computerized literature searches to
identify relevant articles. To help us determine which articles to focus
on, we sought guidance from recognized experts who specialize in this
field. The extent of governmental action to control a specific pollutant
is believed to be one important factor* but not the only factor* in
explaining the relationship between economic growth and emissions of that
pollutant. Therefore, even though few countries have acted to control
carbon dioxide emissions and have done so recently, we included studies
that examined the relationship between economic growth and such emissions.

We conducted our review between October 2001 and April 2003 in accordance
with generally accepted government auditing standards.

Programs and Measures to Reduce Emissions

Appendi x II

of Sulfur Dioxide Country Measures United States Section 109 of the Clean
Air Act requires EPA to establish National Ambient Air Quality Standards

(NAAQS) for air pollutants that may endanger public health and welfare.
EPA established such NAAQS for sulfur dioxide. Under the 1990 amendments,
areas not in attainment with the NAAQS must meet special compliance
schedules.

Section 110 of the Clean Air Act requires states to adopt plans, known as
State Implementation Plans (SIP), which detail the regulations a state
will use to implement, maintain, and enforce the NAAQS. EPA must approve
each SIP, and if a SIP is not acceptable, EPA may take over enforcement of
the Clean Air Act in that state. Section 111 of the Clean Air Act requires
EPA to establish nationally uniform, technology- based standards called
New Source Performance Standards for categories of new industrial
facilities, such as

power plants, steel mills, and smelters. These standards limit the amount
of certain pollutants, including sulfur dioxide, that may be emitted.

Sections 160- 169 of the Clean Air Act establish requirements for the
prevention of significant deterioration (PSD) of air quality in areas that
have attained the NAAQS. The act divides clean air areas into three
classes and specifies the increments of sulfur dioxide and particulate
matter pollution allowed in each. In order to receive a PSD permit, a new
or modified major source of pollution must show that it will not
contribute to a violation of the increments or of the national ambient air
quality standards and that it will use best available control technology
(BACT). This provision is referred to as PSD New

Source Review. Sections 171- 173 of the Clean Air Act establish pre-
construction permitting requirements for major new and modified sources in
non- attainment areas (areas that have not attained the NAAQS). To receive
a permit, such sources must, among other things, (1) obtain emissions
offsets, thereby assuring that reasonable progress toward attainment of
the NAAQS will occur, and (2) comply with the *lowest achievable emissions
rate.*

Title IV of the Clean Air Act created EPA*s Acid Rain Program, which caps
sulfur dioxide emissions from virtually all U. S. electric power plants at
8.95 million tons. Plant operators were required to reduce their emissions
through any combination of strategies, including installing scrubbers,
switching to natural gas or low- sulfur coal, or trading emissions
allowances. The first phase of the program ran from 1995 to 1999, and the
second phase, with more stringent caps, began in 2000 and will run
indefinitely. The program features a provision that allows power plants
that exceed their emissions targets to *bank* extra allowances during the
first phase of the program and then use these banked allowances during the
more stringent second phase.

United Kingdom The United Kingdom*s 1956 and 1968 Clean Air Acts, among
other things:  authorized local councils to set up smokeless zones and
make grants to householders to convert their homes from traditional coal
fires to heaters fueled by gas, oil, smokeless coal, or electricity.  set
limits on sulfur dioxide emissions from small power plants.  The United
Kingdom*s Environment Act of 1995 requires the government to produce a
national air quality strategy that identifies clear, measurable targets
for improved air quality in the United Kingdom. This strategy is to be
developed based on understanding of the health effects of the pollutants
concerned and costs of emission reduction methods and aims to improve air
quality by 2005. The strategy sets standards and objectives for sulfur
dioxide and seven other air pollutants. The 1995 act also established a
system of local air quality management, under which authorities are
required to assess the current and future quality of air in their areas
against the national air quality strategy objectives.

(Continued From Previous Page)

Country Measures

The Convention on Long- Range Transboundary Air Pollution (CLRTAP) binds
the United Kingdom to reduce sulfur, as do certain CLRTAP protocols:  The
1994 Oslo Protocol on Further Reduction of Sulfur Emissions, which aims at
gradually achieving critical loads of sulfur.  The 1999 Gothenburg
Protocol, signed but not ratified by the United Kingdom, which set
emissions ceilings for 2010 for sulfur dioxide and three other pollutants,
is expected to enter into force as early as 2003. (CLRTAP covers more
European countries than the EU, but the EU directives generally require
more ambitious emissions reductions than the CLRTAP protocol.)

EU directives which require the United Kingdom to reduce sulfur dioxide
emissions include:  The First Daughter Directive (1999/ 30/ EC), under
which EU members must establish, and achieve by 2005, a legally binding
limit on concentrations of sulfur dioxide and three other substances.

 The Directive on the Incineration of Wastes (2000/ 76/ EC), which sets
limits on emissions of sulfur dioxide and other substances from waste
incineration plants.  The Large Combustion Plant Directive (2001/ 80/
EC), which sets limits on sulfur dioxide and nitrogen oxides from
combustion plants with a thermal input of 50 megawatts or greater.

Germany  The Large Combustion Ordinance contains emissions ceilings for
new power plants in Germany.  The CLRTAP requirements and EU directives
also apply to Germany.

China The Air Pollution Control Law, enacted in 1987 and amended in 2000,
aims to improve air quality in key urban areas. Specifically, it 
broadens the scope of affected industries beyond industrial sources and
power plants, to include automobiles, ships, domestic heating, and cooking
stoves;

 provides an incentive for using high- quality, low- sulfur coal and
renewable energy;  allows so- called *priority cities* to designate zones
within which all burning of high- polluting fuel (i. e., coal) can be
prohibited and calls for the phase- out of a form of dirty coal in large-
and medium- sized cities;  requires new or expanded sulfur dioxide-
emitting power plants or large- and medium- sized industrial enterprises
to install desulfurization equipment; and  encourages cities to replace
individual household coal heating stoves with centralized district heat.

The Energy Conservation Law, which entered into force in January 1998,
promotes energy conservation and efficiency. Other energy conservation
laws also exist. A fuel tax has been imposed on high- sulfur coals, and
between January and September 2000, 4,732 mines producing high- sulfur
coal were closed.

Subsidies for coal have been greatly reduced since 1984. Source: GAO.

Programs and Measures to Reduce Emissions

Appendi x III

of Black Carbon or Particulate Matter Country Measures United States The
Heavy Duty Diesel Rule, promulgated in 2001, will require significant
future reductions in highway diesel engine particulate matter emissions.
It will also require diesel oil refiners to reduce most sulfur from diesel
fuel by 2006 in preparation for new engines in 2007. In 2030, when the
rule is fully implemented, it is expected that particulate matter from
diesel vehicles will be reduced by 130,000- 140, 000 tons per year
relative to 1996.

United Kingdom The Smoke Control Act of 1993 empowers local authorities to
declare a smoke control area if it appears that air quality standards will
not be met. Under the law, the local government can require that only
certain fuels be used for domestic heating. EU directives aimed at
reducing particulate matter include:  Directive 1998/ 70/ EC, which sets
the maximum allowable sulfur content of gasoline and diesel fuel.  The
First Daughter Directive (1999/ 30/ EC), which contains a particulate
matter standard for the EU countries.  The Directive on the Sulfur
Content of Certain Liquid Fuels (1999/ 32/ EC), which mandates reductions
in sulfur content of diesel fuel to enhance performance of emissions-
reduction devices.

 Directive 1999/ 96/ EC, which sets the emission limit values and
implementation dates in two stages for heavy duty vehicles (Euro III and
IV). The standards cover emissions of particulate matter and ozone
precursors.

Germany The EU directives described above also apply to Germany.

China Euro I and II standards for the control of emissions from diesel
vehicles.

India Euro I and II standards for the control of emissions from diesel
vehicles. Source: GAO.

Programs and Measures to Reduce

Appendi x IV

Ground- Level Ozone Country Measures United States The Clean Air Act has
resulted in the creation of several trading programs for reducing nitrogen
oxide emissions in the electric utility sector:

 EPA*s Acid Rain Program sets emissions rates for all affected utilities.
Unlike sulfur dioxide, there is no cap on total nitrogen oxide emissions,
but utilities may choose to over- control at units where it is easier to
do so and average these emissions with those at their other units, thereby
achieving overall emissions reductions at lower costs.  The EPA Nitrogen
Oxides SIP Call a requires 19 states and the District of Columbia to
reduce total nitrogen oxide emissions from utilities by a certain number
of tons each year; compliance for Phase I must be achieved no later than
May 31, 2004. Power producers subject to these regulations are allowed to
trade emissions allowances to meet the required limits.

 The Nitrogen Oxides Budget Trading Program, begun in 1999 in nine
Northeastern states, aims to reduce nitrogen oxide emissions during the
summer months to enable states to attain the standard for ground- level
ozone. Like the programs above, it is a cap and trade program, under which
total emissions are capped, and affected parties may trade emissions
allowances. The Clean Air Act has also provided the framework for ozone-
reducing reductions in the transportation sector. The most recent
regulation with significant impact on transportation sector ozone
precursors is the Tier 2 program, which was promulgated in 2000 and will
be phased in starting in 2004, when refiners must produce low- sulfur fuel
for passenger vehicle gasoline. Tier 2 also sets tailpipe emission
standards for all classes of

passenger vehicles, including sport utility vehicles and light- duty
trucks. A Clean Air Act regulation requires the combustion of methane and
other non- methane organic compounds from large landfills. The regulation
also contains a performance standard based on the allowable concentration
of methane measured at the landfill. In addition to programs regulating
emissions from cars and trucks, EPA regulates emissions of nitrogen oxides
and hydrocarbons from aircraft, ships, locomotives, recreational vehicles,
off- road diesel equipment (e. g., farm and construction equipment), and
spark- ignition engines, such as chain saws, lawn mowers, and forklifts.

The U. S. Department of Transportation administers a program called
*Congestion Mitigation and Air Quality Improvement* aimed at reducing
ozone and its precursors (as well as particulate matter) by funding new
transit services, bicycle, and pedestrian improvement, alternative fuel
projects, traffic- flow improvements, and other emissions- reducing
projects.

In the industrial sector, the Clean Air Act specifies performance
standards for new industrial sources. The standards, called New Source
Performance Standards, establish maximum emission levels for new or
modified major stationary sources, such as steel mills and smelters. These
standards also apply to power plants.

United Kingdom CLRTAP Protocols that bind the United Kingdom and other
European countries include:  The 1988 Sofia Protocol, which set a target
for emissions of nitrogen oxides.  The 1991 Geneva Protocol, which
requires a reduction in emissions of volatile organic compounds.  The
1999 Gothenburg Protocol, signed but not ratified by the United Kingdom,
which sets emissions ceilings for nitrogen oxides, volatile organic
compounds, and two other substances.

Country Measures

The EU directives aimed at reducing ozone and/ or its precursors include:
 Directives on Air Pollution by Ozone (92/ 72/ EC and 2002/ 3/ EC), which
establish thresholds for ozone and require that threshold exceedances must
be reported to the EU Commission and to the public.  The Directive on VOC
Emissions from the Storage of Petrol (94/ 63/ EC), which sets guidelines
for reducing volatile organic compound emissions from the storage and
distribution of petrol (gasoline) from terminals to

service stations.  The Framework Directive (96/ 62/ EC), which
established the framework under which the EU countries would agree on
emissions limits for certain pollutants. The Directive requires that, if
limits are exceeded, member states devise abatement programs to reach the
limits within a set deadline.  The Directive 98/ 69/ EC, which
establishes emission limit values and implementation dates in two stages
for light- duty vehicles (Euro III and IV). The standards cover ozone
precursors and particulate matter.  The First Daughter Directive (99/ 30/
EC), which sets limit values for nitrogen oxides (and other substances.) 
The VOC Solvents Directive (99/ 13/ EC), which limits emissions of
volatile organic compounds.  The Directive on Landfills (99/ 31/ EC),
which aims to harmonize controls on the landfill of waste throughout the
EU. Its main focus is on common standards for the design, operation and
aftercare of landfill sites. It also aims to reduce the amount of methane
emitted from landfill sites.

 The Large Combustion Plant Directive (2001/ 80/ EC), which sets limits
on sulfur dioxide and nitrogen oxides from combustion plants with a
thermal input of 50 megawatts or greater.

The National Emission Ceiling Directive (2001/ 81/ EC), which sets
ceilings for emissions of nitrogen oxides, sulfur dioxide, ammonia, and
volatile organic compounds to be attained by 2010. (As of early 2003, this
protocol was not yet in force.)

Germany The CLRTAP requirements and EU directives cited above apply to
Germany. Japan The Air Pollution Control Law requires stations in several
parts of the country to monitor for nitrogen dioxide, suspended
particulate matter, sulfur dioxide, carbon monoxide, and photochemical
oxidants. It also establishes maximum permissible limits on exhaust gases
from motor vehicles. The Automobile Nitrogen Oxides Law sets the
fundamental policies and plans for reducing the total volume of nitrogen
oxides for specific automobiles.

China Although the government does not require the reporting of data on
ozone concentrations, the city of Beijing does so when ozone levels become
particularly high.

Euro I and II standards for the control of motor vehicle emissions,
including carbon monoxide, hydrocarbons, and nitrogen oxides.

Mexico Mexico*s Tag Zero Program offers a 2- year exemption from Mexico
City*s *car- free* policy for drivers of clean cars. Under the program,
drivers of new cars or cars that have been upgraded with catalytic
converters may drive in the city any day of the week, while owners of cars
without such certification may drive on only a certain number of days per
week. (An exempted, or clean, car is denoted by a zero on a sticker placed
on the back window of the car. The car*s license plate indicates the days
a car may not be driven if it does not have a

sticker.) The Tag Zero program thus rewards the purchase of clean
vehicles.

India Euro I and II standards for the control of motor vehicle emissions,
including carbon monoxide, hydrocarbons, and nitrogen oxides. Source: GAO.

a The Nitrogen Oxides SIP Call is authorized under section 110 of the
Clean Air Act. A SIP is a State Implementation Plan, which is a proposal
submitted by each state to EPA containing emission limitations and other
control measures to attain, maintain, and enforce the NAAQS. EPA may issue
a SIP Call under the act when it finds that the applicable SIP fails to
comply with a requirement of the act. The SIP Call requires the state to
revise its SIP.

Summary of Results of Selected Studies on Economic Growth and
Environmental

Appendi x V

Pollution The following table presents information on the studies of
economic growth and environmental quality that we reviewed.

Table 2: Results of Selected Studies of Economic Growth and Environmental
Quality Estimated per capita income for turning points,

by type of emission a Study*s author( s) and year Particulate matter
Sulfur dioxide Carbon dioxide Based on exchange rates

Grossman and Krueger, *Economic Growth and Environment,* None found b $4,
100 Not studied

Quarterly Journal of Economics (1995) Holtz- Eakin and Selden, *Stoking
the Fires? CO Emissions and Not studied Not studied $35,400 c 2 Economic
Growth,* Journal of Public Economics (1995) Panayotou, *Demystifying the
Environmental Kuznets Curve: Turning a Not studied 5, 000 Not studied

Black Box into a Policy Tool,* Environment and Development Economics

(1997) Roberts and Grimes, *Carbon Intensity and Economic Development

Not studied Not studied None found 1962- 91: A Brief Exploration of the
Environmental Kuznets Curve,*

World Development (1997)

Based on purchasing power parity

Shafik, *Economic Development and Environmental Quality: $3, 300 3, 700
Not studied

An Econometric Analysis,* Oxford Economic Papers (1994) Selden and Song,
*Environmental Quality and Development: Is There a 9,600 10, 700

Not studied Kuznets Curve for Air Pollution Emissions?,* Journal of
Environmental

9,800 8,900 Economics and Management (1994)* two models estimated Cole,
Rayner, and Bates, *The Environmental Kuznets Curve: An

7,300 5,700

25, 100 Empirical Analysis,* Environment and Development Economics 8,100
6,900 62, 700 (1997)* two models estimated

Schmalensee, Stoker, and Judson, *World Carbon Dioxide Emissions: Not
studied Not studied 10, 000

1950- 2050,* Review of Economics & Statistics (1998) Unruh and Moomaw, *An
Alternative Analysis of Apparent EKC- type Not studied Not studied None
found Transitions,* Ecological Economics (1998) Panayotou, Sachs, and
Peterson, *Developing Countries and the

Not studied Not studied 12, 000 Control of Climate Change: Empirical
Evidence,* Discussion Papers #45, Harvard Institute for International
Development (1999)

Stern and Common, *Is There an Environmental Kuznets Curve for Not studied
101, 200 d Not studied

Sulfur?* Journal of Environmental Economics and Management (2001) Source:
GAO. a All numbers are in 1985 dollars unless otherwise noted. b Grossman
and Krueger estimated a turning point separately for heavy particulate and
smoke. While no turning point for heavy particulate was found, the turning
point for smoke was $6, 200.

c In 1986 dollars. d In 1990 dollars.

Appendi x VI

GAO Contact and Staff Acknowledgments GAO Contact David Marwick, (202)
512- 6775 Acknowledgments In addition to the individual named above,
Bernice H. Dawson, Richard A.

Frankel, Anne K. Johnson, Mehrzad Nadji, and Carol Herrnstadt Shulman made
key contributions to the report. Important contributions were also made by
Laura Yannayon and Katherine M. Raheb.

(360150)

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a

GAO United States General Accounting Office

Scientists generally agree that sulfate aerosols have a cooling effect on
climate, while ozone in the lower atmosphere has a warming effect. Black
carbon tends to warm the atmosphere but cool the earth*s surface. Sulfate
aerosols also affect how much and where it rains. Considerable uncertainty
remains about the size of these effects. All seven countries are taking
steps to reduce the amounts of the three

pollutants. The four economically developed countries have well-
established efforts underway. In these countries, the amounts of the three
substances generally declined over the last 2 decades and are expected to
decline over the next decade. In contrast, the three developing countries*
efforts are less well established. In these countries, the amounts of the
three substances generally increased during the years for which
information is available. GAO found few projections for these three
countries.

An extensive body of research has examined the possible connection between
economic development and environmental pollution, but the results of this
research are inconclusive. Researchers also caution that economic growth
by itself may help support environmental improvements but is not, by
itself, sufficient to ensure them.

Projected Average Global Ozone Concentrations, Parts per Billion, 2025

Solar radiation is absorbed by the earth and is subsequently reemitted.
The buildup of carbon dioxide and certain other gases in the earth*s
atmosphere traps some of that radiation. This is known as

the greenhouse effect and is believed to contribute to a warming of the
earth*s climate. Concerns are growing that, in addition to carbon dioxide
and other conventional

greenhouse gases, certain air pollutants may affect the climate.

GAO was asked to examine (1) the extent of agreement among scientists
regarding the effect on

the climate of three air pollutants* black carbon (soot), ground- level
ozone, and sulfate aerosols* and (2) seven countries* efforts to

control these pollutants, trends in these substances in these countries
over the past 2 decades, and estimates for the next decade. GAO was also
asked to summarize the relationship between economic growth and
environmental

pollution. The seven countries include four that are economically
developed* Germany, Japan, the United Kingdom, and the United States* and
three that are developing* China, India, and Mexico. These countries were
chosen because they have large economies with a high potential to emit
these pollutants. The two federal agencies asked to

comment generally agreed with the information presented in this report.

www. gao. gov/ cgi- bin/ getrpt? GAO- 03- 25. To view the full report,
including the scope and methodology, click on the link above. For more
information, contact John B. Stephenson at (202) 512- 3841. Highlights of
GAO- 03- 25, a report to

Congressional Requesters, House of Representatives

April 2003

CLIMATE CHANGE

Information on Three Air Pollutants* Climate Effects and Emissions Trends

Page i GAO- 03- 25 Air Pollutants and Climate Change

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Appendix I

Appendix I Scope and Methodology

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Appendix II

Appendix II Programs and Measures to Reduce Emissions of Sulfur Dioxide

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Appendix III

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Appendix IV

Appendix IV Programs and Measures to Reduce Ground- Level Ozone

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Appendix V

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Appendix VI

United States General Accounting Office Washington, D. C. 20548- 0001
Official Business Penalty for Private Use $300 Address Service Requested

Presorted Standard Postage & Fees Paid

GAO Permit No. GI00
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