[Senate Hearing 106-1115]
[From the U.S. Government Publishing Office]



                                                       S. Hrg. 106-1115

                   THE SCIENCE BEHIND GLOBAL WARMING

=======================================================================

                                HEARING

                               before the

                         COMMITTEE ON COMMERCE,
                      SCIENCE, AND TRANSPORTATION
                          UNITED STATES SENATE

                       ONE HUNDRED SIXTH CONGRESS

                             SECOND SESSION

                               __________

                              MAY 17, 2000

                               __________

    Printed for the use of the Committee on Commerce, Science, and 
                             Transportation



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       SENATE COMMITTEE ON COMMERCE, SCIENCE, AND TRANSPORTATION

                       ONE HUNDRED SIXTH CONGRESS

                             SECOND SESSION

                     JOHN McCAIN, Arizona, Chairman
TED STEVENS, Alaska                  ERNEST F. HOLLINGS, South Carolina
CONRAD BURNS, Montana                DANIEL K. INOUYE, Hawaii
SLADE GORTON, Washington             JOHN D. ROCKEFELLER IV, West 
TRENT LOTT, Mississippi                  Virginia
KAY BAILEY HUTCHISON, Texas          JOHN F. KERRY, Massachusetts
OLYMPIA J. SNOWE, Maine              JOHN B. BREAUX, Louisiana
JOHN ASHCROFT, Missouri              RICHARD H. BRYAN, Nevada
BILL FRIST, Tennessee                BYRON L. DORGAN, North Dakota
SPENCER ABRAHAM, Michigan            RON WYDEN, Oregon
SAM BROWNBACK, Kansas                MAX CLELAND, Georgia
                  Mark Buse, Republican Staff Director
            Martha P. Allbright, Republican General Counsel
               Kevin D. Kayes, Democratic Staff Director
                  Moses Boyd, Democratic Chief Counsel


                            C O N T E N T S

                              ----------                              
                                                                   Page
Hearing held on May 17, 2000.....................................     1
Statement of Senator Brownback...................................    25
    Prepared statement...........................................    28
Prepared statement of Senator Hollings...........................     3
Statement of Senator Kerry.......................................    20
Statement of Senator McCain......................................     1
Prepared statement of Senator Snowe..............................     4

                               Witnesses

Bradley, Dr. Ray, Department Chair, Department of Geosciences, 
  University of Massachusetts....................................    29
    Prepared statement...........................................    32
Christy, Dr. John R., Director, Earth System Science Center, 
  University of Alabama..........................................    36
    Prepared statement...........................................    38
Lane, Dr. Neal, Assistant to the President for Science and 
  Technology, Office of Science and Technology Policy............     4
    Prepared statement...........................................     7
Mahlman, Dr. Jerry, Director, Geophysical Fluid Dynamics 
  Laboratory, National Oceanic and Atmospheric Administration....    42
    Prepared statement...........................................    45
Trenberth, Dr. Kevin E., Director, Climate Analysis Section, 
  National Center for Atmospheric Research.......................    47
    Prepared statement...........................................    49
Watson, Dr. Robert, Chairman, Intergovernmental Panel on Climate 
  Change.........................................................    54
    Prepared statement...........................................    56

                                Appendix

Response to written questions submitted by Hon. John McCain to:
    Dr. John R. Christy..........................................    88
    Dr. Neal Lane................................................    89
    Dr. Jerry Mahlman............................................    92
    Dr. Kevin E. Trenberth.......................................    95
    Dr. Robert Watson............................................    98
Mahlman, Dr. Jerry, Director, Geophysical Fluid Dynamics 
  Laboratory, National Oceanic and Atmospheric Administration, 
  Science Magazine Article.......................................    85

 
                   THE SCIENCE BEHIND GLOBAL WARMING

                              ----------                              


                        WEDNESDAY, MAY 17, 2000

                                       U.S. Senate,
        Committee on Commerce, Science, and Transportation,
                                                    Washington, DC.
    The Committee met, pursuant to notice, at 9:31 a.m., in 
room SR-253, Russell Senate Office Building, Hon. John McCain, 
Chairman of the Committee, presiding.

            OPENING STATEMENT OF HON. JOHN McCAIN, 
                   U.S. SENATOR FROM ARIZONA

    The Chairman. Good morning. We meet today to examine the 
issues surrounding global warming. This subject continues to be 
an issue of great importance to the environment and the 
economic future of the country.
    To better prepare ourselves to objectively evaluate future 
legislative policy, the Committee will explore three issues: 
One, the underlying science behind global warming; two, exactly 
where we are in our research efforts; and, three, what does it 
all mean.
    For many years, scientists have been warning us about the 
greenhouse effect caused by man-made emissions of carbon 
dioxide and other gases, and the far reaching environmental 
consequences which could result if the problem is not properly 
addressed.
    A large amount of evidence has been presented to suggest 
that this phenomena is real and is due to the activity of man. 
However, there also has been evidence presented to contradict 
this conclusion.
    Earlier this year, the National Research Council concluded 
that the warming trend during the past 20 years is real, and is 
substantially greater than the average temperature of warming 
during the 20th Century. The report also identified a 
substantial disparity between satellite data trends and surface 
temperature trends as well.
    The Intergovernmental Panel on Climate Change also has 
issued a draft of its third assessment report which will, in 
all likelihood, suggests a warming trend when its final version 
is released early next year. These two reports, in addition to 
hundreds of other studies, outline the need for a more firm 
understanding of and scientific consensus on global warming.
    I would like to offer one brief example of global warming's 
potential harm. According to the United Nations Environment 
Program, the global average sea level has risen by 10 to 25 
centimeters over the past 100 years. It is likely that much of 
the rise is related to an increase in the lower atmosphere's 
global average temperature since 1860.
    Scientific models further project a rise in sea levels of a 
foot and a half by the year 2100. This projected rise is two to 
five times faster than the rise experienced over the past 
century. The impact of such movement on our coastal communities 
and businesses, such as fisheries, agriculture, and tourism, is 
unknown, but the consequences could be serious considering that 
half of the U.S. population lives in the coastal communities.
    We look forward to hearing more about the outlined reports 
and potential scenarios from our witnesses today, along with 
the new findings from the government's research efforts.
    Most importantly, any actions the United States takes in 
response to claims of global warming must be based on the best 
science available and not on rhetoric or political expedience. 
We must continue to invest in our research capabilities to 
fully understand the scientific interactions between humans, 
the land, the ocean, and the atmosphere.
    Testimony presented here today will serve as a valuable 
insight for this Committee. We hope to establish a baseline for 
the Committee on the current state of knowledge on the subject 
of global warming. And I welcome all of our witnesses who are 
here today.
    Before I ask Dr. Neal Lane, who is the Assistant to the 
President for Science and Technology of the Office of Science 
and Technology Policy, to begin his statement, I would like to 
make one additional comment.
    One of the great things about the requirements of the 
electoral process is extensive interaction with the citizenry. 
I just finished an unsuccessful, but very enlightening, 
adventure in that area.
    In town hall meeting after town hall meeting after town 
hall meeting, of which I had hundreds, young Americans stood up 
and said, ``Senator McCain, what is your position on global 
warming?'' There is a group of Americans who now come to 
political rallies with signs that say, ``What is your plan?'' 
``What is your plan,'' is the question that is asked.
    I do not have a plan. I am sorry to say that I do not have 
a plan because I do not have, nor do the American people have, 
sufficient information and knowledge. But I do believe that 
Americans and we who are policymakers in all branches of 
government, should be concerned about mounting evidence that 
indicates that something is happening.
    I do not pretend to have the expertise and knowledge on 
this very important and very controversial issue, but I do 
intend, beginning with this hearing and follow-on hearings, to 
become informed, to reach some conclusions, and make some 
recommendations, or make some non-recommendations depending on 
the information that I receive.
    I believe that it is of the utmost importance that we 
examine this issue thoroughly, and I am dedicated to that 
proposition. And I am very grateful that we have such a very 
well informed group of Americans who will appear before us 
today.
    [The prepared statement of Senator Hollings follows:]

            Prepared Statement of Hon. Ernest F. Hollings, 
                    U.S. Senator from South Carolina

    Mr. Chairman, thank you for holding this hearing today on global 
climate change, which I hope will be only one of many. It's been about 
3 years since our last full Committee hearing on climate change, so I 
welcome this opportunity to hear what the science can now tell us about 
this important topic. This Committee has worked hard to ensure that the 
federal government has the best research and information possible about 
global warming, as well as other types of climate changes. I'm glad to 
see our investments are bearing fruit and that we are identifying ways 
to focus our research to help us make decisions now and in the decades 
ahead.
    During the 1980s, a number of us here on the Committee became 
increasingly concerned about the potential threat of global warming and 
loss of the ozone layer. In 1989, I sponsored the National Global 
Change Research Act, which attracted support from many Members still 
serving on this Committee including Chairman McCain, as well as 
Senators Stevens, Inouye, and Gorton. In 1990, after numerous hearings 
and roundtable discussions, Congress enacted the legislation, thereby 
creating the U.S. Global Climate Research Program.
    When we passed the Global Change Research Act, we knew it was the 
first step in investigating a very complex problem. We placed a lot of 
responsibility in NOAA, the scientific agency best suited to monitor 
and predict ocean and atmospheric processes. We need to renew this 
ocean research commitment to ensure we better understand the oceans, 
the engines of climate. The so-called ``wild card'' of the climate 
system, the oceans, are capable of dramatic climate surprises we should 
strive to comprehend. In addition, the oceans are critical to our 
continued well-being. I am particularly interested that we pursue the 
questions covered by the recent NRC report, From Monsoons to Microbes: 
Understanding the Ocean's Role in Human Health. This excellent report 
tells everyone here--even those who don't live on the coast--that 
understanding our oceans is of the utmost national importance. The 
Oceans Act this Committee approved only a few weeks ago would go a long 
way to ensuring that we give priority to these important ocean research 
questions.
    I am glad to report that the research accomplished under the 
National Global Change Research Act has led to increased understanding 
of global climate changes, as well as regional climate phenomena like 
El Nino/Southern Oscillation (ENSO). We now have a better understanding 
of how the Earth's oceans, atmosphere, and land surface function 
together as a dynamic system, but we cannot stop there. Only recently, 
NOAA measured an important increase in temperature in all the world's 
oceans over a 40 year period. We need to understand the causes and how 
that will affect us. All this research ensures that federal and state 
decisionmakers get better information and tools to cope with such 
climate related problems as food supply, energy allocation, and water 
resources.
    While we have learned an astonishing amount about climate and other 
earth/ocean interactions in only a decade, we have other critical 
questions that require further research to answer. Many of these 
questions are relevant not only to improving our scientific 
understanding, but also to contributing to our future social and 
economic well-being. For example, climate anomalies during the past two 
years--most directly related to the 1997-1998 El Nino event--have 
accounted for over $30 billion in impacts worldwide. When impacts from 
the recent floods in China are included, these direct losses could rise 
to $60 billion. This most recent El Nino claimed 21,000 lives, 
displaced 4.5 million people, and affected 82 million acres of land 
through severe flood, drought, and fire. When we better understand the 
global climate system, and its relationship to regional climate events 
like El Nino, we may be able to find ways--such as improved forecasting 
and early warning--to avoid some of the severe impacts.
    Under current global warming scenarios, scientists predict a 6 to 
37 inch rise in sea level by the year 2100 that will put our coastal 
areas at an increased risk of flooding. This could have severe 
consequences for coastal states, such as mine, particularly if climate 
change has any bearing on the frequency or severity of hurricanes. 
While we have been in a pattern of infrequent hurricane landfalls along 
the East Coast, it is possible that recent severe storms signal a 
return to conditions similar to those of the 1930s, 1940s, and 1950s 
when huge storms were frequently making landfall. If so, and 
particularly if global warming increases our vulnerability to flooding, 
we must develop the science to better understand and respond to any 
environmental changes in weather patterns.
    I welcome our witnesses to discuss the current state of science on 
global climate change. I am anxious to hear about the progress we've 
made towards better understanding the complex temperature and 
precipitation pattern changes, and where our research efforts are going 
in the upcoming decade. I hope today's hearing will reinvigorate this 
Committee's leadership in promoting sound research on these important 
scientific questions.

    [The prepared statement of Senator Snowe follows:]

  Prepared Statement of Hon. Olympia J. Snowe, U.S. Senator from Maine

    Thank you, Mr. Chairman, for holding this timely hearing so that we 
can further understand the underlying science behind global climate 
variability from a distinguished group of internationally renowned 
scientists.
    Mr. Chairman, last spring, Maine had a first-of-its-kind conference 
specifically to debate and discuss the impact of potential 
environmental climate change with state, national and international 
experts. For two days, over 150 people explored many questions. Are we 
leaving a human fingerprint on the Earth's climate? Why has the average 
temperature in Lewiston--where the conference was held--increased 3.4 
degrees F. over the last century? Are we in a race against an 
uncertainty that none of us on this planet can afford to lose? And, if 
so, what do we need to do to establish a sound scientific basis for 
making state, regional, national, and international resource management 
and economic and policy decisions when considering global environmental 
change issues? The answers to these questions are complex, and our 
approach to them must continue to be through research and thorough 
analysis of the research results.
    It is important to continue to develop more accurate models led by 
common scientific research and thought so we might better predict what 
the impacts will be on plants and animals--including ourselves--under 
any changing climatic conditions. Concurrently, we must also evaluate 
the mitigation and adaptation strategies under consideration by policy 
makers in response to increasing amounts of atmospheric carbon dioxide 
and other greenhouse gases and possible environmental changes.
    The U.S. Forest Service has predicted that climate and pollution 
stresses from wild pests, humans, and other environmental changes are 
likely to cause unprecedented cumulative effects on our northern forest 
ecosystems and, by extension, on our economy and our culture. Our 
forests can largely adapt to environmental changes. But, over time, 
these forests could very well change in their composition, range, 
health, and productivity. Oak and conifers, for instance, could prevail 
over the maple dominated hardwood forests--diminishing the brilliant 
fall foliage for which New England is so famous.
    The fact is, the vast majority of international scientists say that 
something appears to be happening because of the excess of greenhouse 
gases in the atmosphere, and there is general agreement that human 
activities are affecting the global climate and thus affecting both 
land and sea.
    As Chair of the Oceans and Fisheries Subcommittee, I have 
introduced the Coral Reef Conservation Act, along with you, Mr. 
Chairman, in an effort to protect, sustain, and restore the health of 
coral reef ecosystems. In 1998, coral reefs around the world appeared 
to have suffered the most extensive and severe bleaching damage and 
subsequent mortality in modern times. Reefs in at least 60 countries 
were affected, and in some areas, more than 70 percent of the corals 
died off. These impacts have been attributed to, among other factors, 
the warmest ocean temperatures in 600 years. We must increase our 
efforts to protect these coral reefs, which are among the world's most 
biologically diverse and productive ecosystems.
    Again, Mr. Chairman, I thank you for holding this hearing on the 
science of global warming, and thank you for assembling such a 
distinguished panel today to share their vast expertise with us.

    The Chairman. Dr. Lane, thank you and welcome, and thank 
you for all the outstanding work you have done in the past and 
are presently doing.

  STATEMENT OF DR. NEAL LANE, ASSISTANT TO THE PRESIDENT FOR 
SCIENCE AND TECHNOLOGY, OFFICE OF SCIENCE AND TECHNOLOGY POLICY

    Dr. Lane. Thank you very much, Mr. Chairman.
    And I want to thank you, Senator Hollings, members of the 
Committee, for holding this hearing, and for giving me and also 
my colleagues, who are the experts in this matter, a chance to 
talk to you today about the state of knowledge of climate 
change, and about our Federal agency research program.
    The U.S. Global Change Research Program continues a strong 
bi-partisan tradition of support for this scientific endeavor. 
And it began with President Reagan, continued through President 
Bush's Administration, and on to the Clinton/Gore 
Administration.
    I would ask that my written testimony be included for the 
record.
    The Chairman. Without objection, the entire statement of 
you and the other witnesses will be included in the record.
    Dr. Lane. Thank you. I will summarize three issues in my 
oral statement very briefly: First, what we know about the 
Earth's climate and how it is changing; second, the remaining 
difficult scientific questions that we must address; and 
finally, how our research program is going after these issues.
    Let me start with the area of scientific consensus. First, 
human activities has significantly increased atmospheric carbon 
dioxide. In the past century, atmospheric CO2 has 
risen 30 percent. The concentration of carbon dioxide is now 
higher than at any time over the past 420,000 years.
    Second, the surface of the Earth is warming. The Earth's 
surface has warmed significantly over the last century. The 
oceans are warming as well, and evidence is strong that the 
temperatures of the late 20th Century are without precedent in 
the last several centuries, the 1990's are the warmest decade 
on record, and 1998 was the warmest year in 1,000 years.
    Third, the Earth's global average surface temperature will 
continue to rise during the next century. Greenhouse gases in 
the atmosphere will increase the surface temperature of the 
Earth. Global temperatures are projected to increase two to six 
and a half degrees Fahrenheit over the next 100 years.
    Rising temperatures will increase rates of evaporation and 
lead to more total precipitation. Sea level will rise as 
warming expands the ocean water. Finally, these changes in 
temperature, precipitation, and sea level will affect the 
natural environment and human society.
    The ideal ranges for plants and animals will change, and in 
some cases the effects of other environmental stresses and 
urban and rural areas will be amplified.
    Let me now move to the areas of remaining uncertainty. The 
key questions I think are: How fast will temperatures change 
over the next century, and how will the impacts of this change 
vary across different regions of the world?
    Differences in future climate projections largely stem from 
disagreements over so-called feedback effects. For example, 
will more water in the atmosphere increase warming by acting as 
a greenhouse gas, or result in more low clouds that will 
reflect sunlight away from the Earth? Will aerosols, small 
particles, reflect incoming sunlight, or will they absorb heat 
and contribute to warming effects?
    We do not know the exact answers to these questions, but 
our estimates of future average temperature increases in the 
range of two to six and a half degrees Fahrenheit include all 
of these uncertainties.
    We know the amount of carbon dioxide the global biosphere 
takes up and releases each year varies widely, but we do not 
know why. And although evidence suggests that plants and 
vegetation in the northern hemisphere are currently taking up 
substantial amounts of carbon dioxide, we do not know whether 
this capacity can be maintained or even increased over the long 
term.
    And though we often discuss global climate change, many 
important policy questions will have a regional focus. For 
instance, how will climate change affect rainfall in the 
southwest, fisheries in the northwest, or the distribution of 
maple trees in the northeast? We need to know how these changes 
will affect agriculture, tourism, and local economies.
    Finally, Mr. Chairman, I would like to comment on our 
efforts to answer these questions. Federal agencies that 
participate in the U.S. Global Change Research Program conduct 
research on the mechanisms of the Earth's climate system, on 
the future course of climate change, and the potential impacts 
of climate change on the environment and human society.
    The research agenda for the Global Change Research Program 
has been developed in cooperation with the scientific 
community, including the National Academy of Sciences.
    Over the last decade, the Global Change Research Program 
has had a strong focus on the physics and chemistry of the 
atmosphere and the oceans, including reducing uncertainties 
about the rule of aerosols and water in the atmosphere.
    Recently, the Global Change Research Program has broadened 
its scope, and I would like to highlight three new priorities. 
First, we are completing the first U.S. national assessment of 
the potential consequences of climate variability and change.
    This assessment is examining the potential ecological and 
socioeconomic impacts of climate variation and change in the 
United States and the ways we might prepare for them.
    Second, our new carbon cycle science initiative will 
evaluate the potential for the Earth's forests, the agriculture 
regions, and wetlands, to take up and store carbon.
    And finally, new research under the Global Change Research 
Program umbrella will focus on how water moves through the 
land, the atmosphere, and the ocean, and how climate change may 
increase or decrease regional availability of this critical 
global resource.
    Mr. Chairman, I thank you again for the opportunity to 
testify today. Your sponsorship of the Global Change Research 
Seminar Series clearly shows your interest in climate science. 
And I am confident that together we can continue to increase 
our understanding of these important issues that will help us 
make sound policy decisions for our nation.
    I will be happy to answer any questions you have.
    The Chairman. I thank you, Dr. Lane, and I did read your 
entire statement which I think is very illuminating.
    [The prepared statement of Dr. Lane follows:]

  Prepared Statement of Dr. Neal Lane, Assistant to the President for 
    Science and Technology, Office of Science and Technology Policy

    Thank you for this opportunity to discuss with you the 
Administration's science and technology programs that are relevant to 
the understanding of climate change. I know the Members of this 
Committee share my strong belief that America's world-leading science 
and technology enterprise must be sustained and nurtured. While we 
sometimes differ on precisely how and where to invest our taxpayers' 
funds, we share a bipartisan understanding that the future prosperity 
of this country depends on continued strong federal support for all 
areas of scientific inquiry.
    Today I come before you to suggest that we can bring that same 
common appreciation for science to an area of considerable policy 
disagreement--the issue of climate change. Whatever your policy views 
may be on the wisdom of the Kyoto Protocol, I respectfully suggest that 
supporting scientific research on climate change and its potential 
impacts is in our national interest. The President's FY2001 budget 
requests substantial funding for the U.S. Global Change Research 
Program, as has every budget submitted by this Administration and those 
of President Reagan and President Bush. I hope that Congress sees fit 
to continue the bipartisan tradition of strong support for this 
scientific endeavor, which is providing the sound, objective 
information we need to support decision-making in the public and 
private sectors.

The Science of Climate Change
    I would now like to summarize what we know about the Earth's 
climate and how it is changing. In 1995, the Second Assessment Report 
of the Intergovernmental Panel on Climate Change (IPCC) reviewed all of 
the science then available. Through the IPCC process, leading 
scientists from more than 150 countries periodically review and assess 
scientific information about climate change and its environmental and 
economic effects. The report documented a series of changes that had 
already occurred, including increases in greenhouse gas concentrations, 
an unusually rapid increase in temperatures, and rising sea levels. It 
explained that the magnitude, timing, and geographic pattern of 
observed temperature changes closely matches the changes that models 
project from human activities, and does not match well with model 
simulations of natural change or changes seen in the natural record. 
The Report famously concluded: ``The balance of evidence suggests that 
there is a discernible human influence on global climate.''
    The qualified nature of the IPCC attribution statement reflected 
the existence of alternative interpretations of parts of the data and 
known shortcomings in models of how the climate system works.
    Recently, however, important scientific evidence has emerged that 
has substantially undercut many of potential dissenting arguments, 
thereby fundamentally changing the debate over global warming. 
Basically, the debate has changed from ``Are we warming the Earth?'' to 
``How much are we warming the Earth?'' To understand the current state 
of climate change science, let me first start with a series of 
statements that virtually all credible atmospheric scientists agree 
with.
    1. The atmospheric concentration of CO2 has been 
significantly increased by human activities. In the past century or so 
the CO2 concentration has risen from less than 280 parts per 
million by volume (ppmv) to about 365 ppmv, an increase of about 30 
percent. At 365 ppmv, CO2 is now higher than at any time 
over the past 420,000 years. It is universally recognized that human 
activity is responsible for this increase, mainly through fossil fuel 
combustion and deforestation. Our best estimates show that unless 
action is taken to reduce CO2 emissions, atmospheric carbon 
dioxide levels will likely reach about 700 ppmv by the end of the 21st 
century, about double current levels. Other greenhouse gases, such as 
nitrous oxide, methane, and halocarbons (CFCs and HFCs), have also 
increased due to human activities and further increases over the 21st 
century will add to the tendency for global warming.
    2. The surface of the Earth is warming. There is now near unanimous 
agreement, including most of the climate skeptics, that the Earth's 
surface has warmed significantly over the last century.

   A recent National Research Council report (``Reconciling 
        Observations of Global Temperature Change'') carefully examined 
        direct measurements of surface temperature. The report 
        concluded that ``The warming trend in global-mean surface 
        temperature observations during the past 20 years is 
        undoubtedly real and is substantially greater than the average 
        rate of warming during the twentieth century.'' These data show 
        that the surface of the Earth has warmed by 0.4-0.7 degrees C 
        (0.7-1.4 degrees F) over the last 100 years, with 0.2-0.4 
        degrees C (0.4-0.8 degrees F) of that coming in just the last 
        20 years.

   Borehole measurements of temperature at various depths below 
        the Earth's surface show that the average surface temperature 
        of the late 20th century is without precedent in the last 500 
        years.

   Using tree rings, lake sediment records, ice cores, and 
        other paleoclimate indicators, a global temperature record 
        extending back 1000 years has been constructed. This record is 
        in broad agreement with the other data sets, and it shows that 
        the 1990s were the Earth's warmest decade in the last 1000 
        years, and that 1998 was the warmest year in this entire 
        period.

   Measurements made over the last few decades have shown a 
        precipitous decrease in both the areal extent and thickness of 
        Arctic Sea ice. Model simulations of the data suggest that this 
        decline is unlikely to be an entirely natural phenomenon. 
        Mountain glaciers have retreated worldwide during the last 
        century.

   Over the last century, global mean sea level has risen 4 to 
        8 inches, and further rise is inevitable because of the thermal 
        inertia of the ocean and melting glaciers.

   During the past 45 years the upper 300 meters of world Ocean 
        has warmed by approximately 0.56 degrees F. This warming is 
        consistent with predictions from general circulation models 
        that simulate the effect of greenhouse gas increases since the 
        beginning of the industrial revolution.

    3. The Earth's surface temperature will continue to rise during the 
next century. Elementary physics shows that increasing greenhouse gases 
in the atmosphere must exert a strong warming tendency on the surface 
temperature of the Earth. This is not a controversial concept. Indeed, 
the greenhouse effect is responsible for providing a hospitable climate 
on Earth. It is generally agreed that the Earth's surface temperature 
will rise over the next century as the atmospheric concentrations of 
CO2 and other greenhouse gases increase. The questions are: 
``How much and how fast will temperature increase, and with what 
regional impact?'' The 1995 IPCC Second Assessment Report, representing 
the broad consensus of the scientific community, projected a 
temperature increase of 1.0 to 3.5 degrees C (2 to 6.5 degrees F) over 
the next 100 years. The more sophisticated analyses conducted since 
that time, which will form the basis of the IPCC Third Assessment 
Report, due out in early 2001, continue to show that such an increase 
is likely. This rate of warming would be greater than any seen during 
the past 10,000 years.
    4. There is mounting scientific evidence that climate change is 
already affecting ecosystems. Data from many sites in Europe and North 
America show that the observed warming has been accompanied by earlier 
plant growth and flowering. For example, here in Washington, D.C., 
cherry trees, along with 89 of 99 other plants examined, are blooming a 
week or more earlier than they did 30 years ago. Satellite data for 
high latitudes in the Northern Hemisphere show that plants are leafing 
eight days earlier in 1991 than in 1982. Observed changes are not 
confined to vegetation:

   The ranges of some animals appear to be shifting. Birds are 
        going further north to breed and the range of many European and 
        North American butterflies are shifting north as well.

   Some species are disappearing when a habitat changes. Warmer 
        and drier conditions have caused the high elevation ``cloud 
        forest'' of Costa Rica to rise and 20 frog species to 
        disappear.

   Observations in several sites along the Pacific coast of 
        North America indicate that the distribution of fish and 
        phytoplankton has changed as waters warm. There is also 
        evidence that warming waters increase the amount of coral 
        bleaching.

    We have discovered much about the way the climate system works, and 
about how the climate system is likely to evolve in response to 
increases in greenhouse gases. As I noted above, the debate has changed 
from ``Are we warming the Earth?'' to ``How much are we warming the 
Earth?'' It leads directly to the question of ``So what?'' Right now, 
science only provides a partial answer. As temperatures rise 
evaporation will increase, leading to more moisture in the atmosphere. 
Hence, worldwide, an increase in total rainfall is likely, with much 
coming in heavier downpours. But increased evaporation will also lead 
to more drought in some regions. Rising temperatures will also bring 
sea-level rise. These changes in temperature, precipitation and sea 
level will likely change the ideal ranges for plant and animals, and 
will also affect human society. Our understanding of how the life 
support systems on Earth will respond to these changes remains quite 
uncertain. This uncertainty is no reason to be complacent about the 
future.

Emerging Questions
    Let me now move past points of agreement, and talk about the 
cutting edge of climate science.
    To a large extent, the disagreements between future estimates of 
the climate are disagreements about effects of the ``feedbacks'' of the 
climate system. While increasing CO2 will, by itself, tend 
to increase the surface temperature of the Earth, it will also change 
other parameters, such as the amount of water vapor or the extent of 
clouds, which also affect the climate system. For example, if the 
climate warms due to increased CO2, then this will evaporate 
more water vapor into the atmosphere. Water vapor is a powerful 
greenhouse gas, so this will amplify the warming. This is an example of 
a positive feedback. On the other hand, the increase in CO2 
might also increase low clouds. These clouds reflect sunlight, so if 
they increase it would cool the Earth, moderating somewhat the warming 
effects of the CO2 increase. These feedbacks are only 
roughly understood, and improving our understanding of them would 
significantly improve our ability to predict the future climate.
    Changes in the amount of solar radiation would definitely affect 
the climate, and there are indications that changes in solar radiation 
may have been an important contributor to climate change over the past 
few centuries. However, changes in output of the sun cannot, by 
themselves, entirely explain the observed warming over the last 
century. Our best estimates are that changes in solar output could 
explain about 25 percent of the surface temperature increase observed 
in the last 100 years. The rapidly increasing concentrations of 
greenhouse gases also mean that solar variability will be an ever-
smaller component of climate change in the future.
    There are also important questions about the relationship of 
temperature change to other changes in the physical climate system. One 
of the expected consequences of warming is acceleration of the Earth's 
hydrological cycle. The increased evaporation of water described above 
will transfer water more rapidly from the land and oceans to the 
atmosphere, and could result in an increased incidence of both droughts 
and the extreme rainfall events that lead to flooding. There is already 
evidence that such change has begun in the U.S., where the incidence of 
heavy downpours (where more than 2 inches of rain falls in a 24-hour 
period) has increased by about 10% over the last century. We know that 
there will be significant regional variation in these changes, but our 
ability to project regional-scale precipitation change is very limited, 
and we do not have a good understanding of how precipitation change 
will interact with other stresses on managed and natural ecosystems.
    We also need to quantify the relative contributions of the oceans 
and terrestrial plants to removing carbon from the atmosphere. Human 
activities add about 7 billion tons of carbon to the atmosphere every 
year. About 3 billion tons remain in the atmosphere, while 4 billion 
are absorbed by terrestrial and ocean ``sinks.'' We know that land 
ecosystems play an important role in carbon sequestration, but 
important questions remain about the magnitude and geographic 
distribution of terrestrial sinks. For example, there is consensus that 
more carbon is being taken up than is released by land ecosystems in 
the Northern Hemisphere, but we don't know if the amount is on the 
order of tens of millions or hundreds of millions of tons. And where in 
the Northern Hemisphere is carbon is being sequestered? It could be 
mostly in North America, or it might be in Siberia.
    More importantly, we don't know whether it is the above ground 
vegetation or the soils that are responsible for the apparent increase 
in sequestration. We also don't know what is causing this and whether 
it will persist. Is it from nitrogen fertilization, an effect that will 
disappear when soils become nitrogen-saturated, or as industrial and 
automobile pollution is decreased? Is it from carbon fertilization, an 
effect that could slowly decline with increasing atmospheric 
concentrations? Is it from plants growing on abandoned farmland, or 
from increased use of ``low-till'' agricultural practices? Is it from 
growth of many young forests created recently under revised logging 
laws, an effect that will decline as the forests mature? Or is it 
simply from forest trees growing better in warmer, moister conditions, 
an effect that may continue indefinitely? Finally, we know that the 
amount of carbon the global biosphere stores and releases each year can 
vary widely. However, we don't know how much of that sequestered 
CO2 in the terrestrial biosphere is transitory, being 
returned to the atmosphere in a year or two to continue contributing to 
atmospheric CO2 increases. We also don't know how much 
carbon is retained in soils for the decades or centuries required to 
ameliorate atmospheric increases. Different answers to these questions 
will determine very different trajectories of future atmospheric 
CO2 change.
    We also know that local plant and animal species are being mixed 
into ecosystems all over the world at increasing rates. Climate change 
may exacerbate this problem. We also know that when these exotic 
species spread aggressively, they can reduce and displace current 
species, disrupt ecosystem functioning, and do enormous economic 
damage. The National Academy of Sciences estimates that pubic and 
private-sector spending on Zebra Mussel control, a problem we did not 
even anticipate in the 1980s, will total $5 billion in 2000. Given that 
expected rates of change over the next century will alter the ideal 
ranges of plant and animal species faster than they can migrate, 
ecosystem disruption is likely.

New Directions in the U.S. Global Change Research Program (USGCRP)
    One of the consequences of increased understanding is the 
definition of new research questions. The process of revising and 
updating research strategies in response to new findings and new 
questions goes on every year. It is a regular part of managing large 
research programs, and the USGCRP is no exception. But periodically, it 
is also valuable to step back and take a longer-term view of what has 
been accomplished and what new research challenges are arising. One of 
the most important contributions of the National Research Council to 
the USGCRP is precisely this kind of taking stock. In 1996, the USGCRP 
requested the NRC to undertake a major study of emerging issues in 
global change science. The result was Global Environmental Change: 
Research Pathways for the Next Decade, which consists of a summary 
issued in mid 1998 and a full report published in 1999. The 
``Pathways'' report identified a comprehensive set of science 
questions, and identified several cross-cutting areas of special 
concern, including carbon cycle science, water cycle science, and 
climate change research ``on temporal and spatial scales relevant to 
human activities.'' These recommendations played an important part in 
the definition and initiation of a series of new activities in the 
USGCRP: the Carbon Cycle Science Initiative, an increased emphasis on 
water cycle research, and the initiation of the first National 
Assessment of the Potential Consequences of Climate Variability and 
Change for the US.
    The USGCRP Carbon Cycle Science Initiative was established in the 
FY2000 budget. The focus of this activity is on improving our 
understanding of how carbon moves through the Earth's terrestrial 
ecosystems, soils, ocean, and atmosphere, with $229 million proposed in 
the FY2001 budget (a $25 million increase over FY2000). This on-going 
effort will provide critical scientific information on the fate of 
carbon in the environment, the sources and sinks of carbon on 
continental and regional scales, and how sinks might change naturally 
over time or be modified by agricultural or forestry practices. USDA, 
DOE, DOI/USGS, NASA, NSF, DOC/NOAA, and the Smithsonian Institution 
will all play important roles in this effort, guided by a science plan 
that has been drafted with participation by many of the leading 
scientists in this field.
    The Carbon Cycle Science Initiative will employ a wide variety of 
research activities in a comprehensive examination of the carbon cycle 
as an integrated system, with an initial emphasis on North America. 
Comparison of North America to other regions will also be important for 
understanding the relative importance of our region in the global 
context. Atmospheric and oceanographic field sampling campaigns over 
the continent and adjacent ocean basins will be combined with 
atmospheric transport models to develop more robust estimates of the 
continental distribution and subcontinental-scale magnitude of North 
American carbon sinks. Local-scale experiments conducted in various 
regions will begin to identify the mechanisms involved in the operation 
of carbon sinks on land and in the ocean; the quantities of carbon 
assimilated by ecosystems, and how quantities might change to be 
enhanced in the future.
    The initiative will also include evaluation of information from 
past and current land-use changes, both from remotely sensed and 
historical records, to assess how human activity has affected carbon 
storage on land. Potential management strategies for maximizing carbon 
storage will be studied, including evaluation of the variability, 
sustainability, lifetime, and related uncertainties of different 
managed sequestration approaches. Finally, enhanced long-term 
monitoring of the atmosphere, ocean, forests, agricultural lands, and 
range lands, using improved inventory techniques and new remote 
sensing, will be used to determine long-term changes in carbon stocks. 
Integration of new observations and understanding of carbon cycle 
processes in regional and global carbon system models will enable us to 
more accurately project future atmospheric concentrations of carbon 
dioxide and other greenhouse gases.
    The highest priority for FY2001 will continue to be on 
understanding and quantifying North American carbon sources and sinks, 
and on filling critical gaps in our understanding of the causes of 
carbon sinks on land as well as processes controlling the uptake and 
storage of carbon in the ocean. Research advances on these questions 
will provide information needed as a basis for sound policymaking, as 
well as valuable information about potential management strategies to 
land and forest managers in both the public and private sectors.
    Research on the Global Water Cycle is receiving increased attention 
in the USGCRP, with $308 million proposed in the FY2001 budget (a $35 
million increase over FY2000). This has been an important research area 
since the inception of the USGCRP, but the increasing evidence that 
changes in the water cycle are already occurring, and that changes in 
the water cycle and climate are closely coupled, are leading to a new 
emphasis on water cycle science. The USGCRP has established a Water 
Cycle Study Panel that is focused on improving our understanding of how 
water moves through the land, atmosphere, and ocean, and how global 
change may increase or decrease regional water availability. This 
group, which includes government and academic scientists, is developing 
comprehensive research and applications strategies that will take 
advantage of existing and future observing systems to address the major 
issues concerning the global water cycle and global and national water 
resources.
    The primary goal is to achieve a greater understanding of the 
seasonal, annual, and interannual mean state and variability of water 
and energy cycles at continental-to-global scales, and thus a greater 
understanding of the hydrological interactions in the Earth's climate 
system. The study of the global water cycle is a unifying theme that 
bridges the gap between the spatial scales involved in global 
atmospheric (and atmosphere-ocean interaction) processes, and land 
surface hydrological processes, which determine the availability of 
water resources.
    Finally, the U.S. National Assessment of the Potential Consequences 
of Climate Variability and Change is now nearing completion. The 
National Assessment effort, which began in 1997, is examining the 
degree to which particular regions and sectors of the U.S. are 
vulnerable to climate variations and change. The National Assessment is 
examining the potential ecological and socioeconomic impacts of climate 
variations and change, and ways we might prepare for both the next few 
decades and the next century, including identification of possible 
adaptation measures. It is also identifying key information gaps and 
research needs (i.e., information that is still required to answer 
questions of interest to resource managers and decision-makers).
    The assessment effort has included a series of regional workshops 
with participation from a broad range of public and private 
stakeholders in the identification of issues of interest and a series 
of regional and sectoral analyses, most of which are not yet complete. 
The major product of the assessment process is a National Assessment 
Synthesis Report that should be completed this year. The National 
Assessment Synthesis Report is undergoing a rigorous peer-review that 
includes several rounds of technical review, full agency review, and a 
60-day public comment period before it is submitted to the President 
and the Congress. The U.S. Global Change Research Act calls for this 
type of assessment of the potential consequences of global changes on a 
periodic basis.
    The first National Assessment will soon be completed, but we expect 
many of the lessons learned during this process to play a significant 
role in the definition of future USGCRP research activities. There were 
important issues that it was not possible to fully address in this 
initial effort, such as the potential indirect effects on the U.S. of 
changes in other parts of the world. Many additional questions of 
interest have been identified. Farmers and ranchers are curious about 
what might change for their competitors in other nations. People all 
around the country are interested in how climate change might alter the 
incidence of extreme climate conditions that affect the quality of life 
and livelihoods, such as drought, heat waves, and severe storms.
    This first assessment is part of a larger evolution of the USGCRP. 
During much of the first decade of its existence, the program 
concentrated on observing and documenting change in the Earth's 
physical systems and understanding why these changes are occurring. It 
is now appropriately shifting from this predominant focus on physical 
systems to a much broader effort to understand how global change will 
affect the Earth's biological systems and the human societies that are 
dependent upon them, and make useful scientific data and information 
more broadly available for public and private planning and decision 
making.
    To accomplish this, we must greatly improve our capabilities for 
conducting regional-scale assessment of global change and its potential 
consequences around the country. Our current level of understanding 
tells us that climate change and its effects will vary by region, but 
our ability to project specific regional effects remains limited. We 
also need to learn more about the interactions of natural and human-
induced climate change and variability and other human-induced stresses 
on the environment, such as pollution, land-use change, resource 
extraction, and invasive species, many of which are regional in scale. 
Additionally, we need to achieve an integrated understanding not only 
of the nature and extent of physical and biological effects of climate 
change, but also of their ramifications for our social and economic 
systems.

The Organization of the U.S. Global Change Research Program
    Our current understanding of climate change, as well as our 
understanding of many other important global change issues, is the 
result of the significant progress that has occurred over the last 
several decades through scientific research. U.S. climate change 
research is largely supported through the USGCRP. The Administration is 
committed to continued strong support for the research needed to 
improve our understanding of the mechanisms of the Earth's climate 
system, the likely future course of climate change, and the potential 
impacts of such change on the environment and human society.
    The USGCRP, a program planned during the Reagan Administration and 
elevated to a Presidential Initiative under President Bush in 1989, was 
codified by the Global Change Research Act of 1990. The program has 
been strongly backed by every Administration and Congress since its 
inception. The FY2001 Budget Request demonstrates President Clinton's 
ongoing commitment to the program, with an overall request for the 
USGCRP of approximately $1.74 billion dollars, about 2 percent (or $39 
million) higher than last year's enacted level (tables showing the 
budget by agency and by program element area are attached).
    Within the total, support for scientific research is up about $53 
million (7%), including a $31 million increase for carbon cycle studies 
at USDA as part of the carbon cycle research initiative begun last 
year. Surface-based observations at NOAA are receiving a substantial 
increase ($26 million, or about 39%) that will help provide new 
information on changing patterns of temperature and rainfall in the US. 
The total increase for surface-based observations and science together 
is about $79 million, or 10%. The space-based observation component of 
the budget is reduced by about $40 million, to a total of $897 million. 
This decrease is mainly a consequence of decreases in NASA development 
costs as some of the first series of Earth Observing System (EOS) 
satellites are completed and launched.
    The fact that the increase in science funding more than offsets the 
decrease in funding for space-based observations is important. 
Increasing the proportion of program funding for science has been one 
of the most consistent recommendations from the National Research 
Council and various agency advisory committees over the last few years. 
The National Research Council (NRC) report, Global Environmental 
Change: Research Pathways for the Next Decade, noted that 65 percent of 
the total USGCRP were devoted to space-based observations and data 
systems in the 1996 budget proposal. In this year's budget proposal, 
the equivalent number is about 52 percent, demonstrating the progress 
that has been made over the last 5 years in increasing the proportion 
of USGCRP funding for scientific research and analysis.
    Since its inception, the USGCRP has been directed toward 
strengthening research on key scientific issues, and has fostered much 
improved insight into the processes and interactions of the Earth 
system. The results of research supported by the USGCRP play an 
important role in international scientific assessments, including 
assessments of climate change and stratospheric ozone depletion. The 
USGCRP research results provide the scientific information base that 
underpins consideration of possible response strategies. The USGCRP 
does not recommend specific government policies responsive to global 
change, nor does it include support for research and development of 
energy technologies or development of mitigation strategies.

Participants and Organization
    The Subcommittee on Global Change Research (SGCR) of the Committee 
on Environment and Natural Resources (CENR), a component of the 
National Science and Technology Council (NSTC), provides overall 
direction and executive oversight of the USGCRP. In addition, the 
National Research Council within the National Academy of Sciences 
provides external oversight and review of USGCRP programs. Agencies 
manage and coordinate Federally supported scientific research on global 
change within this framework. In addition to USGCRP review of the 
overall set of agency research programs, each agency is responsible for 
the review of individual projects within its programs. These reviews 
are almost exclusively based on an external peer-review process, which 
is deemed an important means of ensuring continued program quality.
    The agencies that actively participate in the USGCRP are USDA, DOC/
NOAA, DOE, HHS/NIH, DOI/USGS, EPA, NASA, NSF, and the Smithsonian 
Institution. OMB and OSTP are the Executive Office of the President 
liaisons to the SGCR. The Department of State does not fund research 
but is part of the SGCR because of the extensive international 
cooperation necessary in all aspects of global change research. The 
Department of Defense does not fund research focused on global change, 
but participates in the SGCR because it performs related research, such 
as how changing ocean conditions may affect their ability to ensure the 
nation's security. Some of these agencies support research on a broad 
range of issues, while others have a more specialized focus. 
Programmatic contributions are closely matched to agency missions and 
areas of expertise. The crosscutting research that takes place in the 
USGCRP program element areas takes advantage of the unique capabilities 
of different agencies and applies them to science problems that are 
beyond the scope of any single agency's mission or the ability of any 
one agency's programs to address.
    The scientific community contributes to the planning, definition, 
and implementation of USGCRP research activities. An important aspect 
of this is scientific oversight and review of the USGCRP that is 
provided by the National Academy of Sciences. This function includes 
review of various program activities and examination of scientific 
issues in response to requests from the USGCRP and participating 
agencies. Over the past several years, the USGCRP has commissioned a 
series of reports, including ``Pathways'' and smaller reports on 
climate observations and climate modeling. These reports have provided 
important input to the ongoing planning and program implementation 
decisions of the USGCRP agencies, including the initiation of the 
carbon cycle and water cycle research efforts described above, and the 
current organization of the USGCRP as a series of other interrelated 
program elements.

   Understanding the Earth's Climate System, with a focus on 
        improving our understanding of the climate system as a whole, 
        rather than its individual components, and thus improving our 
        ability to predict climate change and variability. The FY2001 
        budget proposes $487 million for this program element (a 
        decrease of $16 million), which is largely focused on the 
        physical climate system. Improving our understanding of climate 
        change, including its potential impacts on ecosystems and human 
        society, requires support of research and integration of 
        results across the entire USGCRP. Climate is a naturally 
        varying and dynamic system with important implications for the 
        social and economic well being of our societies. Understanding 
        and predicting climate changes across multiple time scales 
        (ranging from seasonal to interannual, to decadal and longer) 
        offers valuable information for decision making in those 
        sectors sensitive to rainfall and temperature fluctuations, 
        including agriculture, water management, energy, 
        transportation, and human health.

   Biology and Biogeochemistry of Ecosystems, with a focus on 
        improving understanding of the relationship between a changing 
        biosphere and a changing climate and the impacts of global 
        change on managed and natural ecosystems, including forests, 
        coastal areas, and agriculture. The budget proposes $224 
        million in FY2001 (an increase of $19 million) for the study of 
        changes in managed and unmanaged ecosystems. The biosphere 
        consists of diverse ecosystems that vary widely in complexity 
        and productivity, in the extent to which they are managed, and 
        in their economic value to society. Better scientific 
        understanding of the processes that regulate ecosystems and the 
        capability to predict ecosystem changes and evaluate the 
        potential consequences of management strategies will improve 
        our ability to manage for sustainability.

   Composition and Chemistry of the Atmosphere, with a focus on 
        improving our understanding of the impacts of natural and human 
        processes on the chemical composition of the atmosphere at 
        global and regional scales, and determining the effect of such 
        changes on air quality and human health. The budget proposes 
        $368 million for programs studying the composition and 
        chemistry of the atmosphere (a decrease of $21 million from 
        FY2000). Changes in the global atmosphere can have important 
        implications for life on Earth, including such factors as the 
        exposure to biologically damaging ultraviolet (UV) radiation, 
        the abundance of greenhouse gases and aerosols (which in turn 
        affect climate), and regional air pollution.

   Paleoenvironment and Paleoclimate, with a focus on providing 
        a quantitative understanding of the patterns of natural 
        environmental variability, on timescales from centuries to 
        millennia, upon which are superimposed the effects of human 
        activities on the planet's biosphere, geosphere, and 
        atmosphere. The budget proposes $27 million in FY2001 (a 
        decrease of $2 million) for the study of the Earth's 
        environmental past. Reconstructing the historical climate 
        record offers an enhanced understanding of the mechanisms 
        controlling the Earth's climate system and, together with 
        insight obtained from numerical modeling exercises, provides a 
        foundation for anticipating how the planet might respond to 
        future environmental perturbations.

   Human Dimensions of Global Change, with a focus on 
        explaining how humans affect the Earth system and are affected 
        by it, and on investigating how humans respond to global 
        change. The budget proposes $93 million in FY2001 (level with 
        FY2000) for the study of the human dimensions of global change. 
        Scientific uncertainties about the role of human socioeconomic 
        and institutional factors in global change are as significant 
        as uncertainties about the physical, chemical, and biological 
        aspects of the Earth system. Improving our scientific 
        understanding of how humans cause changes in the Earth system, 
        and how society, in turn, is affected by the interactions 
        between natural and social processes, is an important priority 
        for the USGCRP.

Conclusion
    This brief description of climate change science and U.S. climate 
change research efforts should be seen as a summary rather than a 
comprehensive overview. Nevertheless, it highlights several very 
important points. The USGCRP is a broad and successful program of 
research on global change that is resulting in increases in our 
understanding of how the Earth system is changing, and of the human 
role in such change. In particular, it has made a major contribution to 
our understanding of climate change. USGCRP-supported research has 
played a key role in demonstrating that climate change is occurring, 
and that human activities are playing a role in causing such change. It 
has helped explain the relationships between climate change and other 
significant global-scale environmental changes, such as land cover 
change, ozone depletion, and loss of biodiversity.
    We expect a much fuller understanding of the processes of change to 
emerge from this effort in the future. The sustained bipartisan support 
for global change research over the last decade has enabled steady 
scientific progress and resulted in the development of a new generation 
of tools that offer the promise of more rapid progress in the years 
ahead. We will benefit from unprecedented amounts of data about the 
Earth, and these data will be of higher quality than ever before. We 
will develop more complex and accurate models that permit more 
realistic simulation of the Earth system. Most importantly, we can 
expect to learn much more about the potential consequences of change 
for ecosystems and for human society.

                                       U.S. Global Change Research Program
                                         By Agency/Appropriation Account
                                                 FY 2001 Budget
                            (Discretionary budget authority; in millions of dollars)
----------------------------------------------------------------------------------------------------------------
                                                                             FY
                                                                            1999    FY 2000   FY 2001    Change
                                                                           Actual  Estimate  Proposed  2000-2001
----------------------------------------------------------------------------------------------------------------
Department of Health and Human Services
  National Institutes of Health                                             40       46        48         +2
----------------------------------------------------------------------------------------------------------------
National Aeronautics and Space
  Administration
  Science, Aeronautics, and Technology                                     1,155   1,173     1,149       -24
----------------------------------------------------------------------------------------------------------------
Department of Energy
  Science (Biological & Environmental Research)                            114      120       123         +3
----------------------------------------------------------------------------------------------------------------
National Science Foundation
  Research and Related Activities                                          182      187       187          0
----------------------------------------------------------------------------------------------------------------
Department of Agriculture
  Agricultural Research Service                                             26       27        36         +9
  Cooperative State Research, Education and
    Extension Services
  Research and Education                                                     7        7        14         +7
  Economic Research Service                                                  1        1         2         +1
  Natural Resources Conservation Service
    Conservation Operations                                                  1        1        14        +13
  Forest Service
    Forest and Rangeland Research                                           17       17        20         +3
----------------------------------------------------------------------------------------------------------------
        Subtotal--USDA                                                      52       53        85        +32
----------------------------------------------------------------------------------------------------------------
Department of Commerce
  National Oceanic and Atmospheric Administration
    Operations, Research, and Facilities                                    63       67        93        +26
----------------------------------------------------------------------------------------------------------------
Department of the Interior
  U.S. Geological Survey
    Surveys, Investigations, and Research                                   27       25        25          0
----------------------------------------------------------------------------------------------------------------
Environmental Protection Agency
  Science and Technology                                                    17       23        23          0
----------------------------------------------------------------------------------------------------------------
Smithsonian Institution
  Salaries and Expenses                                                      7        7         7          0
----------------------------------------------------------------------------------------------------------------
        TOTAL \1\                                                          1,657   1,701     1,740       +39
----------------------------------------------------------------------------------------------------------------
\1\ Note: Total may not add due to rounding.


                                       U.S. Global Change Research Program
                                      Details by Program Element/By Agency
                                                 FY 2001 Budget
                            (Discretionary budget authority; in millions of dollars)
----------------------------------------------------------------------------------------------------------------
                                                                             FY
                                                                            1999    FY 2000   FY 2001    Change
                                                                           Actual  Estimate  Proposed  2000-2001
----------------------------------------------------------------------------------------------------------------
Understanding the Earth's Climate System
  National Aeronautics and Space Administration                            324      310       271        -39
  National Science Foundation                                               82       84        84          0
  Department of Energy                                                      64       68        73         +5
  Department of Commerce/NOAA                                               38       41        59        +18
  Department of the Interior                                                 7        0         0          0
  Smithsonian                                                                *        *         *          *
    Subtotal                                                               515      503       487        -16
----------------------------------------------------------------------------------------------------------------
Composition and Chemistry of the Atmosphere
  National Aeronautics and Space Administration                            310      330       306        -24
  National Science Foundation                                               18       19        19          0
  Department of Energy                                                      16       16        15         -1
  Department of Agriculture                                                 16       15        18         +3
  Department of Commerce/NOAA                                                8        9        10         +1
  Smithsonian                                                                *        *         *          *
    Subtotal                                                               368      389       368        -21
----------------------------------------------------------------------------------------------------------------
Global Water Cycle
  National Aeronautics and Space Administration                            238      255       288        +33
  National Science Foundation                                               10       10        10          0
  Department of Commerce/NOAA                                                5        5         7         +2
  Department of Energy                                                       0        4         3         -1
  Department of Agriculture                                                  0        *         *          *
    Subtotal                                                               253      274       308        +34
----------------------------------------------------------------------------------------------------------------
Carbon Cycle Science
  National Aeronautics and Space Administration                            154      154       150         -4
  National Science Foundation                                               13       13        13          0
  Department of Energy                                                      14       14        15         +1
  Department of Agriculture                                                  7       15        37        +22
  Department of Commerce/NOAA                                                4        5        10         +5
  Department of the Interior                                                 3        3         4         +1
  Smithsonian                                                                *        *         *          *
    Subtotal                                                               195      204       229        +25
----------------------------------------------------------------------------------------------------------------
Biology and Biochemistry of Ecosystems
  National Aeronautics and Space Administration                            129      124       134        +10
  Department of Agriculture                                                 32       22        29         +7
  National Science Foundation                                               27       29        29          0
  Department of Energy                                                      13       11        11          0
  Department of the Interior                                                13       13        14         +1
  Smithsonian                                                                4        4         4          0
  Environmental Protection Agency                                            0        2         3         +1
    Subtotal                                                               218      205       224        +19
----------------------------------------------------------------------------------------------------------------
Human Dimensions of Climate Change
  Health and Human Services                                                 40       46        48         +2
  Environmental Protection Agency                                           17       19        20         +1
  National Science Foundation                                               14       14        14          0
  Department of Energy                                                       5        8         5         -3
  Department of Commerce/NOAA                                                5        5         5          0
  Smithsonian                                                                1        1         1          0
    Subtotal                                                                82       93        93          0
----------------------------------------------------------------------------------------------------------------
Paleoenvironment/Paleoclimate
  National Science Foundation                                               18       19        19          0
  Department of Commerce/NOAA                                                2        2         2          0
  Smithsonian                                                                2        2         2          0
  Department of the Interior                                                 0        6         4         -2
    Subtotal                                                                22       29        27         -2
----------------------------------------------------------------------------------------------------------------
        Total 1,2,3                                                        1,653   1,697     1,736       +39
----------------------------------------------------------------------------------------------------------------
* less than $500,000.
\1\ Total may not add due to rounding.
\2\ FY 1999 does not include $3 million in DOE Small Business Innovative Research funding.
\3\ FY 2000 and FY 2001 does not include $4 million in DOI Data Management funding.


    The Chairman. We will proceed during this hearing, at least 
as far as this member is concerned, on the premise that there 
is no such thing as a dumb question. This is an area where I 
admitted in my opening statement that I have a very steep 
learning curve. And as I also mentioned, this will be the 
first, of what I hope to be a number of hearings, that we can 
have on this issue.
    First of all, what changed between the 1995 IPCC report and 
today that has shifted the debate from ``Are we warming the 
Earth?'' to ``How much are we warming the Earth?''
    Dr. Lane. Senator, I think the simple answer is just that 
more science got done, and became available, and then could be 
analyzed by this international peer review process.
    The Chairman. That is an important change, do you not 
think?
    Dr. Lane. I think the change is important. It is--
particularly in the Academy report that was referred to--very 
clear that there really is not any remaining debate about 
whether the Earth is warming or not. It is quite clear that the 
Earth is warming, and there is significant consensus that the 
human activity is a part of that warming.
    So I think it is time to focus on what that means in terms 
of lives of people and nations. And that also involves 
significant research questions, and that in part, what the 
Global Change Research Program is all about.
    It does not mean there are not still important questions 
about the physics and the chemistry of climate change. And we 
will continue to support those research activities to further 
deepen our knowledge in those areas, but I think it is quite 
clear that the larger questions have shifted. And it is 
important the research program respond.
    The Chairman. Do you believe that the upcoming report will 
alter the current debate among scientists?
    Dr. Lane. Senator, I think that many of these questions 
have been subject to scientific debate, and that is how the 
scientific process works. I would expect that increasingly 
researchers will turn their attention to some of these more 
complex questions, and we will see more attention in the 
scientific arena to this research.
    The Chairman. Are other nations devoting anywhere near the 
time and assets and scientific effort that the United States 
is?
    Dr. Lane. I can submit budget numbers to the Committee for 
the record. I do not have them fresh in my mind.
    The Chairman. Just your overall impression about that.
    Dr. Lane. I would emphasize that, yes, the Global Change 
Research Program, the U.S. program, is part of a much larger 
international effort. And it, in my view, is one of the best 
examples among several very good ones, of international 
cooperation and science. The IPCC process involves hundreds of 
experts in all aspects of climate change, the social sciences, 
the economic sciences, as well as the physics----
    The Chairman. Well, I do not mean to interrupt, but my 
question is: Are other nations devoting the time and assets--I 
understand we have a budget request for $1.74 billion. Are 
other nations involving themselves with the degree of 
commitment that we are?
    Dr. Lane. My sense is that the degree of commitment on the 
part of many nations of the world is very substantial, and in 
the research area, which I think is what you would like for me 
to address, the area of climate modeling is one in which, in 
some sense, other countries are ahead of us. And that is an 
issue for us to be concerned about.
    We asked the Academy to study this question, give us a 
report. And the Academy concluded that in the case of climate 
modeling, the United States may be losing leadership to 
researchers in other countries. So I would say in a case like 
that, it is very clear that the commitment is quite strong.
    The Chairman. A lot of our concerns here are anecdotal 
obviously. We read where a huge piece of ice broke off from the 
Antarctic. Does that mean anything to you?
    Dr. Lane. I found that an extremely interesting story, as 
well, and it is a true story. And I have been to the Antarctic 
several times in my role as Director of the National Science 
Foundation since National Science Foundation runs the U.S. 
program down there. That was an extraordinary event.
    One cannot really connect single events of that kind with 
the larger issue of global climate change, and I think it would 
be a mistake to do that. But there are many other examples such 
as the receding of the glaciers and high country around the 
world over the last several decades.
    There is the fairly recent observation that the ice in the 
Arctic region is less in extent and also thinner than we 
anticipated. All those are very significant research questions 
that do have a relationship with the Global Change Research 
Program.
    The Chairman. What about the disappearance of species of 
fish?
    Dr. Lane. We do have evidence that all kinds of life, 
animal life and plant life, is responding to a global change. 
Fish appear to be moving. There is much evidence of early 
blooming of plants. In fact, even in Washington, the cherry 
blossoms are blooming an average of a week earlier, I think the 
number would be, than they were a decade or so ago.
    So ecosystems all over the world are showing some unusual 
movement that might be connected with climate change.
    The Chairman. A lot of this is in the oceans, right?
    Dr. Lane. Define----
    The Chairman. A lot of these changes, we have seen in the 
oceans. What about the death of coral reefs?
    Dr. Lane. Coral reefs are dying all over the world. It is a 
serious problem. Some would predict that without finding the 
cause and doing something about it, we could lose essentially 
all of our coral reefs in the next 100 years.
    We have a significant research effort trying to understand 
the problem with coral reefs. Scientific opinion is that there 
may be several causes, including global warming, which sort of 
chases the algae out of the coral.
    The Chairman. What are some of the other reasons?
    Dr. Lane. Some of the others are pollution, some damage 
just from the human interaction directly with the coral, coral 
disease from causes we do not entirely understand. But there is 
a pretty strong opinion that the warming of the oceans may very 
well be responsible for loss of coral.
    A recent example of that is with the El Nino event which 
may or may not be connected with overall global climate change, 
but which is a very significant climate feature. During the 
last severe El Nino, there was considerable coral bleaching and 
loss of coral due to the increased temperatures.
    So we know that if you increase the temperature of the 
ocean over the coral, you will lose coral. We simply do not 
know how large that effect is versus other possible problems 
that we have with our coral reefs.
    The Chairman. It seems to me that it is almost like 
connecting the dots here. We see example after example ranging 
from ice breaking up in the Antarctic to the death of coral 
reefs to the inexorable increase in water levels, oceanic 
levels. Does that make any sense, or is it just that we are 
being a little bit hysterical?
    Dr. Lane. I think--picking up on your earlier statement, 
Mr. Chairman, I think the public understands something is going 
on, something is happening.
    Scientifically, the experts, who you will hear from 
shortly, have the data, and the analysis, and the modeling to 
show just what we know in detail scientifically and where the 
questions remain. But there are things going on that point to 
potential problems that perhaps we do not have what we would 
consider reliable scientific data on yet, but in time, we will 
better understand how the various dots connect. And maybe there 
is a dot that does not connect.
    Maybe there is some phenomenon out there that looks like it 
might connect with climate change, but in the end, we find it 
has nothing to do with it. We cannot know that for sure right 
now.
    That is why I think having the discussion about the science 
and helping the public understand--as you emphasized, Mr. 
Chairman, we need to do--what the science is and how the 
science consensus is formed, and why there will be debate and 
differences of opinion among experts, that is all good.
    That is the way science advances, and I think this 
potential for harm to the people of our country and our world 
due to global climate change is so great that it behooves us to 
have this discussion, and have it as early as we can, and make 
the necessary investment to try to get the answers to some of 
these remaining questions.
    The Chairman. By intent, our next panel has experts of 
contrasting views. And I think that that is the most important 
and only fair way to address this issue.
    When do you think--if we did everything in a perfect 
scenario, when do you think we could have some definitive 
answers to these largely unanswered questions, or some of them?
    In other words, what can we as Americans expect out of the 
scientific community and out of the $1.74 billion investment in 
the U.S. Global Change Research Program?
    Dr. Lane. Senator, I think that we can expect significant 
progress in answering some of these questions. What the experts 
sort of need to help the Committee understand is ``Which are we 
most likely to be able to pin down first, and which are we 
going to pin down next?''
    For example, one reason we are felt by the Academy to be 
falling a bit behind in our climate modeling has a lot to do 
with computer capability. I mean, our modelers are among the 
top experts in the world in this area, but for a variety of 
reasons, they really do not have access to the kind of computer 
capability that they need to run these big models.
    So, as we address that, and we are doing so in the 
President's information technology initiatives that have 
received bi-partisan support, we will provide that capability. 
Then we will be able to run these models, get the error bars 
down, and answer the questions most directly.
    So I hesitate to speculate on a particular question that 
``I think we are going to answer in 1 or 2 years,'' but the 
progress has been very good since the last IPCC report. And I 
would anticipate just as great progress answering the remaining 
questions in the next period.
    The Chairman. Will we have some definitive answers within 
the next couple of years?
    Dr. Lane. I would expect we will have some definitive 
answers in the next several years. For example, places where we 
have made significant progress is in understanding the role--I 
emphasized the importance of clouds--understanding the role of 
clouds.
    One of the big uncertainties in the model is how clouds 
behave and how most appropriately to put them in the model.
    The second one is the effect of aerosols. Generally, the 
view is that aerosols, which can be anything from ice to 
crystals of other kinds and soot--just tiny little particles 
that are suspended in the atmosphere--the thought has been that 
those would generally have a cooling effect. They would reflect 
the sunlight before it gets down and has a chance to heat the 
earth and contribute to global warming.
    By and large, my own view is that still is probably true, 
but there was a recent report from our international research 
activity in the Indian Ocean where the aerosols turn out to be 
quite dark and pollution is very heavy. It looks as if those 
aerosols are actually not reflecting light very well.
    They are heating up. They themselves then, in their 
interaction with the clouds, are causing the clouds to 
dissipate, and that is having a warming effect. We need to 
understand that--my guess is that those are areas: clouds, ice, 
which I did not mention, and aerosols, in which we would be 
able to make significant progress in the next few years, but I 
would concede to my experts on the subject for their estimate.
    The Chairman. Senator Kerry, thank you for being here.

               STATEMENT OF HON. JOHN F. KERRY, 
                U.S. SENATOR FROM MASSACHUSETTS

    Senator Kerry. Thank you, Mr. Chairman, and thank you very 
much for having this hearing and for your willingness to open 
up the dialogue with respect to this issue. I have been 
interested in and have been involved in this issue for a long 
period of time now.
    In my responsibilities as a Senator I had the privilege of 
joining Vice President Gore, Tim Wirth, John Chafee, and others 
as a member of the delegation down in Rio for the first Earth 
Summit when President Bush embraced the early findings of 
scientists regarding global warming.
    I subsequently have been at the Buenos Aires followup 
meeting, and I was working with Stu Eisenstat and others in 
Kyoto where the negotiations took place. Stu, I think, did a 
very brilliant job in helping develop the Kyoto Treaty.
    And I must say, Mr. Chairman, I have been a little bit 
dumbfounded and somewhat disturbed by the level of skepticism 
that exists, and has existed over a long period of time, in the 
U.S. Congress with respect to this issue.
    We may not have definitive answers for every model, as to 
exactly what forest may move, or precisely how much the sea may 
rise in a particular area over what period of time, but we 
have--correct me if I am wrong, Dr. Lane--absolutely definitive 
science to tell us that the ocean is rising, and that there are 
a number of pollutants that we emit.
    I mean, there is a health issue here, not just a question 
of the effect of global warming. Over the last years, the 
science just keeps getting stronger, and stronger, and 
stronger, reinforcing the theories. The world has, frankly, 
moved more rapidly than the United States.
    And in answer to your question--a couple of weeks ago, we 
had a dinner with the Deputy Prime Minister John Prescott, who 
heads up negotiations for Great Britain, and with the Dutch, 
and others here in Washington, talking about the next meeting 
that will take place in Berlin. There are great concerns about 
the United States' lack of response.
    Frankly, the lack of response by the United States is 
significantly impeding our capacity to bring less developed 
countries into the equation. I am all for the Senate Resolution 
passed in the 105th Congress, which supports this goal of the 
Kyoto Protocol. If we let Mexico, and Korea, and India, and 
China proceed to develop without being participants, they can 
negate every gain that we take in the United States. So, this 
is a global problem.
    But right now, there is such antipathy directed at the 
United States for our lack of seriousness about this, that few 
people are willing to join us in a serious dialogue until we 
demonstrate a little bit of leadership.
    Let me just say, Mr. Chairman, that the science--and we 
will hear this from two of our witnesses this morning--on a 
scale of virtual certainty from one to ten, it is ten out of 
ten. It is virtually certain that some changes indicative of 
climate change are now happening.
    And, Dr. Lane, you will confirm, as every scientist here 
will, that the half life of carbon dioxide and of the other 
greenhouse gas emissions is such that if we just went cold 
turkey today and brought our levels down to the 1990 baseline 
where we are supposed to be according to the Rio voluntary 
agreements, we would still have 70 years of global warming 
effects that are going to occur because the gases have long 
half lives. Therefore, the danger of global warming is going to 
continue no matter what we do today even if we are successful 
at reducing emissions.
    The complexity of global warming can be so daunting that it 
partly is a turn-off to people. They do not want to cope with 
it or try to grapple with it because the problem is quite 
enormous.
    Now again, I say, I know we do not have certainty in the 
model, and, to a degree, people fight about the trivial 
matters. Do we know whether or not Florida is by year such and 
such absolutely going to lose the Miami beaches? No, we cannot 
say exactly what year or when, but we have absolute certainty 
as to the rise in sea level, a range that is disastrous. Take 
even the bottom line of the range--we know it is disastrous.
    Now, we know the worldwide rise in temperatures at the 
earth's surface is real. We know it has accelerated in recent 
decades. The independent scientific panel organized by the 
National Academy of Sciences concluded in a major report issued 
this February that they now have that sort of certainty. They 
estimate the increase in temperatures in the past century 
between .7 and 1.4 degrees Fahrenheit. That is a 30-percent 
increase from earlier projections that reflect record 
shattering high temperatures in the late 1990's.
    We now have learned how to deal with the disparity between 
the satellite findings of the upper atmosphere versus what we 
have on earth, and it sort of makes sense that it is going to 
be warmer down here than it is up there in terms of the ratio 
of impact.
    And I might say, Mr. Chairman, this sounds sort of 
fundamental, but it really goes to the bottom of this. The 
theory about this was found by a fellow named Arhenius in 1898, 
and it has progressed since then.
    And every prognostication of the early scientific data on 
this has been eclipsed by the subsequent findings of fact. Each 
time it has blown away the theory in terms of being more 
serious than people thought.
    But the fact is that life exists on earth because we have a 
greenhouse effect. Were it not for the existence of the 
greenhouse effect, we would not have plant life and human life.
    And it is common sense that if you are emitting gases into 
that atmosphere that are trapped, it will have a long-term 
impact on weather and other things.
    Well, we now find that for the third year in a row we have 
set a record for winter warmth. The 3-month period of December 
1999 through February of 2000 was the warmest winter season in 
the contiguous 48 states in the entire 105 years that we have 
recorded the data.
    That slightly surpassed the record set just one year ago, 
and that slightly surpassed the record set the prior year. So 
we have the three warmest years in the last 3 years. And that 
fits in completely with the detected trend about later freezes 
in the fall, and earlier temperatures of the frost.
    I remember as a kid in Massachusetts, we always looked 
forward to October/November because the ponds froze over and we 
were going to have thick ice, and go play hockey. Today, you 
are lucky if the ponds freeze in Northern New Hampshire.
    And unlike the days when we used to have snow on the ground 
from October to April when we were campaigning as recently as 
20 years ago, I used to freeze and wear a coat in the morning. 
I do not wear a coat until after November now.
    Anybody who does not see the impact of these changes is 
putting their head in the sand. Now, can we say that every bit 
of this is due to global warming? The answer is no. I cannot 
sit here and tell you that. No scientist is going to tell you 
that every bit of it is. Some of it may be normal changes that 
are taking place in terms of the climate process, but we do 
know with absolute certainty, incontrovertible scientific fact, 
we are contributing to it.
    And we ought to adopt the prudent person theory with 
respect to those things that you do not quite know what the 
final consequences are going to be but you know they might be 
disastrous.
    It is like smoking, Mr. Chairman. You and others have 
adopted a very tough policy on the odds about contracting 
cancer from smoking. Does everybody get cancer who smokes? The 
answer is no. But do we know what the probabilities are? The 
answer is yes. The probabilities of this are greater than some 
of what we know about the linkages of cancer in certain kinds 
of disease. We take far more steps to deal with that than we do 
with this.
    Final comment I would make is, and this is of enormous 
concern I think to everybody, is the great ice cover that 
stretches across the top of the globe is about 40 percent 
thinner than it was just 2 to 4 decades ago. We know this 
through our data from nuclear submarines that have been plying 
the Arctic Ocean.
    Scientists from the University of Washington found in a new 
study that the average thickness of the Arctic ice was about 
ten feet from 1958 to 1976. From 1993 to 1997, it is about six 
feet, and in the 1990's, the thinning has been continuing at a 
rate of about four inches a year.
    The area covered by sea ice has diminished and the duration 
of the cover has shortened. Mountain glaciers in Alaska have 
shrunk as has the Greenland ice cap. And the consequences of 
this, according to many experts now, is huge concern about what 
happens with sea levels because if the big ice sheets melt even 
partly, sea levels will rise around the world.
    And there are serious questions--I do not have the answers 
again--about the potential disruption of certain ocean 
currents, but those ocean currents modulate the earth's 
climate. We do not know the answer of what happens to the Gulf 
Stream, but I am concerned about the potential of what might 
happen to it.
    So this hearing and the further science is critical, but we 
should not confuse ourselves by not having answers to every 
single question that common sense drives us to try to mitigate 
at this point in time. And I think that is really the critical 
issue that this Committee, the Congress, and the entire country 
faces.
    Unless the United States is more serious about this effort, 
we are going to have a difficult time getting less developed 
countries and others to join in a more cooperative effort. So 
there is a huge amount at stake and I think this hearing is 
very important in that regard.
    In each of the past 2 years, the House of Representatives 
has included riders in appropriations bills on the Kyoto 
Protocol. And this year, a new bill has language that is 
included in the Agricultural Appropriations Bill that will 
limit the Administration's activities on an international level 
to even continue the dialogue and process of building a 
consensus about Kyoto.
    Do you share a concern that this provision could impede our 
understanding of climate change and the ways we might mitigate 
it, Doctor?
    Dr. Lane. Yes, Senator, I am very concerned about this 
rider. The rider seems, on the face of it, extreme. It tries to 
block the United States from even trying to reach an agreement 
with other countries on action to combat global warming, which 
is very difficult to explain to our international partners 
around the world.
    It undermines the ability of the executive branch to 
conduct international negotiations, which seems to me to raise 
serious constitutional questions. It may stifle U.S. efforts to 
achieve bi-partisan goals with a cost effective treaty and 
meaningful participation of developing countries which, 
Senator, you have emphasized.
    It is extremely important that we are able to sit down with 
developing countries and address their participation in dealing 
with this problem of global warming.
    The amendment is bad for American industry. It is bad for 
the farmers. It is bad for consumers. It tries to stop work on 
the most important tools for holding down costs as we combat 
global warming. And depending on how you interpret the language 
itself, it could also have a serious chilling effect on our 
international research activities. So it is difficult to 
understand the rationale here, and we certainly have great 
difficulties with the rider.
    Senator Kerry. I do not want to abuse the time too much, 
but there is another problem I'd like to focus on. You go to a 
place like North Dakota, or you go to some northern place, they 
like the fact that it is warmer. Their heating bills are less. 
They figure that their gardens are going to last longer; they 
get a longer summer.
    I mean, there is a psychological difficulty here to get 
people to focus on what may happen to your water tables, to 
your crops, to the movement of whole forests. Do you agree that 
there are very significant down sides that have not yet been 
properly quantified to people so that you can create a 
consensus on this?
    Dr. Lane. Indeed I do agree, Senator. I think this national 
assessment I spoke about, which attempts, for the first time, 
to provide some wisdom on what the regional effects of global 
climate change might be, will help us understand better the 
answer to your question.
    There appear to be some positive benefits to increasing 
temperature in certain parts of the country, certain parts of 
the world. People might like a little warmer evenings, little 
warmer winters, but that is kind of taking an isolationist's 
view. You know, if you put a big wall up around your state or 
your community, if that is the view of the world, then you 
might like it a little warmer.
    On the other hand, there are some very real questions. How 
fast can the ecology keep up with the climate change? So 
suppose the forests that need to move in response to climate 
change cannot move fast enough, and so then they are gone. That 
opens the way for all kinds of invasive species, plant and 
animal, that might be very harmful. So we simply do not know 
the answers to those kinds of questions.
    I would also say that if we think we might be comfy in our 
part of the country because it is getting a little warmer, and 
maybe we can grow crops a little more easily, there are other 
parts of the world are becoming destabilized, people are dying 
from the spread of disease that could well be caused by climate 
change, or significant coastal regions that are increasingly 
densely populated around the world are going under water, if we 
think that is a world in which we all could live comfortably, 
then I think we need to look much more carefully at the 
implications for climate change.
    Senator Kerry. Thank you, Doctor.
    Thank you, Mr. Chairman.
    The Chairman. I just want to say, Senator Kerry, I thank 
you for your involvement and many years on this issue. I am a 
relative newcomer. I appreciate what you have done for many 
years and your participation on this issue, and these hearings 
are very important.
    And I would like to add again, that I think we have tried 
to find a balanced second panel that represent a variety of 
views on this issue, and I think that is the best way we can be 
educated on this issue.
    Senator Brownback.

               STATEMENT OF HON. SAM BROWNBACK, 
                    U.S. SENATOR FROM KANSAS

    Senator Brownback. Thank you very much, Mr. Chairman, and I 
want to congratulate you for once again taking leadership on an 
important and tough topic in typical McCain fashion, grabbing a 
hold and saying, ``Here is something that is tough to do, and 
let us get after it.'' And I applaud you very much and hope you 
hold a series of hearings on this.
    And I also thank Senator Kerry for his leadership for a 
long time on this topic as well.
    Dr. Lane, you have made comments on a number of issues 
here. I have got your testimony and caught the end of it, but I 
want to focus on specifically the issue of CO2 in 
the air, carbon dioxide in the air. And apparently, there are 
some scientific questions that remain out here. There are a 
number of them that are resolved and understood, and I think 
there is unanimity on agreement that there is too much CO2 
in the air. Is there anybody that disagrees with that point?
    Dr. Lane. You could probably find somebody, but I think 
that the consensus is precisely as you stated it.
    Senator Brownback. And that you have in your statements the 
factual--the loading of CO2 that is in the air and 
what has occurred there. And I am a relative newcomer to this 
topic as well, but as I have looked at it, I thought, we can 
disagree on a lot of things, but here is one that I think 
everybody agrees.
    You may disagree about how it all got there, or how you 
pull it out of the air, or some things like that, but there is 
too much CO2, and it would be better if we had less 
in the air. And everybody would agree to that, or I guess, most 
would, although as Senator Kerry was talking about how he 
looked forward to the winter and playing ice hockey, I was 
sitting here thinking I was out cutting holes in the ice to 
water cattle, and I did not like that, as thick as it got.
    It is not that I am saying we should have global warming. I 
do not agree with that. I am not for global warming, but we 
just did not play the ice hockey. I had to cut ice holes.
    [Laughter.]
    Senator Brownback. I put forward a bill along with Senator 
Kerrey from Nebraska that tries to get more carbon 
sequestration taking place in agriculture in this country, a 
domestic component. And we have got an international component 
we are putting forward of trying to have more carbon 
sequestration taking place internationally; the international 
component by tax credits, the domestic component by carbon 
payments to farmers along the model of the CRP, the 
Conservation Reserve Program style.
    It seems to me that if we all agree that we have too much 
CO2 in the air--and you can kind of disagree about 
``Here is the impact, or this is how it got there.'' If you 
just step past that one and say, ``We have got too much 
CO2 in the air. How do we get it out,'' here are a 
couple of ways of doing that.
    And the research is coming along pretty well on no till 
farming, different biomass cropping practices of their ability 
to sequester carbon in the soil. The research is pretty good on 
the amount of carbon that has been released from U.S. soil over 
the years of our agricultural practices so that--we know it has 
the capacity to fix it back, because at one time it had a 
higher degree of carbon in the soil. And we know that as well 
internationally from a number of the forests that have been 
uprooted, that if you started or re-instilled those forests, or 
did not take them down in the first place, you would be 
releasing less carbon into the atmosphere.
    I would like your thoughts about those two approaches on 
addressing the issue of carbon sequestration and taking carbon 
out of the atmosphere.
    Dr. Lane. Senator, this is clearly a very important issue 
on which a great deal of progress has been made in 
understanding the science, but there is much more to do.
    There is, in the Fiscal Year 2001 budget, a significant 
initiative this year and last, for the part of the U.S. Global 
Change Research Program focused on carbon sequestration. It is 
one of the ways that we expect that we will be able to remove 
carbon from the atmosphere.
    The second thing I might say here is that the recent IPCC 
report on land use and land use change and forestry, addresses 
this issue and provides important international consensus on 
what the issues are here, and the remaining scientific 
questions, but also what we know.
    Our understanding of the matter so far is that there is 
significant potential for removal of carbon dioxide through 
changes in land use. Just exactly how much is still quite 
widely debated. The error bars, we say, in the science 
community are rather large on that.
    I think most would feel at this point that even with all 
kinds of reasonable land use changes, and accounting for that, 
it would not be enough to deal with the enormous increases that 
we project in carbon dioxide, but it is very important.
    And I think the only issue then is: How do you deal with 
that in terms of our international discussions? So there are 
some important research questions to continue to get at.
    There are also some serious policy issues in any kind of 
international agreement on dealing with the greenhouse emission 
problem. It is important to have the right agreement on how you 
account for land use in each country's participation in 
reducing greenhouse emissions, or removing carbon dioxide from 
the air. And that is an issue that needs to get sorted out. It 
is clearly going to be very important for both developed and 
developing countries.
    And then I know we have got panelists that can address that 
more precisely. So there are policy issues that are big ones, 
and have to do with how reforestation, and biomass, and no till 
farming, how all that would get counted in any kind of 
international agreement of removal and reduction of greenhouse 
gases.
    Also, even if we knew all we need to know about this, 
actually getting it in practice in our country and in other 
countries is challenging also. And that has major policy 
implications.
    But the issue is important. There is no doubt that this is 
a place we must look to to help with the carbon dioxide 
problem.
    Senator Brownback. So you support doing it, but your 
reservation is that you want it done in a global context.
    Dr. Lane. It must be done in a global context.
    Senator Brownback. I mean, if I could challenge you for a 
minute on that. It seems to me that it would be useful for us 
to start moving that way now, and learning from wide scale 
implementation of those practices, and that that is a benefit.
    I do not see that you do any harm, and you actually do a 
great deal of good, and you probably learn a lot by scaling up 
and doing those things, and doing it now.
    Dr. Lane. Without question, I think the--first of all, the 
science is something we are doing now, and should continue to 
increase our investments in this particular area of carbon 
sequestration. There is no reason the United States should not 
play a leadership role here as it does in so many other areas. 
And so nothing says that if one sees a good thing to do, one 
should not proceed to do it.
    Senator Brownback. Because, I mean, it seems like to me, 
that that almost gets us to Senator Kerry's point about the 
United States showing some leadership on this, whereas there 
has been great concern about the Kyoto Treaty for the reasons 
that you articulated of a number of countries being allowed out 
of it that could offset any sort of gain that the United States 
would do.
    And that you almost could get past that issue as well, and 
in doing something here that is a good and right thing to do, 
that would show strong and aggressive U.S. leadership. And it 
would be a positive thing to do.
    Dr. Lane. But I do want to emphasize that our current 
assessment is that even under ideal land use, it is not 
expected to take care of the whole problem.
    Senator Brownback. No, I understand you on that. And I 
would not submit that it would, although I will submit that the 
research I have looked at, looks like it is very promising and 
will take care of a good portion of the problem. It does not do 
it all, but it has got a chance to really help us out in a very 
significant way. I will look forward to pursuing that with the 
Administration.
    We have the one bill that is out there that will be 
considered. I think as we re-write the farm bill, there will be 
a lot of looks at the issue of carbon sequestration, and I 
would hope that we could do an aggressive support 
internationally to other places that are looking to do the 
right thing. We can help in supporting that as well as keeping 
the carbon from either, first, ever being released, and 
increase the amount that is sequestered into the ground.
    Dr. Lane. Senator, we applaud your efforts here with the 
bill, and look forward to working with you on these matters 
that I just addressed.
    Senator Brownback. I look forward to working with you.
    Mr. Chairman, I have an opening statement I want to submit 
for the record, too, if I could.
    The Chairman. Without objection.
    [The prepared statement of Senator Brownback follows:]

   Prepared Statement of Hon. Sam Brownback, U.S. Senator from Kansas

    Thank you Mr. Chairman. I commend you for holding a hearing on a 
topic as important and as controversial as climate change.
    Scientists generally agree that atmospheric concentrations of 
carbon dioxide are now projected to double by the middle of the next 
century--and continue to rise. This additional carbon in the atmosphere 
could lead to a number of disastrous consequences including 
significantly higher temperatures--which could have a detrimental 
affect on certain forms of agriculture, disruption of ocean currents--
leading to an increase in natural disasters, and coastland destruction. 
The potential effects from global warming are serious and warrant our 
close attention and study.
    The issue of climate change has been most closely linked to the 
international treaty on climate change--the Kyoto Treaty. This treaty 
had several flawed components and is highly unlikely to become policy--
nor should it. However, the issue of climate change should not be 
linked solely to any one treaty. Instead, it is vital that we continue 
our research and look for pro-active measures which can be taken to 
reduce carbon dioxide in the atmosphere without sacrificing our economy 
or our standard of living. Voluntary, incentive-based measures to 
improve the environment should be pursued regardless of the Kyoto 
Treaty. In the debate on climate change, there is a middle ground--it 
doesn't have to be an all or nothing proposition.
    Recently, I have introduced legislation which would provide 
financial incentives to landowners who increase conservation practices 
which help pull carbon dioxide out of the atmosphere and store it as 
carbon in the soil. The Domestic Carbon Storage Incentives Act of 
2000--seeks to encourage the positive contributions to the environment 
made by the agriculture industry.
    My bill focuses on offsetting greenhouse gases through improved 
land management and conservation. As a result, these practices will 
also lead to better water quality, less runoff pollution, better 
wildlife habitat and an additional revenue source for farmers. It is a 
win-win proposition for agriculture and the environment. We must look 
for more of these opportunities if we are to avoid the often discussed 
negative economic impacts that a global climate treaty could bring--and 
research is vital to that goal.
    There are currently efforts to prevent the agencies (USDA in 
particular) and the administration from even researching this issue. I 
understand the complex and controversial nature of climate change. That 
is all the more reason to encourage voluntary efforts to mitigate the 
problem and carefully study the science--not to avoid the issue.
    Again, I commend my colleague for holding this hearing and I look 
forward to the testimony and debate it may inspire.

    The Chairman. Thank you, Dr. Lane. Thank you very much for 
your great work and for appearing before the Committee.
    Dr. Lane. Thank you very much, Mr. Chairman, Senator Kerry.
    The Chairman. Our next panel will be Dr. Ray Bradley, 
Department Chair, Department of Geosciences, University of 
Massachusetts; Dr. John R. Christy, Director of the Earth 
System Science Center, University of Alabama; Dr. Jerry 
Mahlman, Director of Geophysical Fluid Dynamics Laboratory of 
the National Oceanic and Atmospheric Administration; Dr. Kevin 
Trenberth, Director of the Climate Analysis Section of the 
National Center for Atmospheric Research; Dr. Robert Watson, 
Chairman of the Intergovernmental Panel on Climate Changes here 
in Washington, D.C. Thank you.
    Dr. Bradley, please, we will begin with you.

 STATEMENT OF DR. RAY BRADLEY, DEPARTMENT CHAIR, DEPARTMENT OF 
            GEOSCIENCES, UNIVERSITY OF MASSACHUSETTS

    Dr. Bradley. Thank you, Senator. I would like to thank you 
for holding this hearing on a very important issue.
    Studies of instrumental temperature measurements from 
around the world show that the climate of the 20th Century was 
dominated by universal warming. At the end of the 20th Century, 
almost all parts of the Earth had temperatures that were higher 
than when the century began.
    This conclusion is supported by numerous lines of 
environmental evidence, melting of glaciers, retreat of sea 
ice, changes in vegetation, rising of sea level, et cetera. At 
the same time, concentration of greenhouse gases in the 
atmosphere increased to levels that were higher than at any 
time in the last 420,000 years. Carbon dioxide levels are now 
35 to 40 percent higher than they were in the middle of the 
19th Century. This change is largely the result of fossil fuel 
combustion.
    I do not believe that the evidence for 20th Century 
warming, or for these extraordinarily high levels of greenhouse 
gases can be seriously challenged. However, the big question as 
you mentioned is: What has caused the warming? Is it just a 
natural change in climate, and does it have anything to do with 
these increased levels of greenhouse gases?
    With only 100 or 150 years of globally extensive 
instrumentally recorded climate data, we have quite a limited 
perspective on natural climate variability and its relation to 
the phenomena that might have caused climate to change such 
things as we call our forcing factors.
    To obtain a longer perspective requires that we examine 
climate dependant natural phenomena that in some way have 
preserved a record of past climate. The most important of these 
are tree rings, ice cores, banded corals, these laminated lake 
and marine sediments, as well as historical records of past 
weather conditions.
    In recent studies, we have assembled the best of these 
records to produce a global picture of how temperatures changed 
over the last 1,000 years as shown in this figure.
    [Slide.]
    Dr. Bradley. In spite of the uncertainties that such a 
reconstruction entails--and that is--the uncertainty is 
demonstrated here by the yellow shading.
    [Indicating]
    The record shown here of mean annual temperature for the 
Northern Hemisphere, shows the temperature slowly decline over 
the millennium. However, this downward trend changed abruptly 
to a strong warming trend in the--early in the 20th Century.
    And this rate of warming was unprecedented in the last 
1,000 years. The warming continued through the 1990's making 
that decade the warmest in at least 1,000 years. Indeed, 1998 
was arguably the warmest year of the millennium, and 1999 was 
only slightly cooler.
    What can this one perspective on temperature tells us about 
natural climate warming? By comparing it with the records of 
various factors that may have affected the temperature.
    It is a pattern of variations in the amount of energy 
emitted by the sun, major explosive volcanic eruptions, and 
perhaps slight changes in the position of the earth in relation 
to the sun, were responsible for much of the variability of 
temperatures leading up to the 20th Century.
    However, these natural effects were completely overwhelmed 
in the 20th Century by the increasing effective greenhouse 
gases.
    [Slide.]
    Dr. Bradley. Human effects on the climate system variations 
now appear to dominate over natural factors. If the variations 
of these natural factors continue into the future and are 
similar to those of the last 1,000 years, it is unlikely that 
they will be of great importance since the climatic changes 
will be mainly affected by human-induced changes in greenhouse 
gases.
    Earlier I noted that the levels of two important greenhouse 
gases, carbon dioxide and methane, were now higher than at any 
time in the last 420,000 years.
    [Slide.]
    Dr. Bradley. Carbon dioxide levels have risen from fairly 
steady background levels to present day levels in a little over 
a century; on this time scale, almost instantaneously.
    This rate of change has no parallel in historical past, 
just as temperatures recorded in the late 20th Century were 
unprecedented.
    Most of the change in carbon dioxide and the greenhouse 
gases resulted from the growth of world population and the 
insatiable demand for fossil-fuel based energy.
    Given that the world population will almost certainly 
double from the present level of 6 billion within the lifetime 
of those who are currently in kindergarten, unless something is 
done to curb the use of fossil fuel consumption, it seems very 
likely that significant change in climate will occur in the 
near future.
    Consider again the record of temperature over the last 
1,000 years.
    [Slide.]
    Dr. Bradley. An important conclusion of my long term 
climate studies is that until the second half of the 20th 
Century, temperatures generally remained within a half degree 
Celsius, one degree Fahrenheit of the average for the baseline 
which we use, which is 1902 to 1980.
    The latest IPCC long phased projection of future climate 
point to a temperature a temperature rise of .6 to 2.2 Celsius, 
1 to 4 Fahrenheit above 1990 levels by 2050. I think this graph 
puts it all into perspective.
    [Slide.]
    Dr. Bradley. Clearly, these estimates have pretty large 
uncertainties. This shaded area to the right is the model based 
estimates of future change.
    But it is important to know that even the lowest would be 
far beyond the range of temperatures in the last 1,000 years. 
If these estimates are even close to being correct, we are 
heading into uncharted waters relative to the climate over the 
last 1,000 years.
    Should we be concerned that the climate may change 
significantly in the future? I have focused exclusively here in 
the changes of temperature. The temperature change is only one 
component of our overall climate system.
    Changes in temperature are associated with variations in 
rainfall, the amount of snow, frequency of floods and droughts, 
El Nino, or El Ninos events, shifts in storm tracks and 
hurricanes, et cetera.
    Our economy and way of life has become highly dependent on 
certain expectations regarding climate. Much of our 
infrastructure for water supply, for agriculture, and 
transportation, was built on the assumption that climate would 
operate in the future pretty much as it has in the past.
    A relatively small shift in average global or hemispheric 
temperature when it is associated with the atmospheric 
circulation, rainfall patterns, et cetera, can be highly 
disruptive to society. We have seen many examples of such in 
recent decades, yet temperatures that were warm were nowhere 
near the levels that may be reached later on in this century.
    Now, these include extremes of rainfall leading to 
catastrophic flooding in some areas, droughts, exceptional 
wildfires, historically low lake levels elsewhere, as well as 
an increase in windstorms and other weather related disasters. 
Unusual weather events are becoming less uncommon, in fact with 
agriculture, transportation, and commercial activity, a fact 
noted with concern by major international property insurance 
agencies.
    Can we be certain that future climate will involve 
unprecedented risks? Can we be certain? Some argue the 
processes within the climate system will act to compensate for 
the effects of high greenhouse gas levels, some call negative 
feedback events.
    According to this scenario, these feedbacks will help 
maintain the climatic status quo, enabling us to continue to 
contaminate the atmosphere with greenhouse gases.
    There is a small chance that such critics are right in 
which case it would be safe to do nothing. But they may be 
completely wrong and, indeed, the scientific consensus is that 
they are wrong.
    Political decisions, as you well know, inevitably involve 
assessing risk and weighing the consequences of action versus 
inaction. Congress must decide and must weigh the potentially 
catastrophic environmental and commercial consequences of 
future global warming against the costs of limiting fossil fuel 
consumption to reduce these risks.
    Given that it will take many decades to stabilize 
greenhouse gas levels in the atmosphere, even if strong action 
was taken today, as Senator Kerry pointed out, to limit fossil 
fuel consumption, the issue is urgent and demands our 
attention.
    Scientists cannot provide Congress with a certain forecast 
of the future. As our research on global warming continues, our 
understanding will undoubtedly change. But the picture at 
present, is that we are indeed living in climatically unusual 
times, and that the future is likely to be even more unusual. 
And I believe we ignore this prospect at our peril.
    Thank you.
    The Chairman. Thank you very much.
    [The prepared statement of Dr. Bradley follows:]

Prepared Statement of Dr. Ray Bradley, Department Chair, Department of 
                Geosciences, University of Massachusetts

                        CLIMATE IN PERSPECTIVE: 
     HOW DOES PRESENT DAY CLIMATE DIFFER FROM CLIMATES IN THE PAST?

Introduction
    My name is Raymond Bradley. I am the Head of the Department of 
Geosciences, and Director of the Climate System Research Center, at the 
University of Massachusetts, Amherst. My research interests are in 
climate variations during the last century and how these compare with 
variations over longer periods. This involves studying both 
instrumental records of climate, and paleo-records--natural phenomena 
that have in some way registered past changes of climate in their 
structure (for example, tree rings, ice cores, lake sediments, banded 
corals etc). Using such ``proxies'' of climate enables the short 
instrumental record to be extended back in time, so it can be placed in 
a longer-term perspective. Like other witnesses here, I have served on 
many national and international committees related to climate 
variability. Most recently I was Chairman of the Past Global Changes 
Project of the International Geosphere Biosphere Programme (IGBP-
PAGES), a member of the National Research Council Panel on Climate 
Variability on Decade-to-Century Time Scales, and I have been 
contributing author to all of the Intergovernmental Panel on Climate 
Change (IPCC) scientific assessment activities. I have written or 
edited 8 books and numerous articles on climatic change.
    We are living in unusual times. The climate of the twentieth 
century climate was dominated by universal warming; almost all parts of 
the earth had temperatures at the end of the century that were higher 
than when it began. At the same time, the concentration of greenhouse 
gases in the atmosphere increased to levels that were higher than at 
any time in at least the last 420,000 years. These observations are 
incontrovertible. Global warming is real and the levels of greenhouse 
gases (such as carbon dioxide) are now 35-40% higher than they were in 
the middle of the 19th century. This change in greenhouse gas 
concentration is largely the result of fossil fuel combustion. What is 
less certain is whether the observed global warming is due entirely to 
the build-up of greenhouse gases, or to other ``natural'' factors, or 
to a combination of both. Here I provide a longer-term perspective on 
the issue by focusing on the evolution of climate in the centuries and 
millennia leading up to the 20th century. Such a perspective 
encompasses the period before large-scale contamination of the global 
atmosphere and global-scale changes in land-surface conditions. By 
studying both the record of past climate variability and factors that 
may have caused climate to change (``forcing factors''), we can 
establish how the climate system varied under ``natural'' conditions, 
before human effects became significant on a global scale. Although 
there is considerable uncertainty about the rate and magnitude of any 
future warming which may occur as a result of human activities, one 
thing is not in dispute: any human-induced changes in climate will be 
superimposed on a background of natural climatic variations. Hence, in 
order to understand future climatic changes, it is necessary to have an 
understanding of how and why climates have varied in the past. Of 
particular relevance are climatic variations of the last few centuries 
leading up to the recent warming trends observed in instrumental 
records.
    For most parts of the world, instrumental records of climate rarely 
span more than a century. We thus have a very limited perspective on 
climate variability and its relationship to potentially important 
forcing factors. To obtain a longer perspective requires reliance on 
climate-dependent natural phenomena that have preserved, in some way, a 
record of past climate. The most important of these are tree rings, ice 
cores, banded corals, varved lake and marine sediments, as well as 
historical records of past weather conditions (see Appendix 1). In 
recent studies we have assembled the best of these records to produce a 
global picture of how temperature has changed over the last 1000 years 
(Figure 1). It is worth noting that it is not sufficient to select one 
or two records; an extensive network is needed to obtain a global 
assessment. Just as listening to one instrument would not capture the 
full beauty of a symphony, so one can not hope to say anything 
meaningful about global climatic change by using data from only one 
site.




Figure 1. Mean annual temperatures for the northern hemisphere since 
A.D. 1000. Values are shown as anomalies from the average for 1902-1980 
(from M.E. Mann, R.S. Bradley and M.K. Hughes, 1999: Geophysical 
Research Letters, v.26, p.759-762).

    In spite of the uncertainties that such a global reconstruction 
entails, the reconstructed record (of mean annual temperature for the 
northern hemisphere) shows that temperatures slowly declined over the 
millennium, with especially cold conditions in the 15th, 17th and 19th 
centuries. This colder period is generally referred to as the ``Little 
Ice Age,'' when glaciers advanced in most mountainous regions of the 
world. However, the downward trend changed abruptly to a strong warming 
trend early in the 20th century and this rate of warming was 
unprecedented in the last 1000 years. The warming continued through the 
1990s making that decade the warmest in at least 1000 years; indeed, 
1998 was arguably the warmest year of the millennium, and 1999 was only 
slightly cooler.
    What can this longer perspective on temperature tell us about 
natural climate variability? By comparing it with the records of 
factors that may have affected temperature, it is apparent that 
variations of solar irradiance (the total energy emitted by the sun), 
major explosive eruptions and perhaps changes in the position of the 
earth in relation to the sun (slight orbital variations) were 
responsible for much of the variability of temperatures leading up to 
the 20th century. However, these ``natural'' effects were completely 
overwhelmed in the 20th century by the increasing effect of greenhouse 
gases. Human effects on climate system variability now appear to 
dominate over natural factors. If variations in ``natural'' forcings in 
the future are similar to those of the last millennium, it is unlikely 
that they will be of great importance since climatic changes will be 
mainly affected by anthropogenic (human-induced) increases in 
greenhouse gases.
    What significance does the paleo-record of temperature have for 
future climate? An important conclusion from our long-term climate 
studies is that until the second half of the 20th century, temperatures 
generally remained within 0.5+C (1+F) of the average for 
1902-1980 (the arbitrary baseline we used in our studies). The latest 
IPCC model-based projections of future climate point to a temperature 
increase of 0.6 to 2.2+C (1 to 4+F) above 1990 levels by 
2050. Clearly, these estimates have large uncertainties, but it is 
important to note that even the lowest value would be far beyond the 
range of temperatures in the last millennium. If these estimates are 
even close to being correct, we are heading into uncharted waters 
relative to the climate of the last 1000 years.
    Why should we be concerned about global contamination of the 
atmosphere and future changes in climate? Earlier, I noted that the 
levels of two important greenhouse gases (carbon dioxide and methane) 
were now higher than at any time in the last 420,000 years (Figure 2). 
In fact, this conclusion is based on measurements from the longest ice 
core record available (from the Russian Vostok station in Antarctica) 
but it is likely that current levels are higher than at any time for 
several million years. To put this in perspective, recall that it was 
only 10,000 years ago that human society first developed agriculture, 
and 120,000 years ago sabre-toothed tigers roamed what is now Trafalgar 
Square. Yet carbon dioxide levels have risen from fairly steady 
background levels (270ppmv) to present day levels (370ppmv) 
in a little over a century. This rate of change has no parallel in the 
historical past, just as temperatures recorded in the late 20th century 
were unprecedented. Most of the change in CO2 and other 
greenhouse gases resulted from the growth of world population and the 
insatiable demand for fossil fuel-based energy. Given that world 
population will almost certainly double within the lifetime of those 
currently in kindergarten, unless something is done to curb the use of 
fossil fuel consumption, it seems very likely that significant changes 
in climate will occur in the near future.




Figure 2. Changes in atmospheric carbon dioxide and methane levels in 
the atmosphere over the last 420,000 years (from gas bubbles trapped in 
an ice core, from Vostok, Antarctica).

    Should we be concerned that the climate may change significantly in 
the future? Here I have focused exclusively on changes in temperature, 
but temperature change is only one component of our overall climate 
system. Changes in temperature are associated with variations in 
rainfall and the amounts of snow, shifts in storm tracks and hurricanes 
etc. From the record of past climate, we know that a relatively small 
overall change in global temperature can have significant environmental 
effects. The ``Little Ice Age'' was characterized by dramatic changes 
in ice cover in mountain regions throughout the world. But historical 
records from lowland areas of Europe also document more extensive snow 
cover, longer periods when rivers and lakes were frozen over and 
frequent cold, wet summers, with disastrous consequences for 
agriculture, leading to social disruption and political upheavals. Such 
changes all occurred with an overall change in average hemispheric 
temperature of less than 1+F. Of course, in trying to anticipate the 
effects of future climate change, we are looking at the consequences of 
warmer, not colder conditions but the implication is the same--even a 
small shift in average global or hemispheric temperature, with its 
associated changes in atmospheric circulation, rainfall patterns etc., 
can be highly disruptive to society. We have seen many examples of such 
anomalies in recent decades, yet temperatures, though warm, were 
nowhere near the levels that may be reached later in this century. 
These include extremes in rainfall, leading to catastrophic flooding in 
some areas, and droughts, exceptional wildfires and historically low 
lake levels elsewhere, as well as an increase in windstorms and other 
weather-related disasters. Unusual weather events are becoming less 
uncommon, impacting agriculture, transportation and commercial 
activity. Of course, such disasters have always occurred to some 
extent, but the frequency of extremes has increased in recent years 
throughout the world, leading major insurance companies to express 
grave concerns about their exposure to these unprecedented risks (note 
that these risks are in addition to the costs due to increased 
development). Munich Re, one of the world's largest re-insurance firms 
recently reported:

        ``1999 fits exactly into the long-term pattern of increasing 
        losses from natural catastrophes . . . insured losses came to 
        $22bn. This is the second highest figure ever recorded . . . 
        windstorms were responsible for 80% of the insured losses while 
        earthquakes accounted for 10%, floods 6%, and other events like 
        forest fires, frost, and heat waves around 4% . . . In view of 
        the fact that the signs of climate change and all its related 
        effects are becoming more and more discernible . . . if . . . 
        meteorological extremes like torrential rain, windstorms, and 
        heat waves continue to increase and the rise in sea level 
        accelerates, many regions of the world will be in immediate 
        danger . . .''

    Can we be certain that future climate will involve unprecedented 
risks? Some argue that processes within the climate system will act to 
compensate for the effects of higher greenhouse gas levels (so-called 
negative feedback effects). According to this scenario, these feedbacks 
will help maintain the climatic status quo enabling us to continue to 
contaminate the atmosphere ad infinitum. There is a small chance that 
such critics are right, in which case it would be safe to do nothing. 
But they may be completely wrong, and indeed the scientific consensus 
is that they are wrong. Political decisions inevitably involve 
assessing risk and weighing the consequences of action versus inaction. 
Just as Congress must decide if the (perhaps small) risk of a rogue 
nation launching a nuclear missile at the United States (resulting in a 
catastrophe) is worth avoiding by spending large sums of money on a 
space defense system, so it must weigh the potentially catastrophic 
environmental and commercial consequences of future global warming 
against the costs of curbing fossil fuel consumption to reduce these 
risks. Scientists cannot provide Congress with a certain forecast of 
the future and as research on global warming continues, our 
understanding will undoubtedly change. But the picture at present is 
that we are indeed living in climatically unusual times, and that the 
future is likely to be even more unusual.
Appendix 1.
    Tree ring data include both ring width and ring density variations. 
Records are available from all continental areas (except Antarctica) 
though most series are from outside the tropical regions. High latitude 
and high altitude trees generally provide estimates of past 
temperature; trees in dry regions generally provide estimates of past 
precipitation, though even in wetter areas, records of rainfall changes 
can sometimes be obtained.
    Ice cores provide many records of past climate but changes in 
oxygen isotopes in the ice, accumulation rate and (summer) melt 
conditions are of primary interest in examining recent centuries. In 
polar regions oxygen isotopes are generally considered to be an 
indicator of annual temperature. Other useful climate indicators 
include the fraction of a core containing `melt features' (produced by 
the re-freezing of percolating surface melt water) which provides a 
useful index of summer temperature conditions, and accumulation rate 
changes, which indicate past snowfall amounts.
    Corals provide uniquely detailed records of sea-surface 
temperatures, from changes in the (temperature-dependent) oxygen 
isotopes in the carbonate skeletons of the corals. In some cases, 
salinity variation is the most important factor influencing isotope 
content, in which case the changes reflect precipitation and runoff 
from adjacent continental regions.
    Varved sediments, from both lake and marine environments, are 
annual layers that record past environmental conditions in the lake or 
oceanic region. There are few ocean areas where varved sediments are 
known to occur (generally upwelling coastal regions where there is 
little oxygen in the deep waters) but varved lake sediments are found 
on all continents. Providing the records are clearly annual and a 
strong climatic signal can be demonstrated, these records can provide 
useful data from many regions of the world.
    Historical records can, potentially, provide seasonal estimates of 
past climate over wide geographic regions, though at present only 
European and East Asian sources have been adequately studied.

Details of how these and other paleoclimate proxies are used to 
reconstruct past climates can be found in the book ``Paleoclimatology'' 
by R.S. Bradley (1999, Academic Press).

    The Chairman. Dr. Christy, welcome.

          STATEMENT OF DR. JOHN R. CHRISTY, DIRECTOR, 
       EARTH SYSTEM SCIENCE CENTER, UNIVERSITY OF ALABAMA

    Dr. Christy. Thank you, Mr. Chairman. I am pleased to be 
here testifying before this Committee.
    By the way, I am from the University of Alabama in 
Huntsville. We do not have football team. Ice hockey, in fact, 
is our favorite sport.
    [Laughter.]
    Dr. Christy. Considering the varying levels of skepticism 
represented on this panel, it would be apparent that I am very 
likely the witness that is most skeptical, but not agnostic, 
regarding our ability to predict future climate. And I hope to 
demonstrate why this is so.
    The universal feature of climate model projections of 
global temperature changes due to greenhouse gas increases is a 
rise in the temperature of the atmosphere from the surface to 
about 30,000 feet.
    This temperature rise itself is projected to be significant 
at the surface, with increasing magnitude as one rises in the 
atmosphere, which we call the troposphere.
    Over the past 21-years various calculations of surface 
temperature, indeed, show a rise between .45 and .65 of a 
degree. This represents about half of the total rise since the 
end of the 19th Century.
    In the troposphere, however, various estimates, which 
include satellite data that Dr. Roy Spencer of NASA and I 
produced, show only a very slight warming between .09 and .18 
of a degree, a rate less than one-third that observed at the 
surface.
    So rather than seeing a rise in temperature that increases 
with altitude as climate models project, we see that in the 
real world since 1979, the rise decreases substantially with 
altitude.
    The most recent modeling efforts which attempt to explain 
this disparity suggest that when some of the actual climate 
processes are factored in, and I emphasize ``some,'' such as 
the Mount Pinatubo eruption, the models looked like they came 
close to reality.
    On closer inspection of these studies, however, one finds 
that the apparent agreement was achieved only by comparing 
apples with oranges. The model experiments included some major 
processes, but not all major processes.
    When those additional processes were included, like real El 
Ninos, the climate models did not produce the observed global 
average vertical temperature changes. In other words, 60 
percent of the atmosphere is going in a direction not predicted 
by models.
    And that, in my view, is a significant missing piece of the 
climate puzzle that introduces considerable uncertainty of the 
models' utility regarding predicting temperatures.
    Now, it is certainly possible that the inability of the 
climate models to predict what happened over the past 21 years 
may only indicate that the climate experiences large natural 
fluctuations in the vertical temperature structure.
    However, this means that any attention drawn to the surface 
temperature rise for the past two decades must, I repeat must, 
also acknowledge the fact that 60 percent of the atmospheric 
mass that was projected to warm did not.
    This vertical temperature situation is a curious and 
unexplained issue regarding global average temperatures. But we 
do not live 30,000 feet in the atmosphere, and we do not live 
in a global average. We live in a specific place, city, state, 
and so on.
    Local and regional projections of climate are very 
difficult and challenging. An example from North Alabama that I 
wanted to use here, only illustrates the difficulty in 
providing regional estimates of what might happen.
    A few climate models have attempted to reproduce the 
temperature changes over the last 150 years, since the 19th 
century. These are complex models with solar changes, carbon 
dioxide increases, sulfate pollution, oceans, and so on.
    They indicate that since the 1890's we in North Alabama 
should have experienced a warming of about two degrees.
    Observations show we have actually experienced a cooling of 
over two degrees. The models may have done fairly well at the 
global average surface temperature, and may have done 
acceptably well in several geographic locations, but my opinion 
in the southeast, is that there was false information there. I 
am not hitting climate models in a critical way. I am showing 
the challenge that is there on reproducing climate results on a 
regional basis.
    If in trying to reproduce the past we see such model 
errors, one must assume that predicting the future would 
produce similar opportunity for regional errors. I want to 
encourage the Committee to be suspicious of media reports in 
which weather extremes are given as proof of human-induced 
climate change.
    Weather extremes occur somewhere all the time. For example, 
you have seen recent reports perhaps about the U.S. surface 
temperature data showing January through March the highest ever 
in one surface temperature data set of the United States, not 
others.
    The satellite data provides information for the entire 
globe and show that, yes, indeed, the tropospheric temperatures 
were well above average for the 48 contiguous states. However, 
most of the globe experienced below average temperatures in 
that massive bulk of the atmosphere.
    It was our turn to be warm while in places such as the 
equatorial oceans and the Sahara Desert, it was their turn to 
be cool. Other climate data give us similar information. 
Hurricanes have not increased. Tornadoes have not increased. 
Droughts and wet spells have not statistically increased, or 
decreased.
    Let me quickly add, there are many more people and much 
more wealth in the paths of these destructive events, so losses 
have increased but that is not due to climate change. Deaths in 
U.S. cities are no longer correlated with high temperatures, 
though deaths still increase during cold temperatures.
    When looking at data such as these, especially on a 
regional basis, climate change, and in particular, the human 
factor of climate change, is very difficult to detect at all.
    I will close with three questions and a plea. Is the 
climate changing? Yes, it always has and it always will, but it 
is very difficult to detect on decadal time scales.
    Are climate models useful? Yes, and improving. At this 
point, their utility is mostly in global average scale, yet 
there are still some significant shortcomings even there.
    Is that portion of climate change due to human factors 
good, bad, or inconsequential? And that, no one knows, although 
we do know that the plant world thrives on additional CO2 
in the atmosphere.
    What I do know is that we depend on data to answer these 
questions. The global data network is decaying at the very time 
we need it most.
    If the richest country in the world could do anything, it 
would be to step up efforts to monitor the present global 
climate, reconstruct the past climate, assure easy and timely 
access to data, and to support scientists to study the data on 
which to depend such important answers.
    Thank you.
    The Chairman. Thank you very much, Dr. Christy.
    [The prepared statement of Dr. Christy follows:]

         Prepared Statement of Dr. John R. Christy, Director, 
           Earth System Science Center, University of Alabama

    Mr. Chairman and Committee Members, I am pleased to accept your 
invitation to offer information on climate change along with my own 
assessment. I am John Christy, Professor of Atmospheric Science and 
Director of the Earth System Science Center at the University of 
Alabama in Huntsville.

Carbon Dioxide
    The concentration of carbon dioxide (CO2) is increasing 
in the atmosphere due primarily to the combustion of fossil fuels. It 
is our great fortune (because we produce so much of it) that CO2 
is not a pollutant. In simple terms, CO2 is plant food. The 
green world we see around us would disappear if not for atmospheric 
CO2. These plants largely evolved at a time when the 
atmospheric CO2 concentration was many times what it is 
today. Indeed, numerous studies indicate the present biosphere is being 
invigorated by the human-induced rise of CO2. In and of 
itself, therefore, the increasing concentration of CO2 does 
not pose a toxic risk to the planet. It is the secondary impact of 
CO2 that may present challenges to human life in the future. 
It has been proposed that CO2 increases could cause climate 
change of a magnitude beyond what naturally occurs that would force 
costly adaptation or significant ecological stress. For example, sea 
level rise and/or reduced rainfall would be two possible effects likely 
to be costly to those regions so affected. Data from the past and 
projections from climate models are employed to provide insight on 
these concerns.

Climate Models
    Climate models attempt to describe the ocean/atmospheric system 
with equations which approximate the processes of nature. No model is 
perfect because the system is incredibly complex. One modest goal of 
model simulations is to describe and predict the evolution of the 
ocean/atmospheric system in a way that is useful to discover possible 
environmental hazards which lie ahead. The goal is not to achieve a 
perfect forecast for every type of weather in every unique geographic 
region, but to provide information on changes in large-scale features. 
If in testing models for current large-scale features one finds 
conflict with observations, this suggests that at least some 
fundamental process, for example heat transfer, are not adequately 
described in the models.

Global Averages
    A universal feature of climate model projections of global average 
temperature changes due to enhanced greenhouse gasses is a rise in the 
temperature of the atmosphere from the surface to 30,000 feet. This 
temperature rise itself is projected to be significant at the surface, 
with increasing magnitude as one rises through this layer called the 
troposphere. Most people use the term Global Warming to describe this 
temperature rise.
    Over the past 21-years various calculations of surface temperature 
do indeed show a rise between +0.45 and +0.65+F (0.25 and 0.36+C 
depending on which estimate is used.) This represents about half of the 
total surface warming since the 19th century. In the troposphere, 
however, the values, which include the satellite data Dr. Roy Spencer 
of NASA and I produce, show only a very slight warming between +0.09 
and +0.18+F (+0.05 and +0.10+C)--a rate less than a third that observed 
at the surface. So, rather than seeing a warming that increases with 
altitude as climate models project, we see that in the real world the 
warming substantially decreases with altitude.
    It is critically important in my view to correctly model 
tropospheric temperature changes because this is where much of the 
global atmospheric heat is moved about and eventually expelled to 
space. This layer also has a strong influence on surface temperature 
through radiation processes. It is conceivable that a model which 
retains too much heat in the troposphere, may also retain too much at 
the surface.




    The most recent modeling attempts which seek to reconcile this 
disparity suggest that when some of the actual climate processes are 
factored in, the models come very close to reality. These processes are 
events such as the Mt. Pinatubo eruption and slow changes such as ozone 
depletion.
    On closer inspection of these studies, however, one finds that the 
apparent agreement was achieved only by comparing apples with oranges. 
The model experiments included some major processes, but not all major 
processes. When those additional processes are also factored in, such 
as real El Ninos, the climate models do not produce the observed global 
average vertical temperature changes observed since 1979. In other 
words, the temperature of 60% of the atmosphere appears to be going in 
a direction not predicted by models. That, in my view, is a significant 
missing piece of the climate puzzle which introduces considerable 
uncertainty about a model's predictive utility.
    It is certainly possible that the inability of the present 
generation of climate models to reproduce the reality of the past 21 
years may only reflect the fact that the climate experiences large 
natural variations in the vertical temperature structure over such time 
periods. By recognizing this however, the implication is that any 
attention drawn to the surface temperature rise over the past two 
decades must also acknowledge the fact that 60% of the atmospheric mass 
has not similarly warmed.

Regional Averages
    This disparity between observations and model results is a curious 
and unexplained issue regarding the global average vertical temperature 
structure. But we do not live 30,000 feet in the atmosphere, and we do 
not live in a global average surface temperature. We live in specific 
places, cities, states and regions. Local and regional projections of 
surface climate are very difficult and challenging. An example from 
Alabama's past is useful here only to illustrate the difficulty of 
providing local predictions with a high level of confidence.
    A few of the present set of climate models have attempted to 
reproduce the distribution of actual surface temperatures since the 
19th century. These complex models incorporate solar changes, 
increasing carbon dioxide, sulfate pollution and so on. They indicate 
that since the 1890's we in North Alabama should have experienced a 
warming of about 2+F (1+C). The truth is that we have actually 
experienced a cooling of over 2+F (1+C).\1\ The model may have done 
fairly well in the global average, and may have done acceptably well in 
many geographic locations, but in my opinion it provided false 
information for those of us in the Southeast. If in trying to reproduce 
the past we see such model errors, one must assume that predicting the 
future would produce similar opportunities for errors on a regional 
basis.
---------------------------------------------------------------------------
    \1\ Data have been adjusted for all station moves, time of 
observation biases and instrument changes.




Weather Extremes and Climate Change
    I want to encourage the Committee to be suspicious of media reports 
in which weather extremes are given as proof of human-induced climate 
change. Weather extremes occur somewhere all the time. For example, you 
may have seen a recent report based on one version of the U.S. surface 
temperature data stating that January through March of this year was 
the hottest ever recorded. The satellite data provide information for 
the entire globe and show that indeed tropospheric temperatures were 
much above average over the lower 48 states. However, most of the globe 
experienced below average temperatures in that massive bulk of the 
troposphere. It was our turn to be warm while in places such as the 
equatorial oceans and the Sahara Desert it was their turn to be cold.




    Has hot weather occurred before in the US? All time record high 
temperatures by states begin in 1888. Only eleven of the states have 
uniquely seen record highs since 1950 (35 occurred prior to 1950, 4 
states had records occurring both before and after 1950.) Hot weather 
happens. Similar findings appear from an examination of destructive 
weather events. The intensity and frequency of hurricanes have not 
increased. The intensity and frequency of tornadoes have not increased. 
(Let me quickly add that we now have more people and much more wealth 
in the paths of these destructive events so that the losses have 
certainly risen, but that is not due to climate change.) Droughts and 
wet spells have not statistically increased or decreased. Last summer's 
drought in the Northeast was remarkable in the sense that for the 
country as a whole, the typical percentage area covered by drought was 
below average. Deaths in U.S. cities are no longer correlated with high 
temperatures, though deaths still increase during cold temperatures.




    When considering information such as indicated above, one finds it 
difficult to conclude the climate change is occurring in the U.S. and 
that it is exceedingly difficult to conclude that part of that change 
might have been caused by human factors.
    In the past 100 years, sea level has risen 6 in.  4 in. 
(15 cm  10 cm) and is apparently not accelerating. Sea 
level also rose in the 17th and 18th centuries, obviously due to 
natural causes, but not as much. One of my duties in the office of the 
State Climatologist is to inform developers and industries of the 
potential climate risks and rewards in Alabama. I am very frank in 
pointing out the dangers of beach front property along the Gulf Coast. 
A sea level rise of 6 in. over 100 years, or even 50 years is minuscule 
compared with the storm surge of a powerful hurricane like Fredrick or 
Camille. Coastal areas threatened today will be threatened in the 
future. The sea level rise, if it continues, will be very slow and thus 
give decades of opportunity for adaptation, if one is able to survive 
the storms.

Summary
    I will close with three questions and a plea.
    Is the climate changing? Yes, it always has and it always will, but 
it is very difficult to detect on decadal time scales or on regional 
spatial scales.
    Are climate models useful? Yes, and improving. At this point, their 
utility is mostly related to global averages, though shortcomings are 
still apparent.
    Is that portion of climate change due to human factors good, bad or 
inconsequential? No one knows (although the plant world thrives on 
increases in carbon dioxide because CO2 is plant food.)
    What we do know is that we depend on data to answer these 
questions. The global data network is decaying at the very time we need 
it most. If the richest country in the world could do something, it 
would be to lead out in monitoring the present climate, in 
reconstructing the past climate, in assuring easy and timely access to 
the data . . . and in supporting scientists to study the data on which 
depend such important answers.

    The Chairman. Dr. Mahlman, is that the proper 
pronunciation?
    Dr. Mahlman. Yes, it is.
    The Chairman. Welcome, Doctor. Would you pull the 
microphone over? Thank you.

  STATEMENT OF DR. JERRY MAHLMAN, DIRECTOR, GEOPHYSICAL FLUID 
     DYNAMICS LABORATORY, NATIONAL OCEANIC AND ATMOSPHERIC 
                         ADMINISTRATION

    Dr. Mahlman. Thank you, Mr. Chairman. We have long known 
that buildups of atmospheric carbon dioxide and other gases 
have the potential to warm earth's climate, through the so-
called greenhouse effect.
    Today, I will discuss the modeling of projections of 
climate changes due to these increases in greenhouse gases for 
the time around the middle of this 21st Century. Because I 
speak with credentials as a physical scientist, I do not offer 
personal opinions on what society should do about these 
projected climate changes.
    Societal actions to greenhouse warming involve value and 
policy judgments that are beyond the realm of climate science. 
At the onset, please recognize that a major international 
effort to assess climate warming was completed in 1996. This is 
the IPCC assessment that Dr. Lane referred to earlier.
    This was the most widely accepted assessment ever on 
climate change. The 2001 climate assessment will be completed 
soon. I expect only small changes in its major conclusions, 
mainly concerning some very important increases in scientific 
confidence over the last 5 years.
    I strongly recommend your use of these IPCC assessments as 
a foundation for your own evaluations. I also recommend their 
use as a point of departure for evaluating the credibility of 
opinions that disagree with the IPCC assessments. IPCC is not 
an infallible system, in that sciences is always self 
corrective, but opinions that disagree with them have the 
burden to make sense.
    My information I present today is derived from the 
strengths and weaknesses of climate models, the strengths and 
weaknesses of climate theory, and the strengths and weaknesses 
of widespread observations of the climate system.
    Climate models have improved in their ability to simulate 
the climate and its natural variations. Unfortunately, 
important uncertainties due to deficiencies in our scientific 
understanding and in our computing power still remain. 
Nevertheless, significant progress is expected over the next 
decade.
    However, let me say at the onset, none of the uncertainties 
that I discuss today can make current concerns about greenhouse 
warming go away. This problem is very real, and is guaranteed 
to be with us for a very long time.
    I will give my evaluation of current model projections of 
climate change for the middle of the next century by my setting 
of simple betting odds. By ``virtually certain,'' a phrase used 
earlier by Senator Kerry, I mean, that there is no plausible 
alternative that we know of. In effect, the bet would be off 
the books.
    ``Very probable'' means that I estimate a nine out of ten 
chance that this will happen within the range projected. 
``Probable'' implies that I am setting the odds at about a two 
out of three chance, while uncertain means a plausible effect, 
but which lacks appropriate evidence. I will give examples of 
all of these. So essentially, I set the betting odds; you 
choose your bet.
    My analysis is presented in decreasing levels of scientific 
confidence. Human-caused increasing greenhouse gases in the 
atmosphere is virtually certain. There is no remaining real 
doubt that increasing greenhouse gases are due to human 
activities.
    Radiative effects of increased greenhouse gases is 
virtually certain. Greenhouse gases absorb and reradiate 
infrared radiation, the heat radiation that leaves the planet 
all the time, that makes it cool off at night. Independent of 
other factors, this acts to produce an increased heating on the 
planet.
    A doubling of atmospheric carbon dioxide expected, 
virtually certain. Atmospheric carbon dioxide amounts are now 
expected to at least double over pre-industrial levels in this 
century. Currently, emission growth is on track to quadruple 
carbon dioxide levels.
    Long time to draw down excess carbon dioxide, virtually 
certain. We know that it takes decades to centuries to produce 
a large buildup of greenhouse gases. Much less appreciated is 
that a return to normal from high carbon dioxide levels in the 
atmosphere would require many additional centuries, perhaps 
more than 1,000 years.
    Global surface warming over the past century, virtually 
certain. The measured 20th century warming in the surface 
temperature records of over one degree Fahrenheit is 
undoubtedly real. Its cause is very probably due mostly to 
added greenhouse gases. No other hypothesis today is nearly as 
creditable.
    Future global-mean surface warming, very probable. Assuming 
business as usual for the middle of the next century, global-
mean surface warming is estimated to be in the range of two to 
six degrees Fahrenheit, with continued increases for the rest 
of the century. The largest uncertainty is due to the effects 
of clouds.
    Increased summertime heat index, very probable. In warm 
moist subtropical climates, such as Washington, D.C., the 
summertime heat index effect is expected to magnify the warming 
impact felt by humans by an additional 50 percent.
    Rise in global sea level, very probable. A further rise of 
four to twelve inches in global mean sea level by the year 2050 
is estimated due simply to the thermal expansion of warmer sea 
water. As the water warms, it occupies more volume. This does 
not include the effects of possible melting of Greenland ice. 
Continued sea level rise is expected for many centuries, 
probably to much higher levels.
    Disappearance over the last 50 years of Arctic sea ice, 
very probably, due to human activities. There is some 
uncertainty about how much humans have had to do with that, but 
it is pretty well conceded that the models are now calculating 
that properly.
    Summer mid-continental dryness, probable. Model studies 
project a marked decrease in soil moisture over summer mid-
latitude continents. This projection remains sensitive to model 
assumptions, thus, I give it a two out of three bet.
    Increased tropical storm intensities, probable. A warmer, 
wetter atmosphere will likely lead to increased intensities of 
tropical storms such as hurricanes, and substantial increases 
in their precipitation rates.
    We still know little about changes in the number of 
hurricanes. When people tell you there will be more hurricanes, 
we do not know where those kind of statements come from. So, 
when people say we are not finding increased numbers of 
hurricanes, I do not understand that either.
    Increased numbers of weather disturbances, uncertain. 
Although many speak of more large-scale storms, such as 
northeasters, and so forth, there is no solid evidence for 
this, in either models or theory.
    Global and regional details for the next 25 years, 
uncertain. The predicted warming, up to now, is not yet large 
compared to natural climate fluctuations. We can find it in the 
data, but it does not yet fully dominate. On these shorter time 
scales, the natural fluctuations can artificially reduce or 
enhance apparent measured greenhouse warming signals, 
especially so on regional scales.
    Endorsing Dr. Christy's point, but raising the bet, 
variations on decadal scales at a particular region can be due 
to completely natural effects, California and Southwest United 
States are particularly vulnerable to these natural 
fluctuations.
    Even though these uncertainties are daunting, important 
advances have already been achieved in observing, 
understanding, and modeling the climate. Today's models can 
simulate many aspects of climate and its changes.
    Although major progress has been made, much more needs to 
be learned. More efforts are needed worldwide to provide a 
long-term climate measuring system that is really designed to 
do the job.
    Focused research into climate processes must be continued. 
Theories must be formulated and re-evaluated in the light of 
newer data. Climate modeling efforts must receive resources 
that are in balance with the broader scientific programs.
    In my view, the U.S. Global Change Research Program has 
already made important progress on these fronts. However, 
patient and sustained efforts will be required in the years 
ahead.
    I endorse Dr. Lane's balanced presentation of this vital 
interagency effort under the U.S. Global Change Research 
Program. Through long-term research and measurements, 
uncertainties will decrease, and confidence for projections of 
climate change will increase.
    In summary, the greenhouse warming effect is quite real. 
The state of the science is strong, but important uncertainties 
do remain. Finally, it is a virtually certain bet that this 
problem will refuse to go away no matter what is said or done 
about it over the next 5 to 10 years.
    Thank you, Mr. Chairman.

 Prepared Statement of Dr. Jerry Mahlman, Director, Geophysical Fluid 
  Dynamics Laboratory, National Oceanic and Atmospheric Administration

    Mr. Chairman:
    My name is Jerry Mahlman. I am the Director of the Geophysical 
Fluid Dynamics Laboratory of NOAA. For over thirty years our Laboratory 
has been a world leader in modeling the earth's climate. I will 
evaluate scientific projections of climate change as well as their 
current uncertainties.
    We have long known that buildups of atmospheric carbon dioxide and 
other gases have the potential to warm earth's climate, through the so-
called ``greenhouse'' effect. Today, I will discuss modeling the 
projections of climate changes due to these increasing greenhouse gases 
for a time around the middle of the century.
    Because I speak with credentials as a physical scientist, I do not 
offer personal opinions on what society should do about these projected 
climate changes. Societal actions in response to greenhouse warming 
involve value and policy judgements that are beyond the realm of 
climate science.
    At the onset, please recognize that a major international effort to 
assess climate warming was completed in 1996. This is ``The 
Intergovernmental Panel on Climate Change Assessment'' (IPCC). The IPCC 
was established in 1988 by the United Nations Environment Programme and 
the World Meteorological Organization to assess the available 
information on climate change and its environmental and economic 
impacts. This was the most widely accepted assessment ever on climate 
change. The 2001 IPCC Assessment will be completed soon. I expect only 
small changes in its major conclusions, mainly concerning some 
important increases in scientific confidence.
    I strongly recommend your use of the IPCC assessments as a 
foundation for your own evaluations. I also recommend their use as a 
point of departure for evaluating the credibility of opinions that 
disagree with them.
    My information is derived from the strengths and weaknesses of 
climate models, climate theory, and widespread observations of the 
climate system. Climate models have improved in their ability to 
simulate the climate and its natural variability. Unfortunately, 
important uncertainties remain due to deficiencies in our scientific 
understanding and in computer power. However, significant progress is 
expected over the next 10 years.
    However, let me say at the outset: None of the uncertainties I will 
discuss can make current concerns about greenhouse warming go away. 
This problem is very real and will be with us for a very long time.
    I will give my evaluation of current model predictions of climate 
change in the middle of the next century by setting simple ``betting 
odds.'' By ``Virtually Certain,'' I mean that there is no plausible 
alternative; in effect, the bet is off the books. ``Very Probable'' 
means I estimate about a 9 out of 10 chance that this will happen 
within the range projected; ``Probable'' implies about a 2 out of 3 
chance. ``Uncertain'' means a plausible effect, but which lacks 
appropriate evidence. Essentially, I set the odds; you choose your bet. 
My analysis is presented in decreasing levels of confidence.

Human-Caused Increasing Greenhouse Gases (virtually certain)
    There is no remaining doubt that increasing greenhouse gases are 
due to human activities.
Radiative Effect of Increased Greenhouse Gases (virtually certain)
    Greenhouse gases absorb and reradiate infrared radiation. 
Independent of other factors, this property acts to produce an 
increased heating effect on the planet.

A Doubling of Carbon Dioxide Expected (virtually certain)
    Atmospheric carbon dioxide amounts are expected to double over pre-
industrial levels in this century. Current emissions growth is on track 
to quadruple atmospheric carbon dioxide.

Long Time to Draw Down Excess Carbon Dioxide (virtually certain)
    We know that it takes decades to centuries to produce a large 
buildup of greenhouse gases. Much less appreciated is that a ``return 
to normal'' from high carbon dioxide levels would require many 
additional centuries.

Global Surface Warming Over the Past Century (virtually certain)
    The measured 20th century warming in the surface temperature 
records of over one degree fahrenheit is undoubtedly real. Its cause is 
very probably due mostly to added greenhouse gases. No other hypothesis 
is nearly as credible.

Future Global-Mean Surface Warming (very probable)
    For the middle of the next century, global-mean surface warming is 
estimated to be in the range of 2 to 6+ fahrenheit, with continued 
increases for the rest of the century. The largest uncertainty is due 
to the effects of clouds.

Increased Summertime Heat Index (very probable)
    In warm, moist subtropical climates the summertime heat index 
effect is expected to magnify the warming impact felt by humans by an 
additional 50%.

Rise in Global Mean Sea Level (very probable)
    A further rise of 4-12 inches in mean sea level by the year 2050 is 
estimated due to thermal expansion of warmer sea water. Continued sea 
level rise is expected for many centuries, probably to much higher 
levels.

Summer Mid-Continental Dryness and Warming (probable)
    Model studies predict a marked decrease of soil moisture over 
summer mid-latitude continents. This projection remains sensitive to 
model assumptions.

Increased Tropical Storm Intensities (probable)
    A warmer, wetter atmosphere will likely lead to increased 
intensities of tropical storms, such as hurricanes. We still know 
little about changes in the number of hurricanes.

Increased Numbers of Weather Disturbances (uncertain)
    Although many speak of more large-scale storms, there is still no 
solid evidence for this.

Global and Regional Details of the Next 25 Years (uncertain)
    The predicted warming up to now is not yet large compared to 
natural climate fluctuations. On these shorter time scales, the natural 
fluctuations can artificially reduce or enhance apparent measured 
greenhouse warming signals, especially so on regional scales.
    Even though these uncertainties are daunting, important advances 
have already been achieved in observing, understanding, and modeling 
the climate. Today's models can simulate many aspects of climate and 
its changes. Although major progress has been made, much more needs to 
be learned. More efforts are needed world-wide to provide a long-term 
climate measuring system. Focussed research into climate processes must 
be continued. Theories must be formulated and re-evaluated in the light 
of newer data. Climate modeling efforts must receive resources that are 
in balance with the broader scientific programs.
    The U.S. Global Change Research Program has already made important 
progress on these fronts. However, patient, sustained efforts will be 
required in the years ahead.
    Through long-term research and measurements, uncertainties will 
decrease and confidence for predicting climate changes will increase.
    In summary, the greenhouse warming effect is quite real. The state 
of the science is strong, but important uncertainties remain. Finally, 
it is a ``virtually certain'' bet that this problem will refuse to go 
away, no matter what is said or done about it over the next five years.
    Thank you, Mr. Chairman. That concludes my testimony.

    The Chairman. Thank you, Dr. Mahlman.
    Dr. Trenberth, welcome.

        STATEMENT OF DR. KEVIN E. TRENBERTH, DIRECTOR, 
         CLIMATE ANALYSIS SECTION, NATIONAL CENTER FOR 
                      ATMOSPHERIC RESEARCH

    Dr. Trenberth. Thank you, Senator.
    I recently served on the National Research Council Panel 
that produced the report that has been referred to, this report 
here on reconciling observations of global temperature change. 
And I was asked in my comments to especially address the 
findings of this particular Committee.
    The first thing I would say is that the mere need for this 
report highlights the fact that we do not have a global climate 
observing system. Most of the observations that are used for 
climate purposes are made for weather or aviation purposes. The 
observations are made for purposes other than for climate.
    Heroic efforts are, therefore, needed, it turns out, to 
reconstruct exactly what has happened even in the instrumental 
period, let alone what has happened in the last 1,000 years.
    What we do conclude in this report is that in the past 20 
years, global mean surface temperatures have been rising at a 
rate as large as any that has been observed within the 
historical record.
    The surface temperatures have increased. A central number I 
would put on it is about 1.3 degrees Fahrenheit over the past 
century. 1998 is the warmest year, as has been mentioned 
several times, and the 1990's is the warmest decade. And 
melting glaciers and rising sea level provides additional 
support that these effects are real.
    Now this rapid warming at the earth's surface is in 
contrast, as John Christy has mentioned, to the trend in the 
satellite record, which only began though in 1979. Now the 
satellite record measures the temperature of about the lowest 
five miles of the atmosphere. It is not measuring the same 
thing as the temperature of the surface. It is an indirect 
measurement, and it is inferred from radiation that is emitted 
by oxygen molecules and it is sampled by a microwave sound 
unit.
    So these are measurements in the microwave frequencies, and 
these measurements are made aboard polar orbiting satellites.
    Before I go on to summarize some aspects of the temperature 
record, I would emphasize a point which has been made by 
others: Temperature changes are only part of the total picture, 
and that the global mean temperature, I think of more as an 
indicator that something extraordinary is happening now. It is 
a little bit like the canary in a cage in a coal mine. It shows 
that something extraordinary is happening, but it has very 
little practical significance locally. And other changes such 
as rainfall and droughts, and fires such as in your own state, 
Senator, are probably of much more practical significance.
    Now in my written testimony, I summarize firstly, the 
surface temperature record; second, the radiosonde balloon-
borne temperature record which measures the temperatures above 
the surface of the earth; and third, the satellite record. And 
for each of these, I discuss the nature of the measurements, 
their coverage in space and time, their biases, their 
advantages and disadvantages, and they all have some, and a 
brief overall assessment of them. And I then deal with the 
issues of reconciling them, and I do not have time to go 
through all of those things here.
    What I will say is that all three records have been 
improved and developed in recent years, in particular several 
corrections have been made to the satellite record, for 
example, through the effects of the systematic orbital decay of 
each satellite--and this has improved the level of agreement 
among the records.
    Now using the radiosonde record, we can estimate the 
temperatures of the layer seen by the satellite. And this shows 
quite good agreement during the overlap period after 1979. And 
therefore, we can use the radiosonde record to extend that 
record back in time to about 1964 quite reliably.
    And when we do that, although we find that the temperature 
trends in the satellite record from 1979 to 1999 are quite 
small, the longer term trends are somewhat more in agreement 
with what we see at the surface.
    I would emphasize that the trends in the satellite record, 
after 1979, are less than those at the surface, primarily 
because they are measuring different things. A reasonable 
interpretation, I think, of the overall record is that global 
warming increases----
    The Chairman. What different things are they measuring?
    Dr. Trenberth. The satellite record is measuring the layer 
in the lowest five miles or so of the atmosphere, and it is 
influenced by a number of things that have much less influence 
at the surface. I was just coming to that point, in fact.
    The Chairman. I am sorry.
    Dr. Trenberth. I think a reasonable interpretation of the 
overall record is that the global warming from increased 
greenhouse gases is producing the rising temperatures that we 
are seeing at the surface, and now those rises are above and 
beyond those arising from natural variability.
    The main reasons the tropospheric temperatures are not 
keeping pace are because of stratospheric ozone depletion which 
has a much greater effect on what is happening, especially in 
the lower stratosphere and the upper part of the troposphere 
than it does on the surface. And also, changes in cloud cover, 
which have an effect on maximum versus minimum temperatures. We 
know that minimum temperatures are rising much faster than 
maximum temperatures, for instance. So changes in cloud 
coverage which may or may not be associated with other 
pollution in the atmosphere (effects other than climate 
change), may also be due to climate change itself. These are 
probably the two biggest effects that are causing the 
disparity.
    Therefore, what we do see is that the larger surface 
temperature increases are occurring over land and at night 
time, somewhat less during the day, and somewhat less over the 
oceans.
    The panel concluded that the records are probably 
reasonably consistent with each other once all of the forcing 
factors are taken into account. Now this goes beyond the models 
themselves, as it also is the forcing factors such as the 
depletion of the ozone layer and its vertical profile which are 
not known very well. And that is one of the uncertainties that 
exists.
    Once all of those factors are taken into account, we 
believe the records are consistent with one another. In other 
words, the bigger increase at the surface than in the 
troposphere is real. And accordingly, the recent warming at the 
surface is undoubtedly real. It is substantially greater than 
the average rate during the 20th century, and it is in no way 
invalidated by the satellite record.
    In my closing remarks, I would like to make a comment about 
global warming in general. I think the term itself is often 
misused, and it really should refer to the increased heating 
that is occurring because of the changes in composition of the 
atmosphere.
    Some of that heat goes into raising temperature, but in 
actual fact, most of it goes into evaporating moisture at the 
surface of the earth. Most of the earth is covered by ocean, 70 
percent of the surface, and most of the heat is, in fact, going 
into evaporating moisture.
    Over land that is true also as long as there is moisture 
around, but when things dry out, as happens in a drought, then 
all of the heat tends to go into raising temperature, and that 
is when we get the greatest heat waves.
    In the United States, there has been a general increase in 
precipitation and this tends to mute any changes in temperature 
because more heat is going then into evaporating moisture. As 
an example of this, if it has been raining and the sun comes 
out, the first thing that happens is that all of the puddles 
dry up. The heat goes into evaporating the moisture, not 
raising temperature.
    So it is very important to consider changes in temperature 
along with changes in rainfall, and just focusing on 
temperature does not give you a complete picture or an adequate 
understanding of what exactly is going on.
    So I would emphasize that it is much more than changes in 
temperature. Changes in precipitation, changes in moisture can 
act as a swamp cooler to air condition the planet, and in fact, 
do so. And we should also be concerned about changes in storms 
and changes in severe weather events.
    Thank you for the opportunity to testify.
    The Chairman. Thank you very much.
    [The prepared statement of Dr. Trenberth follows:]

    Prepared Statement of Dr. Kevin E. Trenberth, Director, Climate 
       Analysis Section, National Center for Atmospheric Research

                    CLIMATE CHANGE AND TEMPERATURES

Introduction
    My name is Kevin Trenberth. I am the Head of the Climate Analysis 
Section at NCAR, the National Center for Atmospheric Research. I am 
especially interested in global-scale climate dynamics; the 
observations, processes and modeling of climate changes from 
interannual to centennial time scales. I have served on many national 
and international committees including National Research Council/
National Academy of Science committees, panels and/or boards. I 
recently served on the National Research Council Panel on ``Reconciling 
observations of global temperature change,'' whose report was published 
in January 2000. I co-chaired the international CLIVAR Scientific 
Steering Group of the World Climate Research Programme (WCRP) from 1996 
to 1999 and I remain a member of that group as well as the Joint 
Scientific Committee that oversees the WCRP as a whole. CLIVAR is short 
for Climate Variability and Predictability and it deals with 
variability from El Nino to global warming. I have been involved in the 
global warming debate and I am extensively involved in the 
Intergovernmental Panel on Climate Change (IPCC) scientific assessment 
activity as a lead author of individual chapters, the Technical Summary 
and Policy Makers Summary of Working Group I.
    During the past 20 years, global mean surface temperatures have 
been rising at a rate as large as any that has been observed within the 
historical record. Such rapid warming at the Earth's surface is in 
contrast to the trend in the global-mean temperature of the lowest 8 
kilometers of the atmosphere (within that portion of the atmosphere 
referred to as the troposphere) as inferred from measurements of 
radiation emitted by oxygen molecules (a proxy for tropospheric 
temperature) sampled by the microwave sounding unit (MSU) carried 
aboard the NOAA polar-orbiting satellites; see Fig. 1 for the vertical 
structure of the atmosphere. I will summarize here the state of 
knowledge with regard to observed climate change, and especially the 
issues of the changes in temperatures as seen by the synthesis of 
observations taken at the Earth's surface versus those measured by 
satellite.

Fig. 1. The typical structure of temperature with height is shown. The 
lower atmosphere is the troposphere and the lowest 8 km or so of that 
is the region measured by the MSU-LT. The stratosphere contains the 
ozone layer and is separated from the troposphere by the tropopause 
which varies in height from about 10 km in the extratropics to 16 km in 
the tropics.




Observed climate change
    It is important to appreciate that temperature changes are only a 
part of the total picture. Global warming refers to the increased 
heating of the Earth arising from well documented increases in 
greenhouse gases such as Carbon Dioxide. At the surface, some of that 
heat goes into raising temperatures, but most of it goes into 
evaporating moisture. This is especially true as long as the surface is 
wet, as it always is over the 70% of the globe covered by oceans. After 
rainfalls, in bright sunshine, it is only following the drying up of 
surface puddles that temperatures are apt to rise. Accordingly, the 
strongest heat waves occur in association with droughts because then 
there is no surface moisture to act as a ``swamp cooler,'' and droughts 
are apt to become more intense with global warming. Meanwhile the 
increases in atmospheric moisture fuel more vigorous storms. Changes in 
extremes of climate will be much greater than changes in the mean. It 
also means that temperature increases are likely to be muted in places 
where precipitation has increased, as is generally the case for most of 
the United States. Changes in cloud cover, storm tracks, winds, and so 
forth further complicate the picture. The very nature of the 
atmospheric circulation, in which large-scale waves occur, also 
guarantees that some regions will warm more than others and some 
regions may cool even as the planet as a whole warms. These comments 
highlight the need to examine several factors, including precipitation, 
when developing an understanding of temperature changes.

Surface temperatures
    The surface temperature record is made up mostly from measurements 
by thermometers that track surface air temperature over land and ocean, 
as well as sea surface temperatures (SSTs) over the oceans. In recent 
years satellite infrared measurements have helped determine patterns of 
SSTs. The coverage increases over time after about 1850; it was quite 
poor in the 1800s and is best after the 1950s. It is only truly global 
after 1982 with the help of satellite measurements. It is generally 
poor over the southern oceans and there were almost no data over 
Antarctica prior to the IGY (1957). Changing biases confound the 
climate record. These arise from changes in observing practices 
(thermometer types, their exposure, the time of measurement etc.), and 
changes in land use practices. The urban heat island is the best known 
latter effect and arises because of the concrete jungle in cities which 
retains heat at night and causes rapid runoff of rain.
    The advantages of the surface record are its length, well over 100 
years, the many independent measurements, several independent analyses, 
and its robustness to the many cross checks, such as Northern versus 
Southern Hemisphere, urban versus rural, and land-based versus marine 
measurements. The disadvantages are the mostly less than global 
coverage, and coverage changes with time. An overall assessment is that 
the trends are robust, but may be slightly over-estimated owing to 
under-representation of the southern oceans and Antarctica.

Fig. 2. The average annual mean global temperature expressed as the 
departure from the 1961-90 average of 14C, called anomalies. From U.K. 
Met. Office and University of East Anglia.




    Surface temperatures (Fig. 2) have increased by 0.7+C (1.3+F) over 
the past century. The increase is not steady but occurs mainly from the 
1910s to 1940 and the 1970s to the present. 1998 is the warmest year on 
record and the 1990s are the warmest decade in both hemispheres, on 
land and on the ocean. Melting glaciers and rising sea level provide 
strong supporting evidence. However, over land nighttime temperatures 
are rising faster then daytime temperatures, by almost 0.1+C per decade 
since 1950, apparently largely because of increases in low cloud cover.
    The surface temperature record has been extended back in time by 
use of proxy indicators that are known to be sensitive to temperatures, 
such as from tree rings, corals, and ice cores. A recent synthesis of 
these provides further context for the recent trends and shows that the 
last decade is likely to have been the warmest in the past 1000 years.

Radiosonde temperatures
    Measurements of temperatures in the atmosphere above the surface 
became routine beginning in the mid-1940s through use of balloon-borne 
instrument packages (radiosondes) that transmit thermister-measured 
temperatures back to ground along with pressure and humidity. Their 
purpose has been mainly for aviation use and weather forecasting. The 
observations are at best twice daily and while spatial coverage 
improved in the IGY, it is marginal for large-scale estimates before 
about 1964. The biases are the many changes in instrumentation and 
observing methods, often with poor documentation of these changes. 
There are known biases in some brands, and a common problem has been 
improper shading from the sun and adequate ventilation. [Recall the 
temperature is that of the air, which must therefore be circulated past 
the sensor, and the sensor must be protected from direct solar 
radiation.] The advantages are the very high vertical resolution of the 
measurements, the use of new independent instruments for each sounding 
and the diversity of instruments. Also, there have been a few 
independent analyses. The disadvantages are the diversity of 
instruments that are inadequately calibrated for climate purposes, 
their often unknown changes with time, and the spotty non-global 
coverage. An assessment suggests that the tropospheric record is 
reasonably well known after 1964 in the Northern Hemisphere 
extratropics, but that coverage is inadequate elsewhere.

Satellite temperature measurements
    The satellite record is made up of MSU measurements of microwave 
radiation emitted by the atmosphere which are proportional to 
temperature. The coverage began in December 1978 twice or four times a 
day from one or two satellites, and is global. The emissions represent 
a very broad layer in the vertical, and so a retrieval is used to 
obtain the temperature closer to the surface. This is the commonly used 
satellite record but it still represents the lowest 8 km or so of the 
atmosphere, so it is physically a very different quantity than the 
surface temperature.
    The observation times vary with satellite and orbit drift. Biases 
arise from the use of 9 different satellites and instruments, orbital 
decay affects the retrieval, east-west drift of the satellite affects 
the time of day of observation, and there are instrument calibration 
and solar heating of the platform effects. Another significant factor 
is that the retrieval amplifies the noise by a factor of 3 to 5. Other 
disadvantages are some contaminating effects from the surface, 
especially over land, contamination by precipitation-sized ice, the 
difficulty of obtaining continuity across satellites, the shortness of 
the record, and one group has processed the data. The advantages are 
the global fairly uniform coverage, the long-term stability of 
microwave radiation emissions from oxygen, the biases may be well 
determined if there is adequate satellite overlap, and there are many 
observations which can be used to reduce random noise. The assessment 
is that this record is excellent for spatial coverage and determining 
interannual variations but suspect for trends.

Reconciling temperature records
    All three records have been improved and developed in recent years. 
In particular several corrections have been made to the satellite 
record (e.g., for orbital decay), and these have improved the 
agreement. Using the radiosonde record to estimate the temperatures of 
the layer seen by satellite shows very good agreement, so that the 
radiosonde record can be used to extend the satellite record back to 
about 1964 (Fig. 3). While tropospheric temperature trends from 1979 to 
1999 are small, longer term trends are more clearly positive and closer 
to those at the surface.
    It is evident that the trends in the satellite record are 
distinctly less than those in the surface record after 1979, and this 
arises primarily because they are measuring quite different things. The 
differences come from the vertical structure of the temperature changes 
with time, which are complicated by features, such as temperature 
inversions, in which the surface is disconnected from the atmosphere 
aloft. Low level inversions trap pollutants near the surface and are 
common over extratropical continents in winter, as well as throughout 
much of the tropics and subtropics. The physical forcing factors 
believed to be involved in causing differences in trends include (1) 
stratospheric ozone depletion which preferentially cools the satellite 
record; (2) episodic volcanic eruptions which cool the MSU more; (3) 
increases in greenhouse gases which warms MSU more; (4) changes in 
visible pollution (aerosols) which have complex regional effects that 
are not well known in vertical structure; (5) solar variations which 
are fairly small in this interval.
    Other physical factors include (1) El Nino and other natural 
variability which seems to produce a larger MSU response than at the 
surface by about 30 to 40%; (2) day-night differences which relate to 
maximum versus minimum temperature trends; and (3) land-ocean 
differences. The much greater increases in minimum temperature, related 
to increasing cloud cover, occur through a shallow layer and are not 
seen as much by satellite as maximum temperature changes which are 
distributed throughout the atmosphere by convection. The extent to 
which the changes in cloud cover arise from changes in atmospheric 
pollution or are a response to climate change is quite uncertain. Also 
ocean surface temperatures are muted, land temperature changes are much 
larger, and these differences are paramount at the surface but less 
evident in the troposphere where winds are much stronger.
    Not all of these effects have been included in models that deal 
with global warming or future climate change projections, but more 
sophisticated climate model simulations are expected in which best 
estimates of all the forcings will be included. Further improvements 
are also likely in the observational records of all three types. 
However, it is believed that the records are reasonably physically 
consistent with each other once all the forcing factors are taken into 
account. Accordingly, the recent warming at the surface is undoubtedly 
real, substantially greater than the average rate during the 20th 
century, and is in no way invalidated by the satellite record.
    A reasonable interpretation of the observational record is that 
global warming from increased greenhouse gases is resulting in global 
temperatures that are now above and beyond those arising from natural 
variability. The main reasons tropospheric temperatures are not keeping 
pace are because of stratospheric ozone depletion and increases in 
cloud cover. Consequently larger surface temperature increases occur 
over land and at nighttime. While observationally uncertain globally, 
although with strong evidence over the United States, increases in 
surface drying, atmospheric moisture amounts and precipitation rates 
are expected as part of an increase in the hydrological cycle. This 
increases risk of floods, droughts and associated fires; these are all 
extremes which are very costly to the environment and to society.

Fig. 3. Global mean seasonal temperature anomalies from the MSU-LT 
after 1979, the equivalent from radiosondes, and the surface from 1958 
on.



    The Chairman. Dr. Watson.

  STATEMENT OF DR. ROBERT WATSON, CHAIRMAN, INTERGOVERNMENTAL 
                    PANEL ON CLIMATE CHANGE

    Dr. Watson. Thank you, Senator. It is a pleasure to be here 
today to testify on the issue of climate change. I am 
testifying in my capacity as the Chairman of the 
Intergovernmental Panel on Climate Change.
    The IPCC conducts peer reviewed, comprehensive assessments 
of the climate system every 5 years, and periodic technical 
papers, special reports, and methodological studies as needed.
    These assessments provide the scientific and technical 
basis for the international negotiations. The IPCC assessments 
involve experts from all relevant disciplines, all stakeholder 
groups and from around the world.
    The second IPCC assessment report was prepared and peer-
reviewed by over 2,000 experts from over 100 countries.
    During the last year, the IPCC has published four special 
reports, one on aviation and the global atmosphere; one on 
technology transfer; one on emissions scenarios; and the one 
that I personally chaired and finished last week on land-use, 
land-use change and forestry.
    We are in the middle of preparing and peer-reviewing the 
third assessment report, which will be finished early next 
year.
    There is no doubt that human-induced climate change is one 
of the most important environmental issues facing society 
worldwide. Climate change is inevitable. It is only a question 
of how much, when and where.
    Human activities have significantly changed the composition 
of the Earth's atmosphere during the last 150 years. The 
atmospheric abundance of carbon dioxides increased about 30 
percent, largely due to the combustion of fossil fuels and 
changes in land-use, primarily--primarily deforestation in the 
tropics.
    The Earth's surface temperature warmed 0.4 to 0.8 degrees 
centigrade over the last 100 years. The last two decades are 
the warmest of the last century. And the 12 warmest years of 
the last century have all occurred since 1983. And this century 
is clearly the warmest century in the last 1,000 years.
    The spacial and temporal patterns of precipitation are 
changing. There have been observed increases in precipitation 
in the mid- and high-latitude and decreases in the sub-tropics.
    And there has been an increase in heavy precipitation 
events and a decrease in light precipitation events, at least 
in the United States.
    Many parts of the world have suffered major heat waves, 
floods and droughts during the last few years, leading to 
significant economic losses and loss of life.
    While individual events cannot be directly linked to human-
induced climate change, the frequency and magnitude of these 
types of events are expected to increase in a warmer world.
    Glaciers are retreating worldwide. Sea level has increased 
10 to 20 centimeters in the last 100 years. And Arctic ice is 
thinning. The observed changes in the Earth's climate cannot be 
explained by natural phenomena alone. And the scientific 
evidence, observations and models suggest a discernible human 
influence.
    The recent projections of future emissions of greenhouse 
gases and sulfur dioxide suggest that in the absence of global 
climate policies, the atmospheric concentrations of greenhouse 
gases will increase substantially over the next 100 years, 
while the emissions of sulfur dioxide will increase initially 
for a decade or two, and then decrease significantly because of 
the concern of acid deposition.
    Temperatures are projected to increase from about one to 
five degrees Centigrade, two to nine degrees Fahrenheit, 
between now and 2100. Why is this number that I am showing 
larger than the previous witnesses? And that is because the new 
emissions scenarios from the IPCC suggest very low sulfur 
dioxide emissions over the next 100 years and, hence, there is 
little or no offsetting/cooling effect due to aerosols on the 
greenhouse gas warming.
    So the projections for climate change are now larger than 
what they were a few years ago under the second assessment 
report. Precipitation is projected to increase globally. But 
many arid and semi-arid areas of the Earth are projected to 
become drier. The sea level is projected to increase between 10 
and 90 centimeters by 2100.
    So why do we, society, care? Water resources, managed and 
un-managed ecological systems, human health and human 
settlements are all predicted to be impacted by climate change.
    The arid and semi-arid areas of Africa, the Middle East and 
Southern Europe will become even more water-stressed than they 
are today.
    Agricultural production in Africa and Latin America could 
decrease ten to thirty percent. The incidence of vector-borne 
diseases, such as malaria and dengue, will increase 
significantly in tropical countries.
    Tens of millions of people will be displaced by rising sea 
levels in small island states and low-lying deltaic areas. And 
major changes are expected in the boundaries and the structure 
and functioning of critical ecological systems, especially in 
forests and coral reefs.
    The social costs of inaction are quite uncertain, but they 
are likely to be in the range of a few percent of world GDP 
annually in a doubled carbon dioxide world, with the cost being 
substantially greater in developing countries.
    However, the good news is that if we go beyond political 
ideology, there are numerous cost-effective ways to mitigate 
climate change using the extensive array of technologies and 
policy measures in both the energy supply and demand sectors.
    In addition, a significant potential to increase the uptake 
or decrease the emissions of carbon dioxide and other 
greenhouse gases through cost-effective changes in land use, 
land-use practices and forestry, slowing deforestation, and 
improve forest, crop land and range land management.
    Policy reform such as the elimination of fossil fuel 
subsidies and the internalization of the social costs of 
environmental damage will be essential to reduce the emissions 
of greenhouse gases.
    The flexibility mechanisms of the Kyoto Protocol, emissions 
trading, and project-based carbon-offset activities, offer the 
possibility of reducing greenhouse gas emissions at a lower 
cost than domestic actions alone, and can lead to the transfer 
of environmentally sound technologies to countries with 
economies in transition and developing countries.
    What we also note, however, is that the current efforts and 
processes will not be sufficient to facilitate the efficient 
transfer of environmentally sound technologies from developed 
to developing countries, but opportunities do exist to enhance 
the transfer of these technologies, but it will require all 
stakeholders to play their role, i.e., governments, industry, 
and NGO's.
    We should note that the atmospheric lifetime of carbon 
dioxide, which is the major anthropogenic greenhouse gas, is 
more than a century. This means that if policy formulation 
waits until all scientific uncertainties are resolved and 
carbon dioxide and other greenhouse gases are responsible for 
changing the earth's climate as projected by all climate 
models, the time to reverse human induced changes in climate 
and the resulting environmental damages will not be years or 
decades, but centuries to millennia.
    I note that enhanced R&D, research and development, policy 
reform and promoting market mechanisms will be essential to 
address the climate change issue, both domestically and 
globally.
    Last, while scientific uncertainties clearly exist, 
governments from around the world have recognized that we know 
enough to take the first steps to mitigate climate change.
    And, let me leave you with one simple observation. Many of 
the global warming skeptics today are the same skeptics who 
questioned whether human activities were destroying the earth's 
fragile ozone layer and increasing the level of damaging 
ultraviolet radiation reaching the Earth's surface. These 
skeptics argued against national and global action to protect 
the ozone layer.
    We now know that human activities were destroying the ozone 
layer and thankfully governments from around the world, working 
with industry, ignored the skeptics and cost-effective 
solutions were developed, thus protecting all life on Earth 
from the damaging--damaging ultraviolet radiation.
    Thank you.
    The Chairman. Thank you, Dr. Watson.
    [The prepared statement of Dr. Watson follows:]

          Prepared Statement of Dr. Robert Watson, Chairman, 
               Intergovernmental Panel on Climate Change

    It is a pleasure to appear before you today to discuss an issue of 
critical importance to this and future generations: global climate 
change. My name is Robert T. Watson and I am testifying in my capacity 
as the chairman of the Intergovernmental Panel on Climate Change 
(IPCC).
    I would like to first describe the work of the IPCC (Part I) and 
then briefly review the current state of knowledge concerning the 
climate system (Part II).

         PART I: The Intergovernmental Panel on Climate Change

    The IPCC is an intergovernmental panel established by the United 
Nations in 1988 under the auspices of the World Meteorological 
Organization (WMO) and the United Nations Environment Programme (UNEP) 
to assess the current state of scientific, technical and economic 
knowledge regarding climate change. While the IPCC is an independent 
scientific panel, it rides itself on being responsive to addressing the 
needs of the UNFCCC and the Kyoto Protocol. Indeed, the current IPCC 
work program has been designed to provide the scientific, technical and 
economic information that is needed to implement the Convention and the 
Kyoto Protocol.
    The IPCC provides comprehensive assessments of the state of 
knowledge every five years, complemented by technical papers, special 
reports, and methodological work.
    The IPCC is in the midst of the preparation and peer-review of the 
Third Assessment Report, including the Synthesis Report, and has, 
during the last year, completed work on four special reports: (i) 
Aviation and the Global Atmosphere; (ii) Methodological and 
Technological Aspects of Technology Transfer: Opportunities for 
Technology Cooperation; (iii) Emissions Scenarios of Greenhouse Gases 
and Aerosol Precursors; and (iv) Land-Use, Land-Use Change and 
Forestry. The Summaries for Policymakers for each of these special 
reports is included in a series of Annexes * to this testimony. The 
three Working Group Reports of the TAR will be completed between 
January 2001 and March 2001, while the Synthesis Report will be 
completed in September/October 2001.
---------------------------------------------------------------------------
    * Annex 1--Summary for Policymakers: Aviation and the Global 
Atmosphere; Annex 2--Summary for Policymakers: Special Report on 
Methodological and Technological Issues in Technology Transfer; Annex 
3--Summary for Policymakers: Special Report on Emissions Scenarios; and 
Annex 4--Summary for Policymakers: Special Report on Land Use, Land-Use 
Change and Forestry, have been retained in the Committee files and are 
available on the web at http://www.ipcc.ch/pub/reports.htm.
---------------------------------------------------------------------------
    The Third Assessment Report will be a comprehensive assessment and 
build upon the findings of the Second assessment Report, which was 
completed in 1995. The Third assessment Report will: (i) emphasize 
cross-sectoral issues, adaptation and the regional dimensions of 
climate change; (ii) place the issue of climate change more centrally 
within the concept of sustainable development; and (iii) identify the 
synergies and trade-offs between local, regional and global 
environmental issues, in particular the inter-linkages between climate 
change, biodiversity, water resources and land degradation.
    All IPCC assessments are prepared and peer-reviewed, according to 
an approved set of principles and procedures, by experts from all 
relevant disciplines (natural scientists, social Scientists, and 
technologists), from all stakeholder groups (universities, government 
agencies, industry, business and environmental organizations) and from 
all around the world. Over two thousand experts, from over one hundred 
countries, participated in the preparation and peer-review of the 
Second Assessment Report. The reports emphasize what is known and what 
is uncertain. Areas of controversy are discussed and alternate 
viewpoints presented.
    The IPCC is currently structured into three Working Groups:

Working Group I
    The climate system: Sources and sinks of greenhouse gases and 
aerosols; observed changes in atmospheric composition, climate 
variables, cryosphere, and sea level; climate variability; physical and 
biogeochemical processes; evaluation of approaches for developing 
regional climate information; evaluation of models; model simulations 
of past and current regional and global climate; model simulations of 
future regional and global changes in atmospheric composition, 
radiative forcing, climate, cryosphere, and sea level, using agreed and 
proposed policies to mitigate climate change, different stabilization 
levels of greenhouse gases, and the emissions scenarios from the 
ongoing special report; and detection and attribution of climate 
change.

Working Group II
    Regional, sectoral and cross-sectoral impacts of and adaptation to, 
climate change, including the social dimensions (e.g., equity) and 
economic costs and benefits: Primers on how terrestrial and marine 
ecological and hydrological processes respond to changes in climatic 
conditions and atmospheric composition, e.g., increased carbon dioxide 
concentrations; primer on human health mechanisms; methodological 
approaches to the impact of, and adaptation to, climate change, for 
ecological systems, human health and socio-economic sectors; issues in 
integrating ecological and economic assessments of impacts and 
adaptation potential; evaluation of the sensitivity of ecological 
systems, human health and socio-economic sectors to climatic variables; 
regional evaluations of the sectoral and cross-sectoral impacts of 
climate change, including the social dimensions and economic costs and 
benefits; regional sectoral and cross-sectoral adaptation strategies 
(technological, institutional, and policy aspects) in the context of 
meeting human needs; and global sectoral assessments (e.g., movements 
in ecosystem boundaries, and changes in agricultural and fisheries 
productivity at the global level). Impact studies will: (i) use a range 
of transient GCM projections of climate change, be placed in the 
context of other changes in socio-economic and environmental 
conditions, and assess to what degree climate change affects the 
ability to meet human needs (adequate food, clean water, a healthy 
environment, safe shelter, etc.); and (ii) be performed for a range of 
climates associated with different greenhouse gas stabilization levels.

Working Group III
    Mitigation of climate change, including the social aspects and 
economic costs and benefits, and methodological aspects of cross-
cutting issues: Methodological issues associated with mitigation, 
equity, discount rates, decision-making framework, uncertainties, and 
integrated assessment modeling; evaluation of the technical, economic 
and market potential of energy supply and demand and land-use 
technologies, regional assessments of the mitigation potential of 
different technologies, including the social dimensions and economic 
costs and benefits, with and integrated energy-related and land-related 
mitigation options, including ``distributional'' costs for different 
stabilization levels and different emissions profiles; and evaluation 
of policy options (including carbon and energy taxes, subsidy 
elimination, internalization of local and regional environmental 
externalities, emissions trading and joint implementation).

    In addition to the three Working Group Reports, the Third 
Assessment Report will contain a Synthesis Report, which is based on 
previously approved IPCC reports and will address the following ten key 
policy-relevant questions (abbreviated):

   What can scientific, technical and socio-economic analyses 
        contribute to the determination of what constitutes dangerous 
        anthropogenic interference with the climate system as referred 
        to in Article 2 of the Framework Convention on Climate Change?

   What is the evidence for, causes of, and consequences of 
        changes in the Earth's climate since the pre-industrial era?

   What is known about the influence of the increasing 
        atmospheric concentrations of greenhouse gases and aerosols, 
        and the projected human-induced change in climate regionally 
        and globally?

   What is known about the inertia and time-scales associated 
        with the changes in the climate system, ecological systems, and 
        socio-economic sectors and their interactions?

   What is known about the regional and global climatic, 
        environmental, and socio-economic consequences in the next 25, 
        50 and 100 years associated with a range of greenhouse gas 
        emissions arising from scenarios used in the TAR (projections 
        which involve no climate policy interventions)?

   How does the extent and timing of the introduction of a 
        range of emissions reduction actions determine and affect the 
        rate, magnitude, and impacts of climate change, and affect the 
        global and regional economy, taking into account the historical 
        and current emissions?

   What is known from sensitivity studies about the regional 
        and global climatic, environmental and socio-economic 
        consequences of stabilizing the atmospheric concentrations of 
        greenhouse gases (in carbon dioxide equivalents), at a range of 
        levels from today's to double that or more, taking into account 
        to the extent possible the effects of aerosols. For each 
        stabilization scenario, including different pathways to 
        stabilization, evaluate the range of costs and benefits, 
        relative to the range of scenarios considered in question 5.

   What is known about the interactions between projected 
        human-induced changes in climate and other environmental 
        issues, e.g., urban air pollution, regional acid deposition, 
        loss of biological diversity, stratospheric ozone depletion, 
        and desertification and land degradation? What is known about 
        the environmental, social and economic costs and benefits and 
        implications of these interactions for integrating climate 
        response strategies in an equitable manner into broad 
        sustainable development strategies at the local, regional and 
        global levels?

   What is known about the potential for, and costs and 
        benefits of, and timeframe for reducing greenhouse gas 
        emissions?

   What are the most robust findings and key uncertainties 
        regarding attribution of climate change and regarding model 
        projections of: (i) future emissions of greenhouse gases and 
        aerosols; (ii) future concentrations of greenhouse gases and 
        aerosols; (iii) future changes in regional and global climate; 
        (iv) regional and global impacts of climate change; and (v) 
        costs and benefits of mitigation and adaptation options?

    I would like to briefly summarize the current state of scientific 
knowledge concerning climate change.

                  PART II: Present State of Knowledge

Overview
    The overwhelming majority of scientific experts recognize that 
scientific uncertainties exist, but still believe that human-induced 
climate change is inevitable. Indeed, during the last few years, many 
parts of the world have suffered major heat-waves, floods, droughts and 
extreme weather events leading to significant economic losses and loss 
of life. While individual events cannot be directly linked to human-
induced climate change, the frequency and magnitude of these types of 
events are expected to increase in a warmer world.
    The question is not whether climate will change in response to 
human activities, but rather where (regional patterns), when (the rate 
of change) and by how much (magnitude). It is also clear that climate 
change will adversely effect human health (particularly vector-borne 
diseases), ecological systems (particularly forests and coral reefs), 
and socio-economic sectors, including agriculture, forestry, fisheries, 
water resources, and human settlements, with developing countries being 
the most vulnerable. These are the fundamental conclusions of a careful 
and objective analysis of all relevant scientific, technical and 
economic information by thousands of experts from the appropriate 
fields of science from academia, governments, industry and 
environmental organizations from around the world under the auspices of 
the United Nations International Panel on Climate Change. The good news 
is, however, that the majority of energy experts believe that 
significant reductions in greenhouse gas emissions are technically 
feasible due to an extensive array of technologies and policy measures 
in the energy supply and energy demand sectors at little or no cost to 
society. In addition, changes in land-use practices can also reduce net 
carbon emissions cost-effectively.
    However, decision-makers should realize that the atmospheric 
residence/adjustment time of carbon dioxide, the major anthropogenic 
greenhouse gas, is more than a century, which means that if policy 
formulation waits until all scientific uncertainties are resolved, and 
carbon dioxide and other greenhouse gases are responsible for changing 
the Earth's climate as projected by all climate models, the time to 
reverse the human-induced changes in climate and the resulting 
environmental damages, would not be years or decades, but centuries to 
millennia, even if all emissions of greenhouse gases were terminated, 
which is clearly not practical.
    This testimony briefly describes the current state of understanding 
of the Earth's climate system and the influence of human activities; 
the vulnerability of human health, ecological systems, and socio-
economic sectors to climate change; and approaches to reduce emissions 
and enhance sinks.

The Earth's Climate System: The Influence of Human Activities
    The Earth's climate has been relatively stable (global temperature 
changes of less than 1+C over a century) during the present 
interglacial (i.e., the past 10,000 years). During this time modem 
society has evolved, and, in many cases, successfully adapted to the 
prevailing local climate and its natural variability. However, the 
Earth's climate is now changing. The Earth's surface temperature this 
century is as warm or warmer than any other century during the last 
thousand years; the Earth's surface temperature has increased by 
between 0.4 and 0.8 degree centigrade over the last century, with land 
areas warming more than the oceans; and the last few decades have been 
the hottest this century. Indeed, the three warmest years during the 
last one hundred years all occurred in the 1990s and the twelve warmest 
years during the last one hundred years all occurred since 1983. In 
addition, there is evidence of changes in sea level, that glaciers are 
retreating world-wide, that Arctic sea ice is thinning, precipitation 
patterns are changing, and that the incidence of extreme weather events 
is increasing in some parts of the world. Not only is there evidence of 
a change in climate at the global level, but there is observational 
evidence that the climate of the U.S. is changing in a manner 
consistent with that predicted by climate models (I have specifically 
mentioned the U.S. because it has a large geographic area and a long 
accurate set of weather observations against which model simulations 
can be evaluated): increased temperatures (day and night), more intense 
rainfall events (defined as two inches within a 24 hour period), 
increased precipitation in winter, and less day-day variability in 
temperature.
    The atmospheric concentrations of greenhouse gases have increased 
because of human activities, primarily due to the combustion of fossil 
fuels (coal, oil and gas), deforestation and agricultural practices, 
since the beginning of the pre-industrial era around 1750: carbon 
dioxide by nearly 30%, methane by more than a factor of two, and 
nitrous oxide by about 15%. Their concentrations are higher now than at 
any time during the last 160,000 years, the period for which there are 
reliable ice-core data, and probably significantly longer. In addition, 
the atmospheric concentrations of sulfate aerosols have also increased. 
Greenhouse gases tend to warm the atmosphere and, in some regions, 
primarily in the Northern hemisphere, aerosols tend to cool the 
atmosphere.
    Theoretical models that take into account the observed increases in 
the atmospheric concentrations of greenhouse gases and sulfate aerosols 
simulate the observed changes in surface temperature and the vertical 
distribution of temperature quite well. This, and other information, 
suggests that human activities are implicated in the observed changes 
in the Earth's climate. In fact, the observed changes in climate cannot 
be explained by natural phenomena alone (e.g., changes in solar output 
and volcanic emissions).
    Future emissions of greenhouse gases and the sulfate aerosol 
precursor, sulfur dioxide, are sensitive to the evolution of governance 
structures world-wide, whether the current inequitable distribution of 
wealth continues or decreases, changes in population and gross domestic 
product, the rate of diffusion of new technologies into the market 
place, production and consumption patterns, land-use practices, energy 
intensity, and the price and availability of energy. Most projections 
suggest that greenhouse gas concentrations will increase significantly 
during the next century in the absence of policies specifically 
designed to address the issue of climate change. Indeed, the recent 
IPCC special report on emissions scenarios reported, for example, 
carbon dioxide emissions from the combustion of fossil fuels are 
projected to range from bout 5 to 35 GtC per year in the year 2100: 
compared to current emissions of about 6.3 GtC per year. Such a range 
of emissions would mean that the atmospheric concentration of carbon 
dioxide would increase from today's level of 360 ppmv (parts per 
million by volume) to between 500 and 900 ppmmv by 2100. It should be 
noted that two major oil companies, Shell and British Petroleum, have 
suggested that the mix of energy sources could change radically, with 
renewable energy sources (solar, wind and modern biomass) accounting 
for as much as half of all energy produced by the middle of the next 
century. Such a future would be consistent with the lower projections 
of greenhouse gas emissions and would clearly eliminate the highest 
projections of greenhouse gases from being realized, but this vision of 
a future world will not occur without policy reform and significantly 
enhanced public and private sector energy R&D programs.
    While the recent IPCC special report on emissions scenarios (SRES 
00) reported similar projected emissions for carbon dioxide to the 1992 
projections, it differed in one important aspect from the 1992 
projections, in-so-far-as the projected emissions of sulfur dioxide are 
much lower. This has important implications for future projections of 
temperature changes, because sulfur dioxide emissions lead to the 
formation of sulfate aerosols in the atmosphere, which as stated 
earlier can partially offset the warming effect of the greenhouse 
gases.
    Based on the range of climate sensitivities (an increase in the 
equilibrium global mean surface temperature of 1.5-4.5+C for a doubling 
of atmospheric carbon dioxide concentrations) and plausible ranges of 
greenhouse gas and sulfur dioxide emissions (SRES 00), climate models 
project that the global mean surface temperature could increase by 1 to 
5+C by 2100. These projected global-average temperature changes would 
be greater than recent natural fluctuations and would also occur at a 
rate significantly faster than observed changes over the last 10,000 
years. These long-term, large-scale, human-induced changes are likely 
to interact with natural climate variability on time-scales of days to 
decades (e.g., the El Nino-Southern Oscillation (ENSO) phenomena). 
Temperature changes are expected to differ by region with high 
latitudes projected to warm more than the global average. However, the 
reliability of regional scale predictions is still low. Associated with 
these estimated changes in temperature, sea level is projected to 
increase by 10-90 cm by 2100, caused primarily by thermal expansion of 
the oceans and the melting of glaciers. However, it should be noted 
that even when the atmospheric concentrations of greenhouse gases are 
stabilized, temperatures will continue to increase for several decades 
because of the thermal inertia of the climate system (temperature by 
another 30-50%), and sea level for an even longer period of time 
(centuries to millennia).
    Model calculations show that evaporation will be enhanced as the 
climate warms, and that there will be an increase in global mean 
precipitation and an increase in the frequency of intense rainfall. 
However, not all land-regions will experience an increase in 
precipitation, and even those land regions with increased precipitation 
may experience decreases in soil moisture, because of enhanced 
evaporation. Seasonal shifts in precipitation are also projected. In 
general, precipitation is projected to increase at high latitudes in 
winter, and soil moisture is projected to decrease in some mid-latitude 
continental regions during summer. The arid and semi-arid areas in 
Southern and Northern Africa, Southern Europe and the Middle East are 
expected to become drier.
    While the incidence of extreme temperature events, floods, 
droughts, soil moisture deficits, fires and pest outbreaks is expected 
to increase in some regions, it is unclear whether there will be 
changes in the frequency and intensity of extreme weather events such 
as tropical storms, cyclones, and tornadoes.

The Vulnerability of Human Health, Ecological Systems, and Socio-
        economic Sectors to Climate Change
    The IPCC has assessed the potential consequences of changes in 
climate for human health, ecological systems and socio-economic sectors 
for ten continental- or subcontinental-scale regions: Africa, 
Australasia, Europe, Latin America, Middle East and Arid Asia, North 
America, Polar regions, Small Island States, Temperate Asia, and 
Tropical Asia. Because of uncertainties associated with regional 
projections of climate change, the IPCC assessed the vulnerability of 
these natural and social systems to changes in climate, rather than 
attempting to provide quantitative predictions of the impacts of 
climate change at the regional level. Vulnerability is defined as the 
extent to which a natural or social system is susceptible to sustaining 
damage from climate change, and is a function of the sensitivity of a 
system to changes in climate and the ability to adapt the system to 
changes in climate. Hence, a highly vulnerable system is one that is 
highly sensitive to modest changes in climate and one for which the 
ability to adapt is severely constrained.
    Most impact studies have assessed how systems would respond to a 
climate change resulting from an arbitrary doubling of atmospheric 
carbon dioxide concentrations. Very few have considered the dynamic 
responses to steadily increasing greenhouse gas concentrations; fewer 
yet have been able to examine the consequences of increases beyond a 
doubling of greenhouse gas concentrations or to assess the implications 
of multiple stress factors.
    The IPCC concluded that human health, terrestrial and aquatic 
ecological systems, and socioeconomic systems (e.g., agriculture, 
forestry, fisheries, water resources, and human settlements), which are 
all vital to human development and well-being, are all vulnerable to 
changes in climate, including the magnitude and rate of climate change, 
as well as to changes in climate variability. Whereas many regions are 
likely to experience the adverse effects of climate change--some of 
which are potentially irreversible--some effects of climate change are 
likely to be beneficial. Hence, different segments of society can 
expect to confront a variety of changes and the need to adapt to them.
    There are a number of general conclusions that can be easily drawn: 
(i) human-induced climate change is an important new stress, 
particularly on ecological and socio-economic systems that are already 
affected by pollution, increasing resource demands, and non-sustainable 
management practices; (ii) the most vulnerable systems are those with 
the greatest sensitivity to climate change and the least adaptability; 
(iii) most systems are sensitive to both the magnitude and rate of 
climate change; (iv) many of the impacts are difficult to quantify 
because existing studies are limited in scope; and (v) successful 
adaptation depends upon technological advances, institutional 
arrangements, availability of financing and information exchange, and 
that vulnerability increases as adaptation capacity decreases. 
Therefore, developing countries are more vulnerable to climate change 
than developed countries.
    The range of adaptation options for managed systems such as 
agriculture and water supply is generally increasing because of 
technological advances. However, some regions of the world, i.e., 
developing countries, have limited access to these technologies and 
appropriate information. The efficacy and cost-effectiveness of 
adaptation strategies will depend upon cultural, educational, 
managerial, institutional, legal and regulatory practices that are both 
domestic and international in scope. Incorporation of climate change 
concerns into resource-use and development decisions and plans for 
regularly scheduled investments in infrastructure will facilitate 
adaptation.
    Let me now briefly discuss the implications of climate change for a 
representative number of systems: natural ecosystems (forests and coral 
reefs), food security, water resources, sea level rise, and human 
health.

Natural Ecosystems--Forests
    The composition and geographic distribution of many ecosystems will 
shift as individual species respond to changes in climate, and there 
will likely be reductions in biological diversity (particularly species 
diversity) and in the goods and services ecosystems provide society, 
e.g., sources of food, fiber, medicines, recreation and tourism, and 
ecological services such as controlling nutrient cycling, Waste 
quality, water run-off, and soil erosion. Models project that as a 
consequence of possible changes in temperature and water availability 
under doubled carbon dioxide equilibrium conditions, a substantial 
fraction (a global average of one-third, varying by region from one-
seventh in tropical forests to two-thirds in Boreal forests) of the 
existing forested area of the world will undergo major changes in broad 
vegetation types. Climate change is expected to occur at a rapid rate 
relative to the speed at which forest species grow, reproduce and re-
establish themselves. For mid-latitude regions a global average warming 
of 1-3.5+C over the next 100 years would be equivalent to a poleward 
shift of isotherms of approximately 150-550 km or an altitude shift of 
150-550 meters. This compares to past tree species migration rates that 
are believed to be on the order of 4-200 km per century. Therefore, 
species composition of impacted forests is likely to change, entire 
forest types may disappear, while new assemblages of species and hence 
new forest ecosystems may be established. Large amounts of carbon could 
be released into the atmosphere during times of high forest mortality 
prior to regrowth of a mature forest.

Natural Ecosystems--Coral Reefs
    Coral reefs, the most biologically diverse marine ecosystems, are 
important for fisheries, tourism, coastal protection, and erosion 
control. Coral reef systems, which are already being threatened by 
pollution, unsustainable tourism and fishing practices, are very 
vulnerable to changes in climate. While these systems may be able to 
adapt to the projected increases in sea level, sustained increases in 
water temperatures of 3-4+C above long-term average seasonal maxima 
over a 6-month period can cause significant coral mortality; short-term 
increases on the order of only 1-2+C can cause ``bleaching,'' leading 
to reef destruction. Indications are that the full restoration of coral 
communities could require several centuries.

Food Security
    Currently, 800 million people are malnourished; as the world's 
population increases and incomes in some countries rise, food 
consumption is expected to double over the next three to four decades. 
Studies show that on the whole, global agricultural production could be 
maintained relative to baseline production in the face of climate 
change under doubled carbon dioxide equilibrium conditions. However, 
crop yields and changes in productivity due to climate change will vary 
considerably across regions and among localities, thus changing the 
patterns of production. In general, productivity is projected to 
increase in middle to high latitudes, depending on crop type, growing 
season, changes in temperature regime, and seasonality of 
precipitation, whereas in the tropics and subtropics, where some crops 
are near their maximum temperature tolerance and where dryland, non-
irrigated agriculture dominates, yields are likely to decrease, 
especially in Africa and Latin America, where decreases in overall 
agricultural productivity of 30% are projected under doubled carbon 
dioxide conditions. Therefore, there may be increased risk of hunger in 
some locations in the tropics and subtropics where many of the world's 
poorest people live.

Water Resources
    Currently 1.3 billion people do not have access to adequate 
supplies of safe water, and 2 billion people do not have access to 
adequate sanitation. Today, some nineteen countries, primarily in the 
Middle East and Africa, are classified as water-scarce or water-
stressed. Even in the absence of climate change, this number is 
expected to double by 2025, in large part because of increases in 
demand from economic and population growth. Climate change will further 
exacerbate the frequency and magnitude of droughts in some places, in 
particular Northern and Southern Africa and the Middle East where 
droughts are already a recurrent feature. Developing countries are 
highly vulnerable to climate change because many are located in arid 
and semi-arid areas.

Sea Level Rise
    Sea-level rise can have negative impacts on tourism, freshwater 
supplies, fisheries, exposed infrastructure, agricultural and dry 
lands, and wetlands. It is currently estimated that about half of the 
world's population lives in coastal zones, although there is a large 
variation among countries. Changes in climate will affect coastal 
systems through sea-level rise and an increase in storm-surge hazards, 
and possible changes in the frequency and/or intensity of extreme 
events. Impacts may vary across regions, and societal costs will 
greatly depend upon the vulnerability of the coastal system and the 
economic situation of the country. Sea-level rise will increase the 
vulnerability of coastal populations to flooding. An average of about 
46 million people per year currently experience flooding due to storm 
surges; a 50 cm sea-level rise would increase this number to about 92 
million; a 1 meter sea-level rise would increase this number to 118 
million. The estimates will be substantially higher if one incorporates 
population growth projections. A number of studies have shown that 
small islands and deltaic areas are particularly vulnerable to a one-
meter sea-level rise. In the absence of mitigation actions (e.g., 
building sea walls), land losses are projected to range from 1.0% for 
Egypt, 6% for Netherlands, 17.5% for Bangladesh, to about 80% of the 
Marshall Islands, displacing tens of millions of people, and in the 
case of low-lying Small Island States, the possible loss of whole 
cultures. Many nations face lost capital value in excess of 10% of GDP. 
While annual adaptation/protection costs for most of these nations are 
relatively modest (about 0.1% GDP), average annual costs to many small 
island states are much higher, several percent of GDP, assuming 
adaptation is possible.

Human Health
    Human health is sensitive to changes in climate because of changes 
in food security, water supply and quality, and the distribution of 
ecological systems. These impacts would be mostly adverse, and in many 
cases would cause some loss of life. Direct health effects would 
include increases in heat-related mortality and illness resulting from 
an anticipated increase in heatwaves. Indirect effects would include 
extensions of the range and season for vector organisms, thus 
increasing the transmission of vector-borne infectious diseases (e.g., 
malaria, dengue, yellow fever and encephalitis). Projected changes in 
climate under doubled carbon dioxide equilibrium conditions could lead 
to potential increases in malaria incidence of the order of 50-80 
million additional cases annually, primarily in tropical, subtropical, 
and less well-protected temperate-zone populations. Some increases in 
non-vector-borne infectious diseases such as salmonellosis, cholera and 
other food- and water-related infections could also occur, particularly 
in tropical and subtropical regions, because of climatic impacts on 
water distribution and temperature, and on micro-organism 
proliferation.

Social Costs of Climate Change
    The range of estimates of economic damages caused by changes in 
climate are quite uncertain. Taking into account both market and non-
market costs, IPCC reported a reduction in world GDP of 1.5-2.0% for a 
doubled carbon dioxide environment. This value was obtained by summing 
widely varying estimates of damages by sector, including socio-economic 
sectors (e.g., agriculture, forestry, fisheries), ecological systems, 
and human health. Nordhaus, conducted an ``expert'' survey which 
resulted in a range from 0 to 21% for loss of world GDP, with a mean 
value of 3.6% and a median value of 1.9%.
    Losses in developing countries are estimated to be much higher than 
the world average, ranging from 5% to 9%. Alternate assumptions about 
the value of a statistical life could increase the estimate of economic 
damages in developing countries.
    IPCC reported values for the marginal damage of one extra ton of 
carbon emitted ranging from $5 to $125. A value of $5 to $12 per ton of 
carbon is obtained using a 5% social rate of time preference (discount 
rate). Lower discount rates increase this estimate, e.g. a 2% discount 
rate would increase this estimate by an order of magnitude.

Approaches to Reduce Emissions and Enhance Sinks
    Significant reductions in net greenhouse gas emissions are 
technically, and often economically, feasible and can be achieved by 
utilizing an extensive array of technologies and policy measures that 
accelerate technology diffusion in the energy supply (more efficient 
conversion of fossil fuels; switching from high to low carbon fossil 
fuels; decarbonization of flue gases and fuels, coupled with carbon 
dioxide storage; increasing the use of nuclear energy; and increased 
use of modem renewable sources of energy (e.g., plantation biomass, 
micro-hydro, and solar), energy demand (industry, transportation, and 
residential/commercial buildings) and agricultural/foresty sectors 
(altered management of agricultural soils and rangelands, restoration 
of degraded agricultural lands and rangelands, slowing deforestation, 
natural forest generation, establishment of tree plantations, promoting 
agroforestry, and improving the quality of the diet of ruminants). By 
the year 2100, the world's commercial energy system will be replaced at 
least twice offering opportunities to change the energy system without 
premature retirement of capital stock. However, full technical 
potential is rarely achieved because of a lack of information and 
cultural, institutional, legal and economic barriers.
    Policy instruments can be used to facilitate the penetration of 
lower carbon intensive technologies and modified consumption patterns. 
These policies include: energy pricing strategies (e.g., carbon taxes 
and reduced energy subsidies); reducing or removing other subsidies 
that increase greenhouse gas emissions (e.g., agricultural and 
transport subsidies); incentives such as provisions for accelerated 
depreciation and reduced costs for the consumer; tradable emissions 
permits (and joint implementation); voluntary programs and negotiated 
agreements with industry; utility demand-side management programs; 
regulatory programs including minimum energy efficiency standards; 
market pull and demonstration programs that stimulate the development 
and application of advanced technologies; and product labeling. The 
optimum mix of policies will vary from country to country; policies 
need to be tailored for local situations and developed through 
consultation with stakeholders.
    Estimates of the costs of mitigating climate change should take 
into account secondary benefits of switching from a fossil fuel based 
economy to a lower-carbon intensity energy system. Secondary benefits 
include lower levels of local and regional pollution, including 
particulates, ozone and acid rain.
    A key issue recognized by all Parties to the UNFCCC and the Kyoto 
Protocol is that of technology transfer. The recent IPCC special report 
on technology transfer examined the flows of knowledge, experience and 
equipment among governments, private sector entities, financial 
institutions, NGOs, and research and education institutions, and the 
different roles that each of these stakeholders can play in 
facilitating the transfer of technologies to address climate change in 
the context of sustainable development. The report concluded that the 
current efforts and established processes will not be sufficient to 
meet this challenge. It is clear that enhanced capacity is required in 
developing countries and that additional government actions can create 
the enabling environment for private sector technology transfers within 
and across national boundaries.

Summary
    Policymakers are faced with responding to the risks posed by 
anthropogenic emissions of greenhouse gases in the face of significant 
scientific uncertainties. They should consider these uncertainties in 
the context that climate-induced environmental changes cannot be 
reversed quickly, if at all, due to the long time scales (decades to 
millennia) associated with the climate system. Decisions taken during 
the next few years may limit the range of possible policy options in 
the future because high near-term emissions would require deeper 
reductions in the future to meet any given target concentration. 
Delaying action might reduce the overall costs of mitigation because of 
potential technological advances but could increase both the rate and 
the eventual magnitude of climate change, and hence the adaptation and 
damage costs.
    Policymakers will have to decide to what degree they want to take 
precautionary measures by mitigating greenhouse gas emissions and 
enhancing the resilience of vulnerable systems by means of adaptation. 
Uncertainty does not mean that a nation or the world community cannot 
position itself better to cope with the broad range of possible climate 
changes or protect against potentially costly future outcomes. Delaying 
such measures may leave a nation or the world poorly prepared to deal 
with adverse changes and may increase the possibility of irreversible 
or very costly consequences. Options for adapting to change or 
mitigating change that can be justified for other reasons today (e.g., 
abatement of air and water pollution) and make society more flexible or 
resilient to anticipated adverse effects of climate change appear 
particularly desirable.
    If, actions are not taken to reduce the projected increase in 
greenhouse gas emissions, the Earth's climate is projected to change at 
an unprecedented rate with adverse consequences for society, 
undermining the very foundation of sustainable development. Adaptive 
strategies to deal with this issue need to be developed, recognizing 
issues of equity and cost-effectiveness.
    While there is no debate that protection of the climate system will 
eventually need all countries to limit their greenhouse gas emissions, 
the Framework Convention on Climate Change recognizes the principle of 
differentiated responsibilities, and also recognizes that developed 
countries and countries with economies in transition should take the 
lead in limiting their greenhouse gas emissions given the historical 
and current emissions of greenhouse gases, and their financial, 
technical and institutional capabilities. Current and historical 
emissions of greenhouse gases arise mainly from developed countries and 
countries with economies in transition, i.e., emissions in developing 
countries are much lower, both in absolute and per capita terms. Even 
though it is well recognized that emissions from developing countries 
are increasing rapidly due to increases in population and economic 
growth, and are likely to surpass those from developed countries within 
a few decades (absolute terms, not per-capita), their contribution to 
global warming will not equal that of developed countries until nearly 
2100 because the climate system responds to the cumulative emissions of 
greenhouse gases not the annual emissions. It is also quite clear that 
increased energy services in developing countries are critical in order 
to alleviate poverty and underdevelopment, where 1.3 billion people 
live on less than $1 per day, 3 billion people live on less than $2 per 
day, and 2 billion people are without electricity. Hence the challenge 
is to assist developing countries expand their production and 
consumption of energy in the most efficient and environmentally benign 
manner. Financial instruments such as the Global Environment Facility 
and promoting market mechanisms such as emissions trading and joint 
implementation can assist in this endeavor. In addition, an increased 
commitment to energy R&D for energy efficient technologies and low-
carbon technologies would not only allow the U.S. to meet it's energy 
needs in a more climate friendly manner, but it would also provide a 
large market in developing countries for U.S. exports.
    Mr. Chairman, members of the Committee, I appreciate the 
opportunity you have provided me to be able to discuss these important 
issues with you today. Thank-you.

    The Chairman. Dr. Christy, can you further discuss the 
reasons why we are not experiencing the rate of temperature 
increase in the upper altitudes that computer models may be 
predicting?
    Dr. Christy. OK. You are asking for the ``why'' of this 
issue, and I do not have an answer for why, here. I would like 
to say that the disparity is greatest in the tropical regions, 
and this lower tropospheric layer of the atmosphere is far 
below what ozone depletion would impact. In fact, I have 
checked specifically to make sure that--that the temperature 
rise at 100 millebars--what would that be? About--about ten 
miles or so.
    The temperature even in the upper troposphere at 100 
millebars is actually slightly warmer than it is in this bulk 
of the atmosphere below that we are measuring in terms of 
trends. So I do not have an answer for ``why.'' I am skeptical 
about ozone depletion as part of the cooling effect on that 
particular layer (i.e., the lower troposphere.
    The Chairman. Well, do you disagree with Dr. Mahlman's 
assertion that the increasing greenhouse gas effect is due to 
human activities?
    Dr. Christy. Oh, no. I do not disagree with that at all.
    The Chairman. Thank you.
    Dr. Mahlman, Dr. Trenberth's statement says that the main 
reason tropospheric temperatures are not keeping pace are 
because of stratospheric ozone depletion and increases in cloud 
cover. Do your models confirm those events?
    Dr. Mahlman. We have done independent calculations of the 
effect of the reduced ozone levels in the lower stratosphere, 
both in the tropical regions and in higher latitudes.
    And we calculate a double effect from that. One is that the 
reduced ozone produces a reduced downward welling of infrared 
radiation, therefore cooling the troposphere.
    But we also see that that depleted ozone in the lower 
stratosphere is transported downward and making lower ozone 
levels in the upper troposphere. Both of these effects produce 
cooling as counterbalance to the warming effect. So it is a 
real effect.
    Part of the problem is that we do not have really good 
ozone profile data, because some of the best measurements of 
ozone profiles have literally disappeared over the last 20 
years and not to be replaced. And so it is hard to really pin 
that down.
    There are also the uncertain effects, in my view, of this 
21-year time series of the quantitative effects of the El 
Chichon and Pinatubo volcanoes, whether these would also lead 
to a cooling effect in the upper troposphere that would add to 
the ozone effect.
    There is also the issue of ``What are the errors in the 
repaired satellite data and the repaired radiosonde data?'' 
Both Dr. Christy and Dr. Trenberth can comment on that as well.
    But as Dr. Trenberth quite properly pointed out, neither of 
these are well-posed measuring systems that are designed to 
produce accurate monitoring of the climate in three dimensions 
in the atmosphere.
    So we are really suffering from significant data problems 
whether that residual difference is physically robust or not. 
If I were forced to put it on Jerry's betting odds scale, so to 
speak, I would guess that it is a two out of three chance that 
there is a robust difference. But I think there is a 
significant uncertainty in how big that difference is.
    The Chairman. If other panel members wish to make comments 
on the questions that I direct to the witnesses, please feel 
free to do so.
    Dr. Trenberth, you heard me say at the beginning of this 
hearing that there is no such thing as a dumb question, right? 
If evaporation is taking place as the result of this and that 
evaporation, as you mentioned, is taking place in the oceans, 
why is the sea level rising? Is it simply because of the 
melting of the icecaps?
    Dr. Trenberth. The sea level is rising because of two 
things. About--one of the estimates is that about maybe 20 
percent of the heat from the global warming overall is going 
into the ocean. That causes expansion of the ocean and the 
evidence suggests now that, indeed, the oceans are warming up.
    The second thing is the melting of glaciers. Glaciers are 
melting almost everywhere around the world. The only places 
where they are not melting is because of increases in 
precipitation; increases in snow. And that is mainly in 
Scandinavia. And so these are the main reasons for the rise in 
sea level.
    The amount of moisture in the atmosphere is really very 
small compared with that in the oceans. And so anything that is 
stored in the atmosphere has a minuscule effect on sea level 
changes.
    But over the United States where we have the best 
measurements and--unfortunately, these measurements are really 
only reliable for about the past 25 years or so--there is good 
evidence that the amount of moisture in the atmosphere has 
increased by about 10 percent.
    That is a large amount. It is more than we would expect 
from just the greenhouse effect alone of global warming, but it 
is one of the effects, which means that there is more moisture 
that is hanging around to get caught up in storms. And it makes 
the storms more severe than they otherwise would be, rainfall 
rates heavier than they otherwise would be, such as we have 
just seen, for instance, in eastern Oklahoma and--and Missouri 
with the flooding that occurred there. And drying, of course, 
occurs somewhere else in the system. In this case, there has 
been a lot of drying over the Southwest.
    The Chairman. Dr. Watson, what has caused scientific 
confidence to increase between the IPCC's 1996 assessment and 
now?
    Dr. Watson. Well, even in the 1995 assessment, we could not 
explain the observed changes in the Earth's climate on natural 
phenomena alone. And that led to the very famous phrase, and 
that is, ``There is now--the scientific evidence now shows a 
discernible human influence on the earth's climate system.''
    And as Dr. Mahlman said, the likely conclusions from the 
third assessment report, which is currently undergoing very 
careful peer review, are likely to confirm the findings of the 
second assessment report.
    We have got improved models. We have continuing data sets. 
Obviously, the research done by the U.S. Global Change Research 
Program has helped us get a slightly better understanding of 
some of these phenomena.
    But I do not believe that there has been a radical change, 
in my opinion, of thinking over the last few years. I think 
there has been a consolidation of the thinking that we had in 
1995, which, of course, as you know, led most governments in 
the world to negotiate the Kyoto Protocol.
    The Chairman. Go ahead, Doctor.
    Dr. Mahlman. If I might just add to that. The observational 
record is very important here. The warmest years on record have 
occurred since the 1995 report, 1998 being the warmest year on 
record. And that is not something to be neglected.
    The other thing is the reconstruction, which Dr. Bradley 
showed, of the pulling together of all of the paleoclimatic 
data and synthesizing that to give us a better picture as to 
what the natural variability has been like in the past. That 
this puts the current warming in a much better historical 
context has been a significant factor, as well.
    And the third thing, in addition to the improvements in 
modeling, I would point to is improved statistical analysis and 
detection methods that have been applied to this problem.
    The Chairman. Dr. Christy, would you like to respond to 
that? I do not--I am not sure you--I do not believe you share 
exactly those views according to your testimony.
    Dr. Christy. The--all of us that work on the IPCC--and my 
chapter is the observations chapter--we will document in the 
IPCC indications of rapid climate changes that have occurred in 
the past under natural conditions, most of which can be 
explained by unusual situations in the earth.
    I would like to comment, though, on what we affectionately 
call the hockey stick diagram that Dr. Bradley showed, because 
it has this steady decline and then this rapid increase. I want 
to describe a feature of that diagram, which is not a 
criticism.
    The information that went into the first half of that 
record is very limited and as you go to the end of the record 
to the year 2000, a considerably larger amount of data went 
into that part, so that there could be a--a refinement of what 
the temperature record looks like at the end.
    If you just took the information that was available at the 
beginning and kept only that to the end, you would not see this 
dramatic spike at the end. And so it is different information 
that allows you to see what has happened in the last 100 years 
than what is shown at the beginning.
    The Chairman. But you do not disagree with the fundamental 
premise that the other witnesses have asserted that there is an 
increase in global warming. It is attributed to human activity.
    Dr. Christy. The Earth's temperature has risen. I do not 
disagree with that. And I agree that a portion of that is due 
to human effects, but I would not say all of it is due to human 
effects. I do not think anyone here might either.
    The Chairman. Dr. Mahlman, I know you want to speak.
    And then, Dr. Bradley, maybe you would like to respond to 
the hockey stick issue.
    Dr. Mahlman. Yes. If I were to have answered the question 
first, I would have raised the same two points that Dr. 
Trenberth raised, namely the fact that it is getting warmer, 
and noticeably so since the last IPCC assessment; and then also 
the amazing 1,000-year record from Drs. Mann and Bradley.
    And the other thing I would add to that is that, post-IPCC 
1995, the IPCC process made their best guess as to what the 
forcing agents for climate were over the past 150 years, and 
asked the leading model groups to make independent calculations 
of a retrospective run-through from 1760 to 2000. Effectively, 
all of the models pretty much nailed this increase in 
temperature. And models with different physics, different 
constructions still get essentially the same kind of answer.
    Now, in each one of these cases, you can make the counter-
argument and say, ``Well, that's certainly not definitive 
evidence.'' And that would be a valid point.
    But on the other hand, the fact that there are three new 
and essentially totally independent pieces of information that 
came since the last IPCC, in my mind, that shrinks the betting 
odds, shrinks the range of uncertainty. It does not make 
uncertainty go away.
    And so ultimately, it will boil down to the level of proof 
that people require in order to take meaningful action.
    The Chairman. Dr. Bradley.
    Dr. Bradley. With reference to this hockey stick issue, 
there may not be too many hockey sticks needed in the future, 
in Massachusetts anyway.
    [Laughter.]
    Dr. Bradley. We initially began this analysis originally by 
assembling as much data as we could and push the record back 
to, I think it was, maybe 1400. And on the basis of that data 
set, we demonstrated that we could reproduce the instrumental 
data completely independent from this--this network of paleo 
data. We then attempted to push it back a little bit further 
with a much sparser network of data. As you go through back in 
time, you lose more data.
    [Slide.]
    Dr. Bradley. But you can see from this record and we--we 
tried to be as honest as possible, by putting this yellow 
envelope of uncertainty. You can see the envelope of 
uncertainty gets bigger as you go back in time.
    But in the context of what the model projections are for 
the next century, the changes we have seen in the last 1,000 
years are fairly trivial.
    And so I think that is the important value of this 
perspective. You step back beyond the period of our own 
experience, the last century or so. You look at it in the 
longer term, when clearly before 1800, it was all due to 
natural variability. It was not due to greenhouse gases--a pre-
industrial level of greenhouse gases.
    So what you see in that graph is just the earth doing its 
thing, solar variations, volcanic eruptions, whatever. Those 
are the amplitudes of change that we believe are real.
    And then you compare that with what are projected to--to 
take place in the future. And you can see that it is just off 
the scale.
    The Chairman. My final question--I appreciate the 
indulgence of my colleagues.
    If the blade part of the hockey stick here in your graph is 
largely accepted as valid, why is it that you think that there 
is not greater concern than that exists today about that blade 
of the hockey stick?
    Dr. Bradley. You know, this diagram is patched together 
from two pieces of information. I do not think it has been seen 
before, in fact.
    The left-hand side, the red and the yellow represent--the 
red is the instrumental element; the yellow is the 
reconstruction; and the gray area represents the projected. So 
that brings it all together and puts it in perspective.
    I think this diagram is compelling. And if it is seen more 
widely people will be forced to face the fact that these are 
very large changes. I think as we develop our science and we 
make these kinds of figures available to people, they will 
begin to realize the magnitude of change.
    Now, why do we not take it more seriously? Because the 
problem is incredibly difficult to resolve, as you no doubt, 
grapple with within yourself.
    How do--how are we going to deal with the fundamental use 
of fossil fuel in our society and around the world? How are we 
going to deal with the fact that the population growth is going 
to double this century? That is the fundamental driver of this 
change in temperature.
    Unless we can come to grips, we obviously are not going to 
do much about changing population growths. We have got to do 
something about the carbon-based fuel economy of the world. We 
have got to come up with more efficient ways of managing our 
society.
    And in the long run, it obviously must be more beneficial 
to our economy to use less fossil fuel. It has got to be more 
sensible to run an engine on less energy, to run a factory on 
less energy, and use less energy to heat or cool our homes. The 
short-term costs may be profound. But the long-term has got to 
be a boost for our overall commerce, I would think.
    The Chairman. Any other panelists wish to--go ahead, Dr. 
Mahlman. We will go right down the list. Dr. Christy, you are 
included in this assessment.
    Dr. Mahlman. Oh, I think this is an extremely important 
question, and if I could repeat the question to know I 
understand it. Given all this, why are people not more 
concerned than--than they are----
    The Chairman. Than they--yes.
    Dr. Mahlman [continuing]. Governments and everybody? I have 
had the good fortune to have spoken face to face to the order 
of 10,000 people on this--on this subject. And this comes up 
all the time.
    And it is a universal issue. And I would submit on the 
basis of my encounters with all these people that it boils down 
to a couple of things.
    One is that it is a hard problem to immediately associate 
with--with a really scary issue, until you start doing what we 
have been doing today, which is looking at each thing and 
finding out what sectors are--are affected and how they might 
be affected. And then suddenly, the potential for serious harm 
begins to creep out of that. And the second part----
    The Chairman. By the way, including a new European--a group 
recently discovered a greenhouse gas with frightful 
characteristics, SF--SCF3, I think.
    Dr. Mahlman. Yes.
    The Chairman. You are familiar with that?
    Dr. Mahlman. Yes. Dr. Watson and I will probably both 
quickly say that this is part of a class of extraordinarily 
long-lived greenhouse gases, most of them human produced, that 
have tremendous global warming potential. It is in the IPCC and 
the ozone assessment reports.
    And there is nothing, to me, particularly new about that. 
It is part of a whole class of fluorocarbons and other very 
long-lived greenhouse gases that exist in a few parts per 
trillion, that probably will be removed quickly from 
manufacturing processes. So I do not see this as a new issue.
    The second thing I would like to say about why people are 
not acting and concerned so much is, in my view, this problem 
has an extraordinarily high degree of difficulty factor. It is 
very easy to demagogue it from all sorts of viewpoints, because 
it is not just a matter of what the U.S. does or what this 
Committee does. It is what the whole planet does.
    And, in that sense, it seems so overwhelming that we, 
therefore, do not have to do very much. And, of course, in this 
problem, like many other problems, a non-decision is a decision 
in the sense that we all are implicitly agreeing to keep 
increasing emissions of CO2 into the atmosphere.
    The Chairman. Dr. Trenberth.
    Dr. Trenberth. Yes. Thank you. Climate change is not 
necessarily bad. When you deplete the ozone layer, the 
consensus was that this was a universally bad thing and, 
therefore, a coordinated activity could occur. But warming in 
wintertime can be beneficial for some things, for instance.
    The real problem, which I do not think is adequately 
appreciated, is that change by its very nature can be 
disruptive and tends to be disruptive. And even though we may 
be changing in some areas to a climate that is better in some 
sense, it is not going to stay there. It is going to continue 
to change.
    In fact, we are entering a period of instability in our 
climate, and we are not going to know just what the climate is 
going to be next year or for the next 30 years, and actually 
this puts an imperative on making better climate predictions so 
that we will have those predictions to be able to base 
decisions upon, because we will not be able to use the climate 
of the past to make those decisions.
    And this applies in so many parts of society and activities 
that we have, such as planning of dams and especially water 
resources. And I personally think the main pressure points on 
society will be changes in precipitation, changes in extremes, 
managing water and water resources, portable water in 
particular, and the effects of changes in the extremes on 
society and on the environment.
    Unfortunately, our data bases for those are not as good as 
they are for mean global temperature. As I mentioned before, a 
one-degree change in global mean temperature translated locally 
does not mean much. But, in fact, this record has included 
things like the Little Ice Age, which caused major disruptions 
in Europe.
    And so regionally, the manifestations of this can, indeed, 
be very great and profound. And so getting these aspects across 
to the general public and to policymakers is not an easy thing 
to do.
    The Chairman. Dr. Christy.
    Dr. Christy. I agree with Dr. Trenberth, who actually is my 
former advisor when I was back in graduate school. And I 
usually have a difficult time to be more skeptical than he is, 
but sometimes I can.
    In Alabama, the temperature has fallen over the last 105 
years, so people right there are not going to be very concerned 
about global warming when the temperature in their local region 
has not warmed at all. The second thing----
    The Chairman. If the Gulf shores is inundated, at least in 
the southern part of the state there remains some concern.
    Dr. Christy. I repeatedly advise people who are interested 
in beach-front property that I do not care about six inches of 
rise relative to hurricanes. It is the next hurricane that is 
going to visit the area that is the problem, and they should 
stay away from the beach for that reason.
    Cheap energy means longer and better lives. And I have seen 
that. I was a missionary in Africa, and I saw people who 
literally died when energy costs increased because they just 
lived right on the edge of existence. So I would be very 
concerned about increasing the cost of energy for the poor 
people of Alabama, and those around the world.
    And in agreement with everyone here, if there is some way 
to keep energy cheap and not produce CO2, I am all 
for it. That is fine, if we can do that.
    Now, lastly, fortunately in this business, CO2 
itself is plant food. It is not toxic. CO2 does not 
bother us, and it invigorates the plant world. The plant world 
you see around you evolved at a time when there was ten times 
as much CO2 as there is now. So that is one thing 
that we can be thankful for, at least in terms of the toxicity 
that CO2 is harmless.
    It is the climate change issue, the secondary effect of 
CO2 that is of concern to us all.
    The Chairman. Dr. Watson.
    Dr. Watson. My comment would be, simply, most scientists 
are concerned about climate change. Most governments are 
concerned about climate change, which is why most of them 
signed the Kyoto Protocol.
    Some businesses are becoming more concerned about climate 
change. Shell and B.P. in Europe, others in the U.S. have all 
now got internal trading systems, and they have got their own 
targets, and they are very similar to Kyoto.
    One of the big problems, however, is what differentiates 
this from the ozone issue. In both cases ozone depletion and 
global warming is largely being caused by emissions from the 
rich countries, the U.S. and Europe, Japan.
    With ozone depletion, the impact is skin cancer on light-
skinned people. Americans cared about it. So did the Europeans.
    The major impact of global warming will be on developing 
countries and especially the poor in developing countries. The 
U.S. will be hit, but the biggest impact is on developing 
countries. So it does not hit home in quite the way skin cancer 
did with the ozone issue.
    But the basic point is--and that is why Shell and others 
are starting to act--there are cost effective solutions, 
especially when we use the so-called flexibility mechanisms, 
emissions trading internationally and project-based joint 
implementation.
    There are distributionable issues. The coal industry is not 
going to be a winner. The renewable energy industry will be a 
winner, and even the gas industry. So there are 
distributionable issues and political forces at play, 
especially in the U.S. and in, say, Australia, where there is a 
lot of cheap coal reserves.
    There is no question we can de-carbonize the energy system 
in the next 50 years. We do not need to do it in 5 years. We 
have to have a long-term strategy to de-carbonize our energy 
system.
    And the population issue is also a manageable issue. If we 
follow the Cairo principles of culturally acceptable forms of 
contraception, education especially of girls and empowerment of 
women, we can actually start to lower the projections of 
population.
    And the latest projections suggest that there could well be 
a stabilization around 9 billion people, only 50 percent more 
than now and starting to decrease by the end of the next 
century.
    So these are indeed solvable issues, but it takes political 
will and it takes partnership between government, the private 
sector and civil society.
    The Chairman. Dr. Christy, you will have the last word from 
me.
    Dr. Christy. OK. I just want to say ``Amen'' to something 
Dr. Watson said. In my experience as an educator in Africa, the 
educational component was the key ingredient to seeing those 
societies bring about a better situation in the lives of the 
people, and I just wanted to echo the need for education of 
women in those countries.
    The Chairman. Thank you very much.
    Senator Kerry.
    Senator Kerry. Thank you, Mr. Chairman.
    [Pause.]
    Senator Kerry [presiding]: It seems to me that there is 
pretty broad agreement among you, not withstanding the 
differences, Dr. Christy, in your assessment of what you are 
willing to conclude from the satellite observations.
    You have a differing of opinion about what the consequences 
of global warming may be, but you do accept the fundamental 
premise of the human impact and the basic findings of the 
increase of warming taking place.
    And I take it that these circumstances have serious 
implications for us involved in policymaking. You do not think 
we should do nothing, do you?
    Dr. Christy. In terms of policy, I am not an expert, but--
--
    Senator Kerry. Well do you think we should let CO2 
double? Should we just sit around and watch this happen? Is 
that your policy recommendation?
    Dr. Christy. If I were to predict, I would say it was going 
to double no matter what policy is adopted.
    Senator Kerry. Realizing it is, would you simply sit back 
and accept that, or would you now begin to do greater research 
and see what----
    Dr. Christy. I would certainly support, especially in terms 
of energy use, research on the alternatives that can be used to 
produce energy, and keep it cheap and affordable, because cheap 
energy means longer and better lives.
    Senator Kerry. So are you saying, about this process--I 
mean, here are four distinguished peers of yours----
    Dr. Christy. And I feel surrounded sitting here.
    [Laughter.]
    Senator Kerry. Well, it is hard to find a whole lot of 
contrarians now. There are a few more but it is hard to find it 
is hard to fill a room with them. How many people are on the 
IPCC? 2,500, is it?
    Dr. Trenberth. There are several hundred as authors. There 
are several thousand, indeed, involved as reviewers. And indeed 
John is one of them, and so is Richard Lindsen, who is also a 
notable skeptic.
    Senator Kerry. Is there a great difference of opinion 
between those 200?
    Dr. Watson?
    Dr. Watson. I think the majority see the climate issue the 
same way. They all recognize what is known. They all recognize 
what is unknown.
    I would say there are a half a dozen key contrarians, which 
include Dick Lindsen, Fred Singer and Pat Michaels, but I would 
say the large majority of the scientists clearly fall on one 
side.
    And in the IPCC, we are trying desperately to make sure the 
full range of views is fully exposed. And so we can actually 
say what is known with certainty, what is less known, why do 
the majority think one way, and the minority think another. So 
we can actually explain what the implications of uncertainties 
are for policy formulation.
    Senator Kerry. Dr. Trenberth, what is your sense of the 
schools of thought here, and how we should come up? What is the 
difference between these four or five that have been mentioned 
as the key contrarians and the vast majority who believe 
otherwise?
    Dr. Trenberth. I think we need to take into account some of 
the ideologies that come into play and recognize that there are 
different views of the world.
    In the IPCC process, particularly in working group one, 
what we try to do is to make the best statement as to what can 
be said about this problem of global climate change and leave 
to the politicians what should actually be done about it. And 
often, I think, those things do get mixed up. And they often, I 
think, get mixed up by some of those people.
    We need to recognize that there are many value systems in 
the world today, from the extreme environmental position, which 
says we should stop the increases in greenhouse gases 
absolutely and mitigate the problem; to people who say 
technology will solve the problem, and we can just adapt to it 
as it goes along; to people who advocate sustainable 
development; to people who have vested interests.
    And we have seen this in the tobacco industry, for 
instance, where often the strategy is to denigrate the science 
and to say that there is not a problem and recognize that they 
do have a vested interest. I do not think it is so much what 
you do about the problem, but how you do it and doing it over 
an appropriate time scale, that would help to assuage some of 
the projections that you see.
    Senator Kerry. Well, it is completely fair and, I think, 
accurate to say, that some of the denigration of science has 
emanated from specific industries highly vested in fossil fuel. 
Is that accurate?
    Dr. Trenberth. That is, I believe, accurate.
    Senator Kerry. Is that accurate, Dr. Mahlman?
    Dr. Mahlman. I think it is accurate, but I would answer a 
little bit differently, in that if you look at this problem 
worldwide, there are people who are trying to frame-out the 
science the best that we know.
    Some of the issues we have just discussed here are ones 
where we can sit around at a table and discuss in a civil way 
and say, ``Well, I disagree with you here or there,'' and we 
would all go out to lunch together, and there would be no 
yelling, or screaming or slugging going on.
    [Laughter.]
    Dr. Mahlman. But on the other hand, I think it is important 
for all of us to recognize that there are contrarians and there 
are also exaggerators. OK? And both are essentially, in my 
view, making points because of agendas that are somewhat 
independent of scientific analysis, and you can say, ``Well, I 
do not see that as necessarily a new phenomenon on Capitol 
Hill.'' But it----
    [Laughter.]
    Dr. Mahlman [continuing]. Is part of human nature to have 
people torque the facts a little bit to hustle whatever their 
position is. And, as you know, they say, ``That is part of the 
policy debate,'' but it is also part of the values conflicts 
and everything else.
    I have gotten so that I do not get all that concerned about 
it, because I think it is part of the process of dealing with a 
problem that is extraordinarily difficult. Lots of folks see 
that a very special thing is going to get hurt by mitigation or 
is going to get hurt by climate change. I thus consider this to 
be the real greenhouse warming controversy.
    Senator Kerry. Governments came together in Kyoto to adopt 
a policy, a response, and hopefully this policy does not 
represent grinding of a particular axe, but represents a 
reasonable approach in the middle. I do not think the Chairman 
or I or others want to adopt a policy we do not need to adopt.
    I do not have any industry axe to grind on one side or the 
other. I mean, I am trying to respond to what I see is a 
problem caused by human beings, which is increasing because of 
our unwillingness to reduce what we are doing that is causing 
it. Now, we have got to make a decision, because there is some 
money involved here. Do we need to reduce the level of 
emissions or do we not? Countries signed on in Kyoto to the 
notion that we do; that reducing emissions is a worthwhile 
goal. Does anybody disagree with that? Is it a worthwhile goal?
    Dr. Mahlman. I would like to comment. I was quoted in the 
New York Times before the Kyoto Conference. And I have written 
a paper in Science Magazine, you know, prior to Kyoto.
    At that time, I said that the best Kyoto could do would be 
to set up a small, but significant decrease in the rate of 
increase of carbon dioxide in the atmosphere. And, this 
statement was somewhat controversial at the time. But the whole 
point was, that even Kyoto itself, if it were fully 
implemented, would still be nipping around the edges.
    Senator Kerry. Absolutely.
    Dr. Mahlman. And I said this not to demean the Kyoto 
process, but more or less to educate people that are probably 
going to be whittling away at this problem for the rest of the 
century. And Kyoto is kind of ground-zero, or maybe Rio was, of 
the process of what the world is going to do about it and how 
all of the hard issues can get worked out.
    And so, therefore, Kyoto, from the point of view of the 
problem, was a very small step; not a radical, the world is 
going off the edge if we implement the Kyoto Protocol. And so, 
the next question is, what will happen in the next round?
    Senator Kerry. Does anybody else want to add to that? Dr. 
Bradley, and then Dr. Watson.
    Dr. Bradley. I think it is clearly--there is a long ladder 
we have to climb. And Kyoto is, perhaps, just the first rung on 
that ladder, but it is an important step, because it forces 
governments throughout the world to recognize the problem and 
to take steps to address the problem.
    It is not going to solve the problem, but it--but just like 
the Montreal protocol, which began small and gradually made 
stronger and stronger steps, I think that is what is necessary 
in Kyoto.
    Senator Kerry. Dr. Trenberth.
    Dr. Trenberth. Well, the Kyoto Protocol is flawed, at least 
in some respects, especially insofar that it is not truly 
global, in terms of the agreements that exist.
    The important thing about it is that it would buy time. The 
estimate is that doubling of carbon dioxide would be delayed by 
about 10 years. And people then ask, ``Is it worth buying that 
time?''
    And I think it, very strongly, is, because the climate is 
going to change, and every step we can take to buy that time 
provides us with better capabilities of planning for what is 
going to happen and for planning the adaptation that will be 
necessary to occur in the future.
    And so, I think it is a desirable first step, even if a 
flawed first step.
    Dr. Watson. Yes. I think it is quite clear that governments 
from around the world recognize that human induced climate 
change is a threat to society. And what we need is some first 
steps toward meeting the ultimate objective of the convention, 
which is Article Two, which calls for the stabilization of 
greenhouse gas concentrations in the atmosphere.
    They also recognize, and I agree, that it is very important 
to differentiate the responsibility between developing and 
developed countries. Energy is needed to alleviate poverty in 
developing countries and for having economic development.
    But why is the Kyoto Protocol such an important first step? 
It will stimulate the development of new energy technologies. 
It will stimulate policy reform, both in developed and 
developing countries. We will find better mechanisms, which 
will involve all sectors and an appropriate enabling government 
framework for technology transfer. And it will give us the 
chance to put these flexibility mechanisms in place.
    So, even though it is not a global convention, it does 
recognize, just like the Montreal Protocol did, that the 
developed world has the institutional, financial, and technical 
capability to take the first steps.
    As they take those first steps, we will see a flow of 
technology transfer, such that it will be in the best interest 
of China and India to also reduce their greenhouse gas 
emissions, and simultaneously to reduce their local air 
pollution and regional air pollution.
    So, I believe it is a very well founded first step, but 
clearly, at the end of the day, all countries will have to 
reduce their greenhouse gas emissions, if we are going to meet 
the ultimate objective of Article Two. There is no question.
    Senator Kerry. Well, I agree with that. I accept that. I 
think that the difficulty is that the current political 
formulation in the United States makes it difficult for us to 
embrace that first step, absent at least an acknowledgment by 
the developing countries that they are willing to adopt some 
measures. Tackling the problem is going to be very complicated.
    You know, I was involved and I led the fight on the floor 
to try to create some sort of rational approach in the Herd-
Engle Amendment. And I am sympathetic to the notion that people 
in the United States are going to be hard-pressed to buy into 
something they do not see other people also buying into.
    The fact is, though, that China and other developing 
countries are currently embracing significant steps to achieve 
clean air. And they are moving forward. In China, for instance, 
they are restricting certain kinds of vehicles, and are 
beginning to get conscious of these environmental issues. And 
they could actually qualify for participation very easily, 
based on many of the things they are doing now.
    What we have is a dividing line between us--the traditional 
view of the developed (and developing) world. We have gotten 
stuck in cement for lack of people's willingness to really look 
at the long-run here. And I think we need to have some 
significant diplomacy exerted in order to try to pull us 
together now. We should not be that far off.
    But let met just touch on a couple of other quick points. I 
know Senator Brownback wants to ask questions.
    Just for the record, the 400,000 year basis that you are 
drawing conclusions on CO2 increase from is based on 
the ice core, correct.
    Dr. Bradley. These are little bubbles of gas; essentially 
samples of the atmosphere that have been trapped in the ice and 
buried for years.
    Senator Kerry. I just want the record to reflect that I 
have read it and I am familiar with it. I want the record to 
reflect the accuracy of that judgment showing that it is not 
some kind of hypothesis.
    You are able to take trapped CO2 through the ice 
cores, through the ice that has been there through these 
millennia, and measure precisely the level of CO2 
increases over that period of time, correct?
    Dr. Bradley. That is correct.
    Senator Kerry. And that is how we know to a certain degree 
the demarcation point of the Industrial Revolution and the 
introduction of CO2 by human industrial efforts that 
has made this marked increase.
    Dr. Bradley. That is correct.
    Senator Kerry. We can track precisely the level of weather 
changes, heat changes over the last 105 years, at least, by 
measuring the CO2 gas in these cores.
    Dr. Bradley. That is right. I might also add that this 
420,000 year limit is only because that is as long an ice core 
record as we have. I am sure if we had a 2 million year ice 
core record--I feel confident that if we had a 2 million year 
ice core record, we would still be heading toward uncharted 
waters in the future.
    Senator Kerry. Now, they also know that these things called 
``sinks'' or entities that sequester carbon dioxide are 
ineffective on a constant basis. But the ocean is also a 
primary sink, correct? It is a huge sink.
    And the ocean, in fact, is warming. And the ocean contains 
very significant amounts of CO2 that it holds onto 
for long periods of time. It is my understanding that the ocean 
could conceivably have some limit as to how much CO2 
it, in fact, can sequester.
    And at some point, if we were to continue to pour it in, we 
could have overload, so that all of a sudden the ocean is no 
longer available as a major sequesterer of CO2, 
correct?
    Dr. Bradley. That is correct.
    Senator Kerry. And that could then have a profound impact, 
in terms of all of a sudden releasing this CO2 The 
benefits of this once extraordinary sink are then negated. And 
where do we go from there, is a legitimate question, is it not?
    Dr. Bradley. Yes. There are a number of these kind of 
thresholds in the climate system that we do not have a good 
handle on. And that is one, for sure. And changes in the ocean 
circulation, in general, are a great uncertainty.
    Senator Kerry. And our weather in the northeast is 
significantly dependent on the ocean, on the Gulf Stream and on 
its relationship.
    Dr. Bradley. That is right.
    Senator Kerry. So, if that were to simply be altered in a 
major way, we could have--who knows what--perhaps some 
catastrophe.
    Dr. Bradley. Yes. That is true in most parts of the world, 
wherein you have the economy and society has developed based on 
what they are used to.
    Senator Kerry. Given that reality, we make judgments here 
everyday about flood plain settlement, about AIDS--the rate of 
spread of AIDS, about tobacco. We have spent $60 billion in the 
last few years, based on judgments we make about potential 
threats from North Korea or Iraq or Iran.
    Here is a far more realistic, in my judgment, and definable 
quantifiable threat. And we are not even doing an adequate 
level of climate change research.
    Dr. Bradley. Exactly. In fact, I would say, that we can 
carry on doing research. It is a trivial amount of money in the 
context of what we spend on other things, but what is really 
needed is a massive national effort to develop alternative 
energy sources to find non-carbon based fuels that will allow 
us to continue our economic progress without continuing to 
increase the level of CO2 in the atmosphere.
    Senator Kerry. But is it not true that, in fact, we are 
much further down that road than most Americans know, with 
respect to hydrogen, engine fuels or other alternatives?
    Dr. Bradley. I am not sure where we are, but wherever we 
are, we are not far enough along. Certainly, on the global 
scale, this is a critical issue.
    Senator Kerry. My point is, simply, that in 1980, before 
President Reagan arrived in Washington, we were the world's 
leader in alternatives and renewables. And we had created an 
energy institute out in Colorado, I believe. And professors 
left their universities and gave up tenure to go out there, and 
research the American future in renewable and alternative 
energy.
    In 1981 the funding was cut completely. And we gave up our 
leadership to the Japanese and Europeans in those sectors, so 
that when the Communist block countries fell and they started 
searching for people who had the technology, they looked 
elsewhere than the United States.
    Dr. Bradley. That is exactly right.
    Senator Kerry. Now, I do not think this is as complicated 
as we make it. The threat may be enormous, but the truth is, if 
we were to unleash the technological capacity of this country 
to truly face this problem--we have an extraordinary capacity 
to develop jobs and economy and a future that is sustainable. 
But it seems to me that we need to face the difficulties of 
educating the public and drawing the people into the potential 
solutions here.
    Problems are real, but solutions are there. We can 
certainly work through this, I think, providing we show some 
leadership.
    Does anybody else want to make a comment?
    Dr. Watson. Yes. I would like to make one comment on it. 
Technology is very important and R&D is important, but the 
policy framework is crucial.
    We are never going to get renewable energies to penetrate 
the marketplace unless we internalize the social costs of 
pollution, for example air pollution and acid deposition, and 
eliminate fossil fuel subsidies. It is worse in other countries 
than the U.S.A. But it has to be a combination of research and 
development into new energy technologies and policy reform.
    There is no way that one is ever going to get renewable 
energies in most countries, because of the subsidies on fossil 
fuels and they subsidize the railways to transport coal, and 
they do not internalize the social costs of environmental 
pollution.
    So, we do not have a level playing field. It does not 
matter how well you do on technology. So, it must be the 
combination of technological development and policy reform.
    And the comment that should be made is, unfortunately, both 
public sector and private sector research in energy has 
decreased in every country in the world, except for Japan. And 
90 percent of their research is on nuclear power, not on 
renewable energy.
    In most of the European Union, energy research has dropped 
by a factor of five to ten. And in the U.S., in real terms, it 
has also dropped. And most of the U.S. money goes into, again, 
fossil fuels and nuclear power. Only 20 percent of the energy 
R&D budget goes into either renewable energies or energy 
efficiency.
    And the other problem that compounds this, is that not only 
has public sector research dropped off, but because of 
deregulation of industries and liberalization, private sector 
research has dropped even further. And so, we have the 
unfortunate situation of both public and private research 
dropping precipitously.
    We do not have the associated policy reform. And so, while 
we have been debating climate change at the convention and the 
Kyoto Protocol, the very instruments we need to enact a 
decarbonization of the energy system have actually been taken 
away from us.
    Senator Kerry. Well, with respect to that policy, let me 
just add, I am a passionate and deeply committed advocate of a 
much more thoughtful foreign policy, where we, in fact, have a 
much more significant component of technology transfer and 
technical assistance.
    And a year ago, I managed to get Jim Wilbinson, to his 
enormous credit, to commit the World Bank to holding the 
conference in, of all places, Hanoi, Vietnam. It is about 
precisely this kind of development.
    And all the donor countries came, including Japan, to think 
about how, as they need to put in a power plant, we could 
provide them with an alternative to simply burning high-sulphur 
coal. We could even provide them with direct grant transfer of 
some of our technological abilities to be able to do these 
things, so that they can develop without repeating the mistakes 
that we have made, and learn, at the same time, that this is 
not a Western conspiracy to keep them from sharing in the 
abundance and wealth of the world, which is the way they view 
it today.
    I concur with you that we desperately need to have a change 
in policy and a much more thoughtful approach to this. I thank 
you for your comments today. And I thank my colleague for his 
forbearance, and look forward to continuing this dialogue with 
you.
    Senator Brownback [presiding]. I want to thank the panel 
for the presentation. It was excellent. I thought it was very 
illuminating.
    And it reminded me just--in looking at how much everything 
is interconnected. When you do one thing, and it just moves 100 
different things, different places. I guess the philosopher 
says that you pull on one place in the universe and everything 
else moves. And it just really is interconnected.
    Let me ask you--Dr. Bradley, you have already started to 
articulate some of this, about what you think the policy moves 
are that we should do today. Renewable energy sources, I think, 
is what your primary focus is.
    Are there other specific policy recommendations outside of 
implementation of the Kyoto Treaty or the renewables that you--
some of you would like to put on the table that we should start 
to discuss now in the U.S. Congress?
    Dr. Bradley. I'm not convinced that renewable energy is 
going to be the solution, but I think one of the simplest 
things is conservation. And by that I mean using more energy-
efficient processes, whether that process is heating a house or 
keeping the heat from going out of the roof; heating water; 
obviously, more efficient automobiles, and that goes for trucks 
and public transportation, too.
    Those issues can be--can be encouraged with tax credits. As 
I recall, the Carter Administration there were--they introduced 
tax credits for energy conservation measures. And that was a 
boost to a whole emerging economic sector, which was the 
development of these products.
    And it seems to me that would be a fairly painless way of 
encouraging energy conservation, by providing significant tax 
credits for people who buy cars that get more miles per gallon, 
people who introduce energy-efficient measures to their homes, 
et cetera. And that, in turn, would generate economic activity 
that could be transferred to other countries. And so, it would 
be a boost to our economy.
    Senator Brownback. Dr. Trenberth.
    Dr. Trenberth. I mentioned before that it is not so much 
what you do, as how you do it. One of things which was 
mentioned by Dr. Watson was the importance of taking into 
account the lifetimes of the infrastructure that exists and 
planning appropriately. And I think that is very important.
    A good example might be, for instance, automobiles. If we 
were to increase the cost of gasoline by a dollar tomorrow--
well, firstly, that would not be politically viable. And 
secondly, it would cause major problems in the whole of the 
economy; very disruptive. But if we increased the cost of 
gasoline by a penny, it would be lost completely in the noise.
    So, what would happen if we increased the cost of gasoline 
by a penny every month? After 10 years, we would have $1.20 
increase in the cost of gasoline. In fact, even then, the cost 
of gasoline in the United States would be much less than it is 
in Europe and in most other places around the world.
    But if we did that and it was a certainty that it was going 
to happen, then because the lifetime of a car is less than 10 
years, the next time people went to buy a car, they would think 
twice about the energy-efficiency of the car that they are 
buying.
    And it is this kind of thing that would enable people to 
plan ahead in a reasonable fashion and adapt to the changes in 
tax policy. And of course, you can use the increases in taxes 
to offset other taxes, so that it is tax-neutral. This kind of 
activity is the kind of thing which I think emphasizes the 
point I make in my comment that it is not what you do, it is 
how you do it.
    Dr. Watson. Yes. I think one needs to look at all facts of 
this. There is no simple home run here. One needs to look at 
the technology on both energy supply and energy demand. So, 
efficient vehicles, efficient housing, and more efficient 
industry can help.
    On energy supply, you can have more efficient use of fossil 
fuels. It does not mean the elimination of fossil fuels--more 
efficient production of energy from fossil fuels.
    You can have fuel switching, from coal to gas. One should 
think renewable energy.
    The policy issues are very, very important policy reform. 
There is no question. And Kevin is absolutely right. We must do 
this in the economically least disruptive manner, which means 
we need a long-time perspective.
    Just like the sulphur market, when there was a decision by 
Congress to reduce sulphur emissions in the U.S. The most 
important thing they did, did not actually involve new 
technologies, but it was the emissions training system that was 
put in place.
    So, one could actually stimulate a market--in this case, on 
carbon--so that both domestically and internationally, you can 
buy and sell carbon as a commodity. That will absolutely drive 
down the price.
    So, one needs to look at both the technology, but also the 
policy framework. And I think that one should--and of course, 
as you, yourself, have mentioned, I think there is a 
significant opportunity through better forest management, 
better agricultural management, better rangeland management.
    And so, again, thinking through the policies that might 
stimulate the farmer to move toward no-till agriculture. What 
do we do with some of the degraded lands? It could actually be 
very useful land for either afforestation or reforestation or 
just simply to improve soil carbon. We must not lose the 
potential in soil carbon.
    My view would be, do not move for one simple home run 
solution, but look right across the wide variety of options, 
both in technologies and in policies.
    Senator Brownback. Dr. Watson, when you look 
internationally on the issues of carbon sequestration in the 
construction of the--some of the forests in areas, do you think 
that that is a key component of--as well as to look at this 
issue, or is it not a major issue?
    You have mentioned the complexity of this and the 
multifaceted solution that is going to be required, if we are 
going to try to pull more carbon out of the atmosphere. 
Regardless of how it got there, regardless of what may be some 
of its impact in the future, we want to get some of this 
CO2 out of the atmosphere. And we could, I think, 
most would agree on that.
    What do you see, as that component of it on the 
international scale?
    Dr. Watson. Today we put about 6.3 billion tons of carbon 
per year into the atmosphere from using energy. And from 
tropical deforestation, we put somewhere around 1.8 billion 
tons of carbon per year. So, from a total of 8.1, 25 percent 
comes from tropical deforestation.
    Therefore, slowing tropical deforestation is a major 
component to acting to protect the earth's climate system. It 
would also have incredible benefits to the biodiversity and 
water resources in those regions. But it is unbelievably 
political.
    I chaired the recent IPCC report and part of my testimony 
is on land use, land use change in forestry. And what we see 
from many developing countries--and this is a political, not a 
scientific issue--is that they are willing to think through 
issues of afforestation and reforestation, and issues such as 
no-till agriculture.
    But Brazil, in particular, is absolutely opposed to 
including avoided deforestation into the Kyoto Protocol through 
the Clean Development Mechanism Article 12. It is a political 
issue. It has to do with the Federal/state government 
relationships, that is to say the interplay between the Federal 
Government and the state governments in Brazil. It is a 
question of whether or not, if you avoid deforestation in one 
part of Brazil, it will accelerate it in another part of 
Brazil.
    So, you have to understand the drivers behind 
deforestation, in order to say that you can actually stop 
deforestation. You need to know all the underlying political 
and technical and industrial factors that drive it.
    But there is no question in my mind that if we can slow 
deforestation in the tropics, and if we can accelerate 
afforestation and reforestation, both in the tropics and high 
latitudes, it would be a major contribution to climate change 
and to save the world's biological diversity.
    Senator Brownback. On the afforestation and reforestation, 
would we not actually affix or sequester more carbon if we--if 
our policies actually focused in that direction, avoiding some 
of the political issues that you have identified?
    Dr. Watson. Yes. On afforestation or reforestation--forests 
grow slowly, but surely, over the next 20, 50, 100 years, 
depending on the lifetime of the forest, you would sequester 
carbon. And there is no question it is a very good thing. But 
if you can avoid deforestation, it stops a big slug of carbon 
going into the atmosphere.
    And of course, if one is trying to avoid deforestation in 
the tropics, one could argue there are national sovereignty 
issues at stake, as well.
    I think we need the dialogue right across the world on all 
of these issues simultaneously. We have got to recognize 
political sensitivity, but we also need to recognize that 
avoiding deforestation is a powerful tool to keep the carbon 
where it is.
    Afforestation and reforestation will draw additional carbon 
from the atmosphere, but avoiding deforestation stops it going 
in, in the first place.
    Senator Brownback. Dr. Trenberth.
    Dr. Trenberth. Senator, you were asking especially about 
the sequestration of carbon dioxide, and there is also new 
technology, and I believe Norway is the leader in this area, 
where they are taking carbon dioxide out of the atmosphere as 
it is generated, essentially, and then the technology is to 
sequester it in the oceans or elsewhere.
    I am not an expert in that area, but I did want to get on 
the record that there are, indeed, other technologies, but of 
course there is a cost attached to doing that.
    Senator Brownback. Other policy suggestions, or 
particularly in the carbon sequestration is a--I think that 
is--that is a key point of political reality. And one needs to 
recognize political reality, you know, here, as well.
    We can probably spend a great deal of time arguing about 
how global warming is occurring. We could probably spend and 
probably will spend a lot of political time discussing, OK, 
whether Kyoto is a good or bad treaty for us to enter into. And 
then you are going to have the political forces that will line 
up both ways on that. And those are legitimate debates and 
discussions, and which you are going to have them in.
    You could also start to do something right now. And you 
could recognize what the market will bear here and what we can 
start to do, which is, in my way of thinking, probably what we 
ought to be--perhaps we can, first and foremost, starting with 
now, because it starts to eat away, as one of you said--I think 
it was Dr. Mahlman.
    He pointed out that even Kyoto just kind of nips around the 
edges of this. ``And we will probably be doing that for the 
next century,'' was the quote of one of you.
    I think there are ways that we can get started on this. I 
think we will need to have the dispassionate dialogue and 
recognize people's concerns and political realities, and then 
say there are ways that we can actually--we can move forward 
and start to address the problem now, rather than just having 
the issues back around.
    Recognizing that that is probably the start of a lengthy 
process of how do we deal with issues like this in ways that 
are least disruptive.
    Dr. Watson. If one simply makes carbon a commodity, just 
like maize or wheat is, then there is real value in carbon. And 
that is how you can then trade carbon either within a company 
as British Petroleum is doing now. You can trade it nationally 
within the U.S. or any other country, like we trade sulphur at 
the moment. And it can be traded internationally.
    As soon as you make carbon a commodity and it has value, 
then it will be a real incentive to farmers, it will be a real 
incentive to foresters, to improve agricultural practices, 
forestry practices, essentially be paid for those better 
management practices, and then also get the multiple benefits 
of increased soil fertility, et cetera.
    So, one of the challenges is putting a policy framework 
together, where one has real value in carbon and will also 
stimulate research and development and will also stimulate 
energy-efficient technologies. There is no question, that the 
challenge is putting the framework together.
    Dr. Bradley. If I could just pick up on a point there, and 
that is that many of these strategies do have multiple 
benefits. Bob talked about the preservation of biodiversity 
in--clearly, it will be more beneficial to the economy if we 
use less fuel to power our automobiles, power our plants and so 
on.
    It is going to be better, ultimately, if we can do things 
more efficiently like that. So, we ought to develop sort of a 
table of strategies that have the least political disagreement 
and the maximum collateral benefits that we can imagine, so 
that we can start chipping away at this very large issue by 
taking some of these measures.
    Senator Brownback. It is picking the low lying fruit as 
best you can.
    Thank you very much. You have been an excellent panel and 
an excellent discussion. I know the Chairman would like to hold 
additional hearings on this. And I think it certainly is 
warranted.
    The record will remain open for the requisite number of 
days, if you choose to submit additional things for the record.
    The hearing is adjourned.
    [Whereupon, at 12:15 p.m., the hearing was adjourned.]

                            A P P E N D I X

   Article Written by Dr. Jerry Mahlman, Director, Geophysical Fluid 
  Dynamics Laboratory, National Oceanic and Atmospheric Administration
                  Science Magazine, November 21, 1997
      Uncertainties in Projections of Human-Caused Climate Warming

    Mankind's activities have increased carbon dioxide (CO2) 
in the atmosphere. This increase has the potential to warm the earth's 
climate by the ``greenhouse effect'' \1\ in which CO2 
absorbs infrared radiation and then re-radiates it back toward the 
surface of the planet. Other gases also act as greenhouse gases and may 
warm the climate even further,\2\ although human-produced airborne 
sulfate particles can cause cooling that offsets some of the 
warming.\3\ Computational models that include these factors predict 
that the climate will warm significantly over the next century.
---------------------------------------------------------------------------
    \1\ The greenhouse effect for CO2 was first calculated 
over 100 years ago by S. Arrhenius, The London, Edinburgh and Dublin 
Philosophical Magazine and Journal of Science 41, 237 (1896).
    \2\ Intergovernmental Panel on Climate Change, Climate Change, the 
IPCC Scientific Assessment, J. T. Houghton et al., Eds. (Cambridge 
Univ. Press, Cambridge, 1990).
    \3\ Intergovernmental Panel on Climate Change, Climate Change 1995, 
The Science of Climate Change, J. T. Houghton et al., Eds. (Cambridge 
Univ. Press, Cambridge, 1996).
---------------------------------------------------------------------------
    These forecasts of likely climate changes have forced a realization 
that it is necessary to reduce human-caused emissions of greenhouse 
gases. But because of the potential social disruptions and high 
economic costs of such reductions, vigorous debate has arisen about the 
size and nature of the projected climate changes and whether they will 
actually lead to serious impacts.
    A key element of these spirited--and often acrimonious--debates is 
the credibility (or lack thereof) of the mathematically and physically 
based climate models \4\ that are used to project the climate changes 
resulting from a sustained buildup of atmospheric CO2. Some 
skeptics ask, to put it bluntly, why should we believe such models' 
attempts to describe changes in such a dauntingly complex system as 
Earth's climate? The cheap answer is that there are no credible 
alternatives. But the real answer is that the climate models do a 
reasonably good job of capturing the essence of the large-scale aspects 
of the current climate and its considerable natural variability on time 
scales ranging from 1 day to decades.\4\ In spite of these considerable 
successes, the models contain weaknesses that add important uncertainty 
to the very best model projections of human-induced climate changes.
---------------------------------------------------------------------------
    \4\ Climate models are mathematically based models that attempt to 
calculate the climate, its variability, and its systematic changes on a 
first-principles basis. The fundamental equations solved are the 
conservation of mass, momentum, and energy. The interactions among the 
atmosphere, ocean, ice, and land surface systems are calculated on 
rather widely separated computational points on Earth (typical spacings 
are 200 to 400 km in the horizontal and 1 to 3 km in the vertical).
---------------------------------------------------------------------------
    I express here a ``policy-independent'' evaluation of the levels of 
current scientific confidence in predictions emanating from climate 
models. This climate model uncertainty is distinct from the high social 
uncertainty associated with future scenarios of greenhouse gas and 
airborne particle concentrations. I assume that detailed future 
greenhouse and airborne particle scenarios are part of the policy 
question and thus do not discuss them further.
    A fair-minded and exhaustive attempt to find a broad consensus on 
what science can say about this problem is contained in the most recent 
1996 IPCC Working Group I Assessment.\3\ Some of my evaluations differ 
in detail from those of IPCC 1996, mostly because of the addition of 
new research insights and information since 1994. A good guideline for 
evaluating contrary ``expert'' opinions is whether they use the IPCC 
science as a point of departure for their own analysis. In effect, if 
we disagree scientifically with IPCC, we should explain why. Without 
such discipline, contrary arguments are not likely to be scientifically 
sound.

Virtually Certain ``Facts''
    These key aspects of our knowledge of the climate system do not 
depend directly on the skill of climate model simulations and 
projections:

   Atmospheric abundances of greenhouse gases are increasing 
        because of human activities.

   Greenhouse gases absorb and re-radiate infrared radiation 
        efficiently. This property acts directly to heat the planet.

   Altered amounts of greenhouse gases affect the climate for 
        many centuries. The major greenhouse gases remain in the 
        atmosphere for periods ranging from a decade to centuries. 
        Also, the climate itself has considerable inertia, mainly 
        because of the high heat capacity of the world ocean.

   Changes in other radiatively active substances offset 
        somewhat the warming effect of increased greenhouse gases. 
        Observed decreases in lower stratospheric ozone and increases 
        in sulfate particles both produce cooling effects. The cooling 
        effect of sulfate particles remains insufficiently quantified.

   Human-caused CO2 increases and ozone decreases in 
        the stratosphere have already produced more than a 1+C global 
        average cooling there. This stratospheric cooling is generally 
        consistent with model predictions.

   Over the past century, Earth's surface has warmed by about 
        0.5+C (0.2+C).

   The natural variability of climate adds confusion to the 
        effort to diagnose human-induced climate changes. Apparent 
        long-term trends can be artificially amplified or damped by the 
        contaminating effects of undiagnosed natural variations.

   Significant reduction of key uncertainties will require a 
        decade or more. The uncertainties concerning the responses of 
        clouds, water vapor, ice, ocean currents, and specific regions 
        to increased greenhouse gases remain formidable.

    I further illustrate these climate uncertainties using two 
extrapolations of the IPCC idealized scenarios of increases of 1% 
equivalent atmospheric CO2 concentration per year.\5\ The 
first case levels off at a CO2 doubling after 70 years; the 
second levels off at a CO2 quadrupling after 140 years. Both 
correspond to simple extrapolations of current trends in greenhouse gas 
emissions. Considering the long residence time of CO2 at 
such large concentrations, these leveled-off scenarios are physically 
plausible but are presented as illustrations, not as social 
predictions.
---------------------------------------------------------------------------
    \5\ S. Manabe and R. J. Stouffer, Nature 364, 215 (1993); J. Clim. 
7, 5 (1994).
---------------------------------------------------------------------------
Virtually Certain Projections
    These projections have a greater than 99 out of 100 chance of being 
true within the predicted range: \6\
---------------------------------------------------------------------------
    \6\ The approach used here was tested and challenged in E. Barron, 
Forum on Global Change Modeling, U.S. Global Change Research Program 
Report 95-02 (U.S. Global Change Research Program, Washington, DC, 
1995). Earlier evaluations were published in J. D. Mahlman, Climate 
Change and Energy Policy, L. Rosen and R. Glasser, Eds. (American 
Institute of Physics, Los Alamos National Laboratory LA-UR-92-502, New 
York, 1992) and in J. D. Mahlman, U.S. Congressional Record, 16 
November 1995, House Science Committee Hearing on Climate Models and 
Projections of Potential Impacts on Global Climate Change (1995).

   The stratosphere will continue to cool significantly as 
        CO2 increases. If ozone continues to decrease, the 
        cooling will be magnified. There is no known mechanism to 
        prevent the global mean cooling of the stratosphere under these 
---------------------------------------------------------------------------
        scenarios.

   Global mean amounts of water vapor will increase in the 
        lower troposphere (0 to 3 km) in approximately exponential 
        proportion (roughly 6% per 1+C of warming) to the global mean 
        temperature change. The typical relative humidities would 
        probably change substantially less, in percentage terms, than 
        would water vapor concentrations.

Very Probable Projections
    These projections have a greater than 9 out of 10 chance of being 
true within the predicted range:

   The global warming observed over the past century is 
        generally consistent with a posteriori model projections of 
        expected greenhouse warming, if a reasonable sulfate particle 
        offset is included. It is difficult, but not impossible, to 
        construct conceivable alternate hypotheses to explain this 
        observed warming. Using variations in solar output or in 
        natural climate to explain the observed warming can be 
        appealing, but both have serious logical inconsistencies.

   A doubling of atmospheric CO2 over preindustrial 
        levels is projected to lead to an equilibrium global warming in 
        the range of 1.5+ to 4.5+C. These generous uncertainty brackets 
        reflect remaining limitations in modeling the radiative 
        feedbacks of clouds, details of the changed amounts of water 
        vapor in the upper troposphere (5 to 10 km), and responses of 
        sea ice. In effect, this means that there is roughly a 10% 
        chance that the actual equilibrium warming caused by doubled 
        atmospheric CO2 levels could be lower than 1.5+C or 
        higher than 4.5+C. For the answer to lie outside these bounds, 
        we would have to discover a substantial surprise beyond our 
        current understanding.

   Essentially all climate models predict equilibrium global 
        temperature increases that are nearly linear in the logarithm 
        of CO2 changes. This effect is mainly due to 
        increasing saturation of many of the infrared absorption bands 
        of CO2. That is, a quadrupling of CO2 
        levels generally produces projected warmings that are about 
        twice as large as those for doubled CO2.

   Models predict that by the year 2100, global mean surface 
        temperature changes under these two idealized scenarios would 
        be 1.5+ to 5+C.

   Sea level rise could be substantial. The projections of 50 
         25 cm by the year 2100, caused mainly by the 
        thermal expansion of sea water, are below the equilibrium sea 
        level rise that would ultimately be expected. After 500 years 
        at quadrupled CO2 levels, the sea level rise 
        expected due to thermal expansion alone is roughly 2 
         1 m. Long-term melting of landlocked ice carries 
        the potential for considerably higher values but with less 
        certainty.

   As the climate warms, the rate of evaporation must increase, 
        leading to an increase in global mean precipitation of about 2 
         0.5% per 1+C of global warming.

   By 2050 or so, the higher latitudes of the Northern 
        Hemisphere are also expected to experience temperature 
        increases well in excess of the global average increase. In 
        addition, substantial reductions of northern sea ice are 
        expected. Precipitation is expected to increase significantly 
        in higher northern latitudes. This effect mainly occurs because 
        of the higher moisture content of the warmer air as it moves 
        poleward, cools, and releases its moisture.

Probable Projections
    The following have a greater than two out of three chance of being 
true:

   Model studies project eventual marked decreases in soil 
        moisture in response to increases in summer temperatures over 
        northern mid-latitude continents. This result remains somewhat 
        sensitive to the details of predicted spring and summer 
        precipitation, as well as to model assumptions about land 
        surface processes and the offsetting effects of airborne 
        sulfate particles in those regions.

   Climate models imply that the circum-Antarctic ocean region 
        is substantially resistant to warming, and thus little change 
        in sea-ice cover is predicted to occur there, at least over the 
        next century or two.

   The projected precipitation increases at higher latitudes 
        act to reduce the ocean's salinity and thus its density. This 
        effect inhibits the tendency of the water to sink, thus 
        suppressing the overturning circulation.

   Very recent research \7\ suggests that tropical storms, once 
        formed, might tend to become more intense in the warmer ocean, 
        at least in circumstances where weather and geographical (for 
        example, no landfall) conditions permit.
---------------------------------------------------------------------------
    \7\ T. R. Knutson, R. E. Tuleya, Y. Kurihara, in preparation.

   Model studies project that the standard deviations of the 
        natural temperature fluctuations of the climate system would 
        not change significantly. This indicates an increased 
        probability of warm weather events and a decreased probability 
        of cold events, simply because of the higher mean temperature.

Incorrect Projections and Policy Implications
    There are a number of statements in informal writings that are not 
supported by climate science or projections with high-quality climate 
models. Some of these statements may appear to be physically plausible, 
but the evidence for their validity is weak, and some are just wrong.
    There are assertions that the number of tropical storms, 
hurricanes, and typhoons per year will increase. That is possible, but 
there appears to be no credible evidence to substantiate such 
assertions.
    Assertions that winds in midlatitude (versus tropical) cyclones 
will become more intense do not appear to have credible scientific 
support. It is theoretically plausible that smaller-scale storms such 
as thunderstorms or squall lines could become stronger under locally 
favorable conditions, but the direct evidence remains weak.
    There is a large demand for specific climate change predictions at 
the regional and local scales where life and life support systems are 
actually affected. Unfortunately, our confidence in predictions on 
these smaller scales will likely remain relatively low. Much greater 
fidelity of calculated local climate impacts will require large 
improvements in computational power and in the physical and biological 
sophistication of the models. For example, the large uncertainty in 
modeling the all-important responses of clouds could become even harder 
at regional and local levels. Major sustained efforts will be required 
to reduce these uncertainties substantially.
    Characterizations of the state of the science of greenhouse warming 
are often warped in differing ways by people or groups with widely 
varying sociopolitical agendas and biases. This is unfortunate because 
such distortions grossly exaggerate the public's sense of controversy 
about the value of the scientific knowledge base as guidance for the 
policy deliberation process.
    It is clear that much is known about the climate system and about 
how that knowledge is expressed through the use of physically based 
coupled models of the atmosphere, ocean, ice, and land surface systems. 
This knowledge makes it obvious that human-caused greenhouse warming is 
not a problem that can rationally be dismissed or ignored. However, the 
remaining uncertainties in modeling important aspects of the problem 
make it evident that we cannot yet produce a sharp picture of how the 
warmed climate will proceed, either globally or locally.
    None of these recognized uncertainties can make the problem go 
away. It is virtually certain that human-caused greenhouse warming is 
going to continue to unfold, slowly but inexorably, for a long time 
into the future. The severity of the impacts can be modest or large, 
depending on how some of the remaining key uncertainties are resolved 
through the eventual changes in the real climate system, and on our 
success in reducing emissions of long-lived greenhouse gases.

                                 ______
                                 
    Response to Written Questions Submitted by Hon. John McCain to 
                          Dr. John R. Christy

Question 1. You mentioned in your statement that 60 percent of the 
atmospheric mass that was projected by computer models to warm 
significantly has not. How significant is this 60 percent? Are you 
saying that the claims of global warming are based on less than half of 
the affected mass?

Answer. To the layman, global warming is something that happens at the 
surface of the Earth, i.e. the surface temperature. Much has been made 
about the fact the surface temperature has increased in the past 21 
years. At the same time, the bulk of the atmosphere, from the surface 
to 5 miles up, has experienced little change in that time. The 
significance here is that all climate models show that with enhanced 
greenhouse gasses, the surface temperature will rise and that the 
deeper layer will rise even more. The fact this bulk-layer has not 
risen indicates that the surface warming of the past 21 years is not 
human-induced warming (if models are correct) or that the climate 
system is not well-represented in the present models. I believe there 
are significant shortcomings in the present models with regard to 
distributing heat throughout the bulk of the atmosphere, and that this 
may lead to predictions of surface warming that are too high.

Question 2. Your written statement has suggested that no model is 
perfect because the weather system is incredibly complex. Furthermore, 
you stated that the goal of models is to provide information on changes 
in large-scale features. Given the increases in computing power, can we 
ever expect to have models provide information on smaller scale 
features?

Answer. I do not see, with either improved computing power or with 
improved models, the ability to predict with confidence what the 
climate will be in specific regions. At this point we are unable to do 
so for the next ten days, much less for the next ten years or next ten 
decades. Since local precipitation is more critical than temperature 
for human and other biological systems, predictions of changes in 
rainfall would be of great value if we could have confidence in them. 
However, the present set of climate models predicts a range of 
precipitation changes in any given region so wide (e.g. much more, 
more, same, less, much less) as to be of no use for policy decisions. 
Thus, establishing regulations that increase the cost of energy to 
people (with a greater impact on poorer people) will be done so to deal 
with a ``global average,'' for which the local impacts are essentially 
unpredictable. Even so, reductions in CO2 through regulation 
will be so tiny as to have microscopic effect on the global average 
temperature. A global economic depression (with associated loss of 
living standards, health, security etc.) would most likely do more to 
reduce CO2 increases than regulation. Even this would have 
relatively no impact on the path of the present global average climate.

Question 3. Your written testimony referred to a recent report which 
stated that January through March of this year was the hottest ever 
recorded. The satellite data showed that the atmospheric temperature 
above the U.S. mainland was indeed higher than average. However, most 
of the globe experienced lower than average temperatures. Does this 
suggest that what we may be experiencing is not global warming, but a 
shifting of the temperature patterns?

Answer. The key point here is that the news media broadcast widely the 
report of ``warmest ever'' surface temperatures over the lower-48 
states. This was then linked as evidence to human-induced global 
warming. The global picture, however, indicated the warm temperatures 
over the U.S. were only part of a typical weather pattern that has 
alternating regions of warm and cold. The U.S. was in a very warm spot, 
but most regions experienced cooler than average tropospheric 
temperatures (see map in written testimony). Thus, the lower-48 (2 
percent of the globe) was not representative of global temperatures, 
and the global temperatures were not showing global warmth.

Question 4. Your written statement acknowledged that in the past 100 
years, sea level has risen 6 inches (plus or minus 4 inches) and is not 
accelerating. You further stated that for the Gulf Coast, a rise of 6 
inches over 100 years is minuscule. Can you elaborate on how minuscule 
this impact would be?

Answer. For this question, we actually have a good source of 
information--the real world. The sea level has risen 6 inches in the 
past 100 years, and the ecosystems along the Gulf Coast have not 
changed appreciably because of it. When sea level rises less than an 
inch per decade, ecosystems can naturally adapt. It is important to 
note that relative sea level is always changing as natural geologic 
forces uplift some coasts and subsidence lowers other coasts. At the 
sea level rates we are discussing for the global average, the change in 
the volume of water in the ocean is often a smaller effect than the 
other natural forces for a given location.
    The stresses these coastal ecosystems do endure come not from sea 
level rise, but from human development and human-generated pollutants 
in river runoff. And, these developments are more and more in harms way 
of the next hurricane which could have a storm surge (i.e. sudden sea 
level rise) of 10 to 30 feet. This is the real danger for coastal 
dwellers and economic infrastructure. Natural ecosystems have ways to 
bounce back from hurricanes, but buildings and roads don't. What I tell 
developers and other potential beach front property owners is ``If a 6 
inch rise in sea level is a problem for you, you are too close to the 
water.''

                                 ______
                                 
    Response to Written Questions Submitted by Hon. John McCain to 
                             Dr. Neal Lane

Question 1. Are there any areas within climate change research which 
you would characterize as deficient? Is the federal government making 
the right choices regarding which programs it should fund?

Answer. Our current understanding of climate change is the result of 
significant successes in research over the last several decades, and, 
as is often the case in science, that success has led to many new 
questions. I would not characterize any aspect of our current climate 
research effort as deficient, but it is certainly true that we need to 
modify and enhance various aspects of our research effort in response 
to new developments in science and new needs for information. As noted 
in my testimony, the climate change debate has evolved from ``Are we 
warming the Earth?'' to How much are we warming the Earth? and ``What 
impacts will that warming have?'' The U.S. Global Change Research 
Program (USGCRP) is benefiting from the advice in a number of recent 
National Research Council reports, including, ``Global Environmental 
Change: Research Pathways for the Next Decade'' as it addresses these 
questions. A number of priorities have emerged from USGCRP 
consideration of recommendations from the NRC and from other scientific 
advisory bodies. The program is enhancing its efforts and revising its 
strategies in a number of key areas, including carbon cycle research, 
water cycle research, research on the impacts of climate change, long-
term climate observations, and high-end climate modeling.
    The USGCRP established a Carbon Cycle Science initiative in the 
FY2000 budget, focused on improving our understanding of carbon 
dynamics in the environment, and we have continued strong support for 
this in the FY2001 budget request. The FY2001 request also proposes 
increases for water cycle research, long-term surface based climate 
observations, and research to understand the ecological impacts of 
climate change and other global changes. All of these topics will be 
important areas in the new overall long-term research strategy that is 
now being developed. We anticipate that a plan will be ready for review 
later this year. My view is that the federal government is making the 
right choices and that the programs we support are necessarily evolving 
and changing as we learn more about the problems and phenomena we are 
attempting to understand.

Question 2. Do you believe that the upcoming IPCC report will alter the 
current debate among scientists or Congress? Will the report confirm 
what we already believe to be true?

Answer. The Intergovernmental Panel on Climate Change (IPCC) produces a 
comprehensive assessment of global climate change approximately every 
five years. I do not think the work of the IPCC really alters or 
changes the views of the scientific community on climate change. It is 
more accurate to say that it describes these views, because the 
scientific community produces IPCC reports. This is one of the reasons 
they are so valuable. The process of creating IPCC assessment reports 
certainly influences scientific debate and discussion over many aspects 
of climate change, but I think it is important to note that the current 
scientific debate on climate change is not over whether climate change 
is occurring. It is rather over detailed projection of how much change 
will occur, exactly how much of this change is due to various forcing 
factors, and precisely what impacts change will have.
    The upcoming Third Assessment Report, which is currently under 
government and technical review, will be completed in early 2001. I 
expect this report to confirm and reinforce the broad scientific 
consensus that atmospheric CO2 has been significantly 
increased by human activities, that the surface of the earth is 
warming, and that the earth's surface temperature will continue to rise 
during the next century. It will document the increase in understanding 
that has occurred since the SAR was completed in 1995, and I believe it 
will also confirm the assertion in my testimony that the research and 
policy communities can now appropriately shift from a primary focus on 
the physical systems of climate change to a broader effort to 
understand how global change will affect the Earth's biological systems 
and the human societies that are dependent on them.

Question 3. Do you believe that the U.S. Global Change Research Program 
is achieving its full potential? What are the weaknesses of this multi-
agency program? Are they currently being addressed?

Answer. The USGCRP has been and is a successful program that can serve 
as a model for broad multi-agency cooperation in addressing a 
crosscutting research theme. Coordinating a complex research agenda 
across a dozen diverse agencies of the federal government is difficult, 
and it is critical that the Program evolves in response to changing 
research priorities. With input from the NRC and the participating 
federal agencies, a new long-term strategic research plan is being 
developed for the Program.

Question 4. What are our national objectives for the modeling program?

Answer. Most global climate modeling research and application in the 
United States is sponsored by NSF, DOE, NASA, and NOAA. These agencies 
each have their own individual planning processes, but they have also 
worked together to establish well-defined priorities consistent with 
goals and objectives of the USGCRP.
    As noted in numerous versions of ``Our Changing Planet,'' the 
USGCRP modeling strategy calls for the use of the most powerful 
supercomputers to accommodate evolutionary development and revision of 
the climate models. An interagency group has established the Common 
Infrastructure Initiative and has made progress in development of a 
flexible national modeling infrastructure that will facilitate the 
exchange of scientific advances and technology between climate modeling 
and research and operational weather modeling groups. A USGCRP 
Integrated Modeling and Prediction Working Group formally coordinates 
the agencies' climate modeling research. This Working Group, which 
reports to the SGCR, has reviewed and endorsed the various plans for 
climate modeling activities and, in particular, the proposal for the 
Climate Simulation Laboratory at the National Center for Atmospheric 
Research (NCAR). In addition, the Advisory Board for the NSF-sponsored 
Climate System Model at NCAR has been reconstituted to include 
scientists and managers from DOE, NASA, and NOAA to reflect their 
growing participation in the nation's only community climate model.
    Two specific efforts are underway to develop a national strategy 
for climate modeling, one by the National Research Council, and one by 
the agencies. These are complementary efforts with overlapping 
membership. Both are responsive to the recent Modeling report produced 
by the National Research Council that identified problems in high-end 
U.S. climate modeling capabilities. An important aspect of the USGCRP 
agency effort is to determine how the climate modeling community should 
focus its efforts and investments to best leverage the new capabilities 
that will be developed through the Administration's Information 
Technology Research (ITR) initiative to create more advanced 
supercomputers and software.
    Finally, an implicit requirement for an effective modeling program 
is a robust observation system that can provide consistent, long-term 
data on the many parameters of the climate system. Thus, a diverse 
approach that supports modeling, observations, research and analysis, 
and assessment is needed. Each of these activities relies upon and 
informs the others.

Question 5. What are some of the lessons learned from the first 
National Assessment?

Answer. The ``U.S. National Assessment of the Potential Consequences of 
Climate Variability and Change'' is now nearing completion. We have 
learned a number of lessons related to process, research needs, and 
potential impacts. Related to process, I want to be on record in 
expressing sincere appreciation for the overwhelming support received 
in this effort. Stakeholders were very forthcoming in sharing their 
insights and concerns, which were critical in providing direction. 
Individuals from academia, industry, and non-governmental organizations 
demonstrated exceptional willingness to serve by volunteering their 
time to be chapter authors, technical reviewers, and advisors to the 
process.
    In terms of research needs, work on the Assessment revealed a 
number of key priorities for further work. It became clear that we need 
more basic knowledge about how natural ecosystems and managed 
ecosystems such as agriculture and managed forests will respond to 
changes in climate and in atmospheric CO2 concentration. 
Since many of the resources and ecosystems that will be affected by 
climate change, such as water and forests, are intensely managed, it is 
crucial that we understand better how present and potential future 
management practices could either compound or mitigate the effects of 
climate change and other environmental stresses. Finally, since the 
degree of impacts will inevitably depend on the actual rate and 
character of climate change, it is important to continue working to 
reduce uncertainties in our knowledge and projections of climate. This 
will require further improvement in climate models and our 
understanding of past climate variation, further development of methods 
to refine regional-scale projections, and crucially, better 
understanding of the socioeconomic drivers of potential climate change, 
such as population, demographics, income levels, and energy use 
patterns.

Question 6. The National Research Council report entitled ``Global 
Environmental Change: Research Pathways for the Next Decade'' stated 
that the USGCRP must be revitalized, focusing its use of funds more 
effectively on the principally unanswered scientific questions about 
global environmental change. What has been the USGCRP reaction to this 
point?

Answer. As noted in my testimony and in the answer to question 1, the 
USGCRP relies on input from both participating federal agencies and the 
broader scientific community to set research priorities and devise 
appropriate strategies for addressing critical issues. With guidance 
from the ``Pathways'' report, USGCRP research has been organized into a 
set of ``program elements,'' including a Carbon Cycle Science 
initiative established in FY2000, and a Global Water Cycle initiative 
included in the FY2001 budget request:

   Understanding the Earth's Climate System

   Biology and Biogeochemistry of Ecosystems

   Composition and Chemistry of the Atmosphere

   Paleoenvironment/Paleoclimate

   Human Dimensions of Global Change

   Carbon Cycle Science

   The Global Water Cycle

    The ``Pathways'' report is also a basis for current efforts to 
develop a new 10-year strategic plan for the USGCRP.

Question 7. Can you summarize how USGCRP has been meeting the 
requirements of Section 104 of the Global Change Research Act of 1990 
(P.L. 101-606)?

Answer. The creation of a comprehensive research plan was one of the 
most important early tasks of the USGCRP. The 1991 edition of Our 
Changing Planet had two volumes, one of which was titled Our Changing 
Planet. The FY1991 Research Plan. This 250-page document was a detailed 
and comprehensive scientific strategy for the USGCRP. The ongoing 
consideration and revision of the plans set forth in this document has 
been an important topic for the USGCRP agencies as they engage in their 
yearly program planning and budget processes, and updates to these 
plans have been included in the subsequent editions of Our Changing 
Planet.
    The progress that has been made in many areas of global change 
science, and the advice received in a number of major studies from the 
National Academy of Sciences, including the Pathways report, has 
resulted in a major effort to define a new long-term strategy for the 
USGCRP. This process has been underway for several years, and we 
anticipate that a draft will be submitted for public comment and NRC 
review later this fall. The draft will cover all the areas outlined in 
Section 104 of the U.S. Global Change Research Act.

Question 8. Given that USGCRP is ten years old, do you believe it's an 
appropriate time for a new ten-year plan?

Answer. Absolutely. The process of review and program improvement is 
continuous. The next important step in this process will be the 
completion of a new long-term plan later this year. This plan will be 
submitted to the National Research Council for review. The NRC 
Committee on Global Change Research, the follow-on committee to the 
``Pathways'' report, is working with the USGCRP agencies to construct a 
reasonable schedule for review of progress in responding to the 
recommendations of the Pathways report and the new long-term plan.

                                 ______
                                 
    Response to Written Questions Submitted by Hon. John McCain to 
                           Dr. Jerry Mahlman

Question 1. You mentioned in your statement that important 
uncertainties remain due to deficiencies in our scientific 
understanding and in computer power. Can you explain how an increase in 
computing power will enable you to reduce some of the uncertainty in 
your models?

Answer. Increases in computer power and increases in ability to process 
very large volumes of data play an important role in reducing the 
scientific uncertainty in understanding human-caused climate warming.
    First, increased computational power allows the climate models to 
resolve regional details far better. For example, today's long-running 
atmosphere-ocean-climate models represent the entire state of Arizona 
with one or two computational points. A factor of 10 increase in 
computer power allows Arizona and its complex topography and climate 
zones to have 20 or so points.
    Second, it has been found advantageous to increase understanding of 
computer model experiments by running multiple versions, each under 
somewhat different circumstances. This allows a clearer view of what we 
do and do not understand well.
    Third, much of the remaining scientific uncertainty in this problem 
arises from incomplete information about key physical processes, such 
as clouds, turbulence, severe storms, complex land-surface biosphere/
climate interactions, etc. Greater computational power allows inclusion 
of considerably more complete physical processes and their possible 
roles in either decreasing or increasing our best estimates as to how 
much or how soon significant warming will occur, and how specific 
regions will be affected.
    Fourth, greater computational power allows the major national 
climate modeling centers to interact more productively with colleagues 
in government, academia, and private industry, simply because more 
experiments can be run at greater fidelity, with more talented 
scientists evaluating the results from a wider range of perspectives.

Question 2. You mentioned that climate modeling efforts must receive 
resources that are in balance with broader scientific programs. What 
are your current funding levels and what level would you recommend?

Answer. The current total funding for NOAA's Geophysical Fluid Dynamics 
Laboratory (GFDL) is about $22M in Fiscal Year 2000, of which $13M is 
in base funds, and most of the remainder in HPCC/IT2 interagency 
program funds. I believe it is fair to say that, thanks to a genuine 
FY2000 and 2001 commitment from Congress, OMB, and the Department of 
Commerce, GFDL's current supercomputer budget is in comparatively good 
shape. A number of our respected U.S. colleagues have not been as 
fortunate.
    For example, in NOAA it has been much easier to obtain funding for 
large hardware ventures (e.g., satellites, ground-based measurement 
systems, and supercomputers) than for funding the scientific talent 
required to achieve optimal value from these critical investments. Even 
a 5% ``tax'' on these large ``hardware'' commitments would have 
produced a very highly leveraged enhancement of these ``big ticket'' 
items. Also, the recent National Research Council's ``Pathways'' report 
has made a similar point about the under funding of NASA's research 
base necessary to optimize the value of its large satellite programs.
    In the case of my own lab, GFDL, the stresses created have been 
daunting. Over the past 15 years, GFDL's base funds for science have 
diminished by more than half in purchasing power due to unfunded 
inflationary losses, to increased administrative costs, and to 
Congressionally authorized pay raises, so conspicuously unaccompanied 
by the funds necessary to pay for them.
    In my strong opinion, this seemingly oblivious diminution of the 
federal research talent base has produced a serious reduction from the 
expected return on NOAA's and NASA's substantial investments in large 
environmental data and computing systems. Moreover, I see no evidence 
of any observable reversal of this destructive trend. In fact, the 
current budget initiative processes in place for FY2001 and 2002 appear 
to perpetuate this seemingly oblivious shortfall in the return from our 
big ticket ``hardware'' investments, including supercomputers.
    Many of us in the scientific community find it inexplicably 
baffling that something so obvious and so amenable to repair can remain 
so conspicuously unaddressed for so long.

Question 3. Can you discuss the validation process used to authenticate 
your models?

Answer. Let me begin by asserting that there is no such thing as a 
``validated climate model.'' We do find that the models perform very 
well for certain processes under certain circumstances. These same 
models exhibit important deficiencies under other circumstances. 
Interestingly, the same dilemma is present in the futile quest for 
``validated'' data sets. There is a surprisingly small number of the 
scientists who analyze observational data and output data from model 
experiments who are focused on sharpening our understanding by careful 
evaluation of the strengths, weaknesses, and information content of 
these ``real-world'' and model-based data sets.
    Given the above constraints, models are evaluated (not validated) 
through careful assessment of their agreement (or lack thereof) with 
carefully analyzed data sets. For example, are the model's simulated 
desert regions in the right location with the right climate and the 
right level of natural variability on time scales of years to decades? 
Are the characteristics of the modeled Arctic region, including sea 
ice, in agreement with available data? Does the model simulate credible 
El Nino and La Nina events? Are the characteristics of the moist 
subtropics, such as the southeast U.S., properly simulated? Is the 
seasonal cycle of climate correctly simulated in all of these regions? 
Generally speaking, the answers to these kinds of questions is yes. 
However, a closer look often reveals significant discrepancies between 
observations and model simulations.
    Does a correct simulation of the present guarantee that we can 
simulate future climate well, assuming that we know how carbon dioxide, 
sulfate particles, and other greenhouse gases will change in the 
future? Not necessarily. Such agreements do add confidence to our use 
of the models as a tool, but do not supply the desired guarantee.
    A very important international effort is currently underway to use 
the observed, roughly 1.3+F, warming of the global-mean surface-air 
temperature over the 20th century as a critical test of the models' 
abilities to project future climate changes. This international 
collaborative effort, which includes GFDL and the National Center for 
Atmospheric Research, is showing that the models capture the essence of 
the observed 20th century warming rather well, although the models 
differ in their details. These studies do indicate, however, that 
imperfections in the observations, in the ``exotic'' forcings operative 
in the past century (such as solar changes, and indirect effects of 
sulfate and carbon particles), and in the models themselves, still 
prohibit us from tightly constraining the levels of uncertainty in the 
model-based projections. That is why my official testimony gives a 2-6 
+F range of warming for ``business as usual'' in the middle of this 
century. In spite of this genuine uncertainty, there is still no viable 
hypothesis that makes a credible case that the global warming problem 
will be substantially less than our best current estimates.

Question 4. Why is the largest uncertainty regarding global-mean 
surface warming due to clouds? Can you explain this further.

Answer. Many aspects of calculating the key effects of global warming 
are rather simple; many of its basic features are rather well 
understood. For the past three decades, for example, the clear-sky 
trapping of outgoing heat radiation from the earth by CO2 
and other greenhouse gases are well documented, as are many aspects of 
the role of water vapor increases in amplifying this ``greenhouse'' 
trapping effect.
    As we all know, cloudy skies have a dramatic effect in suppressing 
the overnight cooling that is so evident when skies are clear. Clouds 
thus absorb outgoing heat radiation and radiate energy back to the 
earth's surface, producing a warming effect. They also reflect incoming 
radiation from the sun, producing a cooling effect. Increasing clouds 
near the ground produce a net cooling effect on the climate, while 
increasing clouds at 6 miles altitude tend to warm the climate.
    Each of these separate cloud effects are difficult to calculate 
with accuracy. The combined effects in the context of climate change 
tend to be small differences between large opposing effects, of which 
all carry significant uncertainty. Moreover, the effects vary 
differently in different geographic regions, and all of these effects 
depend upon the details of very small-scale phenomena on the scale of 
the water droplets and/or ice crystals in the clouds. Furthermore, 
satellite-based measurements do not neatly diagnose the net role of 
clouds very well, even in today's climate.
    Thus, clouds have legitimately earned their place as the leading 
source of the uncertainty in our projections of climate change.

Question 5. What is your current accuracy rate of climate models for 
projecting tropical storms, earthquakes, and floods? How has your 
understanding of global warming changed your models?

Answer. I am rather confident, better than 2 out of 3, that hurricanes 
and similar tropical storms, once formed, will tend to have stronger 
winds and considerably greater rainfall as the climate and the oceans 
continue to warm. The warmer and moister atmosphere and the warmer 
ocean below, simply put, makes the potential energy of a hurricane 
significantly stronger. Today, those hurricanes that stay over warm 
water for sufficient time do tend to approach their maximum potential 
power. We expect that to be also true in the future, only at higher 
intensities. Some have argued that we also should expect more 
hurricanes in the future warmer earth. That may be so, but I see no 
convincing scientific evidence that says that. For now, we simply do 
not know.
    All models of which I am aware do tend to produce more floods- in 
those regions where floods already tend to be prevalent today. At the 
simplest level, this effect is mainly due to the expected higher water 
vapor amounts in the atmosphere due to increased evaporation efficiency 
over the warmer oceans. In effect, wet weather systems become even 
wetter because the atmosphere will carry more water. Conversely, 
drought prone regions, such as the southwest U.S., are likely to be 
even drier due to increased evaporation of soil moisture in the warmer 
climate.
    Earthquakes have no known or suspected connection to a warming 
climate. Even speculated effects would be expected to be very weak.
    Our models have evolved significantly in response to improvements 
in our understanding of very complex phenomena. For example, the 
mathematical modeling of clouds has become significantly more 
sophisticated in the treatment of radiative, convective, and cloud 
microphysical processes. Unfortunately, these improvements have yet to 
produce dramatic breakthroughs in this dauntingly difficult problem. 
However, the problem is now being attacked with increasingly focused 
tools from specialized observations, better theories, and models more 
firmly rooted in fundamentals of atmospheric physics and dynamics.

Question 6. You stated in your testimony that you are ``virtually 
certain'' that increasing greenhouse gases are due to human activities. 
What erased the doubt in your mind?

Answer. Actually, there has not been much doubt about this in the 
scientific community for over a decade. For the dominant greenhouse 
gas, carbon dioxide, we can directly calculate the changes in 
atmospheric fossil fuel carbon from year to year by measuring the 
amount of the isotope, carbon-14. This isotope is produced in the 
atmosphere by bombardment from high energy solar cosmic rays. Once 
created in the atmosphere, carbon-14 decays with a half life of about 
5500 years. Because of this, fossil carbon in the form of coal, oil, 
and natural gas that has been buried for a hundred million years is 
devoid of the carbon-14 isotope. As more fossil carbon is injected into 
the atmosphere, the carbon-14 isotope has become progressively more 
deficient relative to the non-radioactive carbon-12 form.
    Thus, we are not debating whether humans have substantially 
modified the carbon dioxide amounts in the atmosphere. They have. The 
real science issue is focused on how much climate change will occur. 
Beyond the science, people are concerned about who or what would be the 
most impacted, and who will ``pay'' the near-term costs of mitigating 
carbon dioxide emissions, or the delayed costs of dealing with the 
impacts of climate change upon essentially all life forms on earth.

                                 ______
                                 
    Response to Written Questions Submitted by Hon. John McCain to 
                         Dr. Kevin E. Trenberth

Question 1. The national Research Council's report mentioned a 
substantial disparity between satellite data and surface temperature 
trends. Can you summarize the extent of the disparity?

Answer. Over the 20 years 1979 to 1998, the linear temperature trend 
for the surface is estimated to be 0.25 to 0.4+C in contrast to 0.0 to 
0.2+C for the satellite data. While uncertainty exists in the exact 
trend number at about the 0.1+C/decade level (owing to how the spatial 
coverage of data is handled, how global averages are computed, 
treatment of missing data, begin and end points, etc.), the difference 
is large enough that it is significant. It was labeled a ``disparity'' 
by the report as opposed to a ``discrepancy'' as the latter implies 
something amiss, whereas the report assesses that it is likely mostly 
real and arises because the two measurements are of different physical 
quantities.

Question 2. The National Research Council report noted that at the 
outset none of the temperature measurements systems were specifically 
designed for long-term climate monitoring. Can you discuss the design 
life for these instruments and how it compares to the actual life? 
Also, what are the implications of this extended use on the accuracy of 
the measurements?

Answer. At the surface, measurements are made with individual 
thermometers at many sites around the world. As well as calibration of 
the thermometers, the siting and exposure to the atmosphere must be 
standardized and should not change in time if climate trends are to be 
correctly monitored. Changing thermometers is not an issue, as they are 
quite accurate. Of more concern are changes in the way and time of day 
they are read, and changes in exposure (such as trees or buildings 
changing nearby, or building a city around the site; this latter point 
is the ``urban heat island effect''). Movements of sites for 
convenience, such as from city sites to the airport, are a substantial 
problem and this and other changes in practice, can be overcome as long 
as parallel measurements are maintained for at least a year, but often 
this has not been done.
    For the atmosphere above the surface, radiosonde packages of 
instruments are used. The package is flown on a balloon and is regarded 
as expendable and only used once. As a result the package must be as 
inexpensive as possible, which has led to compromises in quality. 
Changes to new improved technology can appear as a spurious change in 
climate unless such changes are measured and adjusted for. Mostly this 
has not been the case.
    For satellites and their platform of instruments, the typical 
design life is about 4 or 5 years. Problems arise with occasional loss 
of a satellite upon launch or premature failure of one or more 
instrument components. As the design for the NOAA series of satellites 
is to have two satellites in orbit at all times (one in the morning and 
one in the afternoon), there is some overlap expected from one 
satellite to the next. There have been times, however, notably in 1985 
and 1986 when NOAA-9 was the only satellite flying, that the overlap at 
both ends was too short to reliably splice the record from one 
satellite to the next. Normally this is done by matching records 
between overlapping satellites. The difficulty of doing this is 
compounded by the fact that the orbits of the satellites are not 
stable. Instead they tend to drift, both through orbital decay and in 
local crossing time. This latter effect means that measurements are 
made at slightly different times each day. For instance, NOAA-11 
drifted from an equator crossing time of 2 p.m. to after 5 p.m. from 
1989 to 1994. The difference in temperature between these times of day 
is considerable and appears as a climate change over time unless 
corrected for. Corrections are indeed made for this but they are likely 
to be imperfect and leave residual effects that may be significant over 
land where the diurnal temperature changes are large. Orbital decay 
also has effects by altering the geometry of any measurements that are 
not directed in the vertical (which is most of them), and this alters 
the interpretation of the measurements, which is recently being allowed 
for. On-board calibration of the instrument itself helps to minimize 
effects of instrumental drift and changes in exposure of the instrument 
to the sun as the orbit changes and with time of year, which otherwise 
would also be considerable. Attempting to allow for such effects has 
been fully tried only recently but the adjustments are empirical, so 
again residual errors are probable, although these are believed to be 
small.

Question 3. Dr John Wallace, who served as Chairman of the National 
Research Council's Panel on Reconciling Temperature Observations, is 
quoted as saying that ``There really is a difference between 
temperatures at the two levels that we don't fully understand.'' Do you 
agree with that statement and, if so, can you comment on the level that 
we don't understand?

Answer. I agree with the statement, although I also think it does 
warrant clarification. We have hypotheses about the nature of the 
differences but proving them or narrowing the possibilities down is 
difficult. Firstly, there are many differing influences on the 
temperatures at different levels in the atmosphere. At the surface it 
matters a great deal whether the surface is land or ocean, and over 
land whether the surface is wet or dry and how much vegetation is 
present. These influences are much less further aloft. Direct radiative 
heating within the atmosphere matters a great deal in the troposphere, 
and so it is important to known the spatial distribution and vertical 
profiles of greenhouse gases (water vapor, carbon dioxide, methane, 
etc., and especially ozone), aerosols and clouds. The radiative 
properties of the aerosols (how absorbing versus reflecting/scattering) 
are affected by the relative humidity and are poorly known and highly 
heterogenous in space and time. Similarly for clouds, the water content 
and size of droplets in clouds are needed to characterize their 
radiative effects. Secondly, the models we have that translate the 
forcings just mentioned into a vertical temperature profile also 
contain uncertainties and imperfections. Some of the processes believed 
to be important, such as convection, are either not well enough 
understood or are very difficult to model accurately because, for 
instance, of horizontal and vertical resolution of the model. Thirdly, 
there are likely to be some remnant errors in the observations that 
also add to uncertainties.
    Climate models need to be further improved (especially in how they 
handle convection and clouds), the changes in distributions of 
greenhouse gases, aerosols, and clouds, and their radiative properties 
need to be much better known to narrow the uncertainties, and further 
improvements are desirable in the observational record.

Question 4. The National Research Council report stated that increases 
in the number of small particles called aerosols often mask the 
greenhouse effect, and that stratospheric depletion contributes to 
cooling of the upper troposphere and stratosphere. How much cooling is 
taking place as a result of these aerosols?

Answer. Aerosols vary enormously in space and time because they are 
washed out of the atmosphere by rain, and so their lifetime is 
typically 5 to 10 days. This is the reason they vary so much spatially 
and they tend to be greatest in concentration near their source. The 
sources vary greatly around the world. Some aerosols (containing soot 
for instance) absorb solar radiation and produce heating, but the most 
pervasive ones in the Northern Hemisphere make up the milky white haze 
that you see from airplane windows crossing North America and these 
sulfate aerosols cause cooling by reflecting the sun's rays back to 
space. The cooling from sulfates is believe to be about -0.5 W m-2 
(plus or minus 50%) which converts to about a cooling of roughly 0.3+C 
over the past century. A bigger effect may come from the changes in 
clouds from aerosols. Aerosol particles encourage more cloud droplets 
to form, which makes a cloud brighter and more reflective. Low cloud is 
known from observations to have increased but how much of this increase 
is due to aerosols is unknown. The cooling is estimated to range from 0 
to perhaps as much as -2 W 
m-2 and so the cooling could be as much as 1.2+C. Over land 
since 1950, the maximum temperature is rising at a rate of about 0.1+C/
decade less than the minimum temperature and this has been shown to be 
mainly due to the increase in cloudiness. So there is huge uncertainty 
to this answer.
    [Please note, the numbers in this answer are in the context of the 
IPCC estimates of radiative forcing. These include 2.3 W m-2 
for the sum of the main well mixed greenhouse gases (not including 
ozone) to date and perhaps a total of about 1.5 W m-2 for 
all radiative forcings. I use a translation into a temperature change 
of 4 W m-2 (the value for doubling carbon dioxide alone) 
corresponding to 2.5+C. This total would then correspond to over 0.9+C 
increase in temperature versus 0.7+C observed; the difference being due 
to delays in the system response.]

Question 5. You mentioned in your written statement that changes in 
extremes changes in climate will be much greater than changes in the 
mean as a result of global warming and the increased amount of moisture 
in the air. Can you elaborate on the types of extremes we may be 
experiencing?

Answer. A relatively small change in the mean of any quantity can alter 
the frequency of extremes by 100% or more. By their very nature, 
extremes occur rarely, and so observationally based statistics on them 
and their changes are hard to come by. The databases to determine their 
changes are less available and the demands on accuracy are much 
greater, and so actual measured changes in extremes are often 
uncertain.
    Changes in some extremes have been documented in the United States 
and to a much lesser extent elsewhere. In the United States, 
precipitation is increasing, and most of that increase is in the 
heaviest (top 10%) rainfall rates. Extremes of daily rainfall of over 2 
inches per day have increased about 10% over the past century. (Because 
it typically rains 10% or less of the time, hourly rather than daily 
rainfall data should be used for this analysis, but are much less 
readily available). Much below normal temperatures (lowest 10%) are 
decreasing and much above normal temperatures (top 10%) are increasing 
for the U.S. (although some record high temperatures still hark from 
the 1930s in the Dust Bowl era). In general, extremes are observed to 
be increasing.
    What we expect, but have little documentation of, is that rainfall 
rates are increasing, so that when it rains, it rains harder, and there 
is thus more runoff and a greater risk of flooding. Whether flooding 
occurs or not depends on whether it is mitigated by building drainage 
ditches, levees, culverts, etc. through planning by the Corp of 
Engineers and local councils in the U.S. In many developing countries, 
however, the risk of flooding has been exacerbated by deforestation 
that greatly increases runoff. In most places, increased building in 
coastal areas and flood plains has increased vulnerability to flooding. 
It is also suspected that droughts set in more quickly through 
increased drying. Plant therefore wilt faster and droughts become more 
severe and are apt to last a bit longer with global warming. The result 
is greatly increased risk of wild fire and for ``control burn'' fires 
to get out of control. Heat waves are also more likely. The ``heat 
index,'' which combines humidity and temperature effects, is likely to 
venture into the uncomfortable range more often and over much greater 
areas.

Question 6. Figure 2 of your statement indicates a decrease in the 
average mean global temperature in the year 1940. Can you explain the 
decrease?

Answer. The global mean temperature had a peak in the early 1940s and 
there was a decline or leveling off until about the 1970s. Firstly, 
observations during World War II were less abundant than before or 
after but also occurred in new areas (like the Pacific atolls) and so 
some of the temperature peak might not be real (e.g., one can not stand 
on the deck of a ship and read a thermometer at night with a light 
during war, and so the thermometer is taken inside where it may be 
warmer.) However, a massive long-lived El Nino from 1939 to 1942 no 
doubt contributed to the warmth. Secondly, following the war there was 
great industrial development that is known to have increased the amount 
of aerosol in the atmosphere sharply, and so this contributes a cooling 
effect. Thirdly, the warming from about 1920 to 1940 was probably in 
part caused by increases in solar radiation, which leveled off in the 
1940s. Climate models run with reasonable estimates of the changes in 
aerosols and sun plus greenhouse gas increases are able to reproduce 
this feature.

Question 7. One of the recommendations of the NRC report (page 25) 
states that the scientific community should explore the possibility of 
exploiting the sophisticated protocols that are now routinely used to 
ensure the quality control and consistency of the data ingested into 
operational numerical weather prediction models, to improve the 
reliability of the data sets used to monitor global climate change.
    Would you explain this recommendation and discuss how it should be 
implemented?

Answer. During the ingestion of data into four dimensional data 
assimilation systems, extensive quality control of the observations 
occurs: 1) through comparison of observations with estimates of the 
observed values from the previous forecast, and 2) comparison with 
adjacent observations of all kinds in a consistent physical (model) 
framework. Sometimes this enables correction for some kinds of errors 
and it allows systematic errors to be estimated. The result is that a 
quality control flag can be assigned to each observation and 
information exists on whether the observation was used or rejected, and 
how accurate it appears to be. This information should be retained and 
archived. In the case of rejected or missing data, an accurate estimate 
of what the observation should have been can be made, and this estimate 
can be utilized to improve the data set. Similarly, more intelligent 
decisions can be made to quality control the whole data set and make it 
more reliable.
    My recommendation is to have the numerical weather prediction 
centers, in collaboration with climate scientists, select a subset of 
observations (in particular a subset of radiosonde observations) and 
generate an enhanced data set that includes, with the original 
observation, the quality control output and estimates of correct values 
in cases of missing or erroneous data. This could feasibly be done for 
temperature, and perhaps humidity and wind measurements during a 
reanalysis of past data. In particular, monthly summaries of estimates 
of offset bias should prove very valuable. Then independent analysis of 
the more comprehensive data set should enable more reliable trend 
estimates from the radiosondes.

                                 ______
                                 
    Response to Written Questions Submitted by Hon. John McCain to 
                             Robert Watson

Question 1. If you consider all of the peer-reviewed assessments that 
the IPCC has made over the years, have there been any distinctive 
trends in the findings? Have any of the studies contradicted each 
other?

Answer. There has clearly been a longer observational record and an 
evolution in our understanding of the Earth's climate system and the 
potential influence of human activities. Our understanding of the 
fundamental process that control the Earth's climate have clearly 
improved, although significant uncertainties still remain. This, 
improved understanding of the processes that control the Earth's 
climate system, combined with more powerful computers, has led to 
significantly more sophisticated theoretical models that include a more 
realistic simulation of land, oceanic and atmospheric processes with 
increased spatial resolution.
    There have been no major changes in the conclusions of successive 
IPCC reports. In most cases, based on new research findings, there have 
been small changes in understanding but few, if any, substantial 
changes in our fundamental understanding.
    Let me summarize how our understanding has evolved since the First 
IPCC assessment in 1990 using just a few key issues to illustrate 
trends in findings. I have focussed my answer on the climate system 
rather than on the projected impacts of climate change on human health, 
socio-economic sectors and ecological systems or the projected 
approaches to mitigate climate change:
    1. Past changes in atmospheric composition, climate and climate-
related parameters:

   atmospheric composition: the atmospheric concentrations of 
        the major greenhouse gases, i.e., carbon dioxide, methane and 
        nitrous oxide have all continued to increase. However, the 
        atmospheric concentrations of some of the chlorofluorocarbons 
        have peaked and are now decreasing because of the effectiveness 
        of the Montreal Protocol.

   temperature: global mean temperatures have continued to 
        increase with the warmest three years of the last century all 
        occurring since 1990;

   precipitation: globally, precipitation is continuing to 
        increase. However, we have now shown that the spatial and 
        temporal distribution of precipitation is changing in some 
        regions of the world, e.g., in the U.S. there is now evidence 
        of more precipitation in winter and an increase in heavy 
        precipitation events in summer.

   sea level: the latest analysis confirms earlier conclusions 
        that sea level has risen 10-25 cms over the last 100 years.

    2. Attribution of the observed changes in climate:

   in contrast to the first assessment report, the second 
        assessment report concluded that the observed changes in the 
        Earth's climate over the last 100 years could not be ascribed 
        to natural phenomena alone, and concluded that there was now a 
        discernible human influence on the Earth's climate.

    3. Projected changes in atmospheric composition, climate and 
climate-related parameters:

   atmospheric composition: the emissions scenarios work has 
        become more sophisticated, but the bottom line conclusion 
        largely remains the same, i.e., there is a wide range of 
        plausible future greenhouse gas emissions, which primarily 
        depends on population and economic growth, technological 
        advances and governance structures.

   climate sensitivity: projected changes in climate depend 
        upon projected changes in atmospheric composition (greenhouse 
        gases and aerosols) and the sensitivity of the climate models 
        to changes in atmospheric composition, i.e., the response 
        function, which we have termed the climate sensitivity factor. 
        In spite of our improved understanding of the climate system, 
        there has been no change in our estimate of the climate 
        sensitivity factor since the first assessment report, i.e., 
        global mean surface temperatures are projected to increase from 
        1.0-4.5 degrees Centigrade at equilibrium in a doubled carbon 
        dioxide world, with the best estimate being 2.5 degrees 
        Centigrade.

   aerosols: the ``cooling'' role of aerosols was not 
        recognized in the first assessment report, but was in the 
        second assessment report.

   temperature: projected changes in global mean surface 
        temperature in 2100 have varied from the first assessment 
        report until now, but well within the uncertainty range and 
        because of known factors. The business as usual best estimate 
        projection for changes in global mean surface temperature in 
        2100 was 3.0 degrees Centigrade, within a range of 2.0-5.0 
        degrees Centigrade (the business as usual greenhouse gas 
        scenario coupled with the range of climate sensitivity). In the 
        second assessment report, the business as usual best estimate 
        projection for a change in global mean surface temperature in 
        2100 was 2.0 degrees Centigrade within a range of 1.0-3.5 
        degrees Centigrade (four greenhouse gas scenarios coupled with 
        the range of climate sensitivity). If the latest IPCC emissions 
        scenarios are used in conjunction with a range of climate 
        models the projected changes in mean surface temperature in 
        2100 would be from about 1.0-5.0 degrees Centigrade (six 
        greenhouse gas scenarios coupled with the range of climate 
        sensitivity). The decrease in the business as usual best 
        estimate projection for changes in global mean surface 
        temperature in 2100 between the first and second assessment 
        report was due to lower projections of chlorofluorocarbon 
        emissions (Montreal Protocol) and carbon dioxide emissions and 
        the inclusion of sulfate aerosols in the models (sulfate 
        aerosols tend to cool the atmosphere and hence partly offset 
        the warming effect of the greenhouse gases).

   precipitation: projections of changes in precipitation have 
        consistently shown an increase in global precipitation, with 
        increases in the tropics, mid- and high-latitudes and decreases 
        in the sub-tropics. The exact changes are model dependent.

   sea level: projected changes in global mean sea level in 
        2100 have varied slightly from the first assessment report 
        until now, but well within the uncertainty range and because of 
        known factors. The business as usual best estimate projection 
        for changes in global mean sea level in 2100 was 65 cms, within 
        a range of 30-110 cms. In the second assessment report, the 
        business as usual best estimate projection for a change in 
        global mean sea level in 2100 was 50 cms within a range of 15-
        95 cms. If the latest IPCC emissions scenarios are used in 
        conjunction with a range of climate models the projected 
        changes in mean sea level in 2100 would be from about 10-90 
        cms. The changes in projected sea level occur primarily because 
        of changes in temperature projections, as well as in some cases 
        because of small changes in the glacier, ice sheet and ocean 
        models.

Question 2. You mentioned in your statement that the time to reverse 
the human-induced changes in the climate and the resulting 
environmental damages would not be years to decades but centuries to 
millennia. Is it reasonable to make any major conclusions on the future 
based upon models and data collection systems that may need further 
refinement?

Answer. Yes. While recognizing there are uncertainties associated with 
precisely quantifying changes in climate at the regional and global 
scale, and hence the associated impacts on human health, socio-economic 
sectors and ecological systems, stating that the time to reverse human-
induced changes in the climate and the resulting environmental damages 
would not be years to decades but centuries to millennia is a robust 
conclusion. The conclusion primarily rests on an understanding of the 
lifetime/adjustment time of carbon dioxide, the major anthropogenic 
greenhouse gas. The lifetime of carbon dioxide is governed by the 
exchange of carbon dioxide between the atmosphere and the deep waters 
of the oceans. Whilst there is a rapid equilibration (less than five 
years) of carbon dioxide between the atmosphere and the surface waters 
of the oceans, it takes much longer (more than a century) for carbon 
dioxide in the atmosphere to equilibrate with the deep oceans. Our 
understanding of this feature of the carbon cycle is based on models 
that have been field-tested against tracer data, e.g., the rate of 
uptake and diffusion into the deep oceans of atmospheric 
chlorofluorocarbons and radio-active carbon (formed during the atomic 
bomb tests).
    The small portion (15-25%) of human-induced changes in climate that 
can be attributed to short-lived gases, i.e., methane (a lifetime of 
about a decade) and tropospheric ozone (a lifetime of a few days) can 
be reversed much quicker. Conversely, reductions in sulfate aerosol 
precursor emissions (i.e., sulfur dioxide) would lead to a rapid 
increase in climate change because of the very short lifetime (days).

Question 3. Would you describe some of the technologies that can be 
used to mitigate climate change.

Answer. The IPCC Second Assessment Report concluded that there is a 
wide range of technologies that already exist that can be used to cost-
effectively mitigate climate change. However, before listing some of 
them it is important to note that cost-effective mitigation of climate 
change (Article 3 of the UNFCCC) will be most effective through a 
combination of changes in both the policy framework and the fuller 
utilization of a wide of technologies in energy supply, energy demand 
and the agricultural/forestry sectors. In addition it should be 
recognized that stabilization of greenhouse gas concentrations in the 
atmosphere (Article 2 of the UNFCCC) will require the development and 
market penetration of new and improved technologies, hence the need for 
increased public and private sector funding for R&D.
    All of the policy and technology options listed below are discussed 
in significant detail in IPCC assessments and Special Reports, e.g., 
technology transfer and land-use, land-use change and forestry.
    Policy Framework: It is important to get the policy framework 
correct in order to stimulate the utilization of ``climate-friendly'' 
technologies and strategies, domestically and internationally. For 
example, if there are policies that distort the market, e.g., fossil 
fuel subsidies, they both discourage the efficient use of energy and 
the penetration of modern renewable energy technologies. An appropriate 
policy framework, augmented by education and training programs, would 
combine:

   command and control, e.g., energy efficiency standards, 
        energy taxes;

   market mechanisms, e.g., domestic and international 
        emissions rights and project-based carbon offset trading; 
        removal of subsidies that increase greenhouse gas emissions; 
        incentives for the use of new technologies during market build-
        up;

   voluntary measures.

    Technologies and Strategies: There needs to be a concerted effort 
to produce and use energy more efficiently and to emit lower amounts of 
greenhouse gases, and to reduce emissions and increase the uptake of 
carbon in agricultural, forestry and rangeland systems. In addition to 
energy and land-use technologies, information technologies can be used, 
inter-alia, for the more efficient management of energy systems, 
improve the efficiency of transportation systems and decrease travel 
miles through telecommuting and teleconferencing.

   Supply side options include:

     fuel switching (coal to gas)
     increased power plant efficiency (co-generation)
     carbon dioxide sequestration (carbon dioxide separation 
            followed by long-term sequestration)
     renewable energies, e.g., wind, solar electric, solar 
            thermal, modern biomass, small-scale hydropower and 
            geothermal
     nuclear

   Demand-side options include:

     transportation (e.g., lighter vehicles, increased 
            combustion efficiency, alternate fuels (e.g., fuel cells), 
            electric vehicles, hybrid vehicles (combustion/electric)--
            land-use planning can improve the efficiency of 
            transportation systems.
     commercial and residential buildings (e.g., building 
            shells, lighting, heating and air conditioning systems, 
            computers, appliances)
     industry (e.g., processes, recycling)

   Agriculture, Forestry and Rangelands

     improved agricultural (e.g., no-till) and grazing land 
            management
     agroforestry (only a significant option in developing 
            countries)
     afforestation, reforestation, slowing deforestation and 
            improved forest management

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