[Senate Hearing 107-1027]
[From the U.S. Government Printing Office]

                                                       S. Hrg. 107-1027



                               before the

                         COMMITTEE ON COMMERCE,
                      SCIENCE, AND TRANSPORTATION
                          UNITED STATES SENATE

                      ONE HUNDRED SEVENTH CONGRESS

                             FIRST SESSION


                              MAY 1, 2001


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

                          WASHINGTON : 2004
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                      ONE HUNDRED SEVENTH CONGRESS

                             FIRST SESSION

                     JOHN McCAIN, Arizona, Chairman
TED STEVENS, Alaska                  ERNEST F. HOLLINGS, South Carolina
CONRAD BURNS, Montana                DANIEL K. INOUYE, Hawaii
TRENT LOTT, Mississippi              JOHN D. ROCKEFELLER IV, West 
KAY BAILEY HUTCHISON, Texas              Virginia
OLYMPIA J. SNOWE, Maine              JOHN F. KERRY, Massachusetts
SAM BROWNBACK, Kansas                JOHN B. BREAUX, Louisiana
GORDON SMITH, Oregon                 BYRON L. DORGAN, North Dakota
PETER G. FITZGERALD, Illinois        RON WYDEN, Oregon
JOHN ENSIGN, Nevada                  MAX CLELAND, Georgia
GEORGE ALLEN, Virginia               BARBARA BOXER, California
                                     JOHN EDWARDS, North Carolina
                                     JEAN CARNAHAN, Missouri
                  Mark Buse, Republican Staff Director
               Ann Choiniere, Republican General Counsel
               Kevin D. Kayes, Democratic Staff Director
                  Moses Boyd, Democratic Chief Counsel

                            C O N T E N T S

Hearing held on May 1, 2001......................................     1
Statement of Senator McCain......................................     1
Statement of Senator Stevens.....................................     7
Prepared statement of Senator Kerry..............................    69


Craig, Hon. Larry E., U.S. Senator from Idaho....................     2
Hagel, Hon. Chuck, U.S. Senator from Nebraska....................     4
Hansen, Dr. James, Director, Goddard Institute for Space Studies, 
  National Aeronautics and Space Administration..................    42
    Prepared statement...........................................    44
Lindzen, Dr. Richard S., Massachussetts Institute of Technology..    24
    Prepared statement...........................................    27
McCarthy, James J., Director, Museum of Comparative Zoology, 
  Harvard University.............................................    19
    Prepared statement...........................................    21
Ramaswamy, Dr. Venkatachala, Senior Scientist, Geophysical Fluids 
  Dynamics Laboratory, National Oceanic and Atmospheric 
  Administration.................................................     9
    Prepared statement...........................................    11
Sathaye, Dr. Jayant A., Senior Scientist, Lawrence Berkeley 
  National Laboratory, University of California..................    31
    Prepared statement...........................................    33


Response by Dr. Venkatachala Ramaswamy to written questions 
  submitted by Hon. John McCain..................................    70
Response by Dr. James J. McCarthy to written questions submitted 
  by Hon. John McCain............................................    75
Response by Dr. James Hansen to written questions submitted by 
  Hon. John McCain...............................................    77
Response by Dr. Richard S. Lindzen to written questions submitted 
    Hon. John McCain.............................................    84
    Hon. John Kerry..............................................    85



                          TUESDAY, MAY 1, 2001

                               U.S. Senate,
        Committee on Commerce, Science, and Transportation,
                                                    Washington, DC.
    The Committee met, pursuant to notice, at 9:30 a.m. in room 
SR-253, Russell Senate Office Building, Hon. John McCain, 
Chairman of the Committee, presiding.


    The Chairman. Good morning. Last year, we held three 
hearings on the issue of climate change. Today we hope to 
continue the dialog on this very important matter confronting 
not only the nation but the world. In recent discussions 
surrounding the President's position on the Kyoto Protocol 
there were several questions concerning the availability of 
sound science in the decisionmaking process.
    At this hearing, we hope to have an open and frank 
discussion on the recent third assessment report by the 
Intergovernmental Panel on Climate Change. The IPCC efforts are 
recognized as one of the most comprehensive in this matter. It 
involves the work of hundreds of scientists from around the 
    The third assessment report is an up-to-date assessment of 
published and peer-reviewed policy relevant scientific, 
technical, and socioeconomic literature. The previous 
assessment report was issued 5 years ago. The latest report 
concludes that a firmer association between human activities 
and climate seems to have emerged. I look forward to discussing 
the basis for such a conclusion by the panel.
    I am disappointed, but not surprised to hear that the most 
vulnerable to these changing conditions are those with the 
least resources. The report states the effects of climate 
change are expected to be the greatest in developing countries 
in terms of loss of life and effects on investment and the 
economy. Therefore, the developed countries like the United 
States must do its share in addressing this global problem.
    Any agreement on the Kyoto Protocol will have real effects 
on our economy. It is interesting to note that the report 
indicates that about half of the emissions reductions targets 
may be achieved with a net economic benefit, according to the 
report. This sounds like the basis for action to me.
    While we appreciate the work of the hundreds of scientists 
involved in this effort, we recognize that a substantial amount 
of research remains before we can fully understand the complex 
and dynamic relationship between the atmosphere, the oceans, 
land, and mankind. I plan to review the U.S. research 
contributions to this global problem to ensure that our 
contributions are helpful and adequate.
    I note that much of the assessment report is based upon 
computer models, and I must say that I am alarmed to hear about 
the recent National Research Council's report on the 
shortcomings of the U.S. climate modeling program. We hope that 
today's discussion will go a long way in aiding this Committee 
and the Congress in crafting future actions to address this 
issue. This is the fourth hearing we have held on this topic in 
the past year.
    I plan to work with the other members of this Committee and 
the Senate, along with our witnesses today, to determine the 
appropriate next step in this complicated process of addressing 
the changing global climate. I welcome all of our witnesses 
here today. We would like to start with our two colleagues from 
the Senate, Senator Craig and Senator Hagel, and obviously we 
would appreciate your remarks and hope that they can be 
relatively brief.
    Senator Craig, welcome.

                           FROM IDAHO

    Senator Craig. Well, Mr. Chairman, certainly I thank you 
for convening this hearing today, and I think you and I both 
agree that the potential of climate change is a serious issue 
with high stakes. I do believe that premature government action 
to cut back energy use to levels lower than those in the 
growth-oriented nineties could cool the economy faster than it 
cools the climate.
    On the other hand, you and I agree that ignoring the 
concerns expressed by some respected scientists about recent 
warming trends is equally irresponsible. During the last 4 
years, Mr. Chairman, you have held hearings, I have held 
hearings, Senator Hagel, I, and a good many others have been 
involved in the fascinating issue.
    I have traveled to Woods Hole to listen to the scientists. 
I have traveled to the Hague to see the international politics 
of this. I have attended numerous hearings. I have listened and 
read the testimony out of the hearings that you have assembled. 
Clearly, the scientific community has made impressive gains in 
its understanding of global climate change, but with increased 
understanding has come increased uncertainty about the relative 
roles of greenhouse gases, aerosols, land coverage changes, 
ocean currents, in the last century's temperature changes.
    In my opinion, Mr. Chairman, moving ahead with strict 
government action based upon our current best guess of what we 
are thinking is not a wise action. This is especially true in 
light of the potential economic and national security 
implications that are likely as consequences of restricting our 
nation's energy use.
    What is needed at this time, Mr. Chairman, is steady and 
thoughtful leadership, and I think your hearings demonstrate 
that national policy on this issue must evolve commensurately 
with the increasing confidence we achieve in our scientific 
understanding. Consensus on appropriate action should be the 
cornerstone of our national policy on this issue.
    The National Academy of Science, upon the authority of a 
charter granted by the Congress in 1863, has a mandate that 
requires it to advise our government on scientific and 
technical matters. The creation of the United Nations 
Intergovernmental Panel on Climate Change, which you have 
referenced, the IPCC, does not, indeed, should not, extinguish 
the mandate of the National Academy to advise our government on 
scientific and technical matters.
    Let me be clear, Mr. Chairman, that I am not here today to 
impugn the work of the scientists associated with the IPCC's 
third assessment. Frankly, after conferring with many of the 
scientists who are credentialed in the disciplines of 
atmospheric and ocean science, I am quite confident that much 
of the underlying work contained in the assessment is 
relatively sound. However, these same scientists who I have 
conferred with caution that the conclusions contained in the 
assessment summary, much of which have been reported by the 
media, are by no means certain and, at the very least, in need 
of scrutiny.
    The computer modeling that you referenced in your opening 
statement, Mr. Chairman, is a part of our concern. In my 
opinion, the President of the National Academy of Science 
should be tasked to review the IPCC Third Assessment 
conclusions, for the following reasons:
    First, The National Academy, through its operating arm, the 
National Research Council, has been reviewing the science of 
climate change for most of two decades.
    Second, many of the scientists involved in the NRC research 
on climate change have contributed scientific analysis to the 
IPCC's third assessment.
    And, finally, the NRC has prepared recent reports 
themselves, a synthesis of many other studies, that are useful 
guides to the state of knowledge and the requirements for the 
scientific path forward.
    Mr. Chairman, I have reviewed the recent scientific 
reports, as I know you have. The NRC's ``Pathways'' and 
``Climate Modeling'' reports raise some profoundly important 
questions. Our best policy decisions could turn on answers to 
any of them. Now, the ``Pathways'' report stated that presently 
available observation and modeling information--again, you have 
expressed that concern on climate change--is useful, but cannot 
provide the knowledge needed to make informed decisions on the 
kinds of critical policies that we would direct.
    The most recent National Research Council's report, ``The 
Science of Regional and Global Change--Putting Knowledge to 
Work,'' which I and Senator Hagel and Senator Murkowski made 
available to all Senators in March, reaffirms the very findings 
and the very concerns I am expressing. Last week, I met with 
Charles Kennel, who co-authored that report and has chaired a 
NRC Committee on climate change, also heads up the Scripps 
Institution of Oceanography out at La Jolla. He expressed those 
concerns, and suggests some approaches to bringing about a 
better modeling system.
    In addition, Mr. Chairman, the National Academy recognizes 
the legitimacy of our concern about the increasing use of 
science as an advocacy tool for political agendas by making the 
following statement on page 10 of that report:

          ``Research on how to do more effective, credible, and helpful 
        scientific assessment is badly needed. Of particular importance 
        will be the development of assessment processes, that link 
        knowledge producers and users in a dialog that builds a mutual 
        understanding of what is needed, what can credibly be said, and 
        how it can be said in a way that maintains both scientific 
        credibility, and political legitimacy.''

    The National Academy proposes solid recommendations for 
implementing an effective research agenda, and I strongly 
endorse them.
    Mr. Chairman, the National Academy is putting together and 
inviting all of us to a high-level, half-day forum at the 
Academy's headquarters that I would encourage all of us to 
attend. I have encouraged Paul O'Neill of the Treasury to be an 
attendee. He is an outspoken person on this issue. Clearly, we 
need to consult with our scientists, but in the process, I do 
believe we need to build computer models that we can rely on, 
and not rely on international models that do not have the 
sensitivity to a variety of the concerns, but most importantly, 
to the quality of the science involved.
    Well, you have urged us to be brief, and I will conclude. 
There are important issues to be dealt with here, Mr. Chairman 
Thorough vetting by this Committee and others is critical, but 
I do believe we have come a long way, but I do not believe that 
the science today or the modeling available that brings that 
science together will lead us to a basis for sound 
policymaking. I think it is our responsibility to bring all of 
those tools together.
    In visiting with Dr. Kennel the other day, he made it clear 
our science is good. The problem is, Mr. Chairman, is that the 
science is over here, and the modeling capability is over 
there, and we have not put those two together yet. We have all 
of those resources in our government. We have the 
supercomputers at the Department of Energy, and we have the 
brain trust that has been assembled by the National Research 
Council through the National Academy of Science. I think it is 
our responsibility to not only drive the process that helps put 
the proper models together and brings the resources of our 
federal government together that will allow us, this Committee 
and other committees, the kind of sound decisionmaking based on 
good science that the policy for this country demands.
    Thank you very much.
    The Chairman. Thank you, Senator Craig.
    Senator Hagel.

                         FROM NEBRASKA

    Senator Hagel. Mr. Chairman, thank you. I, like our 
colleague, Senator Craig, am grateful for an opportunity to 
come before your Committee this morning and discuss an issue 
that I have been deeply involved in over the last several 
years. I have come across few issues, Mr. Chairman, more 
complex than climate change. What exactly is happening? What is 
the science? Are the actions of humans having a real impact on 
climate change? What is the future?
    Most importantly, I think we asked ourselves, what do we 
do? None of these questions have simple answers We do know 
there has been climate change since the beginning of time. In 
fact, very radical climate change, long before the industrial 
revolution or the internal combustion engine.
    Climate change, Mr. Chairman, is not new. In addressing 
this complicated issue, I start with this premise. Debate over 
climate change is not a question of who is for or against the 
environment. We all support protecting our involvement. I have 
yet to meet a Senator or any public official who wants to leave 
dirty air, dirty water, or a degraded environment as the legacy 
for his or her children. There may be one, Mr. Chairman. I have 
not met him or her.
    Over the last 3 months, three scientific working groups of 
the Intergovernmental Panel on Climate Change, IPCC, have 
released thousands of pages of their work for the IPCC's 
assessment. The summaries of those reports are written not by 
the scientists, Mr. Chairman, but by U.N. environmental 
activists. There is a reason the organization is called the 
Intergovernmental Panel on Climate Change. The summaries are 
political documents drafted by government representatives after 
intense negotiating sessions. In some cases, the very people 
sent to represent their countries in writing the IPCC summaries 
are later working to negotiate the provisions of the Kyoto 
Protocol, so you have the same people defining the problems who 
are also trying to create a solution.
    The working group reports vary widely in their scientific 
conclusions and predictions for global warming during the next 
century, but the summaries tend to take very alarmist 
viewpoints which are then used to justify the draconian 
measures of the Kyoto Protocol. The IPCC summaries are not 
science, they are summaries. Furthermore, the predictions made 
by the IPCC are based on computer models, which have already 
been shown to be inadequate, and vary widely in their 
    Just as you have noted, Mr. Chairman, as has Senator Craig, 
the National Research Council recently issued a report called 
the Science of Research nd Global Change, in that they 
discussed the abilities of current climate models and here is 
what they said,

          ``The United States today does not have computational and 
        modeling capability needed to serve society's information needs 
        for reliable environmental predictions and projections.''

    This is what the Clinton administration's Environmental 
Protection Agency has to say about computer climate models:

          ``Virtually all published estimates of how climate change 
        could change in the U.S. are the result of computer models. 
        These complicated models are still not accurate enough to 
        provide a reliable forecast on how climate may change, and 
        several models often yield very contradictory results.''

    This is from President Clinton's EPA.
    We know that the earth's climate has, for thousands of 
years, gone through cycles of warming and cooling. Ice core 
samples from Greenland more than 2 miles deep, dating back more 
than 100,000 years, have shown dramatic fluctuations in the 
earth's temperature. Since the end of the Ice Age, the last Ice 
Age 11,000 years ago, when the earth was 12.6 degrees 
Fahrenheit colder than today, there have been several warming 
and cooling periods.
    Over the last 100 years, surface temperatures have 
increased by approximately 1 degree Fahrenheit. However, most 
of that increase in surface temperature occurred before 1940, 
yet 80 percent of the manmade carbon dioxide was emitted after 
1940. Furthermore, while temperatures on the earth's surface 
have risen slightly over the last two decades, satellite 
temperatures, which are far more accurate, have shown no 
warming over the last 20 years.
    In fact, from 1979 to 1997, satellite temperatures showed a 
slight cooling trend of .04 degrees Fahrenheit. Even the 
scientists most associated with global warming, who we will 
hear from this morning, Dr. James Hansen, Director of NASA's 
Goddard Institute for Space Studies, issued a new analysis last 
year which said the emphasis on carbon dioxide emissions may be 
misplaced. He will obviously speak for himself, Mr. Chairman.
    In 1988, Dr. Hansen testified before a Senate committee 
that human activities were causing global warming. In his 
report las August, he found that mandate emissions of carbon 
dioxide have already been falling. They shrank in 1998 and 
    In his report, he stated that other greenhouse gases such 
as methane, black soot, CFC's, and the compounds that create 
smog maybe causing more damage than carbon dioxide, and efforts 
to affect climate change should focus on these other gases 
because the technology already exists to capture many of them. 
The prospects for having a modest climate impact instead of 
disastrous one are quite good, I think, said Dr. Hansen, who 
was quoted as saying this in the New York Times on August 19, 
    Other preeminent climatologists and meteorologists have 
conducted studies which have offered credible alternatives for 
the causes of our warming trend. Dr. Sally Belinius, the 
director of science programs at Harvard's Center for 
Astrophysics has been able to closely correlate changes in the 
Sun's brightness with temperature changes on earth. Unlike 
climate models, her studies have been able to explain why most 
of the earth's warming in the last 100 years occurred before 
the significant growth in manmade greenhouse gas emissions. 
According to her work, solar activity may be the most direct 
factor in global warming.
    Mr. Chairman, we know that we are far from understanding 
the dynamics of our climate and what stimulates the changes it 
undergoes. Increasing research and intensifying our scientific 
effort will help lead us to clear answers to the questions, 
what is going on, and what is causing it.
    In the last Congress, Senators Murkowski, Craig, and I 
introduced legislation that would dramatically increase funding 
for research. I would like to thank you, Mr. Chairman and your 
fellow Commerce Committee members, Senators Dorgan, Brownback, 
Burns, Smith, others for cosponsoring that legislation. We will 
be updating and reintroducing this legislation in the next few 
    In conclusion, Mr. Chairman, what do we do about climate 
change? Nothing? No, I do not believe so. None of us have 
advocated that. That would be irresponsible. However, it would 
have been equally irresponsible to submit this nation to a 
treaty that would have had a disastrous effect on our economy 
without having any real impact on global emissions of 
greenhouse gases.
    President Bush's Interagency Task Force, reviewing climate 
change, has been listening to and learning from some of the 
world's foremost meteorologists, climatologists, and scientists 
in informal meetings. In fact, I believe some of the scientists 
we hear from this morning have been in those briefings. He has 
said that the administration will soon offer a relevant, 
science-based, realistic alternative to the Kyoto treaty. That 
is the responsible thing to do.
    The United States is still a party to the Framework 
Convention on Climate Change, the Rio treaty, which was signed 
by the United States and ratified by the U.S. Senate in 1992. 
We should go back to the framework of that treaty before the 
Berlin mandate of 1994 that excluded developing countries from 
participation and laid the groundwork for future international 
efforts. If we are creative, and our partners will work with us 
in good faith, we can negotiate arrangements that are 
responsible, proactive, and realistic.
    The United States will need to demonstrate a commitment to 
act domestically before it will be able to build international 
support for action absent the Kyoto Protocol. It is in our best 
interests to create a domestic agenda that will reduce 
greenhouse gas emissions without the heavy hand of government 
mandates. A forward-looking domestic policy will demonstrate 
our commitment, enhance what we genuinely know about climate 
change, what we do not know about climate change, create m ore 
efficient energy sources, and have the additional effect of 
reducing pollutants.
    Mr. Chairman, climate change is a serous issue that 
deserves serious consideration and, as I stated earlier, our 
colleagues, Senators Murkowski, Craig, and I, along with 
others, will soon introduce legislation to improve the 
scientific knowledge base and lay out positive steps that we 
can take now to address that change.
    I again add my thanks, congratulations to you, your active 
participation, this Committee's oversight, to this effort. It 
will take all of us understanding more and more of not just the 
sound science dynamic of this, but what do we do about it, and 
how do we apply the resources that we have in this country and 
in the world to address this issue.
    Mr. Chairman, thank you.
    The Chairman. I thank you both, Senator Craig and Senator 
Hagel. We appreciate your input, and we look forward to working 
with you as we address, as you noted, this issue of deep, 
growing and serious concern on the part of all Americans. Thank 
you very much for being here today.
    Senator Stevens would like to make a comment or remarks 
before he has to go to another hearing.

                          FROM ALASKA

    Senator Stevens. Thank you very much, Mr. Chairman. I, too, 
congratulate you for these hearings.
    I have just returned from the Arctic and our people in 
Alaska, along the Arctic Coast, are very worried about the 
change that they are observing now, and I intend to take a 
group of Senators and staff to Alaska over the Memorial Day 
recess to have hearings in Fairbanks with the International 
Arctic Research Commission on the question. I wanted to call 
that to your attention, and those who are here. I hope many 
Senators will join us.
    We have faced the problem of moving Native villages that 
have been located along the Arctic and West Coast of Alaska for 
centuries because they are slowly but surely being inundated by 
sea water. That is true of Point Barrow. I talked to some of my 
friends who have been out on the ice this year and they tell me 
that the ice thickness is probably 8 inches thinner this year 
than it was last year, and that we probably are going to have 
to move a substantial portion of Point Barrow.
    The difficulty is, is that this is a creeping disaster. It 
is not a disaster--we are not even sure that it is covered by 
the existing disaster law, but very clearly what I want the 
Members of the Senate to see along with me and others, and 
listen to, some of the international people who have been 
working with the International Arctic Research Commission to 
try and define what we can expect with regard to the changes in 
the Arctic.
    As you know, the Northwest Passage will be open for the 
third year in a row. We have observed open needs at the North 
Pole itself in the Arctic, and I think it is a very serious 
thing, particularly for my state and the people who live along 
the coastline of my state. I would be glad to invite any member 
of the committee who wants to join us.
    We intend to stop two or three places and see, actually see 
the onslaught of the ocean on these people who live along the 
shore in our state, and then we will listen to some of the 
people from throughout the Northern Hemisphere and Japan and 
Canada and the United States, and try to tell us their 
predictions of what we can expect.
    We hope we will get some idea of the timing of the impact 
on the Arctic, but I do thank you for the time right now, and I 
would urge any member of this Committee who wants to join us to 
let us know, because we will be leaving for that period.
    There will be hearings in Fairbanks for 2 days right after 
Memorial Day and before that we will go up and look at the 
Arctic in two or three places to see what is happening there. 
Thank you very much for the time.
    The Chairman. I thank you, Senator Stevens, for what you 
had to say. It argues for taking more action than increasing 
our modeling capabilities. I thank you, Senator Stevens. I know 
you have to go.
    Our next panel is--would they please come forward?--Dr. 
Venkatachala Ramaswamy, senior scientist, Geophysical Fluids 
Dynamics Laboratory, National Oceanic and Atmospheric 
Administration, henceforward known as NOAA, Dr. James McCarthy, 
director of the Museum of Comparative Zoology at Harvard 
University, Dr. Jayant Sathaye, senior scientist at Lawrence 
Berkeley National Laboratory, University of California, Dr. 
James Hansen, chief of the Goddard Institute for Space Studies 
at NASA, and Dr. Richard Lindzen, who is professor at 
Massachusetts Institute of Technology in Cambridge.
    Dr. Ramaswamy.


    Dr. Ramaswamy. Mr. Chairman and members of the committee, 
good morning. My name is Venkatachala Ramaswamy. I appreciate 
the invitation to appear before your Committee and give a 
report on the state of the scientific understanding of global 
climate change, as documented in the recently concluded IPCC 
report. Copies of the summary for policymakers and technical 
summary have been distributed, as has been the verbal testimony 
with its appendix.
    Just a brief word about the assessment. The assessment took 
almost 3 years in preparation, between 1998 and 2001, and 
represents the work of over 100 scientific authors as well as 
several hundred contributing authors worldwide. It is based on 
peer-reviewed scientific literature and was carefully 
scrutinized by hundreds of scientific peers through an 
extensive review process.
    I was a coordinating lead author for one of the chapters. 
There were 14 chapters in all. I was coordinating lead author 
of one of the chapters, and also a member of the drafting team 
of the summary for policymakers, which carefully went through 
the science contained in the summary. My testimony today 
summarizes the understanding as it is manifested in the various 
chapters of the report, and as summarized in the summary for 
    Before starting on the scientific findings of the new 
report, I would like to begin with the reiteration of a 
fundamental longstanding knowledge, namely, that (1) there is a 
natural greenhouse effect which keeps the earth warmer than it 
would be otherwise, and (2) greenhouse gases are increasing in 
the atmosphere because of human activities, and they are 
increasingly trapping more heat in the climate system.
    There are many agents which force climate change, and these 
factors are greenhouse gas concentrations, tropospheric 
aerosols, the sun's energy output, land use change, and the 
explosive episodic volcanic eruptions which lead to transitory 
increases in stratospheric aerosols.
    The characteristics of these forcings can be summarized as: 
the long-lived gases have a forcing which is global in extent, 
that is, they exert a forcing all over the globe; this is in 
contrast to short-lived species, for example, ozone and 
aerosols, which vary considerably with region and season. Sun 
and volcanoes are natural forcing factors.
    One characteristic stands out from the assessment of the 
forcings, which is that the estimate and the level of 
scientific understanding of greenhouse gases forcing is greater 
than for other forcings.
    Before discussing the effects of these agents on climate 
change, let us state what has the actual climate undergone and 
what are our observations of the climate system? Well, the 
measurements suggest that there is a growing collective picture 
of a warming world over the past century. The global-mean 
surface temperatures are up .4 to .8 degrees Celsius over the 
past 100 years. In the hand-out, there is a diagram showing the 
Northern Hemisphere surface temperatures, culled from the last 
140 years, using instrumental record and, then, prior to that, 
using proxy records. It shows the degree of rapid increase of 
temperatures over the last century compared to both the mean 
and the variability expressed on the curve.
    Along with the global warming, there have been other 
changes which are consistent with this picture, namely the 
retreat of mountain glaciers in nonpolar regions, decrease in 
the amount of snow cover, the rise in the global average sea 
level by 4 to 8 inches.
    What are the causes of the observed warming? To analyze 
this issue, IPCC resorts to model simulations. Based on 
analysis of both the observed record and climate model 
simulations using the various forcing agents, it is seen that 
there is now new and stronger evidence that most of the 
observed warming over the past 50 years is attributable to 
human activities.
    This is based on the fact there is a better simulation of 
the instrumental temperature record when all the forcings, 
natural and human-related, are taken into consideration. Only 
natural forcings do not lead to a good agreement with the 
observations. Neither does the internal variability of the 
climate system, as estimated by models, explain the rise in 
    The key factors since the 1995 IPCC report are that there 
is now 5 years of additional data which shows a rapid increase 
of warming; and the new 1,000-year record, which is based on 
proxy data now extending prior to 140 years ago, and that sets 
up a context for the changes over the past century. Also, 
climate models have evolved and improved since the last IPCC 
    So now the question is, what could all of this mean for the 
future? IPCC considered a range of mission scenarios, and 
although the abundances of various greenhouse gases and 
aerosols in the future cannot be predicted with a high degree 
of confidence, IPCC considered a suite of possible futures 
based on considerations of economies, populations, et cetera.
    The conclusion from model calculations of the responses to 
these various scenarios is that a continued growth in 
greenhouse gases is projected to lead to very significant 
increases in global mean temperatures and sea level. As far as 
numbers are concerned, by 2100 the global mean surface 
temperature is projected to increase by 2\1/2\ to 10 degrees 
Fahrenheit, considering the range of scenarios, and considering 
the modeling uncertainties.
    The projected rate of warming from these model simulations 
is very likely to be larger than changes that have been 
observed over the past 10,000 years. Along with the global-mean 
surface temperature change, there is a corresponding projected 
sea level rise due to thermal expansion of sea water, on the 
order of 4 to 35 inches.
    Climate changes in specific regions and years cannot be 
predicted with a high degree of confidence but it is likely 
that there would be a shift of the climate to a new regime, and 
it is likely that the weather could be more variable.
    Amidst these projections, a key feature to be borne in 
mind, one which has been stated in the earlier IPCC reports and 
which is worth reiterating here today, is that the greenhouse 
warming can be reversed only very slowly. This is because of 
one, the slow rate of removal of many of the gases from the 
atmosphere--for example, CO2--because they have long 
lifetimes, and second, the slow response of oceans to thermal 
    Finally, Mr. Chairman, I would like to conclude with an 
important remark concerning the IPCC report. This climate 
science assessment is the considered viewpoint of hundreds of 
scientists worldwide, and is based upon the research results of 
the worldwide community that are published in numerous peer-
reviewed scientific journals; there are some 4,000 references 
that are referred to in the Working Group 1 report on the 
    The resulting report contains policy-relevant scientific 
information but, of course, makes no policy statements or 
recommendations. I will conclude by thanking you for the 
invitation to appear today, and to report the findings of the 
Working Group 1 on the scientific understanding of global 
climate change.
    I hope this summary has been helpful to you, Mr. Chairman, 
and to the committee. I would be happy to address any 
questions. Thank you very much.
    [The prepared statement of Dr. Ramaswamy follows:]
  Prepared Statement of Dr. Venkatachala Ramaswamy, Senior Scientist, 
Geophysical Fluid Dynamics Laboratory, National Oceanic and Atmospheric 
    Mr. Chairman: I am a Senior Scientist at NOAA's Geophysical Fluid 
Dynamics Laboratory located in Princeton University, Princeton, New 
Jersey. I appreciate the invitation to appear before your Committee and 
report on the state of the scientific understanding of global climate 
change as documented in the recently concluded Intergovernmental Panel 
on Climate Change (IPCC) assessment [``Climate Change 2001: The 
Scientific Basis'']. The IPCC was set up by the World Meteorological 
Organization (WMO) and the United Nations Environment Program (UNEP) to 
provide expert assessment of the knowledge and an authoritative 
international statement of the scientific understanding on climate 
    For over 30 years, the Geophysical Fluid Dynamics Laboratory has 
been a world leader in the development of numerical models for studying 
climate variations and climate change, and has made major contributions 
to the understanding of the Earth's climate system. My own research has 
involved estimating the natural and human-induced factors that force 
climate change, as well as investigating the manner in which the 
climate system responds to these factors. For over a decade, I have 
been involved in various national and international scientific 
assessments. These include National Academy of Science studies, WMO/
UNEP reports on the scientific understanding of the ozone layer and 
IPCC climate change science assessments. In the recently concluded IPCC 
scientific assignment, I served as the Coordinating Lead Author for the 
Chapter on ``Radiative Forcing of Climate Change.'' I was also a member 
of the panel which drafted the Summary for Policymakers that was 
formally approved in detail and accepted along with the underlying 
assessment report at the IPCC Working Group I Plenary session in 
January 2001.
    I appreciate the invitation to summarize the findings from the IPCC 
(2001) report. My information is based on the set of findings in this 
report. The assessment took almost three years in preparation and 
represents the work of over a hundred scientific authors worldwide. It 
is based on scientific literature, and was carefully scrutinized by 
hundreds of scientific peers through an extensive peer review process. 
My testimony today summarizes the understanding of these authors as 
manifested in the report.
    Before addressing the new findings of the recent report, two 
fundamental points are worthy of note. These have been long-known, are 
very well understood, and have been deeply underscored in all previous 
IPCC reports and other such scientific summaries.
     The ``greenhouse'' effect is real, and is an essential 
component of the planet's climate process. A small percentage (roughly 
2%) of the atmosphere is, and long has been, composed of greenhouse 
gases (water vapor, carbon dioxide, ozone and methane). These 
effectively prevent part of the heat radiated by the Earth's surface 
from otherwise escaping to space. The global system responds to this 
trapped heat with a climate that is warmer, on the average, than it 
would be otherwise without the presence of these gases.
    In addition to the natural greenhouse effect above, there is a 
change underway in the greenhouse radiation balance, namely:
     Some greenhouse gases are increasing in the atmosphere 
because of human activities and increasingly trapping more heat. Direct 
atmospheric measurements made over the past 40-plus years have 
documented the steady growth in the atmospheric abundance of carbon 
dioxide. In addition to these direct real-time measurements, ice cores 
have revealed the atmospheric carbon dioxide concentrations of the 
distant past. Measurements using the air bubbles that were trapped 
within the layers of accumulating snow show that atmospheric carbon 
dioxide has increased by more than 30% over the Industrial Era (since 
1750), compared to the relatively constant abundance that it had over 
the preceding 750 years of the past millennium [see Figure 2, IPCC 
Working Group I Summary for Policymakers, page 6]. The predominant 
cause of this increase in carbon dioxide is the combustion of fossil 
fuels and the burning of forests. Further, methane abundance has 
doubled over the Industrial Era. Other heat-trapping gases are also 
increasing as a result of human activities.
    The increase in greenhouse gas concentrations in the atmosphere 
implies a positive radiative forcing, i.e., a tendency to warm the 
climate system [see Figure 3, IPCC Working Group I Summary for 
Policymakers, 2001; page 8]. Particles (or aerosols) in the atmosphere 
resulting from human activities can also affect climate. Aerosols vary 
considerably by region. Some aerosol types act in a sense opposite to 
the greenhouse gases and cause a negative forcing or cooling of the 
climate system (e.g., sulfate aerosol), while others act in the same 
sense and warm the climate (e.g., soot). In contrast to the long-lived 
nature of carbon dioxide (centuries), aerosols are short-lived and 
removed from the lower atmosphere relatively quickly (within a few 
days). Therefore, aerosols exert a long-term forcing on climate only 
because their emissions continue each year. In summary, emissions of 
greenhouse gases and aerosols due to human activities continue to alter 
the atmosphere in ways that are expected to affect the climate. There 
are also natural factors which exert a forcing of climate, e.g., 
changes in the Sun's energy output and short-lived (about 1 to 2 years) 
aerosols in the stratosphere following episodic and explosive volcanic 
eruptions. IPCC evaluated the state of the knowledge and assessed the 
level of scientific understanding of each forcing. The level of 
understanding and the forcing estimate in the case of the greenhouse 
gases are greater than for other forcing agents.
    What do these changes in the forcing agents mean for changes in the 
climate system? What climate changes have been observed? How well are 
the causes of those changes understood? Namely, what are changes due to 
natural factors, and what are changes due to the greenhouse-gas 
increases? And, what does this understanding potentially imply about 
the climate of the future?
    These questions bear directly on the scientific points that you 
have asked me to address today. In doing so, findings emerging from the 
recent IPCC climate science report with respect to measurements, 
analyses of climate change to date, and projections of climate change 
will be summarized.
     There is a growing set of observations that yields a 
collective picture of a warming world over the past century. The 
global-average surface temperature has increased over the 20th century 
by 0.7 to 1.4 degrees Fahrenheit [See Figure 1, IPCC Working Group I 
Summary for Policymakers, 2001, page 3]. The average temperature 
increase in the Northern Hemisphere over the 20th century is likely to 
have been the largest of any century during the past 1,000 years, based 
on ``proxy'' data (and their uncertainties) from tree rings, corals, 
ice cores, and historical records. Other observed changes are 
consistent with this warming. There has been a widespread retreat of 
mountain glaciers in non-polar regions. Snow cover and ice extent have 
decreased. The global-average sea level has risen between 4 and 8 
inches, which is consistent with a warmer ocean occupying more space 
because of the thermal expansion of sea water and loss of land ice.
     There is new and stronger evidence that most of the 
warming observed over the last 50 years is attributable to human 
activities. The 1995 IPCC climate-science assessment report concluded: 
``The balance of evidence suggests a discernible human influence on 
global climate.'' There is now a longer and more closely scrutinized 
observed temperature record. Climate models have evolved and improved 
significantly since the last assessment. Although many of the sources 
of uncertainty identified in 1995 still remain to some degree, new 
evidence and improved understanding support the updated conclusion. 
Namely, recent analyses have compared the surface temperatures measured 
over the last 140 years to those simulated by mathematical models of 
the climate system, thereby evaluating the degree to which human 
influences can be detected. Both natural climate-change agents (solar 
variation and episodic, explosive volcanic eruptions) and human-related 
agents (greenhouse gases and fine particles) were included. The natural 
climate-change agents alone do not explain the warming in the second 
half of the 20th century. The best agreement between observations and 
model simulations over the last 140 years is found when both human-
related and natural climate-change agents are included in the 
simulations [see Figure 4, IPCC Working Group I Summary for 
Policymakers, 2001; page 11]. Further, model simulations indicate that 
the warming over the past century is very unlikely to be due to 
internal variability alone, i.e., variations within the climate system 
that would be expected even in the absence of any forcing. In light of 
such new evidence and taking into account the remaining uncertainties, 
the IPCC scientists concluded that most of the observed warming over 
the last 50 years is likely to have been due to the increase in 
greenhouse gas concentrations.
     Scenarios of future human activities indicate continued 
changes in atmospheric composition throughout the 21st century. The 
atmospheric abundances of greenhouse gases and aerosols over the next 
100 years cannot be predicted with high confidence, since the future 
emissions of these species will depend on many diverse factors, e.g., 
world population, economies, technologies, and human choices, which are 
not uniquely specifiable. Rather, the IPCC assessment endeavor aimed at 
establishing a set of scenarios of greenhouse gas and aerosol 
abundances, with each based on a picture of what the world plausibly 
could be over the 21st century. [The emission scenarios were based on 
the IPCC Special Report on Emissions Scenarios, 2000; a brief 
description of the scenarios appears in the box on page 18 of the 
Summary for Policymakers report.] Based on these scenarios and the 
estimated uncertainties in climate models, the resulting projection for 
the global average temperature increase by the year 2100 ranges from 
2.5 to 10 degrees Fahrenheit [see Figure 5, IPCC Working Group I 
Summary for Policymakers, 2001; page 14]. Such a projected rate of 
warming would be much larger than the observed 20th-century changes and 
would very likely be without precedent during at least the last 10,000 
years. The corresponding projected increase in global sea level by the 
end of this century ranges from 3.5 to 35 inches. Uncertainties in the 
understanding of some climate processes make it more difficult to 
project meaningfully the corresponding changes in regional climate.
    Finally, I would like to relate a basic scientific aspect, one that 
has been underscored with very high confidence in all of the IPCC 
climate-science assessment reports (1990, 1995, and 2001). It is 
repeated here because it is a key (perhaps ``the'' key) aspect of a 
greenhouse-gas-induced climate change:
     A greenhouse-gas warming could be reversed only very 
slowly. This quasi-irreversibility arises because of the slow rate of 
removal (centuries) from the atmosphere of many of the greenhouse gases 
and because of the slow response of the oceans to thermal changes. For 
example, several centuries after carbon dioxide emissions occur, about 
a quarter of the increase in the atmospheric concentrations caused by 
these emissions is projected to still be in the atmosphere. 
Additionally, global average temperature increases and rising sea level 
are projected to continue for hundreds of years after a stabilization 
of greenhouse gas concentrations (including a stabilization at today's 
abundances), owing to the long timescales (centuries) on which the deep 
ocean adjusts to climate change.
    Let me conclude, Mr. Chairman, with an important remark concerning 
the IPCC report. As noted, the IPCC climate-science assessment is the 
considered viewpoint of hundreds of scientists worldwide. This 
assessment is based upon the research results of the worldwide 
community that are published in numerous peer-reviewed scientific 
journals. The resulting report contains policy-relevant scientific 
information, but makes no policy statements or recommendations. As 
such, the three components of the 2001 IPCC Third Assessment Report--
climate science, impacts, and mitigation--are recommended as a key 
information source that is available to the Committee as it continues 
this important dialogue about climate change and its relation to 
    Thank you for the invitation to appear today. I hope that this 
summary has been useful. I would be happy to address any questions.





    The Chairman. Thank you very much.
    Dr. McCarthy, welcome.


    Dr. McCarthy. Thank you. Good morning, Mr. Chairman, and 
members. I am James McCarthy, professor of biological 
oceanography at Harvard University, where I am also the 
director of the Museum of Comparative Zoology, and I also head 
our undergraduate program on environmental science and public 
policy, but the reason I am here today, of course, is in my 
capacity as the co-chair of the Intergovernmental Panel on 
Climate Change Working Group 2. I and a colleague, Osvaldo 
Canziani, a meteorologist from Argentina, have co-chaired this 
Working Group.
    The charge of this Working Group was to assess evidence for 
impacts, adaptations and vulnerabilities associated with 
climate change. We began this assessment in the autumn of 1997, 
and concluded it earlier this spring.
    Mr. Chairman, I read the testimony related to climate 
change submitted to your Committee last year on three 
occasions, May, July, and September. In each case for which 
evidence of climate change impacts were cited, we now have 
greater confidence that these effects are widespread and more 
conclusively linked to climate change.
    Some witnesses presented evidence of no change in climate, 
or absence of climate change impacts. In my judgment it was the 
selection of data for a particular region or particular time 
period that led them to these conclusions. This, Mr. Chairman, 
is why the work of the IPCC is so important. Some nations have 
sponsored and will continue to sponsor studies that may show, 
quite correctly, that recent data for their localities do not 
show evidence of change. The IPCC focus is on broad patterns 
and generalizations that arise from these patterns.
    Dr. Neil Lane reported to you that 89 of 99 plants examined 
in the District of Columbia are blooming a full week earlier 
now than they did a mere 30 years ago, but is this true 
everywhere in the globe? Probably not. Were a survey in some 
other city to reveal no such change, would this cause one to 
doubt that there had been change in Washington, DC.? Certainly, 
it would not.
    From the IPCC assessment, what is now clear is that this 
type of effect in plants and animals over the last few decades 
is evident on all continents, and in 80 percent of the 
published cases, the change in the distribution of animals or 
their biology is consistent with local changes in temperature. 
This is strong evidence of biological response to climate 
    So, we have already seen effects of recent climate change 
in ecosystems. While none of these might be classified as 
dangerous per se, it is unlikely that they will be reversed 
within our lifetime by any action that we might take today to 
reduce the rate of climate change. And the rate of climate 
change projected for the 21st Century, as we have just heard 
from my colleague, is, on average, 2 to 10 times the rate 
observed in the 20th Century.
    In all likelihood, this projected change will lead to 
displacements of species, and perhaps extinctions, especially 
in tropical ocean and arctic ecosystems such as we were just 
hearing from Senator Stevens. But for the lives and livelihood 
of humankind, the largest associated effects of these shifts in 
organisms will be in regional agricultural productivity, and in 
distribution of disease organisms and their vectors. North 
American and Northern Eurasian agriculture may, in fact, be 
enhanced, albeit with a northward shift. However, the tropical 
and subtropical regions will be hardest hit, with potentially 
serious losses of agricultural capacity.
    Human systems other than agriculture are also being 
affected by climate change, some from general warming, such as 
with human health, but others from an increasing frequency, 
intensity, and persistence of extreme events.
    If climate change is steady and smooth, most of it may be 
accommodated or adapted to without great cost, but if the path 
is bumpy the story becomes very different. There is no good 
news in extreme events. These are inherently disruptive, and 
one need only look at the last 5 years to see the global 
evidence of this, with floods and mudslides of unprecedented 
proportion in Honduras in 1998, where more than 10,000 lives 
were lost, and Venezuela in 1999, where more than 25,0000 lives 
were lost, and on other continents as well, in Africa, with 
Mozambique and Kenya, in Asia with China and North Korea.
    Our report, Mr. Chairman, summarizes our assessment of the 
published literature on the likely effects of projected changes 
in climate on a suite of systems and economic sectors, and for 
eight broad regions of the globe we identify the most serious 
bilities. The tropical and subtropical regions, many of them 
already water-stressed and facing serious questions of food 
security, will be hardest hit. This disproportionate impact is 
in no small part because these regions, many with developing 
countries, are poorly equipped to adapt. In many cases they 
lack the infrastructure and simple resources such as in the 
case of public health measures. But it is also incorrect to 
assume that northern industrialized nations will be spared 
serious effects of climate change within their own sovereign 
territories. The fraction of their citizens who are most 
vulnerable to heat waves, floods, and droughts, will increase.
    In summary, Mr. Chairman, some of the climate changes 
projected for the future have positive effects: less human 
winter mortality in some regions, enhanced crop growth in 
others, for example, but most systems and most sectors and most 
people will be adversely affected by this climate change. For 
most people, the projected rate of change will simply exceed 
capacities to adapt to even gradual change, let alone a future 
with more frequent, intense, and persistent extreme events.
    Our report calls attention to the need to explore all 
opportunities to reduce potential adverse effects of climate 
change by enhancing adaptive capacity, as with some of the 
issues that were being addressed by Senator Stevens.
    Thank you again, Mr. Chairman, for this opportunity to 
present some of our results to your Committee. I realize that 
in addition to the results of the assessment themselves, you 
and members of your Committee may have some questions about the 
methods and procedures of the IPCC. I refer here specifically 
to the last portion of my submitted testimony, in which I 
discussed the actual preparation of the Summary for 
Policymakers and, with all due respect, I think Senator Hagel 
has been misinformed as to how this actually occurs.
    In my written testimony, I have remarked on this process, 
and I will be happy to discuss further any aspect of the 
findings of either the procedures of the IPCC Working Group 2, 
or its results, as you wish.
    Thank you.
    [The prepared statement of Dr. McCarthy follows:]
          Prepared Statement of James J. McCarthy, Director, 
           Museum of Comparative Zoology, Harvard University
    Thank you, Senator McCain, for this opportunity to address the 
Committee on Commerce, Science, and Transportation. My name is James J. 
McCarthy, and I am a Professor of Oceanography, the Director of the 
Museum of Comparative Zoology, and the Head Tutor for undergraduate 
students studying Environmental Science and Public Policy at Harvard 
    For nearly four years I have co-chaired Working Group II (WG II) of 
the Intergovernmental Panel on Climate Change (IPCC). The focus of this 
working group has been to assess potential impacts, adaptations, and 
vulnerabilities to climate change. In my letter of invitation to this 
hearing you have asked that I comment on the results and conclusions of 
the IPCC WG II and other related issues that I wish to bring to the 
attention of the Committee.
    The new WG II report, Climate Change 2001: Impacts, Adaptation, and 
Vulnerability, is the most comprehensive and up-to-date scientific 
assessment of the consequences of, and adaptation responses to, climate 
change. The report:
     evaluates evidence that recent observed changes in climate 
have already affected a variety of physical and biological systems.
     makes a detailed study of the vulnerabilities of human 
populations to future climate change, including associated sea-level 
rise and changes in the frequency and intensity of climate extremes 
such as floods, droughts, heat waves and windstorms, and taking into 
account potential impacts on water resources, agriculture and food 
security, human health, coastal and other types of settlements, and 
economic activities.
     assesses the potential responses of natural environments 
and the wildlife that inhabit them to future climate change and 
identifies environments at particular risk.
     considers how adaptation to climate change might lessen 
adverse impacts or enhance beneficial impacts.
     provides an overview of the vulnerabilities and adaptation 
possibilities by major region of the world (Africa, Asia, Australia/New 
Zealand, Europe, Latin America, Polar Regions, and Small Island 
     contrasts the different vulnerabilities of the developed 
and developing parts of the world and explores the implications for 
sustainable development and equity concerns.
    Research on climate impacts has grown considerably during the five 
years since the last IPCC assessment, and much has been learned 
regarding the potential risk of damage associated with projected 
climate change. In particular, this research has added new 
understanding of vulnerabilities to climate change across a spectrum of 
ecological systems (forests, grasslands, wetlands, rivers, lakes and 
marine environments) and human systems (agriculture, water resources, 
coastal resources, human health, financial institutions, and human 
    Observational evidence of changes has accumulated in many physical 
and biological systems (e.g. glacial melting, shifts in geographic 
ranges of plant and animal species, and changes in plant and animal 
biology) that are highly consistent with warming observed in recent 
decades. These observations are adding to our knowledge of the 
sensitivity of affected systems to changes in climate and can help us 
to understand the vulnerability of systems to the greater and more 
rapid climate changes projected for the 21st century. A number of 
unique systems are increasingly recognized as especially vulnerable to 
climate change (e.g. glaciers, coral reefs and atolls, mangroves, 
boreal and tropical forests, polar and alpine ecosystems, prairie 
wetlands, and remnant native grasslands). In addition, climate change 
is expected to threaten some species with greater probability of 
extinction. Potential changes in the frequency, intensity, and 
persistence of climate extremes (e.g. heat waves, heavy precipitation, 
and drought) and in climate variability (e.g. El Nino--Southern 
Oscillation) are emerging as key determinants of future impacts and 
vulnerability. The many interactions of climate change with other 
stresses on the environment and human populations, as well as linkages 
between climate change and sustainable development, are increasingly 
emphasized in recent research and preliminary insights from these 
important efforts are reflected in the report.
    The value of adaptation measures to diminish the risk of damage 
from future climate change, and from present climate variability, was 
recognized in previous assessments and is confirmed and expanded upon 
in the new assessment. Understanding of the determinants of adaptive 
capacity has advanced and confirms the conclusion that developing 
countries, particularly the least developed countries, have lesser 
capacity to adapt than do developed countries. This condition results 
in relatively high vulnerability to damaging effects of climate change 
in these countries.
                       more specific new findings
    The effects of recent climate change are now clearly evident in 
many natural systems. Changes in the distribution of species as 
documented in the fossil record have long been used as an important 
diagnostic of past climate. In addition, it is well known that the 
seasonal behavior of many species, such as migrations and reproductive 
behavior (e.g. flowering time and egg laying) are sensitive to 
temperature. In the past few decades substantial changes in these 
characteristics have been noted for many species, and for 80% of the 
cases for which such changes could plausibly be linked to temperature, 
the biotic changes were consistent with changes in regional 
    The documented changes in Arctic sea ice cover, both its thinning 
and its shrinkage during summer, affect polar ecosystems. The shrinkage 
that is occurring has averaged 3% per decade for the entire Arctic over 
the last three decades. Throughout Northern Hemisphere freshwater 
ecosystems the ice-free season is now nearly 2 weeks longer than it was 
a century ago, which is consistent with an average annual temperature 
increase of about 1+ C. Increased access for ships is a positive aspect 
of this trend. During the summer of 2000, for the first time in 
recorded history, a RCMP ship transited the Northwest Passage without 
touching ice. With summer ice-free conditions in the Arctic expanding 
poleward, ecosystems will shift accordingly. Marine mammals, such as 
walrus, certain seals, and the polar bear have evolved with a 
dependence on ice for successful feeding and rearing of their young. As 
summer ice retreats from land earlier in the season and reaches greater 
maximum distances, the success of these species will be challenged. 
Now, in the span of a single human generation, observations point to a 
coherent shift in the pattern of temperature sensitive systems on all 
    Many human systems are also inherently sensitive to climate change. 
Examples in the IPCC report include:
     changes in potential crop yields, especially reductions in 
most tropical and subtropical regions.
     changes in water availability, especially losses in the 
     an increase in the number of people exposed to vector born 
diseases like malaria and water borne diseases like cholera.
     increased losses of lives, livelihood, and property from 
heavy rains and sea level rise.
    Already the increased frequency and intensity of extreme 
precipitation events has taken a heavy toll. Devastation caused by 
floods and mudslides in tropical to temperate regions on all continents 
in the last decade has been without precedent. While a gradual increase 
in temperature might be accommodated by many natural and human systems, 
the projected increases in frequency, intensity, and persistence of 
extreme events has the potential to be enormously disruptive. Moreover 
the impacts of these changes will fall disproportionately on the 
poorest peoples. While this may be an obvious conclusion when comparing 
certain developed and developing countries, it will also be true within 
a developed country. The fraction of the population that is vulnerable 
to an extreme heat wave or flood will increase with the severity of the 
extreme event.
    Many of the most devastating aspects of climate change will occur 
in tropical and subtropical regions, where 70% of the world's 
population live, many in developing countries. These are the regions 
that will be the most water stressed, suffer the greatest potential 
losses of agricultural capacity, and be most vulnerable to the expanded 
ranges of certain infectious diseases. Even allowing for possible 
benefits from climate change in some temperate regions, such as net 
gains in potential crop yields, the negative aspects of climate change 
in subtropical and tropical regions are likely to offset these positive 
aspects even assuming there would be no infrastructure or financial 
obstacle to the distribution of resources, i.e. food, moved from one 
region to another.
    Thus the following are evident in the recent IPCC assessment:
     responses to climate change are already occurring in 
natural and human systems.
     it is highly likely that climate changes in the 21st 
century will be 2--10 faster than those of the 19th century.
     increased frequency and severity of extreme events will be 
costly to natural and human systems.
    Given the inertia in human system-climate system linkages, these 
findings lead inevitably to the conclusion that even the most 
optimistic scenarios for mitigating future climate change are unlikely 
to prevent significant damage from occurring. This is not to say that 
mitigation efforts such as a fully implemented Kyoto Protocol won't be 
effective; rather that their effect won't be evident for decades. Thus, 
an important finding of the IPCC is that adaptation will be absolutely 
necessary to minimize damage that is projected from future climate 
change. Limitations in adaptive capacity will make some regions and 
some peoples of lesser means more vulnerable to the impacts of climate 
change. Natural systems will be affected in all regions from polar to 
tropical on all continents. Human systems will, however, be most 
vulnerable to climate change in Africa, Latin America, and Asia where 
current adaptive capacity is low.
    If we wish to minimize the loss of lives, livelihoods and property 
that will occur during our inevitable transition to a warmer world, it 
is imperative that we redouble efforts to both minimize the emissions 
of fossil fuel combustion products and prepare peoples and systems as 
best we can for the disruption that will ensue with the climate change 
that is now projected for the 21st century.
                      comments on the ipcc process
    Nowhere can one find a process that produces a report on the 
understanding of a broad area of science that is more inclusive in its 
coverage of contemporary scientific views, or more broadly vetted by 
the scholarly community than with the IPCC. The basis of the assessment 
is the peer-reviewed published scientific literature. Every effort is 
made to be thorough, and serious attention is given to disparate 
results and conclusions in this literature. To the extent possible, 
degrees of likelihood are assigned to summary statements, especially 
those on projected climate conditions and climate impacts.
    Currently about 100 governments participate in the IPCC, and all 
were invited to propose the names of experts who could serve as authors 
of this report. More than one thousand nominations were received for WG 
II authors, with supporting documentation listing the nominees' 
publications in scientific journals. It should be noted that the 
authors of IPCC reports work without financial compensation for their 
efforts on behalf of the IPCC.
    The report of WG II was drafted between July 1998 and February 2001 
by 183 Lead Authors. In addition, 243 Contributing Authors, from nearly 
70 countries, submitted draft text and information to the Lead Authors. 
Drafts of the report were circulated twice for review, first to experts 
and a second time to both experts and governments. Comments received 
from 440 reviewers were carefully analyzed and assimilated in a revised 
the document, with guidance provided by 33 Review Editors. The full 
report was then condensed into a 70-page manuscript, known as a 
Technical Summary (TS), and it was then further condensed into a 20-
page manuscript known as a Summary for Policy Makers (SPM). The TS and 
SPM (along with a revision of the full report that reflected the 
earlier government and expert review) were then sent out for a final 
review coordinated by governments.
    Comments from this final review were then used to prepare a 
revision of the SPM and TS, and a plenary of the Working Group was 
convened to consider final approval of the SPM. This involved about 150 
delegates from 100 nations, drawn from each nation's departments and 
ministries of state and science. The plenary met for four days in 
Geneva (Switzerland) in February 2001 to vet the SPM line-by-line, 
proceeding to the next line only when all delegates agreed to do so.
    While the science that underpins SPM was clear to its authors as 
their document was taken to the plenary for approval, the plenary is 
actually the final stage in this process of clarifying the message for 
policy makers. Discussions in the course of the plenary called 
attention to words and sentences that were perceived to be unclear by a 
delegate, and suggested changes were made as long as they were not 
inconsistent with the underlying science. By the conclusion of the 
meeting the Summary for Policymakers was approved in detail and the 
full report accepted by all delegations.
    The Working Group Summary for Policy Makers is attached. It and 
related documents are available in pdf format at www.usgcrp.gov/ipcc.
    The Summary for Policymakers.--Climate Change 2001: Impacts, 
Adaptation, and Vulnerability is being maintained in Committee files.

    The Chairman. Thank you, Dr. McCarthy.
    Dr. Lindzen.

                    INSTITUTE OF TECHNOLOGY

    Dr. Lindzen. Thank you, Senator McCain, for the opportunity 
to appear before this Committee. I am a member of the NAS, and 
I also participated in the third assessment report as a lead 
author on chapter 7.
    The Chairman. Chapter 7 was?
    Dr. Lindzen. The physics of climate. I come here usually 
designated as a skeptic. I am not sure what that means. I think 
in dealing with this, people are correct in saying that the 
science is complex, and I think the complexity is not only 
intrinsic, but has also resulted from the presentation of the 
issue, which in many ways has forced confusion and 
irrationality to dominate the discussion. It is presented as a 
multifaceted problem involving atmospheric composition, heat 
transfer, weather, temperature, ocean dynamics, hydrology, sea 
level, glaciology, ecology, and even epidemiology. All of these 
are subjects filled with uncertainty.
    On the other hand, and I do not say any of my colleagues 
here today have done this, but you know that it is frequently 
said the science is settled. This is often said without any 
statement as to exactly what is meant by this, and what 
relevance it has to the forecast being made. The IPCC itself as 
a document is not particularly extreme, and I agree with my 
colleagues that it tends to present the science more or less as 
it is for better or for worse, but in the popular eye it is 
used as a mantra. It inevitably is used by people who wish to 
convince others that the science is settled, it is supported by 
thousands of scientists, and that this relieves them of the 
necessity to explain the science.
    In point of fact, there are quite a few areas of agreement, 
and I think very few, if any of them, in any convincing way 
point to disaster, despite scenario creations of the type that 
Dr. McCarthy spoke of. For example, Dr. Ramaswamy mentioned 
things that are agreed upon, that the temperature has 
increased, that the CO2 has increased, that CO2 
is more likely to cause warming than cooling, and I would add 
to that that man, like the butterfly, has some impact on 
    What is frequently not realized is, the statements are as 
consistent with the statement that there will not be a problem 
as there will be a problem. They have very little substantive 
content, and yet they are perceived as having content.
    In addition, we tend to raise issues that are different 
from warming, per se. To be sure, a few degrees of warming, or 
a degree does not particularly frighten the public. All of us 
who have had the extraordinary experience of day and night, 
winter and summer, have experienced far greater changes, so we 
go to what I think used to be called show-stoppers, increased 
weather extremes, increased variability, rising sea levels, and 
so on.
    Now, I mention here a lot of things where there is 
widespread agreement on the science--that is hardly alarmist--
but I will mention one specifically, and you can read some of 
the others in the testimony, and that has to do with increased 
weather extremes and disturbances. Here, the science for at 
least 40 years has noted that at least outside the tropics the 
main source of generating storms is the difference in 
temperature between the equator and pole.
    Virtually all model predictions of global warming predict 
this will go down, and yet you have people always mentioning 
storminess. The cartoon I offer you emphasizes this. It should 
be going down, not up, by the basic physics.
    When you see extremes in weather in any given season, it is 
because the wind changes from the north to south, and the 
extremes you see relate to how cold could a north wind be. That 
depends on how cold the Arctic is and how warm the tropics are. 
In other words, it depends on the pole-to-equator temperature 
difference. We are simultaneously hearing that these extremes 
will increase while the difference goes down. That is 
impossible, so in some sense alarmism has become a very 
important part of the issue, rather than the facts themselves.
    The Kyoto agreement is also something that has been 
presented with utter confusion. I think there is widespread 
agreement that the Kyoto agreement, if adhered to, would have 
very little impact on climate. The estimates are, if you 
expected 4 degrees, you believed such models, you would knock 
it down to about 3.8.
    In part, this is due to the fact that the Kyoto agreement 
applies only to the developed world, but even if extended to 
the whole world, harming the developing world rather severely, 
because that is at the heart of all claims that the developing 
world is more vulnerable. You are always more vulnerable if you 
are poor. You might knock it down from 4 to 3. In other words, 
if you expect severe warming, you will still have severe 
warming, so as a policy in itself, it seemed fairly ill-advised 
and ineffective.
    Now, it has been mentioned that computer models are at the 
basis of much of our understanding, if you can call it that, 
and it is certainly at the basis of scenario-building. It has 
been mentioned, for example, that we are now surer that a large 
part of climate change is due to man. This is based on computer 
models. It is not a verification. You have to assume natural 
and internal variability generated by models is the same as it 
is in nature, and so we have circular projections.
    This is part of our whole scenario system, where you no 
longer ask computer models to be correct. It is widely 
acknowledged that they are not. What you ask instead is that 
the projections be possible, and here the 1992 framework 
convention which we signed commits us to something called a 
precautionary principle, which now says all you have to do is 
suggest something is possible in order to need to act upon it.
    I think that is a rather dangerous procedure, in any event, 
with such things as ill-defined possibilities and so on come to 
the IPCC, and we have heard from two people who participated 
very heavily in it, much more than I did, but there are a 
number of things with the IPCC that you should keep in mind.
    First of all, even the summary, which does not adequately 
represent the text, is encouraging the media, the advocacy 
groups to misrepresent the summary. When the summary offers a 
range, however ill-advised, the media picked it up. When the 
summary says some part may be due to man, this is regarded as a 
smoking gun, even though it says no more than the advertising 
claim, savings up to 40 percent, which in fact permits them to 
overcharge you, so the use of language which conveys different 
meaning to layman and scientist is a serious issue.
    The summary itself glosses over the text. There is no way 
you can conveniently summarize 1,000 pages in 13. With respect 
to the chapter on the physics, we went to considerable pains 
pointing out all the problems of the models. The summary simply 
concludes, understanding of climate processes and their 
incorporation in climate models have improved, including water 
vapor, sea ice dynamics, and ocean heat transport. That is not 
exactly the gist, and certainly with respect to clouds the 
statement was, all models completely fail to replicate clouds.
    The statement that the IPCC represents hundreds of 
scientists does ignore the fact that hundreds of scientists are 
never asked. Each of them works on a few pages. The summary, 
the fact that the summary was worked on by a subset of about--
you told me it was about 10 lead authors out of the hundreds 
ignores the fact that the summary's draft, which was prepared 
by these, itself was significantly changed in Shanghai.
    I can testify that the preparation of the report itself was 
not only contentious, which is normal, but even after people 
with very different views had agreed, there was still pressure 
not to criticize models, to exaggerate the progress, and so on.
    There is the final thing in the document that has such a 
technical importance on policy, that there are examples where 
the full text is modified long after the individual authors 
have signed off. I would say it is a very disturbing fact that 
the text was essentially complete last August, but is released, 
and as far as I know is still not released, long after the 
summary is released.
    In any event, I do not think any of this is surprising. The 
IPCC was created in essence to support the negotiations, and 
without the negotiations, without the alarm, there would be no 
IPCC. It is not unusual that an organization has its own 
interests. The question I would like to go to and finish with 
is, where do we go from here?
    I think it is extremely important in science policy, and 
that is where I have my own provincial interest, that we figure 
out how to support science without providing incentives for 
alarmism. I think you see here today an example that a field 
that promotes alarmism will get added attention. How do we 
assure scientists that they can find out that something is not 
alarming and still have support to figure out how nature works, 
instead of addressing it toward alarmism?
    I think that is something that will definitely benefit 
future generations, the better understanding of nature, and 
this will far outweigh the benefits of any, if any, of ill-
thought-out attempts to regulate nature in the absence of such 
    With respect to policy, I think the National Research 
Council in 1992 had a very lengthy report, Policy Implications 
of Greenhouse Warming, and their main conclusion was, carry out 
only those actions which can be justified independently of any 
putative anthropogenic global warming, and here I would add 
that you not identify things with climate change unless they 
can be shown, unlike Kyoto, to have a significant impact on 
climate, otherwise it just becomes a coat hook.
    Now, looking back at the picture on the first page of my 
testimony, you will notice they always picture emissions as 
being black. Remember that CO2 is odorless and 
invisible, is essential to life, nontoxic, and is a normal 
product of breathing. When you portray it as black, you are 
already misleading the public.
    Thank you.
    [The prepared statement of Dr. Lindzen follows:]
     Prepared Statement of Dr. Richard S. Lindzen, Massachussetts 
                        Institute of Technology
    I wish to thank Senator McCain and the Commerce Committee for the 
opportunity to clarify the nature of consensus and skepticism in the 
Climate Debate. I have been involved in climate and climate related 
research for over thirty years during which time I have held 
professorships at the University of Chicago, Harvard University and 
MIT. I am a member of the National Academy of Sciences, and the author 
or coauthor of over 200 papers and books. I have also been a 
participant in the proceedings of the IPCC (the United Nation's 
Intergovernmental Panel on Climate Change). The questions I wish to 
address are the following: What can we agree on and what are the 
implications of this agreement? What are the critical areas of 
disagreement? What is the origin of popular perceptions? I hope it will 
become clear that the designation, `skeptic,' simply confuses an issue 
where popular perceptions are based in significant measure on misuse of 
language as well as misunderstanding of science. Indeed, the 
identification of some scientists as `skeptics' permits others to 
appear `mainstream' while denying views held by the so-called 
`skeptics' even when these views represent the predominant views of the 
    Climate change is a complex issue where simplification tends to 
lead to confusion, and where understanding requires thought and effort. 
Judging from treatments of this issue in the press, the public has 
difficulty dealing with numerical magnitudes and focuses instead on 
signs (increasing v. decreasing); science places crucial emphasis on 
both signs and magnitudes. To quote the great 19th Century English 
scientist, Lord Kelvin, ``When you can measure what you are speaking 
about and express it in numbers, you know something about it; but when 
you cannot measure it, when you cannot express it in numbers, your 
knowledge is of a meager and unsatisfactory kind.''
    As it turns out, much of what informed scientists agree upon is 
barely quantitative at all:
     that global mean temperature has probably increased over 
the past century,
     that CO2 in the atmosphere has increased over 
the same period,
     that the added CO2 is more likely to have 
caused global mean temperature to increase rather than decrease, and
     that man, like the butterfly, has some impact on climate.
    Such statements have little relevance to policy, unless 
quantification shows significance.
    The media and advocacy groups have, however, taken this agreement 
to mean that the same scientists must also agree that global warming 
``will lead to rising sea waters, droughts and agriculture disasters in 
the future if unchecked'' (CNN). According to Deb Callahan, president 
of the League of Conservation Voters, ``Science clearly shows that we 
are experiencing devastating impacts because of carbon dioxide 
pollution.'' (Carbon dioxide, as a `pollutant' is rather singular in 
that it is a natural product of respiration, non-toxic, and essential 
for life.) The accompanying cartoon suggests implications for severe 
weather, the ecosystem, and presumably plague, floods and droughts (as 
well as the profound politicization of the issue). Scientists who do 
not agree with the catastrophe scenarios are assumed to disagree with 
the basic statements. This is not only untrue, but absurdly stupid.
    Indeed, the whole issue of consensus and skeptics is a bit of a red 
herring. If, as the news media regularly report, global warming is the 
increase in temperature caused by man's emissions of CO2 
that will give rise to rising sea levels, floods, droughts, weather 
extremes of all sorts, plagues, species elimination, and so on, then it 
is safe to say that global warming consists in so many aspects, that 
widespread agreement on all of them would be suspect ab initio. If it 
truly existed, it would be evidence of a thoroughly debased field. In 
truth, neither the full text of the IPCC documents nor even the 
summaries claim any such agreement. Those who insist that the science 
is settled should be required to state exactly what science they feel 
is settled. In all likelihood, it will turn out to be something trivial 
and without policy implications except to those who bizarrely subscribe 
to the so-called precautionary principle--a matter I will return to 
later. (Ian Bowles, former senior science advisor on environmental 
issues at the NSC, published such a remark on 22 April in the Boston 
Globe: ``the basic link between carbon emissions, accumulation of 
greenhouse gases in the atmosphere, and the phenomenon of climate 
change is not seriously disputed in the scientific community.'' I think 
it is fair to say that statements concerning matters of such complexity 
that are not disputed are also likely to be lacking in policy relevant 
content. However, some policymakers apparently think otherwise in a 
cultural split that may be worthy of the late C.P. Snow's attention.)
    The thought that there might be a central question, whose 
resolution would settle matters, is, of course, inviting, and there 
might, in fact, be some basis for optimism. While determining whether 
temperature has increased or not is not such a question, the 
determination of climate sensitivity might be. Rather little serious 
attention has been given to this matter (though I will mention some in 
the course of this testimony). However, even ignoring this central 
question, there actually is much that can be learned simply by sticking 
to matters where there is widespread agreement. For example, there is 
widespread agreement
     that CO2 levels have increased from about 
280ppm to 360ppm over the past century, and, that combined with 
increases in other greenhouse gases, this brings us about half way to 
the radiative forcing associated with a doubling of CO2 
without any evidence of enhanced human misery.
     that the increase in global mean temperature over the past 
century is about 1F which is smaller than the normal interannual 
variability for smaller regions like North America and Europe, and 
comparable to the interannual variability for the globe. Which is to 
say that temperature is always changing, which is why it has proven so 
difficult to demonstrate human agency.
     that doubling CO2 alone will only lead to about 
a 2F increase in global mean temperature. Predictions of greater 
warming due to doubling CO2 are based on positive feedbacks 
from poorly handled water vapor and clouds (the atmosphere's main 
greenhouse substances) in current computer models. Such positive 
feedbacks have neither empirical nor theoretical foundations. Their 
existence, however, suggests a poorly designed earth which responds to 
perturbations by making things worse.
     that the most important energy source for extratropical 
storms is the temperature difference between the tropics and the poles 
which is predicted by computer models to decrease with global warming. 
This also implies reduced temperature variation associated with weather 
since such variations result from air moving from one latitude to 
another. Consistent with this, even the IPCC Policymakers Summary notes 
that no significant trends have been identified in tropical or 
extratropical storm intensity and frequence. Nor have trends been found 
in tornados, hail events or thunder days.
     that warming is likely to be concentrated in winters and 
at night. This is an empirical result based on data from the past 
century. It represents what is on the whole a beneficial pattern.
     that temperature increases observed thus far are less than 
what models have suggested should have occurred even if they were 
totally due to increasing greenhouse emissions. The invocation of very 
uncertain (and unmeasured) aerosol effects is frequently used to 
disguise this. Such an invocation makes it impossible to check models. 
Rather, one is reduced to the claim that it is possible that models are 
     that claims that man has contributed any of the observed 
warming (ie attribution) are based on the assumption that models 
correctly predict natural variability. Such claims, therefore, do not 
constitute independent verifications of models. Note that natural 
variability does not require any external forcing--natural or 
     that large computer climate models are unable to even 
simulate major features of past climate such as the 100 thousand year 
cycles of ice ages that have dominated climate for the past 700 
thousand years, and the very warm climates of the Miocene, Eocene, and 
Cretaceous. Neither do they do well at accounting for shorter period 
and less dramatic phenomena like El Ninos, quasi-biennial oscillations, 
or intraseasonal oscillations--all of which are well documented in the 
data, and important contributors to natural variability.
     that major past climate changes were either uncorrelated 
with changes in CO2 or were characterized by temperature 
changes which preceded changes in CO2 by 100's to thousands 
of years.
     that increases in temperature on the order of 1F are not 
catastrophic and may be beneficial.
     that Kyoto, fully implemented, will have little detectable 
impact on climate regardless of what one expects for warming. This is 
partly due to the fact that Kyoto will apply only to developed nations. 
However, if one expected large global warming, even the extension of 
Kyoto to developing nations would still leave one with large warming.
    None of the above points to catastrophic consequences from 
increasing CO2. Most point towards, and all are consistent 
with minimal impacts. Moreover, the last item provides a definitive 
disconnect between Kyoto and science. Should a catastrophic scenario 
prove correct, Kyoto will not prevent it. If we view Kyoto as an 
insurance policy, it is a policy where the premium appears to exceed 
the potential damages, and where the coverage extends to only a small 
fraction of the potential damages. Does anyone really want this? I 
suspect not. Given the rejection of the extensive US concessions at the 
Hague, it would appear that the Europeans do not want the treaty, but 
would prefer that the US take the blame for ending the foolishness. As 
a practical matter, a large part of the response to any climate change, 
natural or anthropogenic, will be adaptation, and that adaptation is 
best served by wealth.
    Our own research suggests the presence of a major negative feedback 
involving clouds and water vapor, where models have completely failed 
to simulate observations (to the point of getting the sign wrong for 
crucial dependences). If we are right, then models are greatly 
exaggerating sensitivity to increasing CO2. Even if we are 
not right (which is always possible in science; for example, IPCC 
estimates of warming trends for the past twenty years were almost 
immediately acknowledged to be wrong--so too were claims for arctic ice 
thinning ), the failure of models to simulate observations makes it 
even less likely that models are a reliable tool for predicting 
    This brings one to what is probably the major point of 
    Can one trust computer climate models to correctly predict the 
response to increasing CO2?
    As the accompanying cartoon suggests, our experience with weather 
forecasts is not particularly encouraging though it may be argued that 
the prediction of gross climate changes is not as demanding as 
predicting the detailed weather. Even here, the situation is nuanced. 
From the perspective of the precautionary principle, it suffices to 
believe that the existence of a computer prediction of an adverse 
situation means that such an outcome is possible rather than correct in 
order to take `action.' The burden of proof has shifted to proving that 
the computer prediction is wrong. Such an approach effectively deprives 
society of science's capacity to solve problems and answer questions. 
Unfortunately, the incentive structure in today's scientific enterprise 
contributes to this impasse. Scientists associate public recognition of 
the relevance of their subject with support, and relevance has come to 
be identified with alarming the public. It is only human for scientists 
to wish for support and recognition, and the broad agreement among 
scientists that climate change is a serious issue must be viewed from 
this human perspective. Indeed, public perceptions have significantly 
influenced the science itself. Meteorologists, oceanographers, 
hydrologists and others at MIT have all been redesignated climate 
scientists--indicating the degree to which scientists have hitched 
their futures to this issue.
    That said, it has become common to deal with the science by 
referring to the IPCC `scientific consensus.' Claiming the agreement of 
thousands of scientists is certainly easier than trying to understand 
the issue or to respond to scientific questions; it also effectively 
intimidates most citizens. However, the invocation of the IPCC is more 
a mantra than a proper reflection on that flawed document. The 
following points should be kept in mind. (Note that almost all reading 
and coverage of the IPCC is restricted to the highly publicized 
Summaries for Policymakers which are written by representatives from 
governments, NGO's and business; the full reports, written by 
participating scientists, are largely ignored.) In what follows, I will 
largely restrict myself to the report of Working Group I (on the 
science). Working Groups II and III dealt with impacts and responses.
     The media reports rarely reflect what is actually in the 
Summary. The media generally replace the IPCC range of `possible' 
temperature increases with `as much as' the maximum--despite the highly 
unlikely nature of the maximum. The range, itself, assumes, 
unjustifiably, that at least some of the computer models must be 
correct. However, there is evidence that even the bottom of the range 
is an overestimate. (A recent study at MIT found that the likelihood of 
actual change being smaller than the IPCC lower bound was 17 times more 
likely than that the upper range would even be reached, and even this 
study assumed natural variability to be what computer models predicted, 
thus exaggerating the role of anthropogenic forcing.) The media report 
storminess as a consequence despite the admission in the summary of no 
such observed relation. To be sure, the summary still claims that such 
a relation may emerge--despite the fact that the underlying physics 
suggests the opposite. The media's emphasis on increased storminess, 
rising sea levels, etc. is based not on any science, but rather on the 
fact that such features have more graphic impact than the rather small 
increases in temperature. People who have experienced day and night and 
winter and summer have experienced far greater changes in temperature, 
and retirement to the sun belt rather than the Northwest Territory 
represents an overt preference for warmth.
     The summary does not reflect the full document (which 
still has not been released although it was basically completed last 
August). For example, I worked on Chapter 7, Physical Processes. This 
chapter dealt with the nature of the basic processes which determine 
the response of climate, and found numerous problems with model 
treatments--including those of clouds and water vapor. The chapter was 
summarized with the following sentence: ``Understanding of climate 
processes and their incorporation in climate models have improved, 
including water vapour, sea-ice dynamics, and ocean heat transport.''
     The vast majority of participants played no role in 
preparing the summary, and were not asked for agreement.
     The draft of the Policymakers Summary was significantly 
modified at Shanghai. The IPCC, in response to the fact that the 
Policymakers Summary was not prepared by participating scientists, 
claimed that the draft of the Summary was prepared by a (selected) 
subset of the 14 coordinating lead authors. However, the final version 
of the summary differed significantly from the draft. For example the 
draft concluded the following concerning attribution:
    From the body of evidence since IPCC (1996), we conclude that there 
has been a discernible human influence on global climate. Studies are 
beginning to separate the contributions to observed climate change 
attributable to individual external influences, both anthropogenic and 
natural. This work suggests that anthropogenic greenhouse gases are a 
substantial contributor to the observed warming, especially over the 
past 30 years. However, the accuracy of these estimates continues to be 
limited by uncertainties in estimates of internal variability, natural 
and anthropogenic forcing, and the climate response to external 
    The version that emerged from Shanghai concludes instead:
    In the light of new evidence and taking into account the remaining 
uncertainties, most of the observed warming over the last 50 years is 
likely to have been due to the increase in greenhouse gas 
    In point of fact, there may not have been any significant warming 
in the last 60 years. Moreover, such warming as may have occurred was 
associated with jumps that are inconsistent with greenhouse warming.
     The preparation of the report, itself, was subject to 
pressure. There were usually several people working on every few pages. 
Naturally there were disagreements, but these were usually hammered out 
in a civilized manner. However, throughout the drafting sessions, IPCC 
`coordinators' would go around insisting that criticism of models be 
toned down, and that `motherhood' statements be inserted to the effect 
that models might still be correct despite the cited faults. Refusals 
were occasionally met with ad hominem attacks. I personally witnessed 
coauthors forced to assert their `green' credentials in defense of 
their statements.
    None of the above should be surprising. The IPCC was created to 
support the negotiations concerning CO2 emission reductions. 
Although the press frequently refers to the hundreds and even thousands 
of participants as the world's leading climate scientists, such a claim 
is misleading on several grounds. First, climate science, itself, has 
traditionally been a scientific backwater. There is little question 
that the best science students traditionally went into physics, math 
and, more recently, computer science. Thus, speaking of `thousands' of 
the world's leading climate scientists is not especially meaningful. 
Even within climate science, most of the top researchers (at least in 
the US) avoid the IPCC because it is extremely time consuming and non-
productive. Somewhat ashamedly I must admit to being the only active 
participant in my department. None of this matters a great deal to the 
IPCC. As a UN activity, it is far more important to have participants 
from a hundred countries--many of which have almost no active efforts 
in climate research. For most of these participants, involvement with 
the IPCC gains them prestige beyond what would normally be available, 
and these, not surprisingly, are likely to be particularly supportive 
of the IPCC. Finally, judging from the Citation Index, the leaders of 
the IPCC process like Sir John Houghton, Dr. Robert Watson, and Prof. 
Bert Bolin have never been major contributors to basic climate 
research. They are, however, enthusiasts for the negotiating process 
without which there would be no IPCC, which is to say that the IPCC 
represents an interest in its own right. Of course, this hardly 
distinguishes the IPCC from other organizations.
    The question of where do we go from here is an obvious and 
important one. From my provincial perspective, an important priority 
should be given to figuring out how to support and encourage science 
(and basic science underlying climate in particular) while removing 
incentives to promote alarmism. The benefits of leaving future 
generations a better understanding of nature would far outweigh the 
benefits (if any) of ill thought out attempts to regulate nature in the 
absence of such understanding. With respect to any policy, the advice 
given in the 1992 report of the NRC, Policy Implications of Greenhouse 
Warming, remains relevant: carry out only those actions which can be 
justified independently of any putative anthropogenic global warming. 
Here, I would urge that even such actions not be identified with 
climate unless they can be shown to significantly impact the radiative 
forcing of climate. On neither ground--independent justification or 
climatic relevance--is Kyoto appropriate.

    The Chairman. Thank you.
    Dr. Sathaye.

                    UNIVERSITY OF CALIFORNIA

    Dr. Sathaye. Thank you, Mr. Chairman, for inviting me.
    I am a senior scientist at the Lawrence Berkeley National 
Laboratory operated by the University of California. I have 
worked as a Coordinating Lead Author of one of the chapters, 
the Third Assessment Report of the Third Working Group, and I 
have also served in a similar capacity on other IPCC reports 
over the last 7 years or so.
    The main points that I want to make today deal with two 
segments, two time periods, one dealing with the reduction of 
near-term annual greenhouse gas emissions, and the second 
dealing with the long-term stabilization of climate change. 
With regards to the near-term annual greenhouse gas emissions, 
the IPCC concluded that there were many technologies already 
available in the marketplace, which have the potential to 
reduce global greenhouse gas emissions from 2010 to 2020 to 
levels below those of 2000 and this is something you pointed 
out, Mr. Chairman in your statement. About half of the 
reduction potential can be achieved with direct benefits, 
exceeding the direct cost, and the other half at a net direct 
cost of $100 per ton of carbon equivalent.
    Now, this may seem somewhat optimistic and, indeed, if you 
tried to deploy these technologies in the marketplace you would 
encounter a number of different barriers, and these barriers 
include things like subsidized prices, world capital markets, 
lack of access to information and so forth, and we have a whole 
chapter in the IPCC that deals with just these issues. The 
implications of these barriers are that it will take time in 
order to implement the technologies that are available to us, 
and they will add to the cost of implementing these 
technologies as well.
    Let me go on to talk about another aspect of the near-term 
cost, and this deals with a whole array of studies that have 
been done about the cost to various industrial economies if 
they were to meet the levels of emissions constraints specified 
in the Kyoto Protocol. The studies showed that the cost to the 
U.S. economy would range between 0.4 to 2 percent of the U.S. 
GDP in the year 2010.
    Now, there are a number of ways the cost could be reduced 
and this, too, has been referred to earlier. One of the more 
important ways this cost could be reduced is through full 
emissions trading across industrialized countries. Just by that 
approach alone, these costs could be reduced by 50 percent, and 
we have experience with this, with sulphur dioxide trading 
within the United States and, indeed, that was a very effective 
approach to reducing sulphur dioxide emissions from power 
plants in the United States. But the cost can be further 
reduced if you pursue carbon dioxide projects in developing 
countries and also include land use change and forestry options 
in addition to other technologies.
    Now, Dr. Lindzen just mentioned this question about 
pursuing approaches that also address other benefits that you 
might derive from mitigation actions and so if you pursue 
options that also reduce local pollutants, this could have a 
double or joint benefit whereby you achieve reductions in local 
pollutants as well as reduction of greenhouse gases.
    Let me now turn to the second topic, which has to do with 
the stabilization of long-term atmospheric greenhouse gas 
concentrations. What the IPCC report concludes is that in this 
case as well, the technological options that we need in order 
to stabilize climate at levels of 450 parts per million, for 
instance, which is about 20 percent over the levels in the year 
2000, those technological options are known as well, so we are 
not looking for exotic technologies in order to stabilize 
climate change if we decide that that is what we want to do 
over the long term.
    In terms of the cost of achieving such stabilization, it 
will depend upon what stabilization level we pick as well as 
the emissions pathway to that stabilization level, and least-
cost studies show that the lower the stabilization level, the 
more it will reach that level. The lower stabilization level 
means you begin earlier to decrease emissions as well.
    Stabilization will require the participation of all 
countries. All IPCC emission scenarios show one trend 
consistently, that you cannot stabilize unless all countries 
participate in this process. The emission scenarios also 
indicate that conventional oil and gas resources will be 
severely depleted by mid-century or earlier. This is true for 
all emission scenarios that IPCC has looked at, and what this 
implies is that there will be an opportunity, or opportunities 
to shift or make a transition to less-carbon-intensive energy 
sources and technologies as the conventional oil and gas 
resources are depleted.
    Finally, Mr. Chairman, in order to achieve these kinds of 
technological breakthroughs, investments in energy R&D, the 
transfer existing technologies is going to play a critical role 
not just in the United States but worldwide if climate is to be 
    Let me also make a couple of remarks about the IPCC 
process. I think all of us here have participated in that 
process to some degree, and perhaps one thing that is probably 
worth clearing up is that the IPCC is engaged in reviews of 
studies, research studies that have already been done.
    There is no new research being done within the IPCC work, 
and it is completely compatible with national governments, or 
national institutions carrying out research as mandated, or as 
required by governments on their own, and I think this is 
important to remember, that if there was no research done, 
there would be nothing for the IPCC to review.
    The second point about the IPCC is that we are providing 
information to negotiators, but we also are providing 
summarized information to all concerned. It is not just to the 
government, the negotiators. It goes to academics, it goes to 
students, and can be shared with everyone.
    Lastly, you can do studies and nobody ever reads them, they 
go on bookshelves, and you can do studies in which the 
governments participate actively. In the IPCC process there is, 
indeed, some give-and-take, but we make sure that the content 
of the IPCC report remains in the summaries and, given that, I 
think there is a value to that process of consensus-building 
and pulling together this information in a summarized form.
    Let me conclude with that, and thank you again, Mr. 
Chairman for inviting me.
    [The prepared statement of Dr. Sathaye follows:]
   Prepared Statement of Dr. Jayant A. Sathaye\1\, Senior Scientist, 
    Lawrence Berkeley National Laboratory, University of California
    The IPCC WG III review of studies on climate change mitigation 
describes the potential and costs of technologies, practices, and 
policies to (1) reduce near-term annual greenhouse gas (GHG) emissions, 
and (2) stabilize atmospheric GHG concentrations over the long-term.
    \1\ The remarks in this statement represent my personal views, and 
not necessarily those of the Lawrence Berkeley National Laboratory or 
the University of California.
    Reduction of Near-term Annual GHG Emissions:
    1. Significant unanticipated technical progress relevant to 
greenhouse gas reductions has been achieved since the IPCC released its 
Second Assessment Report in 1996.
    2. Technologies such as efficient hybrid engine cars, fuel cells, 
underground carbon dioxide storage, and many others have the potential 
to reduce global GHG emissions in 2010--2020 to below 2000 levels.
    3. In the absence of barriers, studies suggest that about half of 
the above emissions reduction potential can be achieved with direct 
benefits exceeding direct costs, and the other half at a net direct 
cost of up to US $ 100/t Ceq (at 1998 prices). Overcoming barriers such 
as subsidized prices, lack of access to information and financing, and 
ill defined property rights will incur additional costs, which in some 
cases may be substantial.
    4. National responses can be more effective if deployed as a 
portfolio of policy instruments to reduce greenhouse gas emissions.
    5. About a dozen studies based on models of the global economy 
estimate that costs to the US economy of meeting GHG emissions levels 
noted in the Kyoto Protocol vary from 0.4-2.0% of 2010 GDP.
    6. Assuming full GHG emissions trading both within and across 
industrialized countries, these studies show that costs can be reduced 
to less than half the above values.
    7. Costs may be further reduced through implementation of carbon 
offset projects in developing countries, and land use, land-use change 
and forestry (LULUCF) activities, mitigation options that also reduce 
local pollutants, and revenue neutral carbon taxes.
    Stabilization of Long-term (2100+) Atmospheric GHG Concentrations:
    8. Widespread use of known technological options could achieve a 
broad range of atmospheric carbon dioxide stabilization levels such as 
550, 450 ppmv or below (compared to 368 ppmv in 2000) over the next 100 
years or more, if the type of barriers noted in item 3 above could be 
    9. The cost of achieving stabilization will depend on the emissions 
pathway and the targeted stabilization level. Least-cost studies show 
that decreasing the stabilization target makes annual emissions peak 
earlier and at lower levels before beginning a gradual decline, and 
vice versa. Estimated costs of stabilizing carbon dioxide 
concentrations increase steeply as the level declines below 550 ppmv.
    10. Stabilization will require the participation of all countries. 
Two-thirds of IPCC Post-SRES scenarios show that annual GHG emissions 
per capita from industrialized countries decline to levels below those 
of developing countries by 2050.
    11. IPCC emissions scenarios indicate a severe depletion of 
conventional oil and gas resources by mid-century or earlier. This 
offers an opportunity for a transition to less-carbon-intensive energy 
sources and technologies.
    12. Investment in energy R&D, the transfer and adoption of existing 
technology, and technological and social innovation will be required to 
foster the penetration of these energy sources and improved 
                        results and conclusions
    Mr. Chairman, thank you for inviting me to speak about the findings 
of the Working Group (WG) III on Climate Change 2001: Mitigation of the 
Intergovernmental Panel on Climate Change (IPCC). I served as a 
Coordinating Lead Author of the Chapter on Barriers, Opportunities, and 
Market Potential of Technologies and Practices of the WG III report, 
and an author of the Synthesis Report, and have participated in the 
discussions and writing of their Summaries for Policy Makers (SPM). My 
remarks today are based largely on the SPM findings and the contents of 
the underlying report. In this statement, I have focused on the near- 
and long-term potential for, and costs and benefits of, reducing 
reenhouse gas emissions.
    1. There are many low cost technological options to reduce near-
term emissions, but barriers to their deployment exist.
    Significant technical progress relevant to the potential for 
greenhouse gas emission reductions has been made since 1995 and has 
been faster than anticipated. Net emissions reductions could be 
achieved through, inter-alia, improved production and use of energy, 
shift to low- or no-carbon technologies, carbon removal and storage, 
and improved land-use, land-use change and forestry (LULUCF) practices. 
Relevant advances are taking place in a wide range of technologies at 
different stages of development, ranging from the market introduction 
of efficient hybrid engine cars to the advancement of fuel cell 
technology, and the demonstration of underground carbon dioxide 
    The successful implementation of greenhouse gas mitigation options 
would need to overcome many technical, economic, political, cultural, 
social, behavioral and/or institutional barriers which prevent the full 
exploitation of the technological, economic and social opportunities of 
these mitigation options (Figure 1). The potential mitigation 
opportunities and types of barriers vary by region and sector, and over 
time. In the industrialized countries, future opportunities lie 
primarily in removing social and behavioral barriers, in countries with 
economies in transition, in price rationalization; and in developing 
countries, in price rationalization, increased access to data and 
information, availability of advanced technologies, financial 
resources, and training and capacity building. Most countries could 
benefit from innovative financing and institutional reform and removing 
barriers to trade.
    National responses to climate change can be more effective if 
deployed as a portfolio of policy instruments to limit or reduce 
greenhouse gas emissions. The portfolio may include--according to 
national circumstances- emissions/carbon/energy taxes, tradable or non-
tradable permits, subsidies, deposit/refund systems, technology or 
performance standards, product bans, voluntary agreements, government 
spending and investment, and support for research and development.
    Annual global emissions reductions of 1.9-2.6 GtCeq, and 3.6--5.0 
GtCeq per year could be achieved by 2010 and 2020 respectively, with 
half of these reductions being realized with direct benefits exceeding 
direct costs, and the other half at a net direct cost of up to US$100/
tCeq (at 1998 prices). Depending on the emissions scenario this could 
allow global emissions to be reduced below 2000 levels in 2010-2020 
(Table 1). These cost estimates are derived using discount rates in the 
range of 5 to 12 percent, consistent with public sector discount rates, 
but lower than private internal rates of return, thus affecting the 
rate of adoption of these technologies by private entities. Realising 
these reductions involves, among other things, additional 
implementation costs, which in some cases may be substantial, the 
possible need for supporting policies, increased research and 
development, and effective technology transfer.
    2. Based on models of the global economy the cost estimates of 
meeting GHG emissions levels noted in the Kyoto Protocol vary 
considerably both within and across regions.
    Models show that the Kyoto mechanisms can reduce costs to Annex 
II\2\ countries. Global modeling studies show national marginal costs 
to meet the Kyoto emissions levels range from about US$20/tC up to 
US$600/tC without trading, and from about US$15/tC up to US$150/tC with 
Annex B\3\ trading. Figure 2 shows the range of GDP losses estimated in 
these studies in 2010. The cost reductions and GDP losses from these 
mechanisms may depend on the details of implementation, including the 
compatibility of domestic and international mechanisms, constraints, 
and transaction costs. These costs can be further reduced through use 
of the Clean Development Mechanism, LULUCF activities, by including the 
non-carbon dioxide gases, identifying and implementing options that 
produce ancillary benefits, and identifying double dividend 
opportunities, e.g., carbon taxes or auctioned permits may be used to 
finance reductions in existing distortionary taxes, reducing the 
economic cost of achieving greenhouse gas reductions.
    \2\ Annex II: Countries listed in the Annex II of the UN Framework 
Convention on Climate Change. Annex II list includes the United States 
and 23 other original members of the Organization for Economic 
Cooperation and Development (OECD), plus the European Union.
    \3\ Annex B: Annex I countries that are listed in the Kyoto 
Protocol to take on commitments to limit their emissions.
    Emission constraints in Annex I\4\ countries have well established, 
albeit varied ``spill over'' effects on non-Annex I countries, 
    \4\ Annex I: Annex II countries plus the countries designated as 
Economies in Transition.
    Oil-exporting, non-Annex I countries: The study reporting the 
lowest costs, reported reductions in projected GDP of 0.2% with no 
emissions trading, and less than 0.05% with Annex B emissions trading 
in 2010. The study reporting the highest costs shows reductions of 
projected oil revenues of 25% with no emissions trading, and 13% with 
Annex B emissions trading in 2010.
    Other non-Annex I countries may be adversely affected by reductions 
in demand for their exports to OECD nations and by the price increase 
of those carbon-intensive and other products they continue to import, 
but may benefit from the reduction in fuel prices, increased exports of 
carbon-intensive products and the transfer of environmentally sound 
technologies and know how.
    3. Technology development and diffusion are an important component 
of cost-effective stabilization.
    Transfer of existing technologies and the development and transfer 
of new technologies could play a critical role in reducing the cost of 
stabilizing greenhouse gas concentrations. Transfer of technologies 
between countries and regions could widen the choice of options at the 
regional level and economies of scale and learning will lower the costs 
of their adoption. Governments through sound economic policy, and 
regulatory frameworks, transparency and political stability could 
create an enabling environment for private and public sector technology 
transfers and adequate human and organizational capacity is essential 
at every stage to increase the flow, and improve the quality, of 
technologies. In addition, networking among private and public 
stakeholders, and focusing on products and techniques with multiple 
ancillary benefits, that meet or adapt to local needs and priorities, 
is essential for most effective technology transfers.
    IPCC emissions scenarios indicate that conventional oil and gas 
resources will be mostly used up by mid-century irrespective of actions 
to address climate change (Figure 3). This will necessitate a different 
pattern of energy resource development and an increase in energy R&D 
with the goal of accelerating the development and deployment of 
advanced energy technologies.  Given that the carbon in proven 
conventional oil and gas reserves, or in conventional oil resources, is 
limited, this may imply a change in the energy mix and the introduction 
of new sources of energy during the 21st century. If so, the choice of 
energy mix and associated investment will determine whether, and if so, 
at what level and cost, greenhouse concentrations can be stabilized. 
Opportunities that exist in the near term are the fruits of past 
investments in energy R&D; therefore, further investments in energy R&D 
will be required to maintain the flow of improved energy technologies 
throughout the 21st century.
    Technological and social innovation could raise the social and 
economic potential of mitigation options beyond that of current 
markets. In the longer term, such innovations may shift preferences and 
cultural norms towards lower-emitting and sustainable behaviors.
    4. Both the pathway to stabilization of atmospheric GHG 
concentrations and the stabilization target itself are key determinants 
of mitigation costs
    Stabilization levels depend more on cumulative rather than year-by-
year emissions. A gradual near-term transition away from the world's 
present energy system towards a less carbon-emitting economy minimizes 
costs associated with premature retirement of existing capital stock 
and provides time for technology development, and avoids premature 
lock-in to early versions of rapidly developing low-emission 
technology, where-as more rapid near-term action would decrease 
environmental and human risks associated with projected changes in 
climate and may stimulate more rapid deployment of existing low-
emission technologies and provide strong near-term incentives to future 
technological changes.
    Studies show that the costs of stabilizing carbon dioxide 
concentrations in the atmosphere increase as the stabilization level 
declines (Figure 4). While there is a moderate increase in the costs 
when passing from a 750 ppm to a 550 ppm concentration stabilization 
level, there is a larger increase in costs passing from 550 ppm to 450 
ppm unless the emissions in the baseline scenario are very low. 
However, these studies did not incorporate carbon sequestration, non-
carbon dioxide gases and did not examine the possible effect of more 
ambitious targets on induced technological change.
    Countries and regions will have to choose their own path to a low 
emissions future, where decision-making is essentially a sequential 
process under uncertainty. Most model results indicate that known 
technological options could achieve a broad range of atmospheric carbon 
dioxide stabilization levels, such as 550 ppm or 450 ppm and below over 
the next 100 years or more, but implementation would require associated 
socio-economic and institutional changes. However, no single sector or 
technology option could provide all of the emissions reductions needed. 
A prudent risk management strategy requires a careful consideration of 
the economic and environmental consequences, their likelihood and 
society's attitude toward risk.
    Stabilization of atmospheric GHG levels will require the 
participation of all countries in the long term. Two-thirds of IPCC 
Post-SRES scenarios show that annual GHG emissions per capita from 
industrialized countries decline to levels below those of developing 
countries by 2050.





    The Chairman. Thank you very much.
    Dr. Hansen, welcome.


    Dr. Hansen. Thank you, Mr. Chairman.
    I will talk about future climate. The most popular climate 
projection is the business-as-usual scenario. It leads to 
dramatic climate change later in the century. It provides a 
useful warning of what is possible if greenhouse gases grow 
more and more rapidly.
    Four of my colleagues and I recently described an 
alternative scenario for climate change in the 21st Century 
which we think is a useful complement to the business-as-usual 
scenario. We assert that a brighter climate future is not only 
possible but can be achieved with actions that make good sense, 
independent of global warming.
    This alternative scenario can be explained with the help of 
my bar chart for the forcing agents that underlie climate 
change. These are the climate forcings that exist today, 
relative to 1850. Carbon dioxide is the largest climate-forcing 
at 1.4 watts per meter squared, but these other greenhouse 
gases, methane, CFC's, low-level ozone, and nitrous oxide 
together cause a forcing that is equally as large. Methane, 
when you include its effects on other gases, causes a forcing 
half as large as CO2, and then there are these 
aerosols. Aerosols are fine particles in the atmosphere, liquid 
or solid particles.
    Black carbon, which comes from diesel fuel and coal-
burning, causes a warming. Sulphate and organic carbon, which 
come from fossil fuel burning, cause cooling. All of these 
particles have some effect on cloud properties, which tends to 
cause a cooling. However, it is rather uncertain, the magnitude 
of that cooling.
    The question is, how will these forcings change in the 
future? We could keep the additional climate forcing the next 
50 years as small as 1 watt per meter squared by means of two 
actions. First, we must stop any further net growth of the non-
CO2 forcings, several of which are air pollution. 
Their growth needs to be stopped anyhow for reasons of public 
health. Second, CO2 emissions can continue, but the 
emissions rate should be no larger than it is today, preferably 
declining slowly. The resulting forcing of 1 watt would be 
expected to cause some climate change, but less than 1 degree 
Celsius warming in 50 years.
    So how can we stop the growth of these non-CO2 
forcings? Black carbon is a product of incomplete combustion. 
You can see it in the exhaust of diesel trucks. The microscopic 
particles are like tiny sponges. They soak up toxic organics 
and other aerosols. They are so tiny that when breathed in they 
penetrate human tissue deeply. Some of the smallest enter the 
bloodstream. These particulates cause respiratory and cardiac 
problems, asthma, acute bronchitis. With tens of thousands of 
deaths per year in the United States, also in Europe, where the 
health costs of particulate air pollution has been estimated at 
1.6 percent of the gross domestic products.
    In the developing world the costs are staggering. In India, 
approximately 270,000 children under the age of 5 die per year 
from acute respiratory infections caused by air pollution. Most 
of that pollution arises in household burning of field residue, 
cow dung, biomass, coal, for cooking and heating. There is now 
a brown cloud of pollution mushrooming from India. You can see 
it against the Himalayas.
    There is a similar story for ozone. It is a pollutant that 
causes tens of billions of dollars of damage. We could stop its 
further growth. We have the technology to do that.
    There is a somewhat different story for methane, but there 
are practical steps that could be taken to stop the growth of 
methane also.
    The bottom line is that we have only one atmosphere, and it 
is a global atmosphere. My personal opinion is that we need to 
reduce the pollution that we are putting into it for a number 
of reasons, especially human health, and in the process we can 
help prevent the non-CO2 climate forcing from 
    In the United States, for example, we could reduce diesel 
emissions and other soot emissions. We might also work with 
developing countries to help reduce their pollution. One 
possible long-term solution there would be electrification, a 
source of clean energy.
    Finally, I must also address CO2. It is the 
hardest part of the problem, but not as hard as it is often 
made out to be. In 1998, global CO2 emissions 
declined slightly. In 1999 CO2 emissions declined 
again. In 2000 I believe that they declined again, but the 
numbers are not yet in.
    The Chairman. Doctor, why did those emissions decline?
    Dr. Hansen. The primary reason was China. Choking on its 
pollution, it reduced the amount of coal-burning, replaced coal 
power plants with gas power plants. Emissions from the United 
States actually increased in those years, but there are other 
countries where they are making efforts at renewable energies, 
and that is having some effect.
    The Chairman. Thank you.
    Dr. Hansen. Now, that is just the trend that is needed to 
achieve our alternative scenario with only moderate climate 
change. In the near term, my opinion is that this trend can be 
maintained via concerted efforts toward increased energy 
efficiency and increased use of renewable energy sources. On 
the long-term, most energy experts suggest that we would need a 
significant increasing contribution from some energy source 
that produces little or no CO2.
    In my written testimony, I note several possibilities, 
which include zero emission coal, nuclear power, and a 
combination of solar energy and hydrogen and fuel cells. Each 
possibility has pros and cons, and I am not recommending 
policy. R&D is needed. It will be up to the public, via their 
representatives, to make choices. My point is that such 
possibilities exist, so the concept of the alternative scenario 
with only a modest climate change is a viable possibility.
    Thank you. I would like to include in the record copies of 
my final three references in my official testimony. These 
discuss this topic in more detail, but in a plain language, 
which I think might be helpful.
    [The prepared statement of Dr. Hansen follows:]
Prepared Statement of Dr. James E. Hansen, Director, Goddard Institute 
    for Space Studies, National Aeronautics and Space Administration
                               1. preface
    Mr. Chairman and Members of the Committee: I appreciate the 
opportunity to clarify the paper I co-authored with four other 
scientists on climate change in the 21st century, published in 
Proceedings of the National Academy of Sciences (1). In that paper, we 
define an ``alternative scenario'' for the forcing agents that cause 
climate change. The alternative scenario gives equal emphasis to 
reducing air pollution and to a continued slow downtrend in CO2 
emissions. This scenario produces only a moderate climate change in the 
next 50 years. We suggest that the climate forcings in this scenario 
can be achieved via pragmatic actions that make good sense for a 
variety of reasons. Collateral benefits include improvements in human 
health, agricultural productivity, and greater energy self-sufficiency. 
Our alternative scenario differs markedly from the ``business as 
usual'' scenarios of the Intergovernmental Panel on Climate Change 
(IPCC), which have received the greatest attention among the plethora 
of IPCC scenarios. However, I emphasize that our paper is not a 
criticism of IPCC. The IPCC reports (2), produced by hundreds of 
outstanding scientists, provide an invaluable assessment of the status 
of scientific understanding of climate change.
    Although our research has relevance to public issues, it is not our 
job to suggest policies. Our objective is to provide scientific 
information that the public and their representatives can use to help 
choose wise policies. Thus our aim is to provide relevant information 
on the forcing agents that drive climate change that is as quantitative 
and as clear as the data permit.
                    2. introduction: basic concepts
    The Earth's climate fluctuates from year to year and century to 
century, just as the weather fluctuates from day to day. It is a 
chaotic system, so changes occur without any forcing, but the chaotic 
changes are limited in magnitude. The climate also responds to 
forcings. If the sun brightens, a natural forcing, the Earth becomes 
warmer. If a large volcano spews aerosols into the stratosphere, these 
small particles reflect sunlight away and the Earth tends to cool. 
There are also human-made forcings.
    We measure forcings in watts per square meter (W/m2). 
For example, all the human-made greenhouse gases now cause a forcing of 
more than 2 W/m2. It is as if we have placed two miniature 
Christmas tree bulbs over every square meter of the Earth's surface. 
That is equivalent to increasing the brightness of the sun by about 1 
    We understand reasonably well how sensitive the Earth's climate is 
to a forcing. Our most reliable measure comes from the history of the 
Earth. We can compare the current warm period, which has existed 
several thousand years, to the previous ice age, about 20,000 years ago 
(3, 4, 5). We know the composition of the atmosphere during the ice age 
from bubbles of air that were trapped as the ice sheets on Greenland 
and Antarctica built up from snowfall. There was less carbon dioxide 
(CO2) and less methane (CH4), but more dust in 
the air. The surface was different then, with ice sheets covering 
Canada and parts of Europe, different distributions of vegetation, even 
the coast-lines differed because sea level was 300 feet lower. These 
changes, as summarized in Figure 1, caused a negative climate forcing 
of about 6\1/2\ W/m2. That forcing maintained a planet that 
was 5+ C colder than today. This empirical information implies that 
climate sensitivity is about \3/4\+ C per watt of forcing. Climate 
models have about the same sensitivity, which provides encouraging 
agreement between the real world and the complex computer models that 
we use to predict how climate may change in the future.
    There is another important concept to understand. The climate 
cannot respond immediately to a forcing, because of the long time 
needed to warm the ocean. It takes a few decades to achieve just half 
of the equilibrium climate response to a forcing. Even in 100 years the 
response may be only 60-90 percent complete (5). This long response 
time complicates the problem for policy-makers. It means that we can 
put into the pipeline climate change that will only emerge during the 
lives of our children and grandchildren. Therefore we must be alert to 
detect and understand climate change early on, so that the most 
appropriate policies can be adopted.
              3. past climate forcings and climate change
    The climate forcings that exist today are summarized in Figure 2 
(1). The greenhouse gases, on the left, have a positive forcing, which 
would tend to cause warming. CO2 has the largest forcing, 
but CH4, when its indirect effect on other gases is 
included, causes a forcing half as large as that of CO2. 
CO2 is likely to be increasingly dominant in the future, but 
the other forcings are not negligible.
    Aerosols, in the middle of the figure, are fine particles in the 
air. Some of these, such as sulfate, which comes from the sulfur 
released in coal and oil burning, are white, so they scatter sunlight 
and cause a cooling. Black carbon (soot) is a product of incomplete 
combustion, especially of diesel fuel and coal. Soot absorbs sunlight 
and thus warms the planet. Aerosols tend to increase the number of 
cloud droplets, thus making the clouds brighter and longer-lived. All 
of the aerosol effects have large uncertainty bars, because our 
measurements are inadequate and our understanding of aerosol processes 
is limited.
    If we accepted these estimates at face value, despite their large 
uncertainties, we would conclude that, climate forcing has increased by 
1.7 W/m2 since the Industrial Revolution began [the error 
bars, in some cases subjective, yield an uncertainty in the net forcing 
of 1 W/m2]. The equilibrium warming from a forcing of 1.7 W/
m2 is 1.2-1.3+ C. However, because of the ocean's long 
response time, we would expect a global warming to date of only about 
\3/4\+ C. An energy imbalance of 0.7 W/m2 remains with that 
much more energy coming into the planet than going out. This means 
there is another \1/2\+ C global warming already in the pipeline--it 
will occur even if atmospheric composition remains fixed at today's 
    The climate forcings are known more precisely for the past 50 
years, especially during the past 25 years of satellite measurements. 
Our best estimates are shown in Figure 3. The history of the 
tropospheric aerosol forcing, which involves partial cancellation of 
positive and negative forcings, is uncertain because of the absence of 
measurements. However, the GHG and stratospheric aerosol forcings, 
which are large forcings during this period, are known accurately.
    When we use these forcings in a global climate model (3) to 
calculate the climate change (6), the results are consistent with 
observations (Figure 4). We make five model runs, because of the chaos 
in the climate system. The red curve is the average of the five runs. 
The black dots are observations. The Earth's stratosphere cools as a 
result of ozone depletion and CO2 increase, but it warms 
after volcanic eruptions. The troposphere and the surface warm because 
of the predominantly positive forcing by increases of greenhouse gases, 
in reasonably good agreement with observations.
    The fourth panel in Figure 4 is important. It shows that the 
simulated planet has an increasing energy imbalance with space. There 
is more energy coming into the planet, from the sun, than there is 
energy going out. The calculated imbalance today is about 0.7 W/
m2. This, as mentioned above, implies that there is about 
0.5+ C additional global warming already in the pipeline, even if the 
atmospheric composition does not change further. An important 
confirmation of this energy imbalance has occurred recently with the 
discovery that the deep ocean is warming. That study (7) shows that the 
ocean took up heat at an average rate of 0.3 W/m2 during the 
past 50 years, which is reasonably consistent with the predictions from 
climate models. Observed global sea ice cover has also decreased as the 
models predict.
    There are many sources of uncertainty in the climate simulations 
and their interpretation. Principal among the uncertainties are climate 
sensitivity (the Goddard Institute for Space Studies model sensitivity 
is 3+ C for doubled CO2, but actual sensitivity could be as 
small as 2+ C or as large as 4+ C for doubled CO2), the 
climate forcing scenario (aerosol changes are very poorly measured), 
and the simulated heat storage in the ocean (which depends upon the 
realism of the ocean circulation and mixing). It is possible to find 
other combinations of these ``parameters'' that yield satisfactory 
agreement with observed climate change. Nevertheless, the observed 
positive heat storage in the ocean is consistent with and provides some 
confirmation of the estimated climate forcing of 1.7  1 W/
m2. Because these parameters in our model are obtained from 
first principles and are consistent with our understanding of the real 
world, we believe that it is meaningful to extend the simulations into 
the future, as we do in the following section. Such projections will 
become more reliable and precise in the future if we obtain better 
measurements and understanding of the climate forcings, more accurate 
and complete measures of climate change, especially heat storage in the 
ocean, and as we employ more realistic climate models, especially of 
ocean circulation.
                       4. scenarios for 2000-2050
    We extend our climate model simulations into the future for two 
climate forcing scenarios shown in Figure 5. In the popular ``business-
as-usual'' scenario, which the media focuses upon, the climate forcing 
increases by almost 3 W/m2 in the next 50 years. This leads 
to additional global warming of about 1.5+ C by 2050 and several 
degrees by 2100. Such a scenario, with exponential growth of the 
greenhouse forcing, leads to predictions of dramatic climate change and 
serious impacts on society.
    The ``alternative scenario'' assumes that global use of fossil 
fuels will continue at about today's rate, with an increase of 75 ppm 
in airborne CO2 by 2050. Depending on the rate of CO2 
uptake by the ocean and biosphere this may require a small downtrend in 
CO2 emissions, which would be a helpful trend for obtaining 
climate stabilization later in the century. The alternative scenario 
also assumes that there will be no net growth of the other forcings: in 
somewhat over-simplified terminology, ``air pollution'' is not allowed 
to get any worse that it is today. The added climate forcing in the 
alternative scenario is just over 1 W/m2 in the next 50 
    The alternative scenario results in an additional global warming in 
the next 50 years of about \3/4\+ C, much less than for the business-
as-usual scenario. In addition, the rate of stratospheric cooling 
declines in the alternative scenario (top panel of Figure 5), and in 
fact the lower stratospheric temperature would probably level out 
because of expected stratospheric ozone recovery (not included in this 
simulation). The planetary energy imbalance increases by only about \1/
4\ W/m2 in the alternative scenario, compared with almost 1 
W/m2 in the business-as-usual scenario. In other words, our 
children will leave their children a debt (\3/4\+ C additional warming 
in the pipeline) that is only slightly more than the amount of 
unrealized warming (\1/2\+ C) hanging over our heads now.
    Figure 6 is a cartoon summarizing the two parts of the alternative 
scenario. First, the scenario keeps the added CO2 forcing at 
about 1 W/m2, which requires that annual increases in 
atmospheric CO2 concentrations be similar to those in the 
past decade. The precise scenario that we employ has the CO2 
growth rate declining slowly during these 50 years, thus making it more 
feasible to achieve still lower growth rates in the second half of the 
century and an eventual ``soft landing'' for climate change. Second, 
the net growth of other climate forcings is assumed to cease. The most 
important of these ``other'' forcings are methane, tropospheric ozone, 
and black carbon aerosols. Specific trace gas scenarios used in our 
global climate model simulations are shown in Figure 7.
    In the following two sections we provide data that helps provide an 
indication of how difficult or easy it may be to achieve the elements 
of the alternative scenario.
                 5. alternative scenario: air pollution
    One of the two requirements for achieving the alternative scenario 
is to stop the growth of non-CO2 forcings. Principally, that 
means to halt, or even better reverse, the growth of black carbon 
(soot), tropospheric ozone (O3) and methane 
(CH4). These can loosely be described as air pollution, 
although in dilute amounts methane is not harmful to health. Black 
carbon, with adsorbed organic carbon, nitrates and sulfates, and 
tropospheric ozone are principal ingredients in air pollution.
    Black carbon (soot). Black carbon aerosols, except in the extreme 
case of exhaust puffs from very dirty diesel trucks or buses, are 
invisibly small particles. They are like tiny sponges that soak up 
toxic organic material that is also a product of fossil fuel 
combustion. The aerosols are so small that they penetrate human tissue 
deeply when breathed into the lungs, and some of the tiniest particles 
enter the blood stream. Particulate air pollution, including black 
carbon aerosol, has been increasingly implicated in respiratory and 
cardiac problems. A recent study in Europe (8) estimated that air 
pollution caused annually 40,000 deaths, 25,000 new cases of chronic 
bronchitis, 290,000 episodes of bronchitis in children, and 500,000 
asthma attacks in France, Switzerland and Austria alone, with a net 
cost from the human health impacts equal to 1.6 percent of their gross 
domestic product. Pollution levels and health effects in the United 
States are at a comparable level. Primary sources of black carbon in 
the West are diesel fuels and coal burning.
    The human costs of particulate air pollution in the developing 
world are staggering. A study recently published (9) concluded that 
about 270,000 Indian children under the age of five die per year from 
acute respiratory infections arising from particulate air pollution. In 
this case the air pollution is caused mainly by low temperature 
inefficient burning of field residue, cow dung, biomass and coal within 
households for the purpose of cooking and heating. Pollution levels in 
China are comparably bad, but in China residential coal use is the 
largest source, followed by residential use of biofuels (10).
    Referring back to Figure 2, note that there are several aerosols 
that cause cooling, in addition to black carbon that causes warming. 
There are ongoing efforts to slow the growth of sulfur emissions or 
reduce emissions absolutely, for the purpose of reducing acid rain. In 
our alternative scenario for climate forcings, it is assumed that any 
reduced sulfate cooling will be at least matched by reduced black 
carbon heating. Principal opportunities in the West are for cleaner 
more efficient diesel motors and cleaner more efficient coal burning at 
utilities. Opportunities in the developing world include use of biogas 
in place of solid fuels for household use, and eventually use of 
electrical energy produced at central power plants.
    Ozone (O3). Chemical emissions that lead to tropospheric 
ozone formation are volatile organic compounds and nitrogen oxides 
(carbon monoxide and methane also contribute). Primary sources of these 
chemicals are transportation vehicles, power plants and industrial 
    High levels of ozone have adverse health and ecosystem effects. 
Annual costs of the impacts on human health and crop productivity are 
each estimated to be on the order of $10 billion per year in the United 
States alone.
    Ozone in the free troposphere can have a lifetime of weeks, and 
thus tropospheric ozone is at least a hemispheric if not a global 
problem. Emissions in Asia are projected to have a small effect on air 
quality in the United States (11). Closer neighbors can have larger 
effects, for example, recent ozone increases in Japan are thought to be 
due in large part to combustion products from China, Korea and Japan 
(12). A coordinated reduction of those chemical emissions that lead to 
the formation of low level ozone would be beneficial to developing and 
developed countries.
    Our alternative scenario assumes that it will be possible, at 
minimum, to stop further growth of tropospheric ozone. Recent evidence 
suggests that tropospheric ozone is decreasing downwind of regions such 
as Western Europe (13), where nitrogen oxide and carbon monoxide 
emissions are now controlled, but increasing downwind of East Asia 
(12). Global warming may aggravate summer time ozone production, but 
this feedback effect would be reduced with the small warming in the 
alternative scenario. The evidence suggests that cleaner energy sources 
and improved combustion technology could achieve an overall ozone 
    Methane (CH4). Methane today causes a climate forcing 
half as large as that of CO2, if its indirect effects on 
stratospheric H2O and tropospheric O3 are 
included. The atmospheric lifetime of CH4 is moderate, only 
8-10, years, so if its sources were reduced, the atmospheric amount 
would decline rather quickly. Therefore it offers a great opportunity 
for a greenhouse gas success story. It would be possible to stabilize 
atmospheric CH4 by reducing the sources by about 10%, and 
larger reductions could bring an absolute decrease of atmospheric 
CH4 amount.
    The primary natural source of methane is microbial decay of organic 
matter under anoxic conditions in wetlands. Anthropogenic sources, 
which in sum may be twice as great as the natural source, include rice 
cultivation, domestic ruminants, bacterial decay in landfills and 
sewage, leakage during the mining of fossil fuels, leakage from natural 
gas pipelines, and biomass burning.
    There are a number of actions that could be taken to reduce 
CH4 emissions: (1) capture of methane in coal mining, 
landfills, and waste management, (2) reduction of pipeline leakage, 
especially from antiquated systems such as in the former Soviet Union, 
(3) reduction of methane from ruminants and rice growing, as the 
farmers' objectives are to produce meat, milk and power from the 
animals, not methane, and food and fiber from the fields, not methane.
    The economic benefits of such methane reductions are not so great 
that they are likely to happen automatically. Methane reduction 
probably requires international cooperation, including developing 
countries. Although the task is nontrivial, it represents an 
opportunity for a success story. In some sense, methane in climate 
change is analogous to the role of methyl-chloroform in ozone 
depletion. Although the growth of long-lived chlorofluorocarbons has 
only begun to flatten out, stratospheric chlorine is already declining 
in amount because of reductions in the sources of short-lived methyl-
                6. alternative scenario: carbon dioxide
    CO2 is the largest single human-made climate forcing 
agent today, and its proportion of the total human-made climate forcing 
can be anticipated to increase in the future. It is not practical to 
stop the growth of atmospheric CO2 in the next several 
decades. However, it is possible to slow the growth rate of CO2 
emissions via actions that make good economic and strategic sense.
    Scenarios for CO2 are commonly constructed by making 
assumptions about population growth, standard of living increases, fuel 
choices, and technology. This procedure yields a huge range of 
possibilities with little guidance as to what is likely. An alternative 
approach is to examine historical and current rates of change of 
CO2 emissions, estimate the changes that are needed to keep 
the climate change moderate, and consider actions that could produce 
such rates of change. That is the procedure we explore here.
    Fossil-fuel CO2 emissions. Figures 8 and 9 show U.S. and 
global CO2 emissions. Emissions in the U.S. grew faster in 
the 1800s than in the rest of the world, as the U.S. itself was still 
growing and had rapid immigration. Growth of U.S. emissions was slower 
than in the rest of the world during the second half of the 20th 
century, when other parts of the world were industrializing.
    The important period for the present discussion is the past 25 
years, and the past decade. The U.S. growth rate was 1%/year over the 
past 25 years, as we largely succeeded in decoupling economic and 
energy use growth rates. The global growth rate was moderately higher, 
1.4%, as there was faster growth in developing nations. However, in the 
past decade the growth rate of U.S. CO2 emissions has been 
higher than in the world as a whole (1%/year in the U.S. vs. 0.6%/year 
in the world).
    Figure 10 provides a useful summary. The U.S. portion of global 
fossil fuel CO2 emissions increased from 10% in 1850 to 50% 
in 1920. Since then the U.S. portion has declined to 23% as other parts 
of the world industrialized. The temporary spike beginning in 1940 is 
associated with World War II, including vigorous exertion of U.S. 
industry to supply the war effort. In the 1990s the U.S. portion of 
global emissions increased, despite oratory about possible climate 
change and expectations that the developing world would be the source 
of increasing emissions.
    Growth rate required for ``alternative scenario''. A small change 
in the CO2 emissions growth rate yields large changes in 
emissions several decades in the future. A 1%/year growth yields a 64% 
growth of emissions in 50 years, compared with constant emissions (0%/
year growth rate). A growth rate of -0.5%/year yields a -22% change of 
emissions in 50 years. Thus CO2 emissions in 50 years are 
more than twice as large in a 1%/year scenario than in a -0.5%/year 
    Incomplete understanding of the Earth's ``carbon cycle'' creates 
some uncertainty, but to a good approximation the increase in 
atmospheric CO2 is commensurate with the CO2 
emission rate. Therefore full achievement of the ``alternative 
scenario'' probably requires the global CO2 emissions growth 
rate to be approximately zero or slightly negative over the next 50 
    Even if the United States achieves a zero or slightly negative 
growth rate for CO2 emissions, there is no guarantee that 
the rest of the world will follow suit. However, the economic and 
strategic advantages of a more energy efficient economy are sufficient 
to make this path attractive to most countries. It is likely that the 
shape of the U.S. and global CO2 emissions curves will 
continue to be fundamentally congruent. In any case, any strategy for 
achieving a climate change ``soft landing'', whether pursued 
unilaterally or otherwise, surely requires that the downward change in 
the U.S. CO2 emission growth rates be at least comparable to 
the change needed in the global average. There are many reasons for the 
United States to aggressively pursue the technology needed to achieve 
reduced CO2 emissions, including potential economic benefit 
and reduced dependence on foreign energy sources.
    It is not our task to suggest specific policies. However, we must 
make the case that there are options for achieving the slower CO2 
growth rate. Otherwise the alternative scenario is not viable.
    In the short-term, a case can be made that pent-up slack in energy 
efficiency (14), if pursued aggressively, can help achieve a zero or 
slightly negative CO2 emissions growth rate. Renewable 
energy sources, even though their output is relatively small, also can 
contribute to slowing the growth rate of emissions. There has been 
resistance of some industries to higher efficiency requirements. In 
that regard, the experience with chlorofluorocarbons is worth noting. 
Chemical manufacturers initially fought restrictions on CFC production, 
but once they changed their position and aggressively pursued 
alternatives they made more profits than ever. Similarly, if 
substantially improved efficiencies are developed (for air 
conditioners, appliances, etc.), such that there is a significant gap 
between operating costs of installed infrastructure and available 
technologies, that could facilitate increased turnover. Perhaps 
government or utility actions to encourage turnover also might be 
considered. Corporations will eventually reap large profits from clean 
air technologies, energy efficiency, and alternative energies, so it is 
important for our industry to establish a leadership position.
    In the long-term, many energy analysts believe it is unlikely that 
energy efficiency and alternative energy sources can long sustain a 
global downtrend in CO2 emissions. Lovins (15) argues 
otherwise, pointing out the cost competitiveness of efficient energy 
end-use, gas-fired cogeneration and trigeneration at diverse scales, 
wind power and other renewable sources. Certainly it makes sense to 
give priority to extracting the full potential from efficiency and 
renewable energy sources. Holdren (16) concludes that meeting the 
energy challenge requires that we maximize the capabilities and 
minimize the liabilities in the full array of energy options.
    Many (my impression is, most) energy analysts believe that the 
requirement of a flat-to-downward trend of CO2 emissions 
probably would require increasing penetration of a major energy source 
that produces little or no CO2. Our task is only to argue 
that such possibilities exist. It will be up to the public, through 
their representatives, to weigh their benefits and liabilities. We 
mention three possibilities.
    . Nuclear power: if its liabilities, including high cost and public 
concern about safety, waste disposal and nuclear weapons proliferation, 
can be overcome, it could provide a major no-CO2 energy 
source. Advocates argue that a promising new generation of reactors is 
on the verge of overcoming these obstacles (17). There does not seem to 
be agreement on its potential cost competitiveness.
    2. Clean coal: improved energy efficiency and better scrubbing of 
particulate emissions present an argument for replacing old coal-fired 
power plants with modern designs. However, CO2 emissions are 
still high, so an increasing long-term role for coal depends on 
development of the ``zero emissions'' plant, which involves CO2 
capture and sequestration (18).
    3. Others: Oppenheimer and Boyle (19) suggest that solar power, 
which contributes very little of our power at present, could become a 
significant contributor if it were used to generate hydrogen. The 
hydrogen can be used to generate electricity in a fuel cell. Of course 
the other energy sources can also be used to generate hydrogen.
    In Holdren's (16) words: there are no silver bullets (in the array 
of energy options) nor are there any that we can be confident that we 
can do without. This suggests the need for balanced, increased public 
and private investment in research and development, including 
investments in generic technologies at the interface between energy 
supply and end use (20). The conclusion relevant to the alternative 
scenario is that, for the long-term, there are a number of 
possibilities for energy sources that produce no CO2.
                             7. benchmarks
    The alternative scenario sets a target (1 W/m2 added 
climate forcing in 50 years) that is much more ambitious than IPCC 
business-as-usual scenarios. Achievement of this scenario requires 
halting the growth of non-CO2 climate forcings and slightly 
declining CO2 emissions. Climate change is a long-term issue 
and strategies surely must be adjusted as evidence accumulates and our 
understanding improves. For that purpose it will be important to have 
quantitative measures of the climate forcings.
    Non-CO2 forcings. The reason commonly given for not 
including O3 and soot aerosols in the discussions about 
possible actions to slow climate change is the difficulty in 
quantifying their amounts and sources. That is a weak argument. These 
atmospheric constituents need to be measured in all countries for the 
sake of human health. The principal benchmark for these constituents 
would be their actual amounts. At the same time, we must develop 
improved understanding of all the sources of these gases and aerosols, 
which will help in devising the most cost-effective schemes for 
reducing the climate forcings and the health impacts.
    Methane, with an atmospheric lifetime of several years, presents a 
case that is intermediate between short-lived air pollutants and 
CO2. Measurements of atmospheric amount provide a means of 
gauging overall progress toward halting its growth, but individual 
sources must be identified better to allow optimum strategies. Improved 
source identification is practical. In some cases quantification of 
sources can be improved by regional atmospheric measurements in 
conjunction with global tracer transport modeling.
    Carbon Dioxide. Is it realistic to keep the CO2 growth 
rate from exceeding that of today? The single most important benchmark 
will be the annual change of CO2 emissions. The trend of 
CO2 emissions by the United States is particularly important 
for the reasons discussed above. Figure 11 shows the United States 
record in the 1990s. The requirement to achieve the ``alternative 
scenario'' for climate forcings is that these annual changes average 
zero or slightly negative. It is apparent that, despite much rhetoric 
about global warming in the 1990s, CO2 emissions grew at a 
rate that, if continued, would be inconsistent with the alternative 
    We suggest in the discussion above that it is realistic to aim for 
a lower emission rate that is consistent with the alternative scenario. 
This particular benchmark should receive much closer scrutiny than it 
has heretofore. The climate simulations and rationale presented above 
suggest that, if air pollution is controlled, the trend of this 
CO2 benchmark, more than any other single quantity, can help 
make the difference between large climate change and moderate climate 
                            8. communication
    Our paper on the alternative scenario (1) was reported with a 
variety of interpretations in the media. As I discuss in an open letter 
(21), this may be unavoidable, as the media often have editorial 
positions and put their own spin on news stories. Overall, the media 
correctly conveyed the thrust of our perspective on climate change. 
Furthermore, I suggest in my open letter that the Washington Post 
editorial on our paper (23) represented an astute assessment of the 
    A basic problem is that we scientists have not informed the public 
well about the nature of research. There is no fixed ``truth'' 
delivered by some body of ``experts''. Doubt and uncertainty are the 
essential ingredient in science. They drive investigation and 
hypotheses, leading to predictions. Observations are the judge.
    Of course, some things are known with higher confidence than 
others. Yet fundamental issues as well as details are continually 
questioned. The possibility of finding a new interpretation of data, 
which provides better insight into how something in nature works, is 
what makes science exciting. A new interpretation must satisfy all the 
data that the old theory fit, as well as make predictions that can be 
    For example, the fact that the Earth has warmed in the past century 
is well established, and there is a high degree of confidence that 
humans have been a major contributor to this warming. However, there 
are substantial uncertainties about the contributions of different 
forcings and how these will change in the future.
    In my open letter (21) I note the potential educational value of 
keeping an annual public scorecard of measured changes of (1) fossil 
fuel CO2 emissions, (2) atmospheric CO2 amount, 
(3) human-made climate forcing, and (4) global temperature. These are 
well-defined quantities with hypothesized relationships. It is possible 
to make the science understandable, and it may aid the discussions that 
will need to occur as years and decades pass. It may help us scientists 
                     9. summary: a brighter future
    The ``business-as-usual'' scenarios for future climate change 
provide a useful warning of possible global climate change, if human-
made climate forcings increase more and more rapidly. I assert not only 
that a climatically brighter path is feasible, but that it is 
achievable via actions that make good sense for other reasons (22, 24). 
The alternative scenario that we have presented does not include a 
detailed strategic plan for dealing with global warming. However, it 
does represent the outline of a strategy, and we have argued that its 
elements are feasible.
    It is impractical to stop CO2 from increasing in the 
near term, as fossil fuels are the engine of the global economy. 
However, the decline of the growth rate of CO2 emissions 
from 4 to 1%/year suggests that further reduction to constant emissions 
is feasible, especially since countries such as the United States have 
made only modest efforts at conservation. The potential economic and 
strategic gains from reduced energy imports themselves warrant the 
required efforts in energy conservation and development of alternative 
energy sources. It is worth noting that global CO2 emissions 
declined in 1998 and again in 1999, and I anticipate that the 2000 data 
will show a further decline. Although this trend may not be durable, it 
is consistent with the alternative scenario.
    The other requirement in our alternative scenario is to stop the 
growth of non-CO2 forcings, which means, primarily, air 
pollution and methane. The required actions make practical sense, but 
they will not happen automatically and defining the optimum approach 
requires research.
    A strategic advantage of halting the growth of non-CO2 
forcings is that it will make it practical to stop the growth of 
climate forcings entirely, in the event that climate change approaches 
unacceptable levels. The rationale for that claim is that an ever-
growing fraction of energy use is in the form of clean electrical 
energy distributed by electrical grids. If improved energy efficiency 
and non-fossil energy sources prove inadequate to slow climate change, 
we may choose to capture CO2 at power plants for 
    Global warming is a long-term problem. Strategies will need to be 
adjusted as we go along. However, it is important to start now with 
common-sense economically sound steps that slow emissions of greenhouse 
gases, including CO2, and air pollution. Early emphasis on 
air pollution has multiple immediate benefits, including the potential 
to unite interests of developed and developing countries. Barriers to 
energy efficiency need to be removed. Research and development of 
alternative energies should be supported, including a hard look at next 
generation nuclear power. Ultimately strategic decisions rest with the 
public and their representatives, but for that reason we need to make 
the science and alternative scenarios clearer.
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warming in the twenty-first century: an alternative scenario, Proc. 
Natl. Acad. Sci., 97, 9875-9880, 2000.
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J.T. Houghton, L.G. Meira Filho, B.A. Callandar, N Harris, A. 
Kattenberg and K. Maskell (eds.), Cambridge Univ. Press, Cambridge, 
England, 572 pp., 1996; Intergovernmental Panel on Climate Change, 
Climate Change 2000, editors . . . 2001.
    3. Hansen, J., R. Ruedy, A. Lacis, M. Sato, L. Nazarenko, N. 
Tausnev, I. Tegen and D. Koch, in General Circulation Model 
Development, ed. D. Randall, Academic Press, New York, pp. 127-164, 
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from paleoclimate reconstructions, Nature, 360, 573-576, 1992.
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Ruedy and J. Lerner, Climate sensitivity: analysis of feedback 
mechanisms, Geophys. Mono., 29, 130-163, 1984.
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be submitted to J. Geophys. Res., 2001.
    7. Levitus, S., J.I. Antonov, T.P. Boyer and C. Stephens, Warming 
of the world ocean, Science, 287, 2225-2229, 2000.
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Filliger, M. Herry, F. Horak, V. Puybonnieux-Texier, P. Quenel, J. 
Schneider, R. Seethaler, J.C. Vergnaud and H. Sommer, Public health 
impact of outdoor and traffic-related air pollution: a European 
assessment, The Lancet, 356, 795-801, 2000.
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pollution, Proc. Natl. Acad. Sci., 97, 13286-13293, 2000.
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B. Yiyun, Black carbon emissions in China, Atmos. Envir., in press, 
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emissions on surface ozone in the United States, Geophys. Res. Lett., 
26, 2175-2178, 1999.
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Lower tropospheric ozone trend observed in 1989-1998 at Okinawa, Japan, 
Geophys. Res. Lett., 25, 1637-1640, 1998.
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Segregation and interpretation of ozone and carbon monoxide 
measurements by air mass origin at the TOR station Mace Head, Ireland 
from 1987 to1995, J. Atmos. Chem., 28, 45-59, 1997.
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workshop of United States Association for Energy Economics, Washington, 
DC, October 16, 2000.
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Making Money, Rocky Mountain Institute, Snowmass, CO, http://
www.rmi.org/images/other/C-/ClimateMSMM.pdf; Hawken, P.G., A.B. Lovins 
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Perspectives, Cambridge Univ. Press, Cambridge, U.K., 1998.
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International Herald Tribune, Nov. 16, 2000.






    The Chairman. Thank you, Dr. Hansen. I want to thank all 
the witnesses for being here. Dr. Lindzen, you said we need to 
support science without promoting alarmism. How do you do that, 
and if you would speak close to the mike.
    Dr. Lindzen. A good question. It seems to me that to some 
extent that will require more trust of the scientific 
community. Essentially, in the post war period you typically 
had from the Armed Forces 5-year grants covering significant 
numbers of scientists, minimal paperwork, and so on.
    This was a very productive period for science. As you ask 
for more direct evidence of relevance, the easiest form of 
relevance becomes alarm, and you encourage a kind of bad trend. 
I do not have an easy answer to it, but I think it is something 
that should be thought out. You do not want bias built into 
your scientific support system.
    The Chairman. Thank you. It is my understanding that all 
five members of the panel have been involved in the IPCC 
report. Dr. Lindzen said that hundreds of scientists were never 
asked, that the report was changed in Shanghai, and that 
significant pressure was exerted. I would like to hear the 
other four witnesses' response to those rather serious 
    Dr. Ramaswamy, we will begin with you, sir.
    Dr. Ramaswamy. I think--and this is going to be a long-
winded answer, but the transfer of what is in the detailed 
technical chapter report, the transfer of that information to 
the summary for policymakers admittedly involves lots of 
careful choices of words and sentences and phrases, because it 
has to be a short summary, and so doubtless, you know, some of 
the information that is in the chapters will not appear in the 
    But I must say I was there in Shanghai. I was there in the 
plenary, and I believe there were lead authors from--I have not 
checked carefully, but I think the lead authors from all the 
chapters were present at the meeting in Shanghai. The way the 
deliberations went concerning the summary for policymakers: 
First of all, the draft was drawn up by scientists; any changes 
that were to be introduced in Shanghai--if changes were to be 
introduced, it was only in response to some comments.
    If some reviewer had comments, or someone on the floor had 
some comments, then there were considerations of how the words 
had been crafted, how the sentence had been crafted, and after 
that the scientists had to agree, basically, on any language 
that went in.
    If the scientists objected, that language never made its 
appearance, and so I believe that scientists did contribute 
significantly to the sense expressed in the summary for 
policymakers. Admittedly not all the scientists were involved 
in the drafting process of the chapters there, but by and large 
there was a representation from, I believe, all the chapters 
there, so this was pretty important, because these scientists--
    The Chairman. Was there pressure exerted to change the 
    Dr. Ramaswamy. No, there was no pressure exerted as far as 
I know. I was there on the floor on all the days, and there was 
no pressure exerted. In fact, there were moments when language 
that somebody would insist on was totally vetoed by the 
scientists, and that was the final word. Because the scientists 
did not like it that wording did not go in. Having said that, I 
would think it is true to say that not everything that is in 
the chapters did come through in the summary for policymakers, 
but these were by and large what I would call details with 
respect to certainties or uncertainties, not the major points.
    So for example, Dr. Lindzen mentioned the uncertainty we 
have about water vapor and clouds and climate feedbacks, and 
that is a very prominent uncertainty, and that was recognized 
in the summary for policymakers.
    So as I said at the outset, there is a problem in trying to 
use the English language to condense 1,000 pages down to 15 or 
20 pages, but I do not believe that the principal findings were 
in any way muted in the transfer from the chapters to the 
    The Chairman. Dr. Sathaye.
    Dr. Sathaye. Yes, thank you, Mr. Chairman. I think it might 
be worth explaining very briefly the process we go through in 
order to arrive at the Summary for Policymakers. Each of the 
chapters has an Executive Summary that is prepared with full 
participation of all the authors who have worked on that 
chapter. That Executive Summary is then used to produce two 
documents. One is the Technical Summary and the other is the 
Summary for Policymakers, and they have different audiences.
    You do not necessarily want all of the technical material 
we put in the Technical Summary to appear in the Summary for 
Policymakers, which is intended for a completely different 
audience. We often have a lot more material in the Technical 
Summary which need not appear in the Summary for Policymakers, 
and this certainly was the case with the Working Group III 
    The Chairman. I understand that, doctor, but my question 
was, were hundreds of scientists never asked and was it changed 
in Shanghai? Was there pressure brought to bear on those who 
were drafting the report?
    Dr. Sathaye. I worked on the Working Group III Report, 
which did not meet in Shanghai, but the process was very 
similar, and at no point in time was there pressure brought on 
any of the authors to change any of their findings. Indeed, as 
Ram just mentioned, in Akra, delegates consulted us. They made 
sure that the language we were using was accurate, and we made 
changes to that language to make sure that it fully reflected 
the underlying report.
    The Chairman. Thank you.
    Dr. McCarthy.
    Dr. McCarthy. Thank you. I would just echo the comments of 
my two colleagues. I was in Shanghai, the working group that I 
chair had its final plenary meeting in Geneva. The process that 
was just described was the same for Working Group 2. The actual 
drafting of the Summary for Policymakers (SPM) was done by 
about 60 authors, but every author had an opportunity to see 
each draft as it was initially prepared before a meeting of all 
authors last August. Everyone had a chance to look at the 
responses to the government reviews and every author had an 
opportunity to see the revisions to the SPM.
    We took the revised form of the SPM to our plenary meeting 
in Geneva, and I would describe the process as one of trying to 
take, as mentioned by my colleagues, a document that is full of 
the representation of scientific detail first to a summary 
document, the Technical Summary, and then to as clear a 
statement as scientists can produce--that is, strip all the 
jargon, to make the language of the Summary for Policymakers 
intelligible to anyone who would care to know how this 
information might be used in a policy context. So I see the 
plenary, really, as the final clarifying process.
    Now, similarly, we had about 40 of our authors--that is, 
our lead authors of every chapter present at that final 
meeting. If at any time a question was made, or raised from the 
floor of the plenary, by any of the 150 delegates from 100 
nations, about a particular statement, saying for example, that 
they thought it should be worded differently, if the suggested 
change was simply for the purpose of clarifying the language, 
and the authors present concurred that the proposed change did 
not alter the scientific meaning, then the suggestion would 
    At times a suggestion by a delegate from one country would 
be opposed by another saying no, I do not think that makes it 
clearer at all, so a lot of our discussion went back and forth 
involving maybe a third delegate, who came up with yet another 
suggestion, and if we got stuck in a situation like this, then 
the chair would ask a small group to retire during lunch and 
have a smaller meeting, open to everyone, but asking someone to 
chair it, and then to come back to the full plenary with a 
proposed solution.
    So literally, the process is one in which we never vote. We 
would proceed through the document until at the end of the day 
all delegations say, I am satisfied I fully understand this 
document, it is gaveled, and it is then fully accepted by the 
    The Chairman. Dr. Hansen.
    Dr. Hansen. That is a very difficult question. The IPCC is 
carrying out a very necessary process, and the technical work 
is superb. It involves a large number of outstanding 
scientists, and I am in no way critical of those scientists, 
but I must say I have a significant degree of discomfort with 
the extrapolation of the science into policy directions, the 
close interconnection of the IPCC and the Kyoto discussions.
    I also think that a large committee is seldom the best 
approach for determining actions. I do not feel that I have a 
prescription or that I know the best procedure to do this, but 
I felt much more comfortable with the assessment 20 years ago 
when it was done by the National Academy of Sciences, a stellar 
committee chaired by Joel Charney of MIT, who stayed away from 
policy but gave an outstanding scientific assessment.
    So I do not have a very good answer to that, but I feel 
some discomfort about it.
    The Chairman. Thank you. I would like to ask one more 
question of the panel, and this is something which I am sure 
will not be an easy one or a comfortable one for you to respond 
to. I want you to for a moment put yourself in the shoes of the 
legislator. We have now received numerous reports. We now have 
cumulative evidence that there is climate change. We have had 
some disagreements on what should be done, if anything, and so 
I would like to begin with you, Dr. Lindzen, and ask you, as a 
legislator, what policies or what legislation would you propose 
to attempt to address these issues, if any? Perhaps none.
    Dr. Lindzen. I think it may be premature to take actions 
explicitly designed for this. I think there is general 
agreement with taking care of things like efficiency, reduced 
toxic pollution and so on, which have independent benefits. 
This is, I think, what is referred to as no regrets. I think 
with respect to science, treat it as an open question and ask 
that the physics be improved.
    At present, I mean, it is a point I make in my testimony, 
it is widely understood that doubling CO2 alone 
gives you about a degree centigrade warming. The rest of the 
higher predictions come from the so-called feedback processes. 
These are very weakly understood. They are crucial, and they 
are in many ways not the focus of our research. I think they 
deserve more.
    The Chairman. Dr. Ram.
    Dr. Ramaswamy. Well, that is a difficult question, and I 
guess I am going to stick to my parochial barriers here and 
essentially emphasize--in fact, I would reiterate Dr. Lindzen's 
point, that good, sound science should be the underpinning for 
any policy decision, and the science should be checked and 
rechecked constantly, because science is an evolving thing. It 
is advancing all the time.
    So there should be a careful scrutiny of the science, and I 
would emphasize that besides the measurements we also need 
process studies and modeling to go along with it. The three 
actually go simultaneously together.
    You cannot have a decision based on just observations. You 
cannot have a decision just based on models alone, and I think 
it is this collective picture, looking at all the observations 
and indicators, coupled with model simulations, and coupled 
with the understanding of the physical processes, that 
essentially unites and completes the picture. If you had just 
one of them, that is not the whole picture, so I would 
emphasize that that be the underpinning for the policy 
    I know this is not the direct answer to your question, but 
it is kind of in a roundabout way.
    The Chairman. Dr. Sathaye.
    Dr. Sathaye. Well, never having been a legislator, this is 
a tough question to answer, but since the work that I do 
focuses a lot on technologies and costs and policies, let me 
just suggest a few areas which are, as others have mentioned 
before me, worth pursuing regardless. It is very clear that 
energy efficiency improvements and long-term R&D would form the 
backbone of any decisions you might make, if not today, perhaps 
some years from now, and in fact the question about how soon do 
you wish to act, or one should act, depends a lot upon what 
levels you wish to stabilize climate at, for which we do not 
have a consensus.
    If you want to stabilize at 450, you need to start reducing 
emissions by 2015, and so forth, and so without having that 
particular consensus, one pursues other things that are good 
for the economy, and I do not think we are doing nearly enough 
in that area.
    The Chairman. Do you not think that there is largely an 
emerging consensus on this issue?
    Dr. Sathaye. Yes, there is an emerging consensus on this 
issue. The sooner there is consensus, or the lower your 
emissions are, the sooner you will act; the more room you will 
have to play later on, so to speak.
    The Chairman. Dr. McCarthy.
    Dr. McCarthy. Thank you, Mr. Chairman.
    The Chairman. By the way, I am aware this is a very 
difficult question and I ask it of myself every day.
    Dr. McCarthy. Some of us took the easy route and retired to 
an academic life, rather than the difficult route, that of a 
    I think that there are several things we can and should do 
right away. I think some of these suggestions have been made 
already by my colleagues taking the lead from Dr. Hansen on no-
regrets policies.
    I think the notion that there may be some low-hanging fruit 
with some of the other greenhouse gases should be explored 
vigorously, but I do believe that this is an issue that we 
should look at very differently today than just 5 or even 10 
years ago, because as the Summary for Policymakers in this 
third assessment says for the impacts of climate change, we 
know now about impacts, things we did not know 5 years ago 
because of the recent rate of some of these changes.
    With respect to the comments made by Senator Stevens, I 
would comment that one of my hobbies is the old polar 
exploration literature. It would be fair to say if someone had 
told me 5 years ago that we would be seeing within the next 10, 
20, 30 years the opportunity for ships to travel through the 
Northwest Passage, I would have said that is inconceivable. 
Historically, this name has been a misnomer. It should have 
been called the Northwest impediment.
    The fact that we have seen these dramatic changes, and they 
are entirely consistent, as I have said, where we have examined 
thousands of papers, and for 80 percent of them, these changes 
are consistent with the local changes in temperature. This 
tells us that responses to climate change are occurring more 
quickly than we had thought possible.
    Now, I know Dr. Lindzen said we do not understand the 
physics, and I certainly do not understand the physics, but 
Working Group 1 tells us that intense heat spells, intense 
precipitation events, increased wind velocities associated with 
tropical storms, and increased El Nino like conditions are all 
projections for future climate with 90 percent confidence.
    Now, I am not an expert on that. I cannot possibly explain 
the mechanism, but that is part of the summary statement from 
the Working Group 1 report. If we are wrong and find that these 
factors are not so serious, then we could feel comfort in 
having sat aside and waiting for clearer signals. But if we are 
wrong in the other direction and if they are even more serious 
than we think they are, then these consequences could be even 
    I think an appropriate way to look at this is rather like 
insurance, the insurance that we invest in for all of our 
personal property, and our lives. I think that to gamble that 
these projections will not be borne out within the near future 
is a very, very risky step, and I believe, as our report says 
very clearly, that even the most aggressive actions that have 
been proposed will not prevent some of this damage. In addition 
to looking very seriously at all mitigation options, we must 
look very seriously at enhancing opportunities for adaptation, 
not only in those regions that are going to be most hard-hit, 
the tropic and subtropical regions, but also in northern 
industrialized countries as well.
    The Chairman. Dr. Hansen.
    Dr. Hansen. I agree that first of all we should take the 
steps that have other benefits and, in fact, I think these may 
take us most of the way and perhaps all of the way to what we 
need. I refer particularly to pollution, the examples I gave 
with regard to air pollution. Also, we need to support energy 
efficiency and alternative energies, because of the strategic 
value they will have with regard to our energy independence. 
Second, we should make the measurements that are necessary so 
we can understand what is really happening to the climate 
system. Third, we need to adapt the approach as we go along. 
This is a long-term issue.
    The Chairman. Thank you. There is a vote on. Senator 
Brownback is over voting, and he will be back for his 
questions. I am going to go vote and will be back. Senator 
Kerry, do you want to start?
    Senator Kerry. Is Senator Brownback going to come back?
    The Chairman. Yes, or I can recess.
    Senator Kerry. Why don't we recess, and I will come back, 
    The Chairman. We will take a brief recess. Senator Kerry 
and Senator Brownback will come back. Senator Kerry will have 
questions as soon as he returns. He is very quick.
    Senator Brownback. If we could bring the committee back to 
order, sorry about the brief intermission. We have a vote on on 
the floor, and we will continue with the hearing, if you do not 
mind. Let me make a couple of comments, if I could to you, and 
ask that my full opening statement be put into the record, at 
the appropriate place in the record. I appreciate the testimony 
you gentlemen have given and the information you have put 
    I have put forward two bills that I think are in lines with 
the keeping of some of the items that you have suggested, and I 
just want to draw your attention to it and then ask your 
comments about it. Number 1 is a domestic carbon bill that 
would make small payments to farmers, primarily, on the basis 
of practices that they would use that would increase CO2 
or carbon sequestration in the soil.
    These I think would be generally practices along the lines 
of a no-regrets policy, as one of you had identified that would 
approve soil conservation, soil quality by putting back into 
the soil carbon, which has been released when we tilled up the 
prairies, when we have gone to plowing previously, and this 
would be coming back to more of a no-till, more fixing the 
carbon into the soil, so that you would reward farmers for a 
process of farming, not necessarily production of farming, but 
a process by which they would farm that would fix more carbon 
in the soil, and these would be the practices that would be 
agreed to by appropriate scientific and USDA models and panels.
    The second item is a bill that provides for $200 million in 
tax credits to individuals or companies in the United States 
that invest in reforestation, either domestic or abroad. This 
is modeled after what I think is a start of a pretty 
successful-looking project by the Nature Conservancy in South 
America. They have got projects going in Belize, Bolivia, and 
Brazil. I am hoping they will get outside of just B countries 
and into all nations.
    I toured one in January in Brazil, where they had bought 
back about 150,000 acres in the Atlantic forest region in 
Brazil that had been broken out, farmed, and then had returned 
to pasture for water buffalo, and they were buying it back to 
turn it back to Atlantic forest region. They were measuring the 
amount of carbon that was being fixed over a 40-year cycle, 
working with the local nongovernmental organization in Brazil 
that actually owned the land. The money was put up by groups in 
the United States, several large companies that put the 
resources up to actually purchase the property.
    What I would do is provide tax credits, about $200 million 
initially, to try to incentivize and encourage more of these 
reforestation carbon-fixing, or carbon sinks, as I have 
addressed it in both types of models.
    I would be curious what you think about these sort of 
incentivized--and I would like to think along the lines in the 
future, sa we reduce CO2, that we will do so on a 
market basis, where we do it on a least-cost type of models, 
that these would be kind of early types of models where you get 
the low-lying fruit of pretty quick CO2 sinks, 
sequestrations that would take place with these.
    Any thoughts about models like this from any of the 
panelists, or if you yourself have thought along any of these 
policy models?
    Dr. Sathaye.
    Dr. Sathaye. Yes, I think--let me speak with a personal--
from a scientific perspective on this topic. We had an IPCC 
report on forestry that looked at many of the questions related 
to project-specific soil conservation. I think at the outset I 
should say yes, it is a great idea, and that it is worth 
    Certainly land exchange and forestry options offer an 
important sink for carbon, and the no-till agriculture you 
mentioned would be one of the types of activities that could be 
done in the United States and in other countries as well. 
Indeed, in many cases these types of projects have the 
potential to bring in early monetary returns for the investor.
    As the trees grow, and if you are in a position to sell 
that carbon, you can get revenues fairly early on, and it is a 
good thing for these types of projects.
    There are two issues, though, that one needs to be careful 
about in pursuing these projects. One has to do with a question 
of permanence, and this, too, has been alluded to by many. One 
of the challenges is, how long would these carbon sinks last? 
We lose carbon at some point in time. We have four different 
ways of dealing with that, and to the extent that these 
projects incorporate one of those four ways, then you can, 
indeed, pursue these kinds of projects.
    The four ways are, they all amount really to accounting for 
any carbon that you lose and this may be done through an 
insurance scheme, it may be done by simply starting another 
project in place of whatever carbon you might lose, so there 
are different approaches to it. Well, we know how to deal with 
    The second issue has to deal with what is being labeled as 
leakage, and this is where, if you practice, let us say, 
reducing deforestation in a given area, and if they go to some 
other place and start deforesting, then you lose any carbon 
benefits you might get in the area that you stopped the 
deforestation from. How do you avoid that?
    Here, too, we have ways to address leakage by pursuing 
multicomponent projects. You have wide deforestation in one 
area, then you can provide incentives in another area, so we 
have ways of dealing with this, and to the extent we take care 
of those, these are as good an approach for removing carbon out 
of the atmosphere as we might get out of energy efficiency, or 
alternative energy sources.
    Senator Brownback. Others? Dr. Hansen, did you have any 
thoughts on this, perchance?
    Dr. Hansen. Well, on the face of it they are both 
commendable activities. It does depend upon the kind of detail 
we were just hearing about, and I think it is important to 
quantify the degree to which these other benefits in addition 
to reducing CO2 in the air, are in fact realized. We 
need to have a good cost-benefit analysis. Even though I am 
from Iowa, I do not claim to have expertise on exactly what the 
impact will be, of either the no-till or the reforestation, 
because of these possible indirect effects. So I cannot really 
say much now that can help you.
    Senator Brownback. Dr. McCarthy.
    Dr. McCarthy. Just briefly, Senator Brownback, I, too, 
believe that this is an example of the sort of incentive the 
government can provide that could in some instances make a 
substantial difference.
    It has, however, only been within the last, maybe handful 
of years that scientists have begun to look rather rigorously 
at some of these balances and the effects of perturbations, and 
the cessation of a perturbation on an ecosystem, but it is very 
clear that that is an area that has potential to be an 
important contributor, and I would just add that it is also 
important to keep in mind--I am not directing this to you 
personally, but to all of us, that there is no single best way 
to address the sort of larger question we are asking, and I 
think this is an example of mitigation options that people 
would not have thought of a decade ago as having any potential.
    Within the last 5 years we have begun to look at it 
carefully. It appears now that with the sort of qualifications 
my colleagues have mentioned, that it does have potential and 
should be looked at very carefully.
    Senator Brownback. Dr. Sathaye, is this the sort of thing 
that could possibly be used in emissions trading? You talk 
somewhat about emissions trading, and least-cost approaches for 
CO2 reductions. Would you, particularly on 
reforestation efforts, support the use of that on an emissions 
trading type of basis?
    Dr. Sathaye. First of all, yes, you could include 
reforestation options in the emissions trading scheme but the 
way it is being discussed, and the way it has been talked 
about, is to have reforestation projects in other countries, 
and then trade--let us say you do a reforestation project in 
Europe some place, or Asia, the carbon that you sequester 
through that process could be traded with carbon needs here.
    That is certainly a legitimate way of doing it, and it 
could be identical, to what you would get from any other type 
of energy source.
    A couple of caveats that I mentioned earlier about 
permanence, and also this question of how carefully can you 
measure carbon. We have carbon in four different pools. In the 
forestry projects, we have it in vegetation, in soils, in 
products, and in above and below-ground vegetation, litter and 
so forth. These are the pools.
    Senator Brownback. Those are being measured in the Bolivia 
and the Brazilian project pretty aggressively, and I do not 
know if the scientific community has agreed to the measurement 
method that they want to go with, but they are measured on a 
first year, third year, and then every fifth year, then on 
through 40 years to try to address a permanence issue, and 
leakage issue is also addressed in the bill, requiring to work 
with local people to encourage them to be able to stay, but 
shift their economic income sources from what they have been in 
the past.
    Dr. Sathaye. There is no difficulty in measurement methods. 
We know how to measure carbon. If somebody brought it to my lab 
and said, ``measure this carbon, from this soil,'' or ``we can 
do it.'' The challenge is really whether we have a system set 
up in order to do these kinds of measurements on a normal 
basis, and how much might this cost.
    Senator Brownback. The final question I want to ask, Dr. 
Hansen, you mentioned something about a clean coal type of 
technology, and I think this is also in another testimony, 
where you actually capture the CO2 at the end of the 
pipe, I guess, and store it, is that correct?
    Dr. Hansen. Yes. The danger with coal is that it is by far 
the largest potential source of atmospheric CO2, 
with about 10 times as much as oil and gas. So you have to be 
very careful about introducing greater coal use. We can reduce 
the black carbon probably fairly easily, that is the soot, with 
more efficient burning and filters on the smokestacks. In fact, 
that would do some good, but if we then start burning so much 
coal that we are producing more and more CO2, that 
would be counterproductive. So it is, I think, important to 
explore this possibility of zero emissions coal, but again I am 
not an expert on that.
    I have heard that Germany, Japan, the United States, all 
are working toward that type of technology, and there have been 
some impressive presentations about that. It really needs to be 
looked at, because if that were possible----
    Senator Brownback. That solves a lot of our problems.
    Dr. Hansen. It does solve a lot of our problems, but it is 
bound to increase the cost of coal use, so is China going to 
take that extra step to capture CO2? They have a lot 
of coal.
    So it is an open issue. I think it really needs to be 
looked at pretty hard.
    Senator Brownback. I just noted that in your testimony. 
That is very interesting. I was not familiar with how you would 
do that, but apparently that is being researched and looked at 
now. That is not known as a real solution.
    I am sorry, I am going to have to slip on here, and I do 
not know that--I understand Senator Kerry is supposed to be 
coming back. Let me just say, if I could, in conclusion--and 
maybe he will come back in the interim here--is that a number 
of us are going to be working on ways that we can move forward 
on some no-regrets policies, items that have multiplicity of 
benefits you are talking about.
    In addition to reducing CO2, or in recapturing 
CO2, there would be positive effects, and I think 
that in the state of play where we are as a nation and as 
policymakers at this point in time, that that is probably the 
best route to go, and I hear several of you suggesting that 
indeed is the route that you would suggest that we proceed. I 
hope you would engage us on a very open basis to suggest and to 
help us work through those so that we can start to address this 
issue that has been building for a long period of time that 
needs to be addressed.
    There is still some cautiousness on some parts, but I think 
we can do things that at the end of the day we would say, there 
is no real reason why we should not do these steps.
    I want to thank you all very much. We are going to stay in 
recess until Senator Kerry returns. If the panel does not mind 
for a few minutes we will be in recess.
    Senator Brownback. I call the hearing back to order. Let me 
apologize to our panelists. I have been told that Senator Kerry 
will not be returning.
    I do want to thank the panels and those that have been 
watching, and in attendance. I note there will be a 
subcommittee hearing on solutions, and these no-threat types of 
proposals, and we will be holding that within the next couple 
of weeks as we start to work through some plausible legislative 
solutions we can proceed with. The record will remain open for 
the requisite number of days for additional testimony to be 
submitted, or questions to be submitted. I thank the panelists 
again for being in attendance and sharing their views with us. 
The hearing is adjourned.
    [Whereupon, at 11:30 a.m., the committee adjourned.]
                            A P P E N D I X

        Prepared Statement of Hon. John F. Kerry, U.S. Senator 
                          from Massachussetts
    I want to thank Chairman McCain for holding today's hearing. As I 
have expressed to the Committee before, I believe that addressing the 
threat of climate change is one of the great challenges before the 
nation and the world. It certainly deserves the attention of this 
    Our topic today is the Intergovernmental Panel on Climate Change's 
Third Assessment Report. I want to take just a moment to discuss some 
of the history of the IPCC.
    The Panel was created in 1988 to serve as an independent advisor to 
world leaders in assessing the scientific, technical and socio-economic 
information relevant for the understanding of the risk of human-induced 
climate change. Here in Washington that translated into studying the 
``scientific uncertainties'' of global warming.
    In an April 1989 appropriations letter to Congress, President Bush 
wrote, ``Significant uncertainties remain about the magnitude, timing, 
and regional impacts of global climate change. During Fiscal Year 1988, 
the United States has made major contributions to international plans 
to reduce those uncertainties.'' Among the contributions the President 
noted was the Intergovernmental Panel on Climate Change, which, he 
said, ``launched its multilateral effort in November 1988 with U.S. 
participation and support.''
    In a speech to the IPCC in February 1990, President Bush concluded 
that ``human activities are changing the atmosphere in unexpected and 
unprecedented ways.'' And that, ``the United States will continue its 
efforts to improve our understanding of climate change, to seek hard 
data, accurate models and new ways to improve the science and determine 
how best to meet these tremendous challenges.''
    I think the fundamental question before this Committee today is, 
``What have we learned in 10 years of study and three assessment 
reports from the IPCC?'' My sense is the Panel has fulfilled its 
mission as an independent, scientific adviser to the nations of the 
world. It is also my sense that the Committee can place great 
confidence in the notion that human activities are contributing to 
rising atmospheric concentrations of greenhouse gases with potentially 
adverse consequences for the environment and millions of people.
    Uncertainty exists--as it does in almost all matters of public 
policy--but that uncertainty has been reduced significantly over the 
past decade. And some uncertainty does not always justify inaction. In 
1989, Secretary of State James Baker III spoke to the IPCC. He stated 
that, ``[W]e can probably not afford to wait until all the 
uncertainties have been resolved before we do act. Time will not make 
this problem go away.'' I agree with Secretary Baker.
    Unfortunately too many individuals, companies, nations and some in 
the Congress have used the fact that we can never be absolutely certain 
of how a natural system as complex as the global climate will respond 
to confuse the debate and undermine any meaningful policies.
    That is why 10 years since Secretary Baker made that statement and 
despite more conclusive science, our nation has done so little to 
resolve the threat of climate change. Our emissions--despite our pledge 
to cut them in the Framework Convention on Climate Change have only 
grown. I hope Mr. Chairman, that this hearing will help build a 
foundation for the Congress to move constructively toward lowering our 
greenhouse gas emissions and responding to the threat of climate 
    In closing, Mr. Chairman, I want to express my disappointment in 
those who now attack the IPCC because they do not like its scientific 
conclusions. They assail the process of the IPCC and the motives of 
individuals who have lead the IPCC effort. Dr. Lindzen and my 
colleagues Senators Craig and Hagel have submitted such testimony 
today. I have listened carefully to their comments--and I respectfully 
disagree. I believe the scientists involved in the IPCC have done their 
best to provide an independent and honest assessment of the state of 
knowledge of the world's climate. It is an extraordinary charge we have 
given them, and I do not question their tremendous effort.
    I thank the IPCC for its work. I thank our panelists for joining us 
today. And I thank the Chairman for holding this hearing.
     Responses to Written Questions Submitted by Hon. John McCain 
                     to Dr. Venkatachala Ramaswamy
    Question 1. The IPCC report states that climate models have evolved 
and improved significantly since the last assessment. However, the 
National Research Council reports indicates that US modeling 
capabilities trails those of Europe. Do you agree with that assessment?
    I would like to first thank the Committee for the invitation to 
appear, and to present my testimony on climate change science. I am 
very appreciative of the thoughtful questions that have been put 
forward as follow-up to the testimony. In my testimony, as requested, I 
focussed exclusively on the scientific evaluations, following the 
details spelt out in the IPCC 2001 assessment. Partly because of the 
nature of the follow-up questions, I find that I have to go beyond the 
scope of the IPCC report, and include personal views in response to 
some of the questions.
    Answer. On the first element under this question, coupled 
atmosphere-ocean climate models have evolved and improved significantly 
since the time of the previous IPCC assessment (IPCC, 1996). There is 
now improved knowledge of the physics based on theoretical and 
observational developments, including a longer observational record. 
For example, there is now an improved understanding of convection, 
radiation, boundary layer, and clouds, which constitute key climate 
feedback processes. These improvements have led to better 
representations of the physical processes in models and, therefore, 
increased credibility of the models to perform simulations of climate 
variations and change. There are now better simulations of climate, at 
least down to continental scales and over temporal scales from seasonal 
to decadal, including slight improvements in simulating El Nino. 
Confidence in model projections has also increased owing to the ability 
of climate models to maintain stable, multi-century simulations of 
climate; these are of sufficient quality for use in addressing climate 
change questions. Confidence in the ability of models to project future 
climates has been enhanced by the ability of several models to 
reproduce the warming trends in the 20th century surface temperature 
when driven by the known natural and anthropogenic forcings. Systematic 
intercomparisons of coupled climate models developed in recent years 
provides another line of evidence for the growing capabilities of such 
tools. Although there remain key uncertainties and quantitative aspects 
of key climate processes have yet to become robust, important 
scientific strides have been made in coupled atmosphere-ocean modeling 
since the last assessment.
    The second part of the question touches upon a somewhat different 
issue viz., ``US versus Europe's modeling capabilities''. There are 
several sub-texts to be considered here. The first point is that there 
is no need to look upon the situation as a ``US versus Europe'' 
competition of an unhealthy type. It is more useful to consider our 
European counterparts as worthy collaborators in our joint quest to 
advance the knowledge in climate science. The investigation of climate 
and climate change is a massive scientific problem, and requires vast 
amounts of resources of various kinds in a globe-wide context, more 
than any one country could possibly support. To address this complex 
science, it is important to pursue the investigations in a cooperative 
and collaborative sense, recognizing that scientists in Europe (and 
elsewhere) may have as much and/or unique contributions to make to the 
advancements. It is in fact the recognition of this complexity and the 
need for a collaborative spirit that has led to IPCC's successful 
evaluations of the climate science, guided strictly by scientific bases 
and peer-reviewed publications. It is, however, incumbent upon US 
scientists to bear in mind always the highest traditions of science, 
and pursue the truth in an independent and original manner without 
    Secondly, compared to Europe, and seen in purely computational 
facility and human brainware terms, it has become evident that the UK's 
Hadley Center (under the UK Meteorological Office) made a very focussed 
effort and posted substantive accomplishments, more than any other 
center in the world, during the latter half of the 1990s decade. There 
is one metric in particular that illustrates this point. The Hadley 
Center model has performed stable climate simulation integrations in 
excess of thousand years without flux adjustments--no other model in 
the world has been able to perform such integrations without flux 
adjustments/ corrections at the atmosphere-ocean interface. However, 
this model has been the only European climate model that has eclipsed 
the US achievements. It is important to note that no other model from 
any of Europe's other climate science institutions can be said to be 
more advanced than those in the US, with regards to the metric cited 
above or, for that matter, other metrics of relevance for long-term 
climate change.
    It is a matter of considerable concern (and indeed has been 
recognized to be so by the Academy report) that the computational 
ability of the US has suffered a serious setback in the past few years. 
While European institutions have not had to think of changing basic 
architectures of their computational systems and have been able to 
procure the fastest computers available, US institutions have found 
their ability hampered in the procurements of the fastest computers in 
the world. And, there have not been many competitive alternatives 
available in this regard to the US institutions. Besides decelerating 
the pace of scientific research in the US, this factor has also 
initiated uncertainties about potential future computing frameworks for 
climate modeling research.
    It is unfortunate, too, that the brainpower (i.e. talented human 
resources) needed to tackle the climate science problem has also 
suffered in recent years in the US. While European institutions and 
Hadley Center in particular have been able to ensure that funding and 
institutional infrastructure continue to be favorable enough to attract 
young students and scientists, such that they have been able to readily 
recruit bright and talented youth emerging from the colleges, US has 
lagged severely in this respect. Hadley Center has not only recruited 
top-class youth but has also motivated them into focussed climate 
modeling exercises. The problems in the US include: lack of resources 
to motivate the top minds in the country to turn to and remain engaged 
in science, declining base funding which barely if at all keeps pace 
with inflation, and declining infrastructure resources with lack of 
steady commitments to maintain top-class climate centers.
    The above elements, while very crucial, have to be juxtaposed with 
a third one that is at least equal in value to those stated above. This 
concerns the question of extraction of science from the climate model 
simulations and observations. Obviously, it is not just enough to have 
the best computer, infrastructure and human resources. A key question 
is how far has the science been actually advanced. Examination of 
computer model simulations, critically analyzing them in conjunction 
with observational data of various kinds, and making incisive and 
proper diagnostic interpretations are the hallmarks of success in 
scientific research. This element, together with the others above, 
constitutes, in my view, the definition of the term ``modeling 
capabilities''. In this regard, it is not at all clear that the US 
contributions, in terms of the peer-reviewed findings reported in 
journals or in the IPCC reports, are any less relevant in originality 
and substance than contributions from Europe, including those from the 
Hadley Center.
    The Academy document, while rightly pointing out the limitations of 
computer hardware and brainware, has chosen to critique a somewhat 
narrower focus of the overall problem. It has not emphasized enough 
that scientific accomplishments and advancement of knowledge in long-
term climate change require more than just hardware and brainware. In 
particular, it has paid less emphasis to how the US has fared in the 
third element mentioned above. While Hadley Center may have 
unquestionably led in the implementation of the most sophisticated 
physics and thus created the most stable climate model simulations to-
date, US institutions doing research in climate change have likely been 
not far behind Hadley center in the overall diagnostic analyses of 
climate change--forcings, feedbacks and responses. Compared to other 
institutions in Europe, there is no question that the leading US 
climate change research centers have at least been on par, if not 
outshining them.
    But, it is easy to become complacent. Thus, it is important that US 
take firm, proactive steps to ensure sustained advancements in computer 
power, assure itself of a continued stream of talent to engage in the 
science, spot infrastructure deficiencies and build up with steady 
commitments. In turn, it should be demanded that scientific research 
continue to provide an unbiased, well-grounded and critical appraisal 
of the understanding of climate change to policy makers.
    Question 2. How many more scenarios were involved in this recent 
assessment report as compared to five years ago? Would the scenarios 
used 5 years ago result in the new predicted increases in sea level 
rise and global-average surface temperatures?
    Answer. The IPCC 1996 climate change science assessment employed 
the IS92 suite of scenarios (6 in all), with the middle of the range 
being the oft-mentioned IS92a scenario. In the 2001 assessment, the 
calculations drew upon the IPCC Special Report on Emissions Scenarios 
(SRES), besides also comparing the results with those from the IS92a 
scenarios (see Figure 5, IPCC Summary for Policymakers). The SRES was a 
separate study from the Working Group I climate change science 
assessment. The SRES scenarios were drawn up based on a range of 
diverse assumptions concerning future demographics, population 
evolution, economic developments and technologies. While a few of these 
new scenarios are similar to the IS92 set, some of the newer scenarios 
differ markedly from the earlier ones employed by IPCC. There were 
about 40 scenarios used in IPCC 2001, with 4 main groups or families, 
and with 6 ``marker'' scenarios. As an example, the IS92a scenario 
projection for carbon dioxide concentrations in this century is roughly 
comparable to that for the A1B and A2 scenarios. The IS92 and the newer 
scenarios represent quite a diverse collection of projections. 
Nevertheless, it is emphasized that the projections should be 
considered as sensitivity illustrations that employ a wide range of 
assumptions for the purposes of obtaining insights into the plausible 
projections of future climate changes due to anthropogenic emissions.
    IPCC has discussed the projections of plausible future climates in 
terms of a range that is a consequence of the variety in the scenario 
assumptions. In arriving at the range of future climate change, IPCC 
2001 considered the IS92 scenarios as well. The projections discussed 
in the 2001 report yield a range that encompasses the results of the 
IS92 scenarios, with the overall range wider now than in IPCC 1996. The 
change in the range from IPCC 1996 is due in part to the several new 
emission scenarios considered. The examination of both the IS92 and the 
newer scenarios in the 2001 report achieves the intent of surveying the 
effects due to an array of assumptions about emissions of radiatively-
active species. Thus, the IS92a scenario (BaU) results for global-mean 
temperature and sea-level changes are indeed accounted for in the range 
cited in the 2001 report.
    An important technical difference between the older and newer 
scenarios is the assumption of cleaner technologies in SRES which leads 
to differing considerations of the relative amounts of the projected 
concentrations of greenhouse gases and aerosols. In particular, the 
aerosol concentrations are affected by an earlier invocation of cleaner 
technologies in this century. As aerosols are short-lived, their 
concentrations are affected right away. Thus, the sulfate aerosol 
forcing concentrations (which yield a cooling) are projected to fall 
faster in the newer scenarios than was the case in the IS92 (e.g., 
IS92a) scenario. Greenhouse gas concentrations (including 
CO2) rise less rapidly than in IS92a for several, but not 
all, of the newer scenarios. An additional feature in the IPCC 2001 
report was to use the scenarios in conjunction with different model 
climate sensitivities to approximately mimic the range in climate 
sensitivity that arises owing to uncertainties in the physical 
    Taking into account the ranges provided by the assumptions leading 
to the greenhouse gases and sulfur emissions, and the range in climate 
sensitivity, the following results are cited by IPCC (2001). The 
presently (and the most recently) cited range for the global-mean 
surface temperature change projected in 2100 is 1.4 to 5.8 C; this is 
to be contrasted with the range of 1 to 3.5 C in IPCC (1996). The main 
reason for the upper end being greater and a wider range has to do with 
the lower sulfur emission projections in the present report relative to 
the IS92 scenarios. Lower sulfur emission means lesser importance of 
the role of cooling effect by aerosols relative to the long-lived 
greenhouse gases. The corresponding global sea-level rise in the 2001 
report is 0.09 to 0.88 m. This is to be contrasted with 0.13 to 0.94 m 
in the earlier report. Despite a higher temperature projected at the 
upper end of the range, the sea-level projections are lower owing to 
improvements in models that now yield a smaller contribution from 
glacier and ice-sheet melts. It is reiterated that the scenarios used 
five years ago yield results that are within the range spelt out in the 
2001 report.
    Question 3. You have stated that a key aspect of climate change is 
that a greenhouse gas warming could be reversed only very slowly. Can 
you elaborate on that point and also comment on the value in 
sequestration in this process?
    Answer. The major greenhouse gas being input into the atmosphere, 
CO2, has a long residence time owing to its chemical 
inertness. Its sinks act quite slowly; in particular, mixing into the 
oceans is very slow. Thus, it is expected that it would take a long 
time (centuries) to draw down the CO2 that has been emitted. 
Other greenhouse gases, which are less strong climate forcing agents 
compared to CO2, can be just as long-lived. In a general 
sense, there are several important climate forcing gases, with 
lifetimes varying from ten to upwards of hundred years (e.g., methane, 
nitrous oxide, halocarbons, sulfur hexafluoride). With the CO2 
sinks tending to operate slowly, even if it were assumed that all 
emissions ceased at present, there would tend to be only a slow 
decrease in the atmospheric CO2 concentration.
    The long residence time factor implies that the radiative forcing 
due to the emitted CO2 will act for a long period of time. 
In addition, there is another timescale that has to be taken into 
account. This concerns the delay in the thermal response of the oceans 
owing to the long time it takes for heat to be diffused into or out of 
the deep ocean. At present, the climate is not in equilibrium with the 
present atmospheric CO2 implying that the complete impact of 
present-day CO2 is yet to be fully realized. Thus, while 
atmospheric CO2 is not in equilibrium with the present 
emissions, the climate is not in equilibrium with the present-day 
atmospheric concentrations. Thus, even if the atmospheric CO2 
concentration were to be stabilized at a particular value and at a 
particular time, the climate effects can be expected to be felt well 
after this point is reached e.g., continued sea-level rise. The longer 
this forcing element is there in the atmosphere, the further the delay 
in the recovery of the climate system. In view of the slow but long 
associated timescales, greenhouse gas warming can be reversed only very 
slowly. In this regard, the possibility of non-linear and irreversible 
climate changes owing to feedback mechanisms existing in the system 
cannot be overlooked.
    Sequestration process, meaning a mechanism to draw down the 
CO2 thus reducing its atmospheric composition, would 
presumably achieve the objective of lowering the quantum of this 
forcing agent in the atmosphere. This is a conceptually attractive idea 
and one that is engaging vigorous research attention. Thus far, 
however, the research has yet to be translated in robust quantitative 
and practical terms, including cost-effectiveness. Early results are 
somewhat tentative on the overall effectiveness and scaling with 
respect to natural sinks, especially on multi-decadal to multi-century 
time scales. Note that even if it were possible to sequester all future 
CO2 emissions, climate would still continue to warm and sea-
levels would continue to rise, as noted above, because of the slow 
climate response to the existing atmospheric concentrations. 
Nonetheless, there are some interesting ideas concerning sequestration 
under active investigation which may shed further insights into this 
problem in the near future.
    Question 4. The report states that a special need is to increase 
the observational and research capabilities in many regions, 
particularly in developing countries. How is this need being addressed 
by the International community and how much will it cost?
    Answer. I will confine my remarks here only to the principal 
shortcomings. A key point to note is that observational networks are on 
the decline. Long-term monitoring of climate variables--even the most 
common and obvious ones, such as surface temperature and precipitation, 
are not being done with the spatial distribution and frequency that is 
necessary to achieve a comprehensive documentation of regional climate 
variations and change. The problem exists to varying degrees in all 
parts of the world, but is especially acute in the developing 
countries. Lack of adequate and sustained funding, the high cost of 
initiating and maintaining reliably measuring equipment, are major 
issues. There are, however, other factors as well, such as the lack of 
an appreciation of the significance of long-term monitoring, which 
inhibits a sustained high-quality data collection. Further, data 
gathering tends to not be a high-visibility exercise. The worth of such 
routine measurements does not really show up till at least a decade's 
worth of data has been collected. By then, due attention to such 
important technical issues as instrument maintenance and consistency in 
program management usually tend to wane, resulting in the difficulty of 
compiling a reliable dataset. Insofar as developing countries are 
concerned, the problems include acquisition of state-of-the-art 
equipment, ability to sustain funds for maintenance, and quality 
control. A recurring problem is the lack of well-trained human-power. 
As is true even the developed world, the scientific challenge posed by 
climate change detection is unable to compete with the marketplace 
attraction of other professions. Very few scientists' careers have 
advanced solely as a consequence of painstaking data collection over a 
long period of time, a timescale that is also considerably longer than 
typical program management tenure and fiscal considerations. Thus, 
especially among young scientists worldwide, there is a lack of a 
motivation to undertake these routine but necessary observations. This 
holds true in both developed and developing countries.
    Automation and advances in remote sensing, which would obviate the 
need for humans to attend to the observational tasks, are not yet in 
full gear in this field in the developing countries. Amidst the 
pessimism, however, it is important to point out that some 
observational activities have indeed flourished e.g., measurements of 
CO2 at a few sites around the world for the past 3 decades 
and more. This effort is particularly exemplary and is worth emulating 
for other climate variables as well.
    The situation with regards to modeling capabilities, and diagnostic 
analyses combining models and observations is not dissimilar from the 
tenor of the issues plaguing observational datasets, as noted above. 
The lack of talented minds applying themselves to science in general 
and to this scientific aspect in particular needs to be improved. There 
is a need to improve this situation especially in the developing 
countries, where the educational and scientific infrastructure are at 
times too weak to sustain a orderly, long-term research commitment. 
International research organizations are trying hard to remedy the 
situation, but are being strained by funding inadequacy and the need to 
keep pace with the growing complexity of the climate system.
    Question 5. What would you say is most urgent in terms of future 
research needs?
    Answer. It is useful to summarize here IPCC 2001 `s statements on 
future research needs. These are an appropriate recognition of the 
needs in the present times, based on considerations stemming from the 
current assessment of climate change science. Note that IPCC itself 
does not make any recommendations on prioritization or funding plans, 
nor is it associated with or endorses any national/international 
    First, systematic observations and reconstructions of past climates 
need to be sustained and improved wherever possible. Observations 
include those that are designed to understand the processes, as well as 
those that are specifically geared towards long-term monitoring of key 
climate variables. The elements include: arresting and reversing the 
decline of observational networks; sustaining and expanding the 
observational foundation of climate studies by providing accurate, 
long-term, highly reliable and consistent data, including 
implementation of strategies for integrated and well-coordinated global 
observations; enhancing development of reconstruction of past climate 
periods; improving observations of the spatial and temporal 
distributions of greenhouse gases and aerosols; sustaining measurements 
that monitor forcing agents and climate feedback processes; 
improvements in observations of the world's oceans including ocean 
thermal changes (this may prove to be an optimal item to measure the 
increasing heat content of the climate system).
    Second, improvements in modelling and process studies are needed to 
improve the quantitative realism of the simulated climate system. These 
include: improved understanding of the physical and chemical mechanisms 
that lead to a forcing of climate change; understanding and 
characterizing the important unresolved processes, and physical and 
biogeochemical feedbacks in the climate system; improved methods to 
quantify uncertainties of climate projections and scenarios, including 
long-term ensemble simulations using complex but well-understood 
models; improving the integrated hierarchy of global and regional 
climate models, with a focus on the simulations of climate variability, 
regional climate changes and extreme events; linking more effectively 
models of the physical climate and the biogeochemical system, and in 
turn improving the coupling with other factors intrinsically associated 
with human activities.
    There is a vital research element to be added to the above viz., an 
appropriate synthesis of the observations and model simulations leading 
to a scientifically, well-grounded picture of climate change and its 
causes. Rigorous diagnostic analyses of observations and model 
simulations are critically needed in unravelling the evolution of 
climate change. Lastly, in the sequence, it cannot be overemphasized 
enough that each successive piece of knowledge gained, whether in 
modeling, observations or diagnostic analyses, needs to be gainfully 
used to plan better observational strategies and to improve further 
upon the model simulations/projections of climate change.
    It is vital that there be a balanced approach that weighs in both 
observations and modeling studies. In particular, the build-up of the 
infrastructure and funding plans must recognize this point. For 
instance, observations should guide the science of what forcings are 
operating, what are the feedbacks, how should we be modeling these, 
what are the results of the simulations, how robust are they, how do 
they compare with various climate parameters, why is there a 
disagreement or why is there a good agreement, what can we relay back 
to the observational infrastructure so that they can receive better 
guidance. The idea should be to continually enhance the confidence in 
the climate forcings, feedback mechanisms, and responses, consistent 
with the central focus of understanding climate variations and changes.
    Question 6. You have mentioned that the best agreement between 
observations and model simulations over the past 140 years is found 
when both human-related and natural climate-change agents are included 
in the simulations. Why is it important for the model simulation to 
include both?
    Answer. In order to investigate the long-term climate change, model 
simulations of climate change have considered four different 
possibilities: (a) unforced internal variability of the nonlinear 
coupled atmosphere-ocean system i.e., the climate variations that occur 
even in the absence of any forcing; (b) climate change due to the 
introduction of ``natural'' factors such as solar irradiance changes 
and volcano-induced enhancement of stratospheric aerosol 
concentrations; (c) climate changes when only ``anthropogenic'' factors 
(e.g., emissions of greenhouse gases and aerosols) are considered; and 
(d) when all the factors are considered in unison. This modus operandi 
enables the identification of specific causal factors and aids in 
framing the detection-attribution analyses.
    The climate model simulations performed indicate that it is very 
unlikely that internal variability of the climate system alone can 
explain the past 140 years' observed surface temperature record. Three 
different models (one of them from NOAA) are in agreement on this 
finding. The models' surface temperature interdecadal variation is not 
inconsistent with that observed over the past 140 years. A model 
simulation without consideration of the water vapor feedback yields far 
less variability than evidenced in the observations, suggesting that 
the manner in which this feedback is represented in the models may be 
qualitatively consistent with reality. Owing to the lack of a long 
record in atmospheric observations, there tends to be a reliance on 
climate models for estimates of the unforced climate variability. 
Although this is a limitation, there are tests that climate models have 
successfully met in this regard.
    ``Natural'' factors alone cannot account for the observed warming 
over the past 140 years, although there are suggestions that over the 
first half of the 20th century, these factors may have contributed to 
the warming occurring at that time. In particular, solar irradiance 
changes may have contributed to the observed warming during the first 
half of the 20th century. Although episodic volcanic eruptions exert 
impacts during the 1-2 years that they enhance stratospheric aerosol 
concentrations, their effects over the past century are less relative 
to those due to the secular changes in greenhouse gases. Model 
simulations with ``anthropogenic'' factors alone indicate that, despite 
uncertainties in the quantitative estimates of the forcing, their 
influence in the model simulations can be associated with the rapid 
rise in the observed warming over the latter half of the 20th century.
    When considering the entire modern instrumental surface temperature 
record, it becomes clear that both ``natural'' and ``anthropogenic'' 
factors need to be considered for the simulation of the observed 
temperature record. This includes the Sun's output changes as well as 
the particularly active volcanic period in the 1880-1920 and 1960-1991 
time periods. For a proper explanation of climate change, and to 
distinguish between the natural factors and anthropogenic species, 
these factors must be juxtaposed with the internally generated 
      Response to Written Questions Submitted by Hon. John McCain 
                          to James J. McCarthy
    Question 1. Why would climate changes in the 21st century be 2-10 
times faster than those of the 19th century?
    Answer. On pp. 30-31 of the oral testimony transcript I am 
correctly quoted as having made a statement like this in comparing 
rates of climate change between the 21st century and the 20th (not the 
19th) century.
    More specifically, this comparison is between the rates of global 
mean temperature change. For the 20th century this rate was 0.6C (1.0F) 
per century. For the 21st century, the scenarios project a range of 
increases between 1.4C (2.5F) and 5.8C (10F). This comparison is the 
root of the 2-10 fold comparisons.
    Question 2. Your written testimony states that even the most 
optimistic scenarios for mitigating future climate change are unlikely 
to prevent significant damage from occurring. What type of events would 
qualify as significant damage?
    Answer. Extrapolating from the changes that have occurred in the 
last few decades in the distributions and timing of seasonal biological 
phenomena, accelerating some of these by 2-10 times in the current 
century may push some species over the edge. Prime examples are 
tropical and Arctic systems, where temperature limits for some species 
like coral may be exceeded, and the ice habitat for many organisms, 
like pregnant polar bears needing the high fat nourishment of seals, 
may be lost.
    Most problematic, though, are the impacts on human systems related 
to extreme climate events. Table 1 in the Working Group I SPM indicates 
levels of confidence in extreme weather and climate observations over 
the past 50 years and projections in the next 50 years. Table 1 in the 
Working Group II SPM lists representative examples of projected impacts 
from these extreme events. Extrapolating from the tolls in lives, 
livelihoods, and properties caused by the flood and mudslide disasters 
in the past 5-10 years to the projected future provides good examples 
of likely significant damage.
    Question 3. There has been and continues to be a major discussion 
on how to reduce emissions. How can we best prepare people and systems 
for the disruption that will ensue with the climate change that is now 
projected for the 21st century?
    Answer. This is in my estimation one of the most critical questions 
that we face. The scenarios mentioned above that yield the range of 
1.4-5.8C increases are representatives of classes of scenarios (35 were 
used) that have several variable components. These include the 
projections for human population numbers over the next century, our 
standard of living and socioeconomic conditions in the developed and 
developing world, and the fossil-fuel intensity of our energy producing 
activities. The last of these is the one that is most easily altered 
with minimal impact on the other conditions.
    While an optimist will suggest that it is unlikely that we will 
climb steeply up the highest of these slopes, a realist will also 
suggest that it is unlikely that we be able to stay close to the lowest 
of these slopes. Partly this is due to the socioeconomic and 
geophysical inertia in our energy systems. While it is easier to 
modulate the use of fossil fuel, and especially to switch to 
alternative sources of energy, than it is to reduce the world's human 
population numbers, the difficulties in changing human behavior and 
human institutions are enormous. At the same time, since CO2 
emitted today will be still be in the atmosphere a century from now, 
everything we do now to reduce rates of emission will pay increasing 
dividends in the future.
    This having been said, it is clear that we must also prepare for 
the sort of increasing prospect of damage mentioned in #2 above by 
enhancing adaptation. This is particularly critical in the regions 
hardest hit where adaptive capacity is the least (tropics and 
subtropics). Serious attention must be given to the potential impacts 
on the availability of safe water, subsistence agriculture, and human 
    How the scenarios mentioned above play out will greatly influence 
the rate of sea level rise. A large component of sea level rise is due 
to the expansion of the ocean as it warms. The convection of heat from 
the surface ocean to deeper waters is a slow process. A greater rate of 
atmospheric warming early in this century followed by a slower rate of 
warming later in the century will have a stronger effect on sea level 
rise within the next 100 years than a slow warming followed by a fast 
warming that would have atmospheric temperature at the same point 100 
years from now. Coastal zones and small island states are vulnerable to 
this aspect of climate change and even more so with increases in peak 
storm wind and precipitation intensities. Planning for coastal human 
settlements, their infrastructures, and resources (like ground water) 
must be prepared to consider adaptive strategies that can minimize 
these impacts. Indigenous communities may in some instances be 
especially vulnerable, such as in the case mentioned for Alaska by 
Senator Stevens.
    Question 4. Can you discuss some of the impacts of climate change 
on public health?
    Answer. Impacts of potential climate change on human health are 
given a full chapter in the Working Group II report, and this is 
summarized in section 3.5 of the SPM. Broad categories include negative 
consequences of increasing thermal stress, the impacts of storms, and 
increases in the areal extent or seasonal duration of certain 
infectious diseases. In some areas there may be positive aspects of 
climate change for human health, such as with diminished winter 
mortality, but it is important to emphasize that the negative aspects 
will disproportionately hit the tropical and subtropical regions. An 
obvious adaptive strategy would be to enhance public health 
institutions and resources. Since these are woefully inadequate in many 
areas today, successful adaptation will take a concerted effort the 
likes of which is without any obvious precedent.
    Question 5. How significant was last summer('s) passage of a ship 
through the Northwest Passage without touching ice? Has shipping 
traffic increased?
    Answer. There is something symbolic and sobering about this 
observation. Had it occurred any time before in the last 150-200 years 
it would have been evident in the accounts of sealing and exploring 
vessels. It is possible that the thinning and loss of areal extent of 
summer ice in the Arctic Ocean and adjacent regions may be the result 
of a long term natural cycle, but the period of such a cycle must be 
longer than a few hundred years, and no known or hypothesized mechanism 
has this potential. Climate models have forecast diminished Arctic 
summer ice with continued greenhouse gas--forced warming, but the rates 
were less than has been observed in the last few years.
    At this moment there are probably many commercial enterprises that 
are exploring options for capitalizing on the diminished ice in the 
Northwest Passage. Canadian claims regarding access through its Arctic 
archipelago are certainly an issue that that will require careful 
consideration by nations wishing to anticipate increased shipping 
potential through the Northwest Passage.
    Question 6. You have mentioned how some species are being driven 
from their natural habitats because of changing environmental 
conditions due to increasing temperatures. How many species have been 
declared extinct because of these weather patterns changes?
    Answer. As I stated in my testimony, it is not clear that any of 
the changes in distribution of species and the timing of biological 
processes (that can be plausibly liked to local climate change) have 
led to the loss of any species. Habitat destruction and the intentional 
and accidental introduction of invasive species have caused several 
extinctions, especially on islands. These may continue to be larger 
factors than climate change with regard to extinctions, but in the 
Arctic and the tropical ocean this condition may not hold--climate 
change may dominate. There are synergistic interactions among some of 
these factors, such as climate change prompting relocation of species, 
which is then hindered by land-use change that has interrupted 
migration corridors.
      Response to Written Questions Submitted by Hon. John McCain 
                         to Dr. James E. Hansen
    Question 1a. You mentioned that your alternative scenario assumes 
that air pollution is not allowed to get any worse than it is today and 
that global use of fossil fuels will continue at about today's rate. It 
also assumes no net growth of the other forcings. What are those other 
    Answer. They are included in Figure 2 of my submitted testimony. 
Chief among them are methane, tropospheric ozone and black carbon 
(soot) aerosols.
    Question 1b. Does the IPCC business as usual scenario assume that 
air pollution is stable?
    Answer. No, They have ozone and methane increasing substantially. 
In addition, they grossly underestimate the climate forcing by black 
carbon, and thus their scenarios tend to ignore it. Since air pollution 
is excluded from the Kyoto Protocol, it receives little attention in 
the IPCC scenarios.
    Question 1c. Do these differences in assumption account for the 
differences in expected temperature increases in the next 50 years for 
the two scenarios? And again what are the temperature differences?
    Answer. As shown in Figure 5 of my submitted testimony the 
additional warming in the next 50 years is about 1.6C in the business-
as-usual scenario and about 0.75C in our alternative scenario. 
Moreover, the business-as-usual scenario ``builds in'' a much larger 
later warming, which will appear in the latter half of the century.
    The smaller warming in the alternative scenario is due to the two 
assumptions: (1) it will be possible to stop further growth of non-
CO2 forcings (loosely labeled ``air pollution''), 
particularly ozone, black carbon and methane, (2) it will be possible 
to keep the growth of atmospheric CO2 to about 75 parts per 
million in the next 50 years, which would require that CO2 
emissions remain roughly similar to today's rate or decline slightly.
    Question 2. You mentioned in your statement that the judge of 
science is observations. You also mentioned the potential educational 
value of keeping an annual public scorecard of measured changes. Can 
you elaborate on this idea?
    Answer. It is briefly elaborated upon in reference 22 of my 
submitted testimony, where I mention an annual public scorecard of (1) 
fossil fuel CO2 emissions, (2) atmospheric CO2 
amount, (3) human made climate forcing, (4) global temperature. I will 
try to write a paper with a more a more comprehensive discussion in the 
near future. One obvious addition would be an annual measure of 
CH4 emissions and atmospheric amounts. However, the single 
most important benchmark for the United States is probably an annual 
update of the bar graph in Figure 11 of my testimony. i.e., the annual 
growth of CO2 emissions the annual growth needs to be 
reduced to zero or slightly negative.
    Question 3. Do you feel that your results were reviewed and 
properly considered as part of the IPCC process?
    Answer. No. IPCC's size and review procedures make it inherently 
lethargic, so responding to a mid-2000 paper is difficult. However, the 
real problem is probably the close binding between IPCC and the Kyoto 
Protocol discussions. Kyoto excludes consideration of air pollution 
(such as tropospheric ozone and black carbon), for example, so IPCC 
basically ignores these topics and downgrades them. The only IPCC 
``review'' of our paper was by the IPCC leaders (as reported in the New 
York Times, for example), who saw our paper as potentially harmful to 
Kyoto discussions. They received the backing of organizations (such as 
the Union of Concerned Scientists, who commissioned a criticism of our 
paper that I respond to in reference 22) and publications (particularly 
Nature), who had previous editorial positions favoring the Kyoto 
Protocol. When I had difficulty publishing a response in Nature, I 
wrote an open letter that is available at http://naturalscience.com/ns/
    Question 4. You mentioned that the climate cannot respond 
immediately to a forcing because of the long time needed to warm the 
oceans. How would we measure the real impact of reducing the amount of 
greenhouse gases in the atmosphere in the short term?
    Answer. We should of course measure the individual greenhouse gases 
as the best measure of short-term effectiveness of any attempts to 
reduce emissions. However, the best measure of the impact of the net 
climate forcing is likely to be heat storage in the ocean. Natural 
variations of this rate will occur because of the dynamics of the 
system. but if the measurements are accurate and maintained for years 
they will soon begin to provide us with a great tool for understanding 
where the future climate is heading.
               A Brighter Future--by Dr. James E. Hansen
    Contrary to Wuebbles' thesis (2002), most of the media did not 
misunderstand the thrust of our recent paper (Hansen et al., 2000). We 
do indeed assert that a scenario is feasible in which the rate of 
global warming declines. We also posit that, with an understanding of 
the significant climate forcings, it is possible to achieve such a 
climatically brighter path with actions that are not ``economically 
wrenching'', indeed, actions that make economic sense independent of 
global warming.
    Our paper does not denigrate the ``business-as-usual'' (BAU) 
scenario that has been popular in global climate model simulations. The 
BAU scenario provides a valuable warning of potential climate change if 
the world follows a path with climate forcings growing more and more 
rapidly. Our aim was to present a companion scenario that stimulates 
discussion of actions that help avoid a gloom and doom scenario. I 
tried to clarify our objectives in an ``Open Letter'', which is made 
available from Climatic Change I summarize here key points of 
    Black Carbon (BC). One of our assertions is that BC (soot) plays a 
greater role in climate change than has been appreciated. We believe 
that the forcing due to BC is of the order of 1 W/m\2\, rather than of 
the order of 0.1 W/m\2\, as assumed by IPCC (1996).
    My present estimate for global climate forcings caused by BC is: 
(1) 0.40.2 W/m\2\ direct effect, (2) 03015 W/
m\2\ semi-direct effect (reduction of low-level clouds due to BC 
heating; Hansen et al., 1997), (3) 0.10.05 W/m\2\ ``dirty 
clouds'' due to BC droplet nuclei, (4) 0.20.01 W/m\2\ snow 
and ice darkening due to BC deposition. These estimates will be 
discussed in a paper in preparation. The uncertainty estimates are 
subjective. The net BC forcing implied is 10.3 W/m\2\.
    Air Pollution. Aerosols and tropospheric ozone (O3) are 
not addressed by the Kyoto protocol. They should be. A reason proffered 
for excluding ozone is that its chemistry is so complex that ``most 
scientists'' eyes glaze over'' (Revkin, 2000). Perhaps the latter 
assertion is true. But it is not adequate reason to exclude air 
pollution from international climate negotiations. Our estimated 
anthropogenic global climate forcing due to BC (1 W/m\2\) and O3 
(0.4 W/m\2\) is comparable to the CO2 forcing (1.4 W/m\2\). 
One thesis in our paper is that halting the growth of air pollution can 
make a significant contribution to slowing global warming.
    Effects of air pollution on humans are large in the developed world 
and staggering in the developing world. A recent study (Kunzli et al., 
2000) estimates that particulate air pollution in France, Austria and 
Switzerland takes 40,000 lives annually with health costs equal to 1.6% 
of the gross national products. An example for the developing world is 
the estimate (Smith, 2000) that 270,000 Indian children under 5 years 
old die annually from acute respiratory infections caused by air 
pollution. Most of the pollution in this latter case arises from indoor 
combustion for cooking and heating, a primary source of the cloud of 
pollutants now mushrooming from India and China. Aerosols and ozone 
also reduce agricultural productivity with costs of many billions of 
    Practical benefits of air pollution reduction accrue immediately, 
not in 100 years. We assert in our paper that this offers an 
opportunity to reduce the climate problem with a cooperative approach 
that has immediate clear benefits to both developing and developed 
    Methane. We conclude that climate forcing by CH4 is 0.7 
W/m\2\, fully half as large as the forcing by CO2. Observed 
growth of CH4 is not accelerating, contrary to assumptions 
in many climate scenarios. Indeed, the growth rate has declined by two-
thirds in the past 20 years. However, future trends are uncertain.
    The task of understanding CH4 should be jumped on, like 
a chicken on a June bug. Yet research support has been minuscule. We 
need quantitative understanding of CH4 sources and sinks to 
define optimum policies. It may be possible to find practices that 
reduce methane emissions while saving money. Farmers want cows and 
beasts of burden to produce milk, meat, and power, not methane. Rice 
growers seek food and fiber, not methane, but we must also compare 
impacts of altered practices on N2O production. There is 
much potential for methane capture via improved mining and waste 
management practices.
    Scenarios. Science works via iterative comparison of theory and 
observations. Differences found are not a problem--on the contrary, 
only by discovering and investigating these can our understanding 
advance. One problem with the IPCC reports is that each report produces 
new (and more numerous) greenhouse gas scenarios with little attempt to 
discuss what went wrong with the previous ones. As a result, dramatic 
changes that have occurred since the 1980s in prospects for future 
climate forcings receive inadequate attention.
    Figure 1 shows climate forcing scenarios used for climate 
simulations in the 1980s (Hansen et al., 1988). The actual climate 
forcing in 2000 is close to that of scenario B, and the derivative 
(growth rate) is less than that of scenario B. Further slowdown is 
needed to achieve the path of the ``alternative scenario''. The fact 
that the real world does not now seem to be following a path toward the 
median of the greenhouse gas amounts projected by Ramanathan et al. 
(1985) for 2030 in no way detracts from that paper, which, in my 
opinion, was one of the most stimulating papers in atmospheric sciences 
during recent decades. Indeed, to at least a small extent, one might 
credit the slowdown in climate forcing growth rates to the warning 
implicit in this and related papers.
    Why have growth-rates fallen below BAU scenarios? One clear reason: 
the Montreal Protocol, which forced a phase-out of CFCs. That is an 
example of what we propose: actions useful for other reasons that also 
help to slow climate change. Reasons for the decline in the CH4 
growth rate need to be understood better. The apparent flattening of 
the CO2 growth rate is probably due in part to an increased 
CO2 sink, which may (or may not) be a temporary phenomenon.
    CO2 scenarios are the most critical. Our approach, 
characterized as naive by Wuebbles, emphasizes observations. We note 
that the growth rate of CO2 (fossil fuel) emissions has 
declined from about 4%/year to 1%/year in recent decades. It is 
noteworthy that the current IPCC (2001) scenarios have a growth rate in 
the 1990s that is almost double the observed rate of 0.8%/year (linear 
trend fit to 5-year running mean), but it is consistent with their 
failure to emphasize data. I will not characterize the IPCC approach 
defended by Wuebbles, but I note in my open letter the difficulty 
inherent in multiplying assumptions about population, economic 
development, and technology 50 or 100 years in the future. In my letter 
I specifically discuss their population estimates, which already appear 
to be unduly pessimistic.
    Media and the Public. Wuebbles claims that the press misunderstood 
our paper. I believe that he fails to see the forest for the trees. The 
media do not always get technical details correct, as scientists know 
well. Moreover, media often have editorial positions and put their own 
spin on news stories. I complain in my open letter about an exceptional 
case in which Nature disguised their editorial position as a ``news'' 
article in which they report only criticisms of our paper. However, 
overall the media deserve credit for correctly conveying the thrust of 
our perspective on climate change. Indeed, the Washington Post 
editorial discussed in my open letter is, in my opinion, an astute 
assessment of the issues.
    A basic problem is that we scientists have not informed the public 
well about the nature of research. There is no fixed ``truth'' 
delivered by some body of ``experts''. Doubt and uncertainty are the 
essential ingredient in science. They drive investigation and 
hypotheses, leading to predictions. Observations are the judge.
    Sure, some things are known with higher confidence than others. Yet 
fundamental issues as well as details are continually questioned. The 
possibility of finding a new interpretation of data, which provides 
better insight into how something in nature works, is what makes 
science exciting. A new interpretation must satisfy all the data that 
the old theory fit, as well as make predictions that can be checked.
    The suggestion that BC causes a forcing of about 1 W/m\2\ is a 
possible example. Observations required to verify the forcing are 
extensive, because it is the sum of several effects. Perhaps 
recognition of the BC forcing will allow IPCC to include fully the 
negative direct and indirect forcings of sulfate and organic aerosols, 
something that they have been reluctant to do. There is still much to 
be learned.
    In my letter I note the potential educational value of keeping an 
annual public scorecard of measured changes of (1) fossil fuel CO2 
emissions, (2) atmospheric CO2 amount, (3) human-made 
climate forcing, and (4) global temperature. These are well-defined 
quantities with hypothesized relationships. It is possible to make the 
science understandable, and it may aid the discussions that will need 
to occur as years and decades pass. It may help us scientists too. I am 
curious, for example, whether the IPCC (1996) conclusion that fossil 
fuel CO2 emissions must be cut by 80% to stabilize 
atmospheric CO2 at 550 ppm will be supported by empirical 
data as it accumulates.
    Strategic Considerations. Wuebbles states that our scenario can not 
be ``used in any sense as a strategy, particularly given the 
inhomogeneities in the aerosol distribution and radiative forcing''. We 
do not try to specify a detailed strategy for dealing with global 
warming (nor does Wuebbles or IPCC). However, we do present an outline 
of a strategy and argue that its elements are feasible.
    It is impractical to stop CO2 from increasing in the 
near term, as fossil fuels are the engine of the global economy. 
However, the decline of the growth rate of CO2 emissions 
from 4 to 1%/year suggests that further reduction to constant emissions 
is feasible, especially since countries such as the United States have 
made only modest efforts at conservation. The potential economic and 
strategic gains from reduced energy imports themselves warrant the 
required efforts in energy conservation and development of alternative 
energy sources.
    The other requirement in our alternative scenario is to stop the 
growth of non-CO2 forcings, which means, primarily, air 
pollution and methane. The required actions make practical sense, but 
they will not happen automatically and defining the optimum approach 
requires research.
    A strategic advantage of halting the growth of non-CO2 
forcings is that it will make it practical to stop the growth of 
climate forcings entirely, in the event that climate change approaches 
unacceptable levels. The rationale for that claim is that an ever-
growing fraction of energy use is in the form of clean electrical 
energy distributed by electrical grids. If improved energy efficiency 
and non-fossil energy sources prove inadequate to slow climate change, 
we may choose to capture CO2 at power plants for 
    Global warming is a long-term problem. Strategies will need to be 
adjusted as we go along. However, it is important to start now with 
common sense economically sound steps that slow emissions of greenhouse 
gases, including CO2, and air pollution. Early emphasis on 
air pollution has multiple immediate benefits, including the potential 
to unite interests of developed and developing countries. Barriers to 
energy efficiency need to be removed. Research and development of 
alternative energies should be supported, including a hard look at next 
generation nuclear power. Ultimately strategic decisions rest with the 
public and their representatives, but for that reason we need to make 
the science and alternative scenarios clearer.
    Finally, an amusing thing about Wuebbles'' criticism is the space 
devoted to noting that, even if there is some cancellation of global 
mean forcings by aerosols and gases, there may still be climate effects 
due to the geographical inhomogeneity of the net forcing. That's right. 
However, he fails to recognize that reduction of particulate air 
pollution will reduce this inhomogeneity, not increase it.
    Hansen, J., Fung, I., Lacis, A., Rind, D., Lebedeff, S., Ruedy, R., 
Russell, G., and Stone, P.: 1988, ``Global Climate Changes as Forecast 
of Goddard Institute for Space Studies Three-Dimensional Model'', J. 
Geophys. Res. 93, 9341-9364.
    Hansen, J., Sato, M., and Ruedy, R.: 1997, ``Radiative Forcing and 
Climate Response'', J. Geophys. Res. 102, 831-6864.
    Hansen, J., Sato,M., Ruedy, R., Lacis, A., and Oinas, V.: 2000, 
``GlobalWarming in the Twenty-First Century: An Alternative Scenario'', 
Proc. Nat. Acad. Sci. 97, 9875-9880.
    Intergovernmental Panel on Climate Change: 1996, in Houghton, J. 
T., Meira Filho, L. G., Callander, B. A., Harris, N., Kattenberg and 
Maskell, K. (eds.), Climate Change 1995, Cambridge University Press, p. 
    Kunzli, N., Kaiser, R., Medina, S., Studnicka, M., Chanel, O., 
Filliger, P., Herry, M., Horak, F., Puybonnieux-Texier, V., Quenel, P., 
Schneider, J., Seethaler, R., Vergnaud, J. C., and Sommer, H.: 2000, 
``Public-Health Impact of Outdoor and Traffic-Related Air Pollution: A 
European Assessment'', The Lancet 356, 795-801.
    Ramanathan, V., Cicerone, R. J., Singh, H. B., and Kiehl, J. T.: 
1985, ``Trace Gas Trends and their Potential Role in Climate Change'', 
J. Geophys. Res. 90, 5547-5566.
    Revkin, A. C.: 2000, ``Debate Rises over a Quick(er) Climate Fix'', 
New York Times, October 3.
    Smith, K. R.: 2000, ``National Burden of Disease in India from 
Indoor Air Pollution'', Proc. Nat. Acad. Sci. 97, 13286-13293. 

              [From The Washington Post, August 28, 2000]

                          Hot News on Warming

    If you're trying to decide whether to be an optimist or a pessimist 
on global warming, recent news is enough to leave you dizzy. An 
icebreaker found open water at the North Pole, prompting a new wave of 
attention to the thinning polar ice cap. That seemed like bad news, 
although some oceanographers said summertime cracks in Arctic ice 
aren't new, and this one shouldn't be over-interpreted. Texas, the 
state that produces the most greenhouse gas emissions, for the first 
time took steps to study the extent of those emissions and consider 
possible ways to reduce them. That was good news, although it doesn't 
guarantee state action. And Dr. James Hansen, a leader in drawing 
government attention to global warming, published a report suggesting 
that it may be ``more practical to slow global warming than is 
sometimes assumed'' by focusing in the short term on cutting heat-
trapping gases other than carbon dioxide. That was surprising news, at 
least to those of us who have seen the climate-change fight centering 
on reducing carbon dioxide emissions.
    It's long been known that carbon dioxide isn't the only gas that 
helps hold heat in the atmosphere. Six ``greenhouse gases'' were 
included in the Kyoto protocol, the international agreement that calls 
for cutting emissions by 2012. But carbon dioxide, the most abundant 
greenhouse gas, has dominated the public debate. It has been a subject 
of contention because it is a byproduct of burning fossil fuels, such 
as coal and gas, that drive modern industrial society. American 
opponents of the Kyoto protocol have argued that the reductions it 
requires could wreck the economy.
    Dr. Hansen and a team of colleagues wrote that most of the global 
warming so far observed actually has come from other greenhouse gases 
such as methane, chlorofluorocarbons, and gases that combine to create 
ozone in smog. They suggested a strategy of focusing first on cutting 
those gases and black particles of soot that also trap heat. Some of 
the gases involved are already in decline because of other 
international restrictions; going after others amounts to an attack on 
air pollution, which the scientists argue should be attractive action 
in all parts of the world, independent of concerns about warming, 
because of the health benefits of cleaner air.
    That optimistic scenario immediately caused some environmentalists 
to worry that the report would become a weapon for those who are 
skeptical about warming--who oppose any action. Dr. Hansen himself said 
it undoubtedly will be used that way, but that would be a misreading of 
the study. The new report does not challenge either the evidence that 
surface temperatures are going up or the growing consensus that human 
activities are contributing to the increase. It continues to cite the 
need for reductions in carbon dioxide emissions. There is no 
suggestion, nor should there be, that response to global warming should 
wait until the science is more certain.
    What it does do is remind us that climate issues are complex, far 
from fully understood and open to a variety of approaches. It should 
serve as a caution to environmentalists so certain of their position 
that they're willing to advocate radical solutions, no matter what the 
economic cost. It suggests that the sensible course is to move ahead 
with a strong dose of realism and flexibility, focusing on approaches 
that are economically viable, that serve other useful purposes such as 
cutting dependence on foreign oil or improving public health, and that 
can help support international consensus for addressing climate change. 
If the Hansen report pushes the discussion in that direction, it will 
turn out to be good news indeed.

       [From the International Herald Tribune, November 16, 2000]

              Try a Commonsense Response to Global Warming

                           (By James Hansen)

    New York.--Evidence continues to build that the world is slowly 
getting warmer. Almost all mountain glaciers are retreating. It was 
discovered this year that even the deep ocean is warming. On Earth's 
surface, where people live, the average warming is now about half a 
centigrade degree in the past 100 years.
    Half a degree seems hardly noticeable. It is much less than weather 
fluctuations that occur every day. But it is a warning of possibly 
large climate changes as the 21st century progresses.
    One worry is sea level, which will rise as glaciers melt and as 
ocean water expands from warming. A rise of a meter, a possibility this 
century, would submerge island nations such as the Maldives and the 
Marshall Islands, and it would be devastating to people living in 
Bangladesh and on the Nile Delta.
    The greatest effect of global warming for most people may be an 
increase in extreme weather. Global warming is expected to cause more 
droughts and forest fires. It increases evaporation, which will lead, 
at other times and places, to heavier rainfall and floods.
    The forces that drive global warming are no surprise. They are 
mainly the gases and fine particles that humans have been dumping into 
the atmosphere for many years. The gases, especially carbon dioxide and 
methane, absorb Earth's heat radiation and thus warm the surface, just 
as a blanket traps body heat. Fine particles of soot (black carbon) 
warm the air by absorbing sunlight.
    Other human-made fine particles, especially sulfates, are nearly 
white. Sulfates come from sulfur in coal and oil, which is released to 
the atmosphere when these fossil fuels are burned. Sulfates cool Earth 
by reflecting sunlight back to space.
    The net effect of these human emissions is not accurately known, 
because the fine particles are not yet measured well. But it is 
estimated that the net heating is at least one watt, perhaps closer to 
two watts, per square meter. Such a human forcing of climate is 
comparable to increasing the brightness of the sun by 1 percent.
    Earth responds slowly to such forcings. The thermal inertia of the 
ocean delays the response. It takes decades for most of the response to 
occur, and centuries for the full response.
    The question we face today is how much more we should allow human 
climate forcing to grow. That question is being addressed now in The 
Hague by the world's nations.
    These deliberations are guided by climate simulations carried out 
by the Intergovernmental Panel on Climate Change. The simulations focus 
on a gloomy scenario in which it is assumed that humans will burn coal, 
oil and gas at faster and faster rates.
    This gloomy scenario leads to an additional forcing of three watts 
in the next 50 years. Such a forcing will almost surely lead to 
increases in climate extremes and a rising sea level.
    Some increase in human climate forcing is inevitable. Fossil fuels 
are our primary source of energy. Because of the energy infrastructure, 
it requires decades to phase in new technologies that may produce less 
carbon dioxide.
    However, we recently suggested a scenario that reduces the human 
forcing to only one watt in the next 50 years. This would yield a more 
moderate climate change, allowing time to understand climate change 
better and develop technologies and strategies to deal with it.
    There are two elements in this commonsense solution to global 
warming. First we must stop the growth of air pollution. This would 
eliminate any added climate forcing by constituents other than carbon 
dioxide. Second we must burn fossil fuels, and thus emit carbon 
dioxide, no faster than we do today. That means that growing energy 
needs must be met by increased efficiencies in current uses and by 
introducing technologies that produce little or no carbon dioxide.
    Both elements are achievable but unlikely to happen by accident. 
Technologies that reduce air pollution have to be applied. Annual 
growth of carbon dioxide emissions, which has already slowed from 4 to 
1 percent per year, must be slowed a bit further to zero growth or a 
small decrease.
    Many actions could reduce both air pollution and carbon dioxide 
emissions. We need to develop clean fuels and renewable energy sources, 
and remove barriers to energy efficiency. Improved technology, perhaps 
including fuel cells and hydrogen power, can help reverse the trend to 
greater gas-guzzling vehicles. Utility profits should be designed to 
reward improved efficiency and decreased air pollution.
    Improved energy efficiency, cleaner uses of fossil fuels and 
development of renewable energy sources will have multiple benefits. In 
addition to slowing the growth of carbon dioxide, this will create 
jobs, improve economic competitiveness, reduce reliance on foreign 
sources of energy and improve public health.
    Fine particles in air pollution, including soot, sulfates and 
organic aerosols, penetrate human tissue deeply, causing respiratory 
and cardiac problems. A recent study found that air pollution in 
France, Austria and Switzerland alone accounts for 500,000 asthma 
attacks and 40,000 deaths per year. Air pollution in developing 
countries, such as India and China, is even more severe.
    International cooperation is needed, because emissions circulate 
worldwide. But benefits of progress, in climate stabilization and 
health, will be similarly widespread. Required cooperation, including 
technology transfer, can include incentives and economic opportunities 
for all parties.
    The commonsense approach is to move forward by attacking air 
pollution, improving energy efficiency and developing renewable energy 
sources. This approach is economically sound and has collateral 
benefits. It should provide a meeting ground for persons from a wide 
spectrum of political viewpoints, all of whom wish to preserve the 
     Responses to Written Questions Submitted by Hon. John McCain 
                       to Dr. Richard S. Lindzen
    Question 1. Your written statement refers to the limitations of 
computer models. In two recently released studies, computer models 
showed that the ocean warming that has been measured over the last 
half-century is exactly what would he expected from the amount 
greenhouse gases that have been emitted into the atmosphere. Tim 
Barnett of Scripps Institution of Oceanography is quoted as saying 
``This will make it much harder for naysayers to dismiss predictions 
from climate models.'' Would you comment on these recent reports?
    Answer. The arguments in both papers are fundamentally circular as 
have been all attribution claims so far. What both papers show is that 
in response to rising surface temperatures of the past 50 years or so, 
there has been an increase in ocean heat content. Nothing controversial 
here. The emphasis of Levitus et al on the quantity of heat in the 
ocean is simply a statement that the heat capacity of the ocean is 
high; this is the reason for the ocean delay. Again no surprise. The 
claim that the observation confirms an anthropogenic cause is arrived 
at by looking at climate models which stimulate the observed surface 
temperature history by considering the joint effects of increasing C02 
and aerosols. The argument goes that if models can stimulate the 
surface temperature, and if observations show then deep ocean heat 
content responds to surface temperature, then deep ocean heat content 
is responding to anthropogenic forcing. However, the aerosol forcing 
(which is crucial to stimulations) is so uncertain that it constitutes 
in essence an adjustable parameter (or parameters)which can be adjusted 
to produce a fit. The arguments of Levitus et al and Barnett et al then 
boil down to a peculiar assertion that if one can adust models to fit 
observations, the models must be right. Not exactly normative science.
    That said, Barnett et al do mention some important things in 
passing. One was the role of the `regime change' in the 1970's. This 
may be the real origin of temperature increase over the past 30+ years. 
The radiosonde data shows a very sharp increase in tropospheric 
temperature around 1976, with the surface temperature catching up over 
the following ten years (ocean delay again). This may be the reason for 
discrepancy between the satellite MSU data and surface data: the 
satellite data begins in 1979, after the atmospheric temperature rise 
occurred. As Barnett et al mention, the models don't show the regime 
change, and, therefore, the temperature rise they produce by adjusting 
aerosol forcing is likely due to the wrong reason. A second, was the 
comment that the coupled model they used was rather insensitive to 
anthropogenic forcing. This is important for the following reason: for 
sensitive models, the ratio of surface temperature to radiative forcing 
at the surface is high (this is the meaning of sensitivity), and low 
radiative forcing will cause the ocean to take longer to accumulate a 
given amount of heat. Relatively rapid heating of the deep ocean 
generally implies low climate sensitivity. In a paper by myself and 
Giannitsis in the Journal of Geophysical Research about 3 years ago, we 
looked at the observed response to volcanic sequences in order to 
estimate climate sensitivity: the range 0.3-1 .2C for a doubling of 
CO2 appeared most likely (We are following the conventional 
practice of expressing sensitivity in terms of the response to doubling 
CO2). More recently, at the meeting of European Geophysical 
Society a couple of weeks ago, we did the same for the surface response 
to regime change--and with the same result. Barnett et al really can't 
do the same since they don't know the actual forcing.
    Which brings me to the final point: although both papers claim to 
have made an attribution (spuriously as far as I can tell), neither 
claims to have established any sensitivity, and it is the question of 
climate sensitivity that is crucial. Attribution without determining 
sensitivity is a fairly abstract exercise with no practical implication 
per se.
    Finally, it should be pointed out that when these two papers 
compared observations with model outputs, the agreement was not 
particularly good.
    Question 2. On the IPCC process, you have stated the vast majority 
of the participants played no role in preparing the summary, were not 
asked for agreement. Can you elaborate on this statement?
    Answer. The IPCC directorate chooses the coordinating lead authors 
for each chapter. There were 13 chapters in the Working Group I report. 
Then a team about 15-30 lead authors are assembled for each chapter, 
and finally another 40-50 contributing authors are chosen for each 
chapter. (The numbers are approximate) Each 2-5 pages has about 2-3 
lead authors responsible for their preparation with assistance from 
contributing authors. Only the lead authors, however, attend the 
meetings where their pages are prepared and reviewed. The meetings are 
held around the world. For Working Group I, the meetings were in Paris, 
Arusha in Tanzania, Auckland in New Zealand, and Victoria in British 
Columbia. Although each lead author may comment on the whole chapter, 
in practice, the lead authors generally concern themselves with the 
pages they are expert in. After the chapters are completed (in the case 
of Working Group I, this happened in August 2000), the coordinating 
lead authors prepare a draft of the Summary, which is then studied by 
the directorate as well as representatives from government, industry 
and NGOs who proceed to rewrite the summary. This was done in Shanghai 
in January 2001 for the Working Group I report. The resulting Summary 
for Policymakers is not subject to approval by any of the authors. 
Moreover, the directorate reserves the right to modify the chapters in 
order to make them consistent with the summary. This is done with the 
assistance of the coordinating lead authors. The text is not issued 
until months after the Policymakers Summary.
    Question 3. You have mentioned that the preparation of the report 
was subject to pressure. You said that you personally witness co-
authors being forced to use their green'' credentials in defense of 
their statements. Can you explain these ``green'' credentials?
    In the sections on water vapor of Chapter 7 (Physics of Climate), 
there were three lead authors (myself, Herve Letreut of France, and Ray 
Pierrehumbert from the University of Chicago). Although Letreut is a 
modeler and Pierrehumbert is a Sierra Club activist, and both wanted to 
stress that the models might be right with respect to the crucial water 
vapor feedback, we all agreed that the relevant physics should be 
briefly reviewed with errors from previous IPCC reports corrected, and 
that the potential problems be explained. When, the writeup failed to 
include the traditional bromides of the first and second assessments, 
the coordinating lead author, Thomas Stocker of Switzerland, who knew 
nothing about the water vapor feedback, insisted that the pages be 
rewritten to produce what was expected, and accused the three of us of 
being unduly influenced by my allegedly contrarian and suspect views. 
However, I had intentionally stayed out of the writing, and Herve and 
Ray were forced to explain that they were actively pro-environmental 
and supportive of global warming: they were only trying to tell the 
truth. The scene was truly pathetic, and was witnessed by others.
    Question 4. Background: Last year I introduced a bill, titled 
``International Climate Change Science Commission Act'', to established 
an International scientific commission to assess changes in global 
climate patterns and to conduct scientific studies and analysis for 
other nations. Given your experience with the IPCC, are you 
recommending that the US and other countries rely upon another 
scientific body such as the International commission that I proposed 
last year?
    Answer. I am not familiar with your bill. However, I am not sure 
how the US would go about creating an international commission. 
Certainly, it might be possible to create such a commission without a 
tie to any negotiations, and a permanence that would be independent of 
`crisis' and a charge that included understanding, monitoring, and 
eventual forecasting of climate change regardless of its cause.
    Question 5. You have stated that if we view Kyoto as an insurance 
policy, it is a policy where the premium appears to exceed the 
potential damages, and where the coverage extends to only a small 
fraction of the potential damages. In your opinion, what type of 
damages would not be covered?
    Answer. If one considers most warming scenarios, and carefully 
estimates the costs (viz Questions 2 from Sen. Kerry), they are at 
worst comparable to the estimated costs of Kyoto, while Kyoto will, at 
best, help us to avoid only a small fraction of the projected warming.
      Response to Written Questions Submitted by Hon. John Kerry 
                       to Dr. Richard S. Lindzen
    Question 1. You have stated repeatedly and with some certainty that 
a doubling of carbon dioxide in the atmosphere will produce a warming 
of 1 degree Celsius at most. The IPCC has expressed far greater 
uncertainty in its estimate of the warming impact of a doubling of 
atmospheric carbon dioxide, offering a range of 1.5 to 5.8 degrees 
Celsius. On what do you base your conclusion and why do you make that 
conclusion with such confidence that you don `t suggest a range of 
    Answer. In my written testimony, I mentioned that the response to 
double CO2 alone, without feedbacks from clouds and water 
vapor, would produce about 1C warming. This is what virtually everyone 
involved gets. I also mentioned that higher values resulted from 
positive water vapor and cloud feedbacks in the models which have never 
been confirmed in the observations. Indeed the wide range of model 
results (which for a doubling of CO2 remain in the range 
l.5-4C which is what was given in the 1979 Charney Report of the NRC) 
results largely from the erratic behavior of clouds in the models. The 
IPCC range is based on the range of results produced by current models 
plus uncertainties in emissions scenarios with the highest value based 
on a scenario which more than doubles CO2. In recent papers 
(including one in preparation), we have sought observational estimates 
of sensitivity and feedbacks, and have pretty much narrowed things to a 
range of 0.3 to 1.2C which represents (in percentage terms) as great an 
uncertainty as the IPCC model range of results. In a paper by myself 
and Constantine Giannitsis, we looked at the temporal response to 
volcanic eruptions which provides a direct measurement of sensitivity. 
In another paper by myself, Ming-Dah Chou, and Arthur Hou, we used data 
to estimate a negative cloud feedback completely absent from models 
which essentially cancels model positive feedback--even if the latter 
were correct, which seems unlikely.
    Question 2. You argue that warming observed in recent decades 
``represents what is on the whole a beneficial pattern.'' You have also 
suggested that future warming may have beneficial impacts on the whole. 
What specific imnpacts do you view as beneficial and what impacts do 
you view as harmful in drawing that conclusion? What nations will 
benefit the most from warming? What nations will benefit the least or 
be harmed by warming?
    Answer. With respect to my remark in the testimony, ``that warming 
is likely to be concentrated in winters and at night . This is an 
empirical result based on data from the past century. It represents 
what is on the whole a beneficial pattern,'' the answer is fairly 
obvious: longer growing seasons, less frost, fewer cold related deaths, 
lower heating bills, less likelihood of older citizens moving to the 
moving to the sun-belt. In addition, there are the benefits from 
CO2 fertilization: greater agricultural productivity with 
less need for water. The dangers are more speculative. Some endangered 
species may be stressed further, and some changes in preferred 
agricultural crops may be disadvantageous. Most scenarios of a 
catastrophic nature, refer to storminess, sea level rise, droughts, 
floods, etc., but these are even considered by the IPCC to be 
speculative since observational evidence is very weak, and in the case 
of extra tropical storminess, and variability, theory suggests the 
opposite (as noted in my written testimony). Finally, although I 
believe current models exaggerate the magnitude of warming. the 
coupling of these models to economic models with due concern for the 
detailed impact of climate change on specific sectors leads to a 
positive impact of GDP in most of the world. The figure is taken from a 
report by Prof. Robert Mendelsohri of Yale using Jim Hansen's model at 
the Goddard Institute for Space Studies. It shows most of the Northern 
Hemisphere benefitting, while parts of equatorial Africa and South Asia 
suffering reduced GDP.