[Senate Hearing 106-1115]
[From the U.S. Government Printing Office]
S. Hrg. 106-1115
THE SCIENCE BEHIND GLOBAL WARMING
COMMITTEE ON COMMERCE,
SCIENCE, AND TRANSPORTATION
UNITED STATES SENATE
ONE HUNDRED SIXTH CONGRESS
MAY 17, 2000
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SENATE COMMITTEE ON COMMERCE, SCIENCE, AND TRANSPORTATION
ONE HUNDRED SIXTH CONGRESS
JOHN McCAIN, Arizona, Chairman
TED STEVENS, Alaska ERNEST F. HOLLINGS, South Carolina
CONRAD BURNS, Montana DANIEL K. INOUYE, Hawaii
SLADE GORTON, Washington JOHN D. ROCKEFELLER IV, West
TRENT LOTT, Mississippi Virginia
KAY BAILEY HUTCHISON, Texas JOHN F. KERRY, Massachusetts
OLYMPIA J. SNOWE, Maine JOHN B. BREAUX, Louisiana
JOHN ASHCROFT, Missouri RICHARD H. BRYAN, Nevada
BILL FRIST, Tennessee BYRON L. DORGAN, North Dakota
SPENCER ABRAHAM, Michigan RON WYDEN, Oregon
SAM BROWNBACK, Kansas MAX CLELAND, Georgia
Mark Buse, Republican Staff Director
Martha P. Allbright, Republican General Counsel
Kevin D. Kayes, Democratic Staff Director
Moses Boyd, Democratic Chief Counsel
C O N T E N T S
Hearing held on May 17, 2000..................................... 1
Statement of Senator Brownback................................... 25
Prepared statement........................................... 28
Prepared statement of Senator Hollings........................... 3
Statement of Senator Kerry....................................... 20
Statement of Senator McCain...................................... 1
Prepared statement of Senator Snowe.............................. 4
Bradley, Dr. Ray, Department Chair, Department of Geosciences,
University of Massachusetts.................................... 29
Prepared statement........................................... 32
Christy, Dr. John R., Director, Earth System Science Center,
University of Alabama.......................................... 36
Prepared statement........................................... 38
Lane, Dr. Neal, Assistant to the President for Science and
Technology, Office of Science and Technology Policy............ 4
Prepared statement........................................... 7
Mahlman, Dr. Jerry, Director, Geophysical Fluid Dynamics
Laboratory, National Oceanic and Atmospheric Administration.... 42
Prepared statement........................................... 45
Trenberth, Dr. Kevin E., Director, Climate Analysis Section,
National Center for Atmospheric Research....................... 47
Prepared statement........................................... 49
Watson, Dr. Robert, Chairman, Intergovernmental Panel on Climate
Prepared statement........................................... 56
Response to written questions submitted by Hon. John McCain to:
Dr. John R. Christy.......................................... 88
Dr. Neal Lane................................................ 89
Dr. Jerry Mahlman............................................ 92
Dr. Kevin E. Trenberth....................................... 95
Dr. Robert Watson............................................ 98
Mahlman, Dr. Jerry, Director, Geophysical Fluid Dynamics
Laboratory, National Oceanic and Atmospheric Administration,
Science Magazine Article....................................... 85
THE SCIENCE BEHIND GLOBAL WARMING
WEDNESDAY, MAY 17, 2000
Committee on Commerce, Science, and Transportation,
The Committee met, pursuant to notice, at 9:31 a.m., in
room SR-253, Russell Senate Office Building, Hon. John McCain,
Chairman of the Committee, presiding.
OPENING STATEMENT OF HON. JOHN McCAIN,
U.S. SENATOR FROM ARIZONA
The Chairman. Good morning. We meet today to examine the
issues surrounding global warming. This subject continues to be
an issue of great importance to the environment and the
economic future of the country.
To better prepare ourselves to objectively evaluate future
legislative policy, the Committee will explore three issues:
One, the underlying science behind global warming; two, exactly
where we are in our research efforts; and, three, what does it
For many years, scientists have been warning us about the
greenhouse effect caused by man-made emissions of carbon
dioxide and other gases, and the far reaching environmental
consequences which could result if the problem is not properly
A large amount of evidence has been presented to suggest
that this phenomena is real and is due to the activity of man.
However, there also has been evidence presented to contradict
Earlier this year, the National Research Council concluded
that the warming trend during the past 20 years is real, and is
substantially greater than the average temperature of warming
during the 20th Century. The report also identified a
substantial disparity between satellite data trends and surface
temperature trends as well.
The Intergovernmental Panel on Climate Change also has
issued a draft of its third assessment report which will, in
all likelihood, suggests a warming trend when its final version
is released early next year. These two reports, in addition to
hundreds of other studies, outline the need for a more firm
understanding of and scientific consensus on global warming.
I would like to offer one brief example of global warming's
potential harm. According to the United Nations Environment
Program, the global average sea level has risen by 10 to 25
centimeters over the past 100 years. It is likely that much of
the rise is related to an increase in the lower atmosphere's
global average temperature since 1860.
Scientific models further project a rise in sea levels of a
foot and a half by the year 2100. This projected rise is two to
five times faster than the rise experienced over the past
century. The impact of such movement on our coastal communities
and businesses, such as fisheries, agriculture, and tourism, is
unknown, but the consequences could be serious considering that
half of the U.S. population lives in the coastal communities.
We look forward to hearing more about the outlined reports
and potential scenarios from our witnesses today, along with
the new findings from the government's research efforts.
Most importantly, any actions the United States takes in
response to claims of global warming must be based on the best
science available and not on rhetoric or political expedience.
We must continue to invest in our research capabilities to
fully understand the scientific interactions between humans,
the land, the ocean, and the atmosphere.
Testimony presented here today will serve as a valuable
insight for this Committee. We hope to establish a baseline for
the Committee on the current state of knowledge on the subject
of global warming. And I welcome all of our witnesses who are
Before I ask Dr. Neal Lane, who is the Assistant to the
President for Science and Technology of the Office of Science
and Technology Policy, to begin his statement, I would like to
make one additional comment.
One of the great things about the requirements of the
electoral process is extensive interaction with the citizenry.
I just finished an unsuccessful, but very enlightening,
adventure in that area.
In town hall meeting after town hall meeting after town
hall meeting, of which I had hundreds, young Americans stood up
and said, ``Senator McCain, what is your position on global
warming?'' There is a group of Americans who now come to
political rallies with signs that say, ``What is your plan?''
``What is your plan,'' is the question that is asked.
I do not have a plan. I am sorry to say that I do not have
a plan because I do not have, nor do the American people have,
sufficient information and knowledge. But I do believe that
Americans and we who are policymakers in all branches of
government, should be concerned about mounting evidence that
indicates that something is happening.
I do not pretend to have the expertise and knowledge on
this very important and very controversial issue, but I do
intend, beginning with this hearing and follow-on hearings, to
become informed, to reach some conclusions, and make some
recommendations, or make some non-recommendations depending on
the information that I receive.
I believe that it is of the utmost importance that we
examine this issue thoroughly, and I am dedicated to that
proposition. And I am very grateful that we have such a very
well informed group of Americans who will appear before us
[The prepared statement of Senator Hollings follows:]
Prepared Statement of Hon. Ernest F. Hollings,
U.S. Senator from South Carolina
Mr. Chairman, thank you for holding this hearing today on global
climate change, which I hope will be only one of many. It's been about
3 years since our last full Committee hearing on climate change, so I
welcome this opportunity to hear what the science can now tell us about
this important topic. This Committee has worked hard to ensure that the
federal government has the best research and information possible about
global warming, as well as other types of climate changes. I'm glad to
see our investments are bearing fruit and that we are identifying ways
to focus our research to help us make decisions now and in the decades
During the 1980s, a number of us here on the Committee became
increasingly concerned about the potential threat of global warming and
loss of the ozone layer. In 1989, I sponsored the National Global
Change Research Act, which attracted support from many Members still
serving on this Committee including Chairman McCain, as well as
Senators Stevens, Inouye, and Gorton. In 1990, after numerous hearings
and roundtable discussions, Congress enacted the legislation, thereby
creating the U.S. Global Climate Research Program.
When we passed the Global Change Research Act, we knew it was the
first step in investigating a very complex problem. We placed a lot of
responsibility in NOAA, the scientific agency best suited to monitor
and predict ocean and atmospheric processes. We need to renew this
ocean research commitment to ensure we better understand the oceans,
the engines of climate. The so-called ``wild card'' of the climate
system, the oceans, are capable of dramatic climate surprises we should
strive to comprehend. In addition, the oceans are critical to our
continued well-being. I am particularly interested that we pursue the
questions covered by the recent NRC report, From Monsoons to Microbes:
Understanding the Ocean's Role in Human Health. This excellent report
tells everyone here--even those who don't live on the coast--that
understanding our oceans is of the utmost national importance. The
Oceans Act this Committee approved only a few weeks ago would go a long
way to ensuring that we give priority to these important ocean research
I am glad to report that the research accomplished under the
National Global Change Research Act has led to increased understanding
of global climate changes, as well as regional climate phenomena like
El Nino/Southern Oscillation (ENSO). We now have a better understanding
of how the Earth's oceans, atmosphere, and land surface function
together as a dynamic system, but we cannot stop there. Only recently,
NOAA measured an important increase in temperature in all the world's
oceans over a 40 year period. We need to understand the causes and how
that will affect us. All this research ensures that federal and state
decisionmakers get better information and tools to cope with such
climate related problems as food supply, energy allocation, and water
While we have learned an astonishing amount about climate and other
earth/ocean interactions in only a decade, we have other critical
questions that require further research to answer. Many of these
questions are relevant not only to improving our scientific
understanding, but also to contributing to our future social and
economic well-being. For example, climate anomalies during the past two
years--most directly related to the 1997-1998 El Nino event--have
accounted for over $30 billion in impacts worldwide. When impacts from
the recent floods in China are included, these direct losses could rise
to $60 billion. This most recent El Nino claimed 21,000 lives,
displaced 4.5 million people, and affected 82 million acres of land
through severe flood, drought, and fire. When we better understand the
global climate system, and its relationship to regional climate events
like El Nino, we may be able to find ways--such as improved forecasting
and early warning--to avoid some of the severe impacts.
Under current global warming scenarios, scientists predict a 6 to
37 inch rise in sea level by the year 2100 that will put our coastal
areas at an increased risk of flooding. This could have severe
consequences for coastal states, such as mine, particularly if climate
change has any bearing on the frequency or severity of hurricanes.
While we have been in a pattern of infrequent hurricane landfalls along
the East Coast, it is possible that recent severe storms signal a
return to conditions similar to those of the 1930s, 1940s, and 1950s
when huge storms were frequently making landfall. If so, and
particularly if global warming increases our vulnerability to flooding,
we must develop the science to better understand and respond to any
environmental changes in weather patterns.
I welcome our witnesses to discuss the current state of science on
global climate change. I am anxious to hear about the progress we've
made towards better understanding the complex temperature and
precipitation pattern changes, and where our research efforts are going
in the upcoming decade. I hope today's hearing will reinvigorate this
Committee's leadership in promoting sound research on these important
[The prepared statement of Senator Snowe follows:]
Prepared Statement of Hon. Olympia J. Snowe, U.S. Senator from Maine
Thank you, Mr. Chairman, for holding this timely hearing so that we
can further understand the underlying science behind global climate
variability from a distinguished group of internationally renowned
Mr. Chairman, last spring, Maine had a first-of-its-kind conference
specifically to debate and discuss the impact of potential
environmental climate change with state, national and international
experts. For two days, over 150 people explored many questions. Are we
leaving a human fingerprint on the Earth's climate? Why has the average
temperature in Lewiston--where the conference was held--increased 3.4
degrees F. over the last century? Are we in a race against an
uncertainty that none of us on this planet can afford to lose? And, if
so, what do we need to do to establish a sound scientific basis for
making state, regional, national, and international resource management
and economic and policy decisions when considering global environmental
change issues? The answers to these questions are complex, and our
approach to them must continue to be through research and thorough
analysis of the research results.
It is important to continue to develop more accurate models led by
common scientific research and thought so we might better predict what
the impacts will be on plants and animals--including ourselves--under
any changing climatic conditions. Concurrently, we must also evaluate
the mitigation and adaptation strategies under consideration by policy
makers in response to increasing amounts of atmospheric carbon dioxide
and other greenhouse gases and possible environmental changes.
The U.S. Forest Service has predicted that climate and pollution
stresses from wild pests, humans, and other environmental changes are
likely to cause unprecedented cumulative effects on our northern forest
ecosystems and, by extension, on our economy and our culture. Our
forests can largely adapt to environmental changes. But, over time,
these forests could very well change in their composition, range,
health, and productivity. Oak and conifers, for instance, could prevail
over the maple dominated hardwood forests--diminishing the brilliant
fall foliage for which New England is so famous.
The fact is, the vast majority of international scientists say that
something appears to be happening because of the excess of greenhouse
gases in the atmosphere, and there is general agreement that human
activities are affecting the global climate and thus affecting both
land and sea.
As Chair of the Oceans and Fisheries Subcommittee, I have
introduced the Coral Reef Conservation Act, along with you, Mr.
Chairman, in an effort to protect, sustain, and restore the health of
coral reef ecosystems. In 1998, coral reefs around the world appeared
to have suffered the most extensive and severe bleaching damage and
subsequent mortality in modern times. Reefs in at least 60 countries
were affected, and in some areas, more than 70 percent of the corals
died off. These impacts have been attributed to, among other factors,
the warmest ocean temperatures in 600 years. We must increase our
efforts to protect these coral reefs, which are among the world's most
biologically diverse and productive ecosystems.
Again, Mr. Chairman, I thank you for holding this hearing on the
science of global warming, and thank you for assembling such a
distinguished panel today to share their vast expertise with us.
The Chairman. Dr. Lane, thank you and welcome, and thank
you for all the outstanding work you have done in the past and
are presently doing.
STATEMENT OF DR. NEAL LANE, ASSISTANT TO THE PRESIDENT FOR
SCIENCE AND TECHNOLOGY, OFFICE OF SCIENCE AND TECHNOLOGY POLICY
Dr. Lane. Thank you very much, Mr. Chairman.
And I want to thank you, Senator Hollings, members of the
Committee, for holding this hearing, and for giving me and also
my colleagues, who are the experts in this matter, a chance to
talk to you today about the state of knowledge of climate
change, and about our Federal agency research program.
The U.S. Global Change Research Program continues a strong
bi-partisan tradition of support for this scientific endeavor.
And it began with President Reagan, continued through President
Bush's Administration, and on to the Clinton/Gore
I would ask that my written testimony be included for the
The Chairman. Without objection, the entire statement of
you and the other witnesses will be included in the record.
Dr. Lane. Thank you. I will summarize three issues in my
oral statement very briefly: First, what we know about the
Earth's climate and how it is changing; second, the remaining
difficult scientific questions that we must address; and
finally, how our research program is going after these issues.
Let me start with the area of scientific consensus. First,
human activities has significantly increased atmospheric carbon
dioxide. In the past century, atmospheric CO2 has
risen 30 percent. The concentration of carbon dioxide is now
higher than at any time over the past 420,000 years.
Second, the surface of the Earth is warming. The Earth's
surface has warmed significantly over the last century. The
oceans are warming as well, and evidence is strong that the
temperatures of the late 20th Century are without precedent in
the last several centuries, the 1990's are the warmest decade
on record, and 1998 was the warmest year in 1,000 years.
Third, the Earth's global average surface temperature will
continue to rise during the next century. Greenhouse gases in
the atmosphere will increase the surface temperature of the
Earth. Global temperatures are projected to increase two to six
and a half degrees Fahrenheit over the next 100 years.
Rising temperatures will increase rates of evaporation and
lead to more total precipitation. Sea level will rise as
warming expands the ocean water. Finally, these changes in
temperature, precipitation, and sea level will affect the
natural environment and human society.
The ideal ranges for plants and animals will change, and in
some cases the effects of other environmental stresses and
urban and rural areas will be amplified.
Let me now move to the areas of remaining uncertainty. The
key questions I think are: How fast will temperatures change
over the next century, and how will the impacts of this change
vary across different regions of the world?
Differences in future climate projections largely stem from
disagreements over so-called feedback effects. For example,
will more water in the atmosphere increase warming by acting as
a greenhouse gas, or result in more low clouds that will
reflect sunlight away from the Earth? Will aerosols, small
particles, reflect incoming sunlight, or will they absorb heat
and contribute to warming effects?
We do not know the exact answers to these questions, but
our estimates of future average temperature increases in the
range of two to six and a half degrees Fahrenheit include all
of these uncertainties.
We know the amount of carbon dioxide the global biosphere
takes up and releases each year varies widely, but we do not
know why. And although evidence suggests that plants and
vegetation in the northern hemisphere are currently taking up
substantial amounts of carbon dioxide, we do not know whether
this capacity can be maintained or even increased over the long
And though we often discuss global climate change, many
important policy questions will have a regional focus. For
instance, how will climate change affect rainfall in the
southwest, fisheries in the northwest, or the distribution of
maple trees in the northeast? We need to know how these changes
will affect agriculture, tourism, and local economies.
Finally, Mr. Chairman, I would like to comment on our
efforts to answer these questions. Federal agencies that
participate in the U.S. Global Change Research Program conduct
research on the mechanisms of the Earth's climate system, on
the future course of climate change, and the potential impacts
of climate change on the environment and human society.
The research agenda for the Global Change Research Program
has been developed in cooperation with the scientific
community, including the National Academy of Sciences.
Over the last decade, the Global Change Research Program
has had a strong focus on the physics and chemistry of the
atmosphere and the oceans, including reducing uncertainties
about the rule of aerosols and water in the atmosphere.
Recently, the Global Change Research Program has broadened
its scope, and I would like to highlight three new priorities.
First, we are completing the first U.S. national assessment of
the potential consequences of climate variability and change.
This assessment is examining the potential ecological and
socioeconomic impacts of climate variation and change in the
United States and the ways we might prepare for them.
Second, our new carbon cycle science initiative will
evaluate the potential for the Earth's forests, the agriculture
regions, and wetlands, to take up and store carbon.
And finally, new research under the Global Change Research
Program umbrella will focus on how water moves through the
land, the atmosphere, and the ocean, and how climate change may
increase or decrease regional availability of this critical
Mr. Chairman, I thank you again for the opportunity to
testify today. Your sponsorship of the Global Change Research
Seminar Series clearly shows your interest in climate science.
And I am confident that together we can continue to increase
our understanding of these important issues that will help us
make sound policy decisions for our nation.
I will be happy to answer any questions you have.
The Chairman. I thank you, Dr. Lane, and I did read your
entire statement which I think is very illuminating.
[The prepared statement of Dr. Lane follows:]
Prepared Statement of Dr. Neal Lane, Assistant to the President for
Science and Technology, Office of Science and Technology Policy
Thank you for this opportunity to discuss with you the
Administration's science and technology programs that are relevant to
the understanding of climate change. I know the Members of this
Committee share my strong belief that America's world-leading science
and technology enterprise must be sustained and nurtured. While we
sometimes differ on precisely how and where to invest our taxpayers'
funds, we share a bipartisan understanding that the future prosperity
of this country depends on continued strong federal support for all
areas of scientific inquiry.
Today I come before you to suggest that we can bring that same
common appreciation for science to an area of considerable policy
disagreement--the issue of climate change. Whatever your policy views
may be on the wisdom of the Kyoto Protocol, I respectfully suggest that
supporting scientific research on climate change and its potential
impacts is in our national interest. The President's FY2001 budget
requests substantial funding for the U.S. Global Change Research
Program, as has every budget submitted by this Administration and those
of President Reagan and President Bush. I hope that Congress sees fit
to continue the bipartisan tradition of strong support for this
scientific endeavor, which is providing the sound, objective
information we need to support decision-making in the public and
The Science of Climate Change
I would now like to summarize what we know about the Earth's
climate and how it is changing. In 1995, the Second Assessment Report
of the Intergovernmental Panel on Climate Change (IPCC) reviewed all of
the science then available. Through the IPCC process, leading
scientists from more than 150 countries periodically review and assess
scientific information about climate change and its environmental and
economic effects. The report documented a series of changes that had
already occurred, including increases in greenhouse gas concentrations,
an unusually rapid increase in temperatures, and rising sea levels. It
explained that the magnitude, timing, and geographic pattern of
observed temperature changes closely matches the changes that models
project from human activities, and does not match well with model
simulations of natural change or changes seen in the natural record.
The Report famously concluded: ``The balance of evidence suggests that
there is a discernible human influence on global climate.''
The qualified nature of the IPCC attribution statement reflected
the existence of alternative interpretations of parts of the data and
known shortcomings in models of how the climate system works.
Recently, however, important scientific evidence has emerged that
has substantially undercut many of potential dissenting arguments,
thereby fundamentally changing the debate over global warming.
Basically, the debate has changed from ``Are we warming the Earth?'' to
``How much are we warming the Earth?'' To understand the current state
of climate change science, let me first start with a series of
statements that virtually all credible atmospheric scientists agree
1. The atmospheric concentration of CO2 has been
significantly increased by human activities. In the past century or so
the CO2 concentration has risen from less than 280 parts per
million by volume (ppmv) to about 365 ppmv, an increase of about 30
percent. At 365 ppmv, CO2 is now higher than at any time
over the past 420,000 years. It is universally recognized that human
activity is responsible for this increase, mainly through fossil fuel
combustion and deforestation. Our best estimates show that unless
action is taken to reduce CO2 emissions, atmospheric carbon
dioxide levels will likely reach about 700 ppmv by the end of the 21st
century, about double current levels. Other greenhouse gases, such as
nitrous oxide, methane, and halocarbons (CFCs and HFCs), have also
increased due to human activities and further increases over the 21st
century will add to the tendency for global warming.
2. The surface of the Earth is warming. There is now near unanimous
agreement, including most of the climate skeptics, that the Earth's
surface has warmed significantly over the last century.
A recent National Research Council report (``Reconciling
Observations of Global Temperature Change'') carefully examined
direct measurements of surface temperature. The report
concluded that ``The warming trend in global-mean surface
temperature observations during the past 20 years is
undoubtedly real and is substantially greater than the average
rate of warming during the twentieth century.'' These data show
that the surface of the Earth has warmed by 0.4-0.7 degrees C
(0.7-1.4 degrees F) over the last 100 years, with 0.2-0.4
degrees C (0.4-0.8 degrees F) of that coming in just the last
Borehole measurements of temperature at various depths below
the Earth's surface show that the average surface temperature
of the late 20th century is without precedent in the last 500
Using tree rings, lake sediment records, ice cores, and
other paleoclimate indicators, a global temperature record
extending back 1000 years has been constructed. This record is
in broad agreement with the other data sets, and it shows that
the 1990s were the Earth's warmest decade in the last 1000
years, and that 1998 was the warmest year in this entire
Measurements made over the last few decades have shown a
precipitous decrease in both the areal extent and thickness of
Arctic Sea ice. Model simulations of the data suggest that this
decline is unlikely to be an entirely natural phenomenon.
Mountain glaciers have retreated worldwide during the last
Over the last century, global mean sea level has risen 4 to
8 inches, and further rise is inevitable because of the thermal
inertia of the ocean and melting glaciers.
During the past 45 years the upper 300 meters of world Ocean
has warmed by approximately 0.56 degrees F. This warming is
consistent with predictions from general circulation models
that simulate the effect of greenhouse gas increases since the
beginning of the industrial revolution.
3. The Earth's surface temperature will continue to rise during the
next century. Elementary physics shows that increasing greenhouse gases
in the atmosphere must exert a strong warming tendency on the surface
temperature of the Earth. This is not a controversial concept. Indeed,
the greenhouse effect is responsible for providing a hospitable climate
on Earth. It is generally agreed that the Earth's surface temperature
will rise over the next century as the atmospheric concentrations of
CO2 and other greenhouse gases increase. The questions are:
``How much and how fast will temperature increase, and with what
regional impact?'' The 1995 IPCC Second Assessment Report, representing
the broad consensus of the scientific community, projected a
temperature increase of 1.0 to 3.5 degrees C (2 to 6.5 degrees F) over
the next 100 years. The more sophisticated analyses conducted since
that time, which will form the basis of the IPCC Third Assessment
Report, due out in early 2001, continue to show that such an increase
is likely. This rate of warming would be greater than any seen during
the past 10,000 years.
4. There is mounting scientific evidence that climate change is
already affecting ecosystems. Data from many sites in Europe and North
America show that the observed warming has been accompanied by earlier
plant growth and flowering. For example, here in Washington, D.C.,
cherry trees, along with 89 of 99 other plants examined, are blooming a
week or more earlier than they did 30 years ago. Satellite data for
high latitudes in the Northern Hemisphere show that plants are leafing
eight days earlier in 1991 than in 1982. Observed changes are not
confined to vegetation:
The ranges of some animals appear to be shifting. Birds are
going further north to breed and the range of many European and
North American butterflies are shifting north as well.
Some species are disappearing when a habitat changes. Warmer
and drier conditions have caused the high elevation ``cloud
forest'' of Costa Rica to rise and 20 frog species to
Observations in several sites along the Pacific coast of
North America indicate that the distribution of fish and
phytoplankton has changed as waters warm. There is also
evidence that warming waters increase the amount of coral
We have discovered much about the way the climate system works, and
about how the climate system is likely to evolve in response to
increases in greenhouse gases. As I noted above, the debate has changed
from ``Are we warming the Earth?'' to ``How much are we warming the
Earth?'' It leads directly to the question of ``So what?'' Right now,
science only provides a partial answer. As temperatures rise
evaporation will increase, leading to more moisture in the atmosphere.
Hence, worldwide, an increase in total rainfall is likely, with much
coming in heavier downpours. But increased evaporation will also lead
to more drought in some regions. Rising temperatures will also bring
sea-level rise. These changes in temperature, precipitation and sea
level will likely change the ideal ranges for plant and animals, and
will also affect human society. Our understanding of how the life
support systems on Earth will respond to these changes remains quite
uncertain. This uncertainty is no reason to be complacent about the
Let me now move past points of agreement, and talk about the
cutting edge of climate science.
To a large extent, the disagreements between future estimates of
the climate are disagreements about effects of the ``feedbacks'' of the
climate system. While increasing CO2 will, by itself, tend
to increase the surface temperature of the Earth, it will also change
other parameters, such as the amount of water vapor or the extent of
clouds, which also affect the climate system. For example, if the
climate warms due to increased CO2, then this will evaporate
more water vapor into the atmosphere. Water vapor is a powerful
greenhouse gas, so this will amplify the warming. This is an example of
a positive feedback. On the other hand, the increase in CO2
might also increase low clouds. These clouds reflect sunlight, so if
they increase it would cool the Earth, moderating somewhat the warming
effects of the CO2 increase. These feedbacks are only
roughly understood, and improving our understanding of them would
significantly improve our ability to predict the future climate.
Changes in the amount of solar radiation would definitely affect
the climate, and there are indications that changes in solar radiation
may have been an important contributor to climate change over the past
few centuries. However, changes in output of the sun cannot, by
themselves, entirely explain the observed warming over the last
century. Our best estimates are that changes in solar output could
explain about 25 percent of the surface temperature increase observed
in the last 100 years. The rapidly increasing concentrations of
greenhouse gases also mean that solar variability will be an ever-
smaller component of climate change in the future.
There are also important questions about the relationship of
temperature change to other changes in the physical climate system. One
of the expected consequences of warming is acceleration of the Earth's
hydrological cycle. The increased evaporation of water described above
will transfer water more rapidly from the land and oceans to the
atmosphere, and could result in an increased incidence of both droughts
and the extreme rainfall events that lead to flooding. There is already
evidence that such change has begun in the U.S., where the incidence of
heavy downpours (where more than 2 inches of rain falls in a 24-hour
period) has increased by about 10% over the last century. We know that
there will be significant regional variation in these changes, but our
ability to project regional-scale precipitation change is very limited,
and we do not have a good understanding of how precipitation change
will interact with other stresses on managed and natural ecosystems.
We also need to quantify the relative contributions of the oceans
and terrestrial plants to removing carbon from the atmosphere. Human
activities add about 7 billion tons of carbon to the atmosphere every
year. About 3 billion tons remain in the atmosphere, while 4 billion
are absorbed by terrestrial and ocean ``sinks.'' We know that land
ecosystems play an important role in carbon sequestration, but
important questions remain about the magnitude and geographic
distribution of terrestrial sinks. For example, there is consensus that
more carbon is being taken up than is released by land ecosystems in
the Northern Hemisphere, but we don't know if the amount is on the
order of tens of millions or hundreds of millions of tons. And where in
the Northern Hemisphere is carbon is being sequestered? It could be
mostly in North America, or it might be in Siberia.
More importantly, we don't know whether it is the above ground
vegetation or the soils that are responsible for the apparent increase
in sequestration. We also don't know what is causing this and whether
it will persist. Is it from nitrogen fertilization, an effect that will
disappear when soils become nitrogen-saturated, or as industrial and
automobile pollution is decreased? Is it from carbon fertilization, an
effect that could slowly decline with increasing atmospheric
concentrations? Is it from plants growing on abandoned farmland, or
from increased use of ``low-till'' agricultural practices? Is it from
growth of many young forests created recently under revised logging
laws, an effect that will decline as the forests mature? Or is it
simply from forest trees growing better in warmer, moister conditions,
an effect that may continue indefinitely? Finally, we know that the
amount of carbon the global biosphere stores and releases each year can
vary widely. However, we don't know how much of that sequestered
CO2 in the terrestrial biosphere is transitory, being
returned to the atmosphere in a year or two to continue contributing to
atmospheric CO2 increases. We also don't know how much
carbon is retained in soils for the decades or centuries required to
ameliorate atmospheric increases. Different answers to these questions
will determine very different trajectories of future atmospheric
We also know that local plant and animal species are being mixed
into ecosystems all over the world at increasing rates. Climate change
may exacerbate this problem. We also know that when these exotic
species spread aggressively, they can reduce and displace current
species, disrupt ecosystem functioning, and do enormous economic
damage. The National Academy of Sciences estimates that pubic and
private-sector spending on Zebra Mussel control, a problem we did not
even anticipate in the 1980s, will total $5 billion in 2000. Given that
expected rates of change over the next century will alter the ideal
ranges of plant and animal species faster than they can migrate,
ecosystem disruption is likely.
New Directions in the U.S. Global Change Research Program (USGCRP)
One of the consequences of increased understanding is the
definition of new research questions. The process of revising and
updating research strategies in response to new findings and new
questions goes on every year. It is a regular part of managing large
research programs, and the USGCRP is no exception. But periodically, it
is also valuable to step back and take a longer-term view of what has
been accomplished and what new research challenges are arising. One of
the most important contributions of the National Research Council to
the USGCRP is precisely this kind of taking stock. In 1996, the USGCRP
requested the NRC to undertake a major study of emerging issues in
global change science. The result was Global Environmental Change:
Research Pathways for the Next Decade, which consists of a summary
issued in mid 1998 and a full report published in 1999. The
``Pathways'' report identified a comprehensive set of science
questions, and identified several cross-cutting areas of special
concern, including carbon cycle science, water cycle science, and
climate change research ``on temporal and spatial scales relevant to
human activities.'' These recommendations played an important part in
the definition and initiation of a series of new activities in the
USGCRP: the Carbon Cycle Science Initiative, an increased emphasis on
water cycle research, and the initiation of the first National
Assessment of the Potential Consequences of Climate Variability and
Change for the US.
The USGCRP Carbon Cycle Science Initiative was established in the
FY2000 budget. The focus of this activity is on improving our
understanding of how carbon moves through the Earth's terrestrial
ecosystems, soils, ocean, and atmosphere, with $229 million proposed in
the FY2001 budget (a $25 million increase over FY2000). This on-going
effort will provide critical scientific information on the fate of
carbon in the environment, the sources and sinks of carbon on
continental and regional scales, and how sinks might change naturally
over time or be modified by agricultural or forestry practices. USDA,
DOE, DOI/USGS, NASA, NSF, DOC/NOAA, and the Smithsonian Institution
will all play important roles in this effort, guided by a science plan
that has been drafted with participation by many of the leading
scientists in this field.
The Carbon Cycle Science Initiative will employ a wide variety of
research activities in a comprehensive examination of the carbon cycle
as an integrated system, with an initial emphasis on North America.
Comparison of North America to other regions will also be important for
understanding the relative importance of our region in the global
context. Atmospheric and oceanographic field sampling campaigns over
the continent and adjacent ocean basins will be combined with
atmospheric transport models to develop more robust estimates of the
continental distribution and subcontinental-scale magnitude of North
American carbon sinks. Local-scale experiments conducted in various
regions will begin to identify the mechanisms involved in the operation
of carbon sinks on land and in the ocean; the quantities of carbon
assimilated by ecosystems, and how quantities might change to be
enhanced in the future.
The initiative will also include evaluation of information from
past and current land-use changes, both from remotely sensed and
historical records, to assess how human activity has affected carbon
storage on land. Potential management strategies for maximizing carbon
storage will be studied, including evaluation of the variability,
sustainability, lifetime, and related uncertainties of different
managed sequestration approaches. Finally, enhanced long-term
monitoring of the atmosphere, ocean, forests, agricultural lands, and
range lands, using improved inventory techniques and new remote
sensing, will be used to determine long-term changes in carbon stocks.
Integration of new observations and understanding of carbon cycle
processes in regional and global carbon system models will enable us to
more accurately project future atmospheric concentrations of carbon
dioxide and other greenhouse gases.
The highest priority for FY2001 will continue to be on
understanding and quantifying North American carbon sources and sinks,
and on filling critical gaps in our understanding of the causes of
carbon sinks on land as well as processes controlling the uptake and
storage of carbon in the ocean. Research advances on these questions
will provide information needed as a basis for sound policymaking, as
well as valuable information about potential management strategies to
land and forest managers in both the public and private sectors.
Research on the Global Water Cycle is receiving increased attention
in the USGCRP, with $308 million proposed in the FY2001 budget (a $35
million increase over FY2000). This has been an important research area
since the inception of the USGCRP, but the increasing evidence that
changes in the water cycle are already occurring, and that changes in
the water cycle and climate are closely coupled, are leading to a new
emphasis on water cycle science. The USGCRP has established a Water
Cycle Study Panel that is focused on improving our understanding of how
water moves through the land, atmosphere, and ocean, and how global
change may increase or decrease regional water availability. This
group, which includes government and academic scientists, is developing
comprehensive research and applications strategies that will take
advantage of existing and future observing systems to address the major
issues concerning the global water cycle and global and national water
The primary goal is to achieve a greater understanding of the
seasonal, annual, and interannual mean state and variability of water
and energy cycles at continental-to-global scales, and thus a greater
understanding of the hydrological interactions in the Earth's climate
system. The study of the global water cycle is a unifying theme that
bridges the gap between the spatial scales involved in global
atmospheric (and atmosphere-ocean interaction) processes, and land
surface hydrological processes, which determine the availability of
Finally, the U.S. National Assessment of the Potential Consequences
of Climate Variability and Change is now nearing completion. The
National Assessment effort, which began in 1997, is examining the
degree to which particular regions and sectors of the U.S. are
vulnerable to climate variations and change. The National Assessment is
examining the potential ecological and socioeconomic impacts of climate
variations and change, and ways we might prepare for both the next few
decades and the next century, including identification of possible
adaptation measures. It is also identifying key information gaps and
research needs (i.e., information that is still required to answer
questions of interest to resource managers and decision-makers).
The assessment effort has included a series of regional workshops
with participation from a broad range of public and private
stakeholders in the identification of issues of interest and a series
of regional and sectoral analyses, most of which are not yet complete.
The major product of the assessment process is a National Assessment
Synthesis Report that should be completed this year. The National
Assessment Synthesis Report is undergoing a rigorous peer-review that
includes several rounds of technical review, full agency review, and a
60-day public comment period before it is submitted to the President
and the Congress. The U.S. Global Change Research Act calls for this
type of assessment of the potential consequences of global changes on a
The first National Assessment will soon be completed, but we expect
many of the lessons learned during this process to play a significant
role in the definition of future USGCRP research activities. There were
important issues that it was not possible to fully address in this
initial effort, such as the potential indirect effects on the U.S. of
changes in other parts of the world. Many additional questions of
interest have been identified. Farmers and ranchers are curious about
what might change for their competitors in other nations. People all
around the country are interested in how climate change might alter the
incidence of extreme climate conditions that affect the quality of life
and livelihoods, such as drought, heat waves, and severe storms.
This first assessment is part of a larger evolution of the USGCRP.
During much of the first decade of its existence, the program
concentrated on observing and documenting change in the Earth's
physical systems and understanding why these changes are occurring. It
is now appropriately shifting from this predominant focus on physical
systems to a much broader effort to understand how global change will
affect the Earth's biological systems and the human societies that are
dependent upon them, and make useful scientific data and information
more broadly available for public and private planning and decision
To accomplish this, we must greatly improve our capabilities for
conducting regional-scale assessment of global change and its potential
consequences around the country. Our current level of understanding
tells us that climate change and its effects will vary by region, but
our ability to project specific regional effects remains limited. We
also need to learn more about the interactions of natural and human-
induced climate change and variability and other human-induced stresses
on the environment, such as pollution, land-use change, resource
extraction, and invasive species, many of which are regional in scale.
Additionally, we need to achieve an integrated understanding not only
of the nature and extent of physical and biological effects of climate
change, but also of their ramifications for our social and economic
The Organization of the U.S. Global Change Research Program
Our current understanding of climate change, as well as our
understanding of many other important global change issues, is the
result of the significant progress that has occurred over the last
several decades through scientific research. U.S. climate change
research is largely supported through the USGCRP. The Administration is
committed to continued strong support for the research needed to
improve our understanding of the mechanisms of the Earth's climate
system, the likely future course of climate change, and the potential
impacts of such change on the environment and human society.
The USGCRP, a program planned during the Reagan Administration and
elevated to a Presidential Initiative under President Bush in 1989, was
codified by the Global Change Research Act of 1990. The program has
been strongly backed by every Administration and Congress since its
inception. The FY2001 Budget Request demonstrates President Clinton's
ongoing commitment to the program, with an overall request for the
USGCRP of approximately $1.74 billion dollars, about 2 percent (or $39
million) higher than last year's enacted level (tables showing the
budget by agency and by program element area are attached).
Within the total, support for scientific research is up about $53
million (7%), including a $31 million increase for carbon cycle studies
at USDA as part of the carbon cycle research initiative begun last
year. Surface-based observations at NOAA are receiving a substantial
increase ($26 million, or about 39%) that will help provide new
information on changing patterns of temperature and rainfall in the US.
The total increase for surface-based observations and science together
is about $79 million, or 10%. The space-based observation component of
the budget is reduced by about $40 million, to a total of $897 million.
This decrease is mainly a consequence of decreases in NASA development
costs as some of the first series of Earth Observing System (EOS)
satellites are completed and launched.
The fact that the increase in science funding more than offsets the
decrease in funding for space-based observations is important.
Increasing the proportion of program funding for science has been one
of the most consistent recommendations from the National Research
Council and various agency advisory committees over the last few years.
The National Research Council (NRC) report, Global Environmental
Change: Research Pathways for the Next Decade, noted that 65 percent of
the total USGCRP were devoted to space-based observations and data
systems in the 1996 budget proposal. In this year's budget proposal,
the equivalent number is about 52 percent, demonstrating the progress
that has been made over the last 5 years in increasing the proportion
of USGCRP funding for scientific research and analysis.
Since its inception, the USGCRP has been directed toward
strengthening research on key scientific issues, and has fostered much
improved insight into the processes and interactions of the Earth
system. The results of research supported by the USGCRP play an
important role in international scientific assessments, including
assessments of climate change and stratospheric ozone depletion. The
USGCRP research results provide the scientific information base that
underpins consideration of possible response strategies. The USGCRP
does not recommend specific government policies responsive to global
change, nor does it include support for research and development of
energy technologies or development of mitigation strategies.
Participants and Organization
The Subcommittee on Global Change Research (SGCR) of the Committee
on Environment and Natural Resources (CENR), a component of the
National Science and Technology Council (NSTC), provides overall
direction and executive oversight of the USGCRP. In addition, the
National Research Council within the National Academy of Sciences
provides external oversight and review of USGCRP programs. Agencies
manage and coordinate Federally supported scientific research on global
change within this framework. In addition to USGCRP review of the
overall set of agency research programs, each agency is responsible for
the review of individual projects within its programs. These reviews
are almost exclusively based on an external peer-review process, which
is deemed an important means of ensuring continued program quality.
The agencies that actively participate in the USGCRP are USDA, DOC/
NOAA, DOE, HHS/NIH, DOI/USGS, EPA, NASA, NSF, and the Smithsonian
Institution. OMB and OSTP are the Executive Office of the President
liaisons to the SGCR. The Department of State does not fund research
but is part of the SGCR because of the extensive international
cooperation necessary in all aspects of global change research. The
Department of Defense does not fund research focused on global change,
but participates in the SGCR because it performs related research, such
as how changing ocean conditions may affect their ability to ensure the
nation's security. Some of these agencies support research on a broad
range of issues, while others have a more specialized focus.
Programmatic contributions are closely matched to agency missions and
areas of expertise. The crosscutting research that takes place in the
USGCRP program element areas takes advantage of the unique capabilities
of different agencies and applies them to science problems that are
beyond the scope of any single agency's mission or the ability of any
one agency's programs to address.
The scientific community contributes to the planning, definition,
and implementation of USGCRP research activities. An important aspect
of this is scientific oversight and review of the USGCRP that is
provided by the National Academy of Sciences. This function includes
review of various program activities and examination of scientific
issues in response to requests from the USGCRP and participating
agencies. Over the past several years, the USGCRP has commissioned a
series of reports, including ``Pathways'' and smaller reports on
climate observations and climate modeling. These reports have provided
important input to the ongoing planning and program implementation
decisions of the USGCRP agencies, including the initiation of the
carbon cycle and water cycle research efforts described above, and the
current organization of the USGCRP as a series of other interrelated
Understanding the Earth's Climate System, with a focus on
improving our understanding of the climate system as a whole,
rather than its individual components, and thus improving our
ability to predict climate change and variability. The FY2001
budget proposes $487 million for this program element (a
decrease of $16 million), which is largely focused on the
physical climate system. Improving our understanding of climate
change, including its potential impacts on ecosystems and human
society, requires support of research and integration of
results across the entire USGCRP. Climate is a naturally
varying and dynamic system with important implications for the
social and economic well being of our societies. Understanding
and predicting climate changes across multiple time scales
(ranging from seasonal to interannual, to decadal and longer)
offers valuable information for decision making in those
sectors sensitive to rainfall and temperature fluctuations,
including agriculture, water management, energy,
transportation, and human health.
Biology and Biogeochemistry of Ecosystems, with a focus on
improving understanding of the relationship between a changing
biosphere and a changing climate and the impacts of global
change on managed and natural ecosystems, including forests,
coastal areas, and agriculture. The budget proposes $224
million in FY2001 (an increase of $19 million) for the study of
changes in managed and unmanaged ecosystems. The biosphere
consists of diverse ecosystems that vary widely in complexity
and productivity, in the extent to which they are managed, and
in their economic value to society. Better scientific
understanding of the processes that regulate ecosystems and the
capability to predict ecosystem changes and evaluate the
potential consequences of management strategies will improve
our ability to manage for sustainability.
Composition and Chemistry of the Atmosphere, with a focus on
improving our understanding of the impacts of natural and human
processes on the chemical composition of the atmosphere at
global and regional scales, and determining the effect of such
changes on air quality and human health. The budget proposes
$368 million for programs studying the composition and
chemistry of the atmosphere (a decrease of $21 million from
FY2000). Changes in the global atmosphere can have important
implications for life on Earth, including such factors as the
exposure to biologically damaging ultraviolet (UV) radiation,
the abundance of greenhouse gases and aerosols (which in turn
affect climate), and regional air pollution.
Paleoenvironment and Paleoclimate, with a focus on providing
a quantitative understanding of the patterns of natural
environmental variability, on timescales from centuries to
millennia, upon which are superimposed the effects of human
activities on the planet's biosphere, geosphere, and
atmosphere. The budget proposes $27 million in FY2001 (a
decrease of $2 million) for the study of the Earth's
environmental past. Reconstructing the historical climate
record offers an enhanced understanding of the mechanisms
controlling the Earth's climate system and, together with
insight obtained from numerical modeling exercises, provides a
foundation for anticipating how the planet might respond to
future environmental perturbations.
Human Dimensions of Global Change, with a focus on
explaining how humans affect the Earth system and are affected
by it, and on investigating how humans respond to global
change. The budget proposes $93 million in FY2001 (level with
FY2000) for the study of the human dimensions of global change.
Scientific uncertainties about the role of human socioeconomic
and institutional factors in global change are as significant
as uncertainties about the physical, chemical, and biological
aspects of the Earth system. Improving our scientific
understanding of how humans cause changes in the Earth system,
and how society, in turn, is affected by the interactions
between natural and social processes, is an important priority
for the USGCRP.
This brief description of climate change science and U.S. climate
change research efforts should be seen as a summary rather than a
comprehensive overview. Nevertheless, it highlights several very
important points. The USGCRP is a broad and successful program of
research on global change that is resulting in increases in our
understanding of how the Earth system is changing, and of the human
role in such change. In particular, it has made a major contribution to
our understanding of climate change. USGCRP-supported research has
played a key role in demonstrating that climate change is occurring,
and that human activities are playing a role in causing such change. It
has helped explain the relationships between climate change and other
significant global-scale environmental changes, such as land cover
change, ozone depletion, and loss of biodiversity.
We expect a much fuller understanding of the processes of change to
emerge from this effort in the future. The sustained bipartisan support
for global change research over the last decade has enabled steady
scientific progress and resulted in the development of a new generation
of tools that offer the promise of more rapid progress in the years
ahead. We will benefit from unprecedented amounts of data about the
Earth, and these data will be of higher quality than ever before. We
will develop more complex and accurate models that permit more
realistic simulation of the Earth system. Most importantly, we can
expect to learn much more about the potential consequences of change
for ecosystems and for human society.
U.S. Global Change Research Program
By Agency/Appropriation Account
FY 2001 Budget
(Discretionary budget authority; in millions of dollars)
1999 FY 2000 FY 2001 Change
Actual Estimate Proposed 2000-2001
Department of Health and Human Services
National Institutes of Health 40 46 48 +2
National Aeronautics and Space
Science, Aeronautics, and Technology 1,155 1,173 1,149 -24
Department of Energy
Science (Biological & Environmental Research) 114 120 123 +3
National Science Foundation
Research and Related Activities 182 187 187 0
Department of Agriculture
Agricultural Research Service 26 27 36 +9
Cooperative State Research, Education and
Research and Education 7 7 14 +7
Economic Research Service 1 1 2 +1
Natural Resources Conservation Service
Conservation Operations 1 1 14 +13
Forest and Rangeland Research 17 17 20 +3
Subtotal--USDA 52 53 85 +32
Department of Commerce
National Oceanic and Atmospheric Administration
Operations, Research, and Facilities 63 67 93 +26
Department of the Interior
U.S. Geological Survey
Surveys, Investigations, and Research 27 25 25 0
Environmental Protection Agency
Science and Technology 17 23 23 0
Salaries and Expenses 7 7 7 0
TOTAL \1\ 1,657 1,701 1,740 +39
\1\ Note: Total may not add due to rounding.
U.S. Global Change Research Program
Details by Program Element/By Agency
FY 2001 Budget
(Discretionary budget authority; in millions of dollars)
1999 FY 2000 FY 2001 Change
Actual Estimate Proposed 2000-2001
Understanding the Earth's Climate System
National Aeronautics and Space Administration 324 310 271 -39
National Science Foundation 82 84 84 0
Department of Energy 64 68 73 +5
Department of Commerce/NOAA 38 41 59 +18
Department of the Interior 7 0 0 0
Smithsonian * * * *
Subtotal 515 503 487 -16
Composition and Chemistry of the Atmosphere
National Aeronautics and Space Administration 310 330 306 -24
National Science Foundation 18 19 19 0
Department of Energy 16 16 15 -1
Department of Agriculture 16 15 18 +3
Department of Commerce/NOAA 8 9 10 +1
Smithsonian * * * *
Subtotal 368 389 368 -21
Global Water Cycle
National Aeronautics and Space Administration 238 255 288 +33
National Science Foundation 10 10 10 0
Department of Commerce/NOAA 5 5 7 +2
Department of Energy 0 4 3 -1
Department of Agriculture 0 * * *
Subtotal 253 274 308 +34
Carbon Cycle Science
National Aeronautics and Space Administration 154 154 150 -4
National Science Foundation 13 13 13 0
Department of Energy 14 14 15 +1
Department of Agriculture 7 15 37 +22
Department of Commerce/NOAA 4 5 10 +5
Department of the Interior 3 3 4 +1
Smithsonian * * * *
Subtotal 195 204 229 +25
Biology and Biochemistry of Ecosystems
National Aeronautics and Space Administration 129 124 134 +10
Department of Agriculture 32 22 29 +7
National Science Foundation 27 29 29 0
Department of Energy 13 11 11 0
Department of the Interior 13 13 14 +1
Smithsonian 4 4 4 0
Environmental Protection Agency 0 2 3 +1
Subtotal 218 205 224 +19
Human Dimensions of Climate Change
Health and Human Services 40 46 48 +2
Environmental Protection Agency 17 19 20 +1
National Science Foundation 14 14 14 0
Department of Energy 5 8 5 -3
Department of Commerce/NOAA 5 5 5 0
Smithsonian 1 1 1 0
Subtotal 82 93 93 0
National Science Foundation 18 19 19 0
Department of Commerce/NOAA 2 2 2 0
Smithsonian 2 2 2 0
Department of the Interior 0 6 4 -2
Subtotal 22 29 27 -2
Total 1,2,3 1,653 1,697 1,736 +39
* less than $500,000.
\1\ Total may not add due to rounding.
\2\ FY 1999 does not include $3 million in DOE Small Business Innovative Research funding.
\3\ FY 2000 and FY 2001 does not include $4 million in DOI Data Management funding.
The Chairman. We will proceed during this hearing, at least
as far as this member is concerned, on the premise that there
is no such thing as a dumb question. This is an area where I
admitted in my opening statement that I have a very steep
learning curve. And as I also mentioned, this will be the
first, of what I hope to be a number of hearings, that we can
have on this issue.
First of all, what changed between the 1995 IPCC report and
today that has shifted the debate from ``Are we warming the
Earth?'' to ``How much are we warming the Earth?''
Dr. Lane. Senator, I think the simple answer is just that
more science got done, and became available, and then could be
analyzed by this international peer review process.
The Chairman. That is an important change, do you not
Dr. Lane. I think the change is important. It is--
particularly in the Academy report that was referred to--very
clear that there really is not any remaining debate about
whether the Earth is warming or not. It is quite clear that the
Earth is warming, and there is significant consensus that the
human activity is a part of that warming.
So I think it is time to focus on what that means in terms
of lives of people and nations. And that also involves
significant research questions, and that in part, what the
Global Change Research Program is all about.
It does not mean there are not still important questions
about the physics and the chemistry of climate change. And we
will continue to support those research activities to further
deepen our knowledge in those areas, but I think it is quite
clear that the larger questions have shifted. And it is
important the research program respond.
The Chairman. Do you believe that the upcoming report will
alter the current debate among scientists?
Dr. Lane. Senator, I think that many of these questions
have been subject to scientific debate, and that is how the
scientific process works. I would expect that increasingly
researchers will turn their attention to some of these more
complex questions, and we will see more attention in the
scientific arena to this research.
The Chairman. Are other nations devoting anywhere near the
time and assets and scientific effort that the United States
Dr. Lane. I can submit budget numbers to the Committee for
the record. I do not have them fresh in my mind.
The Chairman. Just your overall impression about that.
Dr. Lane. I would emphasize that, yes, the Global Change
Research Program, the U.S. program, is part of a much larger
international effort. And it, in my view, is one of the best
examples among several very good ones, of international
cooperation and science. The IPCC process involves hundreds of
experts in all aspects of climate change, the social sciences,
the economic sciences, as well as the physics----
The Chairman. Well, I do not mean to interrupt, but my
question is: Are other nations devoting the time and assets--I
understand we have a budget request for $1.74 billion. Are
other nations involving themselves with the degree of
commitment that we are?
Dr. Lane. My sense is that the degree of commitment on the
part of many nations of the world is very substantial, and in
the research area, which I think is what you would like for me
to address, the area of climate modeling is one in which, in
some sense, other countries are ahead of us. And that is an
issue for us to be concerned about.
We asked the Academy to study this question, give us a
report. And the Academy concluded that in the case of climate
modeling, the United States may be losing leadership to
researchers in other countries. So I would say in a case like
that, it is very clear that the commitment is quite strong.
The Chairman. A lot of our concerns here are anecdotal
obviously. We read where a huge piece of ice broke off from the
Antarctic. Does that mean anything to you?
Dr. Lane. I found that an extremely interesting story, as
well, and it is a true story. And I have been to the Antarctic
several times in my role as Director of the National Science
Foundation since National Science Foundation runs the U.S.
program down there. That was an extraordinary event.
One cannot really connect single events of that kind with
the larger issue of global climate change, and I think it would
be a mistake to do that. But there are many other examples such
as the receding of the glaciers and high country around the
world over the last several decades.
There is the fairly recent observation that the ice in the
Arctic region is less in extent and also thinner than we
anticipated. All those are very significant research questions
that do have a relationship with the Global Change Research
The Chairman. What about the disappearance of species of
Dr. Lane. We do have evidence that all kinds of life,
animal life and plant life, is responding to a global change.
Fish appear to be moving. There is much evidence of early
blooming of plants. In fact, even in Washington, the cherry
blossoms are blooming an average of a week earlier, I think the
number would be, than they were a decade or so ago.
So ecosystems all over the world are showing some unusual
movement that might be connected with climate change.
The Chairman. A lot of this is in the oceans, right?
Dr. Lane. Define----
The Chairman. A lot of these changes, we have seen in the
oceans. What about the death of coral reefs?
Dr. Lane. Coral reefs are dying all over the world. It is a
serious problem. Some would predict that without finding the
cause and doing something about it, we could lose essentially
all of our coral reefs in the next 100 years.
We have a significant research effort trying to understand
the problem with coral reefs. Scientific opinion is that there
may be several causes, including global warming, which sort of
chases the algae out of the coral.
The Chairman. What are some of the other reasons?
Dr. Lane. Some of the others are pollution, some damage
just from the human interaction directly with the coral, coral
disease from causes we do not entirely understand. But there is
a pretty strong opinion that the warming of the oceans may very
well be responsible for loss of coral.
A recent example of that is with the El Nino event which
may or may not be connected with overall global climate change,
but which is a very significant climate feature. During the
last severe El Nino, there was considerable coral bleaching and
loss of coral due to the increased temperatures.
So we know that if you increase the temperature of the
ocean over the coral, you will lose coral. We simply do not
know how large that effect is versus other possible problems
that we have with our coral reefs.
The Chairman. It seems to me that it is almost like
connecting the dots here. We see example after example ranging
from ice breaking up in the Antarctic to the death of coral
reefs to the inexorable increase in water levels, oceanic
levels. Does that make any sense, or is it just that we are
being a little bit hysterical?
Dr. Lane. I think--picking up on your earlier statement,
Mr. Chairman, I think the public understands something is going
on, something is happening.
Scientifically, the experts, who you will hear from
shortly, have the data, and the analysis, and the modeling to
show just what we know in detail scientifically and where the
questions remain. But there are things going on that point to
potential problems that perhaps we do not have what we would
consider reliable scientific data on yet, but in time, we will
better understand how the various dots connect. And maybe there
is a dot that does not connect.
Maybe there is some phenomenon out there that looks like it
might connect with climate change, but in the end, we find it
has nothing to do with it. We cannot know that for sure right
That is why I think having the discussion about the science
and helping the public understand--as you emphasized, Mr.
Chairman, we need to do--what the science is and how the
science consensus is formed, and why there will be debate and
differences of opinion among experts, that is all good.
That is the way science advances, and I think this
potential for harm to the people of our country and our world
due to global climate change is so great that it behooves us to
have this discussion, and have it as early as we can, and make
the necessary investment to try to get the answers to some of
these remaining questions.
The Chairman. By intent, our next panel has experts of
contrasting views. And I think that that is the most important
and only fair way to address this issue.
When do you think--if we did everything in a perfect
scenario, when do you think we could have some definitive
answers to these largely unanswered questions, or some of them?
In other words, what can we as Americans expect out of the
scientific community and out of the $1.74 billion investment in
the U.S. Global Change Research Program?
Dr. Lane. Senator, I think that we can expect significant
progress in answering some of these questions. What the experts
sort of need to help the Committee understand is ``Which are we
most likely to be able to pin down first, and which are we
going to pin down next?''
For example, one reason we are felt by the Academy to be
falling a bit behind in our climate modeling has a lot to do
with computer capability. I mean, our modelers are among the
top experts in the world in this area, but for a variety of
reasons, they really do not have access to the kind of computer
capability that they need to run these big models.
So, as we address that, and we are doing so in the
President's information technology initiatives that have
received bi-partisan support, we will provide that capability.
Then we will be able to run these models, get the error bars
down, and answer the questions most directly.
So I hesitate to speculate on a particular question that
``I think we are going to answer in 1 or 2 years,'' but the
progress has been very good since the last IPCC report. And I
would anticipate just as great progress answering the remaining
questions in the next period.
The Chairman. Will we have some definitive answers within
the next couple of years?
Dr. Lane. I would expect we will have some definitive
answers in the next several years. For example, places where we
have made significant progress is in understanding the role--I
emphasized the importance of clouds--understanding the role of
One of the big uncertainties in the model is how clouds
behave and how most appropriately to put them in the model.
The second one is the effect of aerosols. Generally, the
view is that aerosols, which can be anything from ice to
crystals of other kinds and soot--just tiny little particles
that are suspended in the atmosphere--the thought has been that
those would generally have a cooling effect. They would reflect
the sunlight before it gets down and has a chance to heat the
earth and contribute to global warming.
By and large, my own view is that still is probably true,
but there was a recent report from our international research
activity in the Indian Ocean where the aerosols turn out to be
quite dark and pollution is very heavy. It looks as if those
aerosols are actually not reflecting light very well.
They are heating up. They themselves then, in their
interaction with the clouds, are causing the clouds to
dissipate, and that is having a warming effect. We need to
understand that--my guess is that those are areas: clouds, ice,
which I did not mention, and aerosols, in which we would be
able to make significant progress in the next few years, but I
would concede to my experts on the subject for their estimate.
The Chairman. Senator Kerry, thank you for being here.
STATEMENT OF HON. JOHN F. KERRY,
U.S. SENATOR FROM MASSACHUSETTS
Senator Kerry. Thank you, Mr. Chairman, and thank you very
much for having this hearing and for your willingness to open
up the dialogue with respect to this issue. I have been
interested in and have been involved in this issue for a long
period of time now.
In my responsibilities as a Senator I had the privilege of
joining Vice President Gore, Tim Wirth, John Chafee, and others
as a member of the delegation down in Rio for the first Earth
Summit when President Bush embraced the early findings of
scientists regarding global warming.
I subsequently have been at the Buenos Aires followup
meeting, and I was working with Stu Eisenstat and others in
Kyoto where the negotiations took place. Stu, I think, did a
very brilliant job in helping develop the Kyoto Treaty.
And I must say, Mr. Chairman, I have been a little bit
dumbfounded and somewhat disturbed by the level of skepticism
that exists, and has existed over a long period of time, in the
U.S. Congress with respect to this issue.
We may not have definitive answers for every model, as to
exactly what forest may move, or precisely how much the sea may
rise in a particular area over what period of time, but we
have--correct me if I am wrong, Dr. Lane--absolutely definitive
science to tell us that the ocean is rising, and that there are
a number of pollutants that we emit.
I mean, there is a health issue here, not just a question
of the effect of global warming. Over the last years, the
science just keeps getting stronger, and stronger, and
stronger, reinforcing the theories. The world has, frankly,
moved more rapidly than the United States.
And in answer to your question--a couple of weeks ago, we
had a dinner with the Deputy Prime Minister John Prescott, who
heads up negotiations for Great Britain, and with the Dutch,
and others here in Washington, talking about the next meeting
that will take place in Berlin. There are great concerns about
the United States' lack of response.
Frankly, the lack of response by the United States is
significantly impeding our capacity to bring less developed
countries into the equation. I am all for the Senate Resolution
passed in the 105th Congress, which supports this goal of the
Kyoto Protocol. If we let Mexico, and Korea, and India, and
China proceed to develop without being participants, they can
negate every gain that we take in the United States. So, this
is a global problem.
But right now, there is such antipathy directed at the
United States for our lack of seriousness about this, that few
people are willing to join us in a serious dialogue until we
demonstrate a little bit of leadership.
Let me just say, Mr. Chairman, that the science--and we
will hear this from two of our witnesses this morning--on a
scale of virtual certainty from one to ten, it is ten out of
ten. It is virtually certain that some changes indicative of
climate change are now happening.
And, Dr. Lane, you will confirm, as every scientist here
will, that the half life of carbon dioxide and of the other
greenhouse gas emissions is such that if we just went cold
turkey today and brought our levels down to the 1990 baseline
where we are supposed to be according to the Rio voluntary
agreements, we would still have 70 years of global warming
effects that are going to occur because the gases have long
half lives. Therefore, the danger of global warming is going to
continue no matter what we do today even if we are successful
at reducing emissions.
The complexity of global warming can be so daunting that it
partly is a turn-off to people. They do not want to cope with
it or try to grapple with it because the problem is quite
Now again, I say, I know we do not have certainty in the
model, and, to a degree, people fight about the trivial
matters. Do we know whether or not Florida is by year such and
such absolutely going to lose the Miami beaches? No, we cannot
say exactly what year or when, but we have absolute certainty
as to the rise in sea level, a range that is disastrous. Take
even the bottom line of the range--we know it is disastrous.
Now, we know the worldwide rise in temperatures at the
earth's surface is real. We know it has accelerated in recent
decades. The independent scientific panel organized by the
National Academy of Sciences concluded in a major report issued
this February that they now have that sort of certainty. They
estimate the increase in temperatures in the past century
between .7 and 1.4 degrees Fahrenheit. That is a 30-percent
increase from earlier projections that reflect record
shattering high temperatures in the late 1990's.
We now have learned how to deal with the disparity between
the satellite findings of the upper atmosphere versus what we
have on earth, and it sort of makes sense that it is going to
be warmer down here than it is up there in terms of the ratio
And I might say, Mr. Chairman, this sounds sort of
fundamental, but it really goes to the bottom of this. The
theory about this was found by a fellow named Arhenius in 1898,
and it has progressed since then.
And every prognostication of the early scientific data on
this has been eclipsed by the subsequent findings of fact. Each
time it has blown away the theory in terms of being more
serious than people thought.
But the fact is that life exists on earth because we have a
greenhouse effect. Were it not for the existence of the
greenhouse effect, we would not have plant life and human life.
And it is common sense that if you are emitting gases into
that atmosphere that are trapped, it will have a long-term
impact on weather and other things.
Well, we now find that for the third year in a row we have
set a record for winter warmth. The 3-month period of December
1999 through February of 2000 was the warmest winter season in
the contiguous 48 states in the entire 105 years that we have
recorded the data.
That slightly surpassed the record set just one year ago,
and that slightly surpassed the record set the prior year. So
we have the three warmest years in the last 3 years. And that
fits in completely with the detected trend about later freezes
in the fall, and earlier temperatures of the frost.
I remember as a kid in Massachusetts, we always looked
forward to October/November because the ponds froze over and we
were going to have thick ice, and go play hockey. Today, you
are lucky if the ponds freeze in Northern New Hampshire.
And unlike the days when we used to have snow on the ground
from October to April when we were campaigning as recently as
20 years ago, I used to freeze and wear a coat in the morning.
I do not wear a coat until after November now.
Anybody who does not see the impact of these changes is
putting their head in the sand. Now, can we say that every bit
of this is due to global warming? The answer is no. I cannot
sit here and tell you that. No scientist is going to tell you
that every bit of it is. Some of it may be normal changes that
are taking place in terms of the climate process, but we do
know with absolute certainty, incontrovertible scientific fact,
we are contributing to it.
And we ought to adopt the prudent person theory with
respect to those things that you do not quite know what the
final consequences are going to be but you know they might be
It is like smoking, Mr. Chairman. You and others have
adopted a very tough policy on the odds about contracting
cancer from smoking. Does everybody get cancer who smokes? The
answer is no. But do we know what the probabilities are? The
answer is yes. The probabilities of this are greater than some
of what we know about the linkages of cancer in certain kinds
of disease. We take far more steps to deal with that than we do
Final comment I would make is, and this is of enormous
concern I think to everybody, is the great ice cover that
stretches across the top of the globe is about 40 percent
thinner than it was just 2 to 4 decades ago. We know this
through our data from nuclear submarines that have been plying
the Arctic Ocean.
Scientists from the University of Washington found in a new
study that the average thickness of the Arctic ice was about
ten feet from 1958 to 1976. From 1993 to 1997, it is about six
feet, and in the 1990's, the thinning has been continuing at a
rate of about four inches a year.
The area covered by sea ice has diminished and the duration
of the cover has shortened. Mountain glaciers in Alaska have
shrunk as has the Greenland ice cap. And the consequences of
this, according to many experts now, is huge concern about what
happens with sea levels because if the big ice sheets melt even
partly, sea levels will rise around the world.
And there are serious questions--I do not have the answers
again--about the potential disruption of certain ocean
currents, but those ocean currents modulate the earth's
climate. We do not know the answer of what happens to the Gulf
Stream, but I am concerned about the potential of what might
happen to it.
So this hearing and the further science is critical, but we
should not confuse ourselves by not having answers to every
single question that common sense drives us to try to mitigate
at this point in time. And I think that is really the critical
issue that this Committee, the Congress, and the entire country
Unless the United States is more serious about this effort,
we are going to have a difficult time getting less developed
countries and others to join in a more cooperative effort. So
there is a huge amount at stake and I think this hearing is
very important in that regard.
In each of the past 2 years, the House of Representatives
has included riders in appropriations bills on the Kyoto
Protocol. And this year, a new bill has language that is
included in the Agricultural Appropriations Bill that will
limit the Administration's activities on an international level
to even continue the dialogue and process of building a
consensus about Kyoto.
Do you share a concern that this provision could impede our
understanding of climate change and the ways we might mitigate
Dr. Lane. Yes, Senator, I am very concerned about this
rider. The rider seems, on the face of it, extreme. It tries to
block the United States from even trying to reach an agreement
with other countries on action to combat global warming, which
is very difficult to explain to our international partners
around the world.
It undermines the ability of the executive branch to
conduct international negotiations, which seems to me to raise
serious constitutional questions. It may stifle U.S. efforts to
achieve bi-partisan goals with a cost effective treaty and
meaningful participation of developing countries which,
Senator, you have emphasized.
It is extremely important that we are able to sit down with
developing countries and address their participation in dealing
with this problem of global warming.
The amendment is bad for American industry. It is bad for
the farmers. It is bad for consumers. It tries to stop work on
the most important tools for holding down costs as we combat
global warming. And depending on how you interpret the language
itself, it could also have a serious chilling effect on our
international research activities. So it is difficult to
understand the rationale here, and we certainly have great
difficulties with the rider.
Senator Kerry. I do not want to abuse the time too much,
but there is another problem I'd like to focus on. You go to a
place like North Dakota, or you go to some northern place, they
like the fact that it is warmer. Their heating bills are less.
They figure that their gardens are going to last longer; they
get a longer summer.
I mean, there is a psychological difficulty here to get
people to focus on what may happen to your water tables, to
your crops, to the movement of whole forests. Do you agree that
there are very significant down sides that have not yet been
properly quantified to people so that you can create a
consensus on this?
Dr. Lane. Indeed I do agree, Senator. I think this national
assessment I spoke about, which attempts, for the first time,
to provide some wisdom on what the regional effects of global
climate change might be, will help us understand better the
answer to your question.
There appear to be some positive benefits to increasing
temperature in certain parts of the country, certain parts of
the world. People might like a little warmer evenings, little
warmer winters, but that is kind of taking an isolationist's
view. You know, if you put a big wall up around your state or
your community, if that is the view of the world, then you
might like it a little warmer.
On the other hand, there are some very real questions. How
fast can the ecology keep up with the climate change? So
suppose the forests that need to move in response to climate
change cannot move fast enough, and so then they are gone. That
opens the way for all kinds of invasive species, plant and
animal, that might be very harmful. So we simply do not know
the answers to those kinds of questions.
I would also say that if we think we might be comfy in our
part of the country because it is getting a little warmer, and
maybe we can grow crops a little more easily, there are other
parts of the world are becoming destabilized, people are dying
from the spread of disease that could well be caused by climate
change, or significant coastal regions that are increasingly
densely populated around the world are going under water, if we
think that is a world in which we all could live comfortably,
then I think we need to look much more carefully at the
implications for climate change.
Senator Kerry. Thank you, Doctor.
Thank you, Mr. Chairman.
The Chairman. I just want to say, Senator Kerry, I thank
you for your involvement and many years on this issue. I am a
relative newcomer. I appreciate what you have done for many
years and your participation on this issue, and these hearings
are very important.
And I would like to add again, that I think we have tried
to find a balanced second panel that represent a variety of
views on this issue, and I think that is the best way we can be
educated on this issue.
STATEMENT OF HON. SAM BROWNBACK,
U.S. SENATOR FROM KANSAS
Senator Brownback. Thank you very much, Mr. Chairman, and I
want to congratulate you for once again taking leadership on an
important and tough topic in typical McCain fashion, grabbing a
hold and saying, ``Here is something that is tough to do, and
let us get after it.'' And I applaud you very much and hope you
hold a series of hearings on this.
And I also thank Senator Kerry for his leadership for a
long time on this topic as well.
Dr. Lane, you have made comments on a number of issues
here. I have got your testimony and caught the end of it, but I
want to focus on specifically the issue of CO2 in
the air, carbon dioxide in the air. And apparently, there are
some scientific questions that remain out here. There are a
number of them that are resolved and understood, and I think
there is unanimity on agreement that there is too much CO2
in the air. Is there anybody that disagrees with that point?
Dr. Lane. You could probably find somebody, but I think
that the consensus is precisely as you stated it.
Senator Brownback. And that you have in your statements the
factual--the loading of CO2 that is in the air and
what has occurred there. And I am a relative newcomer to this
topic as well, but as I have looked at it, I thought, we can
disagree on a lot of things, but here is one that I think
You may disagree about how it all got there, or how you
pull it out of the air, or some things like that, but there is
too much CO2, and it would be better if we had less
in the air. And everybody would agree to that, or I guess, most
would, although as Senator Kerry was talking about how he
looked forward to the winter and playing ice hockey, I was
sitting here thinking I was out cutting holes in the ice to
water cattle, and I did not like that, as thick as it got.
It is not that I am saying we should have global warming. I
do not agree with that. I am not for global warming, but we
just did not play the ice hockey. I had to cut ice holes.
Senator Brownback. I put forward a bill along with Senator
Kerrey from Nebraska that tries to get more carbon
sequestration taking place in agriculture in this country, a
domestic component. And we have got an international component
we are putting forward of trying to have more carbon
sequestration taking place internationally; the international
component by tax credits, the domestic component by carbon
payments to farmers along the model of the CRP, the
Conservation Reserve Program style.
It seems to me that if we all agree that we have too much
CO2 in the air--and you can kind of disagree about
``Here is the impact, or this is how it got there.'' If you
just step past that one and say, ``We have got too much
CO2 in the air. How do we get it out,'' here are a
couple of ways of doing that.
And the research is coming along pretty well on no till
farming, different biomass cropping practices of their ability
to sequester carbon in the soil. The research is pretty good on
the amount of carbon that has been released from U.S. soil over
the years of our agricultural practices so that--we know it has
the capacity to fix it back, because at one time it had a
higher degree of carbon in the soil. And we know that as well
internationally from a number of the forests that have been
uprooted, that if you started or re-instilled those forests, or
did not take them down in the first place, you would be
releasing less carbon into the atmosphere.
I would like your thoughts about those two approaches on
addressing the issue of carbon sequestration and taking carbon
out of the atmosphere.
Dr. Lane. Senator, this is clearly a very important issue
on which a great deal of progress has been made in
understanding the science, but there is much more to do.
There is, in the Fiscal Year 2001 budget, a significant
initiative this year and last, for the part of the U.S. Global
Change Research Program focused on carbon sequestration. It is
one of the ways that we expect that we will be able to remove
carbon from the atmosphere.
The second thing I might say here is that the recent IPCC
report on land use and land use change and forestry, addresses
this issue and provides important international consensus on
what the issues are here, and the remaining scientific
questions, but also what we know.
Our understanding of the matter so far is that there is
significant potential for removal of carbon dioxide through
changes in land use. Just exactly how much is still quite
widely debated. The error bars, we say, in the science
community are rather large on that.
I think most would feel at this point that even with all
kinds of reasonable land use changes, and accounting for that,
it would not be enough to deal with the enormous increases that
we project in carbon dioxide, but it is very important.
And I think the only issue then is: How do you deal with
that in terms of our international discussions? So there are
some important research questions to continue to get at.
There are also some serious policy issues in any kind of
international agreement on dealing with the greenhouse emission
problem. It is important to have the right agreement on how you
account for land use in each country's participation in
reducing greenhouse emissions, or removing carbon dioxide from
the air. And that is an issue that needs to get sorted out. It
is clearly going to be very important for both developed and
And then I know we have got panelists that can address that
more precisely. So there are policy issues that are big ones,
and have to do with how reforestation, and biomass, and no till
farming, how all that would get counted in any kind of
international agreement of removal and reduction of greenhouse
Also, even if we knew all we need to know about this,
actually getting it in practice in our country and in other
countries is challenging also. And that has major policy
But the issue is important. There is no doubt that this is
a place we must look to to help with the carbon dioxide
Senator Brownback. So you support doing it, but your
reservation is that you want it done in a global context.
Dr. Lane. It must be done in a global context.
Senator Brownback. I mean, if I could challenge you for a
minute on that. It seems to me that it would be useful for us
to start moving that way now, and learning from wide scale
implementation of those practices, and that that is a benefit.
I do not see that you do any harm, and you actually do a
great deal of good, and you probably learn a lot by scaling up
and doing those things, and doing it now.
Dr. Lane. Without question, I think the--first of all, the
science is something we are doing now, and should continue to
increase our investments in this particular area of carbon
sequestration. There is no reason the United States should not
play a leadership role here as it does in so many other areas.
And so nothing says that if one sees a good thing to do, one
should not proceed to do it.
Senator Brownback. Because, I mean, it seems like to me,
that that almost gets us to Senator Kerry's point about the
United States showing some leadership on this, whereas there
has been great concern about the Kyoto Treaty for the reasons
that you articulated of a number of countries being allowed out
of it that could offset any sort of gain that the United States
And that you almost could get past that issue as well, and
in doing something here that is a good and right thing to do,
that would show strong and aggressive U.S. leadership. And it
would be a positive thing to do.
Dr. Lane. But I do want to emphasize that our current
assessment is that even under ideal land use, it is not
expected to take care of the whole problem.
Senator Brownback. No, I understand you on that. And I
would not submit that it would, although I will submit that the
research I have looked at, looks like it is very promising and
will take care of a good portion of the problem. It does not do
it all, but it has got a chance to really help us out in a very
significant way. I will look forward to pursuing that with the
We have the one bill that is out there that will be
considered. I think as we re-write the farm bill, there will be
a lot of looks at the issue of carbon sequestration, and I
would hope that we could do an aggressive support
internationally to other places that are looking to do the
right thing. We can help in supporting that as well as keeping
the carbon from either, first, ever being released, and
increase the amount that is sequestered into the ground.
Dr. Lane. Senator, we applaud your efforts here with the
bill, and look forward to working with you on these matters
that I just addressed.
Senator Brownback. I look forward to working with you.
Mr. Chairman, I have an opening statement I want to submit
for the record, too, if I could.
The Chairman. Without objection.
[The prepared statement of Senator Brownback follows:]
Prepared Statement of Hon. Sam Brownback, U.S. Senator from Kansas
Thank you Mr. Chairman. I commend you for holding a hearing on a
topic as important and as controversial as climate change.
Scientists generally agree that atmospheric concentrations of
carbon dioxide are now projected to double by the middle of the next
century--and continue to rise. This additional carbon in the atmosphere
could lead to a number of disastrous consequences including
significantly higher temperatures--which could have a detrimental
affect on certain forms of agriculture, disruption of ocean currents--
leading to an increase in natural disasters, and coastland destruction.
The potential effects from global warming are serious and warrant our
close attention and study.
The issue of climate change has been most closely linked to the
international treaty on climate change--the Kyoto Treaty. This treaty
had several flawed components and is highly unlikely to become policy--
nor should it. However, the issue of climate change should not be
linked solely to any one treaty. Instead, it is vital that we continue
our research and look for pro-active measures which can be taken to
reduce carbon dioxide in the atmosphere without sacrificing our economy
or our standard of living. Voluntary, incentive-based measures to
improve the environment should be pursued regardless of the Kyoto
Treaty. In the debate on climate change, there is a middle ground--it
doesn't have to be an all or nothing proposition.
Recently, I have introduced legislation which would provide
financial incentives to landowners who increase conservation practices
which help pull carbon dioxide out of the atmosphere and store it as
carbon in the soil. The Domestic Carbon Storage Incentives Act of
2000--seeks to encourage the positive contributions to the environment
made by the agriculture industry.
My bill focuses on offsetting greenhouse gases through improved
land management and conservation. As a result, these practices will
also lead to better water quality, less runoff pollution, better
wildlife habitat and an additional revenue source for farmers. It is a
win-win proposition for agriculture and the environment. We must look
for more of these opportunities if we are to avoid the often discussed
negative economic impacts that a global climate treaty could bring--and
research is vital to that goal.
There are currently efforts to prevent the agencies (USDA in
particular) and the administration from even researching this issue. I
understand the complex and controversial nature of climate change. That
is all the more reason to encourage voluntary efforts to mitigate the
problem and carefully study the science--not to avoid the issue.
Again, I commend my colleague for holding this hearing and I look
forward to the testimony and debate it may inspire.
The Chairman. Thank you, Dr. Lane. Thank you very much for
your great work and for appearing before the Committee.
Dr. Lane. Thank you very much, Mr. Chairman, Senator Kerry.
The Chairman. Our next panel will be Dr. Ray Bradley,
Department Chair, Department of Geosciences, University of
Massachusetts; Dr. John R. Christy, Director of the Earth
System Science Center, University of Alabama; Dr. Jerry
Mahlman, Director of Geophysical Fluid Dynamics Laboratory of
the National Oceanic and Atmospheric Administration; Dr. Kevin
Trenberth, Director of the Climate Analysis Section of the
National Center for Atmospheric Research; Dr. Robert Watson,
Chairman of the Intergovernmental Panel on Climate Changes here
in Washington, D.C. Thank you.
Dr. Bradley, please, we will begin with you.
STATEMENT OF DR. RAY BRADLEY, DEPARTMENT CHAIR, DEPARTMENT OF
GEOSCIENCES, UNIVERSITY OF MASSACHUSETTS
Dr. Bradley. Thank you, Senator. I would like to thank you
for holding this hearing on a very important issue.
Studies of instrumental temperature measurements from
around the world show that the climate of the 20th Century was
dominated by universal warming. At the end of the 20th Century,
almost all parts of the Earth had temperatures that were higher
than when the century began.
This conclusion is supported by numerous lines of
environmental evidence, melting of glaciers, retreat of sea
ice, changes in vegetation, rising of sea level, et cetera. At
the same time, concentration of greenhouse gases in the
atmosphere increased to levels that were higher than at any
time in the last 420,000 years. Carbon dioxide levels are now
35 to 40 percent higher than they were in the middle of the
19th Century. This change is largely the result of fossil fuel
I do not believe that the evidence for 20th Century
warming, or for these extraordinarily high levels of greenhouse
gases can be seriously challenged. However, the big question as
you mentioned is: What has caused the warming? Is it just a
natural change in climate, and does it have anything to do with
these increased levels of greenhouse gases?
With only 100 or 150 years of globally extensive
instrumentally recorded climate data, we have quite a limited
perspective on natural climate variability and its relation to
the phenomena that might have caused climate to change such
things as we call our forcing factors.
To obtain a longer perspective requires that we examine
climate dependant natural phenomena that in some way have
preserved a record of past climate. The most important of these
are tree rings, ice cores, banded corals, these laminated lake
and marine sediments, as well as historical records of past
In recent studies, we have assembled the best of these
records to produce a global picture of how temperatures changed
over the last 1,000 years as shown in this figure.
Dr. Bradley. In spite of the uncertainties that such a
reconstruction entails--and that is--the uncertainty is
demonstrated here by the yellow shading.
The record shown here of mean annual temperature for the
Northern Hemisphere, shows the temperature slowly decline over
the millennium. However, this downward trend changed abruptly
to a strong warming trend in the--early in the 20th Century.
And this rate of warming was unprecedented in the last
1,000 years. The warming continued through the 1990's making
that decade the warmest in at least 1,000 years. Indeed, 1998
was arguably the warmest year of the millennium, and 1999 was
only slightly cooler.
What can this one perspective on temperature tells us about
natural climate warming? By comparing it with the records of
various factors that may have affected the temperature.
It is a pattern of variations in the amount of energy
emitted by the sun, major explosive volcanic eruptions, and
perhaps slight changes in the position of the earth in relation
to the sun, were responsible for much of the variability of
temperatures leading up to the 20th Century.
However, these natural effects were completely overwhelmed
in the 20th Century by the increasing effective greenhouse
Dr. Bradley. Human effects on the climate system variations
now appear to dominate over natural factors. If the variations
of these natural factors continue into the future and are
similar to those of the last 1,000 years, it is unlikely that
they will be of great importance since the climatic changes
will be mainly affected by human-induced changes in greenhouse
Earlier I noted that the levels of two important greenhouse
gases, carbon dioxide and methane, were now higher than at any
time in the last 420,000 years.
Dr. Bradley. Carbon dioxide levels have risen from fairly
steady background levels to present day levels in a little over
a century; on this time scale, almost instantaneously.
This rate of change has no parallel in historical past,
just as temperatures recorded in the late 20th Century were
Most of the change in carbon dioxide and the greenhouse
gases resulted from the growth of world population and the
insatiable demand for fossil-fuel based energy.
Given that the world population will almost certainly
double from the present level of 6 billion within the lifetime
of those who are currently in kindergarten, unless something is
done to curb the use of fossil fuel consumption, it seems very
likely that significant change in climate will occur in the
Consider again the record of temperature over the last
Dr. Bradley. An important conclusion of my long term
climate studies is that until the second half of the 20th
Century, temperatures generally remained within a half degree
Celsius, one degree Fahrenheit of the average for the baseline
which we use, which is 1902 to 1980.
The latest IPCC long phased projection of future climate
point to a temperature a temperature rise of .6 to 2.2 Celsius,
1 to 4 Fahrenheit above 1990 levels by 2050. I think this graph
puts it all into perspective.
Dr. Bradley. Clearly, these estimates have pretty large
uncertainties. This shaded area to the right is the model based
estimates of future change.
But it is important to know that even the lowest would be
far beyond the range of temperatures in the last 1,000 years.
If these estimates are even close to being correct, we are
heading into uncharted waters relative to the climate over the
last 1,000 years.
Should we be concerned that the climate may change
significantly in the future? I have focused exclusively here in
the changes of temperature. The temperature change is only one
component of our overall climate system.
Changes in temperature are associated with variations in
rainfall, the amount of snow, frequency of floods and droughts,
El Nino, or El Ninos events, shifts in storm tracks and
hurricanes, et cetera.
Our economy and way of life has become highly dependent on
certain expectations regarding climate. Much of our
infrastructure for water supply, for agriculture, and
transportation, was built on the assumption that climate would
operate in the future pretty much as it has in the past.
A relatively small shift in average global or hemispheric
temperature when it is associated with the atmospheric
circulation, rainfall patterns, et cetera, can be highly
disruptive to society. We have seen many examples of such in
recent decades, yet temperatures that were warm were nowhere
near the levels that may be reached later on in this century.
Now, these include extremes of rainfall leading to
catastrophic flooding in some areas, droughts, exceptional
wildfires, historically low lake levels elsewhere, as well as
an increase in windstorms and other weather related disasters.
Unusual weather events are becoming less uncommon, in fact with
agriculture, transportation, and commercial activity, a fact
noted with concern by major international property insurance
Can we be certain that future climate will involve
unprecedented risks? Can we be certain? Some argue the
processes within the climate system will act to compensate for
the effects of high greenhouse gas levels, some call negative
According to this scenario, these feedbacks will help
maintain the climatic status quo, enabling us to continue to
contaminate the atmosphere with greenhouse gases.
There is a small chance that such critics are right in
which case it would be safe to do nothing. But they may be
completely wrong and, indeed, the scientific consensus is that
they are wrong.
Political decisions, as you well know, inevitably involve
assessing risk and weighing the consequences of action versus
inaction. Congress must decide and must weigh the potentially
catastrophic environmental and commercial consequences of
future global warming against the costs of limiting fossil fuel
consumption to reduce these risks.
Given that it will take many decades to stabilize
greenhouse gas levels in the atmosphere, even if strong action
was taken today, as Senator Kerry pointed out, to limit fossil
fuel consumption, the issue is urgent and demands our
Scientists cannot provide Congress with a certain forecast
of the future. As our research on global warming continues, our
understanding will undoubtedly change. But the picture at
present, is that we are indeed living in climatically unusual
times, and that the future is likely to be even more unusual.
And I believe we ignore this prospect at our peril.
The Chairman. Thank you very much.
[The prepared statement of Dr. Bradley follows:]
Prepared Statement of Dr. Ray Bradley, Department Chair, Department of
Geosciences, University of Massachusetts
CLIMATE IN PERSPECTIVE:
HOW DOES PRESENT DAY CLIMATE DIFFER FROM CLIMATES IN THE PAST?
My name is Raymond Bradley. I am the Head of the Department of
Geosciences, and Director of the Climate System Research Center, at the
University of Massachusetts, Amherst. My research interests are in
climate variations during the last century and how these compare with
variations over longer periods. This involves studying both
instrumental records of climate, and paleo-records--natural phenomena
that have in some way registered past changes of climate in their
structure (for example, tree rings, ice cores, lake sediments, banded
corals etc). Using such ``proxies'' of climate enables the short
instrumental record to be extended back in time, so it can be placed in
a longer-term perspective. Like other witnesses here, I have served on
many national and international committees related to climate
variability. Most recently I was Chairman of the Past Global Changes
Project of the International Geosphere Biosphere Programme (IGBP-
PAGES), a member of the National Research Council Panel on Climate
Variability on Decade-to-Century Time Scales, and I have been
contributing author to all of the Intergovernmental Panel on Climate
Change (IPCC) scientific assessment activities. I have written or
edited 8 books and numerous articles on climatic change.
We are living in unusual times. The climate of the twentieth
century climate was dominated by universal warming; almost all parts of
the earth had temperatures at the end of the century that were higher
than when it began. At the same time, the concentration of greenhouse
gases in the atmosphere increased to levels that were higher than at
any time in at least the last 420,000 years. These observations are
incontrovertible. Global warming is real and the levels of greenhouse
gases (such as carbon dioxide) are now 35-40% higher than they were in
the middle of the 19th century. This change in greenhouse gas
concentration is largely the result of fossil fuel combustion. What is
less certain is whether the observed global warming is due entirely to
the build-up of greenhouse gases, or to other ``natural'' factors, or
to a combination of both. Here I provide a longer-term perspective on
the issue by focusing on the evolution of climate in the centuries and
millennia leading up to the 20th century. Such a perspective
encompasses the period before large-scale contamination of the global
atmosphere and global-scale changes in land-surface conditions. By
studying both the record of past climate variability and factors that
may have caused climate to change (``forcing factors''), we can
establish how the climate system varied under ``natural'' conditions,
before human effects became significant on a global scale. Although
there is considerable uncertainty about the rate and magnitude of any
future warming which may occur as a result of human activities, one
thing is not in dispute: any human-induced changes in climate will be
superimposed on a background of natural climatic variations. Hence, in
order to understand future climatic changes, it is necessary to have an
understanding of how and why climates have varied in the past. Of
particular relevance are climatic variations of the last few centuries
leading up to the recent warming trends observed in instrumental
For most parts of the world, instrumental records of climate rarely
span more than a century. We thus have a very limited perspective on
climate variability and its relationship to potentially important
forcing factors. To obtain a longer perspective requires reliance on
climate-dependent natural phenomena that have preserved, in some way, a
record of past climate. The most important of these are tree rings, ice
cores, banded corals, varved lake and marine sediments, as well as
historical records of past weather conditions (see Appendix 1). In
recent studies we have assembled the best of these records to produce a
global picture of how temperature has changed over the last 1000 years
(Figure 1). It is worth noting that it is not sufficient to select one
or two records; an extensive network is needed to obtain a global
assessment. Just as listening to one instrument would not capture the
full beauty of a symphony, so one can not hope to say anything
meaningful about global climatic change by using data from only one
Figure 1. Mean annual temperatures for the northern hemisphere since
A.D. 1000. Values are shown as anomalies from the average for 1902-1980
(from M.E. Mann, R.S. Bradley and M.K. Hughes, 1999: Geophysical
Research Letters, v.26, p.759-762).
In spite of the uncertainties that such a global reconstruction
entails, the reconstructed record (of mean annual temperature for the
northern hemisphere) shows that temperatures slowly declined over the
millennium, with especially cold conditions in the 15th, 17th and 19th
centuries. This colder period is generally referred to as the ``Little
Ice Age,'' when glaciers advanced in most mountainous regions of the
world. However, the downward trend changed abruptly to a strong warming
trend early in the 20th century and this rate of warming was
unprecedented in the last 1000 years. The warming continued through the
1990s making that decade the warmest in at least 1000 years; indeed,
1998 was arguably the warmest year of the millennium, and 1999 was only
What can this longer perspective on temperature tell us about
natural climate variability? By comparing it with the records of
factors that may have affected temperature, it is apparent that
variations of solar irradiance (the total energy emitted by the sun),
major explosive eruptions and perhaps changes in the position of the
earth in relation to the sun (slight orbital variations) were
responsible for much of the variability of temperatures leading up to
the 20th century. However, these ``natural'' effects were completely
overwhelmed in the 20th century by the increasing effect of greenhouse
gases. Human effects on climate system variability now appear to
dominate over natural factors. If variations in ``natural'' forcings in
the future are similar to those of the last millennium, it is unlikely
that they will be of great importance since climatic changes will be
mainly affected by anthropogenic (human-induced) increases in
What significance does the paleo-record of temperature have for
future climate? An important conclusion from our long-term climate
studies is that until the second half of the 20th century, temperatures
generally remained within 0.5+C (1+F) of the average for
1902-1980 (the arbitrary baseline we used in our studies). The latest
IPCC model-based projections of future climate point to a temperature
increase of 0.6 to 2.2+C (1 to 4+F) above 1990 levels by
2050. Clearly, these estimates have large uncertainties, but it is
important to note that even the lowest value would be far beyond the
range of temperatures in the last millennium. If these estimates are
even close to being correct, we are heading into uncharted waters
relative to the climate of the last 1000 years.
Why should we be concerned about global contamination of the
atmosphere and future changes in climate? Earlier, I noted that the
levels of two important greenhouse gases (carbon dioxide and methane)
were now higher than at any time in the last 420,000 years (Figure 2).
In fact, this conclusion is based on measurements from the longest ice
core record available (from the Russian Vostok station in Antarctica)
but it is likely that current levels are higher than at any time for
several million years. To put this in perspective, recall that it was
only 10,000 years ago that human society first developed agriculture,
and 120,000 years ago sabre-toothed tigers roamed what is now Trafalgar
Square. Yet carbon dioxide levels have risen from fairly steady
background levels (270ppmv) to present day levels (370ppmv)
in a little over a century. This rate of change has no parallel in the
historical past, just as temperatures recorded in the late 20th century
were unprecedented. Most of the change in CO2 and other
greenhouse gases resulted from the growth of world population and the
insatiable demand for fossil fuel-based energy. Given that world
population will almost certainly double within the lifetime of those
currently in kindergarten, unless something is done to curb the use of
fossil fuel consumption, it seems very likely that significant changes
in climate will occur in the near future.
Figure 2. Changes in atmospheric carbon dioxide and methane levels in
the atmosphere over the last 420,000 years (from gas bubbles trapped in
an ice core, from Vostok, Antarctica).
Should we be concerned that the climate may change significantly in
the future? Here I have focused exclusively on changes in temperature,
but temperature change is only one component of our overall climate
system. Changes in temperature are associated with variations in
rainfall and the amounts of snow, shifts in storm tracks and hurricanes
etc. From the record of past climate, we know that a relatively small
overall change in global temperature can have significant environmental
effects. The ``Little Ice Age'' was characterized by dramatic changes
in ice cover in mountain regions throughout the world. But historical
records from lowland areas of Europe also document more extensive snow
cover, longer periods when rivers and lakes were frozen over and
frequent cold, wet summers, with disastrous consequences for
agriculture, leading to social disruption and political upheavals. Such
changes all occurred with an overall change in average hemispheric
temperature of less than 1+F. Of course, in trying to anticipate the
effects of future climate change, we are looking at the consequences of
warmer, not colder conditions but the implication is the same--even a
small shift in average global or hemispheric temperature, with its
associated changes in atmospheric circulation, rainfall patterns etc.,
can be highly disruptive to society. We have seen many examples of such
anomalies in recent decades, yet temperatures, though warm, were
nowhere near the levels that may be reached later in this century.
These include extremes in rainfall, leading to catastrophic flooding in
some areas, and droughts, exceptional wildfires and historically low
lake levels elsewhere, as well as an increase in windstorms and other
weather-related disasters. Unusual weather events are becoming less
uncommon, impacting agriculture, transportation and commercial
activity. Of course, such disasters have always occurred to some
extent, but the frequency of extremes has increased in recent years
throughout the world, leading major insurance companies to express
grave concerns about their exposure to these unprecedented risks (note
that these risks are in addition to the costs due to increased
development). Munich Re, one of the world's largest re-insurance firms
``1999 fits exactly into the long-term pattern of increasing
losses from natural catastrophes . . . insured losses came to
$22bn. This is the second highest figure ever recorded . . .
windstorms were responsible for 80% of the insured losses while
earthquakes accounted for 10%, floods 6%, and other events like
forest fires, frost, and heat waves around 4% . . . In view of
the fact that the signs of climate change and all its related
effects are becoming more and more discernible . . . if . . .
meteorological extremes like torrential rain, windstorms, and
heat waves continue to increase and the rise in sea level
accelerates, many regions of the world will be in immediate
danger . . .''
Can we be certain that future climate will involve unprecedented
risks? Some argue that processes within the climate system will act to
compensate for the effects of higher greenhouse gas levels (so-called
negative feedback effects). According to this scenario, these feedbacks
will help maintain the climatic status quo enabling us to continue to
contaminate the atmosphere ad infinitum. There is a small chance that
such critics are right, in which case it would be safe to do nothing.
But they may be completely wrong, and indeed the scientific consensus
is that they are wrong. Political decisions inevitably involve
assessing risk and weighing the consequences of action versus inaction.
Just as Congress must decide if the (perhaps small) risk of a rogue
nation launching a nuclear missile at the United States (resulting in a
catastrophe) is worth avoiding by spending large sums of money on a
space defense system, so it must weigh the potentially catastrophic
environmental and commercial consequences of future global warming
against the costs of curbing fossil fuel consumption to reduce these
risks. Scientists cannot provide Congress with a certain forecast of
the future and as research on global warming continues, our
understanding will undoubtedly change. But the picture at present is
that we are indeed living in climatically unusual times, and that the
future is likely to be even more unusual.
Tree ring data include both ring width and ring density variations.
Records are available from all continental areas (except Antarctica)
though most series are from outside the tropical regions. High latitude
and high altitude trees generally provide estimates of past
temperature; trees in dry regions generally provide estimates of past
precipitation, though even in wetter areas, records of rainfall changes
can sometimes be obtained.
Ice cores provide many records of past climate but changes in
oxygen isotopes in the ice, accumulation rate and (summer) melt
conditions are of primary interest in examining recent centuries. In
polar regions oxygen isotopes are generally considered to be an
indicator of annual temperature. Other useful climate indicators
include the fraction of a core containing `melt features' (produced by
the re-freezing of percolating surface melt water) which provides a
useful index of summer temperature conditions, and accumulation rate
changes, which indicate past snowfall amounts.
Corals provide uniquely detailed records of sea-surface
temperatures, from changes in the (temperature-dependent) oxygen
isotopes in the carbonate skeletons of the corals. In some cases,
salinity variation is the most important factor influencing isotope
content, in which case the changes reflect precipitation and runoff
from adjacent continental regions.
Varved sediments, from both lake and marine environments, are
annual layers that record past environmental conditions in the lake or
oceanic region. There are few ocean areas where varved sediments are
known to occur (generally upwelling coastal regions where there is
little oxygen in the deep waters) but varved lake sediments are found
on all continents. Providing the records are clearly annual and a
strong climatic signal can be demonstrated, these records can provide
useful data from many regions of the world.
Historical records can, potentially, provide seasonal estimates of
past climate over wide geographic regions, though at present only
European and East Asian sources have been adequately studied.
Details of how these and other paleoclimate proxies are used to
reconstruct past climates can be found in the book ``Paleoclimatology''
by R.S. Bradley (1999, Academic Press).
The Chairman. Dr. Christy, welcome.
STATEMENT OF DR. JOHN R. CHRISTY, DIRECTOR,
EARTH SYSTEM SCIENCE CENTER, UNIVERSITY OF ALABAMA
Dr. Christy. Thank you, Mr. Chairman. I am pleased to be
here testifying before this Committee.
By the way, I am from the University of Alabama in
Huntsville. We do not have football team. Ice hockey, in fact,
is our favorite sport.
Dr. Christy. Considering the varying levels of skepticism
represented on this panel, it would be apparent that I am very
likely the witness that is most skeptical, but not agnostic,
regarding our ability to predict future climate. And I hope to
demonstrate why this is so.
The universal feature of climate model projections of
global temperature changes due to greenhouse gas increases is a
rise in the temperature of the atmosphere from the surface to
about 30,000 feet.
This temperature rise itself is projected to be significant
at the surface, with increasing magnitude as one rises in the
atmosphere, which we call the troposphere.
Over the past 21-years various calculations of surface
temperature, indeed, show a rise between .45 and .65 of a
degree. This represents about half of the total rise since the
end of the 19th Century.
In the troposphere, however, various estimates, which
include satellite data that Dr. Roy Spencer of NASA and I
produced, show only a very slight warming between .09 and .18
of a degree, a rate less than one-third that observed at the
So rather than seeing a rise in temperature that increases
with altitude as climate models project, we see that in the
real world since 1979, the rise decreases substantially with
The most recent modeling efforts which attempt to explain
this disparity suggest that when some of the actual climate
processes are factored in, and I emphasize ``some,'' such as
the Mount Pinatubo eruption, the models looked like they came
close to reality.
On closer inspection of these studies, however, one finds
that the apparent agreement was achieved only by comparing
apples with oranges. The model experiments included some major
processes, but not all major processes.
When those additional processes were included, like real El
Ninos, the climate models did not produce the observed global
average vertical temperature changes. In other words, 60
percent of the atmosphere is going in a direction not predicted
And that, in my view, is a significant missing piece of the
climate puzzle that introduces considerable uncertainty of the
models' utility regarding predicting temperatures.
Now, it is certainly possible that the inability of the
climate models to predict what happened over the past 21 years
may only indicate that the climate experiences large natural
fluctuations in the vertical temperature structure.
However, this means that any attention drawn to the surface
temperature rise for the past two decades must, I repeat must,
also acknowledge the fact that 60 percent of the atmospheric
mass that was projected to warm did not.
This vertical temperature situation is a curious and
unexplained issue regarding global average temperatures. But we
do not live 30,000 feet in the atmosphere, and we do not live
in a global average. We live in a specific place, city, state,
and so on.
Local and regional projections of climate are very
difficult and challenging. An example from North Alabama that I
wanted to use here, only illustrates the difficulty in
providing regional estimates of what might happen.
A few climate models have attempted to reproduce the
temperature changes over the last 150 years, since the 19th
century. These are complex models with solar changes, carbon
dioxide increases, sulfate pollution, oceans, and so on.
They indicate that since the 1890's we in North Alabama
should have experienced a warming of about two degrees.
Observations show we have actually experienced a cooling of
over two degrees. The models may have done fairly well at the
global average surface temperature, and may have done
acceptably well in several geographic locations, but my opinion
in the southeast, is that there was false information there. I
am not hitting climate models in a critical way. I am showing
the challenge that is there on reproducing climate results on a
If in trying to reproduce the past we see such model
errors, one must assume that predicting the future would
produce similar opportunity for regional errors. I want to
encourage the Committee to be suspicious of media reports in
which weather extremes are given as proof of human-induced
Weather extremes occur somewhere all the time. For example,
you have seen recent reports perhaps about the U.S. surface
temperature data showing January through March the highest ever
in one surface temperature data set of the United States, not
The satellite data provides information for the entire
globe and show that, yes, indeed, the tropospheric temperatures
were well above average for the 48 contiguous states. However,
most of the globe experienced below average temperatures in
that massive bulk of the atmosphere.
It was our turn to be warm while in places such as the
equatorial oceans and the Sahara Desert, it was their turn to
be cool. Other climate data give us similar information.
Hurricanes have not increased. Tornadoes have not increased.
Droughts and wet spells have not statistically increased, or
Let me quickly add, there are many more people and much
more wealth in the paths of these destructive events, so losses
have increased but that is not due to climate change. Deaths in
U.S. cities are no longer correlated with high temperatures,
though deaths still increase during cold temperatures.
When looking at data such as these, especially on a
regional basis, climate change, and in particular, the human
factor of climate change, is very difficult to detect at all.
I will close with three questions and a plea. Is the
climate changing? Yes, it always has and it always will, but it
is very difficult to detect on decadal time scales.
Are climate models useful? Yes, and improving. At this
point, their utility is mostly in global average scale, yet
there are still some significant shortcomings even there.
Is that portion of climate change due to human factors
good, bad, or inconsequential? And that, no one knows, although
we do know that the plant world thrives on additional CO2
in the atmosphere.
What I do know is that we depend on data to answer these
questions. The global data network is decaying at the very time
we need it most.
If the richest country in the world could do anything, it
would be to step up efforts to monitor the present global
climate, reconstruct the past climate, assure easy and timely
access to data, and to support scientists to study the data on
which to depend such important answers.
The Chairman. Thank you very much, Dr. Christy.
[The prepared statement of Dr. Christy follows:]
Prepared Statement of Dr. John R. Christy, Director,
Earth System Science Center, University of Alabama
Mr. Chairman and Committee Members, I am pleased to accept your
invitation to offer information on climate change along with my own
assessment. I am John Christy, Professor of Atmospheric Science and
Director of the Earth System Science Center at the University of
Alabama in Huntsville.
The concentration of carbon dioxide (CO2) is increasing
in the atmosphere due primarily to the combustion of fossil fuels. It
is our great fortune (because we produce so much of it) that CO2
is not a pollutant. In simple terms, CO2 is plant food. The
green world we see around us would disappear if not for atmospheric
CO2. These plants largely evolved at a time when the
atmospheric CO2 concentration was many times what it is
today. Indeed, numerous studies indicate the present biosphere is being
invigorated by the human-induced rise of CO2. In and of
itself, therefore, the increasing concentration of CO2 does
not pose a toxic risk to the planet. It is the secondary impact of
CO2 that may present challenges to human life in the future.
It has been proposed that CO2 increases could cause climate
change of a magnitude beyond what naturally occurs that would force
costly adaptation or significant ecological stress. For example, sea
level rise and/or reduced rainfall would be two possible effects likely
to be costly to those regions so affected. Data from the past and
projections from climate models are employed to provide insight on
Climate models attempt to describe the ocean/atmospheric system
with equations which approximate the processes of nature. No model is
perfect because the system is incredibly complex. One modest goal of
model simulations is to describe and predict the evolution of the
ocean/atmospheric system in a way that is useful to discover possible
environmental hazards which lie ahead. The goal is not to achieve a
perfect forecast for every type of weather in every unique geographic
region, but to provide information on changes in large-scale features.
If in testing models for current large-scale features one finds
conflict with observations, this suggests that at least some
fundamental process, for example heat transfer, are not adequately
described in the models.
A universal feature of climate model projections of global average
temperature changes due to enhanced greenhouse gasses is a rise in the
temperature of the atmosphere from the surface to 30,000 feet. This
temperature rise itself is projected to be significant at the surface,
with increasing magnitude as one rises through this layer called the
troposphere. Most people use the term Global Warming to describe this
Over the past 21-years various calculations of surface temperature
do indeed show a rise between +0.45 and +0.65+F (0.25 and 0.36+C
depending on which estimate is used.) This represents about half of the
total surface warming since the 19th century. In the troposphere,
however, the values, which include the satellite data Dr. Roy Spencer
of NASA and I produce, show only a very slight warming between +0.09
and +0.18+F (+0.05 and +0.10+C)--a rate less than a third that observed
at the surface. So, rather than seeing a warming that increases with
altitude as climate models project, we see that in the real world the
warming substantially decreases with altitude.
It is critically important in my view to correctly model
tropospheric temperature changes because this is where much of the
global atmospheric heat is moved about and eventually expelled to
space. This layer also has a strong influence on surface temperature
through radiation processes. It is conceivable that a model which
retains too much heat in the troposphere, may also retain too much at
The most recent modeling attempts which seek to reconcile this
disparity suggest that when some of the actual climate processes are
factored in, the models come very close to reality. These processes are
events such as the Mt. Pinatubo eruption and slow changes such as ozone
On closer inspection of these studies, however, one finds that the
apparent agreement was achieved only by comparing apples with oranges.
The model experiments included some major processes, but not all major
processes. When those additional processes are also factored in, such
as real El Ninos, the climate models do not produce the observed global
average vertical temperature changes observed since 1979. In other
words, the temperature of 60% of the atmosphere appears to be going in
a direction not predicted by models. That, in my view, is a significant
missing piece of the climate puzzle which introduces considerable
uncertainty about a model's predictive utility.
It is certainly possible that the inability of the present
generation of climate models to reproduce the reality of the past 21
years may only reflect the fact that the climate experiences large
natural variations in the vertical temperature structure over such time
periods. By recognizing this however, the implication is that any
attention drawn to the surface temperature rise over the past two
decades must also acknowledge the fact that 60% of the atmospheric mass
has not similarly warmed.
This disparity between observations and model results is a curious
and unexplained issue regarding the global average vertical temperature
structure. But we do not live 30,000 feet in the atmosphere, and we do
not live in a global average surface temperature. We live in specific
places, cities, states and regions. Local and regional projections of
surface climate are very difficult and challenging. An example from
Alabama's past is useful here only to illustrate the difficulty of
providing local predictions with a high level of confidence.
A few of the present set of climate models have attempted to
reproduce the distribution of actual surface temperatures since the
19th century. These complex models incorporate solar changes,
increasing carbon dioxide, sulfate pollution and so on. They indicate
that since the 1890's we in North Alabama should have experienced a
warming of about 2+F (1+C). The truth is that we have actually
experienced a cooling of over 2+F (1+C).\1\ The model may have done
fairly well in the global average, and may have done acceptably well in
many geographic locations, but in my opinion it provided false
information for those of us in the Southeast. If in trying to reproduce
the past we see such model errors, one must assume that predicting the
future would produce similar opportunities for errors on a regional
\1\ Data have been adjusted for all station moves, time of
observation biases and instrument changes.
Weather Extremes and Climate Change
I want to encourage the Committee to be suspicious of media reports
in which weather extremes are given as proof of human-induced climate
change. Weather extremes occur somewhere all the time. For example, you
may have seen a recent report based on one version of the U.S. surface
temperature data stating that January through March of this year was
the hottest ever recorded. The satellite data provide information for
the entire globe and show that indeed tropospheric temperatures were
much above average over the lower 48 states. However, most of the globe
experienced below average temperatures in that massive bulk of the
troposphere. It was our turn to be warm while in places such as the
equatorial oceans and the Sahara Desert it was their turn to be cold.
Has hot weather occurred before in the US? All time record high
temperatures by states begin in 1888. Only eleven of the states have
uniquely seen record highs since 1950 (35 occurred prior to 1950, 4
states had records occurring both before and after 1950.) Hot weather
happens. Similar findings appear from an examination of destructive
weather events. The intensity and frequency of hurricanes have not
increased. The intensity and frequency of tornadoes have not increased.
(Let me quickly add that we now have more people and much more wealth
in the paths of these destructive events so that the losses have
certainly risen, but that is not due to climate change.) Droughts and
wet spells have not statistically increased or decreased. Last summer's
drought in the Northeast was remarkable in the sense that for the
country as a whole, the typical percentage area covered by drought was
below average. Deaths in U.S. cities are no longer correlated with high
temperatures, though deaths still increase during cold temperatures.
When considering information such as indicated above, one finds it
difficult to conclude the climate change is occurring in the U.S. and
that it is exceedingly difficult to conclude that part of that change
might have been caused by human factors.
In the past 100 years, sea level has risen 6 in. 4 in.
(15 cm 10 cm) and is apparently not accelerating. Sea
level also rose in the 17th and 18th centuries, obviously due to
natural causes, but not as much. One of my duties in the office of the
State Climatologist is to inform developers and industries of the
potential climate risks and rewards in Alabama. I am very frank in
pointing out the dangers of beach front property along the Gulf Coast.
A sea level rise of 6 in. over 100 years, or even 50 years is minuscule
compared with the storm surge of a powerful hurricane like Fredrick or
Camille. Coastal areas threatened today will be threatened in the
future. The sea level rise, if it continues, will be very slow and thus
give decades of opportunity for adaptation, if one is able to survive
I will close with three questions and a plea.
Is the climate changing? Yes, it always has and it always will, but
it is very difficult to detect on decadal time scales or on regional
Are climate models useful? Yes, and improving. At this point, their
utility is mostly related to global averages, though shortcomings are
Is that portion of climate change due to human factors good, bad or
inconsequential? No one knows (although the plant world thrives on
increases in carbon dioxide because CO2 is plant food.)
What we do know is that we depend on data to answer these
questions. The global data network is decaying at the very time we need
it most. If the richest country in the world could do something, it
would be to lead out in monitoring the present climate, in
reconstructing the past climate, in assuring easy and timely access to
the data . . . and in supporting scientists to study the data on which
depend such important answers.
The Chairman. Dr. Mahlman, is that the proper
Dr. Mahlman. Yes, it is.
The Chairman. Welcome, Doctor. Would you pull the
microphone over? Thank you.
STATEMENT OF DR. JERRY MAHLMAN, DIRECTOR, GEOPHYSICAL FLUID
DYNAMICS LABORATORY, NATIONAL OCEANIC AND ATMOSPHERIC
Dr. Mahlman. Thank you, Mr. Chairman. We have long known
that buildups of atmospheric carbon dioxide and other gases
have the potential to warm earth's climate, through the so-
called greenhouse effect.
Today, I will discuss the modeling of projections of
climate changes due to these increases in greenhouse gases for
the time around the middle of this 21st Century. Because I
speak with credentials as a physical scientist, I do not offer
personal opinions on what society should do about these
projected climate changes.
Societal actions to greenhouse warming involve value and
policy judgments that are beyond the realm of climate science.
At the onset, please recognize that a major international
effort to assess climate warming was completed in 1996. This is
the IPCC assessment that Dr. Lane referred to earlier.
This was the most widely accepted assessment ever on
climate change. The 2001 climate assessment will be completed
soon. I expect only small changes in its major conclusions,
mainly concerning some very important increases in scientific
confidence over the last 5 years.
I strongly recommend your use of these IPCC assessments as
a foundation for your own evaluations. I also recommend their
use as a point of departure for evaluating the credibility of
opinions that disagree with the IPCC assessments. IPCC is not
an infallible system, in that sciences is always self
corrective, but opinions that disagree with them have the
burden to make sense.
My information I present today is derived from the
strengths and weaknesses of climate models, the strengths and
weaknesses of climate theory, and the strengths and weaknesses
of widespread observations of the climate system.
Climate models have improved in their ability to simulate
the climate and its natural variations. Unfortunately,
important uncertainties due to deficiencies in our scientific
understanding and in our computing power still remain.
Nevertheless, significant progress is expected over the next
However, let me say at the onset, none of the uncertainties
that I discuss today can make current concerns about greenhouse
warming go away. This problem is very real, and is guaranteed
to be with us for a very long time.
I will give my evaluation of current model projections of
climate change for the middle of the next century by my setting
of simple betting odds. By ``virtually certain,'' a phrase used
earlier by Senator Kerry, I mean, that there is no plausible
alternative that we know of. In effect, the bet would be off
``Very probable'' means that I estimate a nine out of ten
chance that this will happen within the range projected.
``Probable'' implies that I am setting the odds at about a two
out of three chance, while uncertain means a plausible effect,
but which lacks appropriate evidence. I will give examples of
all of these. So essentially, I set the betting odds; you
choose your bet.
My analysis is presented in decreasing levels of scientific
confidence. Human-caused increasing greenhouse gases in the
atmosphere is virtually certain. There is no remaining real
doubt that increasing greenhouse gases are due to human
Radiative effects of increased greenhouse gases is
virtually certain. Greenhouse gases absorb and reradiate
infrared radiation, the heat radiation that leaves the planet
all the time, that makes it cool off at night. Independent of
other factors, this acts to produce an increased heating on the
A doubling of atmospheric carbon dioxide expected,
virtually certain. Atmospheric carbon dioxide amounts are now
expected to at least double over pre-industrial levels in this
century. Currently, emission growth is on track to quadruple
carbon dioxide levels.
Long time to draw down excess carbon dioxide, virtually
certain. We know that it takes decades to centuries to produce
a large buildup of greenhouse gases. Much less appreciated is
that a return to normal from high carbon dioxide levels in the
atmosphere would require many additional centuries, perhaps
more than 1,000 years.
Global surface warming over the past century, virtually
certain. The measured 20th century warming in the surface
temperature records of over one degree Fahrenheit is
undoubtedly real. Its cause is very probably due mostly to
added greenhouse gases. No other hypothesis today is nearly as
Future global-mean surface warming, very probable. Assuming
business as usual for the middle of the next century, global-
mean surface warming is estimated to be in the range of two to
six degrees Fahrenheit, with continued increases for the rest
of the century. The largest uncertainty is due to the effects
Increased summertime heat index, very probable. In warm
moist subtropical climates, such as Washington, D.C., the
summertime heat index effect is expected to magnify the warming
impact felt by humans by an additional 50 percent.
Rise in global sea level, very probable. A further rise of
four to twelve inches in global mean sea level by the year 2050
is estimated due simply to the thermal expansion of warmer sea
water. As the water warms, it occupies more volume. This does
not include the effects of possible melting of Greenland ice.
Continued sea level rise is expected for many centuries,
probably to much higher levels.
Disappearance over the last 50 years of Arctic sea ice,
very probably, due to human activities. There is some
uncertainty about how much humans have had to do with that, but
it is pretty well conceded that the models are now calculating
Summer mid-continental dryness, probable. Model studies
project a marked decrease in soil moisture over summer mid-
latitude continents. This projection remains sensitive to model
assumptions, thus, I give it a two out of three bet.
Increased tropical storm intensities, probable. A warmer,
wetter atmosphere will likely lead to increased intensities of
tropical storms such as hurricanes, and substantial increases
in their precipitation rates.
We still know little about changes in the number of
hurricanes. When people tell you there will be more hurricanes,
we do not know where those kind of statements come from. So,
when people say we are not finding increased numbers of
hurricanes, I do not understand that either.
Increased numbers of weather disturbances, uncertain.
Although many speak of more large-scale storms, such as
northeasters, and so forth, there is no solid evidence for
this, in either models or theory.
Global and regional details for the next 25 years,
uncertain. The predicted warming, up to now, is not yet large
compared to natural climate fluctuations. We can find it in the
data, but it does not yet fully dominate. On these shorter time
scales, the natural fluctuations can artificially reduce or
enhance apparent measured greenhouse warming signals,
especially so on regional scales.
Endorsing Dr. Christy's point, but raising the bet,
variations on decadal scales at a particular region can be due
to completely natural effects, California and Southwest United
States are particularly vulnerable to these natural
Even though these uncertainties are daunting, important
advances have already been achieved in observing,
understanding, and modeling the climate. Today's models can
simulate many aspects of climate and its changes.
Although major progress has been made, much more needs to
be learned. More efforts are needed worldwide to provide a
long-term climate measuring system that is really designed to
do the job.
Focused research into climate processes must be continued.
Theories must be formulated and re-evaluated in the light of
newer data. Climate modeling efforts must receive resources
that are in balance with the broader scientific programs.
In my view, the U.S. Global Change Research Program has
already made important progress on these fronts. However,
patient and sustained efforts will be required in the years
I endorse Dr. Lane's balanced presentation of this vital
interagency effort under the U.S. Global Change Research
Program. Through long-term research and measurements,
uncertainties will decrease, and confidence for projections of
climate change will increase.
In summary, the greenhouse warming effect is quite real.
The state of the science is strong, but important uncertainties
do remain. Finally, it is a virtually certain bet that this
problem will refuse to go away no matter what is said or done
about it over the next 5 to 10 years.
Thank you, Mr. Chairman.
Prepared Statement of Dr. Jerry Mahlman, Director, Geophysical Fluid
Dynamics Laboratory, National Oceanic and Atmospheric Administration
My name is Jerry Mahlman. I am the Director of the Geophysical
Fluid Dynamics Laboratory of NOAA. For over thirty years our Laboratory
has been a world leader in modeling the earth's climate. I will
evaluate scientific projections of climate change as well as their
We have long known that buildups of atmospheric carbon dioxide and
other gases have the potential to warm earth's climate, through the so-
called ``greenhouse'' effect. Today, I will discuss modeling the
projections of climate changes due to these increasing greenhouse gases
for a time around the middle of the century.
Because I speak with credentials as a physical scientist, I do not
offer personal opinions on what society should do about these projected
climate changes. Societal actions in response to greenhouse warming
involve value and policy judgements that are beyond the realm of
At the onset, please recognize that a major international effort to
assess climate warming was completed in 1996. This is ``The
Intergovernmental Panel on Climate Change Assessment'' (IPCC). The IPCC
was established in 1988 by the United Nations Environment Programme and
the World Meteorological Organization to assess the available
information on climate change and its environmental and economic
impacts. This was the most widely accepted assessment ever on climate
change. The 2001 IPCC Assessment will be completed soon. I expect only
small changes in its major conclusions, mainly concerning some
important increases in scientific confidence.
I strongly recommend your use of the IPCC assessments as a
foundation for your own evaluations. I also recommend their use as a
point of departure for evaluating the credibility of opinions that
disagree with them.
My information is derived from the strengths and weaknesses of
climate models, climate theory, and widespread observations of the
climate system. Climate models have improved in their ability to
simulate the climate and its natural variability. Unfortunately,
important uncertainties remain due to deficiencies in our scientific
understanding and in computer power. However, significant progress is
expected over the next 10 years.
However, let me say at the outset: None of the uncertainties I will
discuss can make current concerns about greenhouse warming go away.
This problem is very real and will be with us for a very long time.
I will give my evaluation of current model predictions of climate
change in the middle of the next century by setting simple ``betting
odds.'' By ``Virtually Certain,'' I mean that there is no plausible
alternative; in effect, the bet is off the books. ``Very Probable''
means I estimate about a 9 out of 10 chance that this will happen
within the range projected; ``Probable'' implies about a 2 out of 3
chance. ``Uncertain'' means a plausible effect, but which lacks
appropriate evidence. Essentially, I set the odds; you choose your bet.
My analysis is presented in decreasing levels of confidence.
Human-Caused Increasing Greenhouse Gases (virtually certain)
There is no remaining doubt that increasing greenhouse gases are
due to human activities.
Radiative Effect of Increased Greenhouse Gases (virtually certain)
Greenhouse gases absorb and reradiate infrared radiation.
Independent of other factors, this property acts to produce an
increased heating effect on the planet.
A Doubling of Carbon Dioxide Expected (virtually certain)
Atmospheric carbon dioxide amounts are expected to double over pre-
industrial levels in this century. Current emissions growth is on track
to quadruple atmospheric carbon dioxide.
Long Time to Draw Down Excess Carbon Dioxide (virtually certain)
We know that it takes decades to centuries to produce a large
buildup of greenhouse gases. Much less appreciated is that a ``return
to normal'' from high carbon dioxide levels would require many
Global Surface Warming Over the Past Century (virtually certain)
The measured 20th century warming in the surface temperature
records of over one degree fahrenheit is undoubtedly real. Its cause is
very probably due mostly to added greenhouse gases. No other hypothesis
is nearly as credible.
Future Global-Mean Surface Warming (very probable)
For the middle of the next century, global-mean surface warming is
estimated to be in the range of 2 to 6+ fahrenheit, with continued
increases for the rest of the century. The largest uncertainty is due
to the effects of clouds.
Increased Summertime Heat Index (very probable)
In warm, moist subtropical climates the summertime heat index
effect is expected to magnify the warming impact felt by humans by an
Rise in Global Mean Sea Level (very probable)
A further rise of 4-12 inches in mean sea level by the year 2050 is
estimated due to thermal expansion of warmer sea water. Continued sea
level rise is expected for many centuries, probably to much higher
Summer Mid-Continental Dryness and Warming (probable)
Model studies predict a marked decrease of soil moisture over
summer mid-latitude continents. This projection remains sensitive to
Increased Tropical Storm Intensities (probable)
A warmer, wetter atmosphere will likely lead to increased
intensities of tropical storms, such as hurricanes. We still know
little about changes in the number of hurricanes.
Increased Numbers of Weather Disturbances (uncertain)
Although many speak of more large-scale storms, there is still no
solid evidence for this.
Global and Regional Details of the Next 25 Years (uncertain)
The predicted warming up to now is not yet large compared to
natural climate fluctuations. On these shorter time scales, the natural
fluctuations can artificially reduce or enhance apparent measured
greenhouse warming signals, especially so on regional scales.
Even though these uncertainties are daunting, important advances
have already been achieved in observing, understanding, and modeling
the climate. Today's models can simulate many aspects of climate and
its changes. Although major progress has been made, much more needs to
be learned. More efforts are needed world-wide to provide a long-term
climate measuring system. Focussed research into climate processes must
be continued. Theories must be formulated and re-evaluated in the light
of newer data. Climate modeling efforts must receive resources that are
in balance with the broader scientific programs.
The U.S. Global Change Research Program has already made important
progress on these fronts. However, patient, sustained efforts will be
required in the years ahead.
Through long-term research and measurements, uncertainties will
decrease and confidence for predicting climate changes will increase.
In summary, the greenhouse warming effect is quite real. The state
of the science is strong, but important uncertainties remain. Finally,
it is a ``virtually certain'' bet that this problem will refuse to go
away, no matter what is said or done about it over the next five years.
Thank you, Mr. Chairman. That concludes my testimony.
The Chairman. Thank you, Dr. Mahlman.
Dr. Trenberth, welcome.
STATEMENT OF DR. KEVIN E. TRENBERTH, DIRECTOR,
CLIMATE ANALYSIS SECTION, NATIONAL CENTER FOR
Dr. Trenberth. Thank you, Senator.
I recently served on the National Research Council Panel
that produced the report that has been referred to, this report
here on reconciling observations of global temperature change.
And I was asked in my comments to especially address the
findings of this particular Committee.
The first thing I would say is that the mere need for this
report highlights the fact that we do not have a global climate
observing system. Most of the observations that are used for
climate purposes are made for weather or aviation purposes. The
observations are made for purposes other than for climate.
Heroic efforts are, therefore, needed, it turns out, to
reconstruct exactly what has happened even in the instrumental
period, let alone what has happened in the last 1,000 years.
What we do conclude in this report is that in the past 20
years, global mean surface temperatures have been rising at a
rate as large as any that has been observed within the
The surface temperatures have increased. A central number I
would put on it is about 1.3 degrees Fahrenheit over the past
century. 1998 is the warmest year, as has been mentioned
several times, and the 1990's is the warmest decade. And
melting glaciers and rising sea level provides additional
support that these effects are real.
Now this rapid warming at the earth's surface is in
contrast, as John Christy has mentioned, to the trend in the
satellite record, which only began though in 1979. Now the
satellite record measures the temperature of about the lowest
five miles of the atmosphere. It is not measuring the same
thing as the temperature of the surface. It is an indirect
measurement, and it is inferred from radiation that is emitted
by oxygen molecules and it is sampled by a microwave sound
So these are measurements in the microwave frequencies, and
these measurements are made aboard polar orbiting satellites.
Before I go on to summarize some aspects of the temperature
record, I would emphasize a point which has been made by
others: Temperature changes are only part of the total picture,
and that the global mean temperature, I think of more as an
indicator that something extraordinary is happening now. It is
a little bit like the canary in a cage in a coal mine. It shows
that something extraordinary is happening, but it has very
little practical significance locally. And other changes such
as rainfall and droughts, and fires such as in your own state,
Senator, are probably of much more practical significance.
Now in my written testimony, I summarize firstly, the
surface temperature record; second, the radiosonde balloon-
borne temperature record which measures the temperatures above
the surface of the earth; and third, the satellite record. And
for each of these, I discuss the nature of the measurements,
their coverage in space and time, their biases, their
advantages and disadvantages, and they all have some, and a
brief overall assessment of them. And I then deal with the
issues of reconciling them, and I do not have time to go
through all of those things here.
What I will say is that all three records have been
improved and developed in recent years, in particular several
corrections have been made to the satellite record, for
example, through the effects of the systematic orbital decay of
each satellite--and this has improved the level of agreement
among the records.
Now using the radiosonde record, we can estimate the
temperatures of the layer seen by the satellite. And this shows
quite good agreement during the overlap period after 1979. And
therefore, we can use the radiosonde record to extend that
record back in time to about 1964 quite reliably.
And when we do that, although we find that the temperature
trends in the satellite record from 1979 to 1999 are quite
small, the longer term trends are somewhat more in agreement
with what we see at the surface.
I would emphasize that the trends in the satellite record,
after 1979, are less than those at the surface, primarily
because they are measuring different things. A reasonable
interpretation, I think, of the overall record is that global
The Chairman. What different things are they measuring?
Dr. Trenberth. The satellite record is measuring the layer
in the lowest five miles or so of the atmosphere, and it is
influenced by a number of things that have much less influence
at the surface. I was just coming to that point, in fact.
The Chairman. I am sorry.
Dr. Trenberth. I think a reasonable interpretation of the
overall record is that the global warming from increased
greenhouse gases is producing the rising temperatures that we
are seeing at the surface, and now those rises are above and
beyond those arising from natural variability.
The main reasons the tropospheric temperatures are not
keeping pace are because of stratospheric ozone depletion which
has a much greater effect on what is happening, especially in
the lower stratosphere and the upper part of the troposphere
than it does on the surface. And also, changes in cloud cover,
which have an effect on maximum versus minimum temperatures. We
know that minimum temperatures are rising much faster than
maximum temperatures, for instance. So changes in cloud
coverage which may or may not be associated with other
pollution in the atmosphere (effects other than climate
change), may also be due to climate change itself. These are
probably the two biggest effects that are causing the
Therefore, what we do see is that the larger surface
temperature increases are occurring over land and at night
time, somewhat less during the day, and somewhat less over the
The panel concluded that the records are probably
reasonably consistent with each other once all of the forcing
factors are taken into account. Now this goes beyond the models
themselves, as it also is the forcing factors such as the
depletion of the ozone layer and its vertical profile which are
not known very well. And that is one of the uncertainties that
Once all of those factors are taken into account, we
believe the records are consistent with one another. In other
words, the bigger increase at the surface than in the
troposphere is real. And accordingly, the recent warming at the
surface is undoubtedly real. It is substantially greater than
the average rate during the 20th century, and it is in no way
invalidated by the satellite record.
In my closing remarks, I would like to make a comment about
global warming in general. I think the term itself is often
misused, and it really should refer to the increased heating
that is occurring because of the changes in composition of the
Some of that heat goes into raising temperature, but in
actual fact, most of it goes into evaporating moisture at the
surface of the earth. Most of the earth is covered by ocean, 70
percent of the surface, and most of the heat is, in fact, going
into evaporating moisture.
Over land that is true also as long as there is moisture
around, but when things dry out, as happens in a drought, then
all of the heat tends to go into raising temperature, and that
is when we get the greatest heat waves.
In the United States, there has been a general increase in
precipitation and this tends to mute any changes in temperature
because more heat is going then into evaporating moisture. As
an example of this, if it has been raining and the sun comes
out, the first thing that happens is that all of the puddles
dry up. The heat goes into evaporating the moisture, not
So it is very important to consider changes in temperature
along with changes in rainfall, and just focusing on
temperature does not give you a complete picture or an adequate
understanding of what exactly is going on.
So I would emphasize that it is much more than changes in
temperature. Changes in precipitation, changes in moisture can
act as a swamp cooler to air condition the planet, and in fact,
do so. And we should also be concerned about changes in storms
and changes in severe weather events.
Thank you for the opportunity to testify.
The Chairman. Thank you very much.
[The prepared statement of Dr. Trenberth follows:]
Prepared Statement of Dr. Kevin E. Trenberth, Director, Climate
Analysis Section, National Center for Atmospheric Research
CLIMATE CHANGE AND TEMPERATURES
My name is Kevin Trenberth. I am the Head of the Climate Analysis
Section at NCAR, the National Center for Atmospheric Research. I am
especially interested in global-scale climate dynamics; the
observations, processes and modeling of climate changes from
interannual to centennial time scales. I have served on many national
and international committees including National Research Council/
National Academy of Science committees, panels and/or boards. I
recently served on the National Research Council Panel on ``Reconciling
observations of global temperature change,'' whose report was published
in January 2000. I co-chaired the international CLIVAR Scientific
Steering Group of the World Climate Research Programme (WCRP) from 1996
to 1999 and I remain a member of that group as well as the Joint
Scientific Committee that oversees the WCRP as a whole. CLIVAR is short
for Climate Variability and Predictability and it deals with
variability from El Nino to global warming. I have been involved in the
global warming debate and I am extensively involved in the
Intergovernmental Panel on Climate Change (IPCC) scientific assessment
activity as a lead author of individual chapters, the Technical Summary
and Policy Makers Summary of Working Group I.
During the past 20 years, global mean surface temperatures have
been rising at a rate as large as any that has been observed within the
historical record. Such rapid warming at the Earth's surface is in
contrast to the trend in the global-mean temperature of the lowest 8
kilometers of the atmosphere (within that portion of the atmosphere
referred to as the troposphere) as inferred from measurements of
radiation emitted by oxygen molecules (a proxy for tropospheric
temperature) sampled by the microwave sounding unit (MSU) carried
aboard the NOAA polar-orbiting satellites; see Fig. 1 for the vertical
structure of the atmosphere. I will summarize here the state of
knowledge with regard to observed climate change, and especially the
issues of the changes in temperatures as seen by the synthesis of
observations taken at the Earth's surface versus those measured by
Fig. 1. The typical structure of temperature with height is shown. The
lower atmosphere is the troposphere and the lowest 8 km or so of that
is the region measured by the MSU-LT. The stratosphere contains the
ozone layer and is separated from the troposphere by the tropopause
which varies in height from about 10 km in the extratropics to 16 km in
Observed climate change
It is important to appreciate that temperature changes are only a
part of the total picture. Global warming refers to the increased
heating of the Earth arising from well documented increases in
greenhouse gases such as Carbon Dioxide. At the surface, some of that
heat goes into raising temperatures, but most of it goes into
evaporating moisture. This is especially true as long as the surface is
wet, as it always is over the 70% of the globe covered by oceans. After
rainfalls, in bright sunshine, it is only following the drying up of
surface puddles that temperatures are apt to rise. Accordingly, the
strongest heat waves occur in association with droughts because then
there is no surface moisture to act as a ``swamp cooler,'' and droughts
are apt to become more intense with global warming. Meanwhile the
increases in atmospheric moisture fuel more vigorous storms. Changes in
extremes of climate will be much greater than changes in the mean. It
also means that temperature increases are likely to be muted in places
where precipitation has increased, as is generally the case for most of
the United States. Changes in cloud cover, storm tracks, winds, and so
forth further complicate the picture. The very nature of the
atmospheric circulation, in which large-scale waves occur, also
guarantees that some regions will warm more than others and some
regions may cool even as the planet as a whole warms. These comments
highlight the need to examine several factors, including precipitation,
when developing an understanding of temperature changes.
The surface temperature record is made up mostly from measurements
by thermometers that track surface air temperature over land and ocean,
as well as sea surface temperatures (SSTs) over the oceans. In recent
years satellite infrared measurements have helped determine patterns of
SSTs. The coverage increases over time after about 1850; it was quite
poor in the 1800s and is best after the 1950s. It is only truly global
after 1982 with the help of satellite measurements. It is generally
poor over the southern oceans and there were almost no data over
Antarctica prior to the IGY (1957). Changing biases confound the
climate record. These arise from changes in observing practices
(thermometer types, their exposure, the time of measurement etc.), and
changes in land use practices. The urban heat island is the best known
latter effect and arises because of the concrete jungle in cities which
retains heat at night and causes rapid runoff of rain.
The advantages of the surface record are its length, well over 100
years, the many independent measurements, several independent analyses,
and its robustness to the many cross checks, such as Northern versus
Southern Hemisphere, urban versus rural, and land-based versus marine
measurements. The disadvantages are the mostly less than global
coverage, and coverage changes with time. An overall assessment is that
the trends are robust, but may be slightly over-estimated owing to
under-representation of the southern oceans and Antarctica.
Fig. 2. The average annual mean global temperature expressed as the
departure from the 1961-90 average of 14C, called anomalies. From U.K.
Met. Office and University of East Anglia.
Surface temperatures (Fig. 2) have increased by 0.7+C (1.3+F) over
the past century. The increase is not steady but occurs mainly from the
1910s to 1940 and the 1970s to the present. 1998 is the warmest year on
record and the 1990s are the warmest decade in both hemispheres, on
land and on the ocean. Melting glaciers and rising sea level provide
strong supporting evidence. However, over land nighttime temperatures
are rising faster then daytime temperatures, by almost 0.1+C per decade
since 1950, apparently largely because of increases in low cloud cover.
The surface temperature record has been extended back in time by
use of proxy indicators that are known to be sensitive to temperatures,
such as from tree rings, corals, and ice cores. A recent synthesis of
these provides further context for the recent trends and shows that the
last decade is likely to have been the warmest in the past 1000 years.
Measurements of temperatures in the atmosphere above the surface
became routine beginning in the mid-1940s through use of balloon-borne
instrument packages (radiosondes) that transmit thermister-measured
temperatures back to ground along with pressure and humidity. Their
purpose has been mainly for aviation use and weather forecasting. The
observations are at best twice daily and while spatial coverage
improved in the IGY, it is marginal for large-scale estimates before
about 1964. The biases are the many changes in instrumentation and
observing methods, often with poor documentation of these changes.
There are known biases in some brands, and a common problem has been
improper shading from the sun and adequate ventilation. [Recall the
temperature is that of the air, which must therefore be circulated past
the sensor, and the sensor must be protected from direct solar
radiation.] The advantages are the very high vertical resolution of the
measurements, the use of new independent instruments for each sounding
and the diversity of instruments. Also, there have been a few
independent analyses. The disadvantages are the diversity of
instruments that are inadequately calibrated for climate purposes,
their often unknown changes with time, and the spotty non-global
coverage. An assessment suggests that the tropospheric record is
reasonably well known after 1964 in the Northern Hemisphere
extratropics, but that coverage is inadequate elsewhere.
Satellite temperature measurements
The satellite record is made up of MSU measurements of microwave
radiation emitted by the atmosphere which are proportional to
temperature. The coverage began in December 1978 twice or four times a
day from one or two satellites, and is global. The emissions represent
a very broad layer in the vertical, and so a retrieval is used to
obtain the temperature closer to the surface. This is the commonly used
satellite record but it still represents the lowest 8 km or so of the
atmosphere, so it is physically a very different quantity than the
The observation times vary with satellite and orbit drift. Biases
arise from the use of 9 different satellites and instruments, orbital
decay affects the retrieval, east-west drift of the satellite affects
the time of day of observation, and there are instrument calibration
and solar heating of the platform effects. Another significant factor
is that the retrieval amplifies the noise by a factor of 3 to 5. Other
disadvantages are some contaminating effects from the surface,
especially over land, contamination by precipitation-sized ice, the
difficulty of obtaining continuity across satellites, the shortness of
the record, and one group has processed the data. The advantages are
the global fairly uniform coverage, the long-term stability of
microwave radiation emissions from oxygen, the biases may be well
determined if there is adequate satellite overlap, and there are many
observations which can be used to reduce random noise. The assessment
is that this record is excellent for spatial coverage and determining
interannual variations but suspect for trends.
Reconciling temperature records
All three records have been improved and developed in recent years.
In particular several corrections have been made to the satellite
record (e.g., for orbital decay), and these have improved the
agreement. Using the radiosonde record to estimate the temperatures of
the layer seen by satellite shows very good agreement, so that the
radiosonde record can be used to extend the satellite record back to
about 1964 (Fig. 3). While tropospheric temperature trends from 1979 to
1999 are small, longer term trends are more clearly positive and closer
to those at the surface.
It is evident that the trends in the satellite record are
distinctly less than those in the surface record after 1979, and this
arises primarily because they are measuring quite different things. The
differences come from the vertical structure of the temperature changes
with time, which are complicated by features, such as temperature
inversions, in which the surface is disconnected from the atmosphere
aloft. Low level inversions trap pollutants near the surface and are
common over extratropical continents in winter, as well as throughout
much of the tropics and subtropics. The physical forcing factors
believed to be involved in causing differences in trends include (1)
stratospheric ozone depletion which preferentially cools the satellite
record; (2) episodic volcanic eruptions which cool the MSU more; (3)
increases in greenhouse gases which warms MSU more; (4) changes in
visible pollution (aerosols) which have complex regional effects that
are not well known in vertical structure; (5) solar variations which
are fairly small in this interval.
Other physical factors include (1) El Nino and other natural
variability which seems to produce a larger MSU response than at the
surface by about 30 to 40%; (2) day-night differences which relate to
maximum versus minimum temperature trends; and (3) land-ocean
differences. The much greater increases in minimum temperature, related
to increasing cloud cover, occur through a shallow layer and are not
seen as much by satellite as maximum temperature changes which are
distributed throughout the atmosphere by convection. The extent to
which the changes in cloud cover arise from changes in atmospheric
pollution or are a response to climate change is quite uncertain. Also
ocean surface temperatures are muted, land temperature changes are much
larger, and these differences are paramount at the surface but less
evident in the troposphere where winds are much stronger.
Not all of these effects have been included in models that deal
with global warming or future climate change projections, but more
sophisticated climate model simulations are expected in which best
estimates of all the forcings will be included. Further improvements
are also likely in the observational records of all three types.
However, it is believed that the records are reasonably physically
consistent with each other once all the forcing factors are taken into
account. Accordingly, the recent warming at the surface is undoubtedly
real, substantially greater than the average rate during the 20th
century, and is in no way invalidated by the satellite record.
A reasonable interpretation of the observational record is that
global warming from increased greenhouse gases is resulting in global
temperatures that are now above and beyond those arising from natural
variability. The main reasons tropospheric temperatures are not keeping
pace are because of stratospheric ozone depletion and increases in
cloud cover. Consequently larger surface temperature increases occur
over land and at nighttime. While observationally uncertain globally,
although with strong evidence over the United States, increases in
surface drying, atmospheric moisture amounts and precipitation rates
are expected as part of an increase in the hydrological cycle. This
increases risk of floods, droughts and associated fires; these are all
extremes which are very costly to the environment and to society.
Fig. 3. Global mean seasonal temperature anomalies from the MSU-LT
after 1979, the equivalent from radiosondes, and the surface from 1958
The Chairman. Dr. Watson.
STATEMENT OF DR. ROBERT WATSON, CHAIRMAN, INTERGOVERNMENTAL
PANEL ON CLIMATE CHANGE
Dr. Watson. Thank you, Senator. It is a pleasure to be here
today to testify on the issue of climate change. I am
testifying in my capacity as the Chairman of the
Intergovernmental Panel on Climate Change.
The IPCC conducts peer reviewed, comprehensive assessments
of the climate system every 5 years, and periodic technical
papers, special reports, and methodological studies as needed.
These assessments provide the scientific and technical
basis for the international negotiations. The IPCC assessments
involve experts from all relevant disciplines, all stakeholder
groups and from around the world.
The second IPCC assessment report was prepared and peer-
reviewed by over 2,000 experts from over 100 countries.
During the last year, the IPCC has published four special
reports, one on aviation and the global atmosphere; one on
technology transfer; one on emissions scenarios; and the one
that I personally chaired and finished last week on land-use,
land-use change and forestry.
We are in the middle of preparing and peer-reviewing the
third assessment report, which will be finished early next
There is no doubt that human-induced climate change is one
of the most important environmental issues facing society
worldwide. Climate change is inevitable. It is only a question
of how much, when and where.
Human activities have significantly changed the composition
of the Earth's atmosphere during the last 150 years. The
atmospheric abundance of carbon dioxides increased about 30
percent, largely due to the combustion of fossil fuels and
changes in land-use, primarily--primarily deforestation in the
The Earth's surface temperature warmed 0.4 to 0.8 degrees
centigrade over the last 100 years. The last two decades are
the warmest of the last century. And the 12 warmest years of
the last century have all occurred since 1983. And this century
is clearly the warmest century in the last 1,000 years.
The spacial and temporal patterns of precipitation are
changing. There have been observed increases in precipitation
in the mid- and high-latitude and decreases in the sub-tropics.
And there has been an increase in heavy precipitation
events and a decrease in light precipitation events, at least
in the United States.
Many parts of the world have suffered major heat waves,
floods and droughts during the last few years, leading to
significant economic losses and loss of life.
While individual events cannot be directly linked to human-
induced climate change, the frequency and magnitude of these
types of events are expected to increase in a warmer world.
Glaciers are retreating worldwide. Sea level has increased
10 to 20 centimeters in the last 100 years. And Arctic ice is
thinning. The observed changes in the Earth's climate cannot be
explained by natural phenomena alone. And the scientific
evidence, observations and models suggest a discernible human
The recent projections of future emissions of greenhouse
gases and sulfur dioxide suggest that in the absence of global
climate policies, the atmospheric concentrations of greenhouse
gases will increase substantially over the next 100 years,
while the emissions of sulfur dioxide will increase initially
for a decade or two, and then decrease significantly because of
the concern of acid deposition.
Temperatures are projected to increase from about one to
five degrees Centigrade, two to nine degrees Fahrenheit,
between now and 2100. Why is this number that I am showing
larger than the previous witnesses? And that is because the new
emissions scenarios from the IPCC suggest very low sulfur
dioxide emissions over the next 100 years and, hence, there is
little or no offsetting/cooling effect due to aerosols on the
greenhouse gas warming.
So the projections for climate change are now larger than
what they were a few years ago under the second assessment
report. Precipitation is projected to increase globally. But
many arid and semi-arid areas of the Earth are projected to
become drier. The sea level is projected to increase between 10
and 90 centimeters by 2100.
So why do we, society, care? Water resources, managed and
un-managed ecological systems, human health and human
settlements are all predicted to be impacted by climate change.
The arid and semi-arid areas of Africa, the Middle East and
Southern Europe will become even more water-stressed than they
Agricultural production in Africa and Latin America could
decrease ten to thirty percent. The incidence of vector-borne
diseases, such as malaria and dengue, will increase
significantly in tropical countries.
Tens of millions of people will be displaced by rising sea
levels in small island states and low-lying deltaic areas. And
major changes are expected in the boundaries and the structure
and functioning of critical ecological systems, especially in
forests and coral reefs.
The social costs of inaction are quite uncertain, but they
are likely to be in the range of a few percent of world GDP
annually in a doubled carbon dioxide world, with the cost being
substantially greater in developing countries.
However, the good news is that if we go beyond political
ideology, there are numerous cost-effective ways to mitigate
climate change using the extensive array of technologies and
policy measures in both the energy supply and demand sectors.
In addition, a significant potential to increase the uptake
or decrease the emissions of carbon dioxide and other
greenhouse gases through cost-effective changes in land use,
land-use practices and forestry, slowing deforestation, and
improve forest, crop land and range land management.
Policy reform such as the elimination of fossil fuel
subsidies and the internalization of the social costs of
environmental damage will be essential to reduce the emissions
of greenhouse gases.
The flexibility mechanisms of the Kyoto Protocol, emissions
trading, and project-based carbon-offset activities, offer the
possibility of reducing greenhouse gas emissions at a lower
cost than domestic actions alone, and can lead to the transfer
of environmentally sound technologies to countries with
economies in transition and developing countries.
What we also note, however, is that the current efforts and
processes will not be sufficient to facilitate the efficient
transfer of environmentally sound technologies from developed
to developing countries, but opportunities do exist to enhance
the transfer of these technologies, but it will require all
stakeholders to play their role, i.e., governments, industry,
We should note that the atmospheric lifetime of carbon
dioxide, which is the major anthropogenic greenhouse gas, is
more than a century. This means that if policy formulation
waits until all scientific uncertainties are resolved and
carbon dioxide and other greenhouse gases are responsible for
changing the earth's climate as projected by all climate
models, the time to reverse human induced changes in climate
and the resulting environmental damages will not be years or
decades, but centuries to millennia.
I note that enhanced R&D, research and development, policy
reform and promoting market mechanisms will be essential to
address the climate change issue, both domestically and
Last, while scientific uncertainties clearly exist,
governments from around the world have recognized that we know
enough to take the first steps to mitigate climate change.
And, let me leave you with one simple observation. Many of
the global warming skeptics today are the same skeptics who
questioned whether human activities were destroying the earth's
fragile ozone layer and increasing the level of damaging
ultraviolet radiation reaching the Earth's surface. These
skeptics argued against national and global action to protect
the ozone layer.
We now know that human activities were destroying the ozone
layer and thankfully governments from around the world, working
with industry, ignored the skeptics and cost-effective
solutions were developed, thus protecting all life on Earth
from the damaging--damaging ultraviolet radiation.
The Chairman. Thank you, Dr. Watson.
[The prepared statement of Dr. Watson follows:]
Prepared Statement of Dr. Robert Watson, Chairman,
Intergovernmental Panel on Climate Change
It is a pleasure to appear before you today to discuss an issue of
critical importance to this and future generations: global climate
change. My name is Robert T. Watson and I am testifying in my capacity
as the chairman of the Intergovernmental Panel on Climate Change
I would like to first describe the work of the IPCC (Part I) and
then briefly review the current state of knowledge concerning the
climate system (Part II).
PART I: The Intergovernmental Panel on Climate Change
The IPCC is an intergovernmental panel established by the United
Nations in 1988 under the auspices of the World Meteorological
Organization (WMO) and the United Nations Environment Programme (UNEP)
to assess the current state of scientific, technical and economic
knowledge regarding climate change. While the IPCC is an independent
scientific panel, it rides itself on being responsive to addressing the
needs of the UNFCCC and the Kyoto Protocol. Indeed, the current IPCC
work program has been designed to provide the scientific, technical and
economic information that is needed to implement the Convention and the
The IPCC provides comprehensive assessments of the state of
knowledge every five years, complemented by technical papers, special
reports, and methodological work.
The IPCC is in the midst of the preparation and peer-review of the
Third Assessment Report, including the Synthesis Report, and has,
during the last year, completed work on four special reports: (i)
Aviation and the Global Atmosphere; (ii) Methodological and
Technological Aspects of Technology Transfer: Opportunities for
Technology Cooperation; (iii) Emissions Scenarios of Greenhouse Gases
and Aerosol Precursors; and (iv) Land-Use, Land-Use Change and
Forestry. The Summaries for Policymakers for each of these special
reports is included in a series of Annexes * to this testimony. The
three Working Group Reports of the TAR will be completed between
January 2001 and March 2001, while the Synthesis Report will be
completed in September/October 2001.
* Annex 1--Summary for Policymakers: Aviation and the Global
Atmosphere; Annex 2--Summary for Policymakers: Special Report on
Methodological and Technological Issues in Technology Transfer; Annex
3--Summary for Policymakers: Special Report on Emissions Scenarios; and
Annex 4--Summary for Policymakers: Special Report on Land Use, Land-Use
Change and Forestry, have been retained in the Committee files and are
available on the web at http://www.ipcc.ch/pub/reports.htm.
The Third Assessment Report will be a comprehensive assessment and
build upon the findings of the Second assessment Report, which was
completed in 1995. The Third assessment Report will: (i) emphasize
cross-sectoral issues, adaptation and the regional dimensions of
climate change; (ii) place the issue of climate change more centrally
within the concept of sustainable development; and (iii) identify the
synergies and trade-offs between local, regional and global
environmental issues, in particular the inter-linkages between climate
change, biodiversity, water resources and land degradation.
All IPCC assessments are prepared and peer-reviewed, according to
an approved set of principles and procedures, by experts from all
relevant disciplines (natural scientists, social Scientists, and
technologists), from all stakeholder groups (universities, government
agencies, industry, business and environmental organizations) and from
all around the world. Over two thousand experts, from over one hundred
countries, participated in the preparation and peer-review of the
Second Assessment Report. The reports emphasize what is known and what
is uncertain. Areas of controversy are discussed and alternate
The IPCC is currently structured into three Working Groups:
Working Group I
The climate system: Sources and sinks of greenhouse gases and
aerosols; observed changes in atmospheric composition, climate
variables, cryosphere, and sea level; climate variability; physical and
biogeochemical processes; evaluation of approaches for developing
regional climate information; evaluation of models; model simulations
of past and current regional and global climate; model simulations of
future regional and global changes in atmospheric composition,
radiative forcing, climate, cryosphere, and sea level, using agreed and
proposed policies to mitigate climate change, different stabilization
levels of greenhouse gases, and the emissions scenarios from the
ongoing special report; and detection and attribution of climate
Working Group II
Regional, sectoral and cross-sectoral impacts of and adaptation to,
climate change, including the social dimensions (e.g., equity) and
economic costs and benefits: Primers on how terrestrial and marine
ecological and hydrological processes respond to changes in climatic
conditions and atmospheric composition, e.g., increased carbon dioxide
concentrations; primer on human health mechanisms; methodological
approaches to the impact of, and adaptation to, climate change, for
ecological systems, human health and socio-economic sectors; issues in
integrating ecological and economic assessments of impacts and
adaptation potential; evaluation of the sensitivity of ecological
systems, human health and socio-economic sectors to climatic variables;
regional evaluations of the sectoral and cross-sectoral impacts of
climate change, including the social dimensions and economic costs and
benefits; regional sectoral and cross-sectoral adaptation strategies
(technological, institutional, and policy aspects) in the context of
meeting human needs; and global sectoral assessments (e.g., movements
in ecosystem boundaries, and changes in agricultural and fisheries
productivity at the global level). Impact studies will: (i) use a range
of transient GCM projections of climate change, be placed in the
context of other changes in socio-economic and environmental
conditions, and assess to what degree climate change affects the
ability to meet human needs (adequate food, clean water, a healthy
environment, safe shelter, etc.); and (ii) be performed for a range of
climates associated with different greenhouse gas stabilization levels.
Working Group III
Mitigation of climate change, including the social aspects and
economic costs and benefits, and methodological aspects of cross-
cutting issues: Methodological issues associated with mitigation,
equity, discount rates, decision-making framework, uncertainties, and
integrated assessment modeling; evaluation of the technical, economic
and market potential of energy supply and demand and land-use
technologies, regional assessments of the mitigation potential of
different technologies, including the social dimensions and economic
costs and benefits, with and integrated energy-related and land-related
mitigation options, including ``distributional'' costs for different
stabilization levels and different emissions profiles; and evaluation
of policy options (including carbon and energy taxes, subsidy
elimination, internalization of local and regional environmental
externalities, emissions trading and joint implementation).
In addition to the three Working Group Reports, the Third
Assessment Report will contain a Synthesis Report, which is based on
previously approved IPCC reports and will address the following ten key
policy-relevant questions (abbreviated):
What can scientific, technical and socio-economic analyses
contribute to the determination of what constitutes dangerous
anthropogenic interference with the climate system as referred
to in Article 2 of the Framework Convention on Climate Change?
What is the evidence for, causes of, and consequences of
changes in the Earth's climate since the pre-industrial era?
What is known about the influence of the increasing
atmospheric concentrations of greenhouse gases and aerosols,
and the projected human-induced change in climate regionally
What is known about the inertia and time-scales associated
with the changes in the climate system, ecological systems, and
socio-economic sectors and their interactions?
What is known about the regional and global climatic,
environmental, and socio-economic consequences in the next 25,
50 and 100 years associated with a range of greenhouse gas
emissions arising from scenarios used in the TAR (projections
which involve no climate policy interventions)?
How does the extent and timing of the introduction of a
range of emissions reduction actions determine and affect the
rate, magnitude, and impacts of climate change, and affect the
global and regional economy, taking into account the historical
and current emissions?
What is known from sensitivity studies about the regional
and global climatic, environmental and socio-economic
consequences of stabilizing the atmospheric concentrations of
greenhouse gases (in carbon dioxide equivalents), at a range of
levels from today's to double that or more, taking into account
to the extent possible the effects of aerosols. For each
stabilization scenario, including different pathways to
stabilization, evaluate the range of costs and benefits,
relative to the range of scenarios considered in question 5.
What is known about the interactions between projected
human-induced changes in climate and other environmental
issues, e.g., urban air pollution, regional acid deposition,
loss of biological diversity, stratospheric ozone depletion,
and desertification and land degradation? What is known about
the environmental, social and economic costs and benefits and
implications of these interactions for integrating climate
response strategies in an equitable manner into broad
sustainable development strategies at the local, regional and
What is known about the potential for, and costs and
benefits of, and timeframe for reducing greenhouse gas
What are the most robust findings and key uncertainties
regarding attribution of climate change and regarding model
projections of: (i) future emissions of greenhouse gases and
aerosols; (ii) future concentrations of greenhouse gases and
aerosols; (iii) future changes in regional and global climate;
(iv) regional and global impacts of climate change; and (v)
costs and benefits of mitigation and adaptation options?
I would like to briefly summarize the current state of scientific
knowledge concerning climate change.
PART II: Present State of Knowledge
The overwhelming majority of scientific experts recognize that
scientific uncertainties exist, but still believe that human-induced
climate change is inevitable. Indeed, during the last few years, many
parts of the world have suffered major heat-waves, floods, droughts and
extreme weather events leading to significant economic losses and loss
of life. While individual events cannot be directly linked to human-
induced climate change, the frequency and magnitude of these types of
events are expected to increase in a warmer world.
The question is not whether climate will change in response to
human activities, but rather where (regional patterns), when (the rate
of change) and by how much (magnitude). It is also clear that climate
change will adversely effect human health (particularly vector-borne
diseases), ecological systems (particularly forests and coral reefs),
and socio-economic sectors, including agriculture, forestry, fisheries,
water resources, and human settlements, with developing countries being
the most vulnerable. These are the fundamental conclusions of a careful
and objective analysis of all relevant scientific, technical and
economic information by thousands of experts from the appropriate
fields of science from academia, governments, industry and
environmental organizations from around the world under the auspices of
the United Nations International Panel on Climate Change. The good news
is, however, that the majority of energy experts believe that
significant reductions in greenhouse gas emissions are technically
feasible due to an extensive array of technologies and policy measures
in the energy supply and energy demand sectors at little or no cost to
society. In addition, changes in land-use practices can also reduce net
carbon emissions cost-effectively.
However, decision-makers should realize that the atmospheric
residence/adjustment time of carbon dioxide, the major anthropogenic
greenhouse gas, is more than a century, which means that if policy
formulation waits until all scientific uncertainties are resolved, and
carbon dioxide and other greenhouse gases are responsible for changing
the Earth's climate as projected by all climate models, the time to
reverse the human-induced changes in climate and the resulting
environmental damages, would not be years or decades, but centuries to
millennia, even if all emissions of greenhouse gases were terminated,
which is clearly not practical.
This testimony briefly describes the current state of understanding
of the Earth's climate system and the influence of human activities;
the vulnerability of human health, ecological systems, and socio-
economic sectors to climate change; and approaches to reduce emissions
and enhance sinks.
The Earth's Climate System: The Influence of Human Activities
The Earth's climate has been relatively stable (global temperature
changes of less than 1+C over a century) during the present
interglacial (i.e., the past 10,000 years). During this time modem
society has evolved, and, in many cases, successfully adapted to the
prevailing local climate and its natural variability. However, the
Earth's climate is now changing. The Earth's surface temperature this
century is as warm or warmer than any other century during the last
thousand years; the Earth's surface temperature has increased by
between 0.4 and 0.8 degree centigrade over the last century, with land
areas warming more than the oceans; and the last few decades have been
the hottest this century. Indeed, the three warmest years during the
last one hundred years all occurred in the 1990s and the twelve warmest
years during the last one hundred years all occurred since 1983. In
addition, there is evidence of changes in sea level, that glaciers are
retreating world-wide, that Arctic sea ice is thinning, precipitation
patterns are changing, and that the incidence of extreme weather events
is increasing in some parts of the world. Not only is there evidence of
a change in climate at the global level, but there is observational
evidence that the climate of the U.S. is changing in a manner
consistent with that predicted by climate models (I have specifically
mentioned the U.S. because it has a large geographic area and a long
accurate set of weather observations against which model simulations
can be evaluated): increased temperatures (day and night), more intense
rainfall events (defined as two inches within a 24 hour period),
increased precipitation in winter, and less day-day variability in
The atmospheric concentrations of greenhouse gases have increased
because of human activities, primarily due to the combustion of fossil
fuels (coal, oil and gas), deforestation and agricultural practices,
since the beginning of the pre-industrial era around 1750: carbon
dioxide by nearly 30%, methane by more than a factor of two, and
nitrous oxide by about 15%. Their concentrations are higher now than at
any time during the last 160,000 years, the period for which there are
reliable ice-core data, and probably significantly longer. In addition,
the atmospheric concentrations of sulfate aerosols have also increased.
Greenhouse gases tend to warm the atmosphere and, in some regions,
primarily in the Northern hemisphere, aerosols tend to cool the
Theoretical models that take into account the observed increases in
the atmospheric concentrations of greenhouse gases and sulfate aerosols
simulate the observed changes in surface temperature and the vertical
distribution of temperature quite well. This, and other information,
suggests that human activities are implicated in the observed changes
in the Earth's climate. In fact, the observed changes in climate cannot
be explained by natural phenomena alone (e.g., changes in solar output
and volcanic emissions).
Future emissions of greenhouse gases and the sulfate aerosol
precursor, sulfur dioxide, are sensitive to the evolution of governance
structures world-wide, whether the current inequitable distribution of
wealth continues or decreases, changes in population and gross domestic
product, the rate of diffusion of new technologies into the market
place, production and consumption patterns, land-use practices, energy
intensity, and the price and availability of energy. Most projections
suggest that greenhouse gas concentrations will increase significantly
during the next century in the absence of policies specifically
designed to address the issue of climate change. Indeed, the recent
IPCC special report on emissions scenarios reported, for example,
carbon dioxide emissions from the combustion of fossil fuels are
projected to range from bout 5 to 35 GtC per year in the year 2100:
compared to current emissions of about 6.3 GtC per year. Such a range
of emissions would mean that the atmospheric concentration of carbon
dioxide would increase from today's level of 360 ppmv (parts per
million by volume) to between 500 and 900 ppmmv by 2100. It should be
noted that two major oil companies, Shell and British Petroleum, have
suggested that the mix of energy sources could change radically, with
renewable energy sources (solar, wind and modern biomass) accounting
for as much as half of all energy produced by the middle of the next
century. Such a future would be consistent with the lower projections
of greenhouse gas emissions and would clearly eliminate the highest
projections of greenhouse gases from being realized, but this vision of
a future world will not occur without policy reform and significantly
enhanced public and private sector energy R&D programs.
While the recent IPCC special report on emissions scenarios (SRES
00) reported similar projected emissions for carbon dioxide to the 1992
projections, it differed in one important aspect from the 1992
projections, in-so-far-as the projected emissions of sulfur dioxide are
much lower. This has important implications for future projections of
temperature changes, because sulfur dioxide emissions lead to the
formation of sulfate aerosols in the atmosphere, which as stated
earlier can partially offset the warming effect of the greenhouse
Based on the range of climate sensitivities (an increase in the
equilibrium global mean surface temperature of 1.5-4.5+C for a doubling
of atmospheric carbon dioxide concentrations) and plausible ranges of
greenhouse gas and sulfur dioxide emissions (SRES 00), climate models
project that the global mean surface temperature could increase by 1 to
5+C by 2100. These projected global-average temperature changes would
be greater than recent natural fluctuations and would also occur at a
rate significantly faster than observed changes over the last 10,000
years. These long-term, large-scale, human-induced changes are likely
to interact with natural climate variability on time-scales of days to
decades (e.g., the El Nino-Southern Oscillation (ENSO) phenomena).
Temperature changes are expected to differ by region with high
latitudes projected to warm more than the global average. However, the
reliability of regional scale predictions is still low. Associated with
these estimated changes in temperature, sea level is projected to
increase by 10-90 cm by 2100, caused primarily by thermal expansion of
the oceans and the melting of glaciers. However, it should be noted
that even when the atmospheric concentrations of greenhouse gases are
stabilized, temperatures will continue to increase for several decades
because of the thermal inertia of the climate system (temperature by
another 30-50%), and sea level for an even longer period of time
(centuries to millennia).
Model calculations show that evaporation will be enhanced as the
climate warms, and that there will be an increase in global mean
precipitation and an increase in the frequency of intense rainfall.
However, not all land-regions will experience an increase in
precipitation, and even those land regions with increased precipitation
may experience decreases in soil moisture, because of enhanced
evaporation. Seasonal shifts in precipitation are also projected. In
general, precipitation is projected to increase at high latitudes in
winter, and soil moisture is projected to decrease in some mid-latitude
continental regions during summer. The arid and semi-arid areas in
Southern and Northern Africa, Southern Europe and the Middle East are
expected to become drier.
While the incidence of extreme temperature events, floods,
droughts, soil moisture deficits, fires and pest outbreaks is expected
to increase in some regions, it is unclear whether there will be
changes in the frequency and intensity of extreme weather events such
as tropical storms, cyclones, and tornadoes.
The Vulnerability of Human Health, Ecological Systems, and Socio-
economic Sectors to Climate Change
The IPCC has assessed the potential consequences of changes in
climate for human health, ecological systems and socio-economic sectors
for ten continental- or subcontinental-scale regions: Africa,
Australasia, Europe, Latin America, Middle East and Arid Asia, North
America, Polar regions, Small Island States, Temperate Asia, and
Tropical Asia. Because of uncertainties associated with regional
projections of climate change, the IPCC assessed the vulnerability of
these natural and social systems to changes in climate, rather than
attempting to provide quantitative predictions of the impacts of
climate change at the regional level. Vulnerability is defined as the
extent to which a natural or social system is susceptible to sustaining
damage from climate change, and is a function of the sensitivity of a
system to changes in climate and the ability to adapt the system to
changes in climate. Hence, a highly vulnerable system is one that is
highly sensitive to modest changes in climate and one for which the
ability to adapt is severely constrained.
Most impact studies have assessed how systems would respond to a
climate change resulting from an arbitrary doubling of atmospheric
carbon dioxide concentrations. Very few have considered the dynamic
responses to steadily increasing greenhouse gas concentrations; fewer
yet have been able to examine the consequences of increases beyond a
doubling of greenhouse gas concentrations or to assess the implications
of multiple stress factors.
The IPCC concluded that human health, terrestrial and aquatic
ecological systems, and socioeconomic systems (e.g., agriculture,
forestry, fisheries, water resources, and human settlements), which are
all vital to human development and well-being, are all vulnerable to
changes in climate, including the magnitude and rate of climate change,
as well as to changes in climate variability. Whereas many regions are
likely to experience the adverse effects of climate change--some of
which are potentially irreversible--some effects of climate change are
likely to be beneficial. Hence, different segments of society can
expect to confront a variety of changes and the need to adapt to them.
There are a number of general conclusions that can be easily drawn:
(i) human-induced climate change is an important new stress,
particularly on ecological and socio-economic systems that are already
affected by pollution, increasing resource demands, and non-sustainable
management practices; (ii) the most vulnerable systems are those with
the greatest sensitivity to climate change and the least adaptability;
(iii) most systems are sensitive to both the magnitude and rate of
climate change; (iv) many of the impacts are difficult to quantify
because existing studies are limited in scope; and (v) successful
adaptation depends upon technological advances, institutional
arrangements, availability of financing and information exchange, and
that vulnerability increases as adaptation capacity decreases.
Therefore, developing countries are more vulnerable to climate change
than developed countries.
The range of adaptation options for managed systems such as
agriculture and water supply is generally increasing because of
technological advances. However, some regions of the world, i.e.,
developing countries, have limited access to these technologies and
appropriate information. The efficacy and cost-effectiveness of
adaptation strategies will depend upon cultural, educational,
managerial, institutional, legal and regulatory practices that are both
domestic and international in scope. Incorporation of climate change
concerns into resource-use and development decisions and plans for
regularly scheduled investments in infrastructure will facilitate
Let me now briefly discuss the implications of climate change for a
representative number of systems: natural ecosystems (forests and coral
reefs), food security, water resources, sea level rise, and human
The composition and geographic distribution of many ecosystems will
shift as individual species respond to changes in climate, and there
will likely be reductions in biological diversity (particularly species
diversity) and in the goods and services ecosystems provide society,
e.g., sources of food, fiber, medicines, recreation and tourism, and
ecological services such as controlling nutrient cycling, Waste
quality, water run-off, and soil erosion. Models project that as a
consequence of possible changes in temperature and water availability
under doubled carbon dioxide equilibrium conditions, a substantial
fraction (a global average of one-third, varying by region from one-
seventh in tropical forests to two-thirds in Boreal forests) of the
existing forested area of the world will undergo major changes in broad
vegetation types. Climate change is expected to occur at a rapid rate
relative to the speed at which forest species grow, reproduce and re-
establish themselves. For mid-latitude regions a global average warming
of 1-3.5+C over the next 100 years would be equivalent to a poleward
shift of isotherms of approximately 150-550 km or an altitude shift of
150-550 meters. This compares to past tree species migration rates that
are believed to be on the order of 4-200 km per century. Therefore,
species composition of impacted forests is likely to change, entire
forest types may disappear, while new assemblages of species and hence
new forest ecosystems may be established. Large amounts of carbon could
be released into the atmosphere during times of high forest mortality
prior to regrowth of a mature forest.
Natural Ecosystems--Coral Reefs
Coral reefs, the most biologically diverse marine ecosystems, are
important for fisheries, tourism, coastal protection, and erosion
control. Coral reef systems, which are already being threatened by
pollution, unsustainable tourism and fishing practices, are very
vulnerable to changes in climate. While these systems may be able to
adapt to the projected increases in sea level, sustained increases in
water temperatures of 3-4+C above long-term average seasonal maxima
over a 6-month period can cause significant coral mortality; short-term
increases on the order of only 1-2+C can cause ``bleaching,'' leading
to reef destruction. Indications are that the full restoration of coral
communities could require several centuries.
Currently, 800 million people are malnourished; as the world's
population increases and incomes in some countries rise, food
consumption is expected to double over the next three to four decades.
Studies show that on the whole, global agricultural production could be
maintained relative to baseline production in the face of climate
change under doubled carbon dioxide equilibrium conditions. However,
crop yields and changes in productivity due to climate change will vary
considerably across regions and among localities, thus changing the
patterns of production. In general, productivity is projected to
increase in middle to high latitudes, depending on crop type, growing
season, changes in temperature regime, and seasonality of
precipitation, whereas in the tropics and subtropics, where some crops
are near their maximum temperature tolerance and where dryland, non-
irrigated agriculture dominates, yields are likely to decrease,
especially in Africa and Latin America, where decreases in overall
agricultural productivity of 30% are projected under doubled carbon
dioxide conditions. Therefore, there may be increased risk of hunger in
some locations in the tropics and subtropics where many of the world's
poorest people live.
Currently 1.3 billion people do not have access to adequate
supplies of safe water, and 2 billion people do not have access to
adequate sanitation. Today, some nineteen countries, primarily in the
Middle East and Africa, are classified as water-scarce or water-
stressed. Even in the absence of climate change, this number is
expected to double by 2025, in large part because of increases in
demand from economic and population growth. Climate change will further
exacerbate the frequency and magnitude of droughts in some places, in
particular Northern and Southern Africa and the Middle East where
droughts are already a recurrent feature. Developing countries are
highly vulnerable to climate change because many are located in arid
and semi-arid areas.
Sea Level Rise
Sea-level rise can have negative impacts on tourism, freshwater
supplies, fisheries, exposed infrastructure, agricultural and dry
lands, and wetlands. It is currently estimated that about half of the
world's population lives in coastal zones, although there is a large
variation among countries. Changes in climate will affect coastal
systems through sea-level rise and an increase in storm-surge hazards,
and possible changes in the frequency and/or intensity of extreme
events. Impacts may vary across regions, and societal costs will
greatly depend upon the vulnerability of the coastal system and the
economic situation of the country. Sea-level rise will increase the
vulnerability of coastal populations to flooding. An average of about
46 million people per year currently experience flooding due to storm
surges; a 50 cm sea-level rise would increase this number to about 92
million; a 1 meter sea-level rise would increase this number to 118
million. The estimates will be substantially higher if one incorporates
population growth projections. A number of studies have shown that
small islands and deltaic areas are particularly vulnerable to a one-
meter sea-level rise. In the absence of mitigation actions (e.g.,
building sea walls), land losses are projected to range from 1.0% for
Egypt, 6% for Netherlands, 17.5% for Bangladesh, to about 80% of the
Marshall Islands, displacing tens of millions of people, and in the
case of low-lying Small Island States, the possible loss of whole
cultures. Many nations face lost capital value in excess of 10% of GDP.
While annual adaptation/protection costs for most of these nations are
relatively modest (about 0.1% GDP), average annual costs to many small
island states are much higher, several percent of GDP, assuming
adaptation is possible.
Human health is sensitive to changes in climate because of changes
in food security, water supply and quality, and the distribution of
ecological systems. These impacts would be mostly adverse, and in many
cases would cause some loss of life. Direct health effects would
include increases in heat-related mortality and illness resulting from
an anticipated increase in heatwaves. Indirect effects would include
extensions of the range and season for vector organisms, thus
increasing the transmission of vector-borne infectious diseases (e.g.,
malaria, dengue, yellow fever and encephalitis). Projected changes in
climate under doubled carbon dioxide equilibrium conditions could lead
to potential increases in malaria incidence of the order of 50-80
million additional cases annually, primarily in tropical, subtropical,
and less well-protected temperate-zone populations. Some increases in
non-vector-borne infectious diseases such as salmonellosis, cholera and
other food- and water-related infections could also occur, particularly
in tropical and subtropical regions, because of climatic impacts on
water distribution and temperature, and on micro-organism
Social Costs of Climate Change
The range of estimates of economic damages caused by changes in
climate are quite uncertain. Taking into account both market and non-
market costs, IPCC reported a reduction in world GDP of 1.5-2.0% for a
doubled carbon dioxide environment. This value was obtained by summing
widely varying estimates of damages by sector, including socio-economic
sectors (e.g., agriculture, forestry, fisheries), ecological systems,
and human health. Nordhaus, conducted an ``expert'' survey which
resulted in a range from 0 to 21% for loss of world GDP, with a mean
value of 3.6% and a median value of 1.9%.
Losses in developing countries are estimated to be much higher than
the world average, ranging from 5% to 9%. Alternate assumptions about
the value of a statistical life could increase the estimate of economic
damages in developing countries.
IPCC reported values for the marginal damage of one extra ton of
carbon emitted ranging from $5 to $125. A value of $5 to $12 per ton of
carbon is obtained using a 5% social rate of time preference (discount
rate). Lower discount rates increase this estimate, e.g. a 2% discount
rate would increase this estimate by an order of magnitude.
Approaches to Reduce Emissions and Enhance Sinks
Significant reductions in net greenhouse gas emissions are
technically, and often economically, feasible and can be achieved by
utilizing an extensive array of technologies and policy measures that
accelerate technology diffusion in the energy supply (more efficient
conversion of fossil fuels; switching from high to low carbon fossil
fuels; decarbonization of flue gases and fuels, coupled with carbon
dioxide storage; increasing the use of nuclear energy; and increased
use of modem renewable sources of energy (e.g., plantation biomass,
micro-hydro, and solar), energy demand (industry, transportation, and
residential/commercial buildings) and agricultural/foresty sectors
(altered management of agricultural soils and rangelands, restoration
of degraded agricultural lands and rangelands, slowing deforestation,
natural forest generation, establishment of tree plantations, promoting
agroforestry, and improving the quality of the diet of ruminants). By
the year 2100, the world's commercial energy system will be replaced at
least twice offering opportunities to change the energy system without
premature retirement of capital stock. However, full technical
potential is rarely achieved because of a lack of information and
cultural, institutional, legal and economic barriers.
Policy instruments can be used to facilitate the penetration of
lower carbon intensive technologies and modified consumption patterns.
These policies include: energy pricing strategies (e.g., carbon taxes
and reduced energy subsidies); reducing or removing other subsidies
that increase greenhouse gas emissions (e.g., agricultural and
transport subsidies); incentives such as provisions for accelerated
depreciation and reduced costs for the consumer; tradable emissions
permits (and joint implementation); voluntary programs and negotiated
agreements with industry; utility demand-side management programs;
regulatory programs including minimum energy efficiency standards;
market pull and demonstration programs that stimulate the development
and application of advanced technologies; and product labeling. The
optimum mix of policies will vary from country to country; policies
need to be tailored for local situations and developed through
consultation with stakeholders.
Estimates of the costs of mitigating climate change should take
into account secondary benefits of switching from a fossil fuel based
economy to a lower-carbon intensity energy system. Secondary benefits
include lower levels of local and regional pollution, including
particulates, ozone and acid rain.
A key issue recognized by all Parties to the UNFCCC and the Kyoto
Protocol is that of technology transfer. The recent IPCC special report
on technology transfer examined the flows of knowledge, experience and
equipment among governments, private sector entities, financial
institutions, NGOs, and research and education institutions, and the
different roles that each of these stakeholders can play in
facilitating the transfer of technologies to address climate change in
the context of sustainable development. The report concluded that the
current efforts and established processes will not be sufficient to
meet this challenge. It is clear that enhanced capacity is required in
developing countries and that additional government actions can create
the enabling environment for private sector technology transfers within
and across national boundaries.
Policymakers are faced with responding to the risks posed by
anthropogenic emissions of greenhouse gases in the face of significant
scientific uncertainties. They should consider these uncertainties in
the context that climate-induced environmental changes cannot be
reversed quickly, if at all, due to the long time scales (decades to
millennia) associated with the climate system. Decisions taken during
the next few years may limit the range of possible policy options in
the future because high near-term emissions would require deeper
reductions in the future to meet any given target concentration.
Delaying action might reduce the overall costs of mitigation because of
potential technological advances but could increase both the rate and
the eventual magnitude of climate change, and hence the adaptation and
Policymakers will have to decide to what degree they want to take
precautionary measures by mitigating greenhouse gas emissions and
enhancing the resilience of vulnerable systems by means of adaptation.
Uncertainty does not mean that a nation or the world community cannot
position itself better to cope with the broad range of possible climate
changes or protect against potentially costly future outcomes. Delaying
such measures may leave a nation or the world poorly prepared to deal
with adverse changes and may increase the possibility of irreversible
or very costly consequences. Options for adapting to change or
mitigating change that can be justified for other reasons today (e.g.,
abatement of air and water pollution) and make society more flexible or
resilient to anticipated adverse effects of climate change appear
If, actions are not taken to reduce the projected increase in
greenhouse gas emissions, the Earth's climate is projected to change at
an unprecedented rate with adverse consequences for society,
undermining the very foundation of sustainable development. Adaptive
strategies to deal with this issue need to be developed, recognizing
issues of equity and cost-effectiveness.
While there is no debate that protection of the climate system will
eventually need all countries to limit their greenhouse gas emissions,
the Framework Convention on Climate Change recognizes the principle of
differentiated responsibilities, and also recognizes that developed
countries and countries with economies in transition should take the
lead in limiting their greenhouse gas emissions given the historical
and current emissions of greenhouse gases, and their financial,
technical and institutional capabilities. Current and historical
emissions of greenhouse gases arise mainly from developed countries and
countries with economies in transition, i.e., emissions in developing
countries are much lower, both in absolute and per capita terms. Even
though it is well recognized that emissions from developing countries
are increasing rapidly due to increases in population and economic
growth, and are likely to surpass those from developed countries within
a few decades (absolute terms, not per-capita), their contribution to
global warming will not equal that of developed countries until nearly
2100 because the climate system responds to the cumulative emissions of
greenhouse gases not the annual emissions. It is also quite clear that
increased energy services in developing countries are critical in order
to alleviate poverty and underdevelopment, where 1.3 billion people
live on less than $1 per day, 3 billion people live on less than $2 per
day, and 2 billion people are without electricity. Hence the challenge
is to assist developing countries expand their production and
consumption of energy in the most efficient and environmentally benign
manner. Financial instruments such as the Global Environment Facility
and promoting market mechanisms such as emissions trading and joint
implementation can assist in this endeavor. In addition, an increased
commitment to energy R&D for energy efficient technologies and low-
carbon technologies would not only allow the U.S. to meet it's energy
needs in a more climate friendly manner, but it would also provide a
large market in developing countries for U.S. exports.
Mr. Chairman, members of the Committee, I appreciate the
opportunity you have provided me to be able to discuss these important
issues with you today. Thank-you.
The Chairman. Dr. Christy, can you further discuss the
reasons why we are not experiencing the rate of temperature
increase in the upper altitudes that computer models may be
Dr. Christy. OK. You are asking for the ``why'' of this
issue, and I do not have an answer for why, here. I would like
to say that the disparity is greatest in the tropical regions,
and this lower tropospheric layer of the atmosphere is far
below what ozone depletion would impact. In fact, I have
checked specifically to make sure that--that the temperature
rise at 100 millebars--what would that be? About--about ten
miles or so.
The temperature even in the upper troposphere at 100
millebars is actually slightly warmer than it is in this bulk
of the atmosphere below that we are measuring in terms of
trends. So I do not have an answer for ``why.'' I am skeptical
about ozone depletion as part of the cooling effect on that
particular layer (i.e., the lower troposphere.
The Chairman. Well, do you disagree with Dr. Mahlman's
assertion that the increasing greenhouse gas effect is due to
Dr. Christy. Oh, no. I do not disagree with that at all.
The Chairman. Thank you.
Dr. Mahlman, Dr. Trenberth's statement says that the main
reason tropospheric temperatures are not keeping pace are
because of stratospheric ozone depletion and increases in cloud
cover. Do your models confirm those events?
Dr. Mahlman. We have done independent calculations of the
effect of the reduced ozone levels in the lower stratosphere,
both in the tropical regions and in higher latitudes.
And we calculate a double effect from that. One is that the
reduced ozone produces a reduced downward welling of infrared
radiation, therefore cooling the troposphere.
But we also see that that depleted ozone in the lower
stratosphere is transported downward and making lower ozone
levels in the upper troposphere. Both of these effects produce
cooling as counterbalance to the warming effect. So it is a
Part of the problem is that we do not have really good
ozone profile data, because some of the best measurements of
ozone profiles have literally disappeared over the last 20
years and not to be replaced. And so it is hard to really pin
There are also the uncertain effects, in my view, of this
21-year time series of the quantitative effects of the El
Chichon and Pinatubo volcanoes, whether these would also lead
to a cooling effect in the upper troposphere that would add to
the ozone effect.
There is also the issue of ``What are the errors in the
repaired satellite data and the repaired radiosonde data?''
Both Dr. Christy and Dr. Trenberth can comment on that as well.
But as Dr. Trenberth quite properly pointed out, neither of
these are well-posed measuring systems that are designed to
produce accurate monitoring of the climate in three dimensions
in the atmosphere.
So we are really suffering from significant data problems
whether that residual difference is physically robust or not.
If I were forced to put it on Jerry's betting odds scale, so to
speak, I would guess that it is a two out of three chance that
there is a robust difference. But I think there is a
significant uncertainty in how big that difference is.
The Chairman. If other panel members wish to make comments
on the questions that I direct to the witnesses, please feel
free to do so.
Dr. Trenberth, you heard me say at the beginning of this
hearing that there is no such thing as a dumb question, right?
If evaporation is taking place as the result of this and that
evaporation, as you mentioned, is taking place in the oceans,
why is the sea level rising? Is it simply because of the
melting of the icecaps?
Dr. Trenberth. The sea level is rising because of two
things. About--one of the estimates is that about maybe 20
percent of the heat from the global warming overall is going
into the ocean. That causes expansion of the ocean and the
evidence suggests now that, indeed, the oceans are warming up.
The second thing is the melting of glaciers. Glaciers are
melting almost everywhere around the world. The only places
where they are not melting is because of increases in
precipitation; increases in snow. And that is mainly in
Scandinavia. And so these are the main reasons for the rise in
The amount of moisture in the atmosphere is really very
small compared with that in the oceans. And so anything that is
stored in the atmosphere has a minuscule effect on sea level
But over the United States where we have the best
measurements and--unfortunately, these measurements are really
only reliable for about the past 25 years or so--there is good
evidence that the amount of moisture in the atmosphere has
increased by about 10 percent.
That is a large amount. It is more than we would expect
from just the greenhouse effect alone of global warming, but it
is one of the effects, which means that there is more moisture
that is hanging around to get caught up in storms. And it makes
the storms more severe than they otherwise would be, rainfall
rates heavier than they otherwise would be, such as we have
just seen, for instance, in eastern Oklahoma and--and Missouri
with the flooding that occurred there. And drying, of course,
occurs somewhere else in the system. In this case, there has
been a lot of drying over the Southwest.
The Chairman. Dr. Watson, what has caused scientific
confidence to increase between the IPCC's 1996 assessment and
Dr. Watson. Well, even in the 1995 assessment, we could not
explain the observed changes in the Earth's climate on natural
phenomena alone. And that led to the very famous phrase, and
that is, ``There is now--the scientific evidence now shows a
discernible human influence on the earth's climate system.''
And as Dr. Mahlman said, the likely conclusions from the
third assessment report, which is currently undergoing very
careful peer review, are likely to confirm the findings of the
second assessment report.
We have got improved models. We have continuing data sets.
Obviously, the research done by the U.S. Global Change Research
Program has helped us get a slightly better understanding of
some of these phenomena.
But I do not believe that there has been a radical change,
in my opinion, of thinking over the last few years. I think
there has been a consolidation of the thinking that we had in
1995, which, of course, as you know, led most governments in
the world to negotiate the Kyoto Protocol.
The Chairman. Go ahead, Doctor.
Dr. Mahlman. If I might just add to that. The observational
record is very important here. The warmest years on record have
occurred since the 1995 report, 1998 being the warmest year on
record. And that is not something to be neglected.
The other thing is the reconstruction, which Dr. Bradley
showed, of the pulling together of all of the paleoclimatic
data and synthesizing that to give us a better picture as to
what the natural variability has been like in the past. That
this puts the current warming in a much better historical
context has been a significant factor, as well.
And the third thing, in addition to the improvements in
modeling, I would point to is improved statistical analysis and
detection methods that have been applied to this problem.
The Chairman. Dr. Christy, would you like to respond to
that? I do not--I am not sure you--I do not believe you share
exactly those views according to your testimony.
Dr. Christy. The--all of us that work on the IPCC--and my
chapter is the observations chapter--we will document in the
IPCC indications of rapid climate changes that have occurred in
the past under natural conditions, most of which can be
explained by unusual situations in the earth.
I would like to comment, though, on what we affectionately
call the hockey stick diagram that Dr. Bradley showed, because
it has this steady decline and then this rapid increase. I want
to describe a feature of that diagram, which is not a
The information that went into the first half of that
record is very limited and as you go to the end of the record
to the year 2000, a considerably larger amount of data went
into that part, so that there could be a--a refinement of what
the temperature record looks like at the end.
If you just took the information that was available at the
beginning and kept only that to the end, you would not see this
dramatic spike at the end. And so it is different information
that allows you to see what has happened in the last 100 years
than what is shown at the beginning.
The Chairman. But you do not disagree with the fundamental
premise that the other witnesses have asserted that there is an
increase in global warming. It is attributed to human activity.
Dr. Christy. The Earth's temperature has risen. I do not
disagree with that. And I agree that a portion of that is due
to human effects, but I would not say all of it is due to human
effects. I do not think anyone here might either.
The Chairman. Dr. Mahlman, I know you want to speak.
And then, Dr. Bradley, maybe you would like to respond to
the hockey stick issue.
Dr. Mahlman. Yes. If I were to have answered the question
first, I would have raised the same two points that Dr.
Trenberth raised, namely the fact that it is getting warmer,
and noticeably so since the last IPCC assessment; and then also
the amazing 1,000-year record from Drs. Mann and Bradley.
And the other thing I would add to that is that, post-IPCC
1995, the IPCC process made their best guess as to what the
forcing agents for climate were over the past 150 years, and
asked the leading model groups to make independent calculations
of a retrospective run-through from 1760 to 2000. Effectively,
all of the models pretty much nailed this increase in
temperature. And models with different physics, different
constructions still get essentially the same kind of answer.
Now, in each one of these cases, you can make the counter-
argument and say, ``Well, that's certainly not definitive
evidence.'' And that would be a valid point.
But on the other hand, the fact that there are three new
and essentially totally independent pieces of information that
came since the last IPCC, in my mind, that shrinks the betting
odds, shrinks the range of uncertainty. It does not make
uncertainty go away.
And so ultimately, it will boil down to the level of proof
that people require in order to take meaningful action.
The Chairman. Dr. Bradley.
Dr. Bradley. With reference to this hockey stick issue,
there may not be too many hockey sticks needed in the future,
in Massachusetts anyway.
Dr. Bradley. We initially began this analysis originally by
assembling as much data as we could and push the record back
to, I think it was, maybe 1400. And on the basis of that data
set, we demonstrated that we could reproduce the instrumental
data completely independent from this--this network of paleo
data. We then attempted to push it back a little bit further
with a much sparser network of data. As you go through back in
time, you lose more data.
Dr. Bradley. But you can see from this record and we--we
tried to be as honest as possible, by putting this yellow
envelope of uncertainty. You can see the envelope of
uncertainty gets bigger as you go back in time.
But in the context of what the model projections are for
the next century, the changes we have seen in the last 1,000
years are fairly trivial.
And so I think that is the important value of this
perspective. You step back beyond the period of our own
experience, the last century or so. You look at it in the
longer term, when clearly before 1800, it was all due to
natural variability. It was not due to greenhouse gases--a pre-
industrial level of greenhouse gases.
So what you see in that graph is just the earth doing its
thing, solar variations, volcanic eruptions, whatever. Those
are the amplitudes of change that we believe are real.
And then you compare that with what are projected to--to
take place in the future. And you can see that it is just off
The Chairman. My final question--I appreciate the
indulgence of my colleagues.
If the blade part of the hockey stick here in your graph is
largely accepted as valid, why is it that you think that there
is not greater concern than that exists today about that blade
of the hockey stick?
Dr. Bradley. You know, this diagram is patched together
from two pieces of information. I do not think it has been seen
before, in fact.
The left-hand side, the red and the yellow represent--the
red is the instrumental element; the yellow is the
reconstruction; and the gray area represents the projected. So
that brings it all together and puts it in perspective.
I think this diagram is compelling. And if it is seen more
widely people will be forced to face the fact that these are
very large changes. I think as we develop our science and we
make these kinds of figures available to people, they will
begin to realize the magnitude of change.
Now, why do we not take it more seriously? Because the
problem is incredibly difficult to resolve, as you no doubt,
grapple with within yourself.
How do--how are we going to deal with the fundamental use
of fossil fuel in our society and around the world? How are we
going to deal with the fact that the population growth is going
to double this century? That is the fundamental driver of this
change in temperature.
Unless we can come to grips, we obviously are not going to
do much about changing population growths. We have got to do
something about the carbon-based fuel economy of the world. We
have got to come up with more efficient ways of managing our
And in the long run, it obviously must be more beneficial
to our economy to use less fossil fuel. It has got to be more
sensible to run an engine on less energy, to run a factory on
less energy, and use less energy to heat or cool our homes. The
short-term costs may be profound. But the long-term has got to
be a boost for our overall commerce, I would think.
The Chairman. Any other panelists wish to--go ahead, Dr.
Mahlman. We will go right down the list. Dr. Christy, you are
included in this assessment.
Dr. Mahlman. Oh, I think this is an extremely important
question, and if I could repeat the question to know I
understand it. Given all this, why are people not more
concerned than--than they are----
The Chairman. Than they--yes.
Dr. Mahlman [continuing]. Governments and everybody? I have
had the good fortune to have spoken face to face to the order
of 10,000 people on this--on this subject. And this comes up
all the time.
And it is a universal issue. And I would submit on the
basis of my encounters with all these people that it boils down
to a couple of things.
One is that it is a hard problem to immediately associate
with--with a really scary issue, until you start doing what we
have been doing today, which is looking at each thing and
finding out what sectors are--are affected and how they might
be affected. And then suddenly, the potential for serious harm
begins to creep out of that. And the second part----
The Chairman. By the way, including a new European--a group
recently discovered a greenhouse gas with frightful
characteristics, SF--SCF3, I think.
Dr. Mahlman. Yes.
The Chairman. You are familiar with that?
Dr. Mahlman. Yes. Dr. Watson and I will probably both
quickly say that this is part of a class of extraordinarily
long-lived greenhouse gases, most of them human produced, that
have tremendous global warming potential. It is in the IPCC and
the ozone assessment reports.
And there is nothing, to me, particularly new about that.
It is part of a whole class of fluorocarbons and other very
long-lived greenhouse gases that exist in a few parts per
trillion, that probably will be removed quickly from
manufacturing processes. So I do not see this as a new issue.
The second thing I would like to say about why people are
not acting and concerned so much is, in my view, this problem
has an extraordinarily high degree of difficulty factor. It is
very easy to demagogue it from all sorts of viewpoints, because
it is not just a matter of what the U.S. does or what this
Committee does. It is what the whole planet does.
And, in that sense, it seems so overwhelming that we,
therefore, do not have to do very much. And, of course, in this
problem, like many other problems, a non-decision is a decision
in the sense that we all are implicitly agreeing to keep
increasing emissions of CO2 into the atmosphere.
The Chairman. Dr. Trenberth.
Dr. Trenberth. Yes. Thank you. Climate change is not
necessarily bad. When you deplete the ozone layer, the
consensus was that this was a universally bad thing and,
therefore, a coordinated activity could occur. But warming in
wintertime can be beneficial for some things, for instance.
The real problem, which I do not think is adequately
appreciated, is that change by its very nature can be
disruptive and tends to be disruptive. And even though we may
be changing in some areas to a climate that is better in some
sense, it is not going to stay there. It is going to continue
In fact, we are entering a period of instability in our
climate, and we are not going to know just what the climate is
going to be next year or for the next 30 years, and actually
this puts an imperative on making better climate predictions so
that we will have those predictions to be able to base
decisions upon, because we will not be able to use the climate
of the past to make those decisions.
And this applies in so many parts of society and activities
that we have, such as planning of dams and especially water
resources. And I personally think the main pressure points on
society will be changes in precipitation, changes in extremes,
managing water and water resources, portable water in
particular, and the effects of changes in the extremes on
society and on the environment.
Unfortunately, our data bases for those are not as good as
they are for mean global temperature. As I mentioned before, a
one-degree change in global mean temperature translated locally
does not mean much. But, in fact, this record has included
things like the Little Ice Age, which caused major disruptions
And so regionally, the manifestations of this can, indeed,
be very great and profound. And so getting these aspects across
to the general public and to policymakers is not an easy thing
The Chairman. Dr. Christy.
Dr. Christy. I agree with Dr. Trenberth, who actually is my
former advisor when I was back in graduate school. And I
usually have a difficult time to be more skeptical than he is,
but sometimes I can.
In Alabama, the temperature has fallen over the last 105
years, so people right there are not going to be very concerned
about global warming when the temperature in their local region
has not warmed at all. The second thing----
The Chairman. If the Gulf shores is inundated, at least in
the southern part of the state there remains some concern.
Dr. Christy. I repeatedly advise people who are interested
in beach-front property that I do not care about six inches of
rise relative to hurricanes. It is the next hurricane that is
going to visit the area that is the problem, and they should
stay away from the beach for that reason.
Cheap energy means longer and better lives. And I have seen
that. I was a missionary in Africa, and I saw people who
literally died when energy costs increased because they just
lived right on the edge of existence. So I would be very
concerned about increasing the cost of energy for the poor
people of Alabama, and those around the world.
And in agreement with everyone here, if there is some way
to keep energy cheap and not produce CO2, I am all
for it. That is fine, if we can do that.
Now, lastly, fortunately in this business, CO2
itself is plant food. It is not toxic. CO2 does not
bother us, and it invigorates the plant world. The plant world
you see around you evolved at a time when there was ten times
as much CO2 as there is now. So that is one thing
that we can be thankful for, at least in terms of the toxicity
that CO2 is harmless.
It is the climate change issue, the secondary effect of
CO2 that is of concern to us all.
The Chairman. Dr. Watson.
Dr. Watson. My comment would be, simply, most scientists
are concerned about climate change. Most governments are
concerned about climate change, which is why most of them
signed the Kyoto Protocol.
Some businesses are becoming more concerned about climate
change. Shell and B.P. in Europe, others in the U.S. have all
now got internal trading systems, and they have got their own
targets, and they are very similar to Kyoto.
One of the big problems, however, is what differentiates
this from the ozone issue. In both cases ozone depletion and
global warming is largely being caused by emissions from the
rich countries, the U.S. and Europe, Japan.
With ozone depletion, the impact is skin cancer on light-
skinned people. Americans cared about it. So did the Europeans.
The major impact of global warming will be on developing
countries and especially the poor in developing countries. The
U.S. will be hit, but the biggest impact is on developing
countries. So it does not hit home in quite the way skin cancer
did with the ozone issue.
But the basic point is--and that is why Shell and others
are starting to act--there are cost effective solutions,
especially when we use the so-called flexibility mechanisms,
emissions trading internationally and project-based joint
There are distributionable issues. The coal industry is not
going to be a winner. The renewable energy industry will be a
winner, and even the gas industry. So there are
distributionable issues and political forces at play,
especially in the U.S. and in, say, Australia, where there is a
lot of cheap coal reserves.
There is no question we can de-carbonize the energy system
in the next 50 years. We do not need to do it in 5 years. We
have to have a long-term strategy to de-carbonize our energy
And the population issue is also a manageable issue. If we
follow the Cairo principles of culturally acceptable forms of
contraception, education especially of girls and empowerment of
women, we can actually start to lower the projections of
And the latest projections suggest that there could well be
a stabilization around 9 billion people, only 50 percent more
than now and starting to decrease by the end of the next
So these are indeed solvable issues, but it takes political
will and it takes partnership between government, the private
sector and civil society.
The Chairman. Dr. Christy, you will have the last word from
Dr. Christy. OK. I just want to say ``Amen'' to something
Dr. Watson said. In my experience as an educator in Africa, the
educational component was the key ingredient to seeing those
societies bring about a better situation in the lives of the
people, and I just wanted to echo the need for education of
women in those countries.
The Chairman. Thank you very much.
Senator Kerry. Thank you, Mr. Chairman.
Senator Kerry [presiding]: It seems to me that there is
pretty broad agreement among you, not withstanding the
differences, Dr. Christy, in your assessment of what you are
willing to conclude from the satellite observations.
You have a differing of opinion about what the consequences
of global warming may be, but you do accept the fundamental
premise of the human impact and the basic findings of the
increase of warming taking place.
And I take it that these circumstances have serious
implications for us involved in policymaking. You do not think
we should do nothing, do you?
Dr. Christy. In terms of policy, I am not an expert, but--
Senator Kerry. Well do you think we should let CO2
double? Should we just sit around and watch this happen? Is
that your policy recommendation?
Dr. Christy. If I were to predict, I would say it was going
to double no matter what policy is adopted.
Senator Kerry. Realizing it is, would you simply sit back
and accept that, or would you now begin to do greater research
and see what----
Dr. Christy. I would certainly support, especially in terms
of energy use, research on the alternatives that can be used to
produce energy, and keep it cheap and affordable, because cheap
energy means longer and better lives.
Senator Kerry. So are you saying, about this process--I
mean, here are four distinguished peers of yours----
Dr. Christy. And I feel surrounded sitting here.
Senator Kerry. Well, it is hard to find a whole lot of
contrarians now. There are a few more but it is hard to find it
is hard to fill a room with them. How many people are on the
IPCC? 2,500, is it?
Dr. Trenberth. There are several hundred as authors. There
are several thousand, indeed, involved as reviewers. And indeed
John is one of them, and so is Richard Lindsen, who is also a
Senator Kerry. Is there a great difference of opinion
between those 200?
Dr. Watson. I think the majority see the climate issue the
same way. They all recognize what is known. They all recognize
what is unknown.
I would say there are a half a dozen key contrarians, which
include Dick Lindsen, Fred Singer and Pat Michaels, but I would
say the large majority of the scientists clearly fall on one
And in the IPCC, we are trying desperately to make sure the
full range of views is fully exposed. And so we can actually
say what is known with certainty, what is less known, why do
the majority think one way, and the minority think another. So
we can actually explain what the implications of uncertainties
are for policy formulation.
Senator Kerry. Dr. Trenberth, what is your sense of the
schools of thought here, and how we should come up? What is the
difference between these four or five that have been mentioned
as the key contrarians and the vast majority who believe
Dr. Trenberth. I think we need to take into account some of
the ideologies that come into play and recognize that there are
different views of the world.
In the IPCC process, particularly in working group one,
what we try to do is to make the best statement as to what can
be said about this problem of global climate change and leave
to the politicians what should actually be done about it. And
often, I think, those things do get mixed up. And they often, I
think, get mixed up by some of those people.
We need to recognize that there are many value systems in
the world today, from the extreme environmental position, which
says we should stop the increases in greenhouse gases
absolutely and mitigate the problem; to people who say
technology will solve the problem, and we can just adapt to it
as it goes along; to people who advocate sustainable
development; to people who have vested interests.
And we have seen this in the tobacco industry, for
instance, where often the strategy is to denigrate the science
and to say that there is not a problem and recognize that they
do have a vested interest. I do not think it is so much what
you do about the problem, but how you do it and doing it over
an appropriate time scale, that would help to assuage some of
the projections that you see.
Senator Kerry. Well, it is completely fair and, I think,
accurate to say, that some of the denigration of science has
emanated from specific industries highly vested in fossil fuel.
Is that accurate?
Dr. Trenberth. That is, I believe, accurate.
Senator Kerry. Is that accurate, Dr. Mahlman?
Dr. Mahlman. I think it is accurate, but I would answer a
little bit differently, in that if you look at this problem
worldwide, there are people who are trying to frame-out the
science the best that we know.
Some of the issues we have just discussed here are ones
where we can sit around at a table and discuss in a civil way
and say, ``Well, I disagree with you here or there,'' and we
would all go out to lunch together, and there would be no
yelling, or screaming or slugging going on.
Dr. Mahlman. But on the other hand, I think it is important
for all of us to recognize that there are contrarians and there
are also exaggerators. OK? And both are essentially, in my
view, making points because of agendas that are somewhat
independent of scientific analysis, and you can say, ``Well, I
do not see that as necessarily a new phenomenon on Capitol
Hill.'' But it----
Dr. Mahlman [continuing]. Is part of human nature to have
people torque the facts a little bit to hustle whatever their
position is. And, as you know, they say, ``That is part of the
policy debate,'' but it is also part of the values conflicts
and everything else.
I have gotten so that I do not get all that concerned about
it, because I think it is part of the process of dealing with a
problem that is extraordinarily difficult. Lots of folks see
that a very special thing is going to get hurt by mitigation or
is going to get hurt by climate change. I thus consider this to
be the real greenhouse warming controversy.
Senator Kerry. Governments came together in Kyoto to adopt
a policy, a response, and hopefully this policy does not
represent grinding of a particular axe, but represents a
reasonable approach in the middle. I do not think the Chairman
or I or others want to adopt a policy we do not need to adopt.
I do not have any industry axe to grind on one side or the
other. I mean, I am trying to respond to what I see is a
problem caused by human beings, which is increasing because of
our unwillingness to reduce what we are doing that is causing
it. Now, we have got to make a decision, because there is some
money involved here. Do we need to reduce the level of
emissions or do we not? Countries signed on in Kyoto to the
notion that we do; that reducing emissions is a worthwhile
goal. Does anybody disagree with that? Is it a worthwhile goal?
Dr. Mahlman. I would like to comment. I was quoted in the
New York Times before the Kyoto Conference. And I have written
a paper in Science Magazine, you know, prior to Kyoto.
At that time, I said that the best Kyoto could do would be
to set up a small, but significant decrease in the rate of
increase of carbon dioxide in the atmosphere. And, this
statement was somewhat controversial at the time. But the whole
point was, that even Kyoto itself, if it were fully
implemented, would still be nipping around the edges.
Senator Kerry. Absolutely.
Dr. Mahlman. And I said this not to demean the Kyoto
process, but more or less to educate people that are probably
going to be whittling away at this problem for the rest of the
century. And Kyoto is kind of ground-zero, or maybe Rio was, of
the process of what the world is going to do about it and how
all of the hard issues can get worked out.
And so, therefore, Kyoto, from the point of view of the
problem, was a very small step; not a radical, the world is
going off the edge if we implement the Kyoto Protocol. And so,
the next question is, what will happen in the next round?
Senator Kerry. Does anybody else want to add to that? Dr.
Bradley, and then Dr. Watson.
Dr. Bradley. I think it is clearly--there is a long ladder
we have to climb. And Kyoto is, perhaps, just the first rung on
that ladder, but it is an important step, because it forces
governments throughout the world to recognize the problem and
to take steps to address the problem.
It is not going to solve the problem, but it--but just like
the Montreal protocol, which began small and gradually made
stronger and stronger steps, I think that is what is necessary
Senator Kerry. Dr. Trenberth.
Dr. Trenberth. Well, the Kyoto Protocol is flawed, at least
in some respects, especially insofar that it is not truly
global, in terms of the agreements that exist.
The important thing about it is that it would buy time. The
estimate is that doubling of carbon dioxide would be delayed by
about 10 years. And people then ask, ``Is it worth buying that
And I think it, very strongly, is, because the climate is
going to change, and every step we can take to buy that time
provides us with better capabilities of planning for what is
going to happen and for planning the adaptation that will be
necessary to occur in the future.
And so, I think it is a desirable first step, even if a
flawed first step.
Dr. Watson. Yes. I think it is quite clear that governments
from around the world recognize that human induced climate
change is a threat to society. And what we need is some first
steps toward meeting the ultimate objective of the convention,
which is Article Two, which calls for the stabilization of
greenhouse gas concentrations in the atmosphere.
They also recognize, and I agree, that it is very important
to differentiate the responsibility between developing and
developed countries. Energy is needed to alleviate poverty in
developing countries and for having economic development.
But why is the Kyoto Protocol such an important first step?
It will stimulate the development of new energy technologies.
It will stimulate policy reform, both in developed and
developing countries. We will find better mechanisms, which
will involve all sectors and an appropriate enabling government
framework for technology transfer. And it will give us the
chance to put these flexibility mechanisms in place.
So, even though it is not a global convention, it does
recognize, just like the Montreal Protocol did, that the
developed world has the institutional, financial, and technical
capability to take the first steps.
As they take those first steps, we will see a flow of
technology transfer, such that it will be in the best interest
of China and India to also reduce their greenhouse gas
emissions, and simultaneously to reduce their local air
pollution and regional air pollution.
So, I believe it is a very well founded first step, but
clearly, at the end of the day, all countries will have to
reduce their greenhouse gas emissions, if we are going to meet
the ultimate objective of Article Two. There is no question.
Senator Kerry. Well, I agree with that. I accept that. I
think that the difficulty is that the current political
formulation in the United States makes it difficult for us to
embrace that first step, absent at least an acknowledgment by
the developing countries that they are willing to adopt some
measures. Tackling the problem is going to be very complicated.
You know, I was involved and I led the fight on the floor
to try to create some sort of rational approach in the Herd-
Engle Amendment. And I am sympathetic to the notion that people
in the United States are going to be hard-pressed to buy into
something they do not see other people also buying into.
The fact is, though, that China and other developing
countries are currently embracing significant steps to achieve
clean air. And they are moving forward. In China, for instance,
they are restricting certain kinds of vehicles, and are
beginning to get conscious of these environmental issues. And
they could actually qualify for participation very easily,
based on many of the things they are doing now.
What we have is a dividing line between us--the traditional
view of the developed (and developing) world. We have gotten
stuck in cement for lack of people's willingness to really look
at the long-run here. And I think we need to have some
significant diplomacy exerted in order to try to pull us
together now. We should not be that far off.
But let met just touch on a couple of other quick points. I
know Senator Brownback wants to ask questions.
Just for the record, the 400,000 year basis that you are
drawing conclusions on CO2 increase from is based on
the ice core, correct.
Dr. Bradley. These are little bubbles of gas; essentially
samples of the atmosphere that have been trapped in the ice and
buried for years.
Senator Kerry. I just want the record to reflect that I
have read it and I am familiar with it. I want the record to
reflect the accuracy of that judgment showing that it is not
some kind of hypothesis.
You are able to take trapped CO2 through the ice
cores, through the ice that has been there through these
millennia, and measure precisely the level of CO2
increases over that period of time, correct?
Dr. Bradley. That is correct.
Senator Kerry. And that is how we know to a certain degree
the demarcation point of the Industrial Revolution and the
introduction of CO2 by human industrial efforts that
has made this marked increase.
Dr. Bradley. That is correct.
Senator Kerry. We can track precisely the level of weather
changes, heat changes over the last 105 years, at least, by
measuring the CO2 gas in these cores.
Dr. Bradley. That is right. I might also add that this
420,000 year limit is only because that is as long an ice core
record as we have. I am sure if we had a 2 million year ice
core record--I feel confident that if we had a 2 million year
ice core record, we would still be heading toward uncharted
waters in the future.
Senator Kerry. Now, they also know that these things called
``sinks'' or entities that sequester carbon dioxide are
ineffective on a constant basis. But the ocean is also a
primary sink, correct? It is a huge sink.
And the ocean, in fact, is warming. And the ocean contains
very significant amounts of CO2 that it holds onto
for long periods of time. It is my understanding that the ocean
could conceivably have some limit as to how much CO2
it, in fact, can sequester.
And at some point, if we were to continue to pour it in, we
could have overload, so that all of a sudden the ocean is no
longer available as a major sequesterer of CO2,
Dr. Bradley. That is correct.
Senator Kerry. And that could then have a profound impact,
in terms of all of a sudden releasing this CO2 The
benefits of this once extraordinary sink are then negated. And
where do we go from there, is a legitimate question, is it not?
Dr. Bradley. Yes. There are a number of these kind of
thresholds in the climate system that we do not have a good
handle on. And that is one, for sure. And changes in the ocean
circulation, in general, are a great uncertainty.
Senator Kerry. And our weather in the northeast is
significantly dependent on the ocean, on the Gulf Stream and on
Dr. Bradley. That is right.
Senator Kerry. So, if that were to simply be altered in a
major way, we could have--who knows what--perhaps some
Dr. Bradley. Yes. That is true in most parts of the world,
wherein you have the economy and society has developed based on
what they are used to.
Senator Kerry. Given that reality, we make judgments here
everyday about flood plain settlement, about AIDS--the rate of
spread of AIDS, about tobacco. We have spent $60 billion in the
last few years, based on judgments we make about potential
threats from North Korea or Iraq or Iran.
Here is a far more realistic, in my judgment, and definable
quantifiable threat. And we are not even doing an adequate
level of climate change research.
Dr. Bradley. Exactly. In fact, I would say, that we can
carry on doing research. It is a trivial amount of money in the
context of what we spend on other things, but what is really
needed is a massive national effort to develop alternative
energy sources to find non-carbon based fuels that will allow
us to continue our economic progress without continuing to
increase the level of CO2 in the atmosphere.
Senator Kerry. But is it not true that, in fact, we are
much further down that road than most Americans know, with
respect to hydrogen, engine fuels or other alternatives?
Dr. Bradley. I am not sure where we are, but wherever we
are, we are not far enough along. Certainly, on the global
scale, this is a critical issue.
Senator Kerry. My point is, simply, that in 1980, before
President Reagan arrived in Washington, we were the world's
leader in alternatives and renewables. And we had created an
energy institute out in Colorado, I believe. And professors
left their universities and gave up tenure to go out there, and
research the American future in renewable and alternative
In 1981 the funding was cut completely. And we gave up our
leadership to the Japanese and Europeans in those sectors, so
that when the Communist block countries fell and they started
searching for people who had the technology, they looked
elsewhere than the United States.
Dr. Bradley. That is exactly right.
Senator Kerry. Now, I do not think this is as complicated
as we make it. The threat may be enormous, but the truth is, if
we were to unleash the technological capacity of this country
to truly face this problem--we have an extraordinary capacity
to develop jobs and economy and a future that is sustainable.
But it seems to me that we need to face the difficulties of
educating the public and drawing the people into the potential
Problems are real, but solutions are there. We can
certainly work through this, I think, providing we show some
Does anybody else want to make a comment?
Dr. Watson. Yes. I would like to make one comment on it.
Technology is very important and R&D is important, but the
policy framework is crucial.
We are never going to get renewable energies to penetrate
the marketplace unless we internalize the social costs of
pollution, for example air pollution and acid deposition, and
eliminate fossil fuel subsidies. It is worse in other countries
than the U.S.A. But it has to be a combination of research and
development into new energy technologies and policy reform.
There is no way that one is ever going to get renewable
energies in most countries, because of the subsidies on fossil
fuels and they subsidize the railways to transport coal, and
they do not internalize the social costs of environmental
So, we do not have a level playing field. It does not
matter how well you do on technology. So, it must be the
combination of technological development and policy reform.
And the comment that should be made is, unfortunately, both
public sector and private sector research in energy has
decreased in every country in the world, except for Japan. And
90 percent of their research is on nuclear power, not on
In most of the European Union, energy research has dropped
by a factor of five to ten. And in the U.S., in real terms, it
has also dropped. And most of the U.S. money goes into, again,
fossil fuels and nuclear power. Only 20 percent of the energy
R&D budget goes into either renewable energies or energy
And the other problem that compounds this, is that not only
has public sector research dropped off, but because of
deregulation of industries and liberalization, private sector
research has dropped even further. And so, we have the
unfortunate situation of both public and private research
We do not have the associated policy reform. And so, while
we have been debating climate change at the convention and the
Kyoto Protocol, the very instruments we need to enact a
decarbonization of the energy system have actually been taken
away from us.
Senator Kerry. Well, with respect to that policy, let me
just add, I am a passionate and deeply committed advocate of a
much more thoughtful foreign policy, where we, in fact, have a
much more significant component of technology transfer and
And a year ago, I managed to get Jim Wilbinson, to his
enormous credit, to commit the World Bank to holding the
conference in, of all places, Hanoi, Vietnam. It is about
precisely this kind of development.
And all the donor countries came, including Japan, to think
about how, as they need to put in a power plant, we could
provide them with an alternative to simply burning high-sulphur
coal. We could even provide them with direct grant transfer of
some of our technological abilities to be able to do these
things, so that they can develop without repeating the mistakes
that we have made, and learn, at the same time, that this is
not a Western conspiracy to keep them from sharing in the
abundance and wealth of the world, which is the way they view
I concur with you that we desperately need to have a change
in policy and a much more thoughtful approach to this. I thank
you for your comments today. And I thank my colleague for his
forbearance, and look forward to continuing this dialogue with
Senator Brownback [presiding]. I want to thank the panel
for the presentation. It was excellent. I thought it was very
And it reminded me just--in looking at how much everything
is interconnected. When you do one thing, and it just moves 100
different things, different places. I guess the philosopher
says that you pull on one place in the universe and everything
else moves. And it just really is interconnected.
Let me ask you--Dr. Bradley, you have already started to
articulate some of this, about what you think the policy moves
are that we should do today. Renewable energy sources, I think,
is what your primary focus is.
Are there other specific policy recommendations outside of
implementation of the Kyoto Treaty or the renewables that you--
some of you would like to put on the table that we should start
to discuss now in the U.S. Congress?
Dr. Bradley. I'm not convinced that renewable energy is
going to be the solution, but I think one of the simplest
things is conservation. And by that I mean using more energy-
efficient processes, whether that process is heating a house or
keeping the heat from going out of the roof; heating water;
obviously, more efficient automobiles, and that goes for trucks
and public transportation, too.
Those issues can be--can be encouraged with tax credits. As
I recall, the Carter Administration there were--they introduced
tax credits for energy conservation measures. And that was a
boost to a whole emerging economic sector, which was the
development of these products.
And it seems to me that would be a fairly painless way of
encouraging energy conservation, by providing significant tax
credits for people who buy cars that get more miles per gallon,
people who introduce energy-efficient measures to their homes,
et cetera. And that, in turn, would generate economic activity
that could be transferred to other countries. And so, it would
be a boost to our economy.
Senator Brownback. Dr. Trenberth.
Dr. Trenberth. I mentioned before that it is not so much
what you do, as how you do it. One of things which was
mentioned by Dr. Watson was the importance of taking into
account the lifetimes of the infrastructure that exists and
planning appropriately. And I think that is very important.
A good example might be, for instance, automobiles. If we
were to increase the cost of gasoline by a dollar tomorrow--
well, firstly, that would not be politically viable. And
secondly, it would cause major problems in the whole of the
economy; very disruptive. But if we increased the cost of
gasoline by a penny, it would be lost completely in the noise.
So, what would happen if we increased the cost of gasoline
by a penny every month? After 10 years, we would have $1.20
increase in the cost of gasoline. In fact, even then, the cost
of gasoline in the United States would be much less than it is
in Europe and in most other places around the world.
But if we did that and it was a certainty that it was going
to happen, then because the lifetime of a car is less than 10
years, the next time people went to buy a car, they would think
twice about the energy-efficiency of the car that they are
And it is this kind of thing that would enable people to
plan ahead in a reasonable fashion and adapt to the changes in
tax policy. And of course, you can use the increases in taxes
to offset other taxes, so that it is tax-neutral. This kind of
activity is the kind of thing which I think emphasizes the
point I make in my comment that it is not what you do, it is
how you do it.
Dr. Watson. Yes. I think one needs to look at all facts of
this. There is no simple home run here. One needs to look at
the technology on both energy supply and energy demand. So,
efficient vehicles, efficient housing, and more efficient
industry can help.
On energy supply, you can have more efficient use of fossil
fuels. It does not mean the elimination of fossil fuels--more
efficient production of energy from fossil fuels.
You can have fuel switching, from coal to gas. One should
think renewable energy.
The policy issues are very, very important policy reform.
There is no question. And Kevin is absolutely right. We must do
this in the economically least disruptive manner, which means
we need a long-time perspective.
Just like the sulphur market, when there was a decision by
Congress to reduce sulphur emissions in the U.S. The most
important thing they did, did not actually involve new
technologies, but it was the emissions training system that was
put in place.
So, one could actually stimulate a market--in this case, on
carbon--so that both domestically and internationally, you can
buy and sell carbon as a commodity. That will absolutely drive
down the price.
So, one needs to look at both the technology, but also the
policy framework. And I think that one should--and of course,
as you, yourself, have mentioned, I think there is a
significant opportunity through better forest management,
better agricultural management, better rangeland management.
And so, again, thinking through the policies that might
stimulate the farmer to move toward no-till agriculture. What
do we do with some of the degraded lands? It could actually be
very useful land for either afforestation or reforestation or
just simply to improve soil carbon. We must not lose the
potential in soil carbon.
My view would be, do not move for one simple home run
solution, but look right across the wide variety of options,
both in technologies and in policies.
Senator Brownback. Dr. Watson, when you look
internationally on the issues of carbon sequestration in the
construction of the--some of the forests in areas, do you think
that that is a key component of--as well as to look at this
issue, or is it not a major issue?
You have mentioned the complexity of this and the
multifaceted solution that is going to be required, if we are
going to try to pull more carbon out of the atmosphere.
Regardless of how it got there, regardless of what may be some
of its impact in the future, we want to get some of this
CO2 out of the atmosphere. And we could, I think,
most would agree on that.
What do you see, as that component of it on the
Dr. Watson. Today we put about 6.3 billion tons of carbon
per year into the atmosphere from using energy. And from
tropical deforestation, we put somewhere around 1.8 billion
tons of carbon per year. So, from a total of 8.1, 25 percent
comes from tropical deforestation.
Therefore, slowing tropical deforestation is a major
component to acting to protect the earth's climate system. It
would also have incredible benefits to the biodiversity and
water resources in those regions. But it is unbelievably
I chaired the recent IPCC report and part of my testimony
is on land use, land use change in forestry. And what we see
from many developing countries--and this is a political, not a
scientific issue--is that they are willing to think through
issues of afforestation and reforestation, and issues such as
But Brazil, in particular, is absolutely opposed to
including avoided deforestation into the Kyoto Protocol through
the Clean Development Mechanism Article 12. It is a political
issue. It has to do with the Federal/state government
relationships, that is to say the interplay between the Federal
Government and the state governments in Brazil. It is a
question of whether or not, if you avoid deforestation in one
part of Brazil, it will accelerate it in another part of
So, you have to understand the drivers behind
deforestation, in order to say that you can actually stop
deforestation. You need to know all the underlying political
and technical and industrial factors that drive it.
But there is no question in my mind that if we can slow
deforestation in the tropics, and if we can accelerate
afforestation and reforestation, both in the tropics and high
latitudes, it would be a major contribution to climate change
and to save the world's biological diversity.
Senator Brownback. On the afforestation and reforestation,
would we not actually affix or sequester more carbon if we--if
our policies actually focused in that direction, avoiding some
of the political issues that you have identified?
Dr. Watson. Yes. On afforestation or reforestation--forests
grow slowly, but surely, over the next 20, 50, 100 years,
depending on the lifetime of the forest, you would sequester
carbon. And there is no question it is a very good thing. But
if you can avoid deforestation, it stops a big slug of carbon
going into the atmosphere.
And of course, if one is trying to avoid deforestation in
the tropics, one could argue there are national sovereignty
issues at stake, as well.
I think we need the dialogue right across the world on all
of these issues simultaneously. We have got to recognize
political sensitivity, but we also need to recognize that
avoiding deforestation is a powerful tool to keep the carbon
where it is.
Afforestation and reforestation will draw additional carbon
from the atmosphere, but avoiding deforestation stops it going
in, in the first place.
Senator Brownback. Dr. Trenberth.
Dr. Trenberth. Senator, you were asking especially about
the sequestration of carbon dioxide, and there is also new
technology, and I believe Norway is the leader in this area,
where they are taking carbon dioxide out of the atmosphere as
it is generated, essentially, and then the technology is to
sequester it in the oceans or elsewhere.
I am not an expert in that area, but I did want to get on
the record that there are, indeed, other technologies, but of
course there is a cost attached to doing that.
Senator Brownback. Other policy suggestions, or
particularly in the carbon sequestration is a--I think that
is--that is a key point of political reality. And one needs to
recognize political reality, you know, here, as well.
We can probably spend a great deal of time arguing about
how global warming is occurring. We could probably spend and
probably will spend a lot of political time discussing, OK,
whether Kyoto is a good or bad treaty for us to enter into. And
then you are going to have the political forces that will line
up both ways on that. And those are legitimate debates and
discussions, and which you are going to have them in.
You could also start to do something right now. And you
could recognize what the market will bear here and what we can
start to do, which is, in my way of thinking, probably what we
ought to be--perhaps we can, first and foremost, starting with
now, because it starts to eat away, as one of you said--I think
it was Dr. Mahlman.
He pointed out that even Kyoto just kind of nips around the
edges of this. ``And we will probably be doing that for the
next century,'' was the quote of one of you.
I think there are ways that we can get started on this. I
think we will need to have the dispassionate dialogue and
recognize people's concerns and political realities, and then
say there are ways that we can actually--we can move forward
and start to address the problem now, rather than just having
the issues back around.
Recognizing that that is probably the start of a lengthy
process of how do we deal with issues like this in ways that
are least disruptive.
Dr. Watson. If one simply makes carbon a commodity, just
like maize or wheat is, then there is real value in carbon. And
that is how you can then trade carbon either within a company
as British Petroleum is doing now. You can trade it nationally
within the U.S. or any other country, like we trade sulphur at
the moment. And it can be traded internationally.
As soon as you make carbon a commodity and it has value,
then it will be a real incentive to farmers, it will be a real
incentive to foresters, to improve agricultural practices,
forestry practices, essentially be paid for those better
management practices, and then also get the multiple benefits
of increased soil fertility, et cetera.
So, one of the challenges is putting a policy framework
together, where one has real value in carbon and will also
stimulate research and development and will also stimulate
energy-efficient technologies. There is no question, that the
challenge is putting the framework together.
Dr. Bradley. If I could just pick up on a point there, and
that is that many of these strategies do have multiple
benefits. Bob talked about the preservation of biodiversity
in--clearly, it will be more beneficial to the economy if we
use less fuel to power our automobiles, power our plants and so
It is going to be better, ultimately, if we can do things
more efficiently like that. So, we ought to develop sort of a
table of strategies that have the least political disagreement
and the maximum collateral benefits that we can imagine, so
that we can start chipping away at this very large issue by
taking some of these measures.
Senator Brownback. It is picking the low lying fruit as
best you can.
Thank you very much. You have been an excellent panel and
an excellent discussion. I know the Chairman would like to hold
additional hearings on this. And I think it certainly is
The record will remain open for the requisite number of
days, if you choose to submit additional things for the record.
The hearing is adjourned.
[Whereupon, at 12:15 p.m., the hearing was adjourned.]
A P P E N D I X
Article Written by Dr. Jerry Mahlman, Director, Geophysical Fluid
Dynamics Laboratory, National Oceanic and Atmospheric Administration
Science Magazine, November 21, 1997
Uncertainties in Projections of Human-Caused Climate Warming
Mankind's activities have increased carbon dioxide (CO2)
in the atmosphere. This increase has the potential to warm the earth's
climate by the ``greenhouse effect'' \1\ in which CO2
absorbs infrared radiation and then re-radiates it back toward the
surface of the planet. Other gases also act as greenhouse gases and may
warm the climate even further,\2\ although human-produced airborne
sulfate particles can cause cooling that offsets some of the
warming.\3\ Computational models that include these factors predict
that the climate will warm significantly over the next century.
\1\ The greenhouse effect for CO2 was first calculated
over 100 years ago by S. Arrhenius, The London, Edinburgh and Dublin
Philosophical Magazine and Journal of Science 41, 237 (1896).
\2\ Intergovernmental Panel on Climate Change, Climate Change, the
IPCC Scientific Assessment, J. T. Houghton et al., Eds. (Cambridge
Univ. Press, Cambridge, 1990).
\3\ Intergovernmental Panel on Climate Change, Climate Change 1995,
The Science of Climate Change, J. T. Houghton et al., Eds. (Cambridge
Univ. Press, Cambridge, 1996).
These forecasts of likely climate changes have forced a realization
that it is necessary to reduce human-caused emissions of greenhouse
gases. But because of the potential social disruptions and high
economic costs of such reductions, vigorous debate has arisen about the
size and nature of the projected climate changes and whether they will
actually lead to serious impacts.
A key element of these spirited--and often acrimonious--debates is
the credibility (or lack thereof) of the mathematically and physically
based climate models \4\ that are used to project the climate changes
resulting from a sustained buildup of atmospheric CO2. Some
skeptics ask, to put it bluntly, why should we believe such models'
attempts to describe changes in such a dauntingly complex system as
Earth's climate? The cheap answer is that there are no credible
alternatives. But the real answer is that the climate models do a
reasonably good job of capturing the essence of the large-scale aspects
of the current climate and its considerable natural variability on time
scales ranging from 1 day to decades.\4\ In spite of these considerable
successes, the models contain weaknesses that add important uncertainty
to the very best model projections of human-induced climate changes.
\4\ Climate models are mathematically based models that attempt to
calculate the climate, its variability, and its systematic changes on a
first-principles basis. The fundamental equations solved are the
conservation of mass, momentum, and energy. The interactions among the
atmosphere, ocean, ice, and land surface systems are calculated on
rather widely separated computational points on Earth (typical spacings
are 200 to 400 km in the horizontal and 1 to 3 km in the vertical).
I express here a ``policy-independent'' evaluation of the levels of
current scientific confidence in predictions emanating from climate
models. This climate model uncertainty is distinct from the high social
uncertainty associated with future scenarios of greenhouse gas and
airborne particle concentrations. I assume that detailed future
greenhouse and airborne particle scenarios are part of the policy
question and thus do not discuss them further.
A fair-minded and exhaustive attempt to find a broad consensus on
what science can say about this problem is contained in the most recent
1996 IPCC Working Group I Assessment.\3\ Some of my evaluations differ
in detail from those of IPCC 1996, mostly because of the addition of
new research insights and information since 1994. A good guideline for
evaluating contrary ``expert'' opinions is whether they use the IPCC
science as a point of departure for their own analysis. In effect, if
we disagree scientifically with IPCC, we should explain why. Without
such discipline, contrary arguments are not likely to be scientifically
Virtually Certain ``Facts''
These key aspects of our knowledge of the climate system do not
depend directly on the skill of climate model simulations and
Atmospheric abundances of greenhouse gases are increasing
because of human activities.
Greenhouse gases absorb and re-radiate infrared radiation
efficiently. This property acts directly to heat the planet.
Altered amounts of greenhouse gases affect the climate for
many centuries. The major greenhouse gases remain in the
atmosphere for periods ranging from a decade to centuries.
Also, the climate itself has considerable inertia, mainly
because of the high heat capacity of the world ocean.
Changes in other radiatively active substances offset
somewhat the warming effect of increased greenhouse gases.
Observed decreases in lower stratospheric ozone and increases
in sulfate particles both produce cooling effects. The cooling
effect of sulfate particles remains insufficiently quantified.
Human-caused CO2 increases and ozone decreases in
the stratosphere have already produced more than a 1+C global
average cooling there. This stratospheric cooling is generally
consistent with model predictions.
Over the past century, Earth's surface has warmed by about
The natural variability of climate adds confusion to the
effort to diagnose human-induced climate changes. Apparent
long-term trends can be artificially amplified or damped by the
contaminating effects of undiagnosed natural variations.
Significant reduction of key uncertainties will require a
decade or more. The uncertainties concerning the responses of
clouds, water vapor, ice, ocean currents, and specific regions
to increased greenhouse gases remain formidable.
I further illustrate these climate uncertainties using two
extrapolations of the IPCC idealized scenarios of increases of 1%
equivalent atmospheric CO2 concentration per year.\5\ The
first case levels off at a CO2 doubling after 70 years; the
second levels off at a CO2 quadrupling after 140 years. Both
correspond to simple extrapolations of current trends in greenhouse gas
emissions. Considering the long residence time of CO2 at
such large concentrations, these leveled-off scenarios are physically
plausible but are presented as illustrations, not as social
\5\ S. Manabe and R. J. Stouffer, Nature 364, 215 (1993); J. Clim.
7, 5 (1994).
Virtually Certain Projections
These projections have a greater than 99 out of 100 chance of being
true within the predicted range: \6\
\6\ The approach used here was tested and challenged in E. Barron,
Forum on Global Change Modeling, U.S. Global Change Research Program
Report 95-02 (U.S. Global Change Research Program, Washington, DC,
1995). Earlier evaluations were published in J. D. Mahlman, Climate
Change and Energy Policy, L. Rosen and R. Glasser, Eds. (American
Institute of Physics, Los Alamos National Laboratory LA-UR-92-502, New
York, 1992) and in J. D. Mahlman, U.S. Congressional Record, 16
November 1995, House Science Committee Hearing on Climate Models and
Projections of Potential Impacts on Global Climate Change (1995).
The stratosphere will continue to cool significantly as
CO2 increases. If ozone continues to decrease, the
cooling will be magnified. There is no known mechanism to
prevent the global mean cooling of the stratosphere under these
Global mean amounts of water vapor will increase in the
lower troposphere (0 to 3 km) in approximately exponential
proportion (roughly 6% per 1+C of warming) to the global mean
temperature change. The typical relative humidities would
probably change substantially less, in percentage terms, than
would water vapor concentrations.
Very Probable Projections
These projections have a greater than 9 out of 10 chance of being
true within the predicted range:
The global warming observed over the past century is
generally consistent with a posteriori model projections of
expected greenhouse warming, if a reasonable sulfate particle
offset is included. It is difficult, but not impossible, to
construct conceivable alternate hypotheses to explain this
observed warming. Using variations in solar output or in
natural climate to explain the observed warming can be
appealing, but both have serious logical inconsistencies.
A doubling of atmospheric CO2 over preindustrial
levels is projected to lead to an equilibrium global warming in
the range of 1.5+ to 4.5+C. These generous uncertainty brackets
reflect remaining limitations in modeling the radiative
feedbacks of clouds, details of the changed amounts of water
vapor in the upper troposphere (5 to 10 km), and responses of
sea ice. In effect, this means that there is roughly a 10%
chance that the actual equilibrium warming caused by doubled
atmospheric CO2 levels could be lower than 1.5+C or
higher than 4.5+C. For the answer to lie outside these bounds,
we would have to discover a substantial surprise beyond our
Essentially all climate models predict equilibrium global
temperature increases that are nearly linear in the logarithm
of CO2 changes. This effect is mainly due to
increasing saturation of many of the infrared absorption bands
of CO2. That is, a quadrupling of CO2
levels generally produces projected warmings that are about
twice as large as those for doubled CO2.
Models predict that by the year 2100, global mean surface
temperature changes under these two idealized scenarios would
be 1.5+ to 5+C.
Sea level rise could be substantial. The projections of 50
25 cm by the year 2100, caused mainly by the
thermal expansion of sea water, are below the equilibrium sea
level rise that would ultimately be expected. After 500 years
at quadrupled CO2 levels, the sea level rise
expected due to thermal expansion alone is roughly 2
1 m. Long-term melting of landlocked ice carries
the potential for considerably higher values but with less
As the climate warms, the rate of evaporation must increase,
leading to an increase in global mean precipitation of about 2
0.5% per 1+C of global warming.
By 2050 or so, the higher latitudes of the Northern
Hemisphere are also expected to experience temperature
increases well in excess of the global average increase. In
addition, substantial reductions of northern sea ice are
expected. Precipitation is expected to increase significantly
in higher northern latitudes. This effect mainly occurs because
of the higher moisture content of the warmer air as it moves
poleward, cools, and releases its moisture.
The following have a greater than two out of three chance of being
Model studies project eventual marked decreases in soil
moisture in response to increases in summer temperatures over
northern mid-latitude continents. This result remains somewhat
sensitive to the details of predicted spring and summer
precipitation, as well as to model assumptions about land
surface processes and the offsetting effects of airborne
sulfate particles in those regions.
Climate models imply that the circum-Antarctic ocean region
is substantially resistant to warming, and thus little change
in sea-ice cover is predicted to occur there, at least over the
next century or two.
The projected precipitation increases at higher latitudes
act to reduce the ocean's salinity and thus its density. This
effect inhibits the tendency of the water to sink, thus
suppressing the overturning circulation.
Very recent research \7\ suggests that tropical storms, once
formed, might tend to become more intense in the warmer ocean,
at least in circumstances where weather and geographical (for
example, no landfall) conditions permit.
\7\ T. R. Knutson, R. E. Tuleya, Y. Kurihara, in preparation.
Model studies project that the standard deviations of the
natural temperature fluctuations of the climate system would
not change significantly. This indicates an increased
probability of warm weather events and a decreased probability
of cold events, simply because of the higher mean temperature.
Incorrect Projections and Policy Implications
There are a number of statements in informal writings that are not
supported by climate science or projections with high-quality climate
models. Some of these statements may appear to be physically plausible,
but the evidence for their validity is weak, and some are just wrong.
There are assertions that the number of tropical storms,
hurricanes, and typhoons per year will increase. That is possible, but
there appears to be no credible evidence to substantiate such
Assertions that winds in midlatitude (versus tropical) cyclones
will become more intense do not appear to have credible scientific
support. It is theoretically plausible that smaller-scale storms such
as thunderstorms or squall lines could become stronger under locally
favorable conditions, but the direct evidence remains weak.
There is a large demand for specific climate change predictions at
the regional and local scales where life and life support systems are
actually affected. Unfortunately, our confidence in predictions on
these smaller scales will likely remain relatively low. Much greater
fidelity of calculated local climate impacts will require large
improvements in computational power and in the physical and biological
sophistication of the models. For example, the large uncertainty in
modeling the all-important responses of clouds could become even harder
at regional and local levels. Major sustained efforts will be required
to reduce these uncertainties substantially.
Characterizations of the state of the science of greenhouse warming
are often warped in differing ways by people or groups with widely
varying sociopolitical agendas and biases. This is unfortunate because
such distortions grossly exaggerate the public's sense of controversy
about the value of the scientific knowledge base as guidance for the
policy deliberation process.
It is clear that much is known about the climate system and about
how that knowledge is expressed through the use of physically based
coupled models of the atmosphere, ocean, ice, and land surface systems.
This knowledge makes it obvious that human-caused greenhouse warming is
not a problem that can rationally be dismissed or ignored. However, the
remaining uncertainties in modeling important aspects of the problem
make it evident that we cannot yet produce a sharp picture of how the
warmed climate will proceed, either globally or locally.
None of these recognized uncertainties can make the problem go
away. It is virtually certain that human-caused greenhouse warming is
going to continue to unfold, slowly but inexorably, for a long time
into the future. The severity of the impacts can be modest or large,
depending on how some of the remaining key uncertainties are resolved
through the eventual changes in the real climate system, and on our
success in reducing emissions of long-lived greenhouse gases.
Response to Written Questions Submitted by Hon. John McCain to
Dr. John R. Christy
Question 1. You mentioned in your statement that 60 percent of the
atmospheric mass that was projected by computer models to warm
significantly has not. How significant is this 60 percent? Are you
saying that the claims of global warming are based on less than half of
the affected mass?
Answer. To the layman, global warming is something that happens at the
surface of the Earth, i.e. the surface temperature. Much has been made
about the fact the surface temperature has increased in the past 21
years. At the same time, the bulk of the atmosphere, from the surface
to 5 miles up, has experienced little change in that time. The
significance here is that all climate models show that with enhanced
greenhouse gasses, the surface temperature will rise and that the
deeper layer will rise even more. The fact this bulk-layer has not
risen indicates that the surface warming of the past 21 years is not
human-induced warming (if models are correct) or that the climate
system is not well-represented in the present models. I believe there
are significant shortcomings in the present models with regard to
distributing heat throughout the bulk of the atmosphere, and that this
may lead to predictions of surface warming that are too high.
Question 2. Your written statement has suggested that no model is
perfect because the weather system is incredibly complex. Furthermore,
you stated that the goal of models is to provide information on changes
in large-scale features. Given the increases in computing power, can we
ever expect to have models provide information on smaller scale
Answer. I do not see, with either improved computing power or with
improved models, the ability to predict with confidence what the
climate will be in specific regions. At this point we are unable to do
so for the next ten days, much less for the next ten years or next ten
decades. Since local precipitation is more critical than temperature
for human and other biological systems, predictions of changes in
rainfall would be of great value if we could have confidence in them.
However, the present set of climate models predicts a range of
precipitation changes in any given region so wide (e.g. much more,
more, same, less, much less) as to be of no use for policy decisions.
Thus, establishing regulations that increase the cost of energy to
people (with a greater impact on poorer people) will be done so to deal
with a ``global average,'' for which the local impacts are essentially
unpredictable. Even so, reductions in CO2 through regulation
will be so tiny as to have microscopic effect on the global average
temperature. A global economic depression (with associated loss of
living standards, health, security etc.) would most likely do more to
reduce CO2 increases than regulation. Even this would have
relatively no impact on the path of the present global average climate.
Question 3. Your written testimony referred to a recent report which
stated that January through March of this year was the hottest ever
recorded. The satellite data showed that the atmospheric temperature
above the U.S. mainland was indeed higher than average. However, most
of the globe experienced lower than average temperatures. Does this
suggest that what we may be experiencing is not global warming, but a
shifting of the temperature patterns?
Answer. The key point here is that the news media broadcast widely the
report of ``warmest ever'' surface temperatures over the lower-48
states. This was then linked as evidence to human-induced global
warming. The global picture, however, indicated the warm temperatures
over the U.S. were only part of a typical weather pattern that has
alternating regions of warm and cold. The U.S. was in a very warm spot,
but most regions experienced cooler than average tropospheric
temperatures (see map in written testimony). Thus, the lower-48 (2
percent of the globe) was not representative of global temperatures,
and the global temperatures were not showing global warmth.
Question 4. Your written statement acknowledged that in the past 100
years, sea level has risen 6 inches (plus or minus 4 inches) and is not
accelerating. You further stated that for the Gulf Coast, a rise of 6
inches over 100 years is minuscule. Can you elaborate on how minuscule
this impact would be?
Answer. For this question, we actually have a good source of
information--the real world. The sea level has risen 6 inches in the
past 100 years, and the ecosystems along the Gulf Coast have not
changed appreciably because of it. When sea level rises less than an
inch per decade, ecosystems can naturally adapt. It is important to
note that relative sea level is always changing as natural geologic
forces uplift some coasts and subsidence lowers other coasts. At the
sea level rates we are discussing for the global average, the change in
the volume of water in the ocean is often a smaller effect than the
other natural forces for a given location.
The stresses these coastal ecosystems do endure come not from sea
level rise, but from human development and human-generated pollutants
in river runoff. And, these developments are more and more in harms way
of the next hurricane which could have a storm surge (i.e. sudden sea
level rise) of 10 to 30 feet. This is the real danger for coastal
dwellers and economic infrastructure. Natural ecosystems have ways to
bounce back from hurricanes, but buildings and roads don't. What I tell
developers and other potential beach front property owners is ``If a 6
inch rise in sea level is a problem for you, you are too close to the
Response to Written Questions Submitted by Hon. John McCain to
Dr. Neal Lane
Question 1. Are there any areas within climate change research which
you would characterize as deficient? Is the federal government making
the right choices regarding which programs it should fund?
Answer. Our current understanding of climate change is the result of
significant successes in research over the last several decades, and,
as is often the case in science, that success has led to many new
questions. I would not characterize any aspect of our current climate
research effort as deficient, but it is certainly true that we need to
modify and enhance various aspects of our research effort in response
to new developments in science and new needs for information. As noted
in my testimony, the climate change debate has evolved from ``Are we
warming the Earth?'' to How much are we warming the Earth? and ``What
impacts will that warming have?'' The U.S. Global Change Research
Program (USGCRP) is benefiting from the advice in a number of recent
National Research Council reports, including, ``Global Environmental
Change: Research Pathways for the Next Decade'' as it addresses these
questions. A number of priorities have emerged from USGCRP
consideration of recommendations from the NRC and from other scientific
advisory bodies. The program is enhancing its efforts and revising its
strategies in a number of key areas, including carbon cycle research,
water cycle research, research on the impacts of climate change, long-
term climate observations, and high-end climate modeling.
The USGCRP established a Carbon Cycle Science initiative in the
FY2000 budget, focused on improving our understanding of carbon
dynamics in the environment, and we have continued strong support for
this in the FY2001 budget request. The FY2001 request also proposes
increases for water cycle research, long-term surface based climate
observations, and research to understand the ecological impacts of
climate change and other global changes. All of these topics will be
important areas in the new overall long-term research strategy that is
now being developed. We anticipate that a plan will be ready for review
later this year. My view is that the federal government is making the
right choices and that the programs we support are necessarily evolving
and changing as we learn more about the problems and phenomena we are
attempting to understand.
Question 2. Do you believe that the upcoming IPCC report will alter the
current debate among scientists or Congress? Will the report confirm
what we already believe to be true?
Answer. The Intergovernmental Panel on Climate Change (IPCC) produces a
comprehensive assessment of global climate change approximately every
five years. I do not think the work of the IPCC really alters or
changes the views of the scientific community on climate change. It is
more accurate to say that it describes these views, because the
scientific community produces IPCC reports. This is one of the reasons
they are so valuable. The process of creating IPCC assessment reports
certainly influences scientific debate and discussion over many aspects
of climate change, but I think it is important to note that the current
scientific debate on climate change is not over whether climate change
is occurring. It is rather over detailed projection of how much change
will occur, exactly how much of this change is due to various forcing
factors, and precisely what impacts change will have.
The upcoming Third Assessment Report, which is currently under
government and technical review, will be completed in early 2001. I
expect this report to confirm and reinforce the broad scientific
consensus that atmospheric CO2 has been significantly
increased by human activities, that the surface of the earth is
warming, and that the earth's surface temperature will continue to rise
during the next century. It will document the increase in understanding
that has occurred since the SAR was completed in 1995, and I believe it
will also confirm the assertion in my testimony that the research and
policy communities can now appropriately shift from a primary focus on
the physical systems of climate change to a broader effort to
understand how global change will affect the Earth's biological systems
and the human societies that are dependent on them.
Question 3. Do you believe that the U.S. Global Change Research Program
is achieving its full potential? What are the weaknesses of this multi-
agency program? Are they currently being addressed?
Answer. The USGCRP has been and is a successful program that can serve
as a model for broad multi-agency cooperation in addressing a
crosscutting research theme. Coordinating a complex research agenda
across a dozen diverse agencies of the federal government is difficult,
and it is critical that the Program evolves in response to changing
research priorities. With input from the NRC and the participating
federal agencies, a new long-term strategic research plan is being
developed for the Program.
Question 4. What are our national objectives for the modeling program?
Answer. Most global climate modeling research and application in the
United States is sponsored by NSF, DOE, NASA, and NOAA. These agencies
each have their own individual planning processes, but they have also
worked together to establish well-defined priorities consistent with
goals and objectives of the USGCRP.
As noted in numerous versions of ``Our Changing Planet,'' the
USGCRP modeling strategy calls for the use of the most powerful
supercomputers to accommodate evolutionary development and revision of
the climate models. An interagency group has established the Common
Infrastructure Initiative and has made progress in development of a
flexible national modeling infrastructure that will facilitate the
exchange of scientific advances and technology between climate modeling
and research and operational weather modeling groups. A USGCRP
Integrated Modeling and Prediction Working Group formally coordinates
the agencies' climate modeling research. This Working Group, which
reports to the SGCR, has reviewed and endorsed the various plans for
climate modeling activities and, in particular, the proposal for the
Climate Simulation Laboratory at the National Center for Atmospheric
Research (NCAR). In addition, the Advisory Board for the NSF-sponsored
Climate System Model at NCAR has been reconstituted to include
scientists and managers from DOE, NASA, and NOAA to reflect their
growing participation in the nation's only community climate model.
Two specific efforts are underway to develop a national strategy
for climate modeling, one by the National Research Council, and one by
the agencies. These are complementary efforts with overlapping
membership. Both are responsive to the recent Modeling report produced
by the National Research Council that identified problems in high-end
U.S. climate modeling capabilities. An important aspect of the USGCRP
agency effort is to determine how the climate modeling community should
focus its efforts and investments to best leverage the new capabilities
that will be developed through the Administration's Information
Technology Research (ITR) initiative to create more advanced
supercomputers and software.
Finally, an implicit requirement for an effective modeling program
is a robust observation system that can provide consistent, long-term
data on the many parameters of the climate system. Thus, a diverse
approach that supports modeling, observations, research and analysis,
and assessment is needed. Each of these activities relies upon and
informs the others.
Question 5. What are some of the lessons learned from the first
Answer. The ``U.S. National Assessment of the Potential Consequences of
Climate Variability and Change'' is now nearing completion. We have
learned a number of lessons related to process, research needs, and
potential impacts. Related to process, I want to be on record in
expressing sincere appreciation for the overwhelming support received
in this effort. Stakeholders were very forthcoming in sharing their
insights and concerns, which were critical in providing direction.
Individuals from academia, industry, and non-governmental organizations
demonstrated exceptional willingness to serve by volunteering their
time to be chapter authors, technical reviewers, and advisors to the
In terms of research needs, work on the Assessment revealed a
number of key priorities for further work. It became clear that we need
more basic knowledge about how natural ecosystems and managed
ecosystems such as agriculture and managed forests will respond to
changes in climate and in atmospheric CO2 concentration.
Since many of the resources and ecosystems that will be affected by
climate change, such as water and forests, are intensely managed, it is
crucial that we understand better how present and potential future
management practices could either compound or mitigate the effects of
climate change and other environmental stresses. Finally, since the
degree of impacts will inevitably depend on the actual rate and
character of climate change, it is important to continue working to
reduce uncertainties in our knowledge and projections of climate. This
will require further improvement in climate models and our
understanding of past climate variation, further development of methods
to refine regional-scale projections, and crucially, better
understanding of the socioeconomic drivers of potential climate change,
such as population, demographics, income levels, and energy use
Question 6. The National Research Council report entitled ``Global
Environmental Change: Research Pathways for the Next Decade'' stated
that the USGCRP must be revitalized, focusing its use of funds more
effectively on the principally unanswered scientific questions about
global environmental change. What has been the USGCRP reaction to this
Answer. As noted in my testimony and in the answer to question 1, the
USGCRP relies on input from both participating federal agencies and the
broader scientific community to set research priorities and devise
appropriate strategies for addressing critical issues. With guidance
from the ``Pathways'' report, USGCRP research has been organized into a
set of ``program elements,'' including a Carbon Cycle Science
initiative established in FY2000, and a Global Water Cycle initiative
included in the FY2001 budget request:
Understanding the Earth's Climate System
Biology and Biogeochemistry of Ecosystems
Composition and Chemistry of the Atmosphere
Human Dimensions of Global Change
Carbon Cycle Science
The Global Water Cycle
The ``Pathways'' report is also a basis for current efforts to
develop a new 10-year strategic plan for the USGCRP.
Question 7. Can you summarize how USGCRP has been meeting the
requirements of Section 104 of the Global Change Research Act of 1990
Answer. The creation of a comprehensive research plan was one of the
most important early tasks of the USGCRP. The 1991 edition of Our
Changing Planet had two volumes, one of which was titled Our Changing
Planet. The FY1991 Research Plan. This 250-page document was a detailed
and comprehensive scientific strategy for the USGCRP. The ongoing
consideration and revision of the plans set forth in this document has
been an important topic for the USGCRP agencies as they engage in their
yearly program planning and budget processes, and updates to these
plans have been included in the subsequent editions of Our Changing
The progress that has been made in many areas of global change
science, and the advice received in a number of major studies from the
National Academy of Sciences, including the Pathways report, has
resulted in a major effort to define a new long-term strategy for the
USGCRP. This process has been underway for several years, and we
anticipate that a draft will be submitted for public comment and NRC
review later this fall. The draft will cover all the areas outlined in
Section 104 of the U.S. Global Change Research Act.
Question 8. Given that USGCRP is ten years old, do you believe it's an
appropriate time for a new ten-year plan?
Answer. Absolutely. The process of review and program improvement is
continuous. The next important step in this process will be the
completion of a new long-term plan later this year. This plan will be
submitted to the National Research Council for review. The NRC
Committee on Global Change Research, the follow-on committee to the
``Pathways'' report, is working with the USGCRP agencies to construct a
reasonable schedule for review of progress in responding to the
recommendations of the Pathways report and the new long-term plan.
Response to Written Questions Submitted by Hon. John McCain to
Dr. Jerry Mahlman
Question 1. You mentioned in your statement that important
uncertainties remain due to deficiencies in our scientific
understanding and in computer power. Can you explain how an increase in
computing power will enable you to reduce some of the uncertainty in
Answer. Increases in computer power and increases in ability to process
very large volumes of data play an important role in reducing the
scientific uncertainty in understanding human-caused climate warming.
First, increased computational power allows the climate models to
resolve regional details far better. For example, today's long-running
atmosphere-ocean-climate models represent the entire state of Arizona
with one or two computational points. A factor of 10 increase in
computer power allows Arizona and its complex topography and climate
zones to have 20 or so points.
Second, it has been found advantageous to increase understanding of
computer model experiments by running multiple versions, each under
somewhat different circumstances. This allows a clearer view of what we
do and do not understand well.
Third, much of the remaining scientific uncertainty in this problem
arises from incomplete information about key physical processes, such
as clouds, turbulence, severe storms, complex land-surface biosphere/
climate interactions, etc. Greater computational power allows inclusion
of considerably more complete physical processes and their possible
roles in either decreasing or increasing our best estimates as to how
much or how soon significant warming will occur, and how specific
regions will be affected.
Fourth, greater computational power allows the major national
climate modeling centers to interact more productively with colleagues
in government, academia, and private industry, simply because more
experiments can be run at greater fidelity, with more talented
scientists evaluating the results from a wider range of perspectives.
Question 2. You mentioned that climate modeling efforts must receive
resources that are in balance with broader scientific programs. What
are your current funding levels and what level would you recommend?
Answer. The current total funding for NOAA's Geophysical Fluid Dynamics
Laboratory (GFDL) is about $22M in Fiscal Year 2000, of which $13M is
in base funds, and most of the remainder in HPCC/IT2 interagency
program funds. I believe it is fair to say that, thanks to a genuine
FY2000 and 2001 commitment from Congress, OMB, and the Department of
Commerce, GFDL's current supercomputer budget is in comparatively good
shape. A number of our respected U.S. colleagues have not been as
For example, in NOAA it has been much easier to obtain funding for
large hardware ventures (e.g., satellites, ground-based measurement
systems, and supercomputers) than for funding the scientific talent
required to achieve optimal value from these critical investments. Even
a 5% ``tax'' on these large ``hardware'' commitments would have
produced a very highly leveraged enhancement of these ``big ticket''
items. Also, the recent National Research Council's ``Pathways'' report
has made a similar point about the under funding of NASA's research
base necessary to optimize the value of its large satellite programs.
In the case of my own lab, GFDL, the stresses created have been
daunting. Over the past 15 years, GFDL's base funds for science have
diminished by more than half in purchasing power due to unfunded
inflationary losses, to increased administrative costs, and to
Congressionally authorized pay raises, so conspicuously unaccompanied
by the funds necessary to pay for them.
In my strong opinion, this seemingly oblivious diminution of the
federal research talent base has produced a serious reduction from the
expected return on NOAA's and NASA's substantial investments in large
environmental data and computing systems. Moreover, I see no evidence
of any observable reversal of this destructive trend. In fact, the
current budget initiative processes in place for FY2001 and 2002 appear
to perpetuate this seemingly oblivious shortfall in the return from our
big ticket ``hardware'' investments, including supercomputers.
Many of us in the scientific community find it inexplicably
baffling that something so obvious and so amenable to repair can remain
so conspicuously unaddressed for so long.
Question 3. Can you discuss the validation process used to authenticate
Answer. Let me begin by asserting that there is no such thing as a
``validated climate model.'' We do find that the models perform very
well for certain processes under certain circumstances. These same
models exhibit important deficiencies under other circumstances.
Interestingly, the same dilemma is present in the futile quest for
``validated'' data sets. There is a surprisingly small number of the
scientists who analyze observational data and output data from model
experiments who are focused on sharpening our understanding by careful
evaluation of the strengths, weaknesses, and information content of
these ``real-world'' and model-based data sets.
Given the above constraints, models are evaluated (not validated)
through careful assessment of their agreement (or lack thereof) with
carefully analyzed data sets. For example, are the model's simulated
desert regions in the right location with the right climate and the
right level of natural variability on time scales of years to decades?
Are the characteristics of the modeled Arctic region, including sea
ice, in agreement with available data? Does the model simulate credible
El Nino and La Nina events? Are the characteristics of the moist
subtropics, such as the southeast U.S., properly simulated? Is the
seasonal cycle of climate correctly simulated in all of these regions?
Generally speaking, the answers to these kinds of questions is yes.
However, a closer look often reveals significant discrepancies between
observations and model simulations.
Does a correct simulation of the present guarantee that we can
simulate future climate well, assuming that we know how carbon dioxide,
sulfate particles, and other greenhouse gases will change in the
future? Not necessarily. Such agreements do add confidence to our use
of the models as a tool, but do not supply the desired guarantee.
A very important international effort is currently underway to use
the observed, roughly 1.3+F, warming of the global-mean surface-air
temperature over the 20th century as a critical test of the models'
abilities to project future climate changes. This international
collaborative effort, which includes GFDL and the National Center for
Atmospheric Research, is showing that the models capture the essence of
the observed 20th century warming rather well, although the models
differ in their details. These studies do indicate, however, that
imperfections in the observations, in the ``exotic'' forcings operative
in the past century (such as solar changes, and indirect effects of
sulfate and carbon particles), and in the models themselves, still
prohibit us from tightly constraining the levels of uncertainty in the
model-based projections. That is why my official testimony gives a 2-6
+F range of warming for ``business as usual'' in the middle of this
century. In spite of this genuine uncertainty, there is still no viable
hypothesis that makes a credible case that the global warming problem
will be substantially less than our best current estimates.
Question 4. Why is the largest uncertainty regarding global-mean
surface warming due to clouds? Can you explain this further.
Answer. Many aspects of calculating the key effects of global warming
are rather simple; many of its basic features are rather well
understood. For the past three decades, for example, the clear-sky
trapping of outgoing heat radiation from the earth by CO2
and other greenhouse gases are well documented, as are many aspects of
the role of water vapor increases in amplifying this ``greenhouse''
As we all know, cloudy skies have a dramatic effect in suppressing
the overnight cooling that is so evident when skies are clear. Clouds
thus absorb outgoing heat radiation and radiate energy back to the
earth's surface, producing a warming effect. They also reflect incoming
radiation from the sun, producing a cooling effect. Increasing clouds
near the ground produce a net cooling effect on the climate, while
increasing clouds at 6 miles altitude tend to warm the climate.
Each of these separate cloud effects are difficult to calculate
with accuracy. The combined effects in the context of climate change
tend to be small differences between large opposing effects, of which
all carry significant uncertainty. Moreover, the effects vary
differently in different geographic regions, and all of these effects
depend upon the details of very small-scale phenomena on the scale of
the water droplets and/or ice crystals in the clouds. Furthermore,
satellite-based measurements do not neatly diagnose the net role of
clouds very well, even in today's climate.
Thus, clouds have legitimately earned their place as the leading
source of the uncertainty in our projections of climate change.
Question 5. What is your current accuracy rate of climate models for
projecting tropical storms, earthquakes, and floods? How has your
understanding of global warming changed your models?
Answer. I am rather confident, better than 2 out of 3, that hurricanes
and similar tropical storms, once formed, will tend to have stronger
winds and considerably greater rainfall as the climate and the oceans
continue to warm. The warmer and moister atmosphere and the warmer
ocean below, simply put, makes the potential energy of a hurricane
significantly stronger. Today, those hurricanes that stay over warm
water for sufficient time do tend to approach their maximum potential
power. We expect that to be also true in the future, only at higher
intensities. Some have argued that we also should expect more
hurricanes in the future warmer earth. That may be so, but I see no
convincing scientific evidence that says that. For now, we simply do
All models of which I am aware do tend to produce more floods- in
those regions where floods already tend to be prevalent today. At the
simplest level, this effect is mainly due to the expected higher water
vapor amounts in the atmosphere due to increased evaporation efficiency
over the warmer oceans. In effect, wet weather systems become even
wetter because the atmosphere will carry more water. Conversely,
drought prone regions, such as the southwest U.S., are likely to be
even drier due to increased evaporation of soil moisture in the warmer
Earthquakes have no known or suspected connection to a warming
climate. Even speculated effects would be expected to be very weak.
Our models have evolved significantly in response to improvements
in our understanding of very complex phenomena. For example, the
mathematical modeling of clouds has become significantly more
sophisticated in the treatment of radiative, convective, and cloud
microphysical processes. Unfortunately, these improvements have yet to
produce dramatic breakthroughs in this dauntingly difficult problem.
However, the problem is now being attacked with increasingly focused
tools from specialized observations, better theories, and models more
firmly rooted in fundamentals of atmospheric physics and dynamics.
Question 6. You stated in your testimony that you are ``virtually
certain'' that increasing greenhouse gases are due to human activities.
What erased the doubt in your mind?
Answer. Actually, there has not been much doubt about this in the
scientific community for over a decade. For the dominant greenhouse
gas, carbon dioxide, we can directly calculate the changes in
atmospheric fossil fuel carbon from year to year by measuring the
amount of the isotope, carbon-14. This isotope is produced in the
atmosphere by bombardment from high energy solar cosmic rays. Once
created in the atmosphere, carbon-14 decays with a half life of about
5500 years. Because of this, fossil carbon in the form of coal, oil,
and natural gas that has been buried for a hundred million years is
devoid of the carbon-14 isotope. As more fossil carbon is injected into
the atmosphere, the carbon-14 isotope has become progressively more
deficient relative to the non-radioactive carbon-12 form.
Thus, we are not debating whether humans have substantially
modified the carbon dioxide amounts in the atmosphere. They have. The
real science issue is focused on how much climate change will occur.
Beyond the science, people are concerned about who or what would be the
most impacted, and who will ``pay'' the near-term costs of mitigating
carbon dioxide emissions, or the delayed costs of dealing with the
impacts of climate change upon essentially all life forms on earth.
Response to Written Questions Submitted by Hon. John McCain to
Dr. Kevin E. Trenberth
Question 1. The national Research Council's report mentioned a
substantial disparity between satellite data and surface temperature
trends. Can you summarize the extent of the disparity?
Answer. Over the 20 years 1979 to 1998, the linear temperature trend
for the surface is estimated to be 0.25 to 0.4+C in contrast to 0.0 to
0.2+C for the satellite data. While uncertainty exists in the exact
trend number at about the 0.1+C/decade level (owing to how the spatial
coverage of data is handled, how global averages are computed,
treatment of missing data, begin and end points, etc.), the difference
is large enough that it is significant. It was labeled a ``disparity''
by the report as opposed to a ``discrepancy'' as the latter implies
something amiss, whereas the report assesses that it is likely mostly
real and arises because the two measurements are of different physical
Question 2. The National Research Council report noted that at the
outset none of the temperature measurements systems were specifically
designed for long-term climate monitoring. Can you discuss the design
life for these instruments and how it compares to the actual life?
Also, what are the implications of this extended use on the accuracy of
Answer. At the surface, measurements are made with individual
thermometers at many sites around the world. As well as calibration of
the thermometers, the siting and exposure to the atmosphere must be
standardized and should not change in time if climate trends are to be
correctly monitored. Changing thermometers is not an issue, as they are
quite accurate. Of more concern are changes in the way and time of day
they are read, and changes in exposure (such as trees or buildings
changing nearby, or building a city around the site; this latter point
is the ``urban heat island effect''). Movements of sites for
convenience, such as from city sites to the airport, are a substantial
problem and this and other changes in practice, can be overcome as long
as parallel measurements are maintained for at least a year, but often
this has not been done.
For the atmosphere above the surface, radiosonde packages of
instruments are used. The package is flown on a balloon and is regarded
as expendable and only used once. As a result the package must be as
inexpensive as possible, which has led to compromises in quality.
Changes to new improved technology can appear as a spurious change in
climate unless such changes are measured and adjusted for. Mostly this
has not been the case.
For satellites and their platform of instruments, the typical
design life is about 4 or 5 years. Problems arise with occasional loss
of a satellite upon launch or premature failure of one or more
instrument components. As the design for the NOAA series of satellites
is to have two satellites in orbit at all times (one in the morning and
one in the afternoon), there is some overlap expected from one
satellite to the next. There have been times, however, notably in 1985
and 1986 when NOAA-9 was the only satellite flying, that the overlap at
both ends was too short to reliably splice the record from one
satellite to the next. Normally this is done by matching records
between overlapping satellites. The difficulty of doing this is
compounded by the fact that the orbits of the satellites are not
stable. Instead they tend to drift, both through orbital decay and in
local crossing time. This latter effect means that measurements are
made at slightly different times each day. For instance, NOAA-11
drifted from an equator crossing time of 2 p.m. to after 5 p.m. from
1989 to 1994. The difference in temperature between these times of day
is considerable and appears as a climate change over time unless
corrected for. Corrections are indeed made for this but they are likely
to be imperfect and leave residual effects that may be significant over
land where the diurnal temperature changes are large. Orbital decay
also has effects by altering the geometry of any measurements that are
not directed in the vertical (which is most of them), and this alters
the interpretation of the measurements, which is recently being allowed
for. On-board calibration of the instrument itself helps to minimize
effects of instrumental drift and changes in exposure of the instrument
to the sun as the orbit changes and with time of year, which otherwise
would also be considerable. Attempting to allow for such effects has
been fully tried only recently but the adjustments are empirical, so
again residual errors are probable, although these are believed to be
Question 3. Dr John Wallace, who served as Chairman of the National
Research Council's Panel on Reconciling Temperature Observations, is
quoted as saying that ``There really is a difference between
temperatures at the two levels that we don't fully understand.'' Do you
agree with that statement and, if so, can you comment on the level that
we don't understand?
Answer. I agree with the statement, although I also think it does
warrant clarification. We have hypotheses about the nature of the
differences but proving them or narrowing the possibilities down is
difficult. Firstly, there are many differing influences on the
temperatures at different levels in the atmosphere. At the surface it
matters a great deal whether the surface is land or ocean, and over
land whether the surface is wet or dry and how much vegetation is
present. These influences are much less further aloft. Direct radiative
heating within the atmosphere matters a great deal in the troposphere,
and so it is important to known the spatial distribution and vertical
profiles of greenhouse gases (water vapor, carbon dioxide, methane,
etc., and especially ozone), aerosols and clouds. The radiative
properties of the aerosols (how absorbing versus reflecting/scattering)
are affected by the relative humidity and are poorly known and highly
heterogenous in space and time. Similarly for clouds, the water content
and size of droplets in clouds are needed to characterize their
radiative effects. Secondly, the models we have that translate the
forcings just mentioned into a vertical temperature profile also
contain uncertainties and imperfections. Some of the processes believed
to be important, such as convection, are either not well enough
understood or are very difficult to model accurately because, for
instance, of horizontal and vertical resolution of the model. Thirdly,
there are likely to be some remnant errors in the observations that
also add to uncertainties.
Climate models need to be further improved (especially in how they
handle convection and clouds), the changes in distributions of
greenhouse gases, aerosols, and clouds, and their radiative properties
need to be much better known to narrow the uncertainties, and further
improvements are desirable in the observational record.
Question 4. The National Research Council report stated that increases
in the number of small particles called aerosols often mask the
greenhouse effect, and that stratospheric depletion contributes to
cooling of the upper troposphere and stratosphere. How much cooling is
taking place as a result of these aerosols?
Answer. Aerosols vary enormously in space and time because they are
washed out of the atmosphere by rain, and so their lifetime is
typically 5 to 10 days. This is the reason they vary so much spatially
and they tend to be greatest in concentration near their source. The
sources vary greatly around the world. Some aerosols (containing soot
for instance) absorb solar radiation and produce heating, but the most
pervasive ones in the Northern Hemisphere make up the milky white haze
that you see from airplane windows crossing North America and these
sulfate aerosols cause cooling by reflecting the sun's rays back to
space. The cooling from sulfates is believe to be about -0.5 W m-2
(plus or minus 50%) which converts to about a cooling of roughly 0.3+C
over the past century. A bigger effect may come from the changes in
clouds from aerosols. Aerosol particles encourage more cloud droplets
to form, which makes a cloud brighter and more reflective. Low cloud is
known from observations to have increased but how much of this increase
is due to aerosols is unknown. The cooling is estimated to range from 0
to perhaps as much as -2 W
m-2 and so the cooling could be as much as 1.2+C. Over land
since 1950, the maximum temperature is rising at a rate of about 0.1+C/
decade less than the minimum temperature and this has been shown to be
mainly due to the increase in cloudiness. So there is huge uncertainty
to this answer.
[Please note, the numbers in this answer are in the context of the
IPCC estimates of radiative forcing. These include 2.3 W m-2
for the sum of the main well mixed greenhouse gases (not including
ozone) to date and perhaps a total of about 1.5 W m-2 for
all radiative forcings. I use a translation into a temperature change
of 4 W m-2 (the value for doubling carbon dioxide alone)
corresponding to 2.5+C. This total would then correspond to over 0.9+C
increase in temperature versus 0.7+C observed; the difference being due
to delays in the system response.]
Question 5. You mentioned in your written statement that changes in
extremes changes in climate will be much greater than changes in the
mean as a result of global warming and the increased amount of moisture
in the air. Can you elaborate on the types of extremes we may be
Answer. A relatively small change in the mean of any quantity can alter
the frequency of extremes by 100% or more. By their very nature,
extremes occur rarely, and so observationally based statistics on them
and their changes are hard to come by. The databases to determine their
changes are less available and the demands on accuracy are much
greater, and so actual measured changes in extremes are often
Changes in some extremes have been documented in the United States
and to a much lesser extent elsewhere. In the United States,
precipitation is increasing, and most of that increase is in the
heaviest (top 10%) rainfall rates. Extremes of daily rainfall of over 2
inches per day have increased about 10% over the past century. (Because
it typically rains 10% or less of the time, hourly rather than daily
rainfall data should be used for this analysis, but are much less
readily available). Much below normal temperatures (lowest 10%) are
decreasing and much above normal temperatures (top 10%) are increasing
for the U.S. (although some record high temperatures still hark from
the 1930s in the Dust Bowl era). In general, extremes are observed to
What we expect, but have little documentation of, is that rainfall
rates are increasing, so that when it rains, it rains harder, and there
is thus more runoff and a greater risk of flooding. Whether flooding
occurs or not depends on whether it is mitigated by building drainage
ditches, levees, culverts, etc. through planning by the Corp of
Engineers and local councils in the U.S. In many developing countries,
however, the risk of flooding has been exacerbated by deforestation
that greatly increases runoff. In most places, increased building in
coastal areas and flood plains has increased vulnerability to flooding.
It is also suspected that droughts set in more quickly through
increased drying. Plant therefore wilt faster and droughts become more
severe and are apt to last a bit longer with global warming. The result
is greatly increased risk of wild fire and for ``control burn'' fires
to get out of control. Heat waves are also more likely. The ``heat
index,'' which combines humidity and temperature effects, is likely to
venture into the uncomfortable range more often and over much greater
Question 6. Figure 2 of your statement indicates a decrease in the
average mean global temperature in the year 1940. Can you explain the
Answer. The global mean temperature had a peak in the early 1940s and
there was a decline or leveling off until about the 1970s. Firstly,
observations during World War II were less abundant than before or
after but also occurred in new areas (like the Pacific atolls) and so
some of the temperature peak might not be real (e.g., one can not stand
on the deck of a ship and read a thermometer at night with a light
during war, and so the thermometer is taken inside where it may be
warmer.) However, a massive long-lived El Nino from 1939 to 1942 no
doubt contributed to the warmth. Secondly, following the war there was
great industrial development that is known to have increased the amount
of aerosol in the atmosphere sharply, and so this contributes a cooling
effect. Thirdly, the warming from about 1920 to 1940 was probably in
part caused by increases in solar radiation, which leveled off in the
1940s. Climate models run with reasonable estimates of the changes in
aerosols and sun plus greenhouse gas increases are able to reproduce
Question 7. One of the recommendations of the NRC report (page 25)
states that the scientific community should explore the possibility of
exploiting the sophisticated protocols that are now routinely used to
ensure the quality control and consistency of the data ingested into
operational numerical weather prediction models, to improve the
reliability of the data sets used to monitor global climate change.
Would you explain this recommendation and discuss how it should be
Answer. During the ingestion of data into four dimensional data
assimilation systems, extensive quality control of the observations
occurs: 1) through comparison of observations with estimates of the
observed values from the previous forecast, and 2) comparison with
adjacent observations of all kinds in a consistent physical (model)
framework. Sometimes this enables correction for some kinds of errors
and it allows systematic errors to be estimated. The result is that a
quality control flag can be assigned to each observation and
information exists on whether the observation was used or rejected, and
how accurate it appears to be. This information should be retained and
archived. In the case of rejected or missing data, an accurate estimate
of what the observation should have been can be made, and this estimate
can be utilized to improve the data set. Similarly, more intelligent
decisions can be made to quality control the whole data set and make it
My recommendation is to have the numerical weather prediction
centers, in collaboration with climate scientists, select a subset of
observations (in particular a subset of radiosonde observations) and
generate an enhanced data set that includes, with the original
observation, the quality control output and estimates of correct values
in cases of missing or erroneous data. This could feasibly be done for
temperature, and perhaps humidity and wind measurements during a
reanalysis of past data. In particular, monthly summaries of estimates
of offset bias should prove very valuable. Then independent analysis of
the more comprehensive data set should enable more reliable trend
estimates from the radiosondes.
Response to Written Questions Submitted by Hon. John McCain to
Question 1. If you consider all of the peer-reviewed assessments that
the IPCC has made over the years, have there been any distinctive
trends in the findings? Have any of the studies contradicted each
Answer. There has clearly been a longer observational record and an
evolution in our understanding of the Earth's climate system and the
potential influence of human activities. Our understanding of the
fundamental process that control the Earth's climate have clearly
improved, although significant uncertainties still remain. This,
improved understanding of the processes that control the Earth's
climate system, combined with more powerful computers, has led to
significantly more sophisticated theoretical models that include a more
realistic simulation of land, oceanic and atmospheric processes with
increased spatial resolution.
There have been no major changes in the conclusions of successive
IPCC reports. In most cases, based on new research findings, there have
been small changes in understanding but few, if any, substantial
changes in our fundamental understanding.
Let me summarize how our understanding has evolved since the First
IPCC assessment in 1990 using just a few key issues to illustrate
trends in findings. I have focussed my answer on the climate system
rather than on the projected impacts of climate change on human health,
socio-economic sectors and ecological systems or the projected
approaches to mitigate climate change:
1. Past changes in atmospheric composition, climate and climate-
atmospheric composition: the atmospheric concentrations of
the major greenhouse gases, i.e., carbon dioxide, methane and
nitrous oxide have all continued to increase. However, the
atmospheric concentrations of some of the chlorofluorocarbons
have peaked and are now decreasing because of the effectiveness
of the Montreal Protocol.
temperature: global mean temperatures have continued to
increase with the warmest three years of the last century all
occurring since 1990;
precipitation: globally, precipitation is continuing to
increase. However, we have now shown that the spatial and
temporal distribution of precipitation is changing in some
regions of the world, e.g., in the U.S. there is now evidence
of more precipitation in winter and an increase in heavy
precipitation events in summer.
sea level: the latest analysis confirms earlier conclusions
that sea level has risen 10-25 cms over the last 100 years.
2. Attribution of the observed changes in climate:
in contrast to the first assessment report, the second
assessment report concluded that the observed changes in the
Earth's climate over the last 100 years could not be ascribed
to natural phenomena alone, and concluded that there was now a
discernible human influence on the Earth's climate.
3. Projected changes in atmospheric composition, climate and
atmospheric composition: the emissions scenarios work has
become more sophisticated, but the bottom line conclusion
largely remains the same, i.e., there is a wide range of
plausible future greenhouse gas emissions, which primarily
depends on population and economic growth, technological
advances and governance structures.
climate sensitivity: projected changes in climate depend
upon projected changes in atmospheric composition (greenhouse
gases and aerosols) and the sensitivity of the climate models
to changes in atmospheric composition, i.e., the response
function, which we have termed the climate sensitivity factor.
In spite of our improved understanding of the climate system,
there has been no change in our estimate of the climate
sensitivity factor since the first assessment report, i.e.,
global mean surface temperatures are projected to increase from
1.0-4.5 degrees Centigrade at equilibrium in a doubled carbon
dioxide world, with the best estimate being 2.5 degrees
aerosols: the ``cooling'' role of aerosols was not
recognized in the first assessment report, but was in the
second assessment report.
temperature: projected changes in global mean surface
temperature in 2100 have varied from the first assessment
report until now, but well within the uncertainty range and
because of known factors. The business as usual best estimate
projection for changes in global mean surface temperature in
2100 was 3.0 degrees Centigrade, within a range of 2.0-5.0
degrees Centigrade (the business as usual greenhouse gas
scenario coupled with the range of climate sensitivity). In the
second assessment report, the business as usual best estimate
projection for a change in global mean surface temperature in
2100 was 2.0 degrees Centigrade within a range of 1.0-3.5
degrees Centigrade (four greenhouse gas scenarios coupled with
the range of climate sensitivity). If the latest IPCC emissions
scenarios are used in conjunction with a range of climate
models the projected changes in mean surface temperature in
2100 would be from about 1.0-5.0 degrees Centigrade (six
greenhouse gas scenarios coupled with the range of climate
sensitivity). The decrease in the business as usual best
estimate projection for changes in global mean surface
temperature in 2100 between the first and second assessment
report was due to lower projections of chlorofluorocarbon
emissions (Montreal Protocol) and carbon dioxide emissions and
the inclusion of sulfate aerosols in the models (sulfate
aerosols tend to cool the atmosphere and hence partly offset
the warming effect of the greenhouse gases).
precipitation: projections of changes in precipitation have
consistently shown an increase in global precipitation, with
increases in the tropics, mid- and high-latitudes and decreases
in the sub-tropics. The exact changes are model dependent.
sea level: projected changes in global mean sea level in
2100 have varied slightly from the first assessment report
until now, but well within the uncertainty range and because of
known factors. The business as usual best estimate projection
for changes in global mean sea level in 2100 was 65 cms, within
a range of 30-110 cms. In the second assessment report, the
business as usual best estimate projection for a change in
global mean sea level in 2100 was 50 cms within a range of 15-
95 cms. If the latest IPCC emissions scenarios are used in
conjunction with a range of climate models the projected
changes in mean sea level in 2100 would be from about 10-90
cms. The changes in projected sea level occur primarily because
of changes in temperature projections, as well as in some cases
because of small changes in the glacier, ice sheet and ocean
Question 2. You mentioned in your statement that the time to reverse
the human-induced changes in the climate and the resulting
environmental damages would not be years to decades but centuries to
millennia. Is it reasonable to make any major conclusions on the future
based upon models and data collection systems that may need further
Answer. Yes. While recognizing there are uncertainties associated with
precisely quantifying changes in climate at the regional and global
scale, and hence the associated impacts on human health, socio-economic
sectors and ecological systems, stating that the time to reverse human-
induced changes in the climate and the resulting environmental damages
would not be years to decades but centuries to millennia is a robust
conclusion. The conclusion primarily rests on an understanding of the
lifetime/adjustment time of carbon dioxide, the major anthropogenic
greenhouse gas. The lifetime of carbon dioxide is governed by the
exchange of carbon dioxide between the atmosphere and the deep waters
of the oceans. Whilst there is a rapid equilibration (less than five
years) of carbon dioxide between the atmosphere and the surface waters
of the oceans, it takes much longer (more than a century) for carbon
dioxide in the atmosphere to equilibrate with the deep oceans. Our
understanding of this feature of the carbon cycle is based on models
that have been field-tested against tracer data, e.g., the rate of
uptake and diffusion into the deep oceans of atmospheric
chlorofluorocarbons and radio-active carbon (formed during the atomic
The small portion (15-25%) of human-induced changes in climate that
can be attributed to short-lived gases, i.e., methane (a lifetime of
about a decade) and tropospheric ozone (a lifetime of a few days) can
be reversed much quicker. Conversely, reductions in sulfate aerosol
precursor emissions (i.e., sulfur dioxide) would lead to a rapid
increase in climate change because of the very short lifetime (days).
Question 3. Would you describe some of the technologies that can be
used to mitigate climate change.
Answer. The IPCC Second Assessment Report concluded that there is a
wide range of technologies that already exist that can be used to cost-
effectively mitigate climate change. However, before listing some of
them it is important to note that cost-effective mitigation of climate
change (Article 3 of the UNFCCC) will be most effective through a
combination of changes in both the policy framework and the fuller
utilization of a wide of technologies in energy supply, energy demand
and the agricultural/forestry sectors. In addition it should be
recognized that stabilization of greenhouse gas concentrations in the
atmosphere (Article 2 of the UNFCCC) will require the development and
market penetration of new and improved technologies, hence the need for
increased public and private sector funding for R&D.
All of the policy and technology options listed below are discussed
in significant detail in IPCC assessments and Special Reports, e.g.,
technology transfer and land-use, land-use change and forestry.
Policy Framework: It is important to get the policy framework
correct in order to stimulate the utilization of ``climate-friendly''
technologies and strategies, domestically and internationally. For
example, if there are policies that distort the market, e.g., fossil
fuel subsidies, they both discourage the efficient use of energy and
the penetration of modern renewable energy technologies. An appropriate
policy framework, augmented by education and training programs, would
command and control, e.g., energy efficiency standards,
market mechanisms, e.g., domestic and international
emissions rights and project-based carbon offset trading;
removal of subsidies that increase greenhouse gas emissions;
incentives for the use of new technologies during market build-
Technologies and Strategies: There needs to be a concerted effort
to produce and use energy more efficiently and to emit lower amounts of
greenhouse gases, and to reduce emissions and increase the uptake of
carbon in agricultural, forestry and rangeland systems. In addition to
energy and land-use technologies, information technologies can be used,
inter-alia, for the more efficient management of energy systems,
improve the efficiency of transportation systems and decrease travel
miles through telecommuting and teleconferencing.
Supply side options include:
fuel switching (coal to gas)
increased power plant efficiency (co-generation)
carbon dioxide sequestration (carbon dioxide separation
followed by long-term sequestration)
renewable energies, e.g., wind, solar electric, solar
thermal, modern biomass, small-scale hydropower and
Demand-side options include:
transportation (e.g., lighter vehicles, increased
combustion efficiency, alternate fuels (e.g., fuel cells),
electric vehicles, hybrid vehicles (combustion/electric)--
land-use planning can improve the efficiency of
commercial and residential buildings (e.g., building
shells, lighting, heating and air conditioning systems,
industry (e.g., processes, recycling)
Agriculture, Forestry and Rangelands
improved agricultural (e.g., no-till) and grazing land
agroforestry (only a significant option in developing
afforestation, reforestation, slowing deforestation and
improved forest management