WASHINGTON, June 6 — A panel of top American scientists declared today that global warming was a real problem and was getting worse, a conclusion that may lead President Bush to change his stand on the issue as he heads next week to Europe, where the United States is seen as a major source of the air pollution held responsible for climate change.
In a much-anticipated report from the National Academy of Sciences, 11 leading atmospheric scientists, including previous skeptics about global warming, reaffirmed the mainstream scientific view that the earth's atmosphere was getting warmer and that human activity was largely responsible.
"Greenhouse gases are accumulating in earth's atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise," the report said. "Temperatures are, in fact, rising."
The report was requested by the White House last month in anticipation of an international meeting on global warming in Bonn in July but arrived just before President Bush leaves next week for Europe, a trip that includes talks on global warming with leaders of the 15 European Union countries in Goteborg, Sweden.
European leaders expressed outrage in March when Mr. Bush rejected the global warming pact known as the Kyoto Protocol, an international treaty negotiated in Kyoto, Japan, in 1997, and the subject has been building as an important test of the administration's foreign policy.
In the White House's first official acknowledgment of the academy's conclusions, Condoleezza Rice, Mr. Bush's national security adviser, told reporters today, "This is a president who takes extremely seriously what we do know about climate change, which is essentially that there is warming taking place."
Mr. Bush and many in his cabinet, who discussed the subject at length on Tuesday, have been trying to hammer out a proposal on limiting the pollutants that cause global warming.
"A cabinet-level working group is still working on what it wishes to say to the president before we go to Europe," Ms. Rice said.
She said Mr. Bush would talk with the allies "a little bit about what we've learned thus far."
Without being specific, Ms. Rice said Mr. Bush was being guided by certain principles in formulating a proposal.
"One would want to be certain that developing countries were accounted for in some way, that technology and science really ought to be important parts of this answer, that we cannot do something that damages the American economy or other economies because growth is also important," she said.
In response to critics who have suggested that Mr. Bush is ignoring an issue of mounting international concern, Ms. Rice portrayed the group as feverishly committed to educating itself and coming up with a proposal.
"It has been a matter of bringing up to speed some of the highest- ranking people in this government," she said. "I would dare say — dare challenge you to find a situation in which you've had so many high-ranking people sitting there week after week after week, understanding the challenge that we face in global climate change, everybody from the vice president, the secretary of state, the secretary of interior, secretary of agriculture. It has been quite something to see all of these people grappling with the issue."
Administration officials have said privately that the White House could have handled the matter with greater tact, and Ms. Rice conceded as much today.
"The president had made clear when he was a candidate that he did not believe the Kyoto Protocol addressed the problem of climate change in a way that the United States could support," she said. "In retrospect, perhaps the fact that we understood that we had already said this was not immediately observable to everybody, and it might have been better to let people know again, in advance, including our allies, that we were not going to support the protocol."
This was unusually blunt talk from a White House that until now has fastidiously avoided the phrase "global warming" and repeatedly expressed doubts about the clarity of the science underlying the theory that emissions from smokestacks and tailpipes were heating the atmosphere in ways that posed a threat.
In an indication of the headwind that Mr. Bush is sailing into next week in Europe, the journal Science, published by an American scientific organization, recently carried an open letter signed by 16 prestigious scientific panels in countries around the world calling for "prompt action" to reduce the gases like carbon dioxide that trap heat like in a greenhouse.
The increase in temperatures, the editorial said, "will be accompanied by rising sea levels, more intense precipitation events in some countries and increased risk of drought in others and adverse effects on agriculture, health and water balance."
It continued, "We urge everyone — individuals, businesses and governments — to take prompt action to reduce emissions of greenhouse gases."
Many international business executives have been pressuring the administration to move more aggressively on the issue. And so has a powerful band of Mr. Bush's closest advisers, including Secretary of State Colin L. Powell, Ms. Rice, Treasury Secretary Paul H. O'Neill, and Christie Whitman, the administrator of the Environmental Protection Agency.
Today's report reflects the increasing certainty of the scientific community here and abroad that the warming of the last 50 years is probably because of the increase in greenhouse gas concentrations. The panel said the degree of confidence in this conclusion was "higher today than it was 10 or even 5 years ago."
Still, it said, large uncertainties limit predictions of the extent and consequences — good and bad — of future warming. But it affirmed the scientific consensus that human- caused climate warming could well be a dominant environmental problem throughout the new century, depending on how fast the gases accumulate in coming decades.
"Human-induced warming and associated sea level rises are expected to continue through the 21st century," it said.
And it said that "national policy decisions made now and in the longer-term future will influence the extent of any damage suffered by vulnerable human populations and ecosystems later in this century."
The report thus all but eliminates one reason the administration has been using to forestall any action on global warming.
And it deals a strong card to Democrats on Capitol Hill who have long sought more aggressive action on global warming. Senator John Kerry, Democrat of Massachusetts and a leading advocate of action said of the report, "It confirms in stark terms the reality that many of us had accepted a considerable amount of time ago and refutes an effort by the White House to seek some sort of escape hatch from that reality."
Senator Chuck Hagel, Republican of Nebraska and a longtime critic of the Kyoto Protocol, instead highlighted the uncertainty mentioned in the report and drew the opposite conclusion of Mr. Kerry.
"This report is certainly not a prescription for the drastic measures required under the Kyoto Protocol," Mr. Hagel said in a statement.
Nonetheless, in a nod toward the unanimity of the scientific community, he added:
"This report does provide us with enough evidence to move forward in a responsible, reasonable and achievable way to reduce greenhouse gas emissions. It provides us with a basis to move forward with an alternative to the Kyoto Protocol."
Environmentalists hailed the report as a significant step in the long effort to force the United States to curtail greenhouse gases. Phil Clapp, president of the National Environmental Trust, said, "The president can no longer wiggle out of aggressive action by arguing that the science is inconclusive."
Mr. Clapp also suggested that the report called into question Mr. Bush's proposed energy plan, which seeks to step up production of coal, oil and gas-fired power plants.
"This makes the president's energy plan look completely irresponsible," he said.
Mr. Clapp said environmental groups had estimated that if the energy plan was fully put into effect, it would increase the pollution that causes global warming by 35 percent over the next decade.
The report was written by 11 atmospheric scientists who are members of the National Academy of Sciences. The authors included Dr. Richard S. Lindzen, a meteorologist at the Massachusetts Institute of Technology, who for years has expressed skepticism about some of the more dire predictions of other climate scientists about the significance of human-caused warming.
The report was requested on May 11 in a letter to Dr. Bruce Alberts, the president of the National Academy of Sciences, from John M. Bridgeland, deputy assistant to the president for domestic policy, and Gary Edson, deputy assistant to the president for international economic affairs.
A statement from the academy today said, "The White House requested this fast-track review of the state of climate science in preparation for international discussions on global warming scheduled to take place in the coming weeks."
Initially, the White House asked two questions of the academy: What are the greatest strengths and weaknesses in the science pointing to human-caused warming? And, are there significant differences between the full scientific analysis completed recently by the Intergovernmental Panel on Climate Change, sponsored by the United Nations, and the final executive summary?
There have been three assessments of global warming by the international panel since 1990, and each has drawn a more conclusive picture than the last of the link between human activities and the prospects for significant harm to agriculture, ecosystems and coastlines.
But conservatives in Congress — notably Senators Hagel and Larry E. Craig, Republican of Idaho — and groups representing industries whose business depends on fossil fuels have long criticized the findings of the international panel as biased, pointing particularly to differences between the voluminous chapters on complicated scientific points and briskly worded summaries that tend to influence policy.
The panel, led by Dr. Ralph J. Cicerone, the chancellor of the University of California at Irvine, met initially in California and spent the next weeks intensively sifting the existing science.
The report does provide some ammunition for critics in its description of the conclusion of the international climate group. It concluded, for example, that the international panel had a tendency in its executive summary to understate caveats and focus on the harsher possible consequences of climate warming. But over all, the panel described the international work as "admirable" and robustly supported its conclusions.
In a telephone interview today, Dr. Cicerone said he hoped the report, by spelling out the scientific basis for various predictions, would dispel some unwarranted skepticism about aspects of the warming problem.
One climate scientist who critiqued a draft of the new report for the academy said no one in the administration should be surprised at the firm nature of the result.
"They asked a string of questions that might have been appropriate in 1990," the scientist said.
"Hello?" he said. "Where've you been the last decade?"
FOR IMMEDIATE RELEASE June 6, 2001 by National Academy of Sciences
LEADING CLIMATE SCIENTISTS ADVISE WHITE HOUSE ON GLOBAL WARMING
WASHINGTON -- In a report requested by the Bush administration, a committee of the National Academies' National Research Council summed up science's current understanding of global climate change by characterizing the global warming trend over the last 100 years, and examining what may be in store for the 21st century and the extent to which warming may be attributable to human activity. The committee -- made up of 11 of the nation's top climate scientists, including seven members of the National Academy of Sciences, one of whom is a Nobel-Prize winner -- also emphasized that much more systematic research is needed to reduce current uncertainties in climate-change science.
"We know that greenhouse gases are accumulating in Earth's atmosphere, causing surface temperatures to rise," said committee chair Ralph Cicerone, chancellor, University of California at Irvine. "We don't know precisely how much of this rise to date is from human activities, but based on physical principles and highly sophisticated computer models, we expect the warming to continue because of greenhouse gas emissions."
Based on assumptions that emissions of greenhouse gases will accelerate and conservative assumptions about how the climate will react to that, computer models suggest that average global surface temperatures will rise between 2.5 and 10.4 degrees Fahrenheit (1.4 and 5.8 degrees Celsius) by the end of this century.
With regard to the basic question of whether climate change is occurring, the report notes that measurements show that temperatures at the Earth's surface rose by about 1 degree Fahrenheit (about .6 degrees Celsius) during the 20th century. This warming process has intensified in the past 20 years, accompanied by retreating glaciers, thinning arctic ice, rising sea levels, lengthening of the growing season in many areas, and earlier arrival of migratory birds.
The committee said the conclusion of the Intergovernmental Panel on Climate Change (IPCC) that the global warming that has occurred in the last 50 years is likely the result of increases in greenhouse gases accurately reflects the current thinking of the scientific community. However, it also cautioned that uncertainties about this conclusion remain because of the level of natural variability inherent in the climate on time scales from decades to centuries, the questionable ability of models to simulate natural variability on such long time scales, and the degree of confidence that can be placed on estimates of temperatures going back thousands of years based on evidence from tree rings or ice cores.
The greenhouse gas of most concern is carbon dioxide since the naturally occurring chemical also is generated by the continuing burning of fossil fuels, can last in the atmosphere for centuries, and "forces" more climate change than any other greenhouse gas, the committee said. Other significant greenhouse gases include methane, nitrous oxide, water vapor, tropospheric ozone, and chlorofluorocarbons (CFCs), which together have a "forcing" on climate change approximately equal to that of carbon dioxide. Man-made sources of methane, nitrous oxide, and ozone have resulted in substantially increased concentrations in the atmosphere in the 20th century, although each of these gases also has natural sources. CFCs are entirely synthetic compounds.
The best information about past climate variability comes from ice cores drilled miles deep in Antarctica and Greenland, which reveal that temperatures changed substantially over the past 400,000 years. Although most of these changes occurred over thousands of years, some rapid warmings took place over a period of decades.
The ice cores also trapped carbon dioxide and methane, which shows that the gases were present in the atmosphere at their lowest levels during cold eras and at higher levels during warm eras. Carbon dioxide did not rise much above 280 parts per million by volume (ppmv) until the industrial revolution. By the end of the 20th century, it had reached 370 ppmv, with an average increase in the last two decades of 1.5 ppmv a year. Both carbon dioxide and methane are more abundant in the atmosphere now than at any time during the 400,000-year ice core record.
The committee noted that the IPCC has examined a range of scenarios concerning future greenhouse gas emissions. The committee called such scenarios valuable because they provide a warning of the magnitude of climate change that may occur if emission rates continue to climb at a rate similar to last century, but it also said alternative scenarios are needed to illustrate the sensitivity to underlying assumptions, particularly with regard to future technological development and energy policy.
The committee also was asked by the White House to examine whether there were any substantive differences between the IPCC reports and their abridged technical and policy-maker summaries. The IPCC was established by the United Nations and World Meteorological Organization in 1988 and its reports and summaries have been influential in international negotiations related to the Kyoto protocol.
The full IPCC Working Group 1 report does an admirable job of reflecting research activities in climate science, and is adequately summarized in the technical summary, the committee said. The corresponding summary for policy-makers, it added, placed less emphasis on the scientific uncertainties and caveats. Looking to the future, the committee suggested that improvements to the IPCC process may need to be made to ensure the best scientific representation possible, and to keep the process from being seen as too heavily influenced by governments "which have specific postures with regard to treaties, emissions controls, and other policy instruments."
To reduce some of the uncertainties inherent in current climate change predictions, a strong commitment must be made to basic research as well as to improving climate models and building a global climate observing system, the committee said. More comprehensive measurements of greenhouse gases and increased computational power also will be needed.
Although potential impacts from global warming were looked at in the report, it was not part of the committee's charge to make policy recommendations for dealing with them. The White House requested this fast-track review of the state of climate science in preparation for international discussions on global warming scheduled to take place in the coming weeks. "In view of the critical nature of this issue, we agreed to undertake this study and to use our own funds to support it," said Bruce Alberts, president of the National Academy of Sciences and chair of the National Research Council. The study took a month.
The National Research Council is the principal operating arm of the National Academy of Sciences and National Academy of Engineering. It is a private, nonprofit institution that provides scientific and technical advice under a congressional charter.
Copies of CLIMATE CHANGE SCIENCE: AN ANALYSIS OF SOME KEY QUESTIONS will be available later this summer from the National Academy Press; tel. (202) 334-3313 or 1-800-624-6242 or on the Internet at HTTP://WWW.NAP.EDU. Reporters may obtain a copy from the Office of News and Public Information (contacts listed above).
NATIONAL RESEARCH COUNCIL
Division on Earth and Life Studies
COMMITTEE ON THE SCIENCE OF CLIMATE CHANGE
RALPH J. CICERONE 1 (CHAIR)
Chancellor, and Daniel G. Aldrich Professor
Department of Earth System Science and Department of Chemistry
University of California
ERIC J. BARRON
Earth and Mineral Sciences Environment Institute, and
Distinguished Professor of Geosciences
Pennsylvania State University
ROBERT E. DICKINSON 1
Professor of Dynamics and Climate
School of Earth and Atmospheric Sciences
Georgia Institute of Technology
INEZ Y. FUNG 1
Richard and Rhoda Goldman Distinguished Professor for the Physical Sciences;
Departments of Earth and Planetary Science and of Environmental Sciences,
Policy, and Management; and
Center for Atmospheric Sciences
University of California
JAMES E. HANSEN 1
NASA/Goddard Institute for Space Studies
New York City
THOMAS R. KARL
National Climatic Data Center
National Oceanic and Atmospheric Administration
RICHARD S. LINDZEN 1
Alfred P. Sloan Professor of Meteorology
Department of Earth, Atmospheric, and Planetary Sciences
Massachusetts Institute of Technology
JAMES C. MCWILLIAMS
Slichter Professor of Earth Sciences
Department of Atmospheric Sciences
Institute of Geophysics and Planetary Physics
University of California
F. SHERWOOD ROWLAND 1,2
Donald Bren Research Professor of Chemistry and Earth System Science
Department of Chemistry
University of California
EDWARD S. SARACHIK
Department of Atmospheric Sciences;
School of Oceanography; and
S.P. Hayes Center of the Joint Institute for the Study of the Atmosphere
and the Ocean University of Washington Seattle
JOHN M. WALLACE 1
Professor of Atmospheric Sciences
Department of Atmospheric Sciences, and
Co-Director Program on the Environment University of Washington Seattle
RESEARCH COUNCIL STAFF
VAUGHAN C. TUREKIAN
1 Member, National Academy of Sciences
2 Member, Institute of Medicine