The report was produced by some 600 authors from 40 countries. Over 620 expert reviewers and a large number of government reviewers also participated. Representatives from 113 governments reviewed and revised the Summary line-by-line during the course of this week before adopting it and accepting the underlying report. The report builds upon past IPCC assessments and incorporates new findings from the past six years of research. Scientific progress since the Third Assessment Report (TAR) is based upon large amounts of new and more comprehensive data, more sophisticated analyses of data, improvements in understanding of processes and their simulation in models, and more extensive exploration of uncertainty ranges. In summary, some of the major findings of the report indicate:
- Global atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years (see Figure SPM-1). The global increases in carbon dioxide concentration are due primarily to fossil fuel use and land-use change, while those of methane and nitrous oxide are primarily due to agriculture.
- The understanding of anthropogenic warming and cooling influences on climate has improved since the Third Assessment Report (TAR), leading to very high confidence that the globally averaged net effect of human activities since 1750 has been one of warming, with a radiative forcing of +1.6 [+0.6 to +2.4] W m-2.
- Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level.
- At continental, regional, and ocean basin scales, numerous long-term changes in climate have been observed. These include changes in Arctic temperatures and ice, widespread changes in precipitation amounts, ocean salinity, wind patterns and aspects of extreme weather including droughts, heavy precipitation, heat waves and the intensity of tropical cyclones.
- For the next two decades a warming of about 0.2°C per decade is projected for a range of SRES emission scenarios. Even if the concentrations of all greenhouse gases and aerosols had been kept constant at year 2000 levels, a further warming of about 0.1°C per decade would be expected.
Two other reports, part of the overall 4th Assessment Report, will be forthcoming: The Working Group II report on "Impacts, Adaptation and Vulnerability" will be released in April 2007; and The Working Group III "Mitigation of Climate Change" will be released in May 2007.
White House Agrees Human Activities Caused Most Warming
The U.S. Office of Science and Technology Policy of the Executive Office of the President issued a fact sheet and related information on the IPCC Working Group I report. According to the fact sheet, "The United States joined 112 other nations in finalizing and approving a landmark climate change science report today in Paris, France... The Working Group I portion of the Assessment Report released today represents a comprehensive assessment of the most recent state of knowledge of the physical science of climate change."
Dr. Sharon Hays, the leader of the U.S. delegation at the meeting and Associate Director/Deputy Director for Science at the White House Office of Science and Technology Policy said, “This Summary for Policymakers captures and summarizes the current state of climate science research and will serve as a valuable source of information for policymakers. It reflects the sizeable and robust body of knowledge regarding the physical science of climate change, including the finding that the Earth is warming and that human activities have very likely caused most of the warming of the last 50 years.”
The U.S. delegation to the Working Group I meeting included climate science experts from the National Aeronautics and Space Administration (NASA), the Department of Commerce's National Oceanic and Atmospheric Administration (NOAA), and the U.S. Department of State. The delegation's participation in the meeting followed significant U.S. involvement in the generation of the report, as numerous U.S. climate scientists were involved in its drafting and expert review. In addition, a NOAA climate expert, Dr. Susan Solomon, a senior scientist at the National Oceanic and Atmospheric Administration's Earth System Research Laboratory in Boulder, Colorado served as co-chair of Working Group I.
Other key U.S. officials also reacted to the report. U.S. Secretary of Energy Samuel Bodman said, "The Administration welcomes the Intergovernmental Panel on Climate Change report, which was developed through thousands of hours of research by leading U.S. and international scientists and informed by significant U.S. investments in advancing climate science research. Climate change is a global challenge that requires global solutions. Through President Bush's leadership, the U.S. government is taking action to curb the growth of greenhouse gas emissions and encouraging the development and deployment of clean energy technologies here in the United States and across the globe."
EPA Administrator Stephen Johnson said, “I congratulate my colleagues at the IPCC for their years of research, and look forward to using their scientific findings as we continue America’s efforts to reduce global greenhouse gas emissions,” said Through our commitment to sound science and innovation, the Bush Administration has built a solid foundation to address the environmental challenges of the 21st Century.”
Retired Navy Vice Adm. Conrad Lautenbacher, Ph.D., undersecretary of commerce for oceans and atmosphere and NOAA administrator said, “Without the diligent efforts by our scientists in the United States, these advances in knowledge of our planet’s climate would not have been possible. The U.S. Climate Change Science Program continues to set a high standard world-wide for the pertinent research it conducts. I would like to thank Dr. Susan Solomon and all of the scientists that contributed to the IPCC report.”
Access the complete Summary for Policymakers (click here). Access a webcast audio of the press conference presentation (click here). Access the IPCC website for additional information (click here). Access the Earth Negotiations Bulletin coverage of the IPCC meeting including a summary that will be available on 2/4/07 (click here). Access a release from the United Nations (click here). Access the U.S. fact sheet on the IPCC report (click here). Access a second fact sheet on the U.S. role in studying climate change (click here). Access a third fact sheet outlining the Bush record on addressing climate change (click here). [*Climate]