Leading Climate Scientists Advise White House on Global Warming
WASHINGTON [June 6, 2001] -- 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."
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 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.