The report comes as President George W. Bush prepares to travel to Europe next week to discuss alternatives to the Kyoto Protocol for combating climate change. In the 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. Some of the panelists had been skeptical about the reality of global warming before participating in the review. 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. 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.
Temperatures are, in fact, rising.
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 White House requested the report last month to help President Bush prepare for a meeting in July where government representatives will continue negotiations on the Kyoto Protocol, an international treaty that would require all developed countries to reduce their greenhouse gas emissions. Bush had asked for help in interpreting the conclusions of the IPCC, which issued a new, dire estimates of the rate climate change in January. 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 panel managed to complete their review before President Bush's scheduled meeting next week with European leaders in Goteborg, Sweden.