How Do We Know What We Know About Climate Change?

American Geophysical Union, Fall Meeting 2007

What do we really know about global warming, and how do we know it? An international group of experts has just completed a thorough assessment of recent research on climate change science.

This sobering document, published by the Intergovernmental Panel on Climate Change (IPCC) in 2007, calls warming of the climate system "unequivocal."

But despite the international media coverage the report received this year and the awarding to the IPCC a share of the Nobel Peace Prize, surveys and opinion polls suggest that misconceptions about the state of climate change research abound. Richard Somerville, a Scripps Institution of Oceanography at UC San Diego climate researcher and a coordinating lead author of the IPCC report, will summarize the key scientific findings of the IPCC report and explain why the scientists have reached these conclusions. He will also discuss the challenges faced by scientists and the media in making these conclusions understood by the public.

The IPCC's Fourth Assessment Report released this year attributes most of the observed recent global warming to human activities, with a confidence level of 90 percent or more. At the same time, new research shows that previous IPCC projections have not exaggerated the climate changes observed since 1990 and may even have underestimated some aspects of them. Somerville will discuss the implications for rising sea level, hurricanes and other phenomena as human activities continue to modify the climate system.

The IPCC has become the de facto voice of the mainstream scientific community, as the world seeks to understand the findings of climate science and their relevance to public policy. The panel has been immensely influential in the debate over human-caused climate change, and it has affected efforts to limit the emissions of gases that increase the greenhouse effect and cause global warming. The IPCC was established in 1988 to provide an authoritative assessment of results from climate science as an input to policymakers. Its mandate is to assess research, not to do research.

Its reports are policy-relevant but not policy-prescriptive. Thousands of scientists throughout the world have contributed to the IPCC effort. The latest (2007) IPCC reports are available at http://www.ipcc.ch.