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UW Today
September 30, 2013

The United Nations Intergovernmental Panel on Climate Change late last week released its summary for policy-makers, the Cliffs Notes version of the massive international assessment released about every six years.

The full text of the fifth IPCC report was released today, and University of Washington atmospheric science professors Dennis Hartmann and Chris Bretherton were among 209 researchers from 39 countries who were lead authors on the 900-page report.

“Warming is unequivocal,” Hartmann said Friday at a news conference in Sweden. He was a coordinating lead author for Chapter 2, Observations of Atmosphere and Surface, which reviews the evidence for global warming in temperature records. Hartmann also helped draft the technical summary and the summary for policymakers, and was in Stockholm last week for the final line-by-line reviews of the 36-page summary document.

“For the most part the conclusions of previous IPCC assessments can be given with even more certainty,” Hartmann commented by e-mail. “The surface of Earth is warming and humans are responsible.”

The new report moves from asking whether warming has occurred, he said, to determining exactly how much warming has taken place since 1750, around the beginning of the industrial age. This assessment also makes more forward-looking statements for policymakers.