Encouraging Signs on Climate Change Policy?

SAN FRANCISCO--The latest report of the Intergovernmental Panel on Climate Change (IPCC) is "unequivocal" in its statement that humans are responsible for 20th century climate change, but the scientist who headed up the new report says some of its most striking findings highlight local changes in a warming world.

For the first time, the IPCC evidence for climate change offers a detailed look at patterns in rainfall, wind, storm tracks, snow cover, melting sea and land ice and even extreme weather events such as the heat wave that overtook Europe in the summer of 2003, said Susan Solomon, the co-chair of the IPCC's Working Group 1, which reviews the scientific evidence for climate change.

In her Monday morning plenary address on the final day of the AAAS Annual Meeting, Solomon said a "discernable human influence now extends to other aspects of climate," noting that "we've moved beyond temperature into really looking at the planet as an earth system."

In a meeting with an international group of reporters after the address, Solomon said she was "incredibly encouraged" by the IPCC report's reception since its release in early February. When Solomon testified before the U.S. House of Representatives on 8 February, for instance, she said she heard from "a number of congressmen who said, 'I used to be a skeptic and now I'm a believer.' "

Since the IPCC's 4th Assessment Report from Working Group 1 was released in early February in Paris, Solomon has been traveling constantly to spread the word about the group's findings. Global average temperatures have risen .75 degrees Celsius (just over 1 degree Fahrenheit) since 1860. If greenhouse gas emissions continue at their current rate, temperatures may rise .2 degrees Celsius per decade over the next two decades, the report concludes.

On Sunday, the AAAS Board released a new statement about global climate change, saying the scientific evidence for change is clear and that "it is time to muster the political will for concerted action."

Although Solomon cautioned the audience to keep their eyes on the evidence for long-term, globally averaged climate trends, she said the past decade's high temperatures also strongly suggest a human hand in climate change. "The simple fact that we've had so many warm years consecutively in the...last 12 years is clearly evidence that something unusual is going on," she said. "It's not random."

Snow cover in the Northern Hemisphere and Arctic sea ice are already shrinking, and there have been fewer cold nights and more warm nights globally since the turn of the century, Solomon said. The IPCC report suggests it is "very likely" that heat waves and heavy rainfall events could become more common in the 21st century.

Solomon praised the arduous review process for the IPCC report, especially singling out the importance of "fresh faces" among the 152 authors. Three-quarters of the scientists had not worked on the IPCC 3rd Assessment, 25 percent had received their highest degree less than 10 years ago, and there were 35 percent more authors from the developing world, according to Solomon.

The report also received over 30,000 comments, which Solomon compared to the "dozen or so" comments that a peer-reviewed science paper might typically receive.

In her address and in meetings with reporters, Solomon deflected questions about whether governments have been slow to recognize the problem of global climate change, saying that it was her job to present the science and not become involved in policy debates. Two more reports from IPCC, one examining the impacts of climate change and the other looking at strategies to mitigate these impacts, will be published in the spring.

AAAS has produced a Web page of global climate change resources, including links to the IPCC report, recent research from the journal Science, and information from the AAAS Annual Meeting Town Hall on Climate Change. Click here for more information.

20 February 2007