Thursday, Jan. 18, 2007 | When scientists, policymakers and the media discuss global warming and its effects, they lean heavily on one report to explain how humans are heating the planet.

It comes from the Intergovernmental Panel on Climate Change that includes hundreds of contributing scientists from Canada to Senegal to Thailand — and from San Diego.

Three of the 39 U.S. scientists involved in the landmark international report are local: Richard Somerville, a theoretical meteorologist; Lynne Talley, an oceanography professor; and Veerabhadran Ramanathan, an applied ocean sciences professor. All work at Scripps Institution of Oceanography at the University of California, San Diego.

They have contributed to a highly awaited report, one that synthesizes hundreds of published research papers. It provides the consensus view on the past, present and future of climate change: how much warming is expected in the next century, what’s causing it, what its impacts will be. Think of it as the periodic census of climate science. Scientists simply call it “the IPCC.”

“It has been for a long time the gold standard of information for the media and scientists and the public,” Somerville said. “It’s the nearest thing we’re going to get to a summary of the mainstream scientific consensus.”

Somerville, one of two coordinating lead authors of a chapter on climate change science’s history, estimates he has spent half of his time during the last three years working on the report, which will be released Feb. 2.

“We’re assessing research. Where there’s agreed science it says so. Where there’s substantial uncertainty remaining it says that,” he said.

Talley describes the process as the “most intensely reviewed” she’s ever participated in. She’ll use its publication to launch a series of public seminars on climate change.

“This is really taking the published literature and published models and saying: ‘Where are we going?’” she said. “It also doesn’t overreach. That’s what’s so important.”

The report that Somerville, Talley and Ramanathan are contributing to addresses the scientific basis behind climate change. Two other reports, which will be released later this year, address warming’s socio-economic impacts and mitigation challenges.

The first report comes at a critical time in the country’s growing acceptance of the scientific consensus on global warming. Polls show that Californians — both Republicans and Democrats — are increasingly aware of the threats global warming poses. The nation’s discourse on global warming has advanced from a debate about whether humans are warming the planet to questions now about its many impacts and how to address them.

The science of climate change has also been refined in the six years since the last report. It is increasingly predicting regional impacts of global warming, though many uncertainties remain. Will global warming fuel stronger hurricanes? Would a Pacific hurricane be more likely to strike San Diego in a warmer world? Will the belt of deserts that wraps around the globe expand to include San Diego?

“There are some big changes from the [previous report], in that the science has moved a lot further along,” Talley said.

The IPCC was formed in 1988 by the United Nations Environment Programme and the World Meteorological Organization. It has previously issued three reports, in 1990, 1995 and 2001. The last report was important because it acknowledged that humans were warming the planet, Talley said. The U.N.’s first two reports had been cautious in making that connection.

While the latest U.N. report won’t break new ground — it represents a synthesis, not new research — it should provide the scientific basis for the public to begin asking how global warming will impact them personally, said Tim Barnett, a Scripps marine physicist. He has contributed to two previous reports, but not the latest.

“I think [the public] will learn what the consensus of the world’s scientific community is — without spin,” Barnett said. “When the realization of what’s coming begins to dawn on people, oh boy.”

The report is held up as an independent, nonbiased source of information. But it has been criticized by one participant, a National Hurricane Center scientist who withdrew from the process, saying it had become too politicized.

Somerville said the report had not become political, but also noted his hope that it serves as an impetus spurring for federal action to address climate change.

“I’ve seen a great lack of politics,” he said. “We never talk about politics, we never talk about Kyoto. Our job is climate science.”

The report will be introduced, though, into a polarized political debate. While many European governments have begun addressing the planet’s warming climate, the Bush Administration has downplayed the link between human activity and climate change. The Democratic-controlled Congress has signaled a new willingness to address the issue.

Because the report represents scientific middle ground, it is not guaranteed to support those who want to address warming through federal policy changes, said Roger Pielke Jr., an environmental studies professor at the University of Colorado, who studies the politics of climate science and did not participate in the IPCC process.

“I would think it could work both ways,” Pielke said. “[The report] never has been overly alarmist. From that standpoint, it hasn’t in the past supported the more dire pronouncements made by Al Gore or (prominent NASA climate scientist) James Hansen. There’s plenty of ammunition in the covers for people of all political colors.”

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