Climate-Change Group IPCC Moves to Fix Crisis Damage - WSJ.com
Mr. Pachauri describes the IPCC's record as "impeccable." Still, he said, the IPCC's reforms will aim to "ensure that even the slightest possibility of someone not adhering to procedures is eliminated completely. We just have to act like monitors at every stage."
"There is a very broad and deep consensus that I buy into that we're producing too much CO2 and it's going to cause problems eventually," said John H. Marburger III, former science adviser to President George W. Bush. Many details remain uncertain, he said, but "I think it's unequivocal that there is a human component."
Mr. Mann said in an email interview, "I was not pushing 'hard' for anything of the sort." The chapter's authors, he said, "engaged in a robust, good faith discussion of what the level of certainty was." Mr. Mann also noted that his original 1998 hockey-stick paper stressed the uncertainties involved in reconstructing past temperatures.
Some researchers continued to feel pressure to boil down science as work began on the IPCC's fourth major report, published in 2007. Things that are "very difficult to quantify must be quantified to keep the policy makers happy," Mr. Alley, the geoscientist, who teaches at Penn State, said in an interview. "It's a very frustrating thing."
Mr. Alley walked that tightrope in helping write the chapter covering his specialty: the degree to which massive Greenland and antarctic ice sheets might melt, raising sea levels. The problem, he said: "Ice-sheet models are not very good."
Many conversations with policy makers—including Mr. Gore, the senators in Greenland and Christian Gaudin, a French senator—left the clear impression that "we scientists had better get better numbers," said Mr. Alley, adding that he understands their desire for detail.
So the scientists put numbers into the 2007 study, along with a big caveat—what Mr. Alley calls a "punt." The study took into account things like glacier melt in most of the world, but it noted that it excluded what's happening in the Greenland and Antarctic ice sheets, which "we can't predict," Mr. Alley said.
Inevitably, Mr. Alley said, some people have cited the numbers without that caveat.
A spokeswoman for Mr. Gore said he understands the uncertainties, and that he pointed out in statements "that there was essentially an asterisk" on the 2007 report's sea-level projections. "As he understands the situation from the ice-science community, the uncertainty in sea level applies in both directions," meaning sea-level rise could be greater or smaller than projected, her statement said.