Correction appended.

Leaders of the Intergovernmental Panel on Climate Change apologized yesterday for making a "poorly substantiated" claim that Himalayan glaciers could disappear by 2035.

The finding was included in the group's 2007 report in an error-riddled paragraph that also misstates the total land area covered by Himalayan glaciers. Scientists who identified the mistakes say the IPCC report relied on news accounts that appear to misquote a scientific paper that estimated the glaciers could disappear by 2350, not 2035.

Experts said the gaffes that came to light in recent weeks don't undermine the IPCC report's main conclusion -- that evidence for global warming is "unequivocal," and human activities are driving the climate shift. But some said the incident indicates broader problems with the IPCC process and could provide fodder for climate skeptics.

Jeffrey Kargel, an adjunct professor at the University of Arizona who helped expose the IPCC's errors, said the botched projections were "extremely embarrassing and damaging."

"The damage was that IPCC had, or I think still has, such a stellar reputation that people view it as an authority -- as indeed they should -- and so they see a bullet that says Himalayan glaciers will disappear by 2035 and they take that as a fact," he said.

Kargel is one of four scientists who addressed the issue in a letter that will be published in the Jan. 29 issue of the journal Science. "These errors could have been avoided had the norms of scientific publication including peer review and concentration upon peer-reviewed work, been respected," write the researchers.

One of the letter signers, University of Trent geography professor Graham Cogley, said his rough calculations show that Himalayan glaciers would have to melt 10 times faster than they are now in order to disappear by 2035. "It's a date that doesn't stand up to casual scrutiny," he said.

Now, there's a danger that the uproar over the IPCC's erroneous paragraph could overshadow the scientific group's broader conclusions about the effects of climate change, said Ben Santer, a climate scientist at Lawrence Livermore National Laboratory.

A 'breakdown' in the peer-review process

"Focusing on a mouse and ignoring the elephant would be a mistake," he told reporters yesterday, especially since independent assessments by the National Academy of Sciences, the federal government and other sources echo the IPCC's overall findings.

Lonnie Thompson, a glaciologist at Ohio State University, agreed.

"Some errors can always get through the cracks," he said. "These issues are very specific, and they do not detract from the overall findings of the IPCC. There's a tremendous amount of data and evidence out there that points to human impact on our climate system."

But other experts who follow climate science and policy said they believe the IPCC should re-examine how it vets information when compiling its reports.

Rick Piltz, director of the watchdog organization Climate Science Watch, noted that two separate groups within the IPCC produced very different findings about Himalayan glaciers in their contribution to the science panel's Fourth Assessment Report.

The errors cropped up in a report by IPCC Working Group II, which "assesses the vulnerability of socio-economic and natural systems to climate change, negative and positive consequences of climate change and options for adapting to it." But Working Group I, which examines the state of climate science, did not make similar claims.

"The IPCC are all overloaded and this one just got by them," Piltz said. "The people from Working Group I with the real expertise did not look carefully at the Asia chapter of Working Group II. There's a cross-working group vetting problem that needs to be handled better in the future."

Roger Pielke, Jr., a professor of environmental studies at the University of Colorado, said scientists make mistakes all the time "and it isn't a big deal."

But Pielke also said he was concerned that, in this case, "a non-peer reviewed source [was] elevated to a finding by the IPCC," especially given Austrian glaciologist -- and IPCC Working Group I author -- Georg Kaser's recent assertion that he warned Working Group II of the error in 2006, and was ignored. That suggests "a breakdown in the peer-review process," Pielke said.

Pielke said his concern is heightened because he believes Working Group II also misrepresented his research about the link between climate change and monetary damages of natural disasters, highlighting a white paper produced for a conference he organized -- when ultimately, attendees at the conference "came up with a contrary conclusion to what the background paper said."

The current controversy comes as the IPCC begins work on its next major report, which is due in 2013.

"I think that ultimately, a better Fifth Assessment will emerge from this, and that will be the lasting legacy of it," Kargel said. "But it's really painful to see what's going on right now."

Correction: Jeffrey Kargel is an adjunct professor at the University of Arizona; an earlier version misstated his university affiliation.

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