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By JEFFREY BALL And KEITH JOHNSON

Some top officials of a Nobel Prize-winning climate-science organization are acknowledging the panel made some mistakes amid a string of recent revelations questioning the accuracy of some of the information in its influential reports.



Officials of the Intergovernmental Panel on Climate Change, a United Nations-sponsored network of scientists whose reports strongly influence global policy on greenhouse-gas emissions, initially played down some of the allegations. Increasingly, however, they are acknowledging the panel's mistakes and saying it needs to tighten its procedures.

"This has not increased the credibility of the IPCC," said Ottmar Edenhofer, a German economist who is co-chairing one of the main sections of the IPCC's next big climate-change report, due out in 2013 and 2014. "There is some room for improvement."

Scientists and other experts involved in the IPCC say most of the information assembled and reported by the organization is valid. They say the revelations don't impugn the IPCC's main conclusions: that climate change is largely due to man-made greenhouse-gas emissions and could have dangerous consequences. Though they say each revelation itself is small, they worry that the continuing string of them is damaging the IPCC's credibility—not just with experts who question the premise of human-induced climate change, but with the public at large.

In citing climate change as an important issue, a U.N. conference in December in Copenhagen didn't rely "on the precise date of the demise of Himalayan glaciers, or African agriculture" to tackle global warming, says IPCC Vice Chairman Jean-Pascal van Ypersele, mentioning subjects that have generated criticism of the group. "It's the body of evidence" in the whole report that makes the case for action.

Officials say they don't know of additional mistakes in the IPCC's seminal 2007 report, but that, given that the report runs more than 3,000 pages, additional mistakes may come to light. "I do not expect serious mistakes," Mr. Edenhofer said. "But I'm quite sure that if people read the 3,000 pages, there will be some more mistakes."



A number of climate-change skeptics and public officials, including U.S. Sen. John Barrasso, a Wyoming Republican, have said the IPCC's chairman, Rajendra Pachauri, should resign. IPCC officials said Mr. Pachauri was traveling and unavailable to comment Tuesday.

A U.N. spokesman said IPCC rules don't appear to give the U.N. secretary-general authority to dismiss the IPCC chairman, and noted that Secretary-General Ban Ki-moon hasn't called for Mr. Pachauri's departure. Under IPCC rules, the panel's members—national-government officials—choose the IPCC chairman.

That officials with the IPCC are on the defensive is a big turnabout from 2007, when the organization shared a Nobel Peace Prize with former U.S. Vice President Al Gore. The IPCC got the prize for its 2007 report concluding that climate change is "unequivocal" and is "very likely" caused by man. The report motivated countries around the world to push for limits on greenhouse-gas emissions.

But recent revelations have undercut the Geneva-based group. Among them: Emails were released on the Internet in which leading scientists at an influential U.K. climate-science institute seemed to squelch dissent from researchers who disagreed with them; and the 2007 report incorrectly said that Himalayan glaciers could disappear as soon as 2035.

Thousands of scientists and other experts volunteer their time with the IPCC to issue joint pronouncements every five or six years about one of the most complex scientific fields. The group, established by the U.N. Environment Program and the U.N.'s World Meteorological Organization, is administered by a paid staff of only a few dozen and doesn't do any scientific research itself; its job is to assess work done by others, providing information for policy makers.

Experts involved in writing IPCC reports say the 2007 document's errors point up gaps in the group's checks and balances. Mr. Edenhofer said IPCC reports have to be more careful about noting uncertainties surrounding information that hasn't been subjected to peer review.

The most glaring mistake in the 2007 report is the claim that Himalayan glaciers could disappear by 2035, several IPCC authors say. That claim wasn't based on any peer-reviewed scientific paper, but on a decade-old interview given by an Indian glacier expert.

Chris Field, co-chair of another section of the IPCC's next big report and director of the department of global ecology at the Carnegie Institution for Science in Palo Alto, Calif., said he thinks the IPCC would have caught the error had the team of scientists writing the report chapter on the Himalayas included a glacier expert. It didn't.

U.S. officials said they don't believe revelations of mistakes in IPCC reports undermine cause for concern about global warming. "It's not useful when mistakes are made, but the overwhelming body of evidence [on climate change] is not disturbed by those events," Todd Stern, the Obama administration's top international negotiator on climate-change policy, told an audience Tuesday at the Center for American Progress, a left-leaning Washington think tank. "It's nothing short of crazy for us to put our heads in the sand and do nothing" about climate change.
—Guy Chazan and Ian Talley contributed to this article.