One of the most alarming conclusions from the Intergovernmental Panel on Climate Change (IPCC), a widely respected organization established by the United Nations, is that glaciers in the Himalayas could be gone 25 years from now, eliminating a primary source of water for hundreds of millions of people. But a number of glaciologists have argued that this conclusion is wrong, and now the IPCC admits that the conclusion is largely unsubstantiated, based on news reports rather than published, peer-reviewed scientific studies.
In a statement released on Wednesday, the IPCC admitted that the Working Group II report, “Impacts, Adaptation and Vulnerability,” published in the IPCC’s Fourth Assessment Report (2007), contains a claim that “refers to poorly substantiated estimates. ” The statement also said “the clear and well-established standards of evidence, required by the IPCC procedure, were not applied properly.” The statement did not quote the error, but it did cite the section of the report that refers to Himalayan glaciers. Christopher Field, director of the Carnegie Institution’s Department of Global Ecology, who is now in charge of Working Group II, confirms that the error was related to the claim that the glaciers could disappear by 2035.
The disappearance of the glaciers would require temperatures far higher than those predicted in even the most dire global warming scenarios, says Georg Kaser, professor at the Institut für Geographie der Universität, Innsbruck. The Himalayas would have to heat up by 18 degrees Celsius and stay there for the highest glaciers to melt–most climate change scenarios expect only a few degrees of warming over the next century.
The mistake has called into question the credibility of the IPCC, which has been considered an authoritative source for information about climate change because of its policy of carefully reviewing and analyzing hundreds and even thousands of published, peer-reviewed scientific studies. But the scientists who uncovered the error say that the mistake, and the reliance on news reports and unpublished studies, is rare. “I don’t think it ought to affect the credibility of the edifice as a whole,” says J. Graham Cogley, professor of geography at Trent University, who was key to identifying the original sources of the information in the IPCC report.
The error has been traced to the fact that the IPCC permits the citation of non-peer-reviewed sources, called “grey literature,” in cases where peer-reviewed data is not available. It requires that these sources be carefully scrutinized, but that didn’t happen in this case. The process has “gone spectacularly wrong in this particular instance,” Cogley says.