Claims Himalayan glaciers could melt by 2035 were false, says UN scientist

One paragraph, buried in 3,000 pages of reports and published almost three years ago, has humbled the head of the UN's Intergovernmental Panel on Climate Change. Facing global outcry, Rajendra Pachauri backed down and apologised today for a disputed IPCC claim that there was a very high chance the Himalayan glaciers would melt away by 2035. The assertion, now discredited, was included in the most recent IPCC report assessing climate change science, published in 2007. Those reports are widely credited with convincing the world that human activity was causing global warming. But Pachauri admitted in an IPCC statement (pdf) that in this case "the clear and well-established standards of evidence required by the IPCC procedures were not applied properly", and "poorly substantiated estimates" of the speed of glacier melting had made it into print. He had stridently defended the report in recent months. Furthermore, the Guardian has discovered the claim was questioned by the Japanese government before publication, and by other scientists. Pachauri's statement is a reprimand for some IPCC scientists involved. It is also bound to encourage critics of the panel to redouble efforts to undermine its scientific reputation. However, many scientists say evidence for man-made climate change remains compelling and note that the 2035 claim did not appear in the more widely read "summary for policymakers". The offending paragraph, in the panel's fourth assessment report on the impacts of climate change, said: "Glaciers in the Himalaya are receding faster than in any other part of the world and, if the present rate continues, the likelihood of them disappearing by the year 2035 and perhaps sooner is very high." In IPCC terminology a "very high" likelihood has a specific meaning: more than a 90% chance of coming true. The report's only quoted source for the claim was a 2005 campaigning report from the environment group WWF. In turn, the WWF report's only source was remarks made in 1999 by a leading Indian glaciologist, Syed Hasnain, then vice-chancellor of Jawaharlal Nehru University in Delhi, to journalists at two magazines, New Scientist in London, and Down to Earth in New Delhi. Hasnain had never submitted the suggestion of such an early demise to a scientific journal because, he said last week, it had always been "speculative". How this made it to the august pages of the IPCC report remains unclear. But the IPCC text is almost identical to that in the Down to Earth article in April 1999. WWF said today it regretted "any confusion caused" and would amend its report. The panel is yet to make a similar commitment. Hasnain is currently employed as a senior fellow at an Indian research institute, the The Energy and Resources Institute, whose director is Pachauri. Glaciologists who spoke to the Guardian say Himalayan glaciers contain so much ice it will be 300 years before it vanishes. The affair raises serious questions about the rigour of the IPCC's process of sifting and assessing the thousands of research findings it includes in its reports. It also raises questions about the competence of Pachauri, who angrily defended the report's conclusions about Himalayan glaciers after they were called "alarmist" last autumn by India's environment minister, Jairam Ramesh. Pachauri accused Ramesh of relying on "voodoo science", called the minister "extremely arrogant" and said Ramesh's claims were "not peer reviewed". It is now clear that it was the panel's claims that were not reviewed. The author of the part of the panel's report, another Indian glaciologist, Murari Lal, last week defended inclusion of 2035, saying "the error if any lies with Dr Hasnain's assertion". Pachauri's statement repudiates that position. He said he "regrets the poor application of well-established IPCC procedures in this instance". One person who has not spoken is the co-chairman of the impacts assessment report, Martin Parry, who was unavailable for comment. But his successor, Chris Field of the Carnegie Institution in Stanford, California, said it was a powerful reminder of "carefully applying the well-established IPCC principles to every statement in every paragraph". "Glaciergate" has brought into the open splits between authors of the four different IPCC reports, produced every five or so years. However, Bob Ward, policy director at the Grantham Research Institute on Climate Change at the LSE, said: "We should be cautious about making sweeping statements about the IPCC based on a single error." • This article was amended on Wednesday 27 January 2010. We referred incorrectly to the Tata Energy Research Institute. The organisation that formerly had that name has been The Energy and Resources Institute since 2003. This has been corrected.