The chairman of the leading climate change watchdog was informed that claims about melting Himalayan glaciers were false before the Copenhagen summit, The Times has learnt.

Rajendra Pachauri was told that the Intergovernmental Panel on Climate Change assessment that the glaciers would disappear by 2035 was wrong, but he waited two months to correct it. He failed to act despite learning that the claim had been refuted by several leading glaciologists.

The IPCC’s report underpinned the proposals at Copenhagen for drastic cuts in global emissions.

Dr Pachauri, who played a leading role at the summit, corrected the error last week after coming under media pressure. He told The Times on January 22 that he had only known about the error for a few days. He said: “I became aware of this when it was reported in the media about ten days ago. Before that, it was really not made known. Nobody brought it to my attention. There were statements, but we never looked at this 2035 number.”

Asked whether he had deliberately kept silent about the error to avoid embarrassment at Copenhagen, he said: “That’s ridiculous. It never came to my attention before the Copenhagen summit. It wasn’t in the public sphere.”

However, a prominent science journalist said that he had asked Dr Pachauri about the 2035 error last November. Pallava Bagla, who writes for Science journal, said he had asked Dr Pachauri about the error. He said that Dr Pachauri had replied: “I don’t have anything to add on glaciers.”

The Himalayan glaciers are so thick and at such high altitude that most glaciologists believe they would take several hundred years to melt at the present rate. Some are growing and many show little sign of change.

Dr Pachauri had previously dismissed a report by the Indian Government which said that glaciers might not be melting as much as had been feared. He described the report, which did not mention the 2035 error, as “voodoo science”.

Mr Bagla said he had informed Dr Pachauri that Graham Cogley, a professor at Ontario Trent University and a leading glaciologist, had dismissed the 2035 date as being wrong by at least 300 years. Professor Cogley believed the IPCC had misread the date in a 1996 report which said the glaciers could melt significantly by 2350.

Mr Pallava interviewed Dr Pachauri again this week for Science and asked him why he had decided to overlook the error before the Copenhagen summit. In the taped interview, Mr Pallava asked: “I pointed it out [the error] to you in several e-mails, several discussions, yet you decided to overlook it. Was that so that you did not want to destabilise what was happening in Copenhagen?”

Dr Pachauri replied: “Not at all, not at all. As it happens, we were all terribly preoccupied with a lot of events. We were working round the clock with several things that had to be done in Copenhagen. It was only when the story broke, I think in December, we decided to, well, early this month — as a matter of fact, I can give you the exact dates — early in January that we decided to go into it and we moved very fast.

“And within three or four days, we were able to come up with a clear and a very honest and objective assessment of what had happened. So I think this presumption on your part or on the part of any others is totally wrong. We are certainly never — and I can say this categorically — ever going to do anything other than what is truthful and what upholds the veracity of science.”

Dr Pacharui has also been accused of using the error to win grants worth hundreds of thousands of pounds.

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