There are many kinds of truth. Al Gore was poleaxed by an inconvenient one yesterday.

The former US Vice-President, who became an unlikely figurehead for the green movement after narrating the Oscar-winning documentary An Inconvenient Truth, became entangled in a new climate change “spin” row.

Mr Gore, speaking at the Copenhagen climate change summit, stated the latest research showed that the Arctic could be completely ice-free in five years.

In his speech, Mr Gore told the conference: “These figures are fresh. Some of the models suggest to Dr [Wieslav] Maslowski that there is a 75 per cent chance that the entire north polar ice cap, during the summer months, could be completely ice-free within five to seven years.”

However, the climatologist whose work Mr Gore was relying upon dropped the former Vice-President in the water with an icy blast.

“It’s unclear to me how this figure was arrived at,” Dr Maslowski said. “I would never try to estimate likelihood at anything as exact as this.”

Mr Gore’s office later admitted that the 75 per cent figure was one used by Dr Maslowksi as a “ballpark figure” several years ago in a conversation with Mr Gore.

The embarrassing error cast another shadow over the conference after the controversy over the hacked e-mails from the University of East Anglia’s Climate Research Unit, which appeared to suggest that scientists had manipulated data to strengthen their argument that human activities were causing global warming.

Mr Gore is not the only titan of the world stage finding Copenhagen to be a tricky deal.

World leaders — with Gordon Brown arriving tonight in the vanguard — are facing the humiliating prospect of having little of substance to sign on Friday, when they are supposed to be clinching an historic deal.

Meanwhile, five hours of negotiating time were lost yesterday when developing countries walked out in protest over the lack of progress on their demand for legally binding emissions targets from rich nations. The move underlined the distrust between rich and poor countries over the proposed legal framework for the deal.

Last night key elements of the proposed deal were unravelling. British officials said they were no longer confident that it would contain specific commitments from individual countries on payments to a global fund to help poor nations to adapt to climate change while the draft text on protecting rainforests has also been weakened.

Even the long-term target of ending net deforestation by 2030 has been placed in square brackets, meaning that the date could be deferred. An international monitoring system to identify illegal logging is now described in the text as optional, where before it was compulsory. Negotiators are also unable to agree on a date for a global peak in greenhouse emissions.

Perhaps Mr Gore had felt the need to gild the lily to buttress resolve. But his speech was roundly criticised by members of the climate science community. “This is an exaggeration that opens the science up to criticism from sceptics,” Professor Jim Overland, a leading oceanographer at the US National Oceanic and Atmospheric Administration said.

“You really don’t need to exaggerate the changes in the Arctic.”

Others said that, even if quoted correctly, Dr Maslowski’s six-year projection for near-ice-free conditions is at the extreme end of the scale. Most climate scientists agree that a 20 to 30-year timescale is more likely for the near-disappearance of sea ice.

“Maslowski’s work is very well respected, but he’s a bit out on a limb,” said Professor Peter Wadhams, a specialist in ocean physics at the University of Cambridge.

Dr Maslowki, who works at the US Naval Postgraduate School in California, said that his latest results give a six-year projection for the melting of 80 per cent of the ice, but he said he expects some ice to remain beyond 2020.

He added: “I was very explicit that we were talking about near-ice-free conditions and not completely ice-free conditions in the northern ocean. I would never try to estimate likelihood at anything as exact as this,” he said. “It’s unclear to me how this figure was arrived at, based on the information I provided to Al Gore’s office.”

Richard Lindzen, a climate scientist at the Massachusets Institute of Technology who does not believe that global warming is largely caused by man, said: “He’s just extrapolated from 2007, when there was a big retreat, and got zero.”

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