THE impact of global warming has been exaggerated by some scientists and there is an urgent need for more honest disclosure of the uncertainty of predictions about the rate of climate change, according to the British Government's chief scientific adviser.
John Beddington was speaking after an admission by the Intergovernmental Panel on Climate Change (IPCC) that it grossly over-stated the rate at which Himalayan glaciers were receding.
Professor Beddington said that climate scientists should be less hostile to sceptics who questioned man-made global warming. He condemned scientists who refused to publish the data underpinning their reports.
He said that public confidence in climate science would be improved if there were more openness about its uncertainties, even if that meant admitting that sceptics had been right on some hotly disputed issues.
"I don't think it's healthy to dismiss proper scepticism. Science grows and improves in the light of criticism. There is a fundamental uncertainty about climate change prediction that can't be changed," he said.
Professor Beddington said that the false claim in the IPCC's 2007 report that the glaciers would disappear by 2035 had exposed a wider problem with the way that some evidence was presented.
"Certain unqualified statements have been unfortunate. We have a problem in communicating uncertainty. There's definitely an issue there. If there wasn't, there wouldn't be the level of scepticism. All of these predictions have to be caveated by saying, `There's a level of uncertainty about that'."
Professor Beddington said that particular caution was needed when communicating predictions about climate change made with the help of computer models. "It's unchallengeable that CO2 traps heat and warms the Earth and that burning fossil fuels shoves billions of tonnes of CO2 into the atmosphere. But where you can get challenges is on the speed of change.
"When you get into large-scale climate modelling there are quite substantial uncertainties. On the rate of change and the local effects, there are uncertainties both in terms of empirical evidence and the climate models themselves."
He said that it was wrong for scientists to refuse to disclose their data to their critics: "I think, wherever possible, we should try to ensure there is openness and that source material is available for the whole scientific community."
He added: "There is a danger that people can manipulate the data, but the benefits from being open far outweigh that danger."
Professor Phil Jones, the director of the University of East Anglia's Climatic Research Unit and a contributor to the IPCC's reports, has been forced to stand down while an investigation takes place into leaked e-mails allegedly showing that he attempted to conceal data.
In response to one request for data Professor Jones wrote: "We have 25 or so years invested in the work. Why should I make the data available to you when your aim is to try and find something wrong with it?"
Professor Beddington said that uncertainty about some aspects of climate science should not be used as an excuse for inaction: "Some people ask why we should act when scientists say they are only 90 per cent certain about the problem. But would you get on a plane that had a 10 per cent chance of crashing?"
Mike Hulme, Professor of Climate Change at the University of East Anglia, said: "Climate scientists get kudos from working on an issue in the public eye but with that kudos comes responsibility. Being open with data is part of that responsibility."
He criticised Rajendra Pachauri, the IPCC chairman, for his dismissive response last November to research suggesting that the UN body had overstated the threat to the glaciers. Mr Pachauri described it as "voodoo science".
Professor Hulme said: "Pachauri's choice of words has not been good. The question of whether he is the right person to lead the IPCC is for the 193 countries who make up its governing body. It's a political decision."