Exaggerated and inaccurate claims about the threat from global warming risk undermining efforts to cut greenhouse gas emissions and contain climate change, senior scientists have told The Times.

Environmental lobbyists, politicians, researchers and journalists who distort climate science to support an agenda erode public understanding and play into the hands of sceptics, according to experts including a former government chief scientist.

Excessive statements about the decline of Arctic sea ice, severe weather events and the probability of extreme warming in the next century detract from the credibility of robust findings about climate change, they said.

Such claims can easily be rebutted by critics of global warming science to cast doubt on the whole field. They also confuse the public about what has been established as fact, and what is conjecture.

The experts all believe that global warming is a real phenomenon with serious consequences, and that action to curb emissions is urgently needed.

They fear, however, that the contribution of natural climate variations towards events such as storms, melting ice and heatwaves is too often overlooked, and that possible scenarios about future warming are misleadingly presented as fact.

“I worry a lot that NGOs [non=governmental organisations] are very much in the habit of doing exactly that,” said Professor Sir David King, director of the Smith School for Enterprise and the Environment at the University of Oxford, and a former government chief scientific adviser.

“When people overstate happenings that aren’t necessarily climate change-related, or set up as almost certainties things that are difficult to establish scientifically, it distracts from the science we do understand. The danger is they can be accused of scaremongering. Also, we can all become described as kind of left-wing greens.”

Vicky Pope, head of climate change advice at the Met Office, said: “It isn’t helpful to anybody to exaggerate the situation. It’s scary enough as it is.”

She was particularly critical of claims made by scientists and environmental groups two years ago, when observations showed that Arctic sea ice had declined to the lowest extent on record, 39 per cent below the average between 1979 and 2001. This led Mark Serreze, of the US National Snow and Ice Data Centre, to say that Arctic ice was “in a downward spiral and may have passed the point of no return”.

Dr Pope said that while climate change was a factor, normal variations also played a part, and it was always likely that ice would recover a little in subsequent years, as had happened. It was the long-term downward trend that mattered, rather than the figures for any one year, she added.

“The problem with saying that we’ve reached a tipping point is that when the extent starts to increase again — as it has — the sceptics will come along and say, ‘Well, it’s stopped’,” she said. “This is why it’s important we’re as objective as we can be, and use all the available evidence to make clear what’s actually happening, because neither of those claims is right.”

Myles Allen, head of the Climate Dynamics Group at the University of Oxford, said: “Some claims that were made about the ice anomaly were misleading. A lot of people said this is the beginning of the end of Arctic ice, and of course it recovered the following year and everybody looked a bit silly.” Dr Allen said that predictions of how the world was likely to warm also needed to be framed carefully. While there was little doubt that the Earth would get hotter, there were still many uncertainties about the precise extent and regional impact.

“I think we need to be very careful about purporting to be able to supply very detailed and apparently accurate information about how the climate will be in 50 or 100 years’ time, when what we’re really giving is a possible future climate,” he added.

“We’re not in a position to say how likely it is and what the chances are of it being different. There’s an understandable tendency to want to make climate change real for people and tell them what’s going to happen in their postcode, and that’s very dangerous because it gets beyond the level on which current models can operate.”

Chris Huntingford, of the Centre for Ecology and Hydrology, said: “I think the research scientists in general are extremely cautious about making projections for the future, but that caution is vital. We don’t dispute that warming is happening, but it’s important that the NGOs and other people interested in the issue don’t always pick the high scenario and present it as fact.”

Temperature trends of the past two decades have also been widely mis-interpreted to support particular points of view, the scientists said. Rapid warming in the 1990s, culminating in the hottest year on record in 1998, was erroneously used to suggest that climate change was accelerating. Since then, temperatures have stabilised, prompting sceptics to claim that global warming has stopped.

“In 1998, people thought the world was going to end, temperatures were going up so much,” Dr Pope said. “People pick up whatever makes their argument, but this works both ways. It’s the long-term trend that counts, which is continuing and inexorable.”

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