The shame of the climate-change deniers

More than 10,000 reputable scientists believe in man-made global warming; seven doubt it

Rev up your SUV. Jump in a plane to New York for a morning meeting about how global warming is a "scam", and head back in the afternoon. When you get back to your empty centrally-heated house, turn on that gas fire - and toss a copy of the Kyoto treaty on to the flames. This was the message this weekend from David Bellamy, still routinely dubbed one of Britain's "leading environmentalists". Global warming? Chill, baby, chill.

Rev up your SUV. Jump in a plane to New York for a morning meeting about how global warming is a "scam", and head back in the afternoon. When you get back to your empty centrally-heated house, turn on that gas fire - and toss a copy of the Kyoto treaty on to the flames. This was the message this weekend from David Bellamy, still routinely dubbed one of Britain's "leading environmentalists". Global warming? Chill, baby, chill.

For more than a decade now, the climate change deniers have been in retreat, humbled by the thumping weight of scientific evidence against them. More than 10,000 reputable, peer-reviewed climate scientists believe the evidence that rapid shifts in global temperature are caused by human activity. Seven - that's seven - doubt it. But Bellamy's increasingly erratic outbursts over the past year have given the beleaguered band of anti-environmentalists a fresh gallon of petrol to fuel their flailing pro-carbon crusade. "My belief is that global warming is a largely natural phenomenon and the world is in danger of wasting stupendous amounts of money on trying to fix something that can't be fixed and doesn't need to be anyway," he said, producing ecstasy in the offices of dozens of J R Ewings.

Whenever a journalist writes about man-made climate change, a cascade of e-mails from across the Atlantic floods in. The Arctic ice-sheet has lost half its thickness in the past 30 years? The 1990s were the hottest decade of the entire millennium? The level of carbon in the atmosphere has been consistently rising over this period? "Coincidence!" they cry.

They claim that anthropogenic climate change is "unproven". They send "briefing papers" from corporate-funded think tanks, designed to give the impression that this is "a controversial debate with two sides", and the UN Inter-Governmental Panel on Climate Change (IPCC) - consisting of the world's 2,500 best climatologists - was "fixed". They claim that they are "debunking myths" - but when you look at the evidence, it becomes clear that they entertain more myths than the ancient Greeks.

Their first claim is intuitively appealing. It goes like this: climate changes naturally in slow, inexorable cycles over millennia. It is simply egotism on the part of human beings to assume that our puny emissions have any effect at all.

At first, this sounds persuasive. Aren't we tiny? Isn't the world huge? I put this to Geoff Jenkins, Britain's leading climatologist, based at the Hadley Centre. He replied: "Of course it is true that many factors affect the climate, from changes in the sun to volcanoes. But levels of carbon are a key factor as well."

Everyone agrees there is a natural greenhouse effect, he explains. It's simple: carbon and water vapour in the atmosphere trap heat, and they keep us about 3C warmer. This is basic science. All climatologists are saying is that if you increase one of those properties - carbon - then more heat will be trapped and the temperature will rise further. "Nobody denies the natural greenhouse effect and nobody denies that humans have massively increased carbon emissions since the Industrial Revolution," says Dr Jenkins, "so why does anybody dispute this unnatural greenhouse effect, especially with all the evidence of its effects?"

Dr Jenkins invited Professor Bellamy to the Hadley Centre to explain to him that levels of carbon in the atmosphere are now higher than they have been for the past 420,000 years - with an obvious impact on the greenhouse effect. "He doesn't seem to have grasped basic scientific evidence," says Dr Jenkins, a mild-tempered man, about the meeting. "When you understand how the atmosphere works in even a rudimentary fashion, his argument doesn't hold water."

Because the deniers are so out of tune with this overwhelming scientific consensus, they have been forced to turn on climatology itself. They say that - out of hunger for research grants - climatologists have all begun to skew their evidence. The more disastrous their predictions, the more money they are given by government agencies, so you can't trust what they say.

This is the opposite of the truth. Swaths of the most reputable climate change research has been funded by the US government. Who can seriously claim the White House of George Bush is eager for proof of climate change? In fact, there is political pressure - but it is for scientists to play down the evidence of climate change. For any scientist prepared to defy the evidence and deny anthropogenic climate change, there are huge "grants" and "consultancies" waiting for you from gas and oil companies.

The deniers then take a different tack: in the 1970s, they say, climatologists were warning about the dangers of a "new Ice Age". Now they say we'll boil. Isn't the truth that they don't know?

This is largely a myth. A handful of scientists in the 1970s believed they were witnessing a process of "global cooling" that - if extrapolated for a very long period - would lead to an Ice Age. They said this was simply a possibility worth exploring, and they admitted the evidence was woefully insufficient. A few populist magazines ran with the idea but the scientists always expressed extreme uncertainty.

Today, by contrast, there is a near-complete scientific consensus that man-made global warming is happening and could be disastrous. The evidence is not patchy and partial, as the "global cooling" scientists always admitted theirs was; it is massive and overwhelming.

There are countless myths, and it would take a whole issue of The Independent to debunk them all. But these arguments are distracting dances on the precipice of a volcano. The IPCC says we are now poised on the brink of a temperature rise in the next century of 1.4C to 5.8C - bigger than the difference between the present day and the end of the last Ice Age. This will, they explain, "translate into climate-related impacts that are much larger and faster than any that have occurred during the 10,000-year history of civilisation." Nobody knows where this will lead.

The climate-change deniers are rapidly ending up with as much intellectual credibility as creationists and Flat Earthers. Indeed, given that 25,000 people died in Europe in the 2003 heatwave caused by anthropogenic climate change, given that the genocide unfolding in Darfur has been exacerbated by the stresses of climate change, given that Bangladesh may disappear beneath the rising seas in the next century, they are nudging close to having the moral credibility of Holocaust deniers. They are denying the reality of a force that - unless we change the way we live pretty fast - will kill millions.

j.hari@independent.co.uk