By Simon Cox and Richard Vadon
Amphibians are dying out the world over
Hardly a day goes by without a new dire warning about climate change. But some claims are more extreme than others, giving rise to fears that the problem is being oversold and damaging the issue.
How much has the planet warmed up over the past century? Most people reckon between two and three degrees. They are not even close. The real figure, according to the Intergovernmental Panel on Climate Change (IPCC) is 0.6C.
It's not surprising most people get it wrong. We are bombarded by stories warning us that global warming is out of control. The most extreme warn us we will be living in a tropical Britain where malaria is rife and Norfolk has disappeared altogether.
Dr Hans Von Storch, a leading German climate scientist and fervent believer in global warming, is convinced the effect of climate change is being exaggerated.
"The alarmists think that climate change is something extremely dangerous, extremely bad and that overselling a little bit, if it serves a good purpose, is not that bad."
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Why do the stories that reach the public focus only on the most frightening climate change scenarios? We decided to find out for a BBC Radio 4 documentary.
In 2005 the scientific journal Nature published the first results of a study by Climateprediction.net, a group of UK climate scientists. They had been testing what effect doubling the amount of carbon dioxide (CO2) in the atmosphere would have on temperature.
The vast majority of their results showed that doubling CO2 would lead to a temperature rise of about 3C. Such an increase would have a major impact on the planet. The scientists of Climateprediction.net say that is what you would expect their model to produce, and many other scientists have produced similar results. However a tiny percentage of the models showed very high levels of warming - the highest result was a startling 11C.
When it came to selling the story to journalists, the press release only mentioned one figure - 11C.
The ensuing broadsheet headlines were predictably apocalyptic, from "Global warming is twice as bad as previously thought" to "Screensaver weather trial predicts 10C rise in British temperatures".
They may be dramatic but they are also wrong. Dr Myles Allen, principal investigator at Climateprediction.net, blames the media.
"If journalists decide to embroider on a press release without referring to the paper which the press release is about, then that's really the journalists' problem. We can't as scientists guard against that."
But is the media solely to blame? We asked several climate scientists to read the paper and the press release publicising it. All were critical of the prominence given to the prediction that the world could heat up by 11C.
"I agree the 11C figure was unreasonably hyped. It's a difficult line for all scientists to tread, as we need something 'exciting' to have any chance of publishing... to justify our funding," one scientist wrote us.
Not easy being green
Even government agencies have been criticised for overselling climate change. When the Environment Agency publicised research on global warming over the next 1,000 years, it predicted cataclysmic change; temperature rises of 15C and sea levels increasing by 11m. The agency said action was needed now.
But this isn't how the study's lead author, Dr Tim Lenton sees it. His research shows if you did nothing for a century you would still only get a fraction of the worst case scenario. He says there's consternation among scientists at the presentation of their science by the Environment Agency. Scientists would have liked to have seen a more balanced picture presented.
Clive Bates, head of environment policy at the agency, says it's simply a case of Dr Lenton not understanding the way the media works. "He was involved in signing off the press release, there is nothing in there that is actually incorrect."
The difficulty for climate scientists is that their work has a political dimension. Take the study carried out by researchers at the Cloud Forest Preserve in Costa Rica. It claimed a link between climate change and frog extinctions. The lead scientist Dr Alan Pounds said: "Disease is the bullet killing frogs, but climate change is pulling the trigger."
The press had a field day, as it seemed to show global warming was causing damage now. Indeed the beautiful and now extinct Golden toad was christened the first victim of climate change.
Dr Pounds' team claim global warming is producing ideal conditions for a fungus to thrive which causes the disease, which then kills off the frogs. Critics say there's a problem with this theory. The fungus doesn't need high temperatures to wipe out frogs. It is killing frogs in different areas with different climates.
When I contacted Dr Pounds to discuss his research, he admitted they did not know how the fungus was affected by climate but was confident they had shown as statistical relationship.
"We wouldn't have proposed the hypothesis that we did had we not found such a strong relationship; we are not saying that's the only possible mechanism," he said.
We have spoken to many frog specialists who are sceptical of Dr Pounds' paper. Normally it wouldn't really matter which frog expert was wrong.
But there is another group who are involved - climate change sceptics in the United States. They are already criticising Dr Pounds' research to show you can't trust climate scientists or the journals they write in.
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Dr Cindy Carey, a frog specialist from Colorado University, warns that climate scientists have to be more sceptical of their own research.
"A bad paper that gets a lot of publicity could backfire considerably and they'll say see scientists are trying to convince people of climate change on the back of bad data."
All of the climate scientists we spoke to fervently believe global warming is being caused by human activity. Many agree there's also a major problem with alarmism. As one scientist said: "If we cry wolf too loudly or too often, no-one will believe us when the beast actually comes for dinner."
Overselling Climate Change was broadcast on BBC Radio 4 on Thursday 20 April at 2000 BST. Or you can use the Listen Again service on the Radio 4 website, linked on right of this page.