It's not our fault. Don't blame us for climate change - blame it on the sun and the stars in the sky. That's the radical conclusion of a new glossy paperback, by the controversial climate physicist Henrik Svensmark.

As conspiracy theory books go, The Chilling Stars may not be a page-turner in the style of Michael Crichton's State of Fear, but it has considerably more scientific rigour (albeit that Crichton's book was about as scientific as the Da Vinci Code), and is certainly persuasive enough to earn Svensmark an invite to the White House, to whisper words of encouragement in Dubya's ear.

For 10 years, Svensmark has protested that man-made carbon dioxide is not the gas which is suffocating the planet. Instead, he claims, there are greater forces at work: cosmic rays - streams of high-energy particles from exploded stars.

His theory goes something like this: cosmic rays bombard the earth's atmosphere, helping to seed the formation of clouds. Clouds reflect sunlight and keep the earth cool. So, what would happen if the levels of cosmic rays subsided due to interference from the sun?

The earth would warm.

This is exactly the hypothesis which Svensmark set out in 1996. There was just one major problem - there was no evidence that cosmic rays promote cloud formation, thus blowing a hole bigger than the ozone layer in Svensmark's theory.

But last year, after a decade of digging for data (or "fighting a heroic battle against the doom merchants" if you're a fan of Crichton), Svensmark finally struck oil. In a box of air in the basement of the Danish National Space Centre, he carried out an experiment showing that when cosmic rays hit the atmosphere, electrically-charged particles are formed. "These particles attract water molecules from the air and cause them to clump together until they condense into clouds," says Svensmark. His findings were published in a prestigious journal, Proceedings of the Royal Society.

After discovering the missing piece in his puzzle, Svensmark wasted no time in publishing a book, The Chilling Stars, outlining the finer details of his theory of global warming. He claims that the number of cosmic rays hitting Earth is falling due to higher magnetic activity around the sun.

"Evidence from ice cores show this happening long into the past," says Svensmark. "We have the highest solar activity we have had in at least 1000 years."

Due to this unfortunate cosmic anomaly, there are fewer clouds to protect us from the sun's baking heat. It all points to one very controversial conclusion - mankind is not to blame for climate change.

This flies in the face of a very powerful report by the world's most distinguished climate change experts - the IPCC - who concluded that the likelihood of man being to blame for global warming is "greater than 90%".

Svensmark is not impressed. "By not including the cosmic ray effect in climate models, it means the results are inaccurate. Humans are having an effect on climate change, but the size of man's impact may be much smaller, so the man-made change is happening slower than predicted." As a result, "the most alarming forecasts of global warming are likely to turn out to be exaggerated."

Well, isn't that a comforting thought? Warming, even. But according to the world's leading climate scientists, The Chilling Stars is no more than a bedtime story.

"You cannot explain the rise in global temperatures if you don't change the concentrations of greenhouse gases," says Professor Phil Jones, Director of the Climate Change Unit at East Anglia University and a member of the IPCC. "In fact, without man-made carbon dioxide, the world should be cooling."

Last year, a computer model by Peter Stott at the Met Office's Hadley Centre for Climate Change found that warming over the past 50 years could only be explained by climbing emissions of greenhouse gases.

Stott said that Svensmark's theories should be taken "with a cellar of salt".

Jones agrees: "There's no disputing that cosmic ray activity varies and is influenced by the solar cycle. But there's no real evidence that cosmic rays affect clouds." He also dismisses the historical cloud cover data that Svensmark uses to back up his theory as "very selective".

But Svensmark, unlike his book, will not be put down so easily. Later this year, he and a team of more than 60 scientists from around the world will attempt to replicate the effect of cosmic rays hitting the atmosphere, by conducting a large-scale experiment using a particle accelerator in Geneva.

They hope this will prove whether this deep space radiation is responsible for changing cloud cover. If it is, would this force the IPCC to re-evaluate their ideas about how global warming occurs?

Not according to Phil Jones: "That's only an experiment in the lab, albeit a very big lab. It's still not enough to prove that his theory is happening in the real world."

"Remember - if you write a book, you've only got to persuade the publisher that it's a good read."

  • The Chilling Stars - A New Theory of Climate Change is published on February 22 by Icon Books, priced £9.99.