A new book offers the theory that earth's hot-cold swings are natural and not caused by any greenhouse effect, writes Claire O'Connell.
It's official: we are to blame for the current blip of global warming. Or are we? Last month media reports told the world that the Intergovernmental Panel on Climate Change (IPCC) was 90 per cent sure that man-made greenhouse gases account for most of current global warming.
But an alternative and controversial theory suggests that climate events on earth, including our current warm period, are down to the interplay of more natural phenomena: cloud formation, the sun's magnetic field and a barrage of cosmic rays that bombard our solar system.
Commentators, including George Monbiot in the Guardian, and climate scientists have questioned the validity of the data behind the argument, which flies in the face of conventional thinking that greenhouse gases (such as carbon dioxide) generated by man's activities help to insulate the earth's atmosphere and promote an increase in global temperature.
However, the proponents of naturally orchestrated climate change believe that we should remain open to considering the alternatives to the human-centred argument.
"The most exasperating thing for me is to hear politicians and journalists and, amazingly, some scientists saying that the science is settled," says British science writer Nigel Calder, co-author of The Chilling Stars: A New Theory of Climate Change.
"The IPCC being 90 per cent sure means that there is a wide open breach in the defences for any young scientist with a better idea to come in," says Calder. "Now 99 out of 100 mavericks are wrong, but on the other hand, nearly all the progress in science depends on that 1 per cent of mavericks who are right."
For more than a decade, his Danish co-author, climate physicist Dr Henrik Svensmark, has been investigating the theory that cosmic rays emitted by distant exploding stars could seed low-lying clouds over the earth that reflect the sun's warmth back into space.
"This is the usual terribly boring carpet of cloud that you see out of your window on a transatlantic flight," explains Calder. "It's not a completely simple story, but in round numbers there's no question that these low-level clouds have a huge cooling effect on the earth."
Scientists know remarkably little about how these vast banks of cloud arise, explains Calder, but it appears to involve tiny specks in the atmosphere on which water vapour can condense to form droplets. Svensmark and his colleagues claim to have found a link between cloud cover and cosmic ray exposure, so he devised a simple experiment to see whether cosmic rays could be involved in seeding clouds: he put a box of air in the basement of the Danish National Space Center and looked at what happened when cosmic rays naturally passed through the chamber.
"As the cosmic rays whizzed through the box they knocked electrons out of atoms and these electrons then help to stick together the very small specks, the building blocks of the specks on which the water droplets would eventually condense," explains Calder.
The theory continues that if cosmic rays are seeding the cooling clouds, then variations in the amounts of incoming cosmic rays could affect global temperature. And this is where the sun comes in.
"There's no shutting out cosmic rays, but the sun does its best to bat quite a lot of them away with its magnetic field," according to Calder. "Essentially the cosmic rays bounce off the magnetic field and to that extent we are screened from them."
But there are periods when our celestial bouncer is less than enthusiastic about checking the guest list, potentially allowing more cosmic rays to penetrate the earth's atmosphere and seed cooling clouds.
"The sun is a manic depressive," says Calder. "Three hundred years ago it was depressive, and people commented on the absence of sunspots, the Maunder Minimum. That coincided with the Little Ice Age where in London they were having frost fairs on the frozen Thames."
More recently, the sun has been in a manic phase, he adds. "The sun has got more vigorous, especially since the beginning of the 20th century, which is the global warming period that people have got excited about."
ANOTHER PLANK INthe cooling clouds theory is the Antarctic anomaly, which Calder refers to as an acid test. "It's one of the best kept secrets in the business that East Antarctica is getting cooler; the sea ice has grown by 8 per cent since 1978," he says. "This makes no sense in the greenhouse story. You can produce reasons why Antarctica might not warm up as fast as the Arctic but you can't write the formula in their theory which explains why it's actually getting cooler."
Instead Svensmark's theory proposes that under a cloudless sky the dazzlingly white snow of Antarctica will reflect more sunlight back into space than it will if there's cloud overhead. "And so, glory be, any reduction of cloud cover such as we have had, will tend to make Antarctica cooler," says Calder.
THE COSMIC RAYtheory also holds up through history, he says. As the sun and earth have moved through the terrain of the Milky Way over millions of years, catastrophic changes in the earth's climate appear to link in with bombardment or protection from cosmic rays.
In particular, episodes of severe cold, where glaciers and icebergs stalked the equator, correspond with times of star "baby booms" nearby. "If you get a high birth rate of stars you get a lot of these exploding stars and they'll be popping off and drenching the poor old earth with cosmic rays and it just fits," says Calder.
Svensmark has struggled in the political and scientific cold for 11 years to have his theory taken seriously, but now projects on atomic particles and cloud seeding are being planned at CERN in Geneva.
And if it holds water, what does the cooling clouds theory mean for us today? Calder notes that our knowledge of cosmic rays is still too scant to make predictions, but he argues that the current greenhouse-based predictions of a three to four degree rise in temperature this century could be overly dire.
Calder believes that whatever lies behind climate change, it still makes geo-political and environmental sense to conserve the world's finite fuel resources. "People go to war over energy supplies and motor cars spew out all sorts of nasty stuff, of which carbon dioxide is the least harmful," he says.
And, far from advertising the cosmic ray theory as correct, Calder would prefer to see open debate in the scientific tradition. "The science is never settled. Let other people come along and pick holes in it," he says.
"There has always been a tendency to say that anyone who does not go along with the story about man-made global warming is some kind of nutcase or is in the pay of the oil companies. But to me it is still flabbergasting that the ordinary clouds that you see out of your window take their orders from the sun and the stars. It's beautiful. And if it wasn't so shockingly political, everybody would be lapping it up."
The Chilling Stars: A New Theory on Climate Change , by Henrik Svensmark and Nigel Calder, is published by Icon Books.