We are in a fool's climate, accidentally kept cool by smoke, and before this century is over billions of us will die and the few breeding pairs of people that survive will be in the Arctic where the climate remains tolerable." If anybody, but James Lovelock had said that, you would dismiss him as an attention-seeking panic-monger. But it was Lovelock himself.

A couple of centuries from now, Lovelock's reputation as an original and influential thinker in the life sciences may rival Charles Darwin's.
On the other hand, it is possible that nobody will remember either him or Darwin two centuries from now, because there may be no civilisation left. It is already too late to stop drastic global warming, he says, and the catastrophes that follow may sweep it all away.

Lovelock's great scientific insight began with a question: Why are the earth's climate, and even the very composition of the atmosphere itself, so radically different from what they would be on a dead planet? Earth's two neighbours, Venus and Mars, have atmospheres that are almost entirely carbondioxide, whereas the carbondioxide in our own atmosphere is only one-third of one percent. That makes all the difference, because it keeps earth cool.

The earth's early atmosphere was almost all carbondioxide. On a lifeless world, the carbondioxide would gradually have got thicker (it comes from volcanoes and accumulates over time), and the planet would have got hotter and hotter.

But here early life-forms incorporated the carbon from the carbondioxide into their bodies and released the oxygen into the atmosphere as a waste product. New forms then evolved that could use the oxygen to run a far more efficient metabolism and the whole biosphere took off.
Earth teems with life because the temperature is livable and that is so because the atmosphere stays largely free of carbondioxide.

In fact, the average surface temperature on this planet has varied only within a narrow range of 10 degrees C (18 degrees F) over the past three-and-a-half billion years, despite all the ice ages and warming spells that seem to bring such dramatic changes. The sun's heat output has increased by about 20% to 30% during that time, and still the climate hasn't changed. Something is actually keeping it stable.

There is only one plausible candidate: life itself. Lovelock made the intellectual leap in the 1970s and hypothesised that as living things evolved on this planet, they actually shaped their environment through complex chemical feedback loops that maintain the average temperature, the salinity of the oceans and various other key variables at the levels best suited to life.
He was going to call this complex mechanism the "biocybernetic universal system tendency," but a neighbour of his, Nobel Prize-winning novelist William Golding, persuaded him to call it "Gaia".

It was a mistake. New Age romantics embraced the concept, but their enthusiasm actually slowed down scientific acceptance of the concept. Only in the past decade has Lovelock's theory, now renamed "earth system science", been widely accepted among mainstream scientists.

Lovelock has worried aloud about global warning for 30 years, because the living feedback mechanisms that keep the atmospheric carbondioxide down are good at dealing with gradual changes, but unable to cope with the speed at which the level has been rising since the industrial revolution. Indeed, after a certain point these feedback mechanisms will tend to magnify temperature change. "The earth is about to catch a morbid fever that may last as long as 100,000 years," he warns, with temperatures rising 5 degrees C (9 degrees F) worldwide and as much as 8 degrees C (14 degrees F) near the poles by 2100.

We are living in a "fool's climate," Lovelock says, that seems normal only because atmospheric pollution in the northern hemisphere is reflecting much sunlight back into space and keeping global temperatures low. At some point, however, something will cause a major industrial downturn --- a war that doubles the price of oil, a global bird flu pandemic, whatever --- and within weeks the smoke will thin out dramatically. Then we will find out how hot it really is already.

There will be repeated episodes of this sort as the carbondioxide builds up during this century, he predicts, and in the long run civilisation will collapse in most places. Much of the densely populated tropics would become desert and scrub, massive population movements would overwhelm borders, billions would die of hunger and war would take care of most of the rest.

Now Lovelock is saying that it is already too late to avert that outcome: "We will do our best to survive, but sadly I cannot see the United States or the emerging economies of China and India cutting back in time, and they are the main source of emissions. The worst will happen...."

I don't know if Lovelock is right, but I take him very seriously. He is, as he says, a "cheerful sod," and he didn't used to talk like this. It is very worrisome.
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