An eco-alarmist fantasy? Unfortunately not - having spent the past three years combing the scientific literature for clues to how life will change as the planet heats up, I know that life on a 6C-warmer globe would be almost unimaginably hellish. A clue to just how unpleasant things can get is contained within a narrow layer of strata recently exposed at a rock quarry in China, dating from the end of the Permian period, 251 million years ago. For reasons that are still not properly understood, temperatures rose by 6C over just a few thousand years, dramatically changing the climate and wiping out up to 95 per cent of species alive at the time. The end-Permian mass extinction was the worst ever: the closest that this planet has ever come to becoming just another lifeless rock orbiting the sun. Only one large land animal survived the bottleneck: the pig-like Lystrosaurus, which for millions of years after the disaster had the globe pretty much to itself.
Clues as to how the world looks in a long-term extreme greenhouse state also come from the Cretaceous period, 144 to 65 million years ago, when there was no ice on either pole and much of Europe and North America was flooded by the higher seas. Tropical crocodiles swam in the Canadian high Arctic, whilst breadfruit trees grew in Greenland. The oceans were incredibly hot: in the tropical Atlantic they may have reached 42C, whilst at the North Pole itself, the oceans were as warm as the Mediterranean is today. The tropics and sub-tropics were so hot that no forests grew, and desert belts probably extended into the heart of modern-day Europe.
Why does he base this scenario on six degrees?
In the latest report from the IPCC, if greenhouse gas emissions continue unchecked till the end of the century, global warming will raise the average temperature of the planet an additional 6.4 degrees C. It doesn't sound like much until you take a sober look back in time at past temperature indicators.
Related tags: global warming