I have just finished reading "Six degrees. Our future on a hotter planet" by Mark Lynas (Fourth Estate, 2007), a spine-chiller worthy of Stephen King - except this is non-fiction. Do not let anyone of a nervous disposition read it - but everyone else ought to.
The book goes through, in detail, just what we can expect the atmosphere to do to us as the planet heats up, degree by degree. There are six chapters, one for each degree of warming up to six, plus a seventh chapter on what we can do to stop the warming process before it goes too far. Lynas is not himself a climatologist, but has painstakingly gone through thousands of scientific papers written by people who are, and collated the results. He doesn't have to be as consensus-driven as the IPCC panellists who reported in slightly less chilling terms last week, but there is no sensationalism here, just cold, hard and mostly unpalateable facts.
You begin to get the idea that we are in for a seriously rough ride when by chapter 3 large parts of Africa, Asia and South America have ceased to be able to support anything like the numbers of people who currently live there. The rest of the world isn't going to be in a position to help much either, so it is not hard to imagine that conflicts are going to break out over dwindling resources. One of the hotspots will be the north of the Indian subcontinent, drought-stricken as the vanished Himalayan glaciers no longer feed the major rivers; nuclear-armed Pakistan and India may well square off. The sight of the entire Amazon rainforest literally going up in smoke is hardly reassuring either - especially as that will ensure a further degree and a half rise in global temperature.
That introduces another theme running through the later chapters - the terrifying way in which each degree of temperature rise triggers the next through feedback mechanisms. We already have one of those operating as the arctic icecap melts and ceases to reflect as much sunlight as it used to. That's small beer, though, beside the destruction of the Amazon, the melting of the Siberian permafrost, containing billions of tons of methane - 20 times as powerful a greenhouse gas as carbon dioxide - or the further billions of tons of methane hydrates kept under the sea by cold and pressure, but liable to escape in vast belches as the sea warms. No-one knows how much of that stuff there is down there, or exactly what it will take to release it, but if it comes up we're in big trouble. It's not just that it will give another huge twist to the spiral of global warming - it could explode, too. There is speculation that something like that may have brought the Permian period to an abrupt end, and one scientist has calculated that the bang may have been equivalent to 100,000,000 megatonnes of TNT.
It doesn't look like a good idea to let these feedbacks get too much of a grip, and that probably means keeping the rise down to no more than two degrees above today's temperature. That's quite a challenge for the human race, but it's one at which we cannot afford to fail. Lynas does not go beyond a six degree rise in temperature, probably because there's not much point. By that time the human race, along with most of the rest of Earth's myriad lifeforms, will most likely be extinct.