When a wake-up call bids goodnight

Another Life: Some of the earliest words I read were not exactly encouraging. "The End of the World Is Nigh!", "Prepare To Meet Thy Doom!" - placards borne up and down the seafront by old men with far-off eyes.

Perhaps they parade still, Christian martyrs to indifference. Up near the station, in the Lord's Day Observance Society window, a huge pictorial engraving warned me what to expect: the sky rent with lightning, the Earth unleashing floods and volcanoes (one or the other; perhaps both).

This may have had unintended effects: the young agnostic marching against The Bomb, the full-fledged unbeliever buying into Gaia and science rather than mythology and God. And now here's Professor James Lovelock, Gaia's begetter, my guru and hero for almost 30 years, promising apocalypse - if not now, then far too soon. "I'm usually a cheerful sod, so I'm not happy about writing doom books," he says. "But I don't see any easy way out." Hence, at 86, his final notice, The Revenge of Gaia, to be published by Penguin next week.

It is no surprise to most of us that global warming can't be turned off overnight or even in 10 or 20 years' time. Given the inertia of human, political and corporate response, it's like trying to throw a speeding supertanker into reverse. But the inevitabilities Lovelock spells out are dire stuff indeed. "As the century progresses," he wrote in the London Independent last week, "the temperature will rise 8 degrees in temperate regions and 5 degrees in the tropics. Much of the tropical land mass will become scrub and desert, and will no longer serve for regulation; this adds to the 40 per cent of the Earth's surface we have depleted to feed ourselves.

"Curiously," he went on, "aerosol pollution of the northern hemisphere reduces global warming by reflecting sunlight back to space. This 'global dimming' is transient and could disappear in a few days like the smoke that it is, leaving us fully exposed to the heat of the global greenhouse. 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." Lovelock, now a celebrated environmental scientist, is used to being rubbished. His first book, in 1979, Gaia, A New Look at Life on Earth proposed the hypothesis that the whole earth is a living organism, regulating its well-being by intricate control and feedback mechanisms. As a "hypothesis" it couldn't be proved and met with wide scientific scepticism. To me and a few million other greens, it made powerfully intuitive sense, not least as metaphor for a right and respectful human relationship with nature. Much of science, too, has come round to the idea that Earth has an elaborate and holistic feedback physiology that our species has disrupted and abused.

At the moment, Lovelock argues, Gaia's system is amplifying change, so that any one of a number of "tipping points" will - it used to be could - plunge civilisation into chaos, and most wildlife into extinction. An all-too-ready example is the melting of Arctic ice, leaving a huge dark ocean to soak up solar radiation even faster. He has grown increasingly desperate in considering a "powered descent" of civilisation, outraging many of his green followers by urging a return to nuclear energy. His new book, he says, is intended as a "wake-up call" (though much of it will read more like "Goodnight").

Coincidence brings news of one contingency plan for doomsday that chimes a little oddly with Lovelock's Arctic scenario. The Norwegian government is going to dig an artificial cave, deep inside a frozen mountain on the Arctic island of Svalbard (Spitzbergen), in which to hold about 3 million packages, each containing hundreds of seeds from the world's crop varieties. The cave will have ventilation equipment to keep the cave at minus 10-20 degrees, along with blast-proof doors.

There has been increasing anxiety among crop scientists about the insecurity of many of the world's 1,500 seed banks, given the wide range of possible disasters. Those of both Iraq and Afghanistan were destroyed in the recent wars and many others are at potential risk of simple loss of electricity that keeps the seeds refrigerated and viable.

The Svalbard cave is meant to stay secure "forever", its packages updated by the Global Crop Diversity Trust, working with UN approval. Even if the ventilation equipment failed, its secretary insists, it would be months before the temperature inside rose even to the minus 3.5 degrees of permafrost. And, of course, he'll have left the address with somebody, in case we need to start again.