George Bush is behaving like a furious defaulter whose home is about to be repossessed.

Smashing the porcelain, ripping the doors off their hinges, he is determined that there will be nothing worth owning by the time the bastards kick him out. His midnight regulations, opening America's wilderness to logging and mining, trashing pollution controls, tearing up conservation laws, will do almost as much damage in the last 60 days of his presidency as he achieved in the foregoing 3,000. His backers - among them the nastiest pollutocrats in America - are calling in their favours. But this last binge of vandalism is also the Bush presidency reduced to its essentials.

Destruction is not an accidental product of its ideology. Destruction is the ideology. Neoconservatism is power expressed by showing that you can reduce any part of the world to rubble. If it is too late to prevent runaway climate change, the Bush team must carry much of the blame. His wilful trashing of the Middle Climate - the interlude of benign temperatures which allowed human civilisation to flourish - makes the mass murder he engineered in Iraq only the second of his crimes against humanity.

Bush has waged his war on science with the same obtuse determination with which he has waged his war on terror. Is it too late? To say so is to make it true. To suggest there is nothing that can be done is to ensure that nothing is done. But even a resolute optimist like me finds hope ever harder to summon.

A new summary of the science published since last year's Intergovernmental Panel report suggests that - almost a century ahead of schedule - the critical climate processes might have begun. Just a year ago the Intergovernmental Panel warned that the Arctic's "late-summer sea ice is projected to disappear almost completely towards the end of the 21st century ... in some models." But, as the new report by the Public Interest Research Centre (Pirc) shows, climate scientists are now predicting the end of late-summer sea ice within three to seven years. The trajectory of current melting plummets through the graphs like a meteorite falling to earth. Forget the sodding polar bears: this is about all of us. As the ice disappears, the region becomes darker, which means that it absorbs more heat.

A recent paper published in Geophysical Research Letters shows that the extra warming caused by disappearing sea ice penetrates 1,000 miles inland, covering almost the entire region of continuous permafrost. Arctic permafrost contains twice as much carbon as the entire global atmosphere. It remains safe for as long as the ground stays frozen. But the melting has begun. Methane gushers are now gassing out of some places with such force that they keep the water open in Arctic lakes through the winter.

The effects of melting permafrost are not incorporated in any global climate models. Runaway warming in the Arctic alone could flip the entire planet into a new climatic state. The Middle Climate could collapse faster and sooner than the grimmest forecasts proposed. Barack Obama's speech to the US climate summit last week was an astonishing development. It shows that, in this respect at least, there really is a prospect of profound political change in America. But while he described a workable plan for dealing with the problem perceived by the Earth Summit of 1992, the measures he proposes are hopelessly out of date. The science has moved on.

The events the Earth Summit and the Kyoto process were supposed to have prevented are already beginning. Thanks to the wrecking tactics of Bush the elder, Clinton (and Gore) and Bush the younger, steady, sensible programmes of the kind that Obama proposes are now irrelevant. As the Pirc report suggests, the years of sabotage and procrastination have left us with only one remaining shot: a crash programme of total energy replacement.