Human history, even in the nuclear age, offers nothing to compare with the physical history of the planet in the theatre of the apocalypse. Two hundred and fifty million years ago a giant meteor wiped out 90 per cent of life on Earth. One hundred and eighty-five million years later another space rock is thought to have killed off the dinosaurs. Firmly in the geological present, a single flood, moving at 65 miles per hour with 60 times the force of the Amazon, smashed through the Cascade Mountains to create the Columbia River Gorge in Oregon. And now, in a steady southward sequence, far faster than scientists forecast just 15 years ago, the ice shelves of Antarctica are collapsing.

The disintegration of a large section of the Wilkins ice shelf on the Antarctic Peninsula does not in itself presage major global sea level rises, still less the end of life as we know it. But there is no longer any reasonable doubt that climate change is the cause; that it would take centuries of lower temperatures for these ice shelves to re-form; and that if they do not, the great ice sheets of the Antarctic interior will be the next to melt.

What is happening on the southwestern edge of the Wilkins ice shelf is easily misunderstood. From the stunned commentary of observers who have flown over the area it would be easy to infer that the entire shelf had collapsed. In fact the area reduced to giant icebergs since the first big rupture on February 28 amounts to about 4 per cent of the total. More than 5,000 square miles of ice remains intact. But the break-up has nonetheless been electrifyingly fast and on a massive scale. The alarm it has caused at the British Antarctic Survey and the US National Snow and Ice Data Centre is anything but forced.

This is the eighth Antarctic ice shelf collapse in the past 30 years. All have occurred on the Antarctic Peninsula, which reaches 1,000 miles into the Southern Ocean towards Cape Horn and is far more exposed to warming ocean and air temperatures than is Antarctica's continental interior. The peninsula's mean temperature has, in fact, been rising faster than anywhere on Earth over the past half-century, at half a degree celsius per decade, while there is evidence that mean temperature at the South Pole is actually falling. But the Wilkins shelf is the most southerly to succumb to climate change so far. The damage that it has sustained in the past month will slow during the Antarctic winter but can only accelerate next year. As it shrinks, so will its effectiveness as a buffer between the ocean and the interior. Most troubling of all, the suddenness of the loss of an area the size of the Isle of Man has caused scientists to revise their estimate of the remaining lifespan of the shelf as a whole, from thirty years to ten.

Rajendra Pachauri, the chairman of the UN Intergovernmental Panel on Climate Change, has seized on the Wilkins event to give warning of “irreversible and abrupt changes” including cataclysmic sea level rises. In reality it takes melting ice sheets, not shelves, to raise sea levels significantly. But the evidence from the Antarctic Peninsula hardly justifies complacency. The processes at work there are global. Slowing them is daunting, but the price of not trying will be higher than the most stringent carbon emissions. Britain's brave new enthusiasm for nuclear power is therefore timely, but it must be part of a wholesale switch away from carbon-based energy. Without such a switch, the Wilkins ice shelf will be the least of the casualties.