It should have been a chill midwinter day in St Louis as Professor James Zachos laid out his findings last week on how the world could be about to change for ever. But as the expert in earth sciences addressed the American Association for the Advancement of Science (AAAS) on the dangers of climate change, the weather was noticeably warm and muggy.

If Zachos and others are right, it could be about to get a lot warmer — and far more rapidly than people expect.

Humans, he said, are putting earth on a fast-track to catastrophe. They are creating the same conditions that in the past provoked global temperature rises of 5C, destroyed ecosystems, caused widespread extinctions and raised sea levels by 150ft.

“Records of past climate change show that it starts slowly, then the system crosses a kind of threshold and it suddenly accelerates,” said Zachos, a professor at the University of California, Santa Cruz. “Our studies suggest that earth is now on that fast track to global warming.”

Until now many scientists had thought climate change would take centuries to unfold. But Zachos believes that disaster could be a few decades away.

He was backed by Eric Rignot, a Nasa scientist, who described satellite evidence that the Greenland ice cap is melting faster than expected. If the entire ice sheet now covering Greenland were to flow into the oceans, it would raise sea levels by about 21ft.

An even greater reservoir of freshwater is the Antarctic continent — and today Chris Rapley, director of the British Antarctic Survey, will add evidence that the west Antarctic ice sheet is also melting faster than previously thought.

So much water is currently locked up in the Antarctic ice sheet that if it melted it would raise sea levels by a further 150ft or more.

It sounds apocalyptic — almost impossible that such great changes could happen at all, let alone faster than predicted. But scientists are now finding evidence that a dramatic shift in climate has occurred before with extraordinary rapidity.

Today the conference will be presented with a study of a period known as the Pleistocene-Holocene transition, which took place at the end of the ice age about 11,000 years ago. The Pleistocene period witnessed more than 20 cycles of warming and cooling, and the last warming was thought to have taken place over centuries. Some scientists suggest the cycle of changes relates to shifts in the angle of the earth on its axis as it orbits the sun.

Researchers at the Earth and Mineral Sciences Museum at Pennsylvania State University are to announce geological findings that indicate that the final warming happened in the space of just a few decades. Quite why it happened is not yet clear.

But the speed of change, if right, is startling. It caused the extinction of mammoths and many other species, leaving a world that was warmer but much less diverse. Whole habitats suddenly disappeared.

Are we living in a world where the climate could change dramatically, not just in centuries but in a generation or two? Will the children of today find a very different climate in their old age?

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