Scientists are to dig up ice dating back more than 100,000 years in an attempt to shed light on how global warming will change the world over the next century.

The ice, at the bottom of the Greenland ice sheet, was laid down at a time when temperatures were 3C (5.4F) to 5C warmer than they are today.

With temperatures forecast to rise by up to 7C in the next 100 years, the ice more than 8,000ft (2,400m) below the surface is thought by researchers to hold valuable clues to how much of the ice sheet will melt.

Drilling will start in northern Greenland during the summer in an international project involving researchers from 18 countries to extract ice cores covering the Eemian Period.

The Eemian began 130,000 years ago, ending 15,000 years later, and is the most recent time in the Earth's past when temperatures resembled those that can be expected if greenhouse gas emissions are not brought under control.

Carbon dioxide, methane and other chemicals trapped in the ice can provide a detailed picture of the atmosphere and the climate thousands of years ago.

Fragments of organic matter can offer details about animals and plants alive when the ice formed, while particles of dirt can indicate forest fires, tundra fires and volcanic activity.

Analysis of the ice should provide the first measurement of CO2 levels over Greenland during the Eemian and the most detailed analysis yet achieved of climate indicators from the period.

Lars Berg Larsen, of the University of Copenhagen, which is leading the project, said: “We are looking into this period to find out what happens to the climate if you get 3 to 5 degrees warmer.

“The Eemian is the nearest time we know that matches temperatures we can expect in the next 100 or 200 years. It will tell us much about what might happen.”

Four researchers from the British Antarctic Survey (BAS) will be taking part in the operation. They are hopeful of seeing ice not only from the whole Eemian but the years preceding it as well, which could hold clues to what prompted the temperature to start rising, or at least could chart the atmospheric changes that accompanied the rise.

Researchers also hope that the chemical traces hidden in the ice up to 8,340ft below the surface will reveal how the Greenland ice sheet responded to the higher temperatures. This will have implications for sea level rises in the coming century. If the ice sheet melts entirely, seas would be expected to rise by 21ft.

Researchers expect to find that much of the ice persisted even when temperatures were 5C higher than today, offering hope that much of it will remain in a world of manmade climate change.

Robert Mulvaney, of BAS, who has spent 24 years drilling for ice in both the Arctic and Antarctic, said: “Our ideal would be to get not only the whole of the Eemian but the last time that we had a collapse in the Greenland ice sheet.”

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