Researchers at the University of Birmingham found that 630 million years ago the earth had a warm atmosphere full of carbon dioxide but was completely covered with ice.

The scientists studied limestone rocks and found evidence that large amounts of greenhouse gas coincided with a prolonged period of freezing temperatures.

Such glaciation could happen again if global warming is not curbed, the university's school of geography, earth and environmental sciences warned.

While pollution in the air is thought to trap the sun's heat in the atmosphere, causing the planet to heat up, this new research suggests it could also have the opposite effect reflecting rays back into space.

This effect would be magnified by other forms of pollution in the earth's atmosphere such as particles of sulphate pumped into the air through industrial pollution or volcanic activity and could create ice age conditions once more, the scientists said.

Dr Ian Fairchild, lead investigator, said: "We came up with an independent test of a theory that the earth, like a baked Alaska pudding, was once hot on the outside, surrounding a cold, icy surface.

"It happened naturally in the past, but the wrong use of technology could make it happen again."

The limestones studied were collected in Svalbard in the Arctic Ocean, which is covered in ice and snow.

by:telegraph