Rising carbon dioxide levels in the atmosphere caused by burning fuels such as coal and oil may cause enough residual global warming to prevent its onset, said scientists from the University of Southampton in southern England.

The world's oceans are absorbing carbon dioxide from the atmosphere but in doing so they are becoming more acidic, said a team led by Doctor Toby Tyrrell, which conducted research based on marine chemistry.

This, in turn, dissolves the calcium carbonate in the shells produced by surface-dwelling marine organisms, adding even more carbon to the oceans. The outcome is elevated carbon dioxide levels for far longer than previously assumed, the scientists argued.

Carbon dioxide stays in the atmosphere for between five and 200 years before being absorbed by the oceans, reckons the United Nations' Intergovernmental Panel on Climate Change.

However, up to one-tenth of the carbon dioxide currently being emitted will remain in the air for at least 100,000 years, argued Tyrrell.

"Our research shows why atmospheric carbon dioxide will not return to pre-industrial levels after we stop burning fossil fuels," said Tyrrell.

"It shows that it if we use up all known fossil fuels it doesn't matter at what rate we burn them.

"The result would be the same if we burned them at present rates or at more moderate rates; we would still get the same eventual ice-age-prevention result."

Ice ages occur around every 100,000 years as the Earth's orbit round the Sun alters. However, carbon dioxide levels can affect their onset.

Humans have already burned about 300 gigatonnes of carbon of fossil fuels. If 1000 Gt C are burnt then it is likely the next ice age will be skipped. Burning all possible fossil fuels (about 4,000 Gt C) could lead to avoidance of the next five, the study said.

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