A large number of cities across the world, including the eastern Indian metropolis of Kolkata, are at risk from the threat of rising sea level due to global warming, a major international study has claimed.

According to the study by the Scientific Committee on Antarctic Research, sea levels would rise by twice as much as previously predicted as a result of global warming and by 2100 they would be up to 1.4 metres.

Such a rise in sea levels would engulf island nations such as the Maldives in the Indian Ocean and Tuvalu in the Pacific, devastate coastal cities such as such as Kolkata and Dhaka and force London, New York and Shanghai to spend billions on flood defences, ‘The Times’ reported.

Even if the average global temperature increases by only 2 degree celcius, the target set for next week’s Copenhagen summit, sea levels could still rise by 50 cm, twice that predicted two years ago, the study has calculated.

SCAR, a partnership of 35 of the world’s leading climate research institutions, made the prediction in the report ‘Antarctic Climate Change and Climate’. It far exceeds the 0.59 metre rise by the end of the century quoted by the Intergovernmental Panel on Climate Change (IPCC) in 2007.

SCAR scientists said that the IPCC underestimated grossly how much the melting of the Antarctic and Greenland ice sheets would contribute to total sea-level rises.

In a related interview with the British newspaper, Dr. Rajendra Pachauri, Chairman of the IPCC, said geo-engineering, where carbon is stripped from the atmosphere using specialist technologies, would be necessary to control runaway damage to the climate.

“At some point we will have to cross over and start sucking some of those gases out of the atmosphere,” he said, adding world leaders meeting in Copenhagen should aim for a target of no more than a 1.5 degree celcius rise in global temperatures.

The IPCC report predicted that the melting of ice sheets would contribute about 20 per cent of the total rise in sea levels, with the majority coming from the melting of glaciers and the expansion of the water as it warms. It said that it was not able to predict the impact of melting ice sheets, but suggested this could add 10-20cm.