The UN's climate panel has been backed over a key question as to how far global warming will drive up sea levels this century, a study published on Sunday says. The UN experts are right that the oceans are unlikely to rise by an order of metres (many feet) by 2100, as some scientists have feared, it says. But, its authors caution, low-lying countries and delta areas could still face potentially catastrophic flooding if the upper range of the new estimate proves right.
The UN's climate panel has been backed over a key question as to how far global warming will drive up sea levels this century, a study published on Sunday says.
The UN experts are right that the oceans are unlikely to rise by an order of metres (many feet) by 2100, as some scientists have feared, it says.
But, its authors caution, low-lying countries and delta areas could still face potentially catastrophic flooding if the upper range of the new estimate proves right.
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In a landmark report in 2007, the UN's Intergovernmental Panel on Climate Change (IPCC) predicted oceans would rise by 18-59 centimetres (7.2 and 23.6 inches) by 2100.
The increase would depend on warming, estimated at between 1.1 and 6.4 degrees Celsius (1.98-11.52 degrees Fahrenheit) this century, which in turn depends on how much man-made greenhouse gas is poured into the atmosphere.
It based the calculation on thermal expansion of the seas -- when a liquid is warmed, it grows in volume.
Harder to calculate, the IPCC admitted, was how far meltwater from glaciers and icesheets on land would boost sea levels.
It ventured a provisional calculation, suggesting contributions from those sources could push the upper limit to 76 cms (30.4 inches).
The new paper, led by Mark Siddall of Britain's University of Bristol, used data from fossilised coral and from ice-core measurements to reconstruct sea-level fluctuations over the past 22,000 years, from the height of the last Ice Age to the balmy era of today.
This century, they calculate, the seas will rise by between seven and 82 cms, all sources included, on the basis of a 1.1-6.4 C (1.98-11.52 F) warming -- an estimated increase that is in the same ballpark as the IPCC's.
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