Wednesday 11 March 2009

Sea could rise 1m by 2100, say scientists

CLIMATE CHANGE: SEA LEVELS are set to rise twice as much as previously expected – by as much as a metre or more before the end of this century, mainly due to accelerated melting of the polar ice caps, according to new scientific research.

Presented at a major international conference hosted by the University of Copenhagen, the projections are well higher than the 18cm-59cm rise envisaged by the Intergovernmental Panel on Climate Change (IPCC) in 2007.

Research in the past two years shows the loss of ice in Greenland has been accelerating over the past decade. According to Dr Konrad Steffen, Greenland is losing up to 300sq km of ice a year – equivalent to two-thirds of all the glaciers in the Alps.

Dr Steffen, who heads the University of Colorado’s environmental science institute, said a 30 per cent increase in the area that melts along the Danish protectorate’s west coast has been observed since 1979. He attributed this to an average increase of 1.4 degrees Celsius in the summer months and a 3.5-degree rise in temperature during the spring.

“Climate change is enhancing warming in the Arctic region,” he told a press briefing yesterday. As a result, the ice is “melting much faster” and this, in turn, is contributing to a rise in sea levels.

“The upper range of sea level rise by 2100 might be above one metre or more on a global average, with large regional differences depending where the source of ice loss occurs,” he said.

The new research suggests it is increasingly unlikely that the rise in sea level will be much less than 50cm by 2100. Even this relatively optimistic projection – especially combined with surges – would hit low-lying coastal communities worldwide, including in Ireland.

Dr Eric Rignot, professor of earth system science at the University of California and senior research scientist at NASA’s Jet Propulsion Laboratory, said the reason the IPCC’s 2007 projections were lower was due to “a lot of uncertainty” then about polar ice sheets. “The numerical models used at the time did not have a complete representation of outlet glaciers and their interactions with the ocean. The results gathered in the last two to three years show that these are fundamental aspects that cannot be overlooked,” he said.

Dr John Church, of Australia’s Centre for Climate Research, said “unless we undertake urgent and significant mitigation actions , the climate could cross a threshold during the 21st century committing the world to a sea level rise of metres”. The impacts, he predicted, would be severe.

Approximately 10 per cent of the world’s population – 600 million people – live in low-lying coastal areas, and major flooding that used to happen only once in a hundred years “will be happening several times a year”, he warned.

Dr Jason Lowe, head of the British Met Office’s sea level projection group, said a one-metre increase would be serious enough, but the effects would be devastating if accompanied by storm surges such as the 4.5m surge on the Thames in 1953.

Although such a surge accompanied by a high tide had a “low probability”, it could not be ruled out. Neither could more pessimistic projections that the rise in sea levels by 2010 could be as high as two metres, rather than just one. This has obvious implications for plans to replace the Thames Barrier with a new flood control system to protect London.

A recent study of Dublin Bay that looked at how the city could be protected from rising sea levels proposed a system of “booms” to guard against storm surges.

Irish Times

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