'Acidifying oceans' threaten food supply, UK warns

Mr Benn will be speaking during the summit's "oceans day" at a meeting organised by Stanford University and Scripps Institution of Oceanography, both based in California.

"Unlike global warming, which can manifest itself in nuanced, complex ways, the science of ocean acidification is unambiguous," said Andrew Dickson, a Scripps professor of marine chemistry.

"The chemical reactions that take place as increasing amounts of carbon dioxide are introduced to seawater have been established for nearly a century."
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The oceans and atmosphere are constantly exchanging CO2.

Concentrations in the atmosphere are now about 30% higher than in pre-industrial times; a proportion of this is absorbed by seawater, which results in rising concentrations of carbonic acid.

As a result, the pH of seawater has fallen by about 0.1, and a further change of 0.3-0.4 is expected by the end of the century.

This is likely to affect the capacity of organisms including molluscs, coral and plankton to form "hard parts" of calcium carbonate.

A 2007 study showed that rates of coral growth on the Great Barrier Reef had fallen by 14% since 1990.

Mr Benn will say that the Intergovernmental Panel on Climate Change (IPCC) should investigate ocean acidification during its next major assessment of the Earth's climate, scheduled for release in 2013.

Richard.Black-INTERNET@bbc.co.uk

http://news.bbc.co.uk/2/hi/science/nature/8411135.stm