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Warmer soils will add to climate change: expert

David Adam

Global temperatures could go up by 1.5 degrees centigrade.

FAR BIGGER cuts in greenhouse gas emissions could be needed to prevent dangerous climate change than previously thought, a leading scientist warned on Thursday.

Peter Cox, a climate modeller at Exeter University, England, said changes in the soil and oceans over the coming decades could make it much more difficult for the atmosphere to cope with carbon dioxide spewed from cars, power stations, and aircraft.

Professor Cox told the annual meeting of the Royal Geographical Society in London that warmer temperatures could force soils across the world to release their stocks of carbon, potentially driving up global temperatures by an extra 1.5 degrees centigrade.

Prof. Cox said: "This could be very important and would make the [climate change] problem even greater because you have to work harder to stabilise carbon dioxide levels in the atmosphere." Such stabilisation is the goal of international attempts to tackle climate change through cuts in carbon dioxide emissions.

Prof. Cox told the society's conference that about half of mankind's carbon emissions are soaked up by the land and oceans.

However, experts expect this to decline as global temperatures rise, he said. "The natural buffer that currently absorbs our carbon emissions will actually turn against us and accelerate global warming," he said. Scientists call this situation "positive feedback," with warmer temperatures leading to increased carbon emissions.

Models suggest up to 170 billion tonnes of carbon could be released from the land between 2050 and 2100, equivalent to about 30 years of fossil fuel use. This could increase average temperatures by an extra 0.5 to 1.5 degrees centigrade.

But Prof. Cox said the true impact was difficult to predict. A study published last month in the Journal of Climate compared the results of 10 groups from across the world, and while one showed the soil effect could force carbon dioxide levels in the atmosphere up by 200parts per million by 2100, another showed a modest 20ppm increase.

Prof Cox said: "Our climate models grew from weather forecasts and weather forecasters don't care much about carbon dioxide. As we learn more about the important biological and chemical components then the uncertainties are likely to grow and policy makers will just have to accept that." He called for poorer countries to be paid not to cut down forests as a possible solution.

Such "avoided deforestation," he said, could save millions of tonnes of carbon emissions each year, but is currently excluded from international agreements such as the Kyoto protocol.

— © Guardian Newspapers Limited 2006

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