Ed Pilkington
The Guardian
April 7, 2008
One of the world's leading climate scientists warns today that the EU and its international partners must urgently rethink targets for cutting carbon dioxide in the atmosphere because of fears they have grossly underestimated the scale of the problem.
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Hansen says the EU target of 550 parts per million of C02 - the most stringent in the world - should be slashed to 350ppm. He argues the cut is needed if "humanity wishes to preserve a planet similar to that on which civilisation developed". A final version of the paper Hansen co-authored with eight other climate scientists, is posted today on the Archive website. Instead of using theoretical models to estimate the sensitivity of the climate, his team turned to evidence from the Earth's history, which they say gives a much more accurate picture.
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The fundamental reason for his reassessment was what he calls "slow feedback" mechanisms which are only now becoming fully understood. They amplify the rise in temperature caused by increasing the concentration of greenhouse gases. Ice and snow reflect sunlight but when they melt, they leave exposed ground which absorbs more heat.
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Hansen said that he now regards as "implausible" the view of many climate scientists that the shrinking of the ice sheets would take thousands of years. "If we follow business as usual I can't see how west Antarctica could survive a century. We are talking about a sea-level rise of at least a couple of metres this century."
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http://www.guardian.co.uk/environment/2008/apr/07/climatechange.carbonemissions