NASA chief: Climate target is not radical enough

One of the world's leading climate scientists warned on Apr. 7 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. In a startling reappraisal of the threat, James Hansen, head of the NASA Goddard Institute for Space Studies in New York, calls for a sharp reduction in C02 limits. 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 civilization developed." 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. The team studied core samples taken from the bottom of the ocean, which allow C02 levels to be tracked millions of years ago. They show that when the world began to glaciate at the start of the Ice age about 35 million years ago, the concentration of CO2 in the atmosphere stood at about 450ppm. "If you leave us at 450ppm for long enough it will probably melt all the ice -- that's a sea rise of 75 meters. What we have found is that the target we have all been aiming for is a disaster -- a guaranteed disaster," Hansen told the Guardian. At levels as high as 550ppm, the world would warm by 6ºC, the paper finds. Previous estimates had suggested warming would be just 3ºC at that point. Hansen has long been a prominent figure in climate change science. He was one of the first to bring the crisis to the world's attention in testimony to Congress in the 1980s. But his relationship with the Bush administration has been frosty. In 2005 he accused the White House and NASA of trying to censor him. He has steadily revised his analysis of the scale of the global warming and was himself one of the architects of a 450ppm target. But he told the Guardian: "I realize that was too high." 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. As ice sheets recede, the warming effect is compounded. Satellite technology available over the past three years has shown that the ice sheets are melting much faster than expected, with Greenland and west Antarctica both losing mass. 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 meters this century."