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Climate Target Is Not Radical Enough - Study
By Ed Pilkington
The Guardian UK
Monday 07 April 2008
Nasa scientist warns the world must urgently make
huge CO2 reductions.
New York -
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.
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 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.
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 35m 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 metres. 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 6C, the paper finds. Previous
estimates had suggested warming would be just 3C 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 realise
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 metres this century."
The revised target is likely to prompt criticism that he is setting the bar
unrealistically high. With the US administration still acting as a drag on international
efforts, climate campaigners are struggling even to get a 450ppm target to stick.
Hansen said his findings were not a recipe for despair. The good news, he said,
is that reserves of fossil fuels have been exaggerated, so an alternative source
of energy will have to be rapidly put in place in any case. Other measure could
include a moratorium on coal power stations which would bring the C02 levels
to below 400ppm.
Hansen's revised position will pile yet further pressure on Britain over plans
to build a new generation of coal power stations. Last year he wrote to Gordon
Brown urging him to block the first such power station; the Royal Society has
made similar suggestions to the government.
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