GAGGED NASA SCIENTIST WARNS: ICE CAPS 'MELTING FAST'
Climate change: On the edge
Greenland ice cap breaking up at twice the rate it was five years ago, says scientist Bush tried to gag
By Jim Hansen
Published: 17 February 2006
[div style="display: block;" id="articleColumn1" class="articleColumn1"] A satellite study of the Greenland ice cap shows that it is melting farfaster than scientists had feared - twice as much ice is going into thesea as it was five years ago. The implications for rising sea levels -and climate change - could be dramatic. [/p] Yet, a few weeks ago, when I - a Nasa climate scientist - tried to talkto the media about these issues following a lecture I had given callingfor prompt reductions in the emission of greenhouse gases, the Nasapublic affairs team - staffed by political appointees from the Bushadministration - tried to stop me doing so. I was not happy with that,and I ignored the restrictions. The first line of Nasa's mission is tounderstand and protect the planet.[/p]This new satellite data is a remarkable advance. We are seeing forthe first time the detailed behaviour of the ice streams that aredraining the Greenland ice sheet. They show that Greenland seems to belosing at least 200 cubic kilometres of ice a year. It is differentfrom even two years ago, when people still said the ice sheet was inbalance.[/p]Hundreds of cubic kilometres sounds like a lot of ice. But this isjust the beginning. Once a sheet starts to disintegrate, it can reach atipping point beyond which break-up is explosively rapid. The issue ishow close we are getting to that tipping point. The summer of 2005broke all records for melting in Greenland. So we may be on the edge.[/p]Our understanding of what is going on is very new. Today's forecastsof sea-level rise use climate models of the ice sheets that say theycan only disintegrate over a thousand years or more. But we can now seethat the models are almost worthless. They treat the ice sheets like asingle block of ice that will slowly melt. But what is happening ismuch more dynamic.[/p]Once the ice starts to melt at the surface, it forms lakes thatempty down crevasses to the bottom of the ice. You get rivers of waterunderneath the ice. And the ice slides towards the ocean.[/p]Our Nasa scientists have measured this in Greenland. And once theseice streams start moving, their influence stretches right to theinterior of the ice sheet. Building an ice sheet takes a long time,because it is limited by snowfall. But destroying it can be explosivelyrapid.[/p][/div][div style="display: block;" class="articleColumn2" id="articleColumn2"]How fast can this go? Right now, I think our best measure is whathappened in the past. We know that, for instance, 14,000 years ago sealevels rose by 20m in 400 years - that is five metres in a century.This was towards the end of the last ice age, so there was more icearound. But, on the other hand, temperatures were not warming as fastas today.[/p]How far can it go? The last time the world was three degrees warmerthan today - which is what we expect later this century - sea levelswere 25m higher. So that is what we can look forward to if we don't actsoon. None of the current climate and ice models predict this. But Iprefer the evidence from the Earth's history and my own eyes. I thinksea-level rise is going to be the big issue soon, more even thanwarming itself.[/p]It's hard to say what the world will be like if this happens. Itwould be another planet. You could imagine great armadas of icebergsbreaking off Greenland and melting as they float south. And, of course,huge areas being flooded.[/p]How long have we got? We have to stabilise emissions of carbondioxide within a decade, or temperatures will warm by more than onedegree. That will be warmer than it has been for half a million years,and many things could become unstoppable. If we are to stop that, wecannot wait for new technologies like capturing emissions from burningcoal. We have to act with what we have. This decade, that meansfocusing on energy efficiency and renewable sources of energy that donot burn carbon. We don't have much time left.[/p]Jim Hansen, the director of the Nasa Goddard Institute for SpaceStudies in New York, is President George Bush's top climate modeller.He was speaking to Fred Pearce[/p]
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