Climate Change: On The Edge
Date: Saturday, February 18 2006
Published on Friday, February 17, 2006, by the Independent/UK
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
A satellite study of the Greenland ice cap shows that it is melting far faster than scientists had feared - twice as much ice is going into the sea as it was five years ago. The implications for rising sea levels - and climate change - could be dramatic.
Yet, a few weeks ago, when I - a NASA climate scientist - tried to talk to the media about these issues following a lecture I had given calling for prompt reductions in the emission of greenhouse gases, the NASA public affairs team - staffed by political appointees from the Bush administration - 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 to understand and protect the planet.
This new satellite data is a remarkable advance. We are seeing for the first time the detailed behavior of the ice streams that are draining the Greenland ice sheet. They show that Greenland seems to be losing at least 200 cubic kilometers of ice a year. It is different from even two years ago, when people still said the ice sheet was in balance.
Hundreds of cubic kilometers sounds like a lot of ice. But this is just the beginning. Once a sheet starts to disintegrate, it can reach a tipping point beyond which break-up is explosively rapid. The issue is how close we are getting to that tipping point. The summer of 2005 broke all records for melting in Greenland. So we may be on the edge.
Our understanding of what is going on is very new. Today's forecasts of sea-level rise use climate models of the ice sheets that say they can only disintegrate over a thousand years or more. But we can now see that the models are almost worthless. They treat the ice sheets like a single block of ice that will slowly melt. But what is happening is much more dynamic.