The melting of the icecaps is one part of this story and it’s a big part. The second part of rising sea level is that as the planet warms, oceans warm and warmer water expands slightly. It’s hard to imagine that slightly expanded water could raise sea level, but this is largely an ocean planet, so this slight expansion makes this more of an ocean planet.

The largest amount of sea level rise will be expected from glacial melt, especially melting of the Greenland and Antarctic caps. There is growing evidence that the melting of these critical ice caps is accelerating.

It is likely that there are tipping points in this melting process. One of these tipping points is that the melting water seeps down through the glacier, lubricates and speeds up the glacial flow in to the ocean. The sudden break-up of ice shelves is already documented.

This catastrophic sea level rise will likely happen faster than all predictions because the scientists are conservative in their predictions. This is not a political conservative-ism, it is scientific conservatism. Risk-takers in science, people willing to model aggressively will be wrong on occasion and that single aggressive error will end their scientific career. Most scientists get that.

NASA’s James Hansen is the voice of concerned climate scientists today. If President Obama really wants to deal with global warming, he can always appoint James Hansen to an important post in the administration and give his recommendations a lot of weight.

[1] clipped from [2] www.economist.com A sinking feeling Mar 11th 2009 From The Economist print edition Sea levels are rising twice as fast as had been thought SCIENCE and politics are inextricably linked. At a scientific conference on climate change held this week in Copenhagen, four environmental experts announced that sea levels appear to be rising almost twice as rapidly as had been forecast by the United Nations just two years ago. The warning is aimed at politicians who will meet in the same city in December to discuss the same subject and, perhaps, to thrash out an international agreement to counter it. Konrad Steffen of the University of Colorado, Boulder, leads one study of the Greenland ice sheet. He told the conference that this sheet is melting not only because it is warmer but also because water seeping through its crevices is breaking it up. This effect had been neglected in the earlier report. [3]