Opinion US government funded scientists have measured the speed of glaciers in Greenland as they move down to the sea over the past ten years, and discovered that - while the glaciers have speeded up somewhat - there's no indication that this will mean major sea level rises.
"Observed acceleration indicates that sea level rise from Greenland may fall well below proposed upper bounds," write the boffins, who are based in Seattle and Ohio.
There's a lot of interest in Greenland's glaciers, as opposed to the rest of the Arctic ice cap, as they rest on solid land and thus - if they should all slide off - sea levels would rise seriously around the globe. Just a few years ago, Greenpeace was bandying a wild figure of seven metres about, adding:
That's bye-bye most of Bangladesh, Netherlands, Florida and would make London the new Atlantis.
In the real world, scientists had thought that - if the glaciers accelerated faster and faster as some models predicted - melting Greenland ice might cause 19 inches of sea-level rise by the year 2100. Other scenarios pointed to a lower figure, of four inches. Combined with melting from the Antarctic and mountain glaciers around the world - though many of these latter don't appear to be melting at all, according to recent research - this could still mean greater rises than the normal 6-7 inches as seen in the 20th century.
Hence the new effort to get a handle on glacier movement in Greenland, the results of which have now been published. The study involved building a decade-long record of the speed at which 200 Greenland glaciers moved towards the sea, using records generated by the Canadian Space Agency's Radarsat-1 satellite, Germany's TerraSar-X satellite and Japan's Advanced Land Observation Satellite.
In short, the study indicates that even the four inch prediction is now looking very much on the high side. We are told:
The scientists saw no clear indication in the new research that the glaciers will stop gaining speed during the rest of the century, and so by 2100 they could reach or exceed the scenario in which they contribute four inches to sea level rise.
However the scientists did add the caveat that something might go wrong in future to change this comparatively reassuring picture.
"There still may be future events – tipping points – that could cause large increases in glacier speed," says Professor Ian Howat of Ohio uni, one of the investigating boffins. "Or perhaps some of the big glaciers in the north of Greenland that haven't yet exhibited any changes may begin to speed up, which would greatly increase the rate of sea level rise."
The paper is published in Science. ®