hedgehog

I caught the BBC news last night to be faced with the "fact" that the Greenland ice sheet is melting and we are all doomed. While there may be evidence of this in the BBC newsroom the science is somewhat different indicating that the Greenland ice sheet is increasing in mass, an example of what is going on may be seen here:

http://www.ingentaconnect.com/conten...20001/05140445

Abstract:

The Greenland coastal temperatures have followed the early 20th century global warming trend. Since 1940, however, the Greenland coastal stations data have undergone predominantly a cooling trend. At the summit of the Greenland ice sheet the summer average temperature has decreased at the rate of 2.2 °C per decade since the beginning of the measurements in 1987. This suggests that the Greenland ice sheet and coastal regions are not following the current global warming trend. A considerable and rapid warming over all of coastal Greenland occurred in the 1920s when the average annual surface air temperature rose between 2 and 4 °C in less than ten years (at some stations the increase in winter temperature was as high as 6 °C). This rapid warming, at a time when the change in anthropogenic production of greenhouse gases was well below the current level, suggests a high natural variability in the regional climate. High anticorrelations (r = -0.84 to -0.93) between the NAO (North Atlantic Oscillation) index and Greenland temperature time series suggest a physical connection between these processes. Therefore, the future changes in the NAO and Northern Annular Mode may be of critical consequence to the future temperature forcing of the Greenland ice sheet melt rates.

TonyG

There's no mention of an increase in ice sheet mass in that abstract - only of a temperature drop. Also, if you read the BBC news item again, the loss of ice is not from the ice sheet melting in situ, but of ice being lost from the ends of glaciers due to an increase in the rate at which they move.

hedgehog

Yes indeed, the increase in mass is generally accepted as it is what drives faster moving glaciers hence why I didn't think to post references, however see for example:

http://www.sciencemag.org/cgi/conten...ract/1115356v1

This is, of course, why more ice is being lost at the ends of glaciers, Rignot and Kanagaratnam document that the outflow from Greenland's glaciers has increased to about 220 cubic Km per year for example. If more ice is forming then it is only natural to expect glaciers to move faster and to increase their discharge, just as a river would do if heavy rain falls. If the glaciers weren't moving faster and discharging more ice then we would have a fault with gravity, though it would seem that some didn't get this message from the recent media coverage for some reason.

The Greenland ice cap contains about 9.8% of the worlds ice, the Arctic Ocean contains about 0.01%. The Antarctic ice sheets hold approximately 88% of the worlds ice and they are also increasing in mass.

unclebuck

As far as the BBC is concerned climate change and man made global warming is now presented as fact.

You can even install some dodgy software on your machine and take part in a great 'climate prediction experiment' the outcome of which of course is already beyond doubt.

http://www.bbc.co.uk/sn/hottopics/climatechange/

hedgehog

Actually climate researchers refer to these computer based simulations as "storylines" and that gives some idea of where they are coming from. I think it was Heisenberg (but I'm not certain) who said that if you give him 3 variables he would draw an elephant and if you gave him 4 he would make it wiggle it's trunk. This is very much the case with the climate "storylines" in that what you do is set each model running with a slightly different set of variables and you then pick the result you like from all the outcomes. So when you see a report in the media telling you that computers predict that temperatures will rise by 13 degrees by tomorrow lunchtime what you are actually seeing is one storyline result from perhaps thousands that have actually been run. For all you know every other storyline outcome might have been global cooling but only one gets presented as the "result."

Even the very best of these computer climate models still don't consider clouds for example! When you are ignoring a factor as big as clouds in your attempts to create a storyline to predict climate it can't come as much of a shock when your predictions can produce a range of highly entertaining and improbable outcomes, at least the entertainment value works to benefit the media.