Friday, 16 October 2009

Bad news for polar bears

Suspicious of those computer models. If the global financial crisis achieves nothing else it should make all of us non-mathematical geniuses at least a little suspicious every time we read of powerful computer models predicting this or that. Much of the mayhem that struck the financial markets was the result of the brilliant modelling that created investments designed to eliminate risk  — some of that wizardry rewarded with Nobel prizes if my memory is correct  — turning out to be wrong.
The occasional doubts I have about the pace and the likely impact of global warming come from that experience. I find more convincing the rather more mundane methods like those employed by Professor Peter Wadhams, from the University of Cambridge. Professor Wadhams has been studying the Arctic ice since the 1960s and who reported this week on the findings of the Catlin Arctic Survey.
This survey was not the result of some computer simulation but good old fashioned measurements by an expedition led by explorer Pen Hadow which drilled holes through the ice during the course of a 435km trek over the ice earlier this year. The team’s measurements found that the ice-floes were on average 1.8m thick — typical of so-called “first year” ice formed during the past winter and most vulnerable to melting. The survey route  — to the north of Canada  — had been expected to cross areas of older “multi-year” ice which is thicker and more resilient.
The BBC reports Professor Wadhams saying:
The Catlin Arctic Survey data supports the new consensus view - based on seasonal variation of ice extent and thickness, changes in temperatures, winds and especially ice composition - that the Arctic will be ice-free in summer within about 20 years, and that much of the decrease will be happening within 10 years.
That means you’ll be able to treat the Arctic as if it were essentially an open sea in the summer and have transport across the Arctic Ocean.
Not exactly cheery news for polar bears but at least slightly better than the last report I came across based not on drilling but on sophisticated computer modelling. Back in December 2007 the BBC was reporting the end of summer Arctic ice by 2013  — just four years from now — with Professor Wieslaw Maslowski of the Naval Postgraduate School, Monterey, California, claiming previous projections had underestimated the processes now driving ice loss.
The number crunching by the Maslowski team, which included co-workers at NASA and the Institute of Oceanology, Polish Academy of Sciences (PAS), incorporated “more realistic” representations of the way warm water is moving into the Arctic basin from the Pacific and Atlantic oceans than other models that variously produced dates for an open summer ocean that, broadly speaking, went out from about 2040 to 2100.
The National Snow and Ice Data Center (NSIDC), which is part of the Cooperative Institute for Research in Environmental Sciences at the University of Colorado at Boulder, reported this month that at the end of the Arctic summer, more ice cover remained this year than during the previous record-setting low years of 2007 and 2008. However, sea ice has not recovered to previous levels. September sea ice extent was the third lowest since the start of satellite records in 1979, and the past five years have seen the five lowest ice extents in the satellite record.

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