Every day, it's a-getting closer 12 December 06

Armageddon, that is. Or so it seems. In the first chapter of Six Degrees, due out on 5 March next year, I speculatively state that the Arctic Ocean ice cap will probably now disappear whatever we do to greenhouse gas emissions. The models generally suggest an ice-free Arctic by 2080, but my guess at the time of writing - based on the evidence of very rapid rates of change in the real world (a sixth of the whole ice cap disappeared last summer, for instance) was that this was too conservative.

Well, a new set of model runs, with the NCAR Community Climate System Model, seems to confirm this hunch. Presented at the AGU conference currently, and published in the next issue of Geophysical Research Letters, the study projects near total ice-free conditions across the Arctic Ocean by 2040. Even more startling, perhaps, the model projects that this disappearance of the ice could come in very rapid bursts – with two-thirds of the remaining ice vanishing in the space of a single decade.

What this will do to the radiative balance of the planet I simply don’t know. I have written to Jim Hansen asking about this, so hope to get some wisdom from him – but the big question in my mind is: will the disappearance of the Arctic ice-cap warm the planet sufficiently (by decreasing its albedo, and therefore increasing heat retained from the sun) to trigger other feedbacks such as the enhanced melting of Siberian peat-bogs, releasing more methane and CO2 into the atmosphere, and perhaps sparking ‘runaway’ warming? Any further insight (or reassurance!) on this would be much appreciated.