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Wondering whether weather indicates climate

The latest graph tracking un unprecedented plunge in Arctic sea ice measurements raises once again the question of when you can look at a weather event - a dramatic and unprecedented weather event - and make a relevant and reasonable assumption about what is happening to the climate.

Given the enthusiasm that the denier community brings to challenging assumptions at the contestable edge of science, I’d be wary about saying, unequivally, that this graph shows climate change in action. It’s only part of one year’s data. Admittedly, it’s compared to an average over a much longer time, but it’s still just one year. That’s why you might want to look at the next graph:

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Arctic ice has maxed out for the year and is starting its slow melt into summer in much worse shape than normal, according to the National Snow and Ice Data Centre.

If you look only at the extent of Arctic sea ice, things are not as bad as they have been in recent years. Ice cover is five per cent higher this year than in the record low 2006, even if it is four per cent lower than the 1979 to 2000 average.

But ice thickness is another story, and that seems to be all bad news.

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The return of fall temperatures have ended the annual Arctic melt, leaving the Arctic sea ice cover just shy of a record low, according to the U.S. National Snow and Ice Data Centre.

Expect a flurry of stories in the denier press suggesting that this means global warming has ended.