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Washout 2012 summer, melty Greenland 'nothing to do with Arctic ice or warm oceans'

Could have been 'natural variability'

Girl in rain

Last summer was a washout for us Brits, and indeed top meteorologists are meeting at the moment to find out just why. Some other odd things happened last year, too: exceptionally large areas of the Greenland ice sheet surface melted, as did record amounts of the Arctic ice cap, and ocean temperatures were high. How were all these things linked? What was the underlying cause?

It seems that there is, in fact, a connection between some of these things - but not all. There's now some new research out on the abnormally widespread Greenland surface melting, which caused such a media sensation at the time. A lot of people thought that warm seas and/or the summer melting of the Arctic cap might be involved, but it seems that this isn't the case.

According to an announcement from Sheffield uni, highlighting a new paper published in the International Journal of Climatology:

The research clearly demonstrates that the record surface melting of the [Greenland ice sheet] was mainly caused by highly unusual atmospheric circulation and jet stream changes, which were also responsible for last summer's unusually wet weather in England.

Sheffield's Professor Edward Hanna, who led the investigating boffins, has this to say:

"These jet stream changes over Greenland do not seem to be well captured in the latest Intergovernmental Panel on Climate Change (IPCC) computer model predictions of climate change, and this may indicate a deficiency in these models."

Such jet-stream shifts have not been seen before since satellites began monitoring the world's ice thirty years ago, and in the prof's view most likely have not happened for a century or so. It's always possible that they'll now happen every thirty years, or more commonly than that even, but it's also very possible that they won't and that last year was just the sort of thing that happens sometimes.

Of course if the Greenland melting and washout British summer resulted instead from warmer oceans and/or Arctic cap melt, one could count on such things happening again soon. But in the prof's view, this is not the case. The Sheffield statement says bluntly:

Ocean temperatures and Arctic sea-ice cover were relatively unimportant factors

Those with the relevant subscription can read the scientific paper here.

"[The summer of] 2012 seems not to be climatically representative of future ‘average’ summers projected this century," write Hanna and his colleagues.

“The next five-10 years will reveal whether or not 2012 was a rare event resulting from the natural variability of the North Atlantic Oscillation," adds Hanna.

Which could all be good news, perhaps, for Brits planning a staycation this year and coming ones. ®

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