2009/10 was caused by a rare combination of two separate weather oscillations in the Atlantic and Pacific, claim meteorologists.

The harsh winter and heavy snow surprised forecasters, arriving with temperatures at the lowest they’d been for nearly 30 years. Some climate skeptics cited the conditions as evidence against climate change, while other people pointed out that most climate change predictions include an increase in extreme weather events.

But the research, published in Geophysical Research Letters, claims that neither are correct, and that the freak weather was actually caused by an unusual match-up of a moderately strong El Niño event, and an extremely strongly negative North Atlantic oscillation.

Each has a different effect on the weather. An El Niño event tends to push storm systems towards the equator, making the weather in the US and Northern Europe wetter than normal. The North Atlantic Oscillation, on the other hand, doesn’t cause precipitation, it just makes it very cold. When they combine, you get very cold, wet, conditions — snow.

Richard Seager, a meteorologist at the Lamont Doherty Earth Observatory at Columbia University is one of the co-authors of the paper. He told the BBC: “The NAO was probably as negative as it’s ever been in the instrumental record, which goes back to the early 1800s. This was a once in a century type of event.” Investing in a snow plough for the coming winter is probably unwise, therefore.

As for those who raised the spectre of climate change, Seager is scathing in his dismissal: “Weather will continue to be weather. You have to average over a lot of weather to get the climate trends. There doesn’t seem to be any need to evoke anything else other than that.”

Image: Snow covered Great Britain on January 7, 2010./NASA.

See Also:

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• Russian Heat, Asian Floods May Be Linked
• Pakistan’s Climate Change Floods, Seen From Above
• MIT: Your Meteorologist Needs an Army of Drones
• Pakistan’s Climate Change Floods, Seen From Above
• Reader Photo Gallery: Crazy Dust Storm Turns Sydney Red

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Authors: Duncan Geere

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