Natural shift in Jet Stream to blame for cold snap
According to climatologists, an atmospheric blocking of the Jet Stream — a narrow band of fast-flowing air that normally dictates the Irish weather— has resulted in weather anomalies, bringing Arctic weather to Europe and temperature increases of up to 10C in Canada and Greenland.
Director of the Irish Climate Analysis and Research Units (ICARUS) Professor John Sweeney said that the North Atlantic Oscillation, a component of the Arctic pressure system, has gone very strongly “negative” in the past year.
“For the last 20 years the Oscillations have been more positive than negative bringing us relatively mild weather, but in the last year the North Atlantic Oscillations have turned negative bringing cold bursts. As a result, some places get stuck on the wrong side of the block, getting continental air rather than maritime air.”
However, according to Prof Sweeney the current cold snap should not be confused with long-term climate change.
“2010 will have been one of the three hottest years since instruments for measuring climate became reliable. However, it has been once of the coldest Decembers seen in Ireland over the last century. It would be a bit premature to suggest that the cold may be a trend which can be expected for next winter, but we do tend to get clusters of cold winters and as long as the North Atlantic Oscillation remains negative, it is possible that the cold will continue.”
Prof Sweeney said there are a number of suggestions to explain the shift in the Jet Stream. “One is that, due to the melting of ice in the Arctic Sea, there has been a reduction in pressure that drives the Jet Stream, or it may be down to a period of low solar activity, but a lot more evidence is needed before there can be any suggestion can be considered definitive,” he added.
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