Friday 20 July 2018

‘Wacky’ weather may happen more as Arctic warmer than Europe

File photo of snow in Leitrim Photo: Joe Hunt
File photo of snow in Leitrim Photo: Joe Hunt

Alister Doyle

A freak warming around the North Pole is sending a blast of Arctic cold over Europe in a sign of “wacky” weather that may happen more often with man-made global warming, scientists said yesterday.

On the northern tip of Greenland, the Cape Morris Jesup meteorological site has had a record-smashing 61 hours of temperatures above freezing so far in 2018, linked to a rare retreat of sea ice in the Arctic winter darkness.

“It’s never been this extreme,” said Ruth Mottram, a climate scientist at the Danish Meteorological Institute (DMI). Warmth was coming into the Arctic both up from the Atlantic and through the Bering Strait, driving cold air south.

Around the entire Arctic region, temperatures are now about 20C above normal, at -8C, according to DMI calculations.

To the south, a rare snow storm hit Rome yesterday and some Brussels mayors planned to detain homeless overnight if they refused shelter with temperatures set to fall as low as -10C in the coming week.

Hit by easterly winds from Siberia, cities from Warsaw to Oslo were colder than -8C.

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As long ago as 1973, a study suggested that an ice-free Arctic Ocean could make regions further south colder.

That “warm Arctic, cold continent” (WACC) pattern is sometimes dubbed “wacc-y” or “wacky” among climate scientists.

“Wacky weather continues with scary strength and persistence,” tweeted Professor Lars Kaleschke, a professor at the University of Hamburg.

“The question is whether this weather will happen more often.

“This is just one event so it’s hard to make a causal relationship,” he told Reuters.

Scientists say a long-term shrinking of sea ice on the Arctic Ocean, linked to global warming, exposes warmer water below that releases more heat into the atmosphere. That in turn may be disrupting the high altitude jet stream.

“The jet stream becomes wavier, meaning that colder air can penetrate further south and warmer air further north,” said Nalan Koc, research director of the

Norwegian Polar Institute.

The World Meteorological Organisation said the chill in Europe was caused by a “sudden stratospheric warming” above the North Pole that led to a split in the polar vortex, a cold area of air above the Arctic that spilled cold south.

A big problem in figuring out whether the Arctic warmth is driven by human activities or natural variations is a lack of measuring stations.

There are no thermometers at the North Pole and satellite measurements go back only to the late 1970s.

Irish Independent

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