Icy Europe, balmy North Pole: A world upside down
Experts say climate change has warmed the Arctic region faster
PARIS — Not for the first time in recent years, Europe has descended into a deep freeze while the Arctic experiences record high temperatures, leaving scientists to ponder the role global warming may play in turning winter weather upside down.
A Siberian cold front has spread subzero temperatures across Europe, carpeting southern cities and palmlined Mediterranean beaches with snow.
On Sunday, meanwhile, air temperatures at the North Pole — which won’t see the Sun until March — rose above freezing.
“In relative terms, that’s a 30 C temperature anomaly,” Robert Rohde, lead scientist at Berkeley Earth in Washington, tweeted.
At the Longyearbyen weather station on the Island of Svalbard in the Arctic Ocean, temperatures were 10 C above average over the last 30 days, according to Zack Labe, a climate modeler at the University of California Irvine.
At the same time, sea ice is covering the smallest area in the dead of winter since records began more than half a century ago.
“Positive temperatures near the North Pole in winter are thought to have occurred during four winters between 1980 and 2010,” said Robert Graham, a climate scientist at the Norwegian Polar Institute.
“They have now occurred in four out of the last five winters.”
This acceleration, experts said, circumstantially points to climate change, which has — over the same period — warmed the Arctic region twice as fast as the global average.
If the connection with global warming remains speculative, the mechanics of what scientists call “sudden stratospheric warming” — the weird winter weather’s immediate cause — is well understood.
Strong winds in the stratosphere circulate west-to-east over the Arctic some 30 kilometers above Earth’s surface. This is the polar vortex.
The jet stream, meanwhile, races in the same direction at bullet-train speed 10 kilometers overhead at the upper boundary of the troposphere, the lowest layer of the atmosphere.
‘Locked’ air
Sometimes the vortex dramatically warms and weakens, with winds slowing down and even reversing, said Marlene Kretschmer, a climate scientist at the Potsdam Institute for Climate Impact Research.
“When this happens, it can affect the jet stream where our weather is made,” she said. “That is exactly what has happened now.”
Freezing Arctic air that is normally “locked” in the polar vortex breaks out, creating the Siberian cold front that has blanketed Europe.
Sudden stratospheric warming occurs, on average, every other year, so it is not a rare phenomenon. But over the last two decades, the vortex’s breakdowns have become deeper and more persistent.
One theory holds that newly ice-free ocean surface — which absorbs the Sun’s rays rather than bouncing them back into space like snow — releases warmth into the air that eventually disrupts the stratosphere.
“It is hard to say that any one event is linked to global warming,” said Kretschmer.
“But there are a lot of studies now suggesting this pattern — warm Arctic, cold continent — could be linked to climate change.”
“This much is certain — there is overwhelming evidence that changes in the Arctic will affect our weather,” she added.