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 say.
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 and cold air south.
Around the entire Arctic region, temperatures are now about 20degC above normal, at -8degC, according to DMI calculations.
To the south, a rare snow storm hit Rome on Monday (local time) and some Brussels mayors planned to detain homeless overnight if they refused shelter with temperatures set to fall as low as -10degC in the coming week.
Hit by easterly winds from Siberia, cities from Warsaw to Oslo were colder than -8degC.
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" (WAC#C) 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.
Arctic Ocean sea ice is at a record low for late February at 14.1 million square km, according to the US National Snow and Ice Data Centre.
That is about a million less than normal, or roughly the size of Egypt.