Even as the North Pole soared above freezing, much of Europe—including Moscow, above—shivered. Alexander Zemlianichenko / AP

In December, a team of U.S. government scientists released a “report card” on the Arctic. Their top conclusion was pithy, comprehensive, and bleak. The Arctic, they said, “shows no sign of returning to [the] reliably frozen region of recent past decades.”

Now, it’s almost like the environment is trying to prove them right.

Though the sun hasn’t shone on the central Arctic for more than four months, the region is currently gripped by historic, record-breaking warmth. On Sunday, the temperature at the North Pole rose to about the melting point, and parts of the Arctic were more than 50 degrees Fahrenheit warmer than normal.

A handful of Arctic scientists spent the weekend on Twitter, trying to put the episode into context:

To understand how strange the recent Arctic weather is, it’s worth looking at a place called Cape Morris Jesup.

Cape Morris Jesup is a barren and uninhabited promontory above the Arctic Ocean. Just 450 miles from the North Pole, it is Greenland’s northernmost point. (In fittingly weird fashion, it’s named after Morris Ketchum Jesup, a terrifically mustachioed American banker who helped found the YMCA and the American Museum of Natural History, and helped fund the Arctic expeditions of Robert Peary.)

The sun hasn’t shone on Cape Morris Jesup since October 11. These should be among the coldest weeks of the year for the cape. But over the weekend, the weather station there recorded an air temperature of 43 degrees Fahrenheit, more than 50 degrees above normal for this time of year.

The weird warmth was not limited to that one spot. Station Nord, a scientific research station in Greenland nearly 200 miles to the southeast, recorded temperatures of about 36.5 degrees Fahrenheit this weekend.

These kinds of on-the-ground observations aren’t available for the North Pole. But by combing satellite observations and other temperature data, the top U.S. forecast model estimated that temperatures at the North Pole rose as high as 35 degrees Fahrenheit, according to The Washington Post.

This isn’t the only oddity in the Arctic right now. Every year, the Arctic Ocean goes through a two-part seasonal cycle. From late September to early March, its surface hardens into a huge solid mass, creating a vast ice sheet that stretches from Newfoundland to Siberia. Then, from late March to early September, much of that sea ice melts, and much less of the ocean surface is ice-covered.

At this time of year, sea ice should still be growing and expanding. But recent satellite observations have shown that two large gaps have somehow opened up in the ice. The first is in the Chukchi Sea, near Russia. The second, pictured below, is just north of Cape Morris Jesup in Greenland. The blue gaps are open water:

Arctic Sea Ice, From February 20 to February 25, 2018

A map of sea ice as observed on the Arctic Ocean, from the Canadian Arctic (at left) to Svalbard (center-right), created by Lars Kaleschke, a professor of sea-ice remote sensing at the University of Hamburg. The data is from GCOM-W1, a Japanese climate-science satellite.

These two gaps mean that sea-ice formation has stagnated more than a month early. And even before this current warmth, it has been a dismal year for Arctic sea ice. The Arctic Ocean is on track to set a new record this year for the smallest extent of winter sea ice ever recorded. This would be the fourth straight year that the Arctic sets a new wintertime sea-ice record low.

How rare is this kind of Arctic warmth? Climate scientists say they have seen events similar to this one happen before, but that the size and intensity of the warmth made it really notable.

“There are other cases in the reanalysis record with greater than 20 degree Celsius departures” from normal temperatures, said Zachary Labe, a sea-ice researcher at the University of California at Irvine, in an email. “However, it does appear this particular event featured one of the largest departures on record.”

The anomalous Arctic warmth comes just as Western Europe deals with record-breaking cold. A cold front dubbed “the beast from the East” has moved in from Russia to occupy much of Europe. Several inches of snow fell on Rome and London on Monday. And temperatures in Italy are about 30 degrees Fahrenheit below normal.

Just How Much Hotter (or Colder) Is It Than Usual?

The Climate Reanalyzer, a tool from the University of Maine, uses data from the U.S. weather model to show how far temperatures have deviated from historic norms. On February 26, 2018, the Arctic was almost 5.4 degrees Celsius (about 10 degrees Fahrenheit) warmer than normal, while much of Europe was almost 10 degrees Celsius colder than normal.

Are the two events related? Meteorologists say it’s hard to say for now. Many Americans will recognize the underlying pattern of a “polar vortex” that descends unusually far south, chilling the mid-continent while allowing warm air to rush into the Arctic itself, as we’ve experienced it ourselves a handful of times in the past half-decade. In an email, Labe said that the “blocking pattern” caused by cold over Scandinavia “certainly played a significant role for this warm air to intrude into the Arctic.”

But other factors shaped the warmth too. Low Arctic sea ice probably exacerbated the pattern, allowing an already warm region to heat up more. In early February, the temperature of the high atmosphere above the Arctic suddenly spiked—a mysterious process called sudden stratospheric warming—and that probably helped destablize the polar vortex, too.

The Roman skyline, with the Monument of the Unknown Soldier visible at right, was covered in snow on Monday. (Alessandra Tarantino / AP)

And along with all those causes, there’s climate change, which is slowly but inexorably raising the planet’s temperature. In fact, the recent Arctic warming illustrates two of the most worrying aspects of global warming.

First: Warming in the Arctic is actually outpacing the rest of the world, according to another recent U.S. government report, due to a little-understood phenomenon called Arctic intensification. In 2016, for instance, worldwide temperatures were about 1.78 degrees Fahrenheit above normal. But for much of that year, Arctic temperatures were more than 3.5 degrees above normal.

Second: There are many arbitrary tipping points in Earth’s climate system. The Paris Agreement on climate change, for instance, tries to prevent global temperatures from rising 3.6 degrees Fahrenheit. That may not sound like a lot. But the difference between 30 and 33.6 degrees Fahrenheit is much more than “just” 3.6 degrees—it’s the difference between a solid chunk of sea ice and an open ocean, between the “reliably frozen region” of the recent past and a daunting, new, half-melted desert.