In its hottest December ever recorded, Alaska was a stunning 15.7°F above the 20th century average. And the year ended with Arctic sea ice hitting an all-time record low.

While the East Coast had a cool December and New Year’s week, Alaska baked. Last Tuesday, Anchorage hit 48°F, warmer than southern cities from Atlanta and Jacksonville to Houston and New Orleans.

The National Oceanic and Atmospheric Administration (NOAA) reported this week that Alaska averaged 19.4°F for the month, topping the previous record (1985) by a whopping 2.1°F. “That’s really quite astonishing,” said Rick Thoman, the National Weather Service’s climate sciences and services manager for the Alaska region. As he explained to the Anchorage Daily News, “Usually you’re breaking those by a tenth of a degree or two-tenths of a degree.”

The Arctic as a whole was so warm in December that Arctic sea ice set a new end-of-year record low, as both the U.S. National Snow and Ice Data Center and the Japan Aerospace Exploration Agency (JAXA) reported.

Arctic sea ice extent hits record low the last week of December (red line).

Climate models have always predicted that human-caused warming would occur at least twice as fast in the Arctic, compared to the planet as a whole, thanks to Arctic Amplification — a process that includes higher temperatures melting highly reflective white ice and snow, which is replaced by the dark blue sea or dark land, both of which absorb more solar energy and lead to more melting.


Unfortunately for the rest of the globe, what happens in the Arctic does not stay in the Arctic. Arctic amplification drives more extreme weather in North America, while accelerating the defrosting of the carbon-rich permafrost, releasing carbon dioxide and methane that each cause faster warming — a dangerous amplifying feedback.

At the same time, as the sea ice disappears and Arctic warming speeds up, the the land-based Greenland ice sheet melts faster, which speeds up sea level rise. One 2017 study found that Greenland ice mass loss has tripled since 1997.

The “climate is warming much more rapidly at high latitudes,” said Thoman. “Alaska, of course, being the only Arctic part of the U.S. … We are the U.S.’s canary in that coal mine.”