One notable feature of climate change is how the coldest parts of the planet are seeing the most extreme effects. Up north, for instance, Alaska shattered its statewide temperature record on Dec. 26, when a tidal station off Kodiak Island recorded an incomprehensible 67 degrees Fahrenheit. Nearby Kodiak City registered 65 degrees, which not only broke its record for that particular date by 20 degrees and its monthly record by nine degrees, but also would have set a record for any day between Oct. 5 and April 21. Cold Bay, Alaska broke its daily record by 18 degrees, which would have set a monthly record from November to April.

Setting heat records by that kind of gigantic margin is totally inconceivable without climate change.

Ironically, that warmer, moister air is now expected to hit unusually cold temperatures to produce freezing rain and unusually heavy snow that will encase cities across the state in ice. That kind of erratic see-sawing between extreme conditions is also fast becoming a classic characteristic of climate change.

On the opposite side of the planet, new science has found that a key Antarctic ice sheet is even more unstable than previously thought. A large group of scientists studying the Thwaites Glacier (which is about the size of Florida) recently found troubling new evidence suggesting it may collapse entirely, possibly in less than a decade, which would have dire consequences indeed.

“It’s doubled its outflow speed within the last 30 years, and the glacier in its entirety holds enough water to raise sea level by over two feet,” Ted Scambos, the lead scientist on the project, said in a press release. Worse, Thwaites currently blocks the rest of the West Antarctic ice sheet from the ocean. Should it collapse, it “could lead to even more sea-level rise, up to 10 feet, if it draws the surrounding glaciers with it,” said Scambos.

As Jeff Goodell writes at Rolling Stone, just two feet of sea-level rise would put huge chunks of southern Florida permanently underwater, as well as dozens of other coastal cities in the U.S. and around the world.

As Alaska and Antarctica melt, it’s a reminder that climate change isn’t just an issue for environmentalists — it’s a clear and present danger to the physical security of the American people and all humanity.