By the time you read these words, winter's grip should have mostly loosened in the Northern Hemisphere. But at its worst, this winter was brutally cold. Here in New York City on January 31, the low temperature snuck down to two degrees Fahrenheit. In Chicago, it was also two degrees—but that was the high. The low plummeted to −20. Which was two degrees warmer than the low the day before. And the wind chill in the Windy City was −51 or −52, depending on which weather station was crying out in agony. As comedian Lewis Black once said of Minnesota (which was similarly afflicted in January), “That is not weather. That's an emergency condition.”

When the forecast warned us a couple of days earlier that Arctic air was looming, the president issued a sincere and helpful tweet, which ended with: “What the hell is going on with Global Waming [sic]? Please come back fast, we need you!” And being the most powerful man on Earth, he was successful in his polite imploration. On February 4 the Chicago temperature reached 51 degrees. And the next day the Big Apple basked in a sunny 65.

The Arctic is warming at twice the rate as the global average. This heat can help disrupt the polar vortex, a steady wind pattern that usually stays focused on circling the North Pole. A wobbly jet stream then runs into a brick wall of that Arctic air, which is still pretty frosty by human standards, and both wind up hundreds of miles farther south than they usually belong. And for a few days we in the Deep South—by which I mean Chicago or New York compared with the Arctic—freeze our butts off. But less than a week after this most recent vortex disruption, thanks to some warm air coming up from the real South, I was walking outside without a coat. On a date when the average high temperature is about 40.

Like so much else we are currently living through, this kind of thermometer ride is not normal. Or it didn't used to be, anyway.

Of course, scientists have been waming—sorry, warning—that warming can have these very effects. Climate change deniers may sneer, “So when it's warmer than usual, that's because of global warming. And when it's colder, that's also because of global warming?” Well, yes. And anybody who just can't accept these kinds of seemingly paradoxical situations needs to reflect on the expression “freezer burn.”

In the midst of this wacky weather came Groundhog Day. And I happened on a 2010 interview with noted climatologist Katharine Hayhoe of Texas Tech University, in which she pointed out: “It's been mathematically proven that it's impossible to predict the evolution of a chaotic system like weather for more than two weeks. As everyone knows, though, the laws of physics don't apply to groundhogs.” She also remarked that for groundhog weather forecasting to be truly scientific, its “findings would need to be published in scientific journals such as the Journal of Groundhog Predictions where they would be reviewed for accuracy by other groundhogs.” How Hayhoe could be understood with her tongue so securely embedded in her cheek is a scientific mystery.

In a completely unrelated development, alligators eat stones. As writer Jake Buehler explains in the journal Science, it's long been known that the beasties dine on the rocks. Favored explanations have included the incidental swallowing of mineral while eating animal or vegetable and the ingestion of stones to help mash up the meat in their digestive tracts—akin to what many birds do.

But a new explanation for this gastrolith activity has appeared. Tests with seven captive American alligators found that when they had taken in a bunch of rocks, they were able to hide underwater 88 percent longer. The weight appears to work against the tendency to float back to the surface when the lungs are filled with air. Because if you're going to successfully cope with the laws of physics, it's far better to have stones in your stomach than rocks in your head.