Bitter cold continues to grip the United States as unusual freezing temperatures stretch as far south as Florida this week. Even more chilly weather is in store through the weekend, putting more than 80 percent of the US population under some type of cold weather advisory.

But this jarring cold snap is sandwiched between the end of what was the hottest year on record and the start of another year that could be even hotter. And even as temperatures plunge to new depths, the recent weather isn’t remotely enough to derail an ominous trend.

As the climate changes, the bottom of the temperature scale is rising faster than the top. This pronounced winter warming is often less palpable than the triple-digit summer heat waves that have become all the more frequent across much of the country, but no less profound.

According to Climate Central, more than 200 locations around the United States have lost almost two weeks of below-freezing nights since 1970. By 2050, 23 states are projected to lose upward of a month of freezing days.

“In general, winters have been getting warmer across the country, and really across the world,” said Pamela Knox, an agricultural climatologist at the University of Georgia extension. “It turns out that the colder seasons are warming up more quickly than the warmer seasons.” Warmer winters are one of the strongest examples of how humanity has changed the world with its ravenous appetite for fossil fuels, which emit greenhouse gases into the atmosphere and drive up global temperatures.

That doesn’t just mean fewer good ski days or the end of white Christmases for some regions; cold weather is an important, essential signal for plants and animals, and losing it has far-reaching effects on the economy, food production, and health.

Why winters in particular are heating up

Though Earth is warming on average, those changes aren’t distributed evenly across the planet or throughout the year. The Arctic, for example, is warming about four times as fast as the rest of the world as the sunlight-reflecting ice yields to the darker, heat-absorbing ocean below.

The cold seasons are also heating up disproportionately further south, albeit at a slower pace than the North Pole. According to the fifth National Climate Assessment, a report by 14 US government agencies........

© Vox