Many things are happening all around the world, but on the East Coast of the United States, it’s currently very warm. Very warm. Half-the-country-is-asking-whether-you-can-wear-shorts-to-work-in-February warm.
Here’s some context. On Tuesday, temperatures sat at or well above 70 degrees Fahrenheit from Massachusetts to Miami. Boston broke its record for the warmest night ever recorded in the month of February, at a balmy 50 degrees Fahrenheit. More than 1,100 miles south, in Tampa, Florida, daytime temperatures rose to 89 degrees Fahrenheit, the warmest temperature ever recorded there in the month of February. Cincinnati and Pittsburgh also set all-time February records.
[250 pm Tue 2/20] The temp at Boston has climbed to 69 degrees, and at Worcester the temp has reached 66. The breaks the record high for today's date at both locations. #MAwx— NWS Boston (@NWSBoston) February 20, 2018
Wednesday will also be nice. Across the eastern half of the country, temperatures will rise above 70 degrees, with warmer air the farther south you go. If Washington, D.C., hits 80 degrees Fahrenheit on Wednesday—which is entirely possible—it will be the earliest 80-degree-Fahrenheit day ever recorded in the nation’s capital, where weather logs go back more than a century.
How to make sense of all this heat? Here are three perspectives.
1. From a meteorology perspective, the heat is the result of two air patterns currently interacting over North America.
There’s a huge heat dome off the coast of Georgia and northern Florida. Air is moving clockwise around the dome, creating a conveyor belt of warm, moist tropical air from the Gulf of Mexico.
At the same time, there’s a huge cold front moving across North America, sweeping warm air in front of it. As it plows eastward, it’s restoring wintertime temperatures. The Washington Post’s Angela Fritz notes that as the cold front moved across Oklahoma City on Tuesday, temperatures dropped 21 degrees—in just four minutes.
It’s clear that all this warmth is unusual. According to the University of Maine’s Climate Reanalyzer, the eastern half of North America is almost 10 degrees Celsius (or 18 degrees Fahrenheit) above normal:
But are these temperatures—the ones we’re feeling today—the result of global warming? Without a few weeks of research, it’s hard for climate scientists to say for sure. But they can say a lot.
2. From a climatological perspective, it’s time to get used to the winter heat. One big sign of human-caused climate change is warmer winters. According to Climate Central, a nonpartisan group that researches the effects of climate change, winters in Minneapolis are now 6 degrees Fahrenheit warmer than they were in 1970. Winters in Burlington, Vermont, are 7 degrees Fahrenheit warmer.
Meanwhile, cold snaps—like the two-week spell that hit much of the United States in December—are 15 times less likely to strike now than they were a century ago.
The last few winters have been especially warm, which makes sense, as the last three years have also been the three warmest years ever measured. In Toronto, all three of the hottest February days on record have occurred since 2016.
This trend will continue as the century wears on, according to the Climate Impact Lab, a team of economists and climatologists from UC Berkeley, Rutgers University, the University of Chicago, and the Rhodium Group. They calculate that, between 1981 and 2010, Pennsylvania experienced an average of 105 days below freezing every year. But by the end of the 21st century, if greenhouse-gas emissions continue to grow, it will see only 50 days below freezing.
For now, these warmer winters appear partly as early springs. The National Phenology Network says that spring has already started to arrive—as measured by blossoming trees—as far north as Virginia and West Virginia. But that doesn’t mean East Coasters won’t face a cold snap in a week or two. In some parts of New England, it could even snow on Thursday.
3. From an economic perspective, all these warm winters are one of the best parts of climate change! At least as far as people are concerned.
In a paper published in Science last year, a number of economists—many of them associated with the Climate Impact Lab—argued that the warm winters of global warming would bring limited economic benefits to northern U.S. states. Early deaths are one of the worst costs of climate change, and more people die of winter cold than summer heat in the North, they reasoned. Therefore, as wintertime temperatures rise, early mortality in the North should fall.
There’s even an economic literature (albeit a small one) looking at how warmer winters may encourage northern Americans to exercise more.
But note that these benefits are very minor, and the Climate Impact Lab also found that they were swamped by a raft of economic damages, mostly in the Sunbelt and near the Gulf Coast. (Most of which arise from elevated summer heat.) As such, they argued that climate change would worsen regional U.S. inequality.
Of course, that cheery view about warmer winter doesn’t capture many costs that are harder to calculate (as the Climate Impact Lab recognizes, to be clear). Warmer winters will also cause sea ice in the Arctic Ocean to vanish, endangering polar bears and cutting them off from their food source, for instance. But polar bears don’t have jobs, and they don’t buy anything, so their economic benefits are less clear.
And there are other problems with these late-winter warm snaps. Last year, a series of balmy, late February days convinced the famous cherry trees of Washington, D.C., that it was time to blossom. Then a snowstorm struck in mid-March. Many of the blossoms froze and fell off the tree, resulting in a denuded natural show for the city’s annual National Cherry Blossom Festival.
And these three lenses aren’t the only way to understand the warmth. Other disciplines might have their own contributions. A groundhog hater might remind us that Punxsutawney Phil saw his shadow a few weeks back, falsely forecasting six more weeks of winter. And a Portlander might insist that not all weather happens on the East Coast. On Tuesday evening, that city saw one to four inches of the fluffy white stuff come down—its first snow of the year.