Just because I live in South Florida doesn’t mean I don’t feel for the people who live up north where some of the coldest weather in a generation is taking hold.
Forecasters expect Wednesday’s high temperature (yes, the high) to be minus 14 degrees Fahrenheit in Chicago and Minneapolis. If the forecast holds, that would be Chicago’s lowest high temperature for a single day since officials began keeping records. An expected low of minus 22 was expected to approach, though not surpass, the coldest temperature ever recorded in Chicago. Officials predicted that wind chill readings could plummet to minus 50 in Chicago and minus 60 in Minneapolis.
“This is what you would expect when you get into central and northern Canada,” said Brian Hurley, a National Weather Service meteorologist.
The vortex, a brutal mass of cold air within strong bands of circulating winds, has spread southward from its normal location near the North Pole in recent weeks, bringing arctic weather to the middle of the United States. Such weather events have become more common in recent years; scientists are not sure why, but some suspect a link to climate change.
I can hear the climate-change deniers now: “Hey, what happened to all that global warming, snowflakes? Har-de-har-har.”
The answer lies in the difference between local weather and climate.
Climate refers to how the atmosphere acts over a long period of time, while weather describes what’s happening on a much shorter time scale. The climate can be thought of, in a way, as the sum of long periods of weather.
Or, to use an analogy Mr. Trump might appreciate, weather is how much money you have in your pocket today, whereas climate is your net worth. A billionaire who has forgotten his wallet one day is not poor, anymore than a poor person who lands a windfall of several hundred dollars is suddenly rich. What matters is what happens over the long term.
Even on a day when it is colder than average where you live, the world as a whole is frequently warmer than average, which you can see for yourself on these daily maps from the University of Maine.
While climate scientists expect that the world could warm, on average, roughly two to seven degrees Fahrenheit by the end of the century — depending on how quickly greenhouse-gas emissions rise — they don’t expect that to mean the end of winter altogether. Record low temperatures will still occur; they’ll just become rarer over time.
One 2009 study found that the United States saw roughly as many record highs as record lows in the 1950s, but by the 2000s there were twice as many record highs as record lows. Severe cold snaps were still happening, but they were becoming less common.
Some recent cold spells have been caused by a dreaded weather system called the polar vortex. There’s growing evidence to suggest that the polar vortex is appearing outside the Arctic more frequently, because of changes in the jet stream that are attributed to the warming atmosphere. These changes help frigid air escape from the Arctic and swoop southward.
Climate change brings about weather extremes more often. 2018 was one of the warmest years in recent memory — remember the heat waves last summer? So the cold is getting colder, the heat is getting hotter, and it’s only going to get worse the more carbon we dump into the atmosphere.
Meanwhile, seeing the current temperature in Minneapolis of -4 F is cold comfort for knowing that tomorrow night the low is predicted to be -25 F without the wind.