With an Arctic blast chilling the northern states, U.S. President Donald Trump tweeted over the weekend that it “Wouldn’t be bad to have a little of that good old fashioned Global Warming right now!”

The apparent irony that cold weather can strike a warming world is a time-tested line for Trump, Republican colleagues on Capitol Hill and even late-night talk show hosts. Nothing diffuses a joke quite like further analysis, under which this one falls apart.

Trump’s statement confuses weather, which is short-term local fluctuations that people check every morning before stepping outside, and climate, which is the long-term aggregate of everything that happens weather-wise in an area or globally. Confusing the two is like conflating a Major League Baseball slugger’s lifetime batting average with a single trip to the plate, or a person’s character or disposition with a fleeting mood.

A January cold snap across many U.S. states doesn’t contradict the planet’s long-term warming trend.

A map of today’s weather shows the gradual outline of what one might expect given basic information about how the seasons work. It’s summertime in the planet’s Southern Hemisphere — particularly Australia, which is experiencing a historic heat wave so hot that a restaurant in Mildura, Victoria, claimed on its Facebook page to be able to cook a steak inside a car. A pocket of brutal Arctic coldness has escaped to southeastern Canada and the northeastern U.S., with frigid air draping the northern half of the U.S.

The ultimate irony is that global warming may have a hand in the cold. Research by Rutgers University research professor Jennifer Francis and others has suggested that, because the Arctic is warming twice as fast as the rest of the globe, the temperature difference between temperate latitudes and the high north is diminishing, encouraging these wintry blasts to slip into America’s northeast.

The big picture is clear and has been for many years. Every decade has been warmer than the last since the 1960s and the world is about 1 degree Celsius (1.8 Fahrenheit) hotter than before industrialization. Many years since 1991 have set new global ocean heat records.

Arctic ice is shrinking, seas are rising and scientists have long demonstrated the overwhelming driver is greenhouse gas pollution. The National Oceanic and Atmospheric Administration maintains a rich archive of data and information at climate.gov — when the U.S. government is funded.

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