Dangerously cold temperatures are hitting the Eastern US this week, prompting President Donald Trump to tweet: “In the East, it could be the COLDEST New Year’s Eve on record. Perhaps we could use a little bit of that good old Global Warming.” But scientists say that the record low temperatures and record high snowfalls aren’t proof that global warming is a hoax: they’re precisely the weather you’d expect in a warming world.
There’s a lot of wrongness to unpack in Trump’s tweet, so we’ll focus on that intractable myth that climate change spells the end of cold weather. It doesn’t.
To be clear, climate and weather are not the same thing. Weather is the local, day-to-day variation; climate represents the longer-term, farther-reaching conditions. A rainy day in Phoenix, for example, doesn’t change the fact that Arizona’s climate is dry, NASA’s Climate Kids webpage says. 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,” environmental journalist Kendra Pierre-Louis writes for The New York Times.
So, cold weather can still happen as global temperatures rise. “The trip to a warmer world (climate change) will have plenty of extreme hot and cold weather,” NASA’s Climate Kids site patiently explains. We’ll just see more of those extremely hot days as the planet warms, according to the climate change tracking platform Climate Signals and scientist Michael Mann. He tweeted that record hot days are beating record cold days three to one.
Right now, a warm ridge of high-pressure air is hovering over the Western US, forcing the highway of winds that would normally bring cool, rainy weather to California up into Canada. That’s causing the extended warm, dry spell fueling California’s wildfires and the East Coast’s icy temperatures. When the jet stream plunges back down, it carries frigid air, “mainlining cold to the eastern half of the US,” Brian Kahn writes for Earther.
Scientists led by Stanford’s Noah Diffenbaugh have studied this strange seesaw effect on temperatures across North America, where upward swings in winter temperatures in the west correspond with icy drops to the east. They found that this warm west / cold east combination is happening more often as the climate warms. “We have strong evidence that not only does it not invalidate global warming, but it’s actually very consistent with what we’d expect,” Diffenbaugh tells The Verge.
Climate change also makes lake-effect snow likelier — just like the drifts that piled five feet high in Erie, Pennsylvania, over Christmas, climate scientist Katharine Hayhoe said on Twitter. When the lakes are cold enough to freeze over, this doesn’t happen. But as long as they remain liquid, cold air can blow over the lakes, picking up water vapor. The vapor rises, cools, and then falls back to Earth as snow. “[The] air acts like a big sponge that sops up water from the lake and wrings it out on land,” NASA and NOAA’s SciJinks website says.
Warmer temperatures make it harder for the Great Lakes to freeze over, and that means more snow. Combined with natural climate cycles like La Niña, that’s what’s happening this year, Hayhoe tweets. And we can expect more lake effect snow in the future — at least, until temperatures rise so high that it becomes too warm for snow. Then that water will fall as rain.
The guy from Jersey Shore gets it: "I think climate change is more complex than global warming will make it hotter," Vinny Guadagnino said on Twitter, entirely correctly.