With a major winter storm bearing down on the Eastern United States, you can expect some people (and, perhaps inevitably, President Trump), to ask, “What happened to global warming?”
It’s becoming increasingly clear that climate change does have an effect on storms, though the relationship can be complex and, yes, counterintuitive. “There were these expectations that winter was basically going to disappear on us,” said Judah Cohen, director of seasonal forecasting at AER, a company that provides information to clients about weather and climate-related risk.
Although winters are becoming warmer and somewhat milder overall, extreme weather events have also been on the increase, and especially in the Northeastern United States, as Dr. Cohen pointed out in a recent paper in the journal Nature Communications. From the winter of 2008-9 until 2017-18, there were 27 major Northeast winter storms, three to four times the totals for each of the previous five decades.
One of the factors potentially feeding storms is a warmer atmosphere, which can hold more water vapor; not only can that mean more precipitation, but when the vapor forms clouds, “it releases heat into the air, which provides fuel for storms,” said Jennifer Francis, a senior scientist at the Woodwell Climate Research Center. Also potentially important, but less understood, she noted, is “the increased tendency for the jet stream to take big swoops north and south,” setting up weather phenomena like the dreaded polar vortex.
Does that mean this particular storm has been fueled by climate change? Jonathan E. Martin, a professor in the department of atmospheric and oceanic sciences at the University of Wisconsin-Madison, cautioned against drawing quick conclusions.
Because of the “enormous natural variability” in storms and the weather they deliver, “I think it is a dangerous business attributing individual winter storms, or characteristics of them, to climate change,” he said. And this storm in particular, he added, is getting a lot of its moisture from water vapor evaporated off the Atlantic Ocean, which complicates the picture.
Dr. Francis agreed that any connections are complex, but added, “all storms now form in a greatly altered climate, so there’s little doubt that the same storm decades ago would not be the same.”