With the American Midwest looking like assembly line central for tornadoes this spring, many are wondering whether a toll of 1,000 twisters and counting means climate change—or just a very bad year.
“Eccentric and quirky,” tornadoes have “never fit neatly into the climate change narrative” of warming-induced extreme weather events, writes the Washington Post.
Rather, “twisters seem to follow a boom-and-bust cycle.” While 2018 was quiet, 2008 and 2011 were “off the charts, each with more than 2,000 reported tornadoes.” So far in 2019, there have been nearly 1,000.
Tornadoes themselves “emerge from a time-tested atmospheric recipe,” the Post writes. “Moist air flowing north into the Midwest and the Southeast U.S. gets topped by a layer of hot, dry air from the desert southwest,” which is itself topped by another layer of cold air. All this atmospheric layering ultimately leads to the formation of massively stormy cumulonimbus clouds rising “tens of thousands of feet.” Add rotational winds, and you have a tornado.
While May is always peak tornado season, the pummeling the Midwest has received this spring owes to a jet stream that, rather than flowing reliably in a relatively straight west-to-east pattern, has become stuck in a “roller coaster” formation, trapping uncharacteristically cold, wet weather in the West and unprecedented heat in the Southeast. Between the two regions, the Post notes, “lies a huge swath of the United States that’s primed for tornadoes.”
Jennifer Francis, senior scientist at the Woods Hole Research Center in Massachusetts, said the jet stream is stuck “all the way from the middle of the Pacific Ocean to the Atlantic,” an event whose possible connection to a rapidly-warming Arctic is “consistent with” climate change.
The attribution science connecting individual severe weather events to climate change is in its infancy, the Post says. “If there’s a [climate] signal in the ambiguous tornado data, it’s that there’s more variability from year to year in the number of tornadoes. ‘Expect the unexpected’ seems to be the meteorological conclusion.”
As to the latest forecast: experts say the jet stream is “edging back towards normalcy,” and June should bring calmer skies.