Climate Signals Summary: There are three things to consider when squaring this extreme winter weather with climate change: cold weather doesn’t cancel out decades of warming; rapid Arctic warming is associated with disruptive winter weather in the US; and cold events aren’t as cold as they would have been without climate change.
Article Excerpt: Scientists say global warming – specifically the rapid warming of the Arctic – is a possible, if not likely, culprit in the extreme weather.
Historically, frigid temperatures have typically been contained within the Arctic by a jet stream circling the polar region. In fact, along with the spinning of the planet, it’s the contrast in temperatures and atmospheric pressures between the Arctic and lower latitudes that results in the winds.
But as the Arctic has warmed more than twice as fast as the global average over the last three decades, that contrast can be less pronounced, said Paul Beckwith, a climate system scientist in Ottawa. That could cause the polar jet stream to slow down and meander, so that it carries more warmer air toward the pole and frigid air further south, he said.
“What we’re seeing this year is an extreme example of what happens when the jet stream trough goes really deep southward,” Beckwith said.
“I think it’s a rock-solid case,” he said. But “it might take a bit of time for the science to catch up and find all the details” to prove it.
Others caution that it’s still too early to draw conclusions. The theory “remains speculative, and it is the reporting of it as fact that is not justified,” climate scientist Geoffrey Vallis at the University of Exeter tweeted on Tuesday. “It may be true, but perhaps more likely not.”