Arctic climate change may not be making winter jet stream weird after all
New research is pouring cold water on once-hot theory
An influential, highly publicized theory — that a warming Arctic is causing more intense winter outbreaks of cold and snow in midlatitudes — is hitting resistance from an ongoing sequence of studies, including the most comprehensive polar modeling to date.
The idea, first put forth in a 2012 paper by Jennifer Francis, now at the Woodwell Climate Research Center, and Stephen Vavrus, at the University of Wisconsin at Madison, is that two well-established trends — Arctic amplification (intensified global warming at higher latitudes) and depleted sea ice — can force the polar jet stream to dip farther south, thus causing more intense bouts of winter weather than might have otherwise occurred.
From 2012: Shrinking Arctic ice and the wicked backlash on our weather
Over the past decade, this hypothesis sparked widespread public interest and scientific debate, as various high-profile cold waves and snow onslaughts hit North America and Eurasia, including a deadly, prolonged cold wave in Texas last February.
Winter temperatures over the past three decades have shown cooling in some areas of the northern midlatitudes, especially eastern Asia.
But the cooling has been far from ubiquitous and the Arctic-midlatitude link has been difficult to detect in simulations by global computer models. Instead, the models point more strongly toward the gradual, longer-term trend of milder midlatitude winters that one would expect in a human-warmed climate. (A separate line of research is addressing extremes during the summer, such as the unprecedented heat wave that struck the Pacific Northwest in June; see below.)
Some emerging work, not yet peer-reviewed, does reveal faint fingerprints of the Francis-Vavrus hypothesis in new simulations of Arctic and midlatitude winter climates, part of the Polar Amplification Model Intercomparison Project (PAMIP).
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