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AER Scientists Lead Review Article on the Relationship between Severe Winter Weather and Arctic Warmth

Lexington, Mass., January 13, 2020 — A new review article published in Nature Climate Change evaluates the contentious topic of whether severe winter weather in the United States, Europe, and Asia is sensitive to Arctic temperatures. The lead author is Dr. Judah Cohen, director of seasonal forecasting at AER, a Verisk (Nasdaq:VRSK) business.

Despite a warming planet, winter weather has remained surprisingly resilient across the midlatitudes of the Northern Hemisphere; and the winter weather headlines have often been about severe cold, heavy snowfalls, and the polar vortex. The unexpected frequency of severe winter weather was not projected by global climate models used to study climate change. It has been challenging for climate scientists to attribute the recent streak of cold, snowy winters to a particular cause.

One relatively novel idea has been to attribute severe winter weather across the United States, Europe, and Asia to Arctic amplification, the accelerated warming of the Arctic region at a rate 2 to 3 times faster than the rest of the globe. This accelerated Arctic warming was thought to be mostly due to rapidly melting Arctic sea ice. By contrast, the review article discusses why Arctic warming—which is faster than warming in all other regions—is complicated and not solely due to melting sea ice or snow cover. Increasing water vapor and clouds as well as the transport of heat and moisture from lower latitudes are all contributing to accelerated Arctic warming.

Much of the study discusses whether Arctic amplification, including decreasing Arctic sea ice and increasing Eurasian snow cover extent in the fall, is contributing to more severe winter weather across the midlatitudes. The idea is strongly debated among climate scientists and is considered controversial; therefore, until now, the topic has been considered lacking consensus. But the authors of the review article argue there are actually two divergent camps of consensus. 

One camp of consensus represents the observational studies that strongly argue that Arctic amplification is contributing to more severe winter weather. Low Arctic sea ice coupled with high Eurasian snow cover extent in the fall is ideally located for amplifying naturally occurring waves in the atmosphere that are most favorable for disrupting the polar vortex. Following polar vortex disruptions, the probability of severe winter weather in the United States, Europe, and Asia is greater for up to two months. During the past two winters, polar vortex disruptions unleashed record cold, the “bomb cyclone,” the “Beast from the East,” and other notable severe winter weather events across the United States, Europe, and Asia.

The other camp of consensus cites studies based on simulations of low Arctic sea ice using global climate models. The majority of those studies conclude that any observed increase in recent severe winter weather is likely due to chance and not Arctic amplification. In the simulations, sea ice loss does not result in more polar vortex disruptions and contributes to milder winter weather (not severe winter weather) across the United States, Europe, and Asia. Therefore, as the Arctic continues to experience profound changes, it will only contribute to milder winters across the Northern Hemisphere, according to these simulations.

“The publication of the paper is especially timely given the extreme winters of 2017/18 and 2018/19 in the U.S., including Alaska and Canada, with a record-warm Arctic and low sea ice especially near Alaska; record-breaking polar vortex disruptions; record-breaking cold; disruptive snowfalls, including severe ‘bomb cyclones’; and costly nor’easters,” said Cohen. “Correctly attributing these disruptive weather events to Arctic change or not should help society better anticipate these events and make the appropriate preparations. Also, properly contextualizing severe winter weather vis-à-vis Arctic change will better educate society to understand the full impacts of climate change.”

Cohen adds, “Realizing the dichotomy between observational and modeling studies will possibly break the impasse the climate community is experiencing in trying to understand the linkages between the Arctic and midlatitude weather.”

The research is funded by the National Science Foundation’s Division of Atmospheric and Geospace Sciences and Office of Polar Programs.

The study can be viewed here.

About Atmospheric and Environmental Research (AER)
Atmospheric and Environmental Research (AER) provides science-based solutions to global environmental challenges. AER’s internationally renowned scientists and software engineers collaborate to transform state-of-the-art predictive science and analytical tools into practical systems that address both civilian government and defense needs for geophysical understanding, computer simulation, and forecasting. AER customers include government agencies and national laboratories, aerospace and defense contractors, and academia. Areas of expertise comprise atmospheric and environmental science, air quality, remote sensing, meteorology, oceanography, space science, climate change, and software engineering. A Verisk (Nasdaq:VRSK) business, AER was established in 1977 and is headquartered in Lexington, Massachusetts. Visit

Brett Garrison
Edelman (for AER)

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