Arctic Warm Spells Linked to Nasty Winter Weather on East Coast

As yet another powerful nor’easter slams New England with wind and snow, some scientists suggest that the storm—and other extreme winter weather—could be linked to climate change in the Arctic.

It’s a controversial idea, but one that has gained traction in the last few years. Some scientists suggest that Arctic warming can disrupt certain atmospheric circulation patterns in ways that may disrupt the weather elsewhere in the Northern Hemisphere. And new research this week may support the theory.

The study, published yesterday in Nature Communications, finds a strong correlation between unusually warm episodes in the Arctic and extreme winter weather in the eastern United States. The study includes more than 60 years of data on U.S. weather and Arctic climate conditions, from 1950 to 2016.

“Most of the studies on this work have been kind of just looking at a seasonal time scale,” said lead study author Judah Cohen, director of seasonal forecasting at the research and analytics group Atmospheric and Environmental Research. “We used daily data, and we had over 6,000 data points, so the statistical significance is much more robust.”

The Arctic is warming more rapidly than anywhere else on the planet. And sometimes the region experiences especially severe warming episodes, when temperatures temporarily skyrocket. One event just occurred near the end of last month, when Arctic temperatures soared more than 50 degrees Fahrenheit above their normal levels.

Scientists have also noticed that at the same time the Arctic is warming, there’s been a cooling trend in winter conditions throughout parts of North America and Eurasia—a surprise, given the ongoing influence of climate change. Numerous papers in the last few years have begun to suggest that the strange effect might be linked to the warming Arctic and the atmospheric disruptions some scientists believe it can cause.

Now, the new study finds that unusually warm episodes in the Arctic coincide with periods of extreme winter weather in the United States, pretty much everywhere east of the Rocky Mountains and especially on the East Coast.

The research “provides additional compelling evidence for the storyline that [the authors] have been developing for years,” climate scientist Charles Greene of Cornell University said in an emailed comment. “Most importantly, it demonstrates that the Arctic does play an important role in the development of extreme winter weather events in certain regions of the mid-latitudes and that everything cannot be explained only by what happens in the tropics, important as those regions are in climate-driven weather phenomena.”

The study doesn’t definitively prove that the warming events are the cause behind the weather—it only demonstrates a correlation, that the two tend to occur hand in hand. But there are some reasons to believe that the new research supports the theory, Cohen noted.

The researchers demonstrated that the correlation only exists when Arctic warming events occur first and extreme weather follows afterward. It doesn’t occur in reverse. This at least rules out the idea that weather in the United States could be influencing the climate in the Arctic, as opposed to the other way around, Cohen noted.

Without direct proof of causation, some researchers may suggest that there’s some other external event going on, separate from both the U.S. weather and the Arctic warming, that may be influencing both. But Cohen remains among the group of scientists who contend that it’s the Arctic warming that’s changing weather patterns in the Northern Hemisphere.

Some studies have indicated that rapid warming in the Arctic changes the flow of air between the North Pole and the lower latitudes, disrupting major air currents in the process. Jennifer Francis, one of the new study’s co-authors, has published multiple papers finding that a warming Arctic disrupts the flow of the jet stream. Other research suggests that the Arctic climate may similarly disrupt the polar vortex, a mass of cold air circulating in the Arctic, which has a known influence on winter weather in the Northern Hemisphere.

The polar vortex just experienced a major disruption at the end of February, actually splitting into two pieces, following the stunning warming event in the Arctic. A spree of unusual winter conditions followed, including a vicious cold snap in Europe and a series of winter storms in the United States. The latest is currently bombarding the East Coast.

The study’s authors suggest the eastern United States should get used to these kinds of events—as the Arctic continues to rapidly warm, they believe these kinds of events will occur more frequently. Still, some scientists urge caution. The link between Arctic warming and weather in the lower latitudes has been contested by some researchers, largely because of mixed results among modeling studies. Some models indicate that the connection is weak or may not exist at all.

Xiangdong Zhang of the University of Alaska, Fairbanks, said “comprehensive study” is still needed to establish the definitive causes behind the correlation demonstrated in the new paper. And he added that disturbances in the polar vortex, like the one that occurred in February, clearly influence the weather in the United States—but “what caused the polar vortex shift, in particular shift to a particular direction, is still an open question,” he said in an email.

Cohen suggested that the models themselves contain flaws that prevent them from accurately simulating the processes he and his colleagues believe are occurring. He said he’s begun using these ideas about the Arctic linkages in his own weather forecasting and believes the forecasts have become more accurate as a result.

“I do believe that to use an idea to improve predictability should be persuasive,” he said.

Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net.
https://www.scientificamerican.com/article/arctic-warm-spells-linked-to-nasty-winter-weather-on-east-coast/
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