"The data is clear: Rising global temperatures mean
winters are getting milder, on average, and the sort of
record-setting cold that spanned the country Friday is
becoming rarer. But at the same time, global warming
may be altering atmospheric patterns and pushing harsh
outbreaks of polar air to normally moderate climates,
according to scientists who are actively debating the
link.
Drastic changes in the Arctic, which is warming faster
than anywhere else on Earth, are at the center of the
discussion. Shifts in Arctic ice and snow cover are
triggering atmospheric patterns that allow polar air to
spread southward more often, according to recent
research.
“We’ve seen the same situation basically the last three
years in a row,” said Jennifer Francis, senior
scientist at the Woodwell Climate Research Center in
Massachusetts. “Here we go again.”
But understanding any link between planetary warming
and extreme cold remains a work in progress. Many
climate scientists still emphasize that even if frigid
air escapes the Arctic more often, that air will
nonetheless become milder over time.
More than a million without power as frigid air
overtakes eastern U.S.
The debate started with a research paper Francis co-
authored in 2012. It gets revived whenever an extreme-
cold event creates headlines, such as in 2021, when
Texas’s energy grid was overwhelmed by a storm that
killed 246 people.
Francis’s research hypothesized that Arctic warming was
reducing the contrast between polar and tropical
temperatures, weakening the jet stream, a band of
strong winds in the upper atmosphere that helps guide
weather patterns. A weaker jet stream would allow
weather systems to more easily swing from the Arctic
down into mid-latitude regions that typically have
temperate climates.
Since then, observations of jet stream patterns have
not confirmed the hypothesis, said Daniel Swain, a
climate scientist at UCLA. But the research inspired a
flurry of follow-up studies that Swain expects will
eventually clarify a link between climate change and
cold-weather outbreaks.
“We’re 10 years into this conversation and there’s
still a lot of mixed feelings in the scientific
community, though there is some tantalizing evidence
that there is some ‘there’ there,” said Swain, who
works at UCLA’s Institute of the Environment and
Sustainability.
A 2021 study published in the journal Science is one
new point of debate. The research explains what author
Judah Cohen called “a physical foundation” linking
Arctic warming and changes in atmospheric patterns.
It focuses on the polar vortex, an area of low pressure
typically parked over the North Pole and surrounded by
a band of fast-flowing air. Cohen likens it to a
spinning top — when the polar vortex is strong, that
band of air spins in a tight circle.
Increasingly often, Cohen found, the polar vortex
weakens like a wobbling top. That gives the circulating
air a more oblong, extended shape and encourages bursts
of Arctic air to spread southward.
While the polar vortex took on that stretched shape for
about 10 days a year in 1980, in recent years, it has
been occurring more than twice as often, said Cohen,
director of seasonal forecasting at Atmospheric and
Environmental Research.
The research links that to changes in the climate
around the Arctic: In the Barents and Kara seas north
of Russia and Scandinavia, the waters have warmed and
ice has melted, whereas in Siberia, there’s been a
cooling trend from increases in snowfall induced by
climate change.
Some scientists say that a longer and more thorough
record of data is needed to back up Cohen’s research
and that there isn’t enough evidence to blame Arctic
warming for cold outbreaks at lower latitudes.
The surprising reasons parts of Earth are warming more
slowly
Swain predicted that scientists will make sense of the
atmospheric dynamics but that it could take years.
“It’s one of the most complicated topics in climate
science,” Swain said.
In the meantime, researchers are confident that cold
extremes will follow larger global trends and gradually
get warmer, though they still will have significant
impacts on places unaccustomed to the cold.
“We’re going to break a lot of records this week, for
sure,” Francis said. “The likelihood of breaking cold
records is decreasing, and we see that in the data.”
And Cohen said data suggests that relief from the cold
across the United States is near: Weather models agree
that the polar vortex is going to snap back from its
oblong shape by early January, trapping the most frigid
air around the North Pole once again."
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