What's with the dangerous cold wave hitting much of the country?
The polar vortex and climate change connection explained
I live in Chicago, Ill. and Friday local news outlets issued warnings about sub-zero temperatures that were expected to hit over the weekend, continuing into this week. For example, Block Club Chicago warned: “Dangerous, 25-Below-Zero Cold Is Coming To Chicago This Weekend. Here’s How To Stay Safe.”
News flash: It is cold, very cold, where I live. A cold snap is being experienced across much of the Midwest. With climate change we’d expect winter weather patterns on average to be milder overall than historical trends. In fact, studying an earlier North American cold wave, the World Weather Attribution project finds that:
“Cold waves like this have decreased in intensity and frequency over the last century, but still occur.”
So, what is going on?
The polar vortex: A lay-person’s understanding
Short answer: The polar vortex isn’t staying in the Arctic like it should. The polar vortex is a low pressure area of cold air found at the poles. When it remains stable the the Arctic air stays put at northern latitudes.
The National Oceanic and Atmospheric Administration (NOAA) provides an uncomplicated explanation of the polar vortex in the following graphic:
For more on the polar vortex origins of the cold wave, the NOAA ENSO blog provides an overview of the “sudden stratospheric warming” we have been experiencing the effects of. A “stratospheric polar vortex” is a layer of the atmosphere located 5-30 miles above the surface of the Earth.
“ENSO” refers to “El Niño–Southern Oscillation” climatic patterns. I googled that so you don’t have to. But hey, I am a communications scholar, not an atmospheric scientist. That is why this section’s sub-header is a “lay-person’s understanding.”
On the ENSO blog, Michelle L'Heureux, a physical scientist with the NOAA Climate Prediction Center, writes:
“Sudden Stratospheric Warmings (SSWs) are occasions in the winter (~6 times per decade), when the polar stratosphere warms and the winds that normally flow from west to east around the pole weaken dramatically and even reverse direction, corresponding to a breakdown of the polar vortex.”
Research by Marlene Kretschmer and colleagues, published in the Bulletin of the American Meteorological Society, links weakened stratospheric polar vortexes to midlatitude cold extremes.
What’s the relationship to climate change?
Now that we understand what a polar vortex actually is, how does it relate to climate change anyway? The polar vortex staying put in the Arctic region depends on a robust polar jet stream keeping it contained. This weather pattern is dependent on the Earth’s rotation along with the “temperature difference between the warmer mid-latitudes and the polar region.”
With climate change, the Arctic is warming at a rate more than twice that of the global average, the phenomenon known as “Arctic amplification.” This warming has accelerated both the melting of Arctic sea ice and a decrease in spring and summer snow cover. As explained in a 2019 Carbon Brief article, this creates feedback loops:
“As Arctic sea ice diminishes, energy from the sun that would have been reflected away by the bright white ice is instead absorbed by the ocean, causing further warming. (Declining snow cover over Arctic land areas has the same effect.)”
This is an active area of climate research, with scientists testing several theories about the relationship between Arctic warming and weather extremes (including cold waves). Warmer temperatures in the Arctic “are likely throwing the polar vortex out of whack,” according to climatologist Judah Cohen.
In a 2020 review article, published in the journal Nature Climate Change Dr. Cohen and colleagues conclude that observational studies “overwhelmingly support” the idea that Arctic amplification is a factor in winter cold extremes, at the same time that most climate models do not show support for the theory that Arctic warming is influencing weather extremes in the midlatitudes.
As summarized by Live Science, Cohen and colleagues’ theory goes like this:
“[L]ess Arctic sea-ice cover means there's more moisture from the sea migrating inland over normally dry Siberia. This moisture then turns into snow, which reflects heat back into space and is making Siberia colder than normal; that in turn disrupts a thermal band in the troposphere extending over Eurasia. This discombobulated band can then destabilize the polar vortex, causing colder winters east of the Rockies in the U.S. and in Northern Europe and East Asia.”
The exact relationships between Arctic amplification, destabilized polar vortexes and climate change are being studied by climate scientists.
If you want to read deeper on the topic:
Carbon Brief. (2019, January 31). “Q&A: How is Arctic warming linked to the ‘polar vortex’ and other extreme weather?”
ENSO Blog. (2021, January 28). “On the sudden stratospheric warming and polar vortex of early 2021.”
Live Science. (2021, January 8). “Wandering polar vortex may cause a wild, snowy winter.”
For some sublime, awe-inspiring photography of the Arctic blast, check out Block Club Chicago.
How news outlets can make the climate connection
While the internet is still abuzz about Sunday’s Super Bowl LV (check out poet Amanda Gorman’s moving performance), news media have been reporting on the deep freeze.
Some news coverage is making the climate connection:
New York Times (2021, Jan. 30, updated Feb. 2): “Forecast: Wild Weather in a Warming World.”
National Geographic (2021, Jan. 11): “The polar vortex is coming—and raising the odds for intense winter weather.”
However, many news outlets are not explaining the nuances of climate change and polar vortex-influenced weather patterns. So, I’ll end this newsletter with some resources that journalists (and others!) can use to discuss climate change in extreme weather reporting.
The Covering Climate Now project, which is a collaboration of more than 400 news organizations with the goal to improve climate change news coverage, provides a reporting guide on extreme weather. They note that in humanizing stories it is “essential that the stories and voices we elevate are truly representative of those impacted.”
The American Association for the Advancement of Science (AAAS) SciLine’s provides an overview on “Cold Snaps and Climate Change.”
Climate Central provides data, graphics and other resources that can be tailored to specific media markets.
The bottom line is to emphasize the scientific consensus on human-caused climate change in communicating on the relationship to cold waves, as summarized by SciLine:
“Periodic bouts of extreme cold do not invalidate or weaken the overwhelming scientific evidence that human activities are warming the Earth to dangerous levels. Some evidence even suggests that human-induced global warming may be a driving force behind some winter cold snaps, and that Arctic warming in particular may ultimately increase the frequency and persistence of U.S. winter cold snaps.”
Thanks for reading! Until next week, stay warm, safe and help those in need in our communities. ❄️