Why Global Warming Means a Snowier Eurasia
It may seem like a paradox, but a hotter Arctic can lead to colder winters across Eurasia.
Snow in Russia. Image: Maarten Takens/Russia
As winter approaches, it's time to brace ourselves for a particular type of dad joke: If it's called global warming, why is it so damn cold? Eye-rolling chuckles aside, new research sheds light on one of the classic problems in climate modeling: the fact that, despite higher average global air temperatures, some regions have been experiencing far more severe winters than usual.
In this case, a team of Japanese researchers looked at mid-latitude Eurasia (think southern Russia, northern China, Kazakhstan, and their neighbors), which has seen a boom in snowfall in recent decades. That trend has come despite a decline in winter sea ice in the Russian Arctic, which is due to generally warmer winters in that region.
According to the researchers, the decline in Arctic sea ice has actually fueled colder, more intense winters in central Eurasia.
"We successfully detected the signature of Eurasian cold winters excited by sea-ice decline in the Barents–Kara Sea, where a pronounced change has been observed during winters since 2004, based on a large ensemble of state-of-the-art atmospheric general circulation model (AGCM) simulations," they write in Nature Geoscience.
It seems confusing at first glance. Adding to the problem is the difficulty of modeling a connection between weather in the Barents and Kara Seas in northern Russia and weather at more southerly latitudes, which are separated by the bulk of Russia's own weather systems.
The above map, courtesy the Japanese team, compares observed weather data between high and low Arctic ice years. As you'd expect, low ice years had warmer temperatures in the Arctic (hence the warmer colors), but at the same time Eurasian weather was colder.
While the team tested other possibilities for why Eurasia has experienced snowier winters, they found that years in which the Barents-Kara Sea region was warmer, and Eurasia colder, "is more likely to be responsible for the increased frequency of severe winters in recent years."
They argue that this is due to weather patterns affecting the entire continent. As you can see in the above map, their models show that warm Arctic years produced an atmospheric wall locking cold weather into Eurasia. (Arrows show the direction of near-surface wind.)
"There are strong southerly surface wind anomalies over the Barents-Kara Seas (BKS), associated with the anticyclonic response in the warmer Arctic, colder Eurasia (WACE) model, which reinforces heat release from open water to the atmosphere, possibly acting to reduce sea ice in the BKS through transportation of sea ice from the coast," the authors wrote. "This suggests a positive feedback acting between sea-ice decline and the atmosphere, which may amplify the WACE response."
This type of atmospheric wall is reminiscent of the Ridiculously Resilient Ridge, a 2,000 mile long high pressure front that's locked cold Arctic weather out of California, worsening the states' three-year drought.
While the two observed weather patterns are unique on their own, they have both been connected to the warming climate. On a broad scale, they offer insight into how some counterintuitive weather we observe, like the colder winters we've also observed in the US, can still happen despite the globe on average being hotter.
The frequent occurrence of cold winters may be a temporary phenomenon in a transitional phase of eventual global warming
The Japanese team isn't the first to observe the anomaly, and their work lends further credence to the model of a warming Arctic and declining sea ice directly influencing colder winters in Eurasia. Naturally, the next question is whether or not Eurasia is doomed to more brutal winters forever.
"Given that the observed sea-ice decline largely reflects the global warming signature, and that it will continue to decline in the future, one might expect the frequency of cold winters to increase as well, by the mechanism presented above," the researchers write.
But that's perhaps not the case, as the warmer Arctic, cooler Eurasia conditions that produce a cross-continent atmospheric ridge may balance out if trends continue.
"The frequent occurrence of cold winters may be a temporary phenomenon in a transitional phase of eventual global warming, although projection uncertainty remains," the authors write.
In other words, this atmospheric phenomenon is happening now, but may not continue if overall global temperatures—and thus atmospheric conditions—continue to change. If anything, that represents the easiest answer to the "it's too cold out for global warming" quip: It's already difficult to model what's causing the weather, and it's even harder to predict what will influence it next.