While the ongoing spells of heatwaves and deadly wildfires have been linked to climate change, a new study hints that the recent spells of unusual winters in the northern hemisphere could be the result of Arctic warming. However, it does not indicate if similar trends will continue as the planet heats up further.
Researchers trying to understand a climate dichotomy in the view of global warming found that despite the rapid warming, which is a cardinal signature of global climate change especially in the Arctic, the United States and other regions of the northern hemisphere have experienced an increasingly frequent number of extremely cold winter weather over the past four decades. This is also the period when global warming became most marked.
The study published in the journal Science combines observations from models and satellites to demonstrate that “Arctic change is likely an important cause of a chain of processes dubbed as stratospheric polar vortex disruption, which ultimately results in periods of extreme cold”.
A CONTRASTING EVENT
Climate scientist and the lead author of the study Judah Cohen told Nature that conventional wisdom was that while global warming meant more heatwaves, it would definitely lead to fewer cold spells and snowfall. However, that might not be quite true.
Cohen said, “There are mechanisms by which climate change can contribute to more severe winter weather too.”
The most recent example of extreme winter weather was seen in January and February 2021 in Asia, Europe, and especially the United States.
Researchers maintained that the cold wave witnessed in the US’s Southern Plains in February 2021 might be exceptional in the observational record for the region based on the aggregate severity of the cold intensity, cold duration, and widespread disruptive snowfall. It fuelled the debate of whether climate change contributes to more severe winter weather.
Researchers believe that the loss of ice and snow cover in the Arctic Sea could be affecting the airstreams in the region with increasing episodes of the polar vortex. The polar vortex is a large area of low pressure and cold air surrounding both of the Earth’s poles.
According to the National Weather Service, “It always exists near the poles, but weakens in summer and strengthens in winter. The term ‘vortex’ refers to the counter-clockwise flow of air that helps keep the colder air near the Poles. Many times during winter in the northern hemisphere, the polar vortex will expand, sending cold air southward with the jet stream.”
The identification of the pattern can extend the warning time of cold extremes in Asia, Canada and the United States. “Preparing for only a decrease in severe winter weather can compound the human and economic cost when severe winter weather does occur,” the researchers said in the paper.
WHAT IS ARCTIC WARMING?
Over the last decade, researchers have observed changing trends across the Arctic with the temperature rising in the region faster than anyplace else on the globe. The rising temperature has led to a decline in summer sea ice in the region and the melting of ice in the Barents and Kara seas leading to increased snowfall over Siberia.
Meanwhile, one of the more robust signatures of global warming is accelerated Arctic warming, known as Arctic amplification. “It is both a response to and accelerator of Arctic sea ice decline, with the greatest losses observed in the BarentsKara and ChukchiBering Seas,” the paper said.
This amplification leads to increasing snowfall and snow cover at high latitudes, including across Eurasia during October through January. However, whether Arctic amplification could result in more severe winter weather, and how, is a matter of active debate, the researchers said.