Bitter cold has gripped the United States with its icy fingers, ensuring a bone-chilling start to the new year. The storm, dubbed Winter Storm Blair, triggered winter weather warnings for more than 60 million people this week across a swath from Illinois to New Jersey.

The ongoing storm has already dropped up to 30cm of snow in some cities and killed at least six people. As of Monday morning, nearly 300,000 utility customers in the states of Virginia, Kentucky and Illinois had lost power. The storm is expected to bring more snow through Tuesday and frigid weather well into next week. Subfreezing temperatures are expected to reach Texas and Florida and could bring the first snow to Disney World in nearly 50 years.

Winter Storm Blair is the harbinger of one of the hottest years on record, and although it’s freezing North America over, its origins actually lie in the Arctic.

There is evidence that due to climate change, cold Arctic air is more likely to break containment in the planet’s northernmost regions and escape south, causing freezing temperatures in lower latitudes such as the continental United States.

It may seem counterintuitive, but the fact that global average temperatures are rising does not rule out cold spells and could make them worse in some Arctic-driven storms. Scientists are studying the mechanisms that link humanity’s insatiable appetite for fossil fuels, the Far North and storms like Blair. They reveal a complicated picture that shows some of the most profound impacts of climate change are occurring in the coldest parts of the planet and during the coolest times of the year.

As average temperatures rise rapidly, their impacts are manifesting themselves in surprising ways, but with more observations and better forecasting tools, storms like Blair need not be as deadly and destructive.

How North Pole warming could bring a winter storm to your commute

There are a few key mechanisms behind cold showers like Winter Storm Blair. One of these is the polar vortex, a rotating band of strong, cold wind that is usually limited to 10 to 30 miles above the North Pole. The polar vortex increases in strength in winter and tends to remain circular. However, due to waves in the atmosphere, it can occasionally split into multiple vortices or deform into an elongated shape that extends beyond the Arctic.

The other factor is a jet stream known as a polar jet. This is a band of air that blows from west to east at altitudes between 4 and 8 miles above the Earth’s surface at speeds of up to 275 miles per hour.

When the polar jet is strong, it forms a clearly defined ring around the Arctic, holding the icy air in place. As it weakens, it wobbles and, when viewed directly above the North Pole, forms the shape of a flower or shamrock. Within these lobes, cold Arctic air pours over landmasses such as Asia and North America.

Disturbances in the polar vortex can be accompanied by deviations in the polar jet, causing even more cold air to travel even further south.

However, such floods have also occurred naturally in the Arctic in the past. What role does global warming play? Jennifer Francis, a senior scientist at the Woodwell Climate Research Center, co-authored a review article published in December that looks at the body of research attempting to answer this question.

The crucial fact is that while Earth is warming on average, the Arctic is warming up to four times faster than the planet as a whole, a phenomenon called Arctic amplification. This has important knock-on effects.

For one thing, a warmer Arctic means that there is a weaker temperature gradient between the Arctic and surrounding regions. Francis explained that the stark difference between arctic and subarctic temperatures primarily drives the polar jet. So the more the north feels like the rest of the planet, the weaker the jet will be, increasing the chances of cold air snaking across the Northern Hemisphere – and causing even more extreme winter storms like Blair.

At the same time, the planet’s oceans have warmed to extraordinary levels in recent years, and some of the planet’s waters, such as the North Pacific, remain unusually mild. This pushes tropical air further north and bends the jet stream north over the Pacific and south over North America.

The loss of sea ice in regions of the Arctic due to warming also has the potential to alter the polar vortex, allowing cooler air to move further south.

Francis and her co-authors acknowledge that there are major uncertainties in accurately quantifying how much human-caused warming influences periods of severe cold. It’s also unclear exactly how this will continue as the planet continues to warm.

The effects of warming do not scale linearly, particularly in the Arctic, and there are many complicated feedback mechanisms that researchers are still trying to unravel. For example, melting reflective sea ice results in a dark, heat-absorbing ocean that can melt even more ice.

There are also researchers who are not convinced that climate change has played a discernible role in recent cold snaps or that they will become more frequent as global average temperatures rise. A study published last year using climate models and historical records found that the main way we can tell about human influence on sudden, severe cold spells is that they are no longer as cold as they used to be. The paper found that extreme cold temperatures in North America are warming faster than average winter temperatures.

Scientists generally agree that winters are getting warmer on average and are warming faster than summers. However, dangerous winter weather from the Arctic still occasionally occurs. “Although the Arctic is warming, it will still be cold in winter for a very long time because there will be no sunshine for six months,” Francis said in an email. “There will still be plenty of cold air there to support cold spells if the jet stream dips sharply to the south.”

Researchers also emphasize that the dangers of severe cold spells come not just from the temperature, but also from how well people are prepared to deal with them. A cold snap can prove deadly if it hits an area where such severe cold snaps rarely occur, such as 2021’s Winter Storm Uri, which iced Texas and killed 246 people. The threat is amplified when there is little warning.

On that front, there’s a little bit of warm comfort in this icy weather. Forecasters are better able to recognize the warning signs of cold snaps. Scientists discovered last month that the polar vortex was increasing in strength, and forecasters have been warning since last week that severe cold and snow are ahead across much of the United States. With further advances in data collection and new AI forecasting tools, we will likely be able to see the bitter cold more clearly and from further away in the future.