Winter Storm Blair: How rising temperatures change cold extremes

Bitter cold has lashed its icy fingers across the US, bringing a chilly start to the new year. Dubbed Winter Storm Blair, The storm has triggered winter weather warnings for more than 60 million people this week in a swath from Illinois to New Jersey.

The ongoing storm already has up to a foot of snow fell in some cities and killed at least six people. From Monday morning, almost 300,000 utility customers had lost power across states including Virginia, Kentucky and Illinois. The storm is expected to deliver more snow by Tuesday and freezing weather well into next week. Freezing temperatures are poised to reach as far south as Texas and Florida and could deliver first snow for Disney World in nearly 50 years.

Winter Storm Blair comes as a bookend to one of the warmest years on record, and while it’s freezing North America, its origins actually lie in the Arctic.

There is evidence that, due to climate change, cold Arctic air may be more likely to break confinement in the northernmost parts of the planet and escape south, bringing cold temperatures to lower latitudes like the continental United States.

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

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

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

There are a few key mechanisms behind chills like Winter Storm Blair. One is polar vortexa swirling band of strong, cold winds usually confined to 10 to 30 miles above the North Pole. The polar vortex picks up strength during the winter and tends to remain circular, but due to waves in the atmosphereit can occasionally split into multiple eddies or deform into an elongated shape that reaches beyond the Arctic.

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

When the polar jet is strong, it forms a well-defined ring around the Arctic, keeping the icy air in place. As it weakens, it wobbles and forms a flower or clover shape when seen directly over the North Pole. Within these lobes, cold arctic air flows over land masses such as Asia and North America.

Disturbances in the polar vortex can combine with deviations in the polar jet, leading to more cold air reaching even further south.

However, such arctic spills have occurred naturally in the past. How does global warming play a role? Jennifer Francissenior researcher at the Woodwell Climate Research Center, co-author of a review article published in December, looking at the research that attempts to answer this question.

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

One is that a warmer Arctic means that there is a weaker temperature gradient between the Arctic and its surrounding areas. Francis explained that the steep difference between arctic and subarctic temperatures is what drives the polar jet in the first place, so as the north begins to feel more like the rest of the planet, the jet weakens, making its cold air more likely. to meander across the Northern Hemisphere – causing 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, have continued to unusual balm. It 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 areas of the Arctic due to warming also has the potential to reshape the polar vortex in ways that lead to cooler air reaching further south.

Francis and her co-authors acknowledge that there is a lot of uncertainty in quantifying exactly how much anthropogenic warming affects periods of severe cold. It’s also unclear exactly how this will play out as the planet continues to warm.

The effects of warming do not scale linearly, especially in the Arctic, and there are a lot of complicated feedback mechanisms that scientists are still trying to map. Melting reflective sea ice, for example, gives way to a dark, heat-absorbing ocean that can further melt more ice.

There are also scientists who are not convinced that climate change has had a clear role in recent cold snaps, or that they will become more common as the global average temperature rises. A study published last year using climate models and historical records, reported that the main way we can see human influence on sudden periods of severe cold is that they are not as cold as they used to be. The paper found that extreme cold is warming faster than average winter temperatures in North America.

Scientists generally agree that winters are warming on average and are heats up faster than in summer. Despite this, dangerous winter weather will still occasionally spill over into the Arctic. “Even if the Arctic warms, it will still be cold in the winter for a very long time because it doesn’t have sunshine for six straight months,” Francis said in an email. “There will still be plenty of cold air there to feed into cold spells when the jet stream takes a big dip south.”

Scientists also highlight that the dangers of severe cold waves come not only from the temperature, but from how well people are prepared to cope with them. A cold can prove deadly if it strikes an area that rarely experiences chills as severe as when Winter Storm Uri froze Texas in 2021 and killed 246 people. The threat is amplified when there is little advance warning.

On this front, there is a bit of warm comfort in this icy weather. Forecasters are getting a better handle on the warning signs of cold spells. Scientists discovered polar vortex total strength last monthand meteorologists were warning since last week that intense cold and snow are in store for large parts 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 sharply in the future and further away.