An unusual combination of atmospheric processes and accelerated changes in the Arctic explains the magnitude of the winter storm that is exposing nearly 200 million people to temperatures as low as 50 degrees below zero.
The United States is experiencing one of the most intense and widespread cold waves in recent decades, with nearly 30 states under continuous alerts for snow, freezing rain, and extreme sub-zero temperatures.
The phenomenon advanced from the Rocky Mountains and the Great Plains to the East Coast, with direct impacts on transportation, power supply, and the daily lives of millions of people. At first glance, the scene seems to contradict a widely documented climate trend: winters have become warmer on average.
However, climate science offers precise clues to understanding why such a severe cold snap was possible on a planet that is recording temperature records year after year.
The answer does not rest on a single cause, but on the superposition of processes acting at different scales, from the Arctic to the jet stream that governs the climate of the mid-latitudes.
Meteorology and
El estiramiento del vórtice polar permitió que aire ártico avanzara hacia el sur y provocara condiciones invernales severas en gran parte del país (Joel Bissell/Kalamazoo Gazette via AP) global climate specialists agree that this storm does not contradict global warming, but rather fits within an altered atmospheric system that is more variable and with less frequent but potentially more intense extremes.
1-A distorted and southward-shifted polar vortex
The first key scientific fact lies in the behavior of the polar vortex. This system consists of a vast wall of winds that rotates around the North Pole and keeps the coldest air confined to the high latitudes during the boreal winter.
When its structure remains compact and stable, extreme cold rarely reaches densely populated regions. This time, the opposite occurred.
A series of deep undulations in the upper atmosphere stretched the vortex and allowed lobes of Arctic air to descend into the United States. This displacement explained the arrival of temperatures well below zero in areas that do not usually experience such persistent cold. The US National Weather Service warned of “potentially life-threatening cold air,” a phrase that summarizes the health risks associated with hypothermia and frostbite.
The magnitude of the event surprised even experts accustomed to monitoring winter storms. “The fact that we have approximately 2,900 kilometers of uninterrupted weather alerts from Arizona to the East Coast demonstrates the magnitude of this storm,” Matthew Cappucci, a meteorologist at MyRadar, told PBS, the American public television network.
This geographical continuity reflects a large-scale atmospheric pattern, more typical of winters from past decades than of recent climate patterns.
2-A Warmer Arctic Weakens Winter Stability
The second scientific finding points to the remote origin of this polar vortex: the Arctic. Temperatures in that region have increased at a much faster rate than the global average, with an accelerated loss of sea ice. This change has altered the thermal contrasts that sustain the atmospheric circulation of the Northern Hemisphere.
Judah Cohen, a research scientist at MIT and a specialist in winter climate, explained that the reduction of ice in seas such as the Barents and Kara played a central role in the increased variability of the polar vortex.
“There is clearly a strong relationship between stretched vortex events and extreme winter weather here in the US,” he said. According to his analysis, a warmer Arctic added energy to the system and facilitated configurations that allow cold air to escape southward.
The records support this interpretation. Arctic sea ice reached its lowest extent for this time of year, a fact that scientists consider relevant for anticipating winters with more erratic behavior.
Although not all extreme cold events can be directly attributed to climate change, Cohen summarized the scenario with a clear metaphor.
“I’m not saying that any particular weather event is due to climate change, but I do think the dice have been loaded here,” he said.
3-More Moisture Available for More Intense Storms
The third scientific fact helps explain why this polar vortex not only brought cold but also intense snowfall and extensive ice formations. A warmer atmosphere retains more water vapor. When polar air advances toward mid-latitudes and encounters this moisture, the result can be a large-scale winter storm.
In this episode, the clash between the Arctic air mass and the warm, humid air from the Gulf of Mexico and the Pacific created ideal conditions for snow and freezing rain. Southern states, less accustomed to these types of phenomena, faced frozen roads and power lines covered in ice.
The U.S. National Weather Service warned of accumulations capable of causing widespread power outages and significant damage to trees and infrastructure. "These sub-zero temperatures will pose a deadly risk of hypothermia and frostbite to exposed skin," the agency warned.
This message reflects how the impact of these storms depends not only on the cold but on the combination of variables that amplify their effects.
4-A warmer climate with less frequent but more disruptive extremes
The fourth scientific fact introduces an apparent paradox. In the long term, cold waves in North America have become less frequent and less extreme.
Data shows that warm temperature records have far outnumbered cold records in recent decades, even during the winter. In cities like Minneapolis and Cleveland, the average annual minimum temperature has risen more than six degrees Celsius since the 1970s.
This sustained warming reduces the likelihood of episodes like the current one, but it doesn't eliminate them. When they do occur, they can be more disruptive because societies and infrastructure have adapted to a less severe climate. Power grids, transportation systems, and homes face greater risks from cold that is no longer part of the usual experience.
Jennifer Francis, a researcher at the Woodwell Climate Research Center, underscored this complexity by noting that global warming does not act in a linear fashion. “Although global warming is causing warmer winters overall, severe winter weather events are still possible—and perhaps even more likely—because warming is not the only consequence of human-caused climate change.
Other factors that set the stage for extreme winter weather are on the rise, and many of them are at play this week,” he said.
5-A storm that reflects profound changes in the climate system
The fifth scientific point connects all the previous ones and offers an overall perspective. The current climate system shows greater variability, with patterns that deviate from the stability that characterized much of the 20th century.
Changes in the jet stream, in the distribution of sea ice, and in atmospheric circulation favor extreme weather patterns, both hot and cold.
The winter storm sweeping across the United States has exposed this new dynamic. Nearly 200 million people were under some type of weather alert, with snowfall exceeding 30 centimeters in large regions and wind chill temperatures dropping below -46 degrees Celsius in the northern plains.
At the same time, major cities are facing massive flight cancellations and warnings from transportation authorities.
For scientists, the challenge is to communicate that these events do not contradict global warming, but rather are part of a more complex and less predictable climate.
Amy Butler, an atmospheric scientist at NOAA, explained that there is still uncertainty about how the polar vortex will evolve in the future. “There are many factors that can alter the intensity of the polar vortex,” she said, including sea ice and the warming of the upper layers of the atmosphere.
The underlying trend, however, is clear. Extreme cold spells are decreasing in frequency, but snow and ice remain present and pose significant challenges. In the western United States, for example, snowmelt provides a large portion of the water supply, adding another layer of complexity to the changes in winter storms.
The current polar vortex will serve as a reminder that climate change doesn't eliminate winter, but rather transforms it. In a context of rising global temperatures, extreme cold becomes less common, but when it does occur, it does so in an environment charged with energy and moisture, leading to amplified impacts.
Understanding these five key scientific points is essential for anticipating risks, adapting infrastructure, and recognizing that global warming doesn't mean a uniform climate, but rather an increasingly challenging one.
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