During the holiday period of December 2022, Americans who were dreaming of a white Christmas got more than they bargained for. Sudden, intense, heavy snowfall, and freezing temperatures swiftly grounded parts of North America to a halt.
In Casper, Wyoming, temperatures plummeted as low as –72.2°F (–41°C), a level not seen since 1931.
Many climate scientists believe this kind of extreme, unpredictable weather—known as climate volatility, but sometimes called “climate whiplash”—is expected to become more common as global warming transforms the climate system.
The speed with which temperatures fell in the United States may be an example: Between December 21–25, a powerful arctic front swept into the northern US. Some 200 million people came under a winter storm advisory or warning, and a million people lost electrical power, according to a 2023 climate report from the National Oceanic and Atmospheric Administration (NOAA).
What’s causing the whiplash? While scientists have a good idea about the interaction between climate change and extreme weather events, there are some key puzzles yet to be solved.
The Polar Vortex
Much of the discussion swirling around the cold weather that struck North America involved the polar vortex. This mass of cold wind surrounds the North Pole and intensifies during the winter as the sun’s heat moves away.
Scientists think that fluctuations in the polar vortex (due to a warming climate) may be a principal cause of increasing extreme weather events. Contrary to many news reports, the polar vortex itself doesn’t descend to bring down cold air. It is situated in the stratosphere on both poles, roughly fifteen to fifty kilometers (nine to thirty-one miles) above the Earth’s surface—far from the weather experienced on the ground.
Yet as the vortex becomes unstable, it affects the jet stream below, causing fluctuations that can open a route for cold polar air to move into.
Climate volatility has increased significantly over the last six decades. For instance, in Europe, tree ring data show the jet stream has become more variable and extreme. “The timing of the changes suggests that it’s anthropogenic,” Valerie Trouet, a climate scientist at the University of Arizona, told Yale 360.
The relationship between the vortex and the jet stream appears to be reciprocal, too. The Earth’s atmosphere flows around the planet like a fluid, meaning weather changes at lower altitudes—and variations in the jet stream—can have knock-on effects to the vortex, too.
The Earth’s atmosphere flows around the planet like a fluid, meaning weather changes at lower altitudes can have knock-on effects to the polar vortex, too.
“Like an elastic band, the vortex usually rebounds back to its normal shape and size, maintaining its strong winds and low temperatures,” writes Zachary Lawrence, a Research Scientist at the University of Colorado Boulder, and Amy Butler, Chemistry & Climate Processes Research Scientist at the National Oceanic and Atmospheric Administration, in The Conversation.
But occasionally these variations knock the vortex off balance, leading to structural breakdown. This is thought to have happened over the 2022 holiday period: a sudden violent warming tore the polar vortex apart, releasing weather chaos.
Extreme Warm Weather
Meanwhile, in Europe, climate whiplash presented itself in the form of unseasonably warm weather. Eight European countries experienced the hottest January day on record (January 1, 2023), according to data analyzed by professional climatologist Maximiliano Herrera. “We can regard this as the most extreme [climate] event in European history,” Herrera told The Guardian.
While North America was paralyzed by a cold chill, Budapest experienced its warmest-ever Christmas Eve, according to Reuters. In Bilbao, Spain, temperatures rose to 25.1°C (about 77.1°F) in early January, over 10°C (or 18°F) above the average for this time of year. The causes of this abnormally warm period are unknown, though scientists suggest warming sea surface temperatures could be to blame.
One possible cause for the unusually warm weather was a mass of hot air passing over from Africa—something that has been attributed to the weakening polar vortex. “In December, we saw an elongation and weakening of the stratospheric polar vortex in the Arctic,” said Judah Cohen, a visiting scientist at the Massachusetts Institute of Technology. Cohen's research suggests that stretches in the polar vortex have grown increasingly common over the last four decades.
A Confluence of Tornadoes
It’s not just temperatures that are experiencing abnormal swings. Another phenomenon is happening in the center of North America, in a region stretching from Texas to Wisconsin known as Tornado Alley.
This well-known tornado hotspot appears to be moving. Locals in this valley are familiar with destruction, but it appears to be spreading to their neighboring states in the Southeast: Tornadoes are hitting states like Alabama, Mississippi, Tennessee and Kentucky. On December 10, 2021, tornadoes, at least one twisting at speeds up to 190 mph, rampaged through several Midwestern and Southern states. Many of the 93 people killed that day were in Mayfield, Kentucky.
This apparent shift in tornado activity could be due to climate change, which is expected to bring more frequent and severe extreme weather. There were 1,329 preliminary tornado reports across North America in 2022, above the average of 1,225.1 between 1991 and 2020. (NOAA National Centers for Environmental Information, Monthly Tornadoes Report for Annual 2022, published online January 2023).
Scientists suspect that climate change raises the potential for thunderstorms in the Southeast, which could potentially increase tornado formation.
Tornado Alley steals most of the limelight from Dixie Alley, a lesser-known tornado region stretching through Louisiana, Arkansas, Tennessee, Kentucky, Alabama, and Georgia. "It seems to me that there really is a perception that people think the tornadoes only happened in Tornado Alley," Harold Brooks, a senior scientist at the National Severe Storms Laboratory in Oklahoma, told WFAA.
Scientists suspect that climate change raises the potential for thunderstorms in the Southeast, which could potentially increase tornado formation.
Scientists use a metric called the Convective Available Potential Energy (CAPE) to measure thunderstorm severity. Some parts of the United States have seen between ten and fifteen more days with high CAPE values than tracked before, in both spring and summer. This suggests the potential for thunderstorms—and therefore tornadoes—is rising.
How to Predict, Prepare, and Survive
Scientists around the world are working on further understanding extreme weather. But predicting extreme events, such as the sudden warming of the stratosphere this winter, is notoriously difficult.
Even with a reduction—or immediate cessation—in carbon emissions, considered by scientists to be the main driver of climate change, extreme weather is still predicted to worsen.
Future weather prediction differs depending on regions and at best is thought to last a maximum of two weeks or less.
Even with a reduction—or immediate cessation—in carbon emissions, considered by scientists to be the main driver of climate change, extreme weather is still predicted to worsen.
Many communities around the world are preparing to mitigate some of the more destructive impacts.
Cities across North America are investing in new infrastructure capable of withstanding extreme weather. Baltimore and Minneapolis, for example, are investing in the idea of “Resilience Hubs,” which seek to use local networks to boost resources and services both before and after extreme floods, hurricanes, or tornadoes.
Sadly, many of the hardest-hit countries from the effects of climate change are those without the resources to deal with the coming impacts. Afghanistan, for example, ravaged by decades of conflict and instability, is seeing soaring summer temperatures and increasingly bitter winters. Between 1950 and 2010, temperatures there rose by 3.24°F (1.8°C), and the worst-case scenarios suggest temperatures could rise by a further 10.8°F (6°C) by the end of the century.
Coastal countries like Bangladesh are facing sea-level rise on an unprecedented scale. Between 2000 and 2019, extreme weather events cost Bangladesh $3.72 billion.
Not all hope is lost. At COP27 in November 2022, a “Loss and Damage” fund was established for vulnerable communities. If this succeeds in transferring money to those countries who need it most, they can start preparing for the increasingly volatile weather the world is expected to face. But as the world continues to warm, the future climate is looking increasingly unstable.
*Richard Kemeny writes about archaeology, marine biology, oceanography, ecology, technology, and the environment.