Washington (United States) (AFP) – Meteorologists detected an early and unprecedented disturbance of the polar vortex, which increases the risk of cold waves throughout the northern hemisphere, although uncertainty persists about what triggered this phenomenon.
First modification: 06/11/2026 - 22:11
The polar vortex is a vast system of cold, low-pressure air that normally circulates from west to east high above the Arctic.
It usually strengthens during the fall and reaches its maximum around January. It can weaken in the second half of winter, usually between January and March, causing extremely cold air to spread southwards, reaching Europe, North America and Asia.
But scientists say the vortex is already weakening in early November.
"To our knowledge, this is the earliest disturbance of the stratospheric vortex that has been observed," Tim Stockdale and Frederic Vitart of the European Center for Medium-Range Weather Forecasts told AFP.
Judah Cohen, a climatologist at the Massachusetts Institute of Technology, explained that an alteration of the vortex is seen from below.
Large atmospheric waves in the lower layer of the atmosphere, the troposphere, known as Rossby waves, can rise, and a large enough rise into the polar stratosphere triggers rapid warming known as sudden stratospheric warming.
"That really increases the likelihood of cold air surges in the latitudes where most of the densely populated centers of the northern hemisphere are located: the United States, Europe and East Asia," Cohen told AFP.
Scientists believe that this phenomenon may be associated with this year's El Niño, one of the most intense ever recorded.
El Niño raises Pacific Ocean surface temperatures and alters wind and precipitation patterns around the planet.
According to Stockdale and Vitart, it is not yet known why this disturbance of the polar vortex occurred so early.
But they agreed that El Niño "could have been a factor that increased the probability."
French national agency Meteo-France told AFP that the current disruption is "an unprecedented event."
burs-ia/sms/vel/nn
© 2026 AFP
The content you requested does not exist or is no longer available.
