The key facts

  • The polar vortex weakened unprecedentedly early — the winds reversed direction
  • Scientists link such a disruption to an increased risk of cold outbreaks in the US, Europe and East Asia
  • Cold is not guaranteed: El Niño may soften the effect, and the link to climate change remains disputed

Record-early disruption of the vortex

Above the Arctic, at an altitude of roughly 10–50 kilometers, an enormous belt of cold, low-pressure air spins — the polar vortex. According to Deutsche Welle, citing observations, this year the vortex weakened unprecedentedly early, and its westerly winds reversed direction. 'As far as we know, this is the earliest stratospheric vortex disruption ever observed,' Tim Stockdale and Frédéric Vitar, chief scientists at the European Centre for Medium-Range Weather Forecasts (ECMWF), told AFP. The French weather service Meteo-France called what is happening 'an unprecedented event'.

How the vortex affects weather below

The vortex normally keeps the coldest Arctic air locked near the pole, but when it weakens it can deform, split or shift, altering the position of the jet stream that shapes surface weather. MIT climatologist Judah Cohen explained to AFP that an early breakdown of the vortex 'really raises the probability of outbreaks of cold air' into the latitudes where the densely populated regions of the Northern Hemisphere are located — the United States, Europe and East Asia. Such disruptions are often triggered by a 'sudden stratospheric warming,' when temperatures in the polar stratosphere rise sharply within a few days; the vortex may take several weeks to recover.

A cold winter is not a foregone conclusion

The previous vortex disruption contributed to the 'Great Texas Freeze' of February 2021, when more than a week of frost caused power outages and the deaths of hundreds of people. But, as the UK Met Office stresses, the state of the vortex merely shifts the probabilities rather than acting as an 'on/off switch' for cold: other factors will also determine the outcome of the winter. Cohen suggested that the strengthening El Niño, which is usually associated with milder winters and, according to available data, is expected to peak toward the end of the year, could 'soften or alter' the consequences — though that is not certain. Some studies link the increasing frequency of vortex disruptions to the rapid warming of the Arctic caused by climate change; however, as DW notes, this link has not been definitively proven and remains a matter of scientific debate. How the current disruption will affect winter in the Northern Hemisphere is not yet known.