Polar Vortex & Global Warming: Explained

We take inspiration to open this article from the snow situation at the Milan Cortina 2026 Winter Olympics. Until a few weeks ago, snow was scarce, or completely missing. The competitions were still guaranteed, the organizing committee assured, thanks to the production of 2.4 million cubic meters of artificial snow. Without considering, of course, the costs and water, energy and environmental impacts of what they call “planned snow”.

Then the snow came. And it almost caused a nuisance, forcing extra work to – paradox of our times – remove the natural snow from the perfectly prepared slopes. Punctually, Senator Claudio Borghi returned to social media with one of his usual ones skeptical comments on climate changerelaunching doubts about anthropic responsibilities. And he tweeted: «But what is all that snow doing on the trees around the special track in Bormio? But wasn’t there the guy in the tank top for climate change?

Because a wave of frost does not deny the climate crisis

Snow in the mountains, after all, shouldn’t even make the news. Rather, it is the waves of frost in Europe or the United States that promptly rekindle superficial statements by politicians who transform meteorological episodes into arguments against climate change. On New Year’s Eve, Donald Trump tweeted: «The east coast of the United States is hit by a wave of ice and this could be the coldest New Year’s Eve on record. We could use some of that good old Global Warming that our country, and not others, is paying trillions of dollars to protect us from. Cover yourselves well.”

Then, at the beginning of February, a new and intense outbreak of cold air arrived in the United States, with snowflakes as far away as Florida, temperatures close to zero in Miami and even Cuba. And here again was the outbreak of denialist statements from various political leaders, as if every episode of intense cold could become “proof” that global warming does not exist.

Thus the usual communication short circuit is repeated: weather and climate are confused, the single event contrasted with the long-term trend, the exception passed off as a denial of the rule. Yet the scientific reality is clear: extreme cold is not only compatible with a warming planet, but in some cases it can be an indirect consequence, through alterations in atmospheric circulation and more unstable dynamics of what meteorologists call the polar vortex.

Weather and climate are two different things

Il climate it is what is expected based on the past, time is what touches us every day. The climate tells you which clothes to keep in the closet, the tempo tells you which ones to wear. These are the simplest and most classic examples used to distinguish between time and climate. The climate changes slowly: it has always changed, even in the past, but usually on time scales longer than a human lifetime. The weather, however, changes every day.

Today, however, the climate is changing faster: the planet is warming, rainfall patterns are changing and, naturally, so are the frequency and intensity of waves of frost and snow. This does not mean that all the basic rules have been ignored. In winter it continues to be colder than in summer, at the North Pole it is colder than at the Equator and – with exceptions such as temperature inversions – it is colder in the mountains and it snows more easily than in the plains.

In short, a single snowfall or a wave of frost they do not deny a heating process unequivocal in medium-long term averages. Indeed: some elements indicate that, in a warmer climate marked by more frequent extreme events, cold extremes do not disappear and, under certain conditions, can even become accentuated.

What the polar vortex is (and what it isn’t)

The polar vortex is one large area of ​​semi-permanent low pressure which forms at high altitudes of the atmosphere, more precisely in the stratosphere, above 12-13 kilometers of altitude in medium latitudes, above the North Pole. During the cold season it is present almost constantly over a very large region, with a diameter of thousands of kilometers. Its center is generally located near the North Polebut its influence extends to the middle latitudes.

As mentioned, it develops mainly in the stratosphereabove the troposphere – the layer of atmosphere that goes from the ground up to about 10-12 kilometers above sea level, where clouds form and meteorological phenomena occur. Above the polar regions the stratosphere can start even lower, around 7-8 kilometers. In this area, a vast circulation of very cold air, called the polar vortex, is organised. We distinguish a stratospheric vortex, higher up, and a tropospheric vortex, closer to the ground and therefore more directly connected to the weather we observe.

If you looked at it from above the North Pole, it would look like a circular counterclockwise movementnot perfectly round, but wavy. When it is compact it is more stable; when it is more wavy it can favor outbreaks of cold air towards the south, up to affecting North America or Europe. A similar system also exists above the South Pole, where it is called the Antarctic gyre.

How cold air circulates between the North Pole and mid-latitudes

There are many dynamics at play and they can become technically complex. For our purposes it is sufficient to know that the polar vortex functions as a sort of “container” of the freezing air which, under certain conditions, can slide towards the middle latitudes.

When the vortex is compact and centered on the North Pole, one prevails more easily in Europe zonal circulationthat is, from the west, with the passage of Atlantic disturbances accompanied by relatively mild air or with the presence of subtropical anticyclones. In the United States, similar configurations are observed, although also influenced by the dynamics of the Pacific.

In other cases, however, the vortex can undulate or even divide into several lobes – an event known as “split”, especially in the stratosphere – favoring the descent of very cold air masses towards North America or central-southern Europe. Some studies suggest that certain conditions may increase the likelihood of these ripples; the possible link with climate change is still the subject of research and scientific debate.

Because the polar vortex weakens and deforms

The polar vortex can change shape for several reasons. First of all, it can be disturbed by large planetary waves, called Rossby waves. Within the medium western currents that flow in the middle latitudes, marked undulations of the zonal flow can in fact be generated, due to the large heat exchanges between the Equator and the Poles, between continents and oceans, and further complicated by the presence of mountain chains. These waves can propagate towards the stratosphere and weaken the zonal circulation of the polar vortex.

One of the phenomena most studied by meteorologists is the so-called sudden stratospheric warming (SSW, sudden stratospheric warming). In fact, it may happen that, for reasons still being researched, there may be a rapid increase in temperatures at high altitudes – above the tropopause, between 8 and 12 kilometers depending on season and latitude – accompanied by the reversal of the prevailing winds in the stratosphere. Under these conditions the polar vortex can move (displacement) or divide into two lobes (split).

The more energy in the system, the more instability

The consequences are not always the same and vary from episode to episode. Generally, however, increases the likelihood of persistent cold outbreaks to mid-latitudes in the following weeks.

Stratospheric warming is carefully monitored via satellites, radiosondes and specialized instruments such as LIDAR, and is generally well detected and predicted. What remains uncertain is where the frigid Arctic air will end up if the vortex shifts or splits. Coming to the situation in 2026, the polar vortex has brought cold air to North America on several occasions, without causing significant outbreaks in Europe.

Establishing a direct link with global warming is complex. Some evidence points to a possible connection to Arctic amplification, the process by which the Arctic is warming much faster than the global average. This reduces the thermal gradient between the Pole and mid-latitudes, weakening and making the jet stream more wavy. A jet stream less tense can favor atmospheric blocks and descents of cold air towards the south. The link is neither automatic nor definitive, but some scientific evidence points in this direction.

Finally, it should be remembered that not every episode of frost in the middle latitudes can be traced back to disturbances in the stratospheric vortex: cold outbreaks can also depend on tropospheric configurations independent of the polar vortex. In any case, one thing is clear: global warming does not eliminate the coldalters its dynamics. And it is precisely this greater instability that makes intense waves of frost compatible with a planet that, as a whole, continues to warm.

The real misunderstanding: local cold versus global warming

A cold wave affects a certain area for days or weeks; global warming affects the entire planet on scales of decades. Saying that a cold episode denies anthropogenic climate change is like claiming that birds deny the force of gravity.

It should be remembered, in fact, that with climate change the cold doesn’t go away: despite being attenuated on average by global warming, it can redistribute. In particular configurations of atmospheric circulation, Arctic air masses can move from the North Pole towards mid-latitudes. And the climate system is not linear: more energy in the system can mean more instability and more extreme events, including in the form of frost and snow.

Using a snowfall to deny a global climate trend is doing cherry pickingselect data at your convenience: a classic logical fallacy. Climate science is not done with tweets or political slogans. Climatology is based on long-term observational series, averages, anomalies and atmospheric physics. Tweets can build populist consensus, but they don’t change the laws of thermodynamics.