Yes, phenomena like Filomena are compatible with global warming, and may be more frequent

Now that Spain has faced the heaviest snowfall in half a century and extreme temperatures, never before recorded, many wonder if all this does not put global warming into question. Some “deniers” have been quick to cite the storm Filomena as proof that global warming is not true. Nothing is further from reality.

In fact, according to some models, climate change may cause episodes such as the one that caused the storm Filomena to occur more frequently in mid-latitudes.

The truth is that several factors have been added to cause the “perfect storm” that has paralyzed half of Spain, starting with the capital, Madrid.

The squall Filomena did not really bring cold air, but warmer air and very, very heavy with humidity. In fact, other parts of the Mediterranean have experienced exceptionally high temperatures with Malta registering 22ºC, the record for a month of January.

This warmer air was met by the cold air that had been installed in much of Western Europe for several days, causing the situation that Spain now faces.

What does global warming have to do with it?

The doctor in Physics and meteorologist from Mar Gómez explains that the most accepted model of the effects of climate change is that the warming of the Arctic weakens the jet stream and causes it to fluctuate more, reaching more northern latitudes.

In winter, this means that polar cold can “escape” further south than usual, so extreme cold spells in the northern hemisphere in winter could become more common. Under this model the same phenomenon also causes more frequent and longer heat waves during the summer.

Last year, conversely, the jet stream and the polar vortex were very stable and there was virtually no winter in many parts of Europe.

Another factor commonly accepted – and purely logical – is that global warming increases humidity in the atmosphere (due to increased evaporation) causing storms with more intense precipitation.

In this case it was snow, due to the cold that had settled in Europe, but this autumn the record of storms in the Atlantic was broken and in Europe there have been serious episodes of flooding, which are increasingly frequent.

Climate change does not eliminate weather variability

Nor would it be true to say that the cold of recent weeks and what happened with the storm Filomena is a consequence of global warming. It’s too early to tell and complicated attribution studies would have to be done.

What climate change will not cause is that the variability of the meteorology disappears. Again Mar Gómez, explained to us that the weather is like our mood, that it can change at any time. The climate can be compared to our character which is more stable.

Just as we can have an outburst of bad humor even if we have a calm character, global warming is not at all incompatible with situations like the one caused by the storm Filomena. “At the moment, nothing prevents us from having important episodes of snowfall or even harsh winters, but the general trend continues to increase in temperatures. What counts is the trend and points to the rise in temperatures, although these days we see the opposite. The case of Madrid now snows less than before, but it can continue to do so “explains Gómez.

Sudden stratospheric warming in the Arctic and cold in mid-latitudes

In the days leading up to storm Filomena, there has been a sudden warming in the Arctic stratosphere. In fact, the North Pole region is experiencing much higher temperatures than usual.

However, the extreme cold has moved further south. In Europe, but records are also being broken in Asia.

The imbalances in the temperature of the Arctic affect the climate of the entire planet and the fact that it is experiencing more heat than usual – even if it causes colder in Europe or Asia – is fully consistent with the global warming trend.

Everything points to several weeks of extreme cold, the polar vortex weakens

One of the consequences of stratospheric warming in the Arctic has been to displace the polar vortex, the current of very cold air that is usually maintained around the North Pole, in part thanks to the jet stream.

While the Arctic maintains higher temperatures than usual, the polar vortex, which also connects the stratosphere with the atmosphere (our “time”).

The latest forecasts suggest that the polar vortex could continue to be weakened and installed over Europe and the United States. If it stays that way, all indications are that this will trigger weeks of extreme winter weather.

The last six years, the hottest on record

The trend towards global warming is hardly debatable in view of the latest data. The year 2020 was the warmest on record, tied with 2016, and the past six years are the warmest on record according to the latest Copernicus newsletter, the European Earth Observation Network.

“The extraordinary climate events of 2020 and data from the Copernicus Climate Change Service show us that we have no time to lose. We must come together as a global community, to ensure a just transition to a zero emissions future. It will be difficult, but the cost of the inaction is too great, so the commitments made in the framework of our European Green Agreement are very necessary “, highlighted Matthias Petschke, Director of Space, Directorate General for Defense Industry and Space of the European Commission, in the presentation of the 2020 temperatures report.