Cold spring and extremely hot summer: what’s going on? Greta Thunberg warned us: it’s about climate change. We listen about global warming, but winter never seems to end! Then suddenly, here comes a scorching heat! As Nasa explains, however, there is a lot of confusion when it comes to climate and weather. With climate, we refer to a long-term analysis of complex phenomena that take place on a global scale, and that can involve the atmosphere, the oceans, the Earth, in short, in its entirety. The weather, on the other hand, is limited to the so-called forecasts and verifications of the same: an event that will happen within a few hours or days, therefore in much reduced times, in limited areas.

The experts say

Marshall Shepherd, director of the Atmospheric Sciences Program at the University of Georgia and former president of the American Meteorological Society told CNN that “People often tend to confuse an event that is happening in the place where they live as an indication of what is happening globally”.

Stefan Rahmstorf, a physicist at the University of Potsdam, Germany, explained on Twitterhow these much longer and colder winters are a consequence of global warming: all this is happening because of the polar vortex.

The polar vortex

The polar vortex is a vast area of low pressure able to reach the stratosphere, thanks to the strong temperature difference between the polar regions and the equator. If the vortex is strong, the cold air remains confined above the polar areas, but if instead, it loses strength, it can fragment into one or more parts, and the air at low pressure and low temperature moves, interacting with that warmer outside the polar regions, so… from us!

Imagine pouring oil into a glass of water: the oil floats. But if you mix vigorously, the oil droplets are distributed in the glass. Under normal conditions, therefore, these vortices are stable, since the differences in pressure and temperature, which we could compare to the molecular tension, are such as to keep the system in balance. When the vortex at the North Pole is weak, the areas of high pressure normally present at mid-latitudes creep towards the north, pushing cold air towards the south. The cold air, in contact with the warm and humid mid-latitude air, drastically lowers the temperatures and heavy rainfall occurs, even in snow. But what “shakes the balance”?

Global warming

Not all parts of the Earth heat up at the same speed. The North Pole is warming up twice as fast as the globe average, causing a reduction in the volume of ice: this reduction seems to be linked to the polar vortex, which fails to strengthen as it should, and is a “victim” of the dangers of the currents in middle latitudes, with more frequent gusts of Arctic air than in the past in many areas of Europe, Asia, and North America.

The system is very complex, and the dynamics of the influence of the Arctic on the climate are still not entirely clear: several studies have examined the climatic data of these areas and concluded that in recent years the polar vortex has weakened more frequently and longer. And the situation is only going to get worse.

Exceptional events

We are used to seeing changes only when we are faced with exceptional events, such as record snowfall or extreme temperature peaks. Given the long and cold winters, it does not seem that this global warming is so effective. Yet, only in 2019, several records have already been established, almost all of them up! In this regard, climatologist Maximilian Herrera explained to New Scientist that, according to mathematical models, in a stable climate, the number of records of heat and cold should be equal. So, the climate is changing, but it is not always said that everyday weather is the mirror of the global situation.