Texas had some of the lowest temperatures in more than 30 years last week, and the days between February 14-18 they were the coldest for average temperature since 1981. Because of the local electricity grid limits, the cold has left millions of people without electricity and heating. According to some scientists, these meteorological phenomena could be linked to global warming caused by human activities.
The idea might seem counterintuitive, because global warming is associated with rising temperatures, but the matter is more complex.
Areas of the Earth where the average temperature is rising fastest are the Poles. The climatic phenomena are very complex and it is not yet known what all the consequences of the increase in polar temperatures are, but according to one of the existing hypotheses (“Hot Arctic, cold continents”) the warming of the North Pole would bring the polar winds towards the continental areas to the south more often than in the past, causing some of the most extreme weather phenomena of recent decades, such as the recent snowstorms in Texas.
The name of the hypothesis does not mean that the Arctic is warmer than the continents, but that it is warmer than its classic average temperatures. The concept is well conveyed by many maps showing the Earth’s surface temperature anomalies in recent weeks compared to the 1979-2000 average: colors that tend towards red show where the temperature is higher than usual, those towards purple where it is unusually lower.
As much of USA gripped by bitter cold, other parts of the globe are unusually warm
This map shows the 2 m air temperature anomaly (ie the departure from the 1979-2000 reference period)https://t.co/j4fBXDdLsg pic.twitter.com/VMvzdvfI6Z— World Meteorological Organization (@WMO) February 15, 2021
In the atmospheric layers above the North Pole there is a vortex of cold winds, the so-called polar vortex, or more correctly Arctic vortex. Generally the Arctic vortex is “held” above the Pole by a jet stream, ie a fast flow of air that is further south. The jet stream acts as a barrier to the Arctic vortex as if it were the edge of a bowl, explained to Vox University of Colorado climatologist Walt Meier, expert on the Arctic climate: “Cold air is heavier, so it’s kind of trapped by this bowl of hot air. It does not go over the edge ». Or at least, it doesn’t usually.
As temperatures in the Arctic rise, part of the vortex of cold winds can pass the edge of the “bowl”, exceeding the usual limits of the jet stream and thus reaching continental areas. The phenomenon can be better understood by looking at one of the graphical representations that explain it.
The air that passes the edges of the bowl is warmer than typical Arctic winds, but is still very cold. Because of this it may have been able to cause heavy snowfalls like those recently occurred in Texas (which has no mountain ranges to protect it), or in Europe two years ago.
– Read also: Global warming is there, even if it is very cold
It is not climate change due to human activities that causes these “spills” of cold winds towards continents – in the United States it happens on average six times a decade, says the National Oceanic and Atmospheric Administration (NOAA), the American federal agency that deals with meteorology and climate – but according to some scientists, global warming has made them more frequent.
Not all climatologists agree and in the course of 2020 on the scientific journal Nature have been published due Education who contest the hypothesis “Arctic hot, continents cold”. One of them says that the influence of the Arctic climate on that of the lower latitudes is reduced compared to that of other climatic phenomena.
In general, scientists believe that as a result of climate change the average winter temperatures of the northern hemisphere (ours) will increase. This prediction, however, he explained on Twitter Stefan Rahmstorf, professor of ocean physics at the University of Potsdam, does not necessarily contradict the hypothesis that some winter weather phenomena characterized by intense cold may become more frequent, at least in the short term.
– Read also: Because the cold broke the electricity grid in Texas
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