Heat: It is logical to assume that one of the reasons for the extreme heat wave that has been suffocating the inhabitants of the northern hemisphere during the current summer could be global warming. After all, a record temperature of 54.4ºC in Death Valley, in the United States, on July 9th, can only be related to a rapid warming of planet Earth.
But what about the cold air mass that hit the southern region of Brazil at the end of last month, bringing sudden drops in temperature even in regions not very familiar with the phenomenon, such as the North and Northeast of the country? The low temperatures, and even the blizzards observed in some places, led to the question: if we are in global warming, why all this cold?
To answer this question, an international team of scientists looked into the matter, looking for a causal link that explains how global warming is capable of generating, at the same time, suffocating heat waves and freezing snowstorms. The result of the study was published on Monday (09) in the scientific journal Advances in Atmospheric Sciences.
To clarify the unclear mechanisms between these climate changes, the researchers worked with three extreme cold events that occurred successively in East Asia and North America during the past winter.
For the study’s first author, professor of climate and atmospheric sciences at the Fairbanks University of Alaska, USA, Xiangdong Zhang, these events “provide a unique opportunity to examine what seemingly incompatible physical processes or mechanisms drive these events”, he said in a press release.
To link the events, the research connected the so-called “break” of the polar vortex, a huge ring of cold, low-pressure winds in the Earth’s stratosphere above the north pole, with sub-zero temperature events. This is due to the connection between the polar vortex and jet streams, a kind of airflow with strong winds that flow from west to east, at low altitude.
Thus, when the planetary temperature rises, due to global warming, the balance between the polar vortex and the jet stream weakens and “breaks”, which allows the extremely cold air to descend to lower latitudes as the warm air rises to the polar regions.