Las extreme heat waves are a climate phenomenon which consists of a significant and prolonged increase in temperatures in a certain region. It has been pointed out that the increase in frequency of these events is associated with the global warming.
But scientists working at institutions in the USA y Austria discovered that a surprising new phenomenon is emerging: different regions of the world They are experiencing repeated heat waves that are so extreme that they spill over beyond what any global warming model can predict or explain.
The discovery was published in the journal Proceedings of the National Academy of Sciences. From the data, the researchers created the first global map of these regions with heat waves, like huge patches of skin. The map also includes regions in the south end of South America affected by heat waves.
In recent years, these extreme events have generated serious impacts. They caused the death of tens of thousands of people. They also ruined crops and caused devastating forest fires.
“These are extreme trends that are the result of physical interactions that we may not fully understand,” acknowledged the lead author. Kai Kornhuberassociate scientist at the Lamont-Doherty Earth Observatory within the Climate School of the Columbia University in New York City.
“These regions become temporary greenhouses,” highlighted Kornhuber, who is also a researcher at the International Institute for Applied Systems Analysis in Austria.
He Intergovernmental Panel on Climate Change (IPCC) considers that heat waves are one of the most worrying phenomena of climate change. In two reports, it warned that heat waves will intensify and become more frequent due to rising global temperatures.
These phenomena have devastating effects on human health, especially among vulnerable populations. Heat-related deaths, cardiovascular and respiratory diseases, as well as thermal stress are increasing in urban areas where infrastructure is not prepared for high temperatures.
They also impact agriculture, as extreme heat affects crops, reduces water availability and increases the risk of vegetation or forest fires. These effects can have serious consequences for food security and water supplies.
The study published in PNAS pointed out that the regions most affected by heat waves Included on the map are China, Japan, South Korea, the Arabian Peninsula, eastern Australia, and scattered parts of Africa. Others are the Northwest Territories of Canada and its High Arctic islands, northern Greenland, the southern tip of South America and scattered areas of Siberia.
The researchers postulated that Those extreme heat waves affecting certain regions of the world could be the result of complex physical interactions that are not yet fully understood.
They argued that these areas become “temporary greenhouses” due to exceptional atmospheric conditions. It implies that the increase in extreme temperatures cannot be explained solely by general global warming, but also involves a series of complex local and global factors.
Previously, other hypotheses had been proposed to explain the phenomena of extreme heat waves. One of the most influential explanations was the one that related these events to the polar jet ripples.
This phenomenon implies that the polar jet, which consists of a fast air current that circles the northern hemisphere, is altered by the faster warming of the Arctic.
As the Arctic warms more quickly than other areas, the polar jet becomes less stable and, consequently, can form the so-called “Rossby waves”. Those waves pull warm air from lower latitudes into normally temperate regions, causing extreme heat waves in areas that don’t traditionally experience such phenomena.
This hypothesis was defended by Kornhuber and others in previous studies when analyzing the heat waves that affected Europe and Russia.
Another hypothesis related to the case of the Pacific Northwest and southwestern Canada, presented in a previous study led by Kornhuber, suggests a combination of factors including the long term climate changehe thawing of regional vegetation and the influence of smaller atmospheric waves.
The study, published in Nature Climate Changerevealed that the global warmingby reducing the amount of water available in vegetation to evaporate, intensified the heat during extreme waves.
The differences between these hypotheses lie mainly in the causality of extreme events. While Rossby waves focus on changes in large atmospheric currents due to global warming, the new hypothesis presented in the new study emphasizes the physical interactions at the regional level that are not yet fully understood, such as the formation of “temporary greenhouses”.
Furthermore, previous hypotheses usually consider global factors as the main causes, while the new one points to the complexity of the interaction between global and local factors that trigger extreme events.
