Heat waves in many parts of the world without apparent cause

In recent years, a disturbing climate phenomenon is emerging: heat waves so extreme that they far exceed what any global warming model can predict or explain are unleashed in different regions of the Earth. A new study provides the first global map of these heat wave-prone regions, located on every continent except Antarctica. In recent years, these heat waves have killed tens of thousands of people, withered agricultural fields and forests, and sparked devastating wildfires.

The study was carried out by a team led by Kai Kornhuber, from Columbia University in New York, United States.

The wide and unexpected temperature ranges by which recent regional heat waves have broken previous records have raised questions about the extent to which climate models can provide adequate estimates of the relationships between global mean temperature changes and climate risks. regional.

The study analyzes heat waves over the past 65 years and identifies areas where extreme heat is accelerating considerably faster than “normal” heat. This often results in maximum temperatures that have been repeatedly exceeded by notable, sometimes unheard of, margins.

For example, a nine-day heat wave that hit southwestern Canada and part of the United States in June 2021 broke daily records in some locations, with 30 degrees Celsius above normal values ​​for the time of year. This included the highest ambient temperature ever recorded in Canada since systematic measurements: 49.6 degrees Celsius, in Lytton, British Columbia. This town burned the next day in a forest fire caused largely by the desiccation of the vegetation caused by the extraordinary heat. In the US states of Oregon and Washington, hundreds of people died from heatstroke and other health problems related to excess heat.

Regions where observed heat waves exceed climate model trends. The boxed areas with the darkest red colors are the most extreme. The lighter orange or red ones outperform the models, but not by much. The yellow ones more or less match the models. Those in green and blue are below what the climate models predict. (Image: adapted from: Kornhuber et al., PNAS 2024)

These extreme heat waves have occurred mostly in the past five years, although some occurred in the early 2000s or earlier. The most affected regions are central China, Japan, Korea, the Arabian Peninsula, eastern Australia and some areas of Africa. Other regions prone to heat waves include Canada’s Northwest Territories and its High Arctic islands, northern Greenland, the southern tip of South America, and scattered parts of Siberia. Areas of Texas and New Mexico also appear on the map, although they do not belong to the most extreme heat wave risk category.

According to the report, the most pronounced and constant trend comes from northwest Europe, where sequences of heat waves caused about 60,000 deaths in 2022 and about 47,000 in 2023. These occurred in Germany, France, the United Kingdom, the Netherlands and other nations. . In those areas, in recent years, the hottest days of the year are warming twice as fast as days with average summer temperatures. The population in these areas is especially vulnerable because, unlike other places, few people there have air conditioning, since traditionally it was almost never needed. The heat waves have continued; Last September, new maximum temperature records were broken in Austria, France, Hungary, Slovenia, Norway and Sweden.

The study is titled “Global emergence of regional heatwave hotspots outpaces climate model simulations.” And it has been published in the academic journal Proceedings of the National Academy of Sciences (PNAS). (Fountain: NCYT by Amazings)