More than 50 degrees in Death Valley in the United States, a historic record of 45.3 ° C in Catalonia, more than 43 ° C in Phoenix for twenty-four days and 46°C recorded in Sardinia. And to top it off, China has just broken its record with a heat wave lasting 27 days. In short, the northern hemisphere has been sweltering in the heat since early June.
Such heat waves would be “almost impossible” in Europe and the United States without global warming, shows a study by the World Weather Attribution (WWA) network. This scientific network, which assesses the link between extreme weather events and climate change, also believes that the latter has made the heat wave in China “at least 50 times more likely”. Climate change, caused by human-caused greenhouse gas emissions, “has made heat waves hotter, longer and more frequent,” says the WWA.
A warming that has already reached 1.2 degrees
“Recent heat waves are no longer exceptional events” and those that will occur “will be even more intense and more common if emissions are not reduced quickly”, conclude the researchers. Because if natural phenomena such as anticyclones or El Nino can contribute to triggering these heat waves, “warming up the temperatures of the planet by burning fossil fuels is the main reason why they are so serious”, underlines the WWA.
To reach these conclusions, the study’s authors – seven Dutch, British and American scientists – relied on historical weather data and climate models to compare today’s climate and its 1.2 degree global warming with what it once was. These results, produced on an emergency basis, are published without going through the long process of peer-reviewed journals, but combine methods approved by their peers.
A summer that “could become the norm”
The scientists particularly looked at the periods when the heat was “most dangerous”, which is from July 12 to 18 in southern Europe, from July 1 to 18 in the western United States, Texas and northern Mexico, and from July 5 to 18 in central and eastern China. They recalled that global warming worsens the intensity of temperatures: with it, heat waves in Europe are 2.5°C warmer, those in North America increase by 2°C and those in China by 1°C, indicates the WWA.
July 2023 is “on track to become the hottest July ever measured”, according to NASA and the European observatory Copernicus. “In the past, such events would have been aberrant. But in today’s climate, they can now reproduce approximately every 15 years in North America, every 10 years in southern Europe and every 5 years in China,” says Mariam Zachariah, a scientist at Imperial College London, who contributed to the study.
This early summer “could become the norm (…) and even be considered cool if we do not achieve carbon neutrality”, underlines British climatologist Friederike Otto. “There is an urgent need to stop burning fossil fuels and work to reduce our vulnerabilities. If we don’t, tens of thousands of people will continue to die,” she said, deeming “absolutely essential” the adoption of international legislation on the progressive elimination of fossils at the 28th United Nations Climate Conference (COP), in November in Dubai.