Europe could face weeks of 40°C heat in current worst-case scenario

In today’s climate, Europe could be hit with a summer of rolling heatwaves and severe drought that would leave much of the continent suffering weeks of deadly temperatures, water shortages and energy price spikes.

That is the finding of new research that seeks to define the “worst-case scenario” for heat and drought possible now during the summer months in central and western Europe.

Laura Suarez-Gutierrez at ETH Zurich in Switzerland and her colleagues started with seven simulations of heatwaves in climate models. They then deliberately made tiny tweaks to the starting atmospheric state in the models and re-ran them 1000 times for each simulation to assess alternative outcomes, such as the heatwaves becoming more severe, a technique known as ensemble boosting.

“They generate lots of events with a very, very tiny change in the initial state of the model each time,” says Vikki Thompson at the Royal Netherlands Meteorological Institute, who wasn’t involved in the research. “These worst cases that they’re presenting are things that this model suggests could happen right now.”

In many cases, no heatwave emerged from the simulations, but in some cases the simulations produced heatwaves and droughts far more severe than anything seen previously in the historical record.

Under the most extreme scenarios, temperatures of up to 45°C (113°F) could linger for more than a month in parts of the continent, accompanied by extreme drought. Such an event would outstrip by a large margin the 2003 or 2018 heat and drought events, currently the worst on record in Europe, for duration and intensity, the researchers warn.

More worryingly still, the modelling suggests the worst heatwaves tend to occur immediately after a previous heatwave, potentially condemning Europe to a summer of rolling heat extremes with little respite for humans or ecosystems. This raises the risk of wildfires, drought, energy and food shortages and ecosystem breakdown, the researchers warn.

“Our findings expose the potential for unprecedented compound heat, fire weather and soil drought conditions well beyond historical extremes in the recent past,” Suarez-Gutierrez and her colleagues write in the study.

This pattern of successive heatwaves and persistent drought could be partly driven by extreme heat drying out soils, says Pascal Yiou at the Laboratory for Climate and Environmental Sciences in France. One heatwave may cause the soils to dry out, contributing to further heat extremes, he says. “Dryness of the soils actually generates weather systems that can last for a long time.”

Yiou, who works with Suarez-Gutierrez but wasn’t involved in this research, stresses these worst-case scenarios are unlikely – but possible – outcomes in the current climate. “They are not saying this is going to happen. They’re just saying that this might happen,” he says. He compares it with the 2021 heatwave in western North America, which smashed temperature records and became the deadliest weather event in Canadian history. The heatwave was made possible by highly unusual atmospheric conditions that produced extreme heat far beyond anything seen before.

“This work is about creating the perfect conditions for an extreme event,” agrees Jana Sillmann at the Centre for International Climate Research in Norway. This can help decision makers stress-test their emergency response plans, to ensure they can cope with, for example, a series of record-breaking heatwaves occurring over a single summer, she says.