Heatwaves are only going to be more frequent, more intense and last longer, the World Health Organization (WHO) said on Tuesday in the wake of days of record-breaking temperatures that claimed dozens of lives across Europe.
"The summers ahead will be harder," Hans Kluge, the director of the WHO's European region, said in a statement, warning that heatwaves were no longer one-off events but recurring crises.
But as human-made climate change makes heatwaves around the world worse, will the human body be able to adapt to higher temperatures?
Yes, to some extent - but that adaptation has clear limits, says medical meteorologist Kathrin Graw, who works with Germany's national weather service, the Deutscher Wetterdienst (DWD).
"Within a heatwave, the longer it lasts, the more of a burden it becomes for people day by day," Graw told dpa. "Especially when recovery at night is also lacking - when nights remain warm and sleep quality deteriorates as a result - the heat can be harder to cope with the following day."
"The longer the heat persists, the more people die," Graw said, pointing to a recent DWD study that showed that the risk of fatal consequences from heat also rises with the duration of a heatwave.
Among people with cardiovascular disease, up to 18% more deaths occur on the 11th and 12th day of a heatwave compared with periods without heat. In the first days of a heatwave, the heat-related excess mortality in this group stands at 8.5%.
The human body is nonetheless capable of adapting somewhat to heat over the course of a summer, the medical meteorologist said. Weather services like Germany's DWD also take this into account in warnings, and the threshold at which heat warnings are issued is lower at the start of summer or after a cooler period than at the end of summer.
As the climate crisis makes heatwaves more frequent and intense, the question arises whether the human body can also learn to cope better over the long term. Graw said there are some indications of this, but they too are very limited.
People in more southern countries have been living with heat for longer, and heat-related mortality in these areas is somewhat lower than in more northern countries.
"But long-term adaptation to higher temperatures will not be possible without limits either - especially not when the changes the body has to adapt to are happening very quickly," Graw warned. "The rise in temperature due to climate change has unfortunately accelerated in recent years."
Heat poses a particular risk for older people, children, pregnant women and those with pre-existing conditions.
