As many as 61,000 people may have died in Europe’s sweltering heatwaves last summer, according to new research, suggesting countries’ heat preparedness efforts are falling fatally short.

The study by researchers from European health institutes estimated that more than 61,600 people died from heat-related causes across 35 European countries from late May to early September 2022, during Europe’s hottest summer on record.

The study, published on Monday in the journal Nature Medicine, found that Mediterranean countries — Greece, Italy, Portugal and Spain — saw the highest death rate according to population size.

“The Mediterranean is affected by desertification, heatwaves are amplified during summer just because of these drier conditions,” said study co-author Joan Ballester, a professor at the Barcelona Institute for Global Health.

In a summer that saw European countries hit by intense wildfires and drought, Portugal recorded a peak temperature of 47C in July — just shy of the country’s hottest temperature on record, of 47.3C in 2003.

In absolute numbers, Italy, Spain, and Germany saw the most lives lost due to the heat, with 18,010; 11,324; and 8,173 deaths respectively.

As human-caused climate change drives temperatures higher, heatwaves are becoming more frequent and severe. Extreme heat can kill by causing heat stroke, or aggravating cardiovascular and respiratory diseases, with older people among the most vulnerable.

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The researchers used epidemiological models to analyse how many deaths could be directly linked to heat, out of all excess deaths European countries recorded last summer — a rate of excess mortality that was unusually high.

Countries including France introduced national plans to cope with intense temperatures following deadly heatwaves in Europe in 2003 — with early warning systems and more cooling green spaces in cities among the measures.

But researchers said last year’s high death toll suggests these strategies are falling short, and should be urgently strengthened.

“It’s an indication to those countries that they need to review their plans and see what is not working,” said Chloe Brimicombe, a climate scientist at Austria’s University of Graz.

Germany’s health ministry last month launched a campaign to guide local authorities in drawing up heat action plans, such as through increased protection for homeless people, or measures like providing more drinking water in public spaces.

“The number of deaths is increasing every year… It’s relatively easy to save them if we have a plan,” German health minister Karl Lauterbach said.