About 2,300 people may have died of heat-related causes in 12 cities in Europe during the recent heatwave that ended last week, according to a rapid scientific analysis published today.

The study focused on the 10 days, through July 2, during which large parts of western Europe were hit by extreme heat, with temperatures topping 40° Celsius in Spain and major forest fires breaking out in France.

Of the 2,300 people estimated to have died in that time, 1,500 deaths would not have occurred but for climate change, which made the heatwave even more intense, according to research by scientists at Imperial College London and the London School of Hygiene and Tropical Medicine.

“Climate change has made the planet significantly warmer than it would have been, which in turn makes it much more dangerous,” said Dr Ben Clark a researcher at Imperial College.

The report covers 12 cities in Europe — including Barcelona, Madrid, London and Milan — where researchers say climate change has caused temperatures to be 4° Celsius higher than normal.

“We estimate that global warming exacerbated the heat wave by 2 to 4° Celsius in most of the cities” examined, notably Paris, London and Madrid, according to Clark.

To estimate the impact of climate change, the scientists simulated the intensity of this episode in a world that would not have experienced massive burning of coal, oil and gas using historical meteorological data.

They concluded that the heat wave “would have been 2 to 4° Celsius less intense” in the absence of climate change in 11 of the 12 cities studied.

These extra degrees significantly increased the health risk to the 30 million residents of these cities.

Heat waves are particularly dangerous for the elderly, the sick, young children, outdoor workers and anyone exposed to high temperatures for long periods of time without respite, especially during a series of hot nights.

Large areas of southern Europe experienced a series of “tropical nights” during which temperatures did not drop enough to allow the body to recover.

Authorities estimate it will take several weeks to determine the final death toll. A series of similar incidents has already caused tens of thousands of premature deaths in Europe in previous summers.

Researchers from European health institutes reported in 2023 that up to 61,000 people may have died from the heatwaves that hit Europe in 2022, according to new research that suggests countries’ efforts to prepare for extreme heatwaves are failing.