'Silent killers': Climate change made European heatwaves deadlier; temperatures up by 4°C

Human-induced climate change made the recent heatwaves across Europe significantly more intense, with temperatures in many cities up to 4°C higher than they would have been without global warming, according to a recent study.

Researchers from five European institutions studied 12 cities, including major capitals such as Paris, London and Madrid, which have a combined population of over 30 million. They concluded that additional heat likely led to a higher number of heat-related deaths than would have occurred in a cooler climate, scientists said on Wednesday, reported AFP.

The findings raise fresh concerns about the increasing risks to public health, particularly for vulnerable groups. Heatwaves spanned from late June to early July, saw temperatures soar past 40°C in several European countries, setting new records and triggering health warnings.

According to the EU’s climate monitor Copernicus, June was the hottest on record in western Europe. The extreme heat forced the closure of schools and tourist attractions in many areas.

Analysis of historical weather data revealed that, in all but one of the 12 cities studied, the temperatures would have been 2–4°C cooler without the influence of human-caused climate change.

“What that does is it brings certain groups of people into more dangerous territory,” said Ben Clarke, a researcher from Imperial College London, which co-led the study along with the London School of Hygiene and Tropical Medicine. “For some people, it's still warm, fine weather. But for now a huge sector of the population, it’s more dangerous,” he added.

For the first time, the study also attempted to estimate the number of deaths attributable to the heatwave and the role climate change played.

“An increase in heatwave temperature of just two or four degrees can mean the difference between life and death for thousands of people,” said Garyfallos Konstantinoudis, a lecturer at Imperial College London. “This is why heatwaves are known as silent killers. Most heat-related deaths occur in homes and hospitals out of public view and are rarely reported,” he added.

The researchers were based in the UK, Netherlands, Denmark and Switzerland, emphasised that their estimate was only a partial snapshot of the overall impact, as official figures are not yet available.

Heatwaves pose the greatest danger to the elderly, children, the sick, outdoor workers and those without access to cooling or shade. Urban areas face heightened risks due to the heat island effect, where buildings and paved surfaces absorb and retain more heat than surrounding areas.