BRUSSELS — Climate change was responsible for an estimated 16,500 additional deaths in Europe this summer, according to a study by epidemiologists and climate scientists published Wednesday.

This represents 68 percent of the 24,400 estimated heat-related deaths that happened this summer in large European cities, according to researchers from Imperial College London and the London School of Hygiene and Tropical Medicine.

“These numbers represent real people who have lost their lives in the last months due to extreme heat. Many of these would not have died if it wasn’t for climate change,” said Friederike Otto, a climate science professor at the Centre for Environmental Policy at Imperial College London, who contributed to the study.

Climate change has made Europe’s largest cities, on average, 2.2 degrees Celsius warmer compared to a pre-industrial world. This not only makes them hotter in general, but increases the risk of heat waves, Otto said.

This summer was the third hottest on record, according to the EU’s Copernicus Climate Change Service.

Extreme heat is also putting older people and those with underlying health conditions, such as heart disease and diabetes, at higher risk.

People aged 65 and over accounted for 85 percent of the estimated excess heat-related deaths this summer, according to the study, highlighting how hotter summers are becoming increasingly deadly for Europe’s aging population.

“An increasing heat wave temperature of just 2 to 4 degrees [Celsius] can mean the difference between life and death for thousands of people,” said Garyfallos Konstantinoudis, a lecturer at the Grantham Institute for Climate Change, who contributed to the study. “This is why heat waves are known as silent killers.”

But this estimated death toll is just a snapshot, according to the researchers, as the study only focused on 854 cities with more than 50,000 people in the EU and the U.K. This represents only about 30 percent of Europe’s population.

However, these deaths are “preventable” if countries continue to reduce their emissions and combat climate change, said Malcolm Mistry, assistant professor at the London School of Hygiene and Tropical Medicine, who contributed to the study.

Italy and Spain were the most severely affected, with climate change contributing to an estimated 4,597 additional heat-related deaths in Italy and 2,841 in Spain.

But the researchers also found that “although the excess mortality rates are lower in northern Europe, mainly because temperatures were lower, the proportion of deaths attributable to climate change is higher.”