More than 47,000 Europeans died from heat-related causes during 2023, the world’s hottest year on record, a new report in Nature Medicine has found.

But the number could have been much higher.

Without heat adaptation measures over the past two decades, the death toll for Europeans experiencing the same temperatures at the start of the 21st century could have been 80 percent higher, according to the new study. For people over 80 years old, the toll could have doubled.

Some of the measures include advances in health care, more widespread air-conditioning, and improved public information that kept people indoors and hydrated amid extreme temperatures.

“We need to consider climate change as a health issue,” said Elisa Gallo, the lead author of the study and a postdoctoral researcher at the Barcelona Institute for Global Health, a nonprofit research center. “We still have thousands of deaths caused by heat every year, so we still have to work a lot and we have to work faster.”

Counting deaths from extreme heat is difficult, in part because death certificates don’t always reflect the role of heat. The study used publicly available death records from 35 countries, provided by Eurostat, the statistics office of the European Union, and representing about 543 million Europeans.