Heat is a killer — and climate change is driving up its body count. On average, about 37 percent of heat deaths can be tied back to human-caused climate change, according to a new study in Nature Climate Change.

The study looked at data from 732 places in 43 countries over a period of about three decades, from 1991-2018. They used information including heat deaths and temperature readings from those places to build computer models that calculated how many deaths could be attributed to climate change. The numbers varied depending on location, with a larger percentage of climate-change related deaths occuring in warmer countries than cooler ones.

Overall, about 166,000 people died of heat-related deaths between 1998 and 2017, according to the World Health Organization. Thanks to climate change, more people are being exposed to heatwaves than ever before. “Between 2000 and 2016, the number of people exposed to heatwaves increased by around 125 million,” the WHO estimates.

There is one notable limitation to this new study — while hundreds of locations were included, many areas of Africa and Southeast Asia were not, due to a lack of data. Gathering that information in the future will be vitally important for new efforts to create a global accounting of heat-related deaths and illnesses.

“The countries where we do not have the necessary health data are often among the poorest and most susceptible to climate change, and, concerningly, are also the projected major hotspots of future population growth,” climate change researcher Dann Mitchell wrote in an article accompanying the paper. “Obtaining these data will be key for science to provide the information needed to help these countries adapt.”

“We are thinking about these problems of climate change as something that the next generation will face,” said Ana Maria Vicedo-Cabrera, the lead author of the paper in an interview with The New York Times. “It’s something we are facing already. We are throwing stones at ourselves.”

That’s in line with other research, which has found that climate change is already a disaster for human health. Older people, in particular, are particularly vulnerable, with heat-related deaths for this age group increasing by about 54 percent between 2000 and 2018. Some areas of the planet are getting hit worse than others, with extreme conditions happening even more frequently than predicted.