Extreme heat could kill 73 people per 100,000 by 2100 as world temperatures continue to rise.

The warning comes from a team of more than 30 scientists at the Climate Impact Lab, who gathered 399 million death records from 41 countries for the study, as reported on by Earther.

Temperatures are increasing across the globe due to global warming. The team found that if greenhouse gas emissions are not curbed, heatwaves could kill as many people as fatalities linked to HIV, malaria and yellow fever combined.

Following an investigation into temperature and mortality, the results showed that it is those with underlying cardiovascular issues that are more at risk.

The records show that the direct impact of extreme heat, which results in heat stress or heat stroke, only affected a small pieces of deaths linked to rising temperatures.

However, the largest amount of heat-related fatalities were a result of indirect impacts, as heat is known to increase risk of heart attacks among those with cardiovascular issues.

Amir Jina, environmental and development economist at the University of Chicago and co-author of the study, told Earther in an email that when an individual with heart problems is exposed to extreme heat, their ‘body starts pumping more blood around, trying to stay cool and it puts extra stress on the system.’