International Study Finds Man-Made Climate Change Responsible for a Third of Heat-Related Deaths

June 1, 2021
Man-Made Climate Change Study

A recent study published in Nature Climate Change found that a third of heat-related deaths are due to man-made climate change. Noah Scovronick, PhD, MSc, was second author on the article.   

Using empirical heat-related data from 732 cities in 43 countries around the world between 1991–2018, the researchers found that 37 percent (range 20.5–76.3%) of heat-related deaths can be directly attributed to anthropogenic (or man-made) climate change and that increased mortality is evident on every continent. This international study was coordinated by the University of Bern and the London School of Hygiene & Tropical Medicine and was conducted by 70 researchers.

Scenarios of future climate conditions predict a substantial rise in average temperatures and in the occurrence of extreme events such as heatwaves, leading to future increases in the related health burden. However, so far, no study has evaluated if and to which extent these impacts have already been experienced in the recent decades. This study now provides evidence on this topic.

More global warming means more deaths

More precisely, the epidemiological investigation focused on man-made global warming, in a "detection and attribution" study that identifies and attributes observed phenomena to changes in climate and weather. The researchers examined past weather conditions projected under scenarios with and without anthropogenic emissions, therefore being able to separate the warming and related health impact linked with human activities from natural trends.

"We expect the proportion of heat-related deaths to continue to grow if we don't do something about climate change or adapt," says Ana M. Vicedo-Cabrera, PhD, the first author of the study. "So far, the average global temperature has only increased by about 1°C, which is a fraction of what we could face if emissions continue to grow unchecked."

Regional differences in heat-related health risks

While, on average, over a third of heat-related deaths are due to human-induced climate change, impact varies substantially across regions. The number of climate-related heat casualties ranges from a few dozen to several hundred deaths each year, depending on the local changes in climate in each area and the vulnerability of its population. Interestingly, populations living in low and middle-income countries, which are responsible for a minor part of anthropogenic emissions in the past, are those most affected, with the proportion of human-induced heat-related mortality higher in Central and South America and Southeast Asia.

This study shows us that the impacts of climate change are already upon us, and are being felt all over the world,” says Scovronick. “The southeastern United States is no exception. This work provides another reminder of the need to reduce emissions of greenhouse gases and to implement policies to protect the people most at risk.” 

Findings from the dataset revealed that in the United States, 34.7 percent of all heat-related summer deaths during the study period were attributable to anthropogenic climate change. In Atlanta, 24.3 percent of summer deaths from heat over the study period were due to anthropogenic climate change and an average of 19 deaths per year over the study period were attributable to anthropogenic climate change.