Study tallies heatwave deaths over recent decades

Heatwaves, periods of extremely high ambient temperature that last for a few days, can impose overwhelming thermal stress on the human body. Studies have previously quantified the effect of individual heatwaves on excess deaths in local areas, but have not compared these statistics around the globe over such a prolonged period.

In the new study, researchers used data from the Multi-Country Multi-City (MCC) Collaborative Research Network that included daily deaths and temperatures from 750 locations across 43 countries. With the MCC data, the researchers estimated excess heatwave deaths around the world spanning 1990 to 2019 and mapped the variance in these deaths across continents.

During the warm seasons from 1990 to 2019, heatwave-related excess deaths accounted for 153,078 deaths per year, a total of 236 deaths per ten million residents or 1% of global deaths. While Asia had the highest number of estimated deaths, Europe had the highest population-adjusted rate, at 655 deaths per ten million residents. A substantial burden of estimated deaths was seen in southern and eastern Europe as well as the area between Northern Africa, the Arabian Peninsula and Southern Asia. At the national level, Greece, Malta, and Italy had the highest excess death ratios. Overall, the largest estimated rates of heatwaves deaths were seen in areas with dry climates and lower-middle incomes. Understanding the regional disparity of heatwave-related mortality is key to planning local adaptation and risk management towards climate change.

"Heatwaves are associated with substantial mortality burden that varies spatiotemporally over the globe in the past 30 years," the authors say. "These findings indicate the potential benefit of government actions to enhance health sector adaptation and resilience, accounting for inequalities across communities."

The authors add, "In the context of climate change, it is crucial to address the unequal impacts of heatwaves on human health. This necessitates a comprehensive approach that not only tackles immediate health risks during heatwaves but also implements long-term strategies to minimize vulnerability and inequality. The strategies include: climate change mitigation policy, heat action plans (e.g., heat early warning system), urban planning and green structure, social support program, healthcare and public health services, education awareness, and community engagement and participation."