Two new studies out today in The Lancet Planetary Health reveal the stark reality of climate-related mortality, showing that rising temperatures as a result of climate change will lead to a future spike in temperature-related deaths.
The first study, led by Monash University’s Yuming Guo, looked at mortality and temperature data across the world from 2000 to 2019, a period when global temperatures rose by 0.26°C per decade.
The data reveals a complex trajectory: as global temperatures rose, cold-related deaths decreased by 0.51% over the 19-year period, but heat-related deaths increased by 0.21%. This means an overall net reduction in mortality but, critically, as temperatures continue to rise, it’s predicted that so too will heat-related deaths.
Professor Guo says that while this shows global warming may “slightly reduce the number of temperature-related deaths, largely because of the lessening in cold-related mortality, in the long-term, climate change is expected to increase the mortality burden because hot-related mortality would be continuing to increase”.
Key research points
- More than half of global deaths attributed to abnormal cold or hot temperatures occurred in Asia, particularly in East and South Asia
- Europe had the highest excess death rates per 100,000 due to heat exposure
- Sub-Saharan Africa had the highest death rates per 100,000 due to exposure to cold.
Guo says previous studies have tended to focus on trends in one particular country or region, but understanding the geographic patterns of temperature-based mortality is important to help develop global policy on the issue.
“This is the first study to get a global overview of mortality due to non-optimal temperature conditions between 2000 and 2019, the hottest period since the pre-industrial era,” he says.
“Importantly, we used 43 countries’ baseline data across five continents with different climates, socioeconomic and demographic conditions and differing levels of infrastructure and public health services, so the study had a large and varied sample size, unlike previous studies.”
The second study, by the Barcelona Institute for Global Health (ISGlobal), analysed European data from 1998 to 2012, concluding that more than 7% of all deaths registered during the period could be attributed to temperature, and that cold temperatures had a greater impact on mortality than warm temperatures by a factor of 10.
Using the collected data, the team combined four climate models to make projections through to the end of the century under three different greenhouse-gas-emission scenarios. It found – in line with the Monash University study – that while temperature-related deaths were currently in decline, they would begin to climb again as the climate continues to warm.
“All of the models show a progressive increase in temperatures and, consequently, a decrease in cold-attributable mortality and an increase in heat-attributable deaths,” says ISGlobal researcher Èrica Martínez, lead author of the study.
“The difference between the scenarios lies in the rate at which heat-related deaths increase. The data suggest that the total number of temperature-attributable deaths will stabilise and even decrease in the coming years, but that this will be followed by a very sharp increase, which could occur sometime between the middle and the end of the century, depending on greenhouse gas emissions.”
The authors warn that swift global mitigations are required to manage the future scale of the problem and prevent a mortality boom.
“Our findings underscore the urgency of adopting global mitigation measures, since they will not be effective if they are only adopted in specific countries or regions,” says researcher Joan Ballester, co-author of the ISGlobal study. “Moreover, one decisive factor not included in our models is our capacity to adapt to new scenarios, which is already helping to reduce our vulnerability to temperatures.”
Amalyah Hart is a science journalist based in Melbourne.
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