Rising heat-related deaths linked to global warming

Claudia Caruana

Using empirical data gathered from 732 locations, researchers estimated the mortality burdens associated with additional heat exposure resulting from human-induced warming from 1991 to 2018.

An international team of researchers has quantified how heat-related deaths are attributable to global warming, with Latin America and South-East Asia the worst hit.

Ana Maria Vicedo-Cabrera, lead author and head of the Climate Change and Health Research Group at the Institute of Social and Preventive Medicine, University of Bern, says across 43 countries an average of 37 per cent of warm-season heat-related deaths could be attributed to anthropogenic climate change.

Increased mortality was evident on every continent, the highest being in Central and South America (up to 76 per cent in Ecuador and Columbia) and South-East Asia (up to 61 per cent).

Using empirical data gathered from 732 locations, researchers estimated the mortality burdens associated with additional heat exposure resulting from human-induced warming from 1991 to 2018.

The two-step study, led by the London School of Hygiene and Tropical Medicine and the University of Bern, Switzerland, was published in Nature Climate Change.

In the first step, time series regression techniques were used to observe temperature and mortality, with data collected through the Multi-Country Multi-City (MCC) Collaborative Research Network — a large weather and health data consortium.

In the second step, researchers used estimated exposure-response (response to an environmental condition within a given time) to compute heat-related mortality for each location over the 27-year period.

“We already have performed research on the impacts of heat, both on current times and future projections.  However, in this analysis we decided to go further and quantify the percentage of the historical burden that can be directly attributed to human-induced climate change,” Vicedo-Cabrera says.

She adds: “We found larger percentages of contribution of human induced climate change in countries in South/Central America and West/South-East Asia – these countries suffered a larger increase in temperature and they also showed to be more vulnerable.”

“We found larger percentages of contribution of human induced climate change in countries in South/Central America and West/South-East Asia – these countries suffered a larger increase in temperature and they also showed to be more vulnerable.”

Ana Maria Vicedo-Cabrera, University of Bern

“Our findings support the urgent need for more ambitious mitigation and adaptation strategies to minimise the public health impacts of climate change,” she emphasises.

Antonio Gasparrini, a professor at the London School of Hygiene and Tropical Medicine and senior author of the MCC Network tells SciDev.Net that the negative environmental and ecological signals of climate change are already well evidenced. “The increase in extreme weather events, the melting of the polar ice caps and sea-level rise, or coral bleaching have been frequently reported and linked to global warming,” he says.

In contrast, he adds, “most of the scientific studies assessing effects of climate change on human health focus on future impacts projected in the future. This is one of the few studies — the first with a global scope — that measures increased health risks of climate change in the historical period, and the message is clear: climate change will not just have devastating impacts in the future, but every continent is already experiencing the dire consequences of human activities on our planet.”

Aaron Bernstein, interim director of The Center for Climate, Health, and the Global Environment, Harvard T.H. Chan School of Public Health, notes that the poorest, especially those in tropical nations, are the most vulnerable to the effects of climate change.

“We knew that extreme heat results in early death. This showed us — at a global scale — how much climate change has grown risk of death from heat,” he says. “Where people die of heat has much to do with how much they can afford to protect themselves from it. The results in Asia, Southern Europe, and the global South make clear that health risks from climate are happening in places that historically have had little to do with causing climate change.”

Bernstein says the study suggests that the risk of heat death by climate change has grown by more than one third in almost 30 years. “To make sure that this trend doesn’t continue, we must meet the scientific targets to reduce greenhouse gas emissions and get fossil fuels out of our economies. We also need to do much more to keep people safe from heat,” he adds.

Vicedo-Cabrera concludes: “Our findings suggest that more ambitious mitigation strategies and efficient adaptation measures are urgently needed to attenuate future impacts of climate change.”

The researchers acknowledged limitations in their work such as inability to include large parts of Africa and South Asia, due to a lack of empirical data.

This piece was produced by SciDev.Net’s Asia & Pacific desk.