Heat mortality: thousands at risk

09 June 2019

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If countries increase their commitment to climate action, large cities could prevent thousands of heat related deaths every year...

A new study of heat-related deaths claims that lives could be directly saved if countries keep to the Paris Agreement. But it also shows that the world is currently on track to go more than a degree over the target.

Scientists from the University of Bristol created models of how temperature affects mortality for fifteen major US cities. They then combined these models with predictions about how temperatures will rise in the future.

The results show an annual reduction in deaths of up to a couple thousand per city, if global warming is limited to 2°C - and a similar decrease again if the limit is 1.5°C. According Eunice Lo, lead author on the study, this is a substantial number.

“The long-term temperature goal within the Paris Agreement is to limit global warming to well below 2°C above pre-industrial times, with an ambition to further limit it to 1.5°C. Based on the current climate commitments that the nations have made, we are probably heading toward 3°C.”

These national commitments are called Nationally Determined Contributions, and the Paris Agreement contains a mechanism for countries to “ratchet up” those contributions. Lo and her colleagues say this is a necessity.

Previous studies of climate change have looked at risks like sea level rise and extreme weather, but heat alone is a serious danger as well. Heatstroke, and heart problems induced by heat, already kill tens of thousands of people worldwide.

To study the effects of 3°C warming on public health, University of Bristol scientists collaborated with the London School of Epidemiology and Tropical Medicine, who provided the data. The research is partly funded by the Union of Concerned Scientists, a US-based science and advocacy group - which is one reason why they focused on US cities.

They found that results range widely between the different locations. Mitigating global warming to 2°C prevented 70-1980 annual deaths, depending on the city; and mitigating to 1.5°C prevented 110-2720 deaths.

What’s more, these may be conservative numbers. The research didn’t account for population growth, or for a higher proportion of elderly people in the future - both of which may mean a higher death toll.

But, on the other hand, Lo says there are ways cities could adapt and save lives. “If we have an improved healthcare system, or a better early warning system of heatwaves or extreme high temperatures, then the estimated heat-related mortality could reduce.”

“The takeaway message here is that, in addition to mitigating climate change in terms of increasing national and international climate action within the Paris Agreement, regional adaptation is also very important.”

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