Low-income countries lose almost 7 per cent of their GDP to heatwaves

Short spells of extreme heat can be enough to lower a region’s economic output for an entire year, according to a new analysis showing the unequal impact of global warming

By Luke Taylor

Periods of extremely hot weather cost the global economy an estimated $16 trillion between 1992 and 2013, while hitting the poorest countries four times as hard as the richest ones.

“Our work reveals that we have underestimated both the costs of climate change so far and how sensitive our economy is at present to climate variations,” says Justin Mankin at Dartmouth University in New Hampshire.

Previous studies have shown that climate change hits the poorest nations hardest, despite them contributing the least to climate change. This is partly because many low-income countries are in the tropics and have a hotter climate to begin with.

New data on economic growth allowed Mankin and Christopher Callahan, also at Dartmouth University, to look at the impact of extreme heat at a regional level and use models to fill in the data in parts of Africa and Asia where figures were missing.

Their analysis reveals that short spells of extreme heat were significant enough to lower a region’s economic output for the entire year.

An annual increase in the temperature of the five hottest days of a year reduced economic growth in tropical regions by as much as a percentage point.

Nations with the lowest income were estimated to have lost 6.7 per cent of their GDP between 1992 and 2013 due to heatwaves, while regions in the top income level lost only 1.5 per cent.

The acute economic disruption in tropical regions during heatwaves is probably caused by crop production and labour productivity dropping while mortality rates increase, the researchers say.

“The countries in the tropics that are experiencing the largest changes in extreme heat also have the economies that produce a lot of the types of goods and services that make them vulnerable to that extreme heat,” says Mankin.

Heatwaves also destroy infrastructure, melting roads and warping train tracks, while causing the power systems that cool buildings to burn out.

“This huge inequity is emblematic of global warming’s larger agenda. These countries are the least culpable for global warming, yet they are the ones most impacted by these extreme heat changes economically,” says Mankin.

The outsized effects of short spells of extremely hot weather mean that efforts to adapt to climate change may have to be centred on heatwaves rather than all-year-round temperature changes, says Callahan.

City planners will increasingly have to consider how their designs will fare during extremely hot spells, while local authorities may have to introduce temporary measures, such as converting public spaces into cooling centres.

“Investment strategies that make us resilient to the hottest days of the year could pay big dividends for economic growth and therefore resilience to other consequences of climate change,” says Callahan.

The study only looked at increases in extreme temperatures, not their growing frequency, so the researchers’ estimates “are likely a floor rather than a ceiling”, says Mankin. “We don’t have a great handle on the aggregate economic costs of all of the things that climate change is going to do to our daily lives, our economies and our well-being.”

Journal reference: Science Advances, DOI: 10.1126/sciadv.add3726

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