Heatwaves brought on by human-caused climate breakdown have cost the global economy about $16tn since the 1990s, according to a study.
The research calculates the financial impact of extreme heat on infrastructure, agriculture, productivity, human health and other areas.
“We have been underestimating the true economic costs we’ve suffered because of global warming so far, and we are likely underestimating the costs going out into the future,” said Justin Mankin, an assistant professor of geography at Dartmouth College and senior author of the study published in the journal Science Advances.
Despite having the lowest carbon emissions, it is the tropics and the global south that bear almost the entirety of the economic brunt of extreme heat. This is because they are warmer and therefore hit harder by heatwaves, and also because they are more economically vulnerable and therefore more susceptible to economic depression and the costs of adapting to the climate crisis.
Using data covering about 66% of the world’s population, the researchers examined temperature measurements from the hottest five-day periods of the years between 1992 and 2013 and compared them with national economic data from that same period, segmented for regions.
Extreme heat had a wide range of effects on people and economies, said Christopher Callahan, a researcher at Dartmouth College and lead author of the study. “We know that heatwaves kill crops and cause illnesses like heat stroke, but they also have other effects such as increased interpersonal aggression, increased rates of workplace injury, and reduced mental performance.”
Until recently, most studies on the subject were based on averages, but these can mask the effects of local and temporary events, according to Dr Leonie Wenz, the deputy head of the research department on complexity science at the Potsdam Institute for Climate Impact Research, who was not involved in the study.
“They do not fully reflect how we as humans experience temperature. What really matters for us, what affects our wellbeing, our productivity, and our decisions are the extremes and the fluctuations from one day, or week, to the next.”
The study found that the world’s wealthiest regions, such as areas of Europe and North America, experienced an average 1.5% loss of GDP per capita per year due to extreme heat. By comparison, low-income regions – such as India and Indonesia – recorded a 6.7% GDP per capita loss yearly.
The bill had been footed mainly by countries that had not benefited from industrialisation, said Mankin, creating a vicious cycle.
“Low-income countries have been asked to develop and industrialise in a global economy that strategically disadvantages them,” he said. “And they’re doing so while also being hammered by the impacts of global warming that has been generated by the global north. It’s kind of a double whammy.”