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Massive economic losses due to sweltering temperatures caused by human-caused climate change are not just a problem for the distant future. A study in the magazine Advances in Science has found that the most severe heat waves resulting from global warming have already cost the world economy trillions of dollars since the early 1990s, with the world’s poorest and least carbon-emitting nations suffering the most.

Dartmouth College researchers combined newly available in-depth economic data for regions around the world with the average temperature of the hottest five-day period, a commonly used measure of heat intensity, for each region every year. They found that between 1992 and 2013, heat waves statistically coincided with variations in economic growth, and that $16 trillion was lost due to the effects of high temperatures on human health, productivity and agricultural production.

The findings underscore the immediate need for policies and technologies that protect people during the hottest days of the year, especially in the world’s hottest and most economically vulnerable nations, the researchers report.

“Accelerating adaptation measures in the hottest period of each year would yield economic benefits now,” said the first author Christopher Callahan, PhD candidate in geography at Dartmouth. “The amount of money spent on adaptation measures should not be assessed only by the price of those measures, but in relation to the cost of doing nothing. Our research identifies a substantial price for doing nothing.”

The study is the first to specifically examine how heat waves affect economic output, the lead author said Justin Mankinassistant professor of geography at Dartmouth. “No one has shown an independent fingerprint for extreme heat and the intensity of the impact of that heat on economic growth. The true costs of climate change are much higher than we’ve calculated so far,” Mankin said. .

“Our work shows that no site is well adapted to our current climate,” Mankin said. “Lower-income regions of the world suffer the most from these extreme heat events. As climate change increases the magnitude of extreme heat, it is a fair expectation that these costs will continue to accumulate.”

Climate models and previous research have included heat waves among other extreme events resulting from climate change, such as more frequent flooding and increased storm intensity, Callahan said. But heat waves have a unique signature, he said. They occur on shorter timescales than droughts, and temperatures on the hottest days of the year are projected to rise much faster than global average temperatures as human activity continues to drive climate change.

“Heat waves are one of the most direct and tangible effects of climate change that people feel, but they have not been fully integrated into our assessments of what climate change has cost and will cost in the future,” he said Callahan. “We live in a world that has already been altered by greenhouse gas emissions. I think our research helps prove that.”

The study’s findings underscore issues of climate justice and inequality, Mankin and Callahan said. The economic costs of extreme heat, as well as the cost of adaptation, have been and will be borne disproportionately by the world’s poorest nations in the tropics and the Global South. Most of these countries have contributed less to climate change.

The researchers found that while economic losses from extreme heat events averaged 1.5% of gross domestic product (GDP) per capita for the wealthiest regions of the world, regions of low income suffered a loss of 6.7% of GDP per capita. In addition, the study revealed that, to some extent, rich sub-national regions in Europe and North America, which are among the world’s largest carbon emitters, could theoretically benefit economically from having periods of longer days warm

“We have a situation where the people who are causing global warming and changes in extreme heat have more resources to be resilient to those changes and, in some rare cases, could benefit from it,” Mankin said. “It is a massive international transfer of wealth from the poorest countries in the world to the richest countries in the world through climate change, and this transfer must be reversed.”

In July, Mankin and Callahan published a paper in the journal Climate change which assessed the economic damage that individual countries have caused to others through their contributions to climate warming. The study presented the scientific basis that nations need to assess their legal ability to claim economic damages due to emissions and warming.

In this latest publication, Mankin and Callahan indicate that the world’s major emitters should foot large portions of the bill for adapting to extreme heat events, as well as helping low-income nations develop low-emission economies. In the global economy, sharing the costs of adaptation measures would benefit both rich and developing nations, Mankin said.

“Almost no country on Earth has benefited from the extreme heat that has occurred,” Mankin said. “Global events such as the COVID-19 pandemic have revealed the close interconnectedness of the supply chain and the global economy. Low-income countries have a disproportionate number of outdoor workers who often generate raw materials so crucial to the global supply chain – there is absolutely the potential for dominant upstream effects.”

The paper, “Global Uneven Effect of Extreme Heat on Economic Growth,” was published on October 28, 2022 by Science Advances. The research was funded by a National Science Foundation Graduate Research Grant (No. 1840344); the Wright Center for the Study of Computation and Just Communities at Dartmouth’s Neukom Institute for Computational Science; and the Nelson A. Rockefeller Center.

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