Heat waves caused by climate change have cost the global economy trillions since the 1990s

The huge economic losses due to cold temperatures caused by human-caused climate change are not just a problem for the distant future. Study in magazine Scientific progress found that more severe heat waves as a result of global warming have already cost the global economy trillions of dollars since the early 1990s – with the world’s poorest, least carbon-emitting nations suffering the most.

Dartmouth College researchers combined newly available, in-depth economic data on regions around the world with the average temperature for the hottest five-day period — a commonly used measure of heat intensity — for each region in each year. They found that from 1992-2013, heat waves statistically coincided with variations in economic growth, and that about $16 trillion was lost 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 warmest and most economically vulnerable nations, the researchers report.

“Accelerating adaptation measures within the hottest period of each year would bring economic benefits now,” said first author Christopher Callahan, a doctoral student in geography at Dartmouth. “The amount of money spent on adaptation measures should not be judged only on the basis of the cost of those measures, but on the cost of inaction. Our research identifies a significant cost of doing nothing.”

The study is among the first to specifically examine how heat waves affect economic output, said senior author Justin Mankin, an assistant professor of geography at Dartmouth. “Nobody has shown an independent footprint 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 estimated so far,” Mankin said.

“Our work shows that no one place is well adapted to our current climate,” Mankin said. “It is the lowest-income regions globally that suffer the most from these extreme heats. As climate change increases the scale of extreme heat, it is fair to expect that these costs will continue to accumulate.”

Climate models and previous research include heat waves among other extreme events resulting from climate change, such as more frequent flooding and greater storm intensity, Callahan said. But heat waves have a unique signature, he said. They occur on a shorter timescale than droughts, and temperatures on the hottest days of the year are expected to rise much faster than the average global temperature 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 are not fully integrated into our estimates of what climate change has cost and will cost in the future,” Callahan said. “We live in a world that has already been changed by greenhouse gas emissions. I think our research helps to prove that.”

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

The researchers found that while economic losses due to extreme heat averaged 1.5% of gross domestic product (GDP) per capita for the world’s wealthiest regions, low-income regions suffered a loss of 6.7% of GDP per head of population. The study also revealed that at some point, rich sub-national regions in Europe and North America, which are among the world’s biggest carbon emitters, could theoretically benefit economically by experiencing periods of warmer days.

“We have a situation where the people causing global warming and changes in extreme heat have more resources to be resilient to those changes, and in some rare cases they could take advantage of that,” Mankin said. “This is a massive international transfer of wealth from the world’s poorest countries to the world’s richest countries through climate change – and this transfer must be reversed.”

In July, Mankin and Callahan published an article in the journal Climate change which estimates the economic damage that individual countries have caused to others through their contribution to climate warming. The study provided the scientific basis nations need to assess their legal standing to claim economic damages due to emissions and warming.

In this latest publication, Mankin and Callahan point out that the world’s major emitters should shoulder much of the bill for adapting to extreme heat, in addition to helping lower-income nations develop low-emission economies. In a 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 the raw materials so important to the global supply chain – there is absolute potential for upward ripple effects.”

The report “The Globally Uneven Effect of Extreme Heat on Economic Growth” was published on October 28, 2022 in Scientific progress.