Washington (AFP) - Heat waves intensified by climate change have cost the global economy trillions of dollars in the past 30 years, a study published Friday showed, with poor countries paying the heaviest price.

Likewise, these unbalanced economic effects contribute to widening inequalities around the world, according to the study.

"The cost of extreme heat waves caused by climate change has so far been disproportionately borne by countries and regions that are least responsible for climate warming," Justin Mankin, a professor at Dartmouth College and one of the authors of the study published in the journal Science Advances, told AFP. ".

"Climate change comes at a time when economic inequality prevails in the world, and is exacerbating it," he added.

The study showed that periods of extreme heat waves between 1992 and 2013 cost the global economy about $16 trillion.
But while rich countries lost about 1.5 percent of their annual per capita GDP while dealing with heatwaves, poor countries lost about 6.7 percent of their annual per capita GDP.

The reason for this disparity is simple, and it is due to the fact that poor countries are often located near the tropics, which naturally makes their climate warmer. During heat waves, it gets exceptionally hot.

This study was published days before the start of the Climate Summit (COP 27) in Sharm El-Sheikh, Egypt, where it is expected that the issue of compensating the countries most vulnerable to the repercussions of climate change, despite being the least responsible for this phenomenon, will be one of the main topics.

The costs of heatwaves come from many factors: the fallout on agriculture, strained health systems, a less productive workforce, and damage to infrastructure, such as melting roads.

The researchers involved in the study focused on the five hottest days each year in certain regions where extreme heat waves are considered extreme weather phenomena.

"The general idea is to look at the differences in temperature extremes (...) and see how much that is reflected in the differences in economic growth" for each region, Mankin said.

"Then, in the next step, we look at how human-caused climate change affects these temperature extremes," he added.

But the results of the study almost certainly underestimate the true cost of extreme heat waves, according to the research, as studying only five days a year does not reflect the increasing frequency of these climatic phenomena, and not all potential costs are included.

Previous studies on this topic have focused on the costs of heatwaves in specific sectors, although scientists say it is important to look at the costs of climate change comprehensively.

"You want to know what those costs are so that you have a frame of reference against which to compare the cost of taking action," Mankin said, for example setting up cooling centers or installing air conditioners against "the cost of inaction."

"The economic gains from responding to the five hottest days of the year could be enormous," he added.

But Mankin noted that the most important response is to reduce greenhouse gas emissions to slow climate warming at the source.
"We must adapt to the climate in which we live now, and we must invest heavily to combat climate change," he concluded.