Poor countries may lose 10 times more people to deaths from high temperatures than rich ones, according to an analysis by Climate Impact Lab.
The research, published on March 25, is designed to help cities and communities understand and respond to the dangers they face from rising temperatures.
It comes as a record-breaking heat wave grips much of the US and as more evidence emerges that global warming is accelerating. While the rising heat is global, its consequences for health vary dramatically depending on affluence.
“I continue to be shaken by the inequality of climate change,” said Dr Michael Greenstone, a University of Chicago economist who co-authored the report and who co-directs Climate Impact Lab, a collaboration among researchers focused on emerging risks.
“The extra deaths are all going to occur in places that contributed very little” to greenhouse gas emissions that are warming the atmosphere.
The new report projects that by 2050, vulnerable countries will see an increase in heat-related deaths equivalent to current fatalities from common diseases.
Niger, Burkina Faso and other countries in Africa’s Sahel region could see 60 or more deaths a year per 100,000 people – a rate higher than the current one for malaria in Africa.
About 55 people per 100,000 die of HIV/AIDS in Djibouti; it might experience a commensurate rise in heat-related mortality. In south-eastern Bolivia, the death rate could rise by 30 people per 100,000, or about the current rate from diabetes.
Some cold climates will see a drop in heat-related deaths. North-eastern Russia’s New Siberia Islands could register the biggest decline in the mortality rate – 161 fewer per 100,000 people – although not many people actually live there.
Other places in rich countries also benefit, including the North Slope of Alaska, Banff, Canada and Oslo.
All but two of the 20 countries with the biggest net improvements are higher income, and 16 of the 20 countries facing the most new deaths are lower income.
The report is not itself peer reviewed, but its methodology, developed several years ago, was reviewed and published in an economics journal in 2022. The group’s initial work focused on the rise in heat mortality by 2100, and demonstrated in detail the relationship between wealth, temperature and risk.
“Alarm bells are ringing,” said Dr Cascade Tuholske, a geographer at Montana State University who works on climate risk.
“Mortality rates will continue to rise due to extreme heat that is being driven by carbon emissions, by fossil fuels. The burden is falling on those who have the fewest resources to adapt and the people who are not causing this problem, by and large.”
To Dr Tuholske, who was not involved with the study, it appropriately highlights places that face increasingly dangerous conditions but are not widely understood to be among the most vulnerable.
Pakistan is already dealing with other severe climate impacts, such as historic floods in 2022; the country’s dense cities and an economy dependent on outdoor labour mean that its heat risks are significant and chronic, said Dr Tuholske.
“For me, that’s always been a country of concern, just looking at global climate projections in extreme heat,” he said.
The authors’ approach relies on breaking the whole world down into small units, about the size of a US county or a district in China or India – nearly 25,000 of them. This granularity shows how neighbouring regions, even within the same countries, can face very different futures.
Sometimes differences are easily explained by geography.
Communities in the Rocky Mountains of the US may see dozens fewer deaths a year by 2050 amid warming winters, while to the south and south-west, heat is more likely to claim lives every year.
The research makes clear how wealth inequality will increasingly become a life or death issue. Djibouti’s projected higher mortality rate is more than twice that of Kuwait’s, which sits across the Arabian Peninsula.
The study assumes that the world economy will continue to grow. Otherwise, there would be seven times more temperature-related deaths. The additional income will allow people to buy ways to adapt – air conditioners, shelters, parks and other cooling measures – saving additional lives.
The trouble is, funding and attention are always in short supply.
“These deaths don’t have to be inevitable,” said Ms Emily Grover-Kopec, a report co-author and a director in the climate and energy practice of the research firm Rhodium Group.
The report “provides a map for where income growth alone will not be enough and where deliberate adaptation policy and investments can save the most lives.” BLOOMBERG