In the last three decades, global warming has been responsible for 37 percent of heat-related deaths across the globe, according to researchers who say their finding is a reminder that climate change is already having severe impacts.
But that one-in-three number is only a sliver of the overall death toll. Researchers claim that even more people die from climate-related events, such as floods, avalanches, storms, droughts, and wildfires – and the numbers will grow exponentially as the temperatures rise.
Dozens of researchers from around the globe used temperature and mortality data from 732 cities in 43 countries between 1991 and 2018, to come to their estimation of climate-linked heat deaths. The scientists then compared them with 10 computer models simulating a world without climate change.
The difference is the warming caused by humans. By applying that scientifically accepted technique to the individualized heat-death curves for the 732 cities, the scientists calculated extra heat deaths from climate change, reports NBC News. Their results were published Monday in the online journal, Nature Climate Change.
“People continue to ask for proof that climate change is already affecting our health. This attribution study directly answers that question using state-of-the-science epidemiological methods, and the amount of data the authors have amassed for analysis is impressive,” said Dr. Jonathan Patz, director of the Global Health Institute at the University of Wisconsin.
Chloe Brimicombe at the University of Reading, UK, who wasn’t involved in the research, says the study is timely – especially with the record-breaking temperatures already being seen in cities around the world this month. “It also shows how quicker action in the past to limit emissions would have led to fewer heat-related deaths,” she says, reports New Scientist.
The number of people who suffered heat-related deaths in those 732 cities comes to 9,700 people. “These are deaths related to heat that actually can be prevented. It is something we directly cause,” said lead author Ana Vicedo-Cabrera, an epidemiologist at the Institute of Social and Preventative Medicine at the University of Bern in Switzerland, according to the Associated Press.
The highest percentages of heat deaths caused by climate change were in cities in South America. Vicedo-Cabrera pointed to southern Europe and southern Asia as other hot spots for climate change-related heat deaths.
São Paulo, Brazil, has the most climate-related heat deaths, averaging 239 a year, researchers found.
About 35 percent of heat deaths in the United States can be blamed on climate change, the study found. That’s a total of more than 1,100 deaths a year in about 200 U.S. cities, topped by 141 in New York. Honolulu had the highest portion of heat deaths attributable to climate change, 82 percent.
Friederike Otto at the University of Oxford, who has studied the lack of data on heat waves and deaths in Africa, says it matters a great deal that much of the world map is missing in the study.
“In most countries in the world, heatwaves are not recorded at all,” she says. “This paper shows we do not have enough data and, importantly, awareness, to quantify the impacts of climate change on lives.” And that is a good point, and one that should be followed up on, because we know that worse is coming in the future.