More than a third of heat-related deaths in many parts of the world can be attributed to the global warming associated with climate change, a new study calculating the human cost of climate change claims.
According to the study published in the journal, Nature Climate Change, dozens of researchers who looked at heat deaths in 732 cities around the globe from 1991 to 2018 calculated that 37% were caused by higher temperatures from human-caused warming.
The study's lead author said that the figure amounts to about 9,700 people a year from just those cities adding that the figure would be much more worldwide.
The shocking facts from the study has now made a case for taking strong action to reduce greenhouse gas emissions in order to protect public health.
According to the scientists, the figure is only a sliver of climate's overall toll.
The study reveals that more people die from other extreme weather amplified by global warming such as storms, flooding and drought — and the heat death numbers will grow exponentially with rising temperatures.
Ana Vicedo-Cabrera, an epidemiologist at the Institute of Social and Preventative Medicine observed that these deaths related to heat that can actually be prevented as it is something we directly cause by our actions.
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.
Sao Paulo, Brazil, has the most climate-related heat deaths, averaging 239 a year, researchers found.
About 35% 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%.
Scientists used decades of mortality data in the 732 cities to plot curves detailing how each city's death rate changes with temperature and how the heat-death curves vary from city to city. Some cities adapt to heat better than others because of air conditioning, cultural factors and environmental conditions, Vicedo-Cabrera said.
Then researchers took observed temperatures and compared them with 10 computer models simulating a world without climate change. The difference is warming humans caused. 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.
"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.