- Jun 2014
- Cleveland, Ohio
By 2100, Deadly Heat May Threaten Majority of HumankindA new study has found that 30 percent of the world’s population is currently exposed to potentially deadly heat for 20 days per year or more—and like a growing forest fire, climate change is spreading this extreme heat.
Without major reductions in emissions of greenhouse gases such as CO2, up to three in four people will face the threat of dying from heat by 2100. However, even with reductions, one in two people at the end of the century will likely face at least 20 days when extreme heat can kill, according to the analysis, published on Monday in Nature Climate Change.
“Lethal heatwaves are very common. I don’t know why we as a society are not more concerned about the dangers,” says Camilo Mora of the University of Hawaii at Manoa, the study’s lead author. “The 2003 European heatwave killed approximately 70,000 people—that’s more than 20 times the number of people who died in the September 11 attacks.”
Dangerous heatwaves are far more common than anyone realized, killing people in more than 60 different parts of the world every year. Notable deadly heatwaves include the 2010 Moscow event that killed at least 10,000 people and the 1995 Chicago heatwave, where 700 people died of heat-related causes.
Heatwaves have also claimed victims more recently. In the last two weeks, dozens have died in India and Pakistan’s current heatwave, with temperatures spiking to a record 128 degrees Fahrenheit (53.5 degrees Celsius). And there have been heat-related deaths already in the U.S. this summer.
Mora and an international group of researchers and students examined more than 30,000 relevant publications to find data on 1,949 case studies of cities or regions where human deaths were associated with high temperatures. Lethal heatwaves have been documented in New York City, Washington, D.C., Los Angeles, Chicago, Toronto, London, Beijing, Tokyo, Sydney, and São Paulo.
Those facing the greatest risk live in the wet tropics, where only slight increases in average temperatures or humidity can result in deaths. However, heat can be deadly even at moderate temperatures of less than 86 degrees Fahrenheit (30 degrees Celsius) if it’s combined with very high humidity, Mora ays.
Heat kills ten times more people in the U.S. than tornados or other extreme weather events, says Richard Keller, a University of Wisconsin-Madison professor of medical history.
Extreme heat sneaks up on us because we expect it to be hot in the summer, says Keller, who has written a book on the 2003 European heat wave.
The human body’s internal temperature likes to be between 98.6 to 100.4 degrees Fahrenheit (37 to 38 degrees Celsius); any warmer, and it’s a fever. As temperatures rise, the body reacts by sweating to try and cool down.
If our internal temperature gets close to 104 degrees Fahrenheit (40 degrees Celsius), all-important cellular machinery start to break down. Body temperatures above 104 degrees are extremely dangerous and require immediate medical attention.
If the heat index—a metric that combines temperature and humidity—reaches 104 degrees Fahrenheit (40 degrees Celsius), our bodies begin to slowly heat up to the ambient temperature unless we take action to cool down.