Half the World’s Population Will Experience Deadly Heat by the End of the Century

And Arizona is kicking things off

Phoenix Sunset
Fasten your seatbelts for record heat, Phoenix—just don't burn yourself while you're at it. midiman - Flickr/Creative Commons

Heat waves aren’t just uncomfortable, they’re downright dangerous. But how likely is your area to experience heat that gets into the deadly range? The risk may be higher than you thought, and as Oliver Milman reports for The Guardian, it’s growing. A new study suggests that by the end of the century, half of the world's population will suffer from deadly heat waves.

Already, 30 percent of people are at risk for deadly heat, according to a new study published in the journal Nature Climate Change. The researchers analyzed lethal heat events over a 34 year period and used that data to create a threshold for when heat is deadly. After studying 783 cases of what they call “excess human mortality” from heat events, they pinpointed heat waves to 164 cities in 36 countries. Then they assessed climate conditions like wind speed, surface air temperature and relative humidity in those locations.

Armed with profiles of what constitutes deadly heat in different areas, the researchers looked to the future using models of a climate with low, moderate and high greenhouse gas emissions. The results were grim. Even under a scenario that included aggressive greenhouse gas reductions, they found that by 2100, nearly 27 percent of Earth’s land will be at risk of deadly heat more than 20 days of the year, exposing roughly 48 percent of the global population to these soaring temperatures. And the higher the emissions, the more severe the heat. Under higher emissions they estimate that by 2100 up to 47 percent of Earth's land and nearly 74 percent of the world's populations will be at risk of deadly heat waves.

Unfortunately, that scenario is already reality for much of the world. Take Arizona, where record temperatures are expected through Sunday. According to the National Weather Service, a large swath of the state is expected to hit “rare, dangerous, and very possibly deadly” temperatures of up to 122 degrees. Airline operators have begun canceling flights since temperatures are expected to exceed maximum operating thresholds for aircraft, and burn specialists are even warning of second- and third-degree burns from everything from hot car interiors to sun-baked hoses.

Warnings like that could increase the number of people who survive a deadly heat event, the researchers say. But they warn that the human body is unlikely to ever develop a better heat tolerance—especially given a rapidly changing climate. Extreme climate events are already happening more rapidly as Earth’s atmosphere warms. According to a group of researchers from the National Center for Atmospheric Research, all weather is now influenced by climate change. Humans can still slow the pace of change by reducing greenhouse gas emissions, but you might want to stock up on some ice cubes (and review some basic heat safety tips) while you’re at it.