New research has found that Middle America could soon be too hot for humans to live in.
The section of the United States from Florida to New York and Houston to Chicago could get so hot that humans would not be able to withstand the heat if the planet continues to warm past 3 degrees Celsius above pre-industrial levels, according to a study published in the Proceedings of the National Academy of Sciences.
At the Earth's current level of warming, the U.S. will experience heat waves, but they will not surpass human limitations— though some parts of the world will. During the study, scientists looked at five possible warming scenarios if the Earth were to warm beyond 1.5 degrees Celsius above preindustrial levels.
"Among the five scenarios, the intermediate one is most likely and will lead to a warming of 2.1-3.5 degrees Celsius with a median at 2.7 degrees Celsius (compared with pre-industrial period) by the end of this century," Qinqin Kong, a co-author on the study and a doctoral candidate at Purdue University, told Newsweek.
"Recent observations showed that we might do slightly better with a warming between 2 and 3 degrees Celsius. At 2 degrees Celsius warming, only relatively small areas over Pakistan will have over 240 hours of uncompensable heat stress each year, which amounts to one month if you count eight hours for a day," he said. "This is surely a problem since that region is densely populated. But I wouldn't expect heat stress to make any place inhabitable at this level of warming."
At 3 degrees Celsius warming, a large part of the Indus Valley and coastal region of the Persian Gulf and the Red Sea could possibly see over two months and even more than three months of uncompensable heat stress on average every year, Kong said.
"Al Hudaydah, the second-largest city of Yemen, this number reaches up to 160 days. With uncompensable heat of season length on average each year, these regions will become inhabitable, or dramatic lifestyle changes (e.g., staying in the air conditioning room most of the time) are necessary to survive. As 3 degrees Celsius is within the envelope of the most likely warming scenarios, the aforementioned situations are quite likely to happen in my opinion," Kong said.
Humans can only withstand a certain amount of heat and humidity before it becomes a serious problem for their health. Prolonged exposure to extreme heat can cause heat stroke or in severe cases, even heart attacks.
As human-induced climate change continues, the Earth will only continue to warm. Scientists believe it could be only a matter of time before the planet reaches a point beyond the point that a human could withstand.
Deals like the Paris Agreement aim to minimize warming. Since the start of the Industrial Revolution—when humans first began to burn fossil fuels in large numbers—the Earth has warmed by around 1 degrees Celsius, or 1.8 degrees Fahrenheit.
There are some instances where incredibly hot temperatures have already started to affect humans. Scientists reiterate that while models used in the study are good at predicting events, they do not predict specific events. Events like this can include the Oregon heatwave that killed more than 700 people in 2021.
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It also does not seem possible that humans will be able to adapt to these rapidly rising temperatures.
"Evolutionary or genetic adaptation to a changing climate takes many, many generations to develop, much longer than the timescales associated with our current changing climate," Daniel Vecellio, who performed the study as a postdoctoral fellow in the Center for Healthy Aging at Penn State University and postdoctoral scholar at George Mason University's Virginia Climate Center, told Newsweek.
"Based on human's current physiological capabilities, it may be possible for those who live in the regions which are chronically exposed to extreme heat (e.g., South Asia, the Middle East) to develop better biological protection to the heat, but there is still a limit to what they'll be able to withstand. Those living in the mid-latitudes will likely not be exposed to this extreme heat on a consistent enough basis to build up any large or long-lasting physiological protection."
Vecellio said that adaptation for most people will be in the technological sense, such as the use of air conditions. Behavioral adaptations may also be made, for example, the change of working hours to avoid the hottest parts of the day.
"I don't think that it was shocking that with continued warming, we would reach these lower wet-bulb temperature thresholds in more regions across the globe more frequently, but some of the magnitudes of the yearly exposure to uncompensable heat stress were sobering to see," Vecellio said.
"Of course, one would imagine that the summer season would see longer periods of threshold exceedance—but some of the Middle Eastern cities having over 1,000 or 2,000 hours of exposure every year in a 4-degree Celcius warmer world, which, if spread out evenly in 8-hour increments, would mean up to 300 days a year of this seemingly fatal heat stress if no precautions or technological adaptation were to take place—was a distressing result to stomach."
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Correction 10/11/23, 10:22 a.m. ET: This article was updated to take out an incorrect temperature conversion.
