New study: Dangerous heat set to strike 3 times more often in future as climate change worsens


According to a new study, what is officially considered “dangerous heat” in the coming decades will likely affect much of the world at least three times more often as climate change worsens.

In most of Earth’s rich mid-latitudes, temperature and humidity spikes that look like 103 degrees (39.4 degrees Celsius) or higher — now an occasional summer shock — are statistically predicted to occur 20 to 50 times a year. by mid-century, according to a study Monday in the journal Communications Earth & Environment.

By 2100, this brutal heat index could persist for most of the summer in places like the southeastern United States, the study author said.

And it’s much worse for the sticky tropics. The study said a heat index deemed ‘extremely dangerous’ where the felt heat index exceeds 124 degrees (51 degrees Celsius) – now something that rarely happens – will likely hit a tropical belt that includes India one to four weeks per year per century. end.

“So it’s a little scary about that,” said study author Lucas Zeppetello, a Harvard climatologist. “This is something where potentially billions of people are going to be exposed to extremely dangerous levels of heat on a very regular basis. So something that has gone from hardly ever before is going to be something that happens every year.”

Zeppetello and his colleagues used more than 1,000 computer simulations to examine the probabilities of two different levels of high heat – heat indices of 103 degrees (39.4 Celsius) and above 124 degrees (51 Celsius), which are dangerous and extremely dangerous thresholds according to the United States National Weather Service. They calculated for the years 2050 and 2100 and compared that to how often this heat occurred each year around the world from 1979 to 1998.

The study found a three to 10-fold increase in 103-degree heat at mid-latitudes, even under the unlikely best-case scenario of global warming limited to just 3.6 degrees (2 degrees Celsius) since pre-industrial times. – the less stringent of two international objectives.

According to the study, there is only a 5% chance that the warming will be so weak and so infrequent. What’s more likely, the study says, is that 103-degree heat will engulf the tropics “for most days of every typical year” by 2100.

Chicago only hit that 103-degree heat index level four times between 1979 and 1998. But the study’s most likely scenario shows Chicago hitting that hot, sticky threshold 11 times a year by the end of the year. end of the century.

Heat waves are one of the four new horsemen of apocalyptic climate change, along with rising sea levels, water scarcity and changes in the global ecosystem, said Zeppetello, who has conducted a large part of research at Washington State University during the warming-laden heat of 2021. wave that broke records and killed thousands.

“Unfortunately, the horrific predictions presented in this study are credible,” climatologist Jennifer Francis of the Woodwell Climate Research Center, who was not part of the study team, said in an email. “The past two summers have opened a window into our scorching future, with deadly heat waves in Europe, China, northwestern North America, India, the south-central United States , in the UK, central Siberia and even New England are becoming uninhabitable as heat indices rise above dangerous thresholds, affecting both humans and ecosystems Areas where extreme heat is now rare will suffer also more and more, because the infrastructures and the living beings are unsuited to the crushing heat.

The study focuses on the heat index and that’s smart because it’s not just the heat but the combination with the humidity that is detrimental to health, said Harvard School professor Dr. Renee Salas of Public Health and emergency physician.

“As the heat index increases, it becomes increasingly difficult to cool our bodies,” Salas, who was not part of the research team, said in an email. “Heat stroke is a potentially fatal form of heat illness that occurs when body temperature reaches dangerous levels.”

The study is based on mathematical probabilities instead of other climate research that looks at what happens to different levels of carbon pollution. For this reason, University of Pennsylvania climatologist Michael Mann is more skeptical of this research. It also ignores landmark US climate legislation that President Joe Biden signed earlier this month or new efforts from Australia, he said.

“The obstacles at this point are political and no statistical method, no matter how powerful or sophisticated, can predict whether we will muster the political will to overcome them,” Mann said in an email. “But there is reason to be optimistic and cautious.”

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