CREDIT: Shutterstock Abu Dhabi, capital of the United Arab Emirates.

This summer, a heat wave sent temperatures near the Persian Gulf skyrocketing, with outdoor temperatures reaching as high as 120°F throughout parts of Iraq and Iran. And while those temperatures might seem extreme, a new study published in Nature Climate Change suggests that scorching temperatures could become increasingly common in the region by the end of the century, if climate change is left unchecked.

According to the study, outdoor temperatures in the Persian Gulf could reach levels inhospitable to human survival as often as once every decade by 2100, with heat and humidity climbing so high that healthy humans couldn’t survive for more than a few hours outside. This would place a huge amount of stress on both poor residents, who cannot afford air conditioning or other adaptive measures, and laborers who work outdoors, like farmers and construction workers.

To understand how climate change could impact future temperatures and human health in the Persian Gulf, researchers from Massachusetts Institute of Technology and Loyola Marymount University used high-resolution climate models to look at a measurement known as the “wet-bulb temperature,” which takes into account both heat and humidity. Researchers chose to look at the wet-bulb temperature because of its direct impact on human health — for humans to maintain a healthy inner body temperature, the wet-bulb temperature cannot exceed 35°C (95°F). If the wet-bulb temperature does exceed that threshold, humans have a difficult time getting rid of metabolic heat, leading to hyperthermia and potentially death.

“The main finding of this study is the projection that, in cities and localities around the Persian Gulf, conditions in the future towards the end of the 21st century would be such that the wet bulb temperature will approach and exceed 35°C,” Elfatih Eltahir, a professor of civil and environmental engineering at MIT, said in a video released by MIT on Monday. Currently, it’s rare for wet-bulb temperatures to exceed 31°C.

Elthair went on to stress that these exceedingly high wet-bulb temperatures wouldn’t necessarily become an everyday occurrence — even under a business-as-usual scenario, wet-bulb temperatures above 95°F probably would only happen once every decade or every few decades.

According to the study, the regions likely to bear the brunt of increased temperatures are the low-lying areas, which are located close to the coast and tend to experience higher levels of humidity — the Persian Gulf itself is very shallow, the researchers note, lending itself to evaporation and high humidity. Major cities, like Qatar, Abu Dhabi, and Dubai could also see temperatures exceed the wet-bulb threshold multiple times over a 30-year period, according to the study. The study also notes that future heat waves could be of “severe consequence” to important Muslim rituals like Hajj — when more than two million pilgrims pray outdoors in Mecca — which could see future wet-bulb temperatures of 32°C.

Still, the study notes that the worst of this extreme heat could be avoided if serious mitigation efforts are taken. Under a scenario where global emissions peak around 2040, and then decline, annual wet-bulb temperatures would not exceed the 35°C threshold at any of the considered locations.