If climate change continues unabated, the Persian Gulf will experience heat waves that push the heat index beyond 170 degrees for extended periods of time. This startling projection was just published online in the journal Nature Climate Change.

A heat index of 170 is particularly concerning because it roughly corresponds to a wet-bulb temperature of 35° Celsius. Wet-bulb temperature factors in both actual air temperature and the moisture the air contains. At 35° Celsius, the human body's cooling systems are rendered inoperable. Rather than shed heat to the environment, the body takes it in. In such a hostile environment, young and fit individuals will be at risk of hyperthermia and death, even when under the shade.

A wet-bulb temperature of 35° Celsius has never been directly observed, but residents of Bandar Mahshahr in Iran came close to experiencing it this past summer, when temperatures of 115° Fahrenheit were accompanied by a relative humidity of 49%, producing a wet-bulb temperature of 34.6 °C.

Today, temperatures like that are headline-grabbing rarities, but the architects of the new paper, Jeremy Pal and Elfatih A. B. Eltahir, respectively based out of Loyola Maramount University and the Massachusetts Institute of Technology, say such conditions could potentially become the new normal for extreme heat waves in the Persian Gulf after 2070.

Particularly concerning, Pal and Eltahir note, are the potential ramifications for the Hajj, the Islamic pilgrimage to Mecca undertaken by millions every year.

"This necessary outdoor Muslim ritual is likely to become hazardous to human health, especially for the many elderly pilgrims, when the Hajj occurs during the boreal summer."

The Persian Gulf is uniquely susceptible to extreme heat conditions on account of its regularly clear skies, which allows solar radiation to rain down, as well as relatively shallow seas nearby, which absorb heat and release water vapor that retains heat near the ground.

Luckily, the potentially deadly conditions in the Persian Gulf predicted by Pal and Eltahir's models only occur under the "business as usual" scenario, in which no steps are taken to curb carbon emissions and average global temperatures rise by 6.7° F. If temperatures only rise by 3.2° F, then the intolerable conditions will largely be avoided, they say.

Source: Jeremy S. Pal and Elfatih A. B. Eltahir. Future temperature in southwest Asia projected to exceed a threshold for human adaptability. Nature Climate Change. PUBLISHED ONLINE: 26 OCTOBER 2015 | DOI: 10.1038/NCLIMATE2833

(Image: AP)