Within this century, parts of the Middle East, in particular the Persian Gulf region, could be hit with unprecedented events of deadly heat as a result of climate change, according to a study of high-resolution climate models, published Monday. Generally, Jeddah, the Red Sea port city in Western Saudi Arabia and Mecca in the mountains to the south, have more moderate temperatures than in the east coast but I was in Jeddah on 30 June 1995 for the hottest day in 20 years — 48°Celsius (118°Fahrenheit) and higher when humidity is accounted for. In more recent times Jeddah has been hit by extreme floodings and on 22 June 2010 the temperature rose to 52°C (126°F) — the record heat was accompanied by a sandstorm, which triggered power plant blackouts.

 

The study, published in the journal Nature Climate Change, was carried out by Elfatih Eltahir, a professor of civil and environmental engineering at MIT, and Jeremy Pal of Loyola Marymount University. They conclude that conditions in the Persian Gulf region, including its shallow water and intense sun, make it “a specific regional hotspot where climate change, in absence of significant mitigation, is likely to severely impact human habitability in the future.”

Running high-resolution versions of standard climate models, Eltahir and Pal found that many major cities in the region could exceed a tipping point for human survival, even in shaded and well-ventilated spaces. Eltahir says this threshold “has, as far as we know...never been reported for any location on Earth.”

That tipping point involves a measurement called the “wet-bulb temperature” that combines temperature and humidity, reflecting conditions the human body could maintain without artificial cooling. That threshold for survival for more than six unprotected hours is 35°C, or about 95°F, according to recently published research. (The equivalent number in the National Weather Service’s more commonly used “heat index” would be about 165°F.)

This limit was almost reached this summer, at the end of an extreme, weeklong heat wave in the region: On July 31, the wet-bulb temperature in Bandahr Mashrahr, Iran, hit 35°C — just a fraction below the threshold, for an hour or less.

The severe danger to human health and life occurs when such temperatures are sustained for several hours, Eltahir says — which the models show would occur several times in a 30-year period toward the end of the century under the business-as-usual scenario used as a benchmark by the Intergovernmental Panel on Climate Change.

The Persian Gulf region is especially vulnerable, the researchers say, because of a combination of low elevations, clear sky, water body that increases heat absorption, and the shallowness of the Persian Gulf itself, which produces high water temperatures that lead to strong evaporation and very high humidity.

The models show that by the latter part of this century, major cities such as Doha, Qatar, Abu Dhabi, and Dubai in the United Arab Emirates, and Bandar Abbas, Iran, could exceed the 35°C threshold several times over a 30-year period. What’s more, Eltahir says, hot summer conditions that now occur once every 20 days or so “will characterize the usual summer day in the future.”

While the other side of the Arabian Peninsula, adjacent to the Red Sea, would see less extreme heat, the projections show that dangerous extremes are also likely there, reaching wet-bulb temperatures of 32 to 34 °C. This could be a particular concern, the authors note, because the annual Hajj, or annual Islamic pilgrimage to Mecca — when as many as 2m pilgrims take part in rituals that include standing outdoors for a full day of prayer — sometimes occurs during these hot months.

Middle East, Hajj extreme heat, climate change

The Ka'ba within the Grand Mosque, Mecca. Source: www.alharamain.gov.sa

While many in the Persian Gulf’s wealthier states might be able to adapt to new climate extremes, poorer areas, such as Yemen, might be less able to cope with such extremes, the authors say.

Christoph Schaer, a professor of atmospheric and climate science at ETH Zurich (Swiss Institute of Technology) who was not involved in this study, provided an independent commentary in the journal, writing that while deadly heat waves have occurred recently in Chicago, Russia, and Europe, in these cases infants and the elderly were most affected. The new study, Schaer writes, “concerns another category of heat waves — one that may be fatal to everybody affected, even to young and fit individuals under shaded and well-ventilated outdoor conditions.”

Schaer writes that “the new study shows that the threats to human health may be much more severe than previously thought, and may materialize already in the current century.” He added: “I think the study is of great importance, since it indicates where heat waves could get worst if climate change proceeds.”

Image on top from the Nature Climate Change study