Is the Hajj pilgrimage destined to become a victim of global warming?
Parts of the Middle East, including the Gulf states and Muslim holy places around Mecca, could become uninhabitable even for the young and fit before the century is out, according to a new climate modelling study. The rituals of the Hajj, during which up to 2 million Muslims pray outdoors from dawn to dusk, would be impossible in summer.
Elfatih Eltahir of the Massachusetts Institute of Technology and Jeremy Pal of Loyala Marymount University, Los Angeles, used standard global climate models to show likely future temperatures in the Gulf, assuming global warming of 4 °C, which is possible later this century.
Crucially, they then made predictions of future humidity in order to assess likely “wet-bulb” temperatures, as measured by thermometers whose bulbs are kept damp.
Close to body temperature
The wet-bulb temperature is the best measure of our ability to tolerate high temperatures, because it reflects the ability of the body to cool off by sweating. When wet-bulb temperatures reach 35 °C, which is approaching body temperature, “the human body can no longer get rid of heat”, says Eltahir.
Wet-bulb temperatures are lower than dry-bulb temperatures, but the difference is greater in dry air and less in humid air, reflecting the common experience that dry heat is easier to endure than muggy heat.
“It is often assumed that humans would be able to adapt to any possible warming,” says Matthew Huber of Purdue University in West Lafayette, Indiana. “But any wet-bulb temperature over 35 °C for extended periods should induce hyperthermia, as dissipation of metabolic heat becomes impossible.”
Currently, wet-bulb temperatures rarely exceed 31 °C anywhere in the world, say Pal and Eltahir.
But the Gulf states are getting closest to the 35 °C threshold. This is because high temperatures are combined with the high humidity of air moistened by the exceptionally warm waters of the Gulf.
At the end of July this year, when dry-bulb temperatures in the Gulf exceeded 50 °C at times, wet-bulb temperatures peaked at 34.6 °C, Christoph Schär of the Swiss Federal Institute of Technology in Zurich writes in an accompanying article in Nature Climate Change.
This is the first study to have predicted that populated regions could suffer conditions during this century that “may be fatal to everybody affected, even young and fit individuals under shaded and well-ventilated outdoor conditions”, says Schär. Coastal urban centres such as Dubai, Abu Dhabi and Doha are most at risk.
While many Gulf citizens live their lives largely inside air conditioned buildings, there are exceptions. One is Muslims from round the world attending the rituals of the Hajj. A second is foreign workers on construction sites. Qatar has been accused of allowing South Asian workers building stadiums for the World Cup in 2022 to die from heatstroke.
In August, Islamic leaders called on Muslims around the world, including oil-producing states, “to lead the way in phasing out greenhouse-gas emissions.”
But so far the governments of Gulf states – which include some of the world’s major producers of planet-warming oil and gas supplies – have made no promises to the forthcoming Paris conference to limit their greenhouse gas emissions.
Journal reference: Nature Climate Change, DOI: 10.1038/nclimate2833
Read more: “Climate shock: One heatwave from oblivion”
image credit: Mohamed El-Dakhakhny/SIPA/Rex Shutterstock
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