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Dangerous heat and humidity conditions are likely to occur every year during the Muslim pilgrimage, or Hajj, near the end of the century if high carbon emissions continue. A new analysis of temperature predictions made by three computer climate models for the area around Mecca, Saudi Arabia shows how climate change could reshape the religion practiced by 1.8 billion people around the world.
All Muslims are obligated to undertake Hajj at some point during their life, if health and finances permit. The ritual takes place in Mecca and the surrounding desert over the course of five days. It involves standing, walking, and praying along with millions of other pilgrims at a series of holy sites – about 20 to 30 hours outdoors overall.
The Muslim calendar is based on the lunar cycle, so the timing of Hajj shifts slightly in relation to the solar calendar each year. It falls during the summer months through 2020, as well as during 2045-2053 and 2079-2086.
Saudi Arabia has hot summers that have been getting hotter, and climate change is projected to lead to greater temperature increases in summer than in winter. Summers can also be muggy, due to westerly winds that blow humid air from the Red Sea inland.
Heat plus humidity is dangerous because the human body becomes unable to cool itself effectively by sweating in these conditions. Scientists express the combined effects of temperature and humidity using a measure known as wet bulb temperature. The U.S. National Weather Service considers wet bulb temperatures above 24.6 °C to be dangerous, and those above 29.1 °C extremely dangerous.
Over the past 30 years, 60% of years with a summer Hajj have seen wet bulb temperatures above the 24.6 °C danger threshold sometime during the pilgrimage period. These conditions are believed to have been a factor in stampedes that occurred in July 1990 and September 2015, both resulting in the deaths of hundreds of pilgrims.
And those dangerous conditions are likely to become more frequent and intense as climate change proceeds. If high carbon emissions continue, dangerous wet bulb temperatures are likely to occur during every summer Hajj by the end of the century, researchers reported August 22 in Geophysical Research Letters.
Moderate emissions cuts (slightly less aggressive those prescribed in the Paris Agreement) will still likely result in wet bulb temperatures above 24.6 °C during nearly every summer Hajj by the end of the century.
In the past 30 years, wet bulb temperatures past the extreme danger threshold of 29.1 °C have not occurred during Hajj. But if high carbon emissions continue, they are likely to occur in 20% of years between 2045-2053, and 42% of years between 2079-2086. Fortunately, moderate emissions cuts could cut the risk in at least half, the researchers found, holding the extreme danger to 15% of years during the former period and 19% of years during the latter.
Islam is the world’s fastest growing religion. The Saudi government has recently improved Hajj infrastructure, adding misters along pilgrimage routes for relief from the heat and widening some routes to reduce overcrowding.
But in the future, if pilgrims decide to make their Hajj during a year when it falls outside the summer months to avoid extreme heat, that strategy could exacerbate crowding. Plus, as climate change proceeds, dangerous wet bulb temperatures are more likely to occur outside the summer months.
Officials might have to reduce the number of people allowed to make the pilgrimage during high-risk years, or forbid those in poor health or frail condition from taking part, the researchers suggest.
Source: Kang S. et al. “Future Heat Stress During Muslim Pilgrimage (Hajj) Projected to Exceed ‘Extreme Danger’ Levels.” Geophysical Research Letters 2019.
Image: BBC World Service via Flickr.