Saudi Arabia: Muslim pilgrims risk being killed by heat

By Paul Brown

Even with climate mitigation measures, the summer heat in Mecca will threaten the lives of many thousands of Muslim pilgrims visiting the city.

LONDON − Many of the nearly two million Muslim pilgrims who journey to Saudi Arabia annually will soon be in severe danger of death from the extreme heat in years when the Hajj takes place in mid-summer, scientists say.

For 1.8 billion Muslims, around a quarter of the world’s population, a pilgrimage to Mecca, known as the Hajj, is an obligation to be undertaken once in their lifetime. But the city is in one of the hottest places in the world, where the temperature already tops 45°C (113°F) in summer, enough to damage the heart, brain and kidneys.

According to researchers at the Massachusetts Institute of Technology (MIT), when climate change drives temperatures even higher it will threaten the lives of thousands of people who typically spend more than a week on the pilgrimage in unrelenting heat.

The dates for the Hajj are fixed by the lunar cycle, and arrive 11 days earlier each year. This year the pilgrimage ended on 14 August in temperatures over 40°C (104°F), already close to the danger threshold for human life. The scientists warn that next year’s mid-summer Hajj could be even more dangerous for pilgrims.

It is not just the temperature but also the humidity that is important. Scientists use what is known as the wet bulb temperature, measured by attaching a wet cloth to a thermometer bulb to indicate how effective perspiration is at cooling off the body. The higher the humidity, the greater the danger of health problems, because the body cannot effectively cool itself down.

“If you have crowding in a location, the harsher the weather conditions are, the more likely it is that crowding would lead to incidents”

At an actual temperature of just 32.2°C (90°F) and a humidity of 95%, the wet bulb temperature is calculated as 51.1°C (124°F). At a lower humidity of 45%, more typical of Saudi Arabia, the 51.1°C wet bulb temperature would not be reached until the actual temperature climbed to 40°C (104°F)

But the scientists warn that with anything above a wet bulb temperature of 39.4°C (102.9°F), the body can no longer cool itself. Such temperatures are classified as “dangerous” by the US National Weather Service. Above 51.1°C (124°F) is classified as “extreme danger”, when the body’s vital organs begin to be badly affected.

There have been earlier warnings of the risks posed by this lethal combination, some coupled with suggestions that a wider part of the region surrounding Saudi Arabia could possibly become uninhabitable.

Elfatih Eltahir, MIT professor of civil and environmental engineering, and his colleagues, writing in the journal Geophysical Review Letters, said there had already been signs of the risk becoming a reality. Although details of the events are scant, there have been deadly stampedes during the Hajj in recent decades: one in 1990 that killed 1,462 people, and one in 2015 that left 769 dead and 934 injured.

Unhappy coincidence

Eltahir says that both of these years coincided with peaks in the combined temperature and humidity in the region, as measured by the wet bulb temperature, and the stress of elevated temperatures may have contributed to the deadly events.

“If you have crowding in a location,” Eltahir says, “the harsher the weather conditions are, the more likely it is that crowding would lead to incidents” like these.

In Saudi Arabia climate change will significantly increase the number of days each summer that will exceed this “extreme danger” limit. In the years 2047 to 2052 and 2079 to 2086, when the Hajj again takes place at the hottest time of year, it will probably be too dangerous for pilgrims, the researchers say.

This will happen even if substantial measures are taken to limit the impact of climate change, the study finds, and without those measures the dangers would be even greater. Planning for counter-measures or restrictions on participation in the pilgrimage may therefore be needed, Professor Eltahir concluded.

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