Global heating has fundamentally altered the climate of Mecca, exposing millions of hajj pilgrims to extreme and dangerous heat even outside summer, a new analysis has found. Carbon dioxide emissions from fossil fuels mean scorching temperatures of 40°C are now regularly experienced in May, whereas in past decades such peaks only occurred in summer.
The study by the World Weather Attribution group shows that the average temperature for May is now 3.5°C hotter than before human-caused global heating. As a result, hajj in May is now as dangerous as the height of summer used to be. Without a rapid transition away from fossil fuels, the pilgrimage would face dangerous heat almost all year round by the end of the century.
Saudi Arabia, the world’s second biggest oil producer, has long obstructed climate action. The Saudi authorities have introduced heat action plans including shaded walkways, cooling stations, misting systems and expanded medical services, which have helped reduce heat-related illnesses among pilgrims.
However, Professor Friederike Otto at Imperial College London, an author of the study, warned: 'If we don’t rapidly reduce our dependence on fossil fuels – an industry at the very centre of the Saudi economy – we are resigning ourselves to the fact that millions of Muslims will be forced to carry out the hajj rituals in a climate that is simply unsuitable for it.'
Dr Clair Barnes, also at Imperial College London, said: 'Our analysis shows very clearly that less of the year is now safe for the millions of Muslims who wish to undertake the hajj. As long as we continue to burn fossil fuels, the window for bearable hajj temperatures will continue to shrink.'
More than 1,300 pilgrims died due to extreme heat and humidity in 2024, when hajj was in June. A 2022 study found that if global temperatures rise by 3°C by the end of the century, about 97% of all hajj pilgrimages would endure dangerous levels of heat in Mecca.
