Rising heat in Saudi Arabia threatens millions of Muslim pilgrims – but cutting fossil fuels would keep it safer Global heating has “fundamentally altered” the climate of Mecca and is exposing millions of hajj pilgrims to extreme and dangerous heat even in months outside summer, new analysis has found. Carbon dioxide emissions from fossil fuels means scorching temperatures of 40C (104F) are now regularly experienced in May, the study showed. In past decades, such peaks would only have occurred in summer.