Heat Stress During Arba’een Foot-Pilgrimage (World’s Largest Gathering) Projected to Reach “Dangerous” Levels Due To Climate Change

Abstract

Arba’een, a Muslim pilgrimage, is one of the largest annual mass gatherings in the world, with a date fixed according to the lunar calendar. Most pilgrims start their long walking journey from Basra/Najaf toward Karbala (about 70–500 km) and are significantly affected by outdoor weather conditions during this period. Here, based on simulations performed using carefully-selected climate models, we project that heat stress during the pilgrimage is likely to reach a “dangerous” level, defined according to the US National Weather Service criteria, by the end of this century. Moreover, a significant increase in consecutive occurrence of hot days and hot nights is expected within the coming decades, which may cause a high incidence of heat-related disorders as the human body may not recover from the daytime heat loads. Our study suggests that sound adaptation measures and stringent mitigation actions must be established to ensure a safe pilgrimage in the future.

Plain Language Summary

Arba’een is a religious mass gathering, drawing millions of people to the holy city of Karbala in Iraq annually. When this procession occurs in the sweltering summer, it could cause significant heat-related morbidity and mortality. Despite the growing risk of heat stress with global warming, less attention has been paid to heat-related issues during this religious ceremony. Without adequate adaptation and mitigation strategies to climate change, more frequent and severe heatwaves (associated with the consecutive occurrence of hot days and nights) in a warmer world may pose a substantial threat to the Arba’een participants’ health.