Increasing population exposure to global warm-season concurrent dry and hot extremes under different warming levels

Projecting future changes in concurrent dry and hot extremes (CDHEs) and the subsequent socio-economic risks (e.g. population exposure) is critical for climate adaptation and water management under different warming targets. However, to date, this aspect remains poorly understood on both global and regional scales. In this study, the changes in future CDHEs and their population exposures under 1.5 °C, 2 °C, and 3 °C warming were quantified using a Standardized Dry and Hot Index calculated based on the newly released Coupled Model Intercomparison Project Phase 5 climate model outputs and global population datasets. It was found that relative to the baseline period (1986-2005), the severity of CDHEs would increase on the global scale and in most regions, such as in Southern Europe, the Mediterranean, Sahara, West Africa, Central America, Mexico, the Amazon, and the west coast of South America under 1.5 °C, 2 °C, and 3 °C of warming. Stabilizing the warming at 1.5 °C would constrain the adverse influence of CDHEs on the population suffering from severe CDHEs in most regions (especially in Central Europe, Southern Europe, the Mediterranean, Eastern North America, West Asia, East Asia, and Southeast Asia). Globally, the population impacted by severe CDHEs (with a constant 2000 population) would increase by 108 and 266 million (149 and 367 million when constant 2080 population is applied) for 2 °C and 3 °C increase compared to a 1.5 °C increase. These findings provide scientific evidence of the benefit of limiting anthropogenic warming to 1.5 °C in terms of the socio-economic risks related to CDHEs.