Enhanced risk of concurrent regional droughts with increased ENSO variability and warming
Abstract Spatially compound extremes pose substantial threats to globally interconnected social-economic systems. We use an Earth system model large ensemble to examine the future risk of compound droughts during the boreal summer over ten global regions with highly seasonal climate. Relative to the late-20th century, the probability, mean extent and severity of compound droughts increase by ~60%, ~10% and ~20% respectively by the late-21st century, with a disproportionate increase in risk across North America and the Amazon. These changes result in a ~9-fold increase in exposure over agricultural areas and ~5 to 20-fold increase in population exposure depending on the shared socioeconomic pathway. ENSO is the predominant large-scale driver of compound droughts with 68% of historical events occurring during El Niño or La Niña conditions. ENSO teleconnections remain stationary in the future though an ~22% increase in ENSO extremes combined with projected warming, drive the elevated risk of compound droughts.