Madden–Julian Oscillation-induced extreme rainfalls constrained by global warming mitigation

Abstract

The sixth assessment report of the IPCC indicates low-to-high confidence in trends of extreme rainfall with regional inconsistency in the tropics, where a key phenomenon causing intra-seasonal variations in weather is the Madden–Julian Oscillation (MJO). It remains unknown how the MJO-induced extreme rainfall and the societal exposure may change in response to global warming and climate mitigation attempts. Here, using eight CMIP6 models that capture the eastward-propagating MJO structure and amplitude, we detect a nearly 60% increase in extreme rainfall over tropical Asia and Australia by the end of the 21st century under the fossil-fueled warming scenario (SSP5-8.5); 84% of this change is associated with MJO-induced extreme rainfall. Extreme rainfall increases are modulated by the warming-induced asymmetric changes in MJO phase characteristics, occurring mostly over the lands with distinct zonal differences. The region that is most likely to be affected includes Malaysia, Indonesia, and northern Australia where 96.68 million people and 9.72 million km2 of urban areas are exposed to potential danger stemming from extreme rainfall. More than 95% (99%) of the population (urban) exposure can be potentially avoided under the “middle of the road” development (SSP2-4.5) scenario, whereby CO2 emissions hover around current levels before starting to fall mid-century.