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

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 intra-seasonal phenomenon is the Madden–Julian Oscillation (MJO). How MJO-induced extreme rainfall and societal exposure respond to warming and mitigation is unclear. Using eight CMIP6 models that capture the eastward-propagating MJO structure and amplitude, the study detects a nearly 60% increase in extreme rainfall over tropical Asia and Australia by the end of the 21st century under SSP5-8.5; 84% of this change is associated with MJO-induced extreme rainfall. Increases are modulated by warming-induced asymmetric changes in MJO phase characteristics, with most increases over land and distinct zonal differences. The most affected region includes Malaysia, Indonesia, and northern Australia where 96.68 million people and 9.72 million km² of urban areas are exposed to increased extreme rainfall. More than 95% (99%) of the population (urban) exposure can potentially be avoided under SSP2-4.5, where CO2 emissions hover around current levels before declining mid-century.