Hysteresis of extreme precipitation in East Asia under various CO2 removal pathways

Extreme precipitation poses severe societal and economic risks under elevated atmospheric carbon dioxide (CO2), yet current understanding of how it will respond to various future CO2 removal scenarios remains limited. Focusing on East Asia, a region highly vulnerable to monsoonal dynamics and anthropogenic influences, here we assess the hysteresis of extreme precipitation responses under four CO2 concentration thresholds and two emission reduction rates using climate model simulations. The extreme precipitation indices based on intensity and frequency exhibit an increase during the CO2 peak, but fail to fully return to their initial states even after CO2 levels decline to their initial levels. This hysteresis behavior is amplified by delayed and slower emission reductions. The hysteresis is linked to increases in mean monsoon precipitation associated with hysteresis in tropical Pacific warming patterns and subsequent atmospheric teleconnections. Moisture budget analysis further indicates that enhanced precipitation is attributed to increased moisture transport into East Asia, driven by early-summer rises in specific humidity (thermodynamic factor) through mean circulation and late-summer intensification of monsoon circulation (dynamic factor). These findings reveal the mechanisms shaping East Asian extreme precipitation under different carbon removal pathways and highlight the critical role of both timing and pace of emission reductions in determining regional climate outcomes. Across carbon removal experiments, East Asian extreme precipitation can remain elevated as CO2 declines, with later and slower CO2 removal producing stronger hysteresis associated with delayed tropical Pacific warming and changes in the monsoon circulation.