Contrasting Hysteresis Behaviors of Northern Hemisphere Land Monsoon Precipitation to CO2 Pathways

Abstract

Understanding precipitation changes over the Northern Hemisphere land monsoon (NHLM) region, where nearly 60% of the world's population resides, is fundamental for hydrological projections and adaptations against climate change. There are many studies on the hydrological cycle under various climate change scenarios. However, there is still a lack of research on the hydrological responses to CO2 removal as a global warming mitigation measure from a global perspective. This study demonstrates the distinguished hysteresis responses of mean NHLM precipitation based on idealized CO2 ramp-up and ramp-down experiments using the Community Earth System Model|Community Earth System model. The Indian and North African monsoons have time asymmetry in the mean precipitation changes under the CO2 increase and decrease pathways, while the North American monsoon does not. The zonal contrasting hysteresis is attributed to longitudinally contrasting changes in the intertropical convergence zone position driven by the inter-hemispheric and land–sea thermal contrast. On the contrary, changes in extreme precipitation exhibit little temporal asymmetries over any of the NHLM domains. These results provide new insights into climate hysteresis of the hydrological cycle from regional and global perspectives.