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.

This study has examined relative contributions of dynamic and thermodynamic components to East Asian summer monsoon (EASM), compared to the others over Asia. We have decomposed of moisture budget into the dynamic and thermodynamic components composing of interannual variability of the EASM. As represented by the moisture budget, the Asian monsoon is mostly caused by changes in winds (dynamic component); interestingly, changes in moisture (thermodynamic component) play an important role in monsoon rainfall anomalies only for East Asia (27.09%). In terms of the dynamic component over East Asia, strong continental heating, resulting in enhanced land‐sea contrast, is identified as crucial to a local development of winds toward East Asia, and it ultimately strengthens a meridional wind, which is accompanied by the western North Pacific subtropical high. In addition, the negative winter North Atlantic Oscillation could induce the enhanced moisture advection term of the dynamic component over East Asia through barotropic Rossby wave propagation. The thermodynamic component has a localized effect on net precipitation at midlatitudes, with an enhanced wave train pattern with a zonal wavenumber‐5, which reinforces the Okhotsk high. These distinct large‐scale circulation patterns together create favorable conditions for heavy rainfall over East Asia when the two components are positively in‐phase. Here we have also described that the extreme heavy rainfall is noticeable when the Eurasian blocking occurs. This study is expected to improve the detailed predictability of the EASM by understanding the two components to prevent disaster risks in terms of extreme rainfall.

The Indo-Pacific warm pool (IPWP) is enclosed by a 28 °C isotherm and plays a vital role in controlling atmospheric circulations. However, the effects of changes in regional warm pool sea surface temperatures (SSTs) remain unexplored. We divided the IPWP into the Indian and Pacific sectors and distinguished their responses to natural variability and global warming. Furthermore, we examined the impacts of the interannual variability (IAV) in warm pool SST on the tropical Hadley, Walker, and monsoon circulations. The Hadley circulation was affected by warm pool SST warming, i.e., warmer SSTs over the warm pool strengthened the upward branch of Hadley circulation, whereas the downward branch was respectively weakened and strengthened in the Northern and Southern Hemispheres. Walker circulation was strengthened (weakened) in the warming (natural) mode. Consequently, the Walker circulation is weakened since the natural variability of warm pool SST plays a more dominant role rather than the warming trend of SSTs over the warm pool. Furthermore, our analysis displays that warm pool warming has little impact on the monsoon circulation. Our findings highlight the different roles of the IAV of warm pool regions in each tropical circulation as part of the warming trend and natural variability.

In 2023, the global temperature rose significantly, triggering a marine heatwave (MHW) in the East China Sea (ECS) from August 12 to October 13. Unlike the typical July onset, this event was delayed. Here we investigate the mechanisms behind the late onset and prolonged duration of the 2023 MHW in the ECS and its potential linkage to global warming. The early phase was driven by shortwave radiation and ocean dynamics, while the later phase saw reduced northerly winds, allowing warmer, more humid southerlies to dominate. This shift decreased the air-sea humidity difference, enhancing downward latent heat fluxes. Future CMIP6 projections also suggest that delayed MHWs are linked to weak heat exchanges, limiting the oceanic heat transport to the atmosphere. Our findings highlight the increasing risk of prolonged MHWs in the ECS and the urgent need for improved climate preparedness.

This study investigates the mechanism of the hysteresis of European summer mean precipitation in a CO₂ removal (CDR) simulation. The European summer mean precipitation exhibits robust hysteresis in response to the CO₂ forcing; after decreasing substantially (∼40%) during the ramp-up period, it shows delayed recovery during the ramp-down period. We found that the precipitation hysteresis over Europe is tied to the hysteresis in the Atlantic Meridional Overturning Circulation (AMOC). During the ramp-down period, an anomalous high surface pressure circulation prevails over Europe. The anomalous high pressure system is a baroclinic response of the atmosphere to strong North Atlantic cooling associated with a weakened AMOC. This anomalous circulation suppresses summertime convective activity over the entire Europe by decreasing near-surface moist enthalpy in Central and Northern Europe while increasing lower free-tropospheric temperature in Southern Europe. Our findings underscore the need to understand complex interactions in the Earth system for reliable future projections of regional precipitation change under CDR scenarios.