Asymmetric response of precipitation extremes in China to CO₂ removal forcing

Abstract Understanding precipitation extremes response to CO 2 removal (CDR) in China is crucial for climate change mitigation and adaptation. This study examines the responses of heavy precipitation, represented by the maximum consecutive 5-day precipitation (Rx5day), over China under an idealized CDR scenario using five models from phase 6 of the Coupled Model Inter-comparison Project (CMIP6). The results reveal an asymmetric response, indicating that China may experience more severe heavy precipitation events compared to the pre-industrial (PI, 1850–1900) period, even if CO 2 concentrations are reduced to PI levels. From June to September, the increase in Rx5day across most of China relative to the PI stage is primarily driven by upward air motions and the convergence of water vapor flux. The regions with overshoot are linked to southward movement of westerly jet, as well as shifts in vertical motion. A moisture budget diagnosis demonstrates that the thermal term plays a dominant role in promoting water vapor convergence across most of China, while the dynamic term leads to water vapor divergence in specific areas. These results in corresponding increases and decreases in extreme precipitation, respectively. Specifically, water vapor advection associated with the thermal term, along with the convergence and divergence linked to the dynamic term, serves as the principal determinants influencing the distribution of water vapor changes in China from June to September. Our study highlights the need for further investigation into more effective mitigation and adaptation strategies in the context of CDR.