Asymmetric Response of Land Precipitation Variability Under Carbon Dioxide Removal

Abstract

Abstract Precipitation variability describes fluctuations between wet and dry conditions and plays an important role in shaping hydrological extremes and their societal impacts. Using idealized carbon dioxide removal experiments from CMIP6 models, we assess how precipitation variability responds to symmetric CO 2 ramp‐up and ramp‐down forcing across time scales from day‐to‐day to intraseasonal. Precipitation variability strengthens with increasing CO 2 and remains stronger during the ramp‐down phase than during the ramp‐up phase, even at comparable CO 2 concentrations. This asymmetry is evident across time scales and is particularly pronounced over several densely populated land regions, including North America, Europe, South Asia and East Asia. Diagnostics based on a simplified moisture‐budget framework indicate that the asymmetry is primarily driven by thermodynamic moistening, which enhances variability in vertical moisture transport. These results demonstrate a pronounced asymmetric response of short‐timescale precipitation variability to CO 2 forcing, highlighting the persistence of hydroclimatic variability beyond the period of CO 2 reduction.