Abstract Reliable projections of the future hydrological cycle are needed for designing adaptation and mitigation measures under global warming. However, uncertainties in the projected sign and magnitude of effective precipitation changes (precipitation minus evaporation, P − E) remain high. Here, we examine the state dependency of circulation, temperature, and relative humidity contributions to P − E changes in simulations of the Last Glacial Maximum (LGM), mid-Holocene, and abrupt quadrupling of the atmospheric carbon dioxide concentration. To this purpose, we apply a moisture budget decomposition and a thermodynamic scaling approximation to CMIP6/PMIP4 simulations with the Earth system model MPI-ESM1.2. We find that the importance of thermodynamic and dynamic contributions to P − E changes and the patterns of dynamic contributions depend strongly on the underlying forcing. Greenhouse gas forcing leads to a stronger thermodynamic response than dynamic response. The LGM ice sheets yield a large dynamic contribution with zonally heterogeneous patterns. Orbital forcing induces a predominantly dynamic response with a hemispherically antisymmetric structure. We also identify state-invariant features: The importance of temperature and relative humidity contributions to specific humidity changes is consistent across states, and the wet-get-wetter–dry-get-drier paradigm proposed for global warming holds in almost all regions dominated by thermodynamic contributions. By definition, the P − E budget and the respective thermodynamic, dynamic, and transient eddy contributions vanish in the global mean. Moreover, we find that for increasing length scales, the spatial variability of these contributions decays with similar rates. We suggest repeating our analysis for more models and states which could help constrain hydroclimate projections. Significance Statement We aim at improving our understanding of the influence of changes in winds and water vapor on the local balance between precipitation and evaporation. To this end, we compare simulations for two past climate states with an idealized high carbon dioxide concentration scenario. We find characteristics that depend on the underlying state and characteristics that are consistent across states. Our results help to identify what we can learn from past climate states about precipitation changes under future greenhouse gas emission scenarios. So far, we only analyzed simulations from one model. Therefore, we suggest to repeat our analysis with more models and for more past climate states to confirm our results.
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