Timescale Dependence of the Precipitation Response to CO2-Induced Warming in Millennial-Length Climate Simulations

Previous work has shown that estimates of climate sensitivity vary over time in response to abrupt CO₂ forcing in climate model simulations. The energy fluxes that drive warming in response to increasing CO₂ also influence precipitation, which prompts the question: Does the precipitation response therefore also vary over time? We investigate by examining the response of precipitation to warming forced by greenhouse gases—the hydrological sensitivity—in a set of millennial-length climate simulations with multiple climate models, Long Run Model Intercomparison Project (LongRunMIP). We compare hydrological sensitivity calculated from three different timescales of the simulations: years 1–20, 21–150, and 151–1000. We show that the hydrological sensitivity lacks a consistent dependence on timescale, in contrast to climate sensitivity. Decomposition of the surface energy budget reveals that the relative muting of the multi-model mean hydrological sensitivity is driven by surface downwelling shortwave flux.