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.