Abstract
AbstractThe response of the hydrological cycle to climate forcings can be understood within the atmospheric energy budget framework. In this study precipitation and energy budget responses to five forcing agents are analyzed using 10 climate models from the Precipitation Driver Response Model Intercomparison Project (PDRMIP). Precipitation changes are split into a forcing-dependent fast response and a temperature-driven hydrological sensitivity. Globally, when normalized by top-of-atmosphere (TOA) forcing, fast precipitation changes are most sensitive to strongly absorbing drivers (CO2, black carbon). However, over land fast precipitation changes are most sensitive to weakly absorbing drivers (sulfate, solar) and are linked to rapid circulation changes. Despite this, land-mean fast responses to CO2 and black carbon exhibit more intermodel spread. Globally, the hydrological sensitivity is consistent across forcings, mainly associated with increased longwave cooling, which is highly correlated with intermodel spread. The land-mean hydrological sensitivity is weaker, consistent with limited moisture availability. The PDRMIP results are used to construct a simple model for land-mean and sea-mean precipitation change based on sea surface temperature change and TOA forcing. The model matches well with CMIP5 ensemble mean historical and future projections, and is used to understand the contributions of different drivers. During the twentieth century, temperature-driven intensification of land-mean precipitation has been masked by fast precipitation responses to anthropogenic sulfate and volcanic forcing, consistent with the small observed trend. However, as projected sulfate forcing decreases, and warming continues, land-mean precipitation is expected to increase more rapidly, and may become clearly observable by the mid-twenty-first century.
Highlights
Understanding changes in the hydrological cycle is of great importance due to the potential impact on society (Alfieri et al 2015)
In this study we present the global, land, and sea mean precipitation and atmospheric energy budget responses to five climate drivers (CO2, CH4, black carbon, sulfate, and insolation) across 10 global climate models participating in the Precipitation Driver Response Model Intercomparison Project (PDRMIP) (Myhre et al 2017)
Doubling CO2 produces a large negative fast precipitation response associated with the reduction in atmospheric LW cooling
Summary
Understanding changes in the hydrological cycle is of great importance due to the potential impact on society (Alfieri et al 2015). VOLUME 31 individual forcing agents (Lambert and Faull 2007; Andrews et al 2010; Kvalevåg et al 2013) as well as global warming (Held and Soden 2006; Previdi 2010). This is because precipitation is tightly constrained by the atmospheric energy budget, such that globally the latent and sensible heat fluxes are balanced by net atmospheric radiative cooling (Mitchell et al 1987; Allen and Ingram 2002; O’Gorman et al 2012; Pendergrass and Hartmann 2014). The fast precipitation response includes the direct radiative effects of the forcing agent, as well as any rapid adjustments of the troposphere and land surface
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