Can precipitation help us attribute the temperature “hiatus”?

Thursday, 18 December 2014
Kate Marvel, Lawrence Livermore National Laboratory, Livermore, CA, United States
The ability of the atmosphere to balance the latent heat of precipitation (P) with radiative cooling provides a strong energetic constraint on global-mean precipitation. The P response to forcing may be partitioned into a “slow” temperature-mediated component, and a “fast” response that depends on the nature of the external forcing. Abrupt GHG forcing, for example, leads to an immediate suppression of global-mean P followed by a slower temperature-mediated increase. Previous studies have established that this slow response is roughly independent of forcing, and thus removing the temperature-mediated component from the observed precipitation response yields a picture of the forcing-dependent fast response. The GPCP satellite dataset indicates that, in recent years, global-mean precipitation has decreased even as global-mean surface temperature has remained roughly constant. Does this atypical behavior reveal the signatures of external forcing agents? Using observational data and CMIP5 single-forcing experiments, we examine the roles of various external forcing agents in the hiatus decade and explore their effect on the scaling of precipitation with temperature.