Perturbations to Global Energy Budget Due to Absorbing and Scattering Aerosols

Impacts of absorbing and scattering aerosols on global energy balance are investigated with a global climate model. A series of sensitivity experiments perturbing emissions of black carbon and sulfate aerosols individually is conducted with the model to explore how components of global energy budget change in response to the instantaneous radiative forcing due to the two types of aerosols. It is demonstrated how differing vertical structures of the instantaneous radiative forcing between the two aerosols induce distinctively different proportions of fast and slow climate responses through different energy redistribution into atmosphere and surface. These characteristics are quantified in the form of the whole picture of global energy budget perturbations normalized by the top-of-atmosphere instantaneous radiative forcing. The energy budget perturbation per “unit” instantaneous forcing thus quantified reveals relative magnitudes of changes to different component fluxes in restoring atmospheric and surface energy balances through fast and slow responses. The normalized picture then directly links the “initial forcing” to the eventual climate “responses,” thereby explaining how starkly different responses of the global-mean temperature and precipitation are induced by the two types of aerosols. The study underscores a critical need for better quantifications of the forcings' vertical structure and atmospheric rapid adjustment for reliable estimates of climatic impact of absorbing and scattering aerosols. In particular, cloud responses through the indirect and semidirect effects and the sensible heat decrease in response to stabilized atmosphere due to the black carbon heating are identified as key uncertain components in the global energy budget perturbation.