The impact of aerosols on forcing and feedbacks in CMIP5

Abstract:

Radiative kernels are used to estimate direct radiative forcing of aerosols and aerosol-induced cloud responses in coupled ocean-atmosphere model simulations under historical and future emission scenarios. The method is evaluated using matching pairs of historical climate change experiments with and without aerosol forcing. The radiative kernels are able to accurately capture both the spatial pattern and global mean effects of aerosol forcing and aerosol-induced cloud changes. We also quantify the aerosol-mediated response of the atmospheric circulation and energy transport to aerosol forcing. Aerosol forcing induces coherent changes in the dynamics and energy transport. The response associated with this change in energy transport also induces non-local cloud responses whose global-mean radiative impact is comparable in magnitude to the in-situ component of aerosol indirect forcing. In CMIP5 models, the impact of this aerosol-induced dynamical cloud response is large enough to alter the sign of the aerosol-mediated cloud-radiative response.