Seminar

Abstract

Radiative forcing of climate occurs when the energy budget of the earth system is altered. The resulting change to temperature and circulation induces climate feedbacks, which govern the response of the system to changes, and can buffer the climate system response (in the case of negative feedbacks), or can enhance it (positive feedbacks). This presentation will review the framework for understanding climate forcing and climate feedbacks, particularly with respect to responses to anthropogenic forcing. The largest uncertainty in climate forcing is the induced change in cloudiness due to aerosols. The largest feedback uncertainty is the cloud feedback. The fact that the forcing is dependent on clouds, which are also the largest feedback, makes dis-entangling forcing and feedbacks complex. Several ensembles of a single comprehensive Earth System Model are analyzed to explore the the interaction of feedbacks and forcing, which may provide further constraints on forcing and feedback, and hence future evolution of climate. In these ensembles, cloud feedback can be altered by 50% due to the effects of natural and anthropogenic aerosols. Given the diversity in estimates of cloud feedback in models, some of this spread may be attributable to aerosol (and aerosol-cloud) processes, not clouds alone.