How can in-situ observations constrain and improve modeling of aerosol indirect effects? (Invited Speaker)

The effects of airborne particulate matter (“aerosols”) on clouds (known as the “aerosol indirect effect”) are potentially one of the largest and uncertain anthropogenic impacts on climate. Furthermore the indirect effect is thought to have a net climatic cooling effect, largely contributing to the uncertainty in predictions of climate sensitivity to greenhouse gases. This uncertainty originates from the complex and multi-scale nature of aerosol-cloud interactions, which often forces climate models to use empirical approaches for their representation. This talk will present ongoing efforts on incorporating theoretically-based and computationally efficient links between aerosols and clouds within a global climate model framework. We will also present methods for constraining and evaluating these novel modeling approaches by using in-situ observations of cloud condensation nuclei, chemical composition and aerosol-cloud droplet number from recent field missions. Finally, we present work on robustly constraining important sources of predictive uncertainty by coupling the in-situ observations with global climate modeling.