This presentation will discuss the development and use of a Perturbed Parameter Ensemble (PPE) in the Community Earth System Model. The methodology for building and running the PPE is described, with discussion of the application of similar methods for E3SM. Then an example is presented of using the PPE to explore the relationships between aerosol forcing of climate and cloud feedback. Aerosols alter then microphysical properties of clouds (drop/crystal number and size), with resulting effects on cloud macrophysical properties (cloud extent, lifetime, water mass and precipitation). These changes to clouds have effects on climate, specifically the radiative effects of clouds. In addition, by altering the microphysical and macrophysical state of clouds, aerosols may also alter cloud feedbacks: the response of clouds to the change in surface temperature. This work will explore the relationships between aerosols and cloud feedbacks using controlled experiments and the PPE, with the goal at not just parameter sensitivity, but the processes underlying that sensitivity.