Interpreting model simulations and addressing uncertainty are key to understanding the modeling of atmospheric, land, ocean, and socio-economic phenomena and processes. These approaches are also critical in evaluating the possible consequences and risks of model predictions/projections. We seek contributions in both philosophical and scientific model interpretation, identifying or describing sources of uncertainty, and evaluating models against observations. We also will consider methods that quantify uncertainty through both forward (sensitivity analyses) and inverse modeling (optimization/calibration) in all components of climate, earth system, and integrated assessment models, at various spatial and temporal scales.