In this project we are initiating a rigorous analysis of the uncertainties in simplified climate models and metrics as applied to assessing options for mitigating climate change from aviation. We are examining a variety of modeling uncertainties to see how they propagate to different metrics that might be used in a policy-making context. We will examine the role of emissions uncertainty (through parametric variations), aircraft operations uncertainty (through parametric variations of where the emissions are deposited, largely focusing on altitude), background atmospheric uncertainty (through parametric variations), and structural model uncertainty (through making back-to-back comparisons of four different models that represent a wide range of model complexity and fidelity). We will do this in the context of different metric choices (e.g., to determine the extent to which different uncertainties or assumptions are more or less influential for different metrics), and in the context of different policy, technology, and operational mitigation options (since the influence of uncertainties is different depending on the options being evaluated).