This report explores how climate change will influence air quality in California through changes to meteorology and emissions. The report addresses the challenging nature of the high spatial resolution needed to represent Californias air basins and the long analysis periods needed to capture El-Nino Southern Oscillation (ENSO) meteorological cycles. Previous studies have not adequately addressed these issues for California. Three study methods were employed: (1) model perturbations (O3 and PM), (2) statistical downscaling (O3), and (3) dynamic downscaling (PM). Model perturbation studies for historical ozone episodes suggest that concentrations increase when maximum daytime temperatures increase, and that the climate change penalty will offset much of the benefit from future emissions control programs.