The chemical composition of the atmosphere controls the climate system, the quality of the air that we breathe and the amount of ultraviolet radiation to which we are exposed. Human energy use and agricultural activities have profoundly altered this composition leading to regional and global climate change, widespread air pollution and stratospheric ozone depletion. Dr. Unger applies numerical modeling and integrated studies to advance understanding of interactions between atmospheric chemistry and climate. The goal is to support effective decision-making and the development of smart climate policy.