Smith’s research has focused on long-term socioeconomic scenarios, the interface between socioeconomic systems and the climate system, and the interactions between air pollution and climate. Smith is principal investigator of the Community Emissions Data System (CEDS) project that produces global historical air pollutant emissions over the industrial era (1750-present). Smith also works with the Global Change Assessment Model (GCAM), which he and collaborators are currently using to examine multi-sector interactions between the energy system and air-pollutant emissions from global to regional scales.