To better understand how aerosols affect the atmosphere and Earth system processes, historical emissions data are a key input for modeling and analyses. A research team produced a new, robust data set covering the years 1750–2014 for carbonaceous aerosols, and chemically reactive gases—which are precursors to ozone, aerosols such as sulfate and nitrate, and carbon dioxide. To organize, analyze, and provide the data, the team developed a data system called the Community Emissions Data System.