Atmospheric chemistry, as a modern discipline, can be considered to have originated in 1931, when Sydney Chapman, distinguished British physicist, formulated a chemical mechanism for the formation of stratospheric ozone. The foundations of understanding tropospheric chemistry were laid in the early 1950s by Arie Haagen-Smit, a bioorganic chemist at the California Institute of Technology, who described ozone formation in the Los Angeles Basin as resulting from reactions involving volatile organic compounds and oxides of nitrogen. The essential reactive species in tropospheric chemistry remained unknown until the early 1970s, when the central role of the hydroxyl radical as the troposphere's “detergent” was revealed. The existence of particles in the air (aerosols) had long been recognized, but it was not until the past 50 years that instrumentation was developed that is capable of determining the size distribution and composition of atmospheric aerosols.
Threats to stratospheric ozone made headlines in the early 1970s, when Harold Johnston at the University of California, Berkeley, published calculations of the effect on stratospheric ozone of a proposed fleet of supersonic aircraft. Johnston's work was followed shortly thereafter by the revelation of the stratospheric chemical impact of chlorofluorocarbons, widely used as refrigerants and in consumer products, by F. Sherwood Rowland and Mario Molina of the University of California, Irvine. For their penetrating insights into atmospheric chemistry, Rowland, Molina, and Paul Crutzen of the Max Planck Institute for Chemistry in Mainz, Germany, received the 1995 Nobel Prize in Chemistry.