The atmosphere is the integrator of the Earth system. Human emissions of pollutants and long-lived greenhouse gases into the atmosphere have caused dramatic transformations of the planet, altering air quality, climate and nutrient flows in every ecosystem. Understanding the global atmosphere requires an international network of scientists to address these issues. Acknowledgement of this need led to the formation of International Global Atmospheric Chemistry (IGAC) Project in 1990. IGAC facilitates atmospheric chemistry research towards a sustainable world by fostering community, building capacity, and providing leadership. Fostering Community IGAC is an open international community of atmospheric scientists actively collaborating across geographical boundaries and disciplines in order to contribute to addressing the most pressing global change and sustainability issues through scientific research. Building Capacity IGAC builds scientific capacity through its national and regional working groups, its early career scientists program, its biennial conferences and facilitation of numerous thematic workshops. Providing Leadership IGAC provides intellectual leadership by identifying and fostering activities on current and future areas within atmospheric chemistry research that link emissions, atmospheric processes and atmospheric composition to global change and sustainability issues such as human health, climate, ecosystem and how individual and societal responses feedback onto the core research-led foci of IGAC.