The Expert Team on the Atmospheric Composition Network Design and Evolution undertakes a range of core activities, including reviewing user requirements for observations across three key atmospheric composition application areas—monitoring, forecasting, and urban environments—in support of the WMO Rolling Review of Requirements (RRR). It also works to align and harmonize requirements for atmospheric composition variables across other WMO application areas, ensures that these requirements are regularly updated within the OSCAR database, evaluates existing observational capabilities against identified needs, and formulates recommendations for integrated network design through Statements of Guidance for each application area, while providing advice on network development to the GAW Programme and relevant partners.