observations are needed for the generation and updating of global climate products and derived information. GCOS and its partners are developing ways of improving the generation and supply of data products relating to the ECVs. Expert Panels Three expert panels have been established by the GCOS Steering Committee to define the observations needed in each of the main global domains - Atmosphere, oceans, and land - to prepare specific programme elements and to make recommendations for implementation. GCOS is both supported by and supports the international scientific community, and therefore the three expert panels are co-sponsored by the World Climate Research Programme (WCRP). The Atmospheric, Ocean, and Terrestrial Observation Panel for Climate gather scientific and technical experts in the respective areas to generate inputs from these fields to the climate observing community. Those expert panels report to the GCOS Steering Committee, and have been established to define the observations needed in each of the main global domains to prepare scientific programme-elements and to make recommendations for implementation. Atmospheric Observation Panel for Climate (AOPC) AOPC was established in recognition of the need for specific scientific and technical input concerning atmospheric observations for climate. Its aim is to ensure the quality, long-term homogeneity and continuity of data needed. AOPC supports and is supported by the WMO Integrated Global Observing System (WIGOS). Key activities of AOPC are: - Assessing the current state of the atmospheric component of the global observing system for climate and identify its gaps and adequacies; - Securing the implementation of designated GCOS Networks and promote the establishment and enhancement of new and current systems to provide long-term and consistent data and information for Essential Climate Variables, such as earth radiation budget, surface radiation, greenhouse gases, water vapour, clouds and aerosols; - Liaising with relevant research, operational and end-user bodies in order to determine and maintain the requirements for data to monitor, understand and predict the dynamical, physical and chemical state of the atmosphere and its interface on seasonal and multi-decadal time scales, on both global and regional levels; - Promoting the transfer and accessibility to the user community, as well as the rehabilitation of historical observational and proxy climate data sets. Ocean Observations Panel for Climate (OOPC) OOPC, co-sponsored by GOOS, as well as GCOS and WCRP, is a scientific and technical advisory group charged with making recommendations for a sustained global ocean observing system for climate in support