MACC II (Monitoring Atmospheric Composition and Climate – Interim Implementation) is designed to meet the requirements that have been expressed for prototype operational GMES services for the atmospheric domain. From late-2011 MACC II will continue the operation and development of the GMES service lines established by the MACC project and prepare for its transition in 2014 to become the atmospheric monitoring component of GMES Operations. MACC II will prepare for full operations in terms of continuity, sustainability and availability. It will maintain and further develop the efficiency and resilience of its end-to-end processing system, and will refine the quality of the products of the system. It will adapt the system to make use of observations from new satellites, in particular the first of the atmospheric Sentinels, and will interface with FP7 RTD projects that contribute towards long-term service improvement. MACC II will ensure that its service lines best meet both the requirements of downstream-service providers and end users, and the requirements of the global scientific user community. The service lines will cover air quality, climate forcing, stratospheric ozone and solar radiation. MACC II will deliver products and information that support the establishment and implementation of European policy and wider international programmes. It will acquire and assimilate observational data to provide sustained real-time and retrospective global monitoring of greenhouse gases, aerosols and reactive gases such as tropospheric ozone and nitrogen dioxide. It will provide daily global forecasts of atmospheric composition, detailed air-quality forecasts and assessments for Europe, and key information on long range transport of atmospheric pollutants. It will provide comprehensive web-based graphical products and gridded data. Feedback will be given to space agencies and providers of in situ data on the quality of their data and future observational requirements.