The project is a preparation of Danish participation in the ESFRI project ICOS. (Integrated Carbon Observation System). The ICOS Research Infrastructure aims to initiate across Europe and adjacent regions a network for standardized long-term high precision monitoring of greenhouse gas concentrations (CO2, CH4, N2O, SF6, CO and their isotopes) and ecosystem fluxes (CO2, H2O, heat) together with their ecosystem component fluxes. These measurements will allow daily assessments of sources and sinks at scales down to about 10 km, and these data will be a basis for understanding the exchange processes between the atmosphere, the terrestrial surface and the ocean. The Danish preparatory project is lead by Risø-DTU and is conducted in cooperation with Copenhagen University and Roskilde University.