ICOS Cities (a.k.a. PAUL – Pilot Applications In Urban Landscapes) is a large project funded by the EU Horizon 2020 instrument’s Green Deal call. The project focuses on monitoring systems for greenhouse gas emissions (GHG) in densely populated urban areas in the Europe. The role of the NODUS team is to benchmark existing services and to develop new service prototypes for the end users of observational emission data such as city administrators.