This ITT, entitled ‘Provision of global inversion-optimised greenhouse gas fluxes and concentrations’, is for providing quantitative estimates of net surface fluxes of greenhouse gases, which are key drivers of the Earth’s climate evolution. Ground-based and now satellite remote-sensing observations allow these fluxes to be monitored. The data provided so far by CAMS have delivered time-series of CH4, CO2 and N2O surface flux fields of high quality. The successful tenderer shall extend the time-series, both forwards and backwards (as far as possible) in time, while maintaining their quality at the highest international standard. Periodically, the successful tenderer will reprocess the whole period in order to reflect improvements in spatial resolution as well as in modelling and data assimilation techniques used for the atmospheric inversions. The documentation of associated errors and comparison with independent observations as well as with similar products that are produced outside of CAMS will also form part of the activities.