This contract will provide quantitative estimates of net surface fluxes of greenhouse gases. The Contractor will extend the time-series of CH4, CO2 and N2O surface flux fields both forwards and backwards in time while maintaining their high quality. Furthermore, the Contractor will periodically reprocess the whole period 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. Finally, specific developments will be included to further improve the data products.