Since the climate agreement of Paris, the playing field for CO2 monitoring has dramatically changed. This relates to the fact that a fixed temperature threshold was chosen in Paris that translates almost immediately into an allowable emission target for fossil fuels, but it also underscored the limited amount of time we have to achieve this reduction. This puts enormous pressure on the development of adequate monitoring schemes for fossil fuel emission (reductions). It requires a shift in determining diffuse, biospheric fluxes towards point sources of emission by power plants and cities.

The network to achieve this is ready in blueprint, but by far not in practice. The in situ network is designed for biospheric fluxes and far less for fossil fuel emissions. Satellite systems that can bridge gaps between in situ observation are still in developmental stage, even if in orbit. The coordination of these systems with modelling effort requires an effort that we have not seen since the development of NWP.

We urgently need assessments of the capability to determine country or small region scale budgets with mesoscale model inversions, using existing data sources. At the same time the in situ networks need to be optimized further towards fossil fuel monitoring, without losing the current networks’ long term monitoring obligations. There is some hope that mesoscale models plus additional high-resolution RS data can constrain and reduce the uncertainties that increase from large scale inversion going to smaller scales, and from local site observations going to larger scales. Where these meet, a future monitoring and observation system will need to bring the constraints.