Inversion modelling products with uncertainties

During the last period of the ICOS-Cities project, several inversion systems have been developed to produce fossil fuel and biogenic CO2 emissions over Paris, Munich, and Zurich. These inversion systems produce their own associated uncertainties (so-called posterior uncertainties), often impacted by incorrect error specification. Indeed, the various sources of uncertainties in inversion systems, such as transport errors, inventory errors, or biogenic model errors, remain difficult to characterize rigorously. Here, we document the uncertainties associated with fossil fuel emissions primarily, using independent measurements (i.e. direct emissions from eddy-flux towers, mass-balance estimate from 14CO2 flask measurements) and we inter-compare inverse emissions using two different inversion systems. These additional analyses help us document and characterize the actual emissions uncertainties to improve the inverse emissions estimate and their interpretation.