A pragmatic protocol for characterising errors in atmospheric inversions of methane emissions over Europe

International audienceThis study aims at estimating errors to be accounted for in atmospheric inversions of methane (CH4)emissions at the European scale. Four types of errors are estimated in the concentration space over themodel domain and at selected measurement sites. Furthermore, errors in emission inventories are estimatedat country and source sector scales. A technically ready method is used, which is implemented by running aset of simulations of hourly CH4 mixing ratios for 2015 using two area-limited transport models at threehorizontal resolutions with multiple data sets of emissions and boundary and initial conditions as inputs. Theobtained error estimates provide insights into how these errors could be treated in an inverse modellingsystem for inverting CH4 emissions over Europe. The main results show that sources of transport errors maybetter be controlled alongside the emissions, which differs from usual inversion practices. The average totalconcentration error is estimated at 29 ppb. The assessed error of total CH4 emissions is 22% and emissionerrors are heterogeneous at sector (23–49%) and country scales (16–124%), with largest errors occurring inthe waste sector due to uncertainties in activity data and emission factors and in Finland due to uncertaintiesin natural wetland emissio