This study aims at estimating errors which are to be accounted for in atmospheric inversions of methane (CH4) emissions at the European scale. A technically ready and computationally inexpensive method is used. Four types of errors are estimated in the concentration space over the model domain and at selected measurement sites. Furthermore, errors in emission inventories are estimated at the country and source sector scales. The method is implemented by running a set of simulations of hourly CH4 mixing ratios for 2015 using two area-limited transport models at three horizontal resolutions with three emission inventories and two sets of boundary and initial conditions as inputs. The obtained error estimates provide insights into how these errors could be treated in an inverse modelling system for inverting CH4 emissions over Europe. The main results include that sources of transport errors may better be controlled alongside the emissions, which differs from usual inversion practices. The total concentration error is 29 ppb and error patterns cover a number of measurement sites. The error of total CH4 emissions is 22% and emission errors
are heterogeneous at sector (23-49%) and country scales (16-124%), with largest errors occurring in the waste sector.