Sources, Regional Scaling and Validation of Methane Emissions from the Netherlands and Northwest Europe

In this study, carried out in the frame of the Dutch National Research Programme on Global Air Pollution and Climate Change three connected validation procedures have been applied for a methane emission inventory, namely:

1. the comparison of emission inventories
2. the comparison of modelled with observed methane concentrations
3. the comparison of bottom-up emission estimates with inversely modelled emission estimates.

There is a good overall correspondence between the consistent bottom-up METDAT emission inventory and the National Communication data. However, on a country level and on a source category level large discrepancies could been found. The analysis of concentration measurements gives a clear indication of the contribution from the different areas. Time series analysis as such appeared not to be suitable for verification purposes in this study. The technique of emission verification by modelling methane concentrations with the bottom-up estimated emission data as input for the model and comparing the results with measured concentrations has been proven quite successful, at least on a regional scale. The technique applied so far is however not able to indicate whether the individual sources are estimated realistically as well. At present, the technique of inverse modelling has not proven to be robust enough to produce stable results of satisfactory accuracy on a regional scale. At least, there is a lack of sufficient measurement data, e.g. from neighbouring countries and a need for the improvement of background concentration data (by global models).