A high resolution gridded European Atmospheric Potential Oxygen (APO) inventory 2005 - 202

Accurately attributing CO2 emissions is key to mitigating greenhouse gas (GHG) emissions under the European Green Deal. However, this poses significant challenges. To this end, the CO2MVS Research on Supplementary Observations (CORSO) project will support establishing the new European anthropogenic CO2 emissions Monitoring and Verification Support capacity (CO2MVS), which is being implemented within the Copernicus Atmosphere Monitoring Service (CAMS). To better separate the contribution of fossil fuels and natural sources to atmospheric CO2 emissions, CORSO will be using supplementary observations focused on co-emitted species, as well as other auxiliary observations, such as gaseous tracers. One such tracer is Atmospheric Potential Oxygen (APO), that integrates both emitted CO2 and the corresponding O2 uptake through the derivation of an oxidative ratio (OR). Here we present  the development and further refinement of a regional APO inventory that spans the European domain from 2005 to 2020 at a resolution of 6 x 6 km. The inventory builds upon earlier work conducted under the CO2 Human Emissions (CHE) project for the year 2015, leveraging CO2 and co-emitted species emissions from the CAMS-REG-v4 dataset produced by TNO. It expands on the methodology used to develop the COFFEE global dataset (Steinbach et al., 2011) by introducing several improvements. Oxygen consumption from fossil fuel combustion is dominated by CO2 but we also incorporated the O2 uptake from the production of the co-emitted species NOx, CO and SOx. Furthermore, the oxidative ratios associated with sea shipping are refined using detailed fuel classification data from the Finnish Meteorological Institute (FMI). We will compare the results against global APO datasets, including COFFEE and GridFED, and drawing conclusions on consistency across the different inventories. Finally, we aim to collaborate closely with end-users of the inventory under the CORSO project, to assess the interpretability of results and ascertain the dataset’s relevance in supporting robust modelling practices. Through these refinements, we aim to contribute to the growing body of knowledge dedicated to more accurately quantify anthropogenic CO2 emissions, to help inform effective policies that support nations in achieving their objectives under the European Green Deal.