Evidence for under‐reported western European emissions of the potent greenhouse gas HFC‐23

Western European emission inventories of the potent greenhouse gas trifluoromethane (HFC‐23) are validated at a country level by combining 2‐hourly atmospheric in‐situ measurements at Jungfraujoch (Switzerland) and Mace Head (Ireland) with Lagrangian transport simulations. HFC‐23 has an atmospheric lifetime of ∼270 yr and a 100‐yr global warming potential (GWP) of 14,800 and is unintentionally produced during the manufacture of chlorodifluoromethane (HCFC‐22). For the study region we derive emissions of 144–216 Mg/yr for July 2008–July 2010, which are 60–140% higher than the official emissions gathered from the national reports for the year 2009. The largest discrepancy is found for Italy, where our estimate of 26–56 Mg/yr exceeds the national inventory (2.6 Mg/yr) by more than an order of magnitude. These findings suggest that non‐reported emissions from Annex 1 countries partly explain the recently derived gap between global bottom‐up and top‐down HFC‐23 emission estimates. The results presented here provide independent information to relevant authorities on effective reporting of HFC‐23 emissions, and demonstrate the potential of atmospheric measurements for real‐world verification of greenhouse gas emissions.