Evidence of ongoing SF6 emissions in Germany

Sulfur hexafluoride (SF6) is a greenhouse gas with an estimated atmospheric lifetime of about 850-1280 years and a global warming potential of 24,700 over 100 years. As this strong greenhouse gas continues to be used in switchgear, circuit breakers, transformers and in other applications; monitoring emissions worldwide is essential. Some global and regional measurement networks, including the AGAGE, NOAA and ICOS programmes, have been measuring surface-based SF6 for several years. Through these measurements and inverse modelling, it has been shown that there are still significant SF6 emissions in western Europe, the largest source estimated to be in southern Germany. Here we present the first time series of all available SF6 observations in Germany to localise the most important source regions of SF6. Data from the following stations were used: Taunus Observatory (AGAGE), Zugspitze / Schneefernerhaus (UBA Germany, GAW, ICOS), Karlsruhe (DWD, ICOS), Hohenpeissenberg (DWD, GAW, ICOS), Lindenberg (DWD, ICOS), Ochsenkopf (MPI-BGC, ICOS), Steinkimmen (ICOS), Gartow (ICOS) and Schauinsland (UBA Germany, GAW, ICOS). This distribution of observation sites provides good resolution of SF6 emissions in Germany. Despite the annual National Inventory Reports to the UNFCCC suggesting a decline in SF6 emissions in Germany, observations show continued episodes of elevated mixing ratios. This is indicative of continuing local emissions in Germany. Depending on wind direction, the highest levels of SF6 were measured at Zugspitze, Schauinsland, Karlsruhe and the Taunus Observatory, consistent with a source in southern to south-western Germany.  The Karlsruhe station stands out in particular, with maximum mixing ratios of more than 70 ppt. In addition to an analysis of such pollution events, the observations are also used in the top-down inverse model InTEM (Inversion Technique for Emission Modelling) coupled to the atmospheric transport model NAME (Numerical Atmospheric Dispersion Modelling Environment).