Global trends and European emissions of tetrafluormethane (CF4), hexafluoroethane (C2F6) and octafluoropropane (C3F 8)
Perfluorocarbons (PFCs) are amongst the most potent greenhouse gases listed under the United Nations Framework Convention on Climate Change (UNFCCC). With atmospheric lifetimes on the order of thousands to tens of thousands of years, PFC emissions represent a permanent alteration to the global atmosphere on human timescales. While the industries responsible for the vast majority of these emissions – aluminium smelting and semi-conductor manufacturing – have made efficiency improvements and introduced abatement measures, the global mean mole fractions of three PFCs, namely tetrafluoromethane (CF, PFC-14), hexafluoroethane (CF, PFC-116) and octafluoropropane (CF, PFC-218), continue to grow. In this study, we update baseline growth rates using in situ high-frequency measurements from the Advanced Global Atmospheric Gases Experiment (AGAGE) and, using data from four European stations, estimate PFC emissions for northwest Europe. The global growth rate of CF decreased from 1.3 ppt yr in 1979 to 0.6 ppt yr around 2010 followed by a renewed steady increase to 0.9 ppt yr in 2019. For CF, the growth rate grew to a maximum of 0.125 ppt yr around 1999, followed by a decline to a minimum of 0.075 ppt yr in 2009, followed by weak growth thereafter. The CF growth rate was around 0.007 ppt yr until the early 1990s and then quickly grew to a maximum of 0.03 ppt yr in 2003–2004. Following a period of decline until 2012 to 0.015 ppt yr, the growth rate slowly increased again to 0.017 ppt yr in 2019. We used an inverse modelling framework to infer PFC emissions for northwest Europe. No statistically significant trend in regional emissions was observed for any of the PFCs assessed. For CF, European emissions in early years were linked predominantly to the aluminium industry. However, we link large emissions in recent years to a chemical manufacturer in northwest Italy. Emissions of CF are linked to a range of sources, including a semi-conductor manufacturer in Ireland and a cluster of smelters in Germany's Ruhr valley. In contrast, northwest European emissions of CF are dominated by a single source in northwest England, raising the possibility of using emissions from this site for a tracer release experiment.