Abstract
Abstract. 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 (CF4, PFC-14), hexafluoroethane (C2F6, PFC-116) and octafluoropropane (C3F8, 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 CF4 decreased from 1.3 ppt yr−1 in 1979 to 0.6 ppt yr−1 around 2010 followed by a renewed steady increase to 0.9 ppt yr−1 in 2019. For C2F6, the growth rate grew to a maximum of 0.125 ppt yr−1 around 1999, followed by a decline to a minimum of 0.075 ppt yr−1 in 2009, followed by weak growth thereafter. The C3F8 growth rate was around 0.007 ppt yr−1 until the early 1990s and then quickly grew to a maximum of 0.03 ppt yr−1 in 2003–2004. Following a period of decline until 2012 to 0.015 ppt yr−1, the growth rate slowly increased again to ∼ 0.017 ppt yr−1 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 CF4, 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 C2F6 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 C3F8 are dominated by a single source in northwest England, raising the possibility of using emissions from this site for a tracer release experiment.
Highlights
Perfluorocarbons (PFCs) – fully fluorinated hydrocarbons – are a group of extremely potent greenhouse gases that are used extensively in the electronics and semi-conductor industry and are emitted as a byproduct of aluminium and rare-earth metal smelting
As a consequence of their high global warming potentials (GWPs), PFCs were listed under the Kyoto “basket”, a collection of gases for which regulation on their emissions was introduced under the Kyoto Protocol (UNFCCC, 2009)
Production of primary aluminium dropped by roughly 6 % (∼ 200 000 metric tonnes) between 2008 and 2009 (IAI, 2020)
Summary
Perfluorocarbons (PFCs) – fully fluorinated hydrocarbons – are a group of extremely potent greenhouse gases that are used extensively in the electronics and semi-conductor industry and are emitted as a byproduct of aluminium and rare-earth metal smelting. As a consequence of their high global warming potentials (GWPs), PFCs were listed under the Kyoto “basket”, a collection of gases for which regulation on their emissions was introduced under the Kyoto Protocol (UNFCCC, 2009). Countries listed under Annex 1 of the protocol are required to report annual PFC emissions to the United Nations Framework Convention on Climate Change (UNFCCC). Harnisch and Eisenhauer (1998) estimated that the fluorite reservoir is sufficient to maintain an atmospheric background mole fraction of approximately 40 ppt. This was refined to 34.05 ± 0.33 ppt (Trudinger et al, 2016)
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