Perfluorocarbons (PFCs) are very potent and long-lived greenhouse gases in the atmosphere, released predominantly during aluminium production and semiconductor manufacture. They have been targeted for emission controls under the United Nations Framework Convention on Climate Change.
Here we present the first continuous histories of the abundance and emissions of three PFCs (CF4, C2F6 and C3F8) from 1800 to 2014. The histories were derived from atmospheric measurements made at stations in the AGAGE (Advanced Global Atmospheric Gases Experiment) global network, archived air samples and air extracted from polar firn or ice in both hemispheres.
The firn and ice core measurements allow us to determine the atmospheric levels of these PFCs in the 19th century, before significant anthropogenic influence. CF4 was stable at 34.1 ± 0.3 ppt through the 19th century, with levels maintained by natural emissions from rocks (fluorites and granites) released by tectonic activity and weathering. C2F6 and C3F8 were below measurement detection limits of 0.002 and 0.01 ppt, respectively.
We found a significant peak in CF4 and C2F6 emissions around 1940, most likely due to the high demand for aluminium during World War II, for example for construction of aircraft, but these emissions were nevertheless much lower than in recent years. Emissions increased rapidly from around 1960, to peak in 1980 (CF4) or early-to-mid-2000s (C2F6 and C3F8). Significant mitigation efforts by both the aluminium and semiconductor industries have led to strong decreases in emissions, despite the continued increase in global aluminium production. We saw a temporary reduction of around 15% in CF4 emissions in 2009, presumably associated with the impact of the Global Financial Crisis on aluminium and semiconductor production.
The decrease in emissions that followed the emissions peaks appears to have slowed and possibly stopped in recent years. Continued effort from all PFC generating industries is urgently needed to reduce the emissions of these potent greenhouse gases, which, once emitted, will stay in the atmosphere essentially permanently (on human timescales) and contribute to radiative forcing.
Related article:
Atmospheric abundance and global emissions of perfluorocarbons CF4, C2F6 and C3F8 since 1800 inferred from ice core, firn, air archive and in situ measurements. Trudinger, C.M.; P.J. Fraser; D.M. Etheridge; W.T. Sturges; M.K. Vollmer; M. Rigby; P. Martinerie; J. Mühle; D.R. Worton; P.B. Krummel; L.P. Steele; B.R. Miller; J. Laube; F.S. Mani; P.J. Rayner; C.M. Harth; E. Witrant; T. Blunier; J. Schwander; S.J. O’Doherty and M. Battle (2016), Atmospheric Chemistry and Physics 16, 11733–11754