Publication Type:Journal Article
Source:Bulletin of the American Meteorological Society, Volume 92, Issue 6, p.S62 (2011)
Perfluorocarbons (PFCs) are extremely long-lived, potent greenhouse gases. PFC-14 (CF4) and PFC-116 (C2F6) have conservative lower limits for atmospheric lifetimes of 50 000 and 10 000 years, respectively, and global warming potentials (100-year time horizon) of 7390 and 12 200, respectively (Ravishankara et al. 1993; Morris et al. 1995; Forster et al. 2007; Montzka et al. 2011). Anthropogenic PFC-14 and PFC-116 were historically emitted as by-products of aluminum production and are now also emitted from the electronics industry. However, the onset and extent of PFC emissions from the electronics industry is poorly known due to limited reporting (Khalil et al. 2003; Worton et al. 2007; EDGAR 2009; Mühle et al. 2010). A small natural source of PFC-14 from degassing of Earth’s crust has been identified (Harnisch and Eisenhauer 1998; Harnisch et al. 2000), which, because of its extraordinarily long atmospheric lifetime, accounts for its significant pre-industrial abundance (Harnisch et al. 1996a, 1996b) of 34.7 ± 0.2 ppt (Mühle et al. 2010), or ~44% of its 2010 abundance. Global average surface concentrations of PFC-14 and PFC-116, respectively (Fig. 2.51), were 50.8 ± 0.8 ppt and 1.0 ± 0.1 ppt in 1978, 77.7 ± 0.1 ppt and 4.01 ± 0.01 ppt in 2009, and 78.3 ± 0.1 ppt and 4.09 ± 0.02 ppt in 2010 (Mühle et al. 2010). PFC-14 rose at ~1.1 ppt yr-1 from the late 1970s to the early 1990s and by ~0.7 ppt yr-1 since that time. PFC-116 rose at ~0.09 ppt yr-1 from the late-1970s to the mid-1990s followed by an increase to ~0.12 ppt yr-1 until the mid-2000s and a subsequent decline to ~0.09 ppt yr-1 afterwards (Mühle et al. 2010).