Perfluorocarbons in the global atmosphere: tetrafluoromethane, hexafluoroethane, and octafluoropropane

• Published in: Atmospheric Chemistry and Physics
• Main Authors: J. Mühle, A. L. Ganesan, B. R. Miller, P. K. Salameh, C. M. Harth, B. R. Greally, M. Rigby, L. W. Porter, L. P. Steele, C. M. Trudinger, P. B. Krummel, S. O'Doherty, P. J. Fraser, P. G. Simmonds, R. G. Prinn, R. F. Weiss
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2010
• Subjects: Physics; QC1-999; Chemistry; QD1-999; Antarctic; Greenland; Antarc*
• Online Access: https://doi.org/10.5194/acp-10-5145-2010; https://doaj.org/article/1af6462c0655433cb01730653a922e3c

We present atmospheric baseline growth rates from the 1970s to the present for the long-lived, strongly infrared-absorbing perfluorocarbons (PFCs) tetrafluoromethane (CF 4 ), hexafluoroethane (C 2 F 6 ), and octafluoropropane (C 3 F 8 ) in both hemispheres, measured with improved accuracies (~1–2%) and precisions (<0.3%, or <0.2 ppt (parts per trillion dry air mole fraction), for CF 4 <1.5%, or <0.06 ppt, for C 2 F 6 <4.5%, or <0.02 ppt, for C 3 F 8 within the Advanced Global Atmospheric Gases Experiment (AGAGE). Pre-industrial background values of 34.7±0.2 ppt CF 4 and 0.1±0.02 ppt C 2 F 6 were measured in air extracted from Greenland ice and Antarctic firn. Anthropogenic sources are thought to be primary aluminum production (CF 4 , C 2 F 6 , C 3 F 8 ), semiconductor production (C 2 F 6 , CF 4 , C 3 F 8 ) and refrigeration use (C 3 F 8 ). Global emissions calculated with the AGAGE 2-D 12-box model are significantly higher than most previous emission estimates. The sum of CF 4 and C 2 F 6 emissions estimated from aluminum production and non-metal production are lower than observed global top-down emissions, with gaps of ~6 Gg/yr CF 4 in recent years. The significant discrepancies between previous CF 4 , C 2 F 6 , and C 3 F 8 emission estimates and observed global top-down emissions estimated from AGAGE measurements emphasize the need for more accurate, transparent, and complete emission reporting, and for verification with atmospheric measurements to assess the emission sources of these long-lived and potent greenhouse gases, which alter the radiative budget of the atmosphere, essentially permanently, once emitted.