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

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 2F6), and octafluoropropane (C 3F8) 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 CF4; <1.5%, or <0.06 ppt, for C2F6; <4.5%, or <0.02 ppt, for C3F8) within the Advanced Global Atmospheric Gases Experiment (AGAGE). Pre-industrial background values of 34.7±0.2 ppt CF4 and 0.1±0.02 ppt C2F6 were measured in air extracted from Greenland ice and Antarctic firn. An- thropogenic sources are thought to be primary aluminum production (CF4, C2F6, C3F8), semiconductor production (C2F6, CF4, C3F8) and refrigeration use (C3F8). Global