History of atmospheric SF 6 from 1973 to 2008

We present atmospheric sulfur hexafluoride (SF 6) mole fractions and emissions estimates from the 1970s to 2008. Measurements were made of archived air sam- ples starting from 1973 in the Northern Hemisphere and from 1978 in the Southern Hemisphere, using the Ad- vanced Global Atmospheric Gases Experiment (AGAGE) gas chromatographic-mass spectrometric (GC-MS) systems. These measurements were combined with modern high- frequency GC-MS and GC-electron capture detection (ECD) data from AGAGE monitoring sites, to produce a unique 35-year atmospheric record of this potent greenhouse gas. Atmospheric mole fractions were found to have increased by more than an order of magnitude between 1973 and 2008. The 2008 growth rate was the highest recorded, at 0.29± 0.02 pmol mol 1 yr 1 . A three-dimensional chemical transport model and a minimum variance Bayesian inverse method was used to estimate annual emission rates using the measurements, with a priori estimates from the Emis- sions Database for Global Atmospheric Research (EDGAR, version 4). Consistent with the mole fraction growth rate maximum, global emissions during 2008 were also the high- est in the 1973-2008 period, reaching 7.4± 0.6 Gg yr 1 (1-