Improving measurements of SF₆ for the study of atmospheric transport and emissions

Abstract. Sulfur hexafluoride (SF₆) is a potent greenhouse gas and useful atmospheric tracer. Measurements of SF₆ on global and regional scales are necessary to estimate emissions and to verify or examine the performance of atmospheric transport models. Typical precision for common gas chromatographic methods with electron capture detection (GC-ECD) is 1–2%. We have modified a common GC-ECD method to achieve measurement precision of 0.5% or better. Global mean SF₆ measurements were used to examine changes in the growth rate of SF₆ and corresponding SF₆ emissions. Global emissions and mixing ratios from 2000–2008 are consistent with recently published work. More recent observations show a 10% decline in SF₆ emissions in 2008–2009, which seems to coincide with a decrease in world economic output. This decline was short-lived, as the global SF₆ growth rate has recently increased to near its 2007–2008 maximum value of 0.30±0.03 pmol mol⁻¹ (ppt) yr⁻¹ (95% C.L.).