GLOBAL INCREASE OF SF6 OBSERVED IN THE ATMOSPHERE

High precision long-term observations of the trace gas sulphur hexafluoride (SF6) in background air at Neumayer station, Antarctica (1986-1991), and at Izana observatory, Tenerife (1991-1992), are presented. Since the very first measurements in 1970 (0.03 pptv), the purely anthropogenic greenhouse gas SF6 has increased by two orders of magnitude to a global mean value of 2.8 pptv in 1992. The observations can best be fitted by a quadratic curve with a recent increase rate of 8.3% yr-1. A significant north-south gradient of 0.29 pptv is observed. From this gradient an interhemispheric exchange time of 1.4 years is derived. A modeled atmospheric budget history agrees reasonably well with estimates of global SF6 production rates and leads to an extrapolated SF6 concentration of about 20 pptv for the year 2030.