Tropospheric SF 6 : Observed latitudinal distribution and trends, derived emissions and interhemispheric exchange time

Sulfur hexafluoride (SF 6 ), an anthropogentically produced compound that is a potent greenhouse gas, has been measured in a number of NOAA GMDL air sampling programs. These include high resolution latitudinal profiles over the Atlantic and Pacific oceans, weekly flask samples from seven remote, globally distributed sites, hourly in situ measurements in rural North Carolina, and a series of archived air samples from Niwot Ridge, Colorado. The observed increase in atmospheric mixing ratio is consistent with an overall quadratic growth rate, at 6.9±0.2% yr −1 (0.24±0.01 ppt yr −1 ) for early 1996. From these data we derive an early 1996 emission rate of 5.9±0.2 Gg SF 6 yr −1 and an interhemispheric exchange time of 1.3±0.1 years.