Graph showing global-averaged monthly mean atmospheric sulphur hexafluoride (SF6) levels as determined from marine surface sites since 2001. The levels are given as a dry air mole fraction, which is the number of sulphur hexafluoride molecules divided by the total number of molecules in a sample after water vapour has been removed. Sulphur hexafluoride is the most potent greenhouse gas yet evaluated, with a warming potential nearly 24,000 times that of carbon dioxide over a 100 year period. Man-made sources of sulphur hexafluoride are magnesium and electronics production. The red lines and circles are globally averaged monthly mean values centered on the middle of each month. The black line and squares show the long-term trend (similar to a 12-month running mean) where the average seasonal cycle has been removed.