Sulfur hexafluoride
According to the Intergovernmental Panel on Climate Change,  is the most potent greenhouse gas that it has evaluated, with a global warming potential (GWP) of 22,800 times that of  when compared over a 100-year period.  Measurements of SF6 show that its global average mixing ratio has increased by about 0.2 ppt per year to over 7 ppt.  Sulfur hexafluoride is also extremely long-lived. It is inert in the troposphere and stratosphere. It has an estimated atmospheric lifetime of 800–3200 years.  is very stable. (For countries reporting their emissions to the UNFCCC, a GWP of 23,900 for  was suggested at the third Conference of the Parties: GWP used in Kyoto protocol). Average global SF6 concentrations increased by about seven percent per year during the 1980s and 1990s, mostly as the result of its use in the magnesium production industry, and by electrical utilities and electronics manufacturers. Given the low amounts of SF6 released compared to carbon dioxide, its overall contribution to global warming is estimated to be less than 0.2 percent.