The greenhouse gas with the largest known warming potential is sulfur hexafluoride (SF6), which persists in the atmosphere for a long time (580-3200 years). SF6 is used in processes for electric power transmission and distribution, through electric power plants, transmission power lines, and transformers, as well as electronic product manufacturing. Although existing observations from the US Environmental Protection Agency (EPA) show a decreasing trend of SF6 in response to US mitigation efforts, SF6 emission magnitudes and distributions have substantial uncertainties. To circumvent this problem, researchers used NOAA’s ground-based and airborne measurements of SF6 to estimate SF6 emissions from the United States between 2007 and 2018.
The results of this study, funded in part by the Climate Program Office’s Atmospheric Chemistry, Carbon Cycle and Climate (AC4) and Climate Observations and Monitoring (COM) Programs, show that while the decreasing trend is indeed occurring, the widely used and accepted EPA dataset underestimates the total amount of SF6 in the air by up to 250%. The discrepancy between the results in this study, published in Atmospheric Chemistry and Physics, and the national inventory suggests that emissions from the electric power and manufacturing industries are being under-reported. A group of researchers, including AC4- and COM- supported scientists Lei-Hu, Stephen Montzka, Arlyn Andrews, and Colm Sweeney of NOAA’s Global Monitoring Laboratory (GML), also identified elevated SF6 during the winter. The authors hypothesize that leakage and other issues with electric power transmission and distribution equipment could be responsible for these emissions, and could be improved by servicing and sealing these faulty materials. This research contributes to a growing body of work supported by AC4 and COM to use atmospheric observations to quantify the effects of greenhouse gases other than carbon dioxide on the US.