A new NOAA analysis shows U.S. emissions of the super-potent greenhouse gas sulfur hexafluoride (SF₆) have declined between 2007-2018, likely due to successful mitigation efforts by the Environmental Protection Agency (EPA) and the electric power industry.

At the same time, significant disparities that existed previously between NOAA’s estimates, which are based on atmospheric measurements, and EPA’s estimates, which are based on a combination of reported emissions and industrial activity, have narrowed following the establishment of the EPA's Greenhouse Gas Reporting Program. The findings, published in the journal Atmospheric Chemistry and Physics, also suggest how additional emissions reductions might be achieved.

Researchers from NOAA’s Global Monitoring Laboratory (GML), working with the EPA, CIRES, and the University of Maryland, estimated U.S. SF₆ emissions for the first time from atmospheric measurements collected at a network of tall towers and aircraft in NOAA’s Global Greenhouse Gas Reference Network. The researchers provided an estimate of SF₆ emissions independent from the EPA’s estimate, which is based on reported SF₆ emissions for some industrial facilities and on estimated SF₆ emissions for others.

“We observed differences between our atmospheric estimates and the EPA’s activity-based estimates,” said study lead author Lei Hu, a federal researcher in GML who was a CIRES scientist at the time of the study. “But by closely collaborating with the EPA, we were able to identify processes potentially responsible for a significant portion of this difference, highlighting ways to improve emission inventories and suggesting additional emission mitigation opportunities in the future.”

Read more from NOAA Research here.