Levels of a powerful greenhouse gas are four times as high as previously thought, according to new measurements released on Thursday.
New analytical techniques show that about 5,400 metric tons of nitrogen trifluoride are in the atmosphere, with amounts increasing by about 11 percent per year.
Ray Weiss of the Scripps Institution of Oceanography in La Jolla, California, and colleagues said it had not been possible to accurately measure this gas before.
They said nitrogen trifluoride is 17,000 times more effective at warming the atmosphere than an equal mass of carbon dioxide, although it does not yet contribute much to global warming.
Previous estimates had put levels of the gas at less than 1,200 metric tons in 2006.