But if the emissions of CFC-11 continue, recovery could be delayed by about a decade, said Stephen A. Montzka, the lead author of a report detailing the findings published Wednesday in the journal Nature.
“We’re raising the flag to say, look, this is not what we hope happens for the ozone layer,” said Dr. Montzka, a research chemist at the Earth System Research Laboratory in Boulder, Colo., a part of the National Oceanic and Atmospheric Administration.
David Doniger, director of the climate and clean energy program of the Natural Resources Defense Council, an environmental group in Washington, said the new emissions were “bad for the ozone layer and bad for climate change.”
“It’s worrisome that someone’s cheating,” he said.
But Mr. Doniger noted that the Montreal Protocol, which has been signed by nearly 200 countries, has a strong track record of compliance, with countries often reporting their own violations. “There’s a reasonable chance we’ll figure out what’s happening here,” he said.
Keith Weller, a spokesman for the United Nations Environment Program, which helps implement the protocol, said the findings would be presented to the parties to the agreement for review. “It is critical that we take stock of this science, identify the causes of these emissions and take necessary action,” he said.