"Scientists who detected the return of a long-banned pollutant say emissions resumed their prior decline after China cracked down on production of the chemical."
"The whodunit began when scientists caught a whiff of an unexpected climate super-pollutant in the air in 2018, which spurred a global investigation to find its source. A subsequent crackdown on illegal production of the banned chemical has resulted in a return to decreasing emissions of the powerful greenhouse gas, two new studies conclude, effectively closing the case.
Production of CFC-11, which was used primarily to make foam insulation, was slowly phased out before being banned entirely by 2010. The chemical, which destroys atmospheric ozone in addition to warming the planet, was banned under the Montreal Protocol, an international agreement that was finalized in 1987 to help mend the “ozone hole” over Antarctica and now also addresses climate change.
However, in 2018, researchers detected an “unexpected and persistent increase” in global atmospheric concentrations of CFC-11, which is 7,000 times more effective at warming the planet than carbon dioxide over the near term."