Despite being banned under the Montreal Protocol, the five chlorofluorocarbons (CFCs) measured increased rapidly in the atmosphere from 2010 to 2020, reaching record-high levels in 2020, according to the study published in the journal Nature Geoscience. "If you are producing greenhouse gases and ozone-depleting substances during the production of these next-generation compounds, then they do have an indirect impact on the climate and the ozone layer," said co-author Isaac Vimont of the Global Monitoring Laboratory at the US National Oceanic and Atmospheric Administration. Nationwide data gaps make it difficult to determine where the gases are coming from and for some of the CFCs analysed there are no known uses