text: Starting in the 2010s, despite a global ban on the production of CFCs, five of these ozone-damaging emissions were on the rise.
  The atmospheric abundance of CFC-13 rose from 3.0 parts per trillion (ppt) in year 2010 to 3.3 ppt in year 2020 based on analysis of air samples gathered from sites around the world.
  Contrary to the Montreal Protocol, the atmospheric emissions of CFC-13 and four other chlorofluorocarbons (CFCs), increased between 2010 and 2020. 
  As of 2023, the drivers behind the increase in CFC-13 and CFC-112a emissions were not certain.