Measured and expected atmospheric concentrations of CFC-11

Measured concentrations of trichlorofluoromethane (CFC-11) gas in the Northern and Southern hemispheres, measured relative to the expected/projected
concentrations based on emissions reported by countries to the Montreal Protocol. This is measured in mole fractions (ppt) of CFC-11. In recent years (since 2012),
concentrations have not declined at the projected rate, suggesting unreported sources of CFC-11 emissions.