The Kigali Amendment to the Montreal Protocol introduced controls to reduce HFC-23 emissions. China and India, major HCFC-22 producers, implemented ambitious reduction programs. However, atmospheric observations reveal increased emissions in 2018, exceeding historical levels. This discrepancy suggests that reported reductions haven't fully materialized or that HCFC-22 production is substantially unreported, leading to unaccounted-for HFC-23 emissions. The difference between reported and observed emissions implies an additional ~309 Tg CO2-equivalent added to the atmosphere between 2015 and 2017.

K.M. Stanley, D. Say, J. Mühle, C.M. Harth, P.B. Krummel, D. Young, S.J. O'Doherty, P.K. Salameh, P.G. Simmonds, R.F. Weiss, R.G. Prinn, P.J. Fraser, M. Rigby