Banks, emissions, and environmental impacts of China's ozone depletion substances and hydrofluorocarbon substitutes during 1980-2020.

Ozone-depleting substances (ODSs), which also contribute to global warming, have been controlled by the Montreal Protocol (MP) since 1987. China joined the MP in 1991 and began reducing production and consumption of ODSs in the country, leading to a decrease in emissions of ODSs. Based on the Intergovernmental Panel on Climate Change guidelines, the latest emission factors and actual consumption in China (MP scenario), both the historical banks and the historical emissions of ODSs and substitute hydrofluorocarbons (HFCs) during 1980-2020 were calculated. To understand the reduction in ODS and HFC emissions by implementing the MP, we also estimated China's virtual emissions (NMP, i.e., the amount of ODS emissions without the MP) over the same period. The avoided cumulative ODS consumption and emission values of 10.8 and 5.8 (4.8-6.9) million tonnes (Mt) of CFC-11-equivalent (eq), respectively, were estimated by comparing the two scenarios. Furthermore, 26 (22-33) giga tonnes (Gt) of CO2-eq emissions, equivalent to an increase of 0.031 W m-2 radiative forcing, were estimated to be avoided by 2020, which will prevent an additional 0.025 °C increase in temperature. The MP implemented by China has resulted in substantial environmental benefits over the last 30 years. However, owing to the massive use of HFCs as substitutes, the cumulative emissions reached 2286 Mt. CO2-eq during 1990-2020, and it will be challenging to phase down HFCs in the environment after China ratified the Kigali Amendment in 2021.