Fig. 1: HFC-23 emissions, HCFC-22 production and HFC-23 mole fractions, 2008–2023.

a Bottom-up and top-down HFC-23 emissions for the period 2008–2023. The green line shows the global emissions derived in this study from measurements of atmospheric mole fractions from the Advanced Global Atmospheric Gases Experiment (AGAGE). The pink line shows the emissions estimated from eastern China for this period, also derived in this study using data from Gosan, South Korea and the FLEXINVERT+ inversion framework. The green and pink shading represents the 1-sigma uncertainty in these estimates. The bottom-up estimates of global HFC-23 emissions through 2020 are shown by the dashed green line, based on emissions of HFC-23 reported to the United Nations Framework Convention on Climate Change (UNFCCC) and, for non-Annex 1 countries, HCFC-22 production data with abatement reported to the Multilateral Fund. These data suggest a substantial drop in emissions as China and India’s abatement policies were implemented from 2015-2018. The green dotted line indicates emissions of HFC-23 from HCFC-22 production reported to the United Nations Environment Programme (UNEP) under the Kigali Amendment, combined with reports by Annex I countries to the UNFCCC for years where both are available; note that China only began reporting emissions to UNEP in 2020. The pink dashed line shows the bottom-up inventory of HFC-23 emissions for China taken from ref. ²⁷. The blue shaded area indicates the period during which China’s hydrofluorocarbon production phase-out management plan was in operation. b Global HCFC-22 production data for 2008-2022 for both feedstock (maroon) and non-feedstock (blue) uses, as reported to UNEP⁵³. c Hemispheric monthly baseline mean HFC-23 mole fractions for 2008–2023, based on in situ measurements from the five core AGAGE sites, for the northern (blue) and southern (orange) hemispheres.