Emissions of HFC-134a in China and Reconciliation of Discrepancies between Observation-Based and Inventory-Based Emission Estimates

HFC-134a (1,1,1,2-tetrafluoroethane) is a potent greenhouse gas with global warming potential thousands of times larger than that of carbon dioxide (CO₂). HFC-134a is regulated under the Montreal Protocol. However, the emissions, consumption, and emission-consumption relationships of HFC-134a are unclear. Here, this study reveals that observation-based HFC-134a emissions increased from 19.5 ± 2.5 Gg yr^-1 in 2011 to 33.1 ± 7.5 Gg yr^-1 in 2020 in China, but with a lower increase (2%) compared to those (48%) reported in a previous inventory-based emission estimate from 2015 to 2020. Consequently, the emission discrepancy between observation-based and inventory-based emissions reached 24.9 ± 7.5 Gg yr^-1 (equivalent to 36.6 ± 11.0 Tg of CO₂-eq yr^-1) in 2020. Therefore, this study built a novel approach (Observation-based Sectoral Activity and Emission Function Attribution Model, OSAM) to quantitatively attribute these emission discrepancies. We found that the emission discrepancies of HFC-134a were generally attributed to the consumption (35.6%) and emission functions (64.4%) used in previous emission inventories; thereby an emission inventory with new emission-consumption relationships, which matched the observation-based estimates, was established in this study. This study provides an emission discrepancy reconciliation approach applicable worldwide.