Although developing countries have compiled greenhouse gas inventories (GHGI) for over 20 years, improving national GHGI capacity remains a priority under the Paris Agreement. However, a global assessment of GHGI capacity status and change over time has not yet been conducted. By developing a quantifiable GHGI capacity and quality indices based on a synthesis review of 369 submitted GHGIs, our assessment shows that while roughly half of 133 developing countries have
improved their GHGI capacity and quality from 1997 to 2019, the remaining countries have not. This is especially evident regarding the GHGI quality principles of promptness, accuracy, and consistency. Future capacity-building approaches
should make it clear how GHGIs can support countries pursuing their domestic climate goals, including climate resiliency and low greenhouse gas (GHG) emissions development pathways, while exploring the use of other information sources to replace GHGIs where they are missing. Global assessments of capacity building can largely be improved with increased data availability, which can be addressed collectively under the Paris Agreement.