Reporting of Black Carbon emissions: A comparison of data submitted under the Air Convention and alternative datasets

Black carbon (BC) is a key short-lived climate forcer and an air pollutant with significant impacts on human health. Although reporting of BC emissions remains voluntary under the Convention on Long-range Transboundary Air Pollution, 42 Parties submitted BC data in 2024. This report assesses the completeness, methodological consistency and comparability of reported BC emissions and compares national inventories compiled by CEIP with alternative datasets from GAINS and CAMS.

Residential stationary combustion (1A4bi) is the dominant source of BC emissions that contributed on average 43.75% of total BC emissions in the year 2022. Most countries used a Tier 2 methodology for reporting in sector 1A4bi - Residential Stationary. In contrast, emissions from venting and flaring, agricultural residue burning and waste-related activities often rely on basic Tier 1 methodologies or remain unreported altogether.

Comparisons between CEIP, GAINS and CAMS BC emission estimates, three datasets that are compiled by different institutions, that use different approaches but that are not completely independent from each other show that the strongest overall alignment is observed between GAINS and CAMS, while the comparison between CEIP and CAMS shows lower, yet still significant, correlation.

A few countries exhibit very low correlations between the datasets. In these cases, the low or even negative correlations likely reflect fundamental differences in sectoral allocation, activity data selection, or emission factor choice rather than random deviations. Such anomalies highlight the need for targeted review efforts during the annual inventory review process. Future studies could delve deeper into the reasons behind low correlations in certain sectors or countries, potentially identifying areas where data collection methodologies or emission models could be refined.