2027 IPCC Methodology Report on Inventories for Short-lived Climate Forcers

The Panel agreed to the outline  of the 2027 IPCC Methodology Report on Inventories for Short-lived Climate Forcers at its 61st Session held in in Sofia, Bulgaria from 27 July to 2 August 2024 (Decision IPCC-LXI-7).

The Methodology Report will provide guidance on Short-lived Climate Forcer emissions which are anthropogenic, not including secondary human-induced substances, national, annual and will be reported in mass units for each individual emitted species.

The report aims to cover:

1. All IPCC inventory sectors with categories where the science is assessed to be robust enough to provide guidance for a Tier 1 methodological approach and have a relative contribution to the global/regional emissions of the species, species assessed and potentially covered by the new Methodology Report will be NO_X, CO, NMVOCs, SO₂, NH₃, BC and OC, as well as emissions of primary particulate matter relevant for radiative forcing, as appropriate.
2. Methane and halogenated species under Montreal Protocol and Kigali Amendment will not be covered since these are already addressed by the existing IPCC Guidelines.
3. Given the uncertainties in the radiative forcing of H₂ and taking note that H₂ has not yet been well assessed as a climate forcer by IPCC WGI, H₂ emissions relevant for radiative forcing are to be considered by the authors as an Appendix subtitled “Basis for future methodological development” subject to the IPCC’s Principles and Procedures on review and adoption.
4. For NMVOCs, the methodology should provide estimates for total NMVOCs. The speciation of NMVOCs should be considered by authors, as appropriate.
5. Anthropogenic emissions only, where anthropogenic refers to emissions from human activities and from managed land.
6. Sources covered are those of anthropogenic emissions, where scientific evidence is available; while for others, guidance could be provided as a basis for future methodological development.
7. Geographical and temporal coverage is national and annual level, and authors should also consider guidance on spatial and temporal disaggregation of SLCF emissions.

The First Lead Author Meeting for the 2027 IPCC Methodology Report on Inventories for Short-lived Climate Forcers was held on 24-26 March 2025 in Bilbao, Spain. The Second Lead Authors Meeting was held in Istanbul, Türkiye, from 7-9 October 2025. The Third Lead Authors’ meeting will be held in Rome, Italy, April 2026.

Over 150 experts are participating in the writing process, which will be completed by 2027.

The participants were selected by the Task Force Bureau taking into account scientific and technical expertise, geographical and gender balance to the extent possible in line with Appendix A to the Principles Governing IPCC Work.

Scientific Steering Committee Members

The Scientific Steering Committee governing the writing process is chaired by IPCC TFI Co-Chairs, Takeshi Enoki and Mazhar Hayat, and also includes:

• Maria José Sánz (TFI Task Force Bureau)
• Laura Dawidowski (TFI Task Force Bureau)
• Mohd Talib Bin Latif (TFI Task Force Bureau)
• Maheswar Rupakheti (Vice-Chair of WGI)
• Veronika Ginzburg
• Steve Smith
• Ole-Kenneth Nielsen
• Ajay Kumar Singh
• Daniela Romano
• Melisa Carla Diaz Resquin
• Marta Andrea Del Carmen Alfaro Valenzuela
• Doug Macdonald
• Jongikhaya Witi
• Mark Hunstone