IPCC TFI Work on Short-lived Climate Forcers:
Background and Scope
Third IPCC Expert Meeting on Short-lived Climate Forcers
11-15 April 2022
Virtual Meeting
IPCC TFI TSUExpert meeting in 2018
• At the 45th Session of the IPCC (March 2017, in Guadalajara, Mexico) somegovernments proposed the work on development of methodologies forestimation of emissions of Short-lived Climate Forcers (SLCFs)• At its 46th Session (September 2017, in Montreal, Canada) the IPCC decided(Decision IPCC/XLVI-6) to hold an expert meeting on SLCFs to discuss issues
on estimation of emissions and climate effects• The expert meeting was held jointly by TFI and WGI on 28-31 May 2018 inGeneva, Switzerland• The following SLCF species were considered at the meeting: BC, OC, [PM2.5],
NOx, CO, NMVOC (including BVOC), SO2 and NH3. Methane and halogenatedspecies (e.g., hydrofluorocarbons) are not discussed at the meeting as they are
already well covered by the 2006 IPCC Guidelines for National Greenhouse
Gas Inventories and its 2019 Refinement

Expert meeting in 2018

• The meeting concluded, among others:

Improved emission inventories of SLCFs are necessary to enhance scientificunderstanding and assessment of their role in climate change as well as to informclimate policy at national and international levels― Internationally-agreed, globally applicable methodologies and emission factors for
SLCF emission inventories are necessary, and the IPCC TFI is in a good position
to do that work
― All SLCF species discussed at this expert meeting are considered important andshould be prioritized in the future work to develop inventory methodology― SLCF emissions should not be converted to CO2 equivalent units in the same way
as in the inventory reporting under the UNFCCC. The meeting agreed that theissue of metrics and how they can be used may be further considered based on
new scientific literature for coordination across WG reports (particularly WGI &WGIII)―• The meeting report is published at the TFI website https://www.ipccnggip.iges.or.jp/public/mtdocs/1805_Geneva.html

Further work on SLCFs• Taking the conclusions and recommendations of the expert meeting held in 2018
into consideration, the IPCC decided (Decision IPCC-XLIX-7) at its 49th Session(May 2019, in Kyoto, Japan) to develop a Methodology Report on SLCFs during
the IPCC 7th Assessment Report (AR7) cycle• The preparatory work for the Methodology Report to be completed as soon aspossible, starting in the AR6 cycle――――

Technical analysis work by TFI TSU with other experts
3-4 Expert meetings
Scoping meeting
Approval of outline by the Panel• Expert meetings will produce a series of supporting materials after each expert
meeting and will be used to inform the scoping of methodological work forSLCFs

Work on SLCFs in 2020-2022• TFI Technical Support Unit (TSU) conducted technical analysis of the main
methodological frameworks on SLCF emissions (EMEP/EEA Air Pollutant Emission
Inventory Guidebook 2019; AP-42: Compilation of Air Pollutant Emissions Factors, USEPA; and Atmosphericand prepared a number ofbackground documents to support the work at expert meetings• Kick-off Session for the IPCC TFI Expert Meetings on SLCFs was held on 9and 11 March 2021 (virtual meeting)• Joint 1st and 2nd IPCC Expert Meeting on SLCFs was held on 11-22 October
2021 (virtual meeting)• 3rd IPCC Expert Meeting on SLCFs on 11-15 April 2022 (virtual meeting)
Brown Clouds (ABC) Emission Inventory Manual, UNEP)

Impact of COVID19 pandemic on the work plan
• No meetings in 2020
• IPCC at its 53(bis) Session (March 2021) agreed that Scoping meeting plannedin 2022 should be postponed to AR7 cycle together with the IPCC Session foroutline approvalOutcome of the Joint 1st and 2nd IPCC Expert Meeting on
SLCFs (Joint Meeting)••Working on the background documents, the Joint Meeting successfully achieved itsgoals:
1.

Complete list of SLCF source categories and associated SLCF species for all
sectors – Energy, IPPU, AFOLU and Waste (the main goal)

2.

List of knowledge gaps (the secondary goal)

All outcomes (category list, gaps’ list, BOGs’ discussion and conclusions, presentations andtables for each sector) are part of the meeting report published in the TFI website(https://www.ipcc-nggip.iges.or.jp/public/mtdocs/2110_SLCF.html)•The category list and other materials will help to inform the future Scoping meetingwith the aim to develop the outline of a new Methodology report on SLCFs

The 3rd IPCC Expert Meeting on SLCFs• The scope of the 3rd Expert Meeting is to consider: SLCF species definitions and their relevance for a climate-related inventory(BOG1)
 Applicability of general inventory guidance provided in Volume 1 of the 2006
IPCC Guidelines and the 2019 Refinement to the inventories of SLCFs,including, but not limited to, key category analysis, uncertainty analysis,verification, etc. (BOG2)
 Gaps that need to be addressed in the future work for a new Methodology
Report on SLCFs (BOG3)

Materials for the 3rd Expert Meeting
BOG1

BOG2
BOG3

Note on BOG1 including participants’ feedback to the questionnaire
Outcomes of the IPCC WGI and WGIII contributions to AR6
Note on BOG2 including participants’ feedback to the questionnaire
Note on Key Category analysis
Technical consolidation of Volume 1 of the 2006 IPCC Guidelines and Volume 1 of the2019 Refinement (informal material prepared by TSU)
Note on BOG3 including participants’ feedback to the questionnaire
Gaps list from the Joint Meeting and Geneva Meeting
Category list from the Joint Meeting
Allocation issues from the Joint Meeting

QuestionnaireExperts’ feedback

Definitions ofSLCFs

General Inventory
IssuesLists of Gaps andCategories

1096

Expected discussion and outcomeof the 3rd Expert Meeting – BOG1
2018 Geneva Expert Meeting concluded that SLCF species to focus on in a national emission
inventory are:• Aerosols:- Black Carbon (BC, also as fraction of PM2.5)- Organic Carbon (OC, also as fraction of PM2.5)• Precursors (ozone precursors and aerosol precursors):
- NOx
- CO
- NMVOC (including BVOC)
- SO2
- NH3
BOG1 experts are expected to discuss the following:
1.

With reference to the above list of SLCF species, could experts confirm its validity?

Expected discussion and outcomeof the 3rd Expert Meeting – BOG1
2. Is there a common metric applicable across all GHGs and SLCFs to assess the relative
importance in terms of climate impacts of each GHG/SLCF source and CO2 sinks within
national emissions totals?
3. For each SLCF species provide a prioritization in an emission inventory considering therelevance in terms of climate impact?
4. Could experts assess if for any of the SLCF species listed above constrains ininstruments/monitoring-systems availability and operativity may prevent countries’ capacity toprepare national emission estimate unless a disproportionate amount of resources is to beapplied?

Expected discussion and outcomeof the 3rd Expert Meeting – BOG2
BOG2 experts are expected to discuss the following:•Key category analysis- How quantitative approaches should be applied for SLCFs (see KCA note)?
- Should qualitative criteria for SLCFS be applied as provided for GHGs in the KCA note orshould be revised or new to be added?

•Approaches to data collection and time series consistency- How to address finer temporal and spatial distribution of SLCFs?
- What are the implications in terms of good practice for SLCFs data collection?
- What are implications on time series consistency for SLCFs?

•Verification.
- Given SLCF emissions have large spatial and temporal variability, should verification withatmospheric observation data be further promoted?
- Is there any regional/global independent monitoring system/dataset to be suggested forverification of SLCF emissions?

Expected discussion and outcomeof the 3rd Expert Meeting – BOG3
BOG3 experts are expected to:1.

Refine the list of data gaps and, where needed, to refine the list of SLCF categories
as well2.

Prioritize the gaps for future research according to the significance of the sources,
for which methods gaps and/or data gaps are identified

3.

Review the list of allocation issues (cross-sectoral/cross-category), where a further
work or clarification is needed and to refine the list, if neededThank you
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