Methodological work on Short-lived
Climate Forcers
Bonn Climate Change Conference (SB50)
IPCC TFI Side Event
19 June 2019, Bonn, Germany
Yurii Pyrozhenko
IPCC TFI TSUOutline
Expert meeting on SLCF held in May2018• Background• Coverage of SLCF species• Outcomes• Conclusions and recommendations
Future work on SLCF inventories
decided by IPCC-49 in May 2019
• Related to AR6 cycle• Related to AR7 cycle

Expert meeting on SLCF held in May
2018

Background Science on SLCFs has significantly advanced since the IPCC
Expert Meeting on Emission Estimation of Aerosols Relevant to
Climate Change was held in 2005
 At the 45th Session in Guadalajara (March 2017), some member
governments proposed on work of IPCC, among others: development of robust inventory methodologies on estimationof SLCF emissions
 At the 46th Session in Montreal (September 2017), IPCC
decided to hold an expert meeting on Short-lived Climate
Forcers to discuss issues on estimation of emissions andclimate effects (Decision IPCC/XLVI-6)
 The meeting, organised jointly by TFI and WGI, took place on
28-31 May 2018 in Geneva, Switzerland

Coverage of SLCF species (1) Aerosols: Black Carbon (BC) Organic Carbon (OC) PM2.5
 Precursors:
 NOx
 CO
 NMVOC (including BVOC)
 SO₂
 NH₃
 CH₄ and HFCs are already covered in 2006 IPCC Guidelines and its 2019
Refinement, therefore these SLCFs were not consideredCoverage of SLCF species (2)Most of SLCF species considered are included in existing nonIPCC guidance (e.g. EMEP/EEA and AP-42)
The only exception is OC that generally is not accounted for due
to methodology and data gaps
In addition, the current approach to derive BC emissions as afraction of PM2.5 or PM10 (e.g., in EMEP/EEA Guidebook) mightneed elaboration due to significant variability in observed
BC/PM2.5 ratios
 Existing guidance does not cover all global sources and is not
yet globally-applicableOutcomes
Meeting Report was published on TFI website:
https://www.ipcc-nggip.iges.or.jp/public/mtdocs/1805_Geneva.html)

The outcomes of the meeting: will be used as a basis for future work of TFI are expected to feed into the WGI AR6 report, primarily in
Chapter 6 (Short-lived climate forcers) but also Chapter 7(The Earth’s energy budget, climate feedbacks, andclimate sensitivity)

Conclusions and recommendations (1)Science has advanced. Need has arisen.
 Since AR5, progress has been made in:

improved definitions of OC and BC
increased understanding of non-combustion aerosol sources
amount of measurements on aerosol particle sizes
better model parametrisations of aerosol processes

 Improved SLCF emission inventories and methodologies
are necessary:

to increase accuracy of SLCF emission estimates
to enhance scientific understanding and assessment of theirrole in climate change; as well as
to inform climate policy at the national and international levels,
particularly through UNFCCC

Conclusions and recommendations (2)IPCC can play an important role.
 Internationally-agreed, globally applicable methodologies
and emission factors for SLCF emission inventories arenecessary The IPCC can play an important role because of its
unique position, therefore considered to be the rightorganisation to fill gaps in existing methodologies and todevelop and disseminate an internationally-agreed,
globally applicable methodological guidance based on
existing methodologies
 This could be achieved in close cooperation andcollaboration with other relevant international bodies

Conclusions and recommendations (3)All SLCFs should be considered.
 Some SLCF species are of key importance globally
and/or regionally for climate change (e.g. CH4, NOx, OC,
BC and SO2)
 Others may become a high-priority over time in terms ofmitigation strategies (e.g. NH3 and VOC)
 In order to take into account trends and developments, allSLCFs should be considered with more focus on speciesand sources that are not well covered in existing guidanceConclusions and recommendations (4)Careful consideration is required in consolidating
existing inventory methodology.

 If the IPCC Plenary decides to engage into further work
on SLCF inventories, careful consideration needs to begiven to possible issues in consolidating existing
inventory methodologies on GHGs and SLCFs
 Generally, much of the existing good practice guidanceon GHG inventory is applicable to, or can be a goodbasis for, SLCF inventories at a national level
 For some emission sources, however, existing
inventory methodology does not provide a good basis
for SLCF inventory

Conclusions and recommendations (5)SLCF reporting should be in mass units, not in CO2-eq.
 Reporting of SLCF inventories should be in mass units foreach individual emitted compound SLCF emissions should not be converted to CO2
equivalent units in the same way as done based on
GWP100 in the inventory reporting under the UNFCCC
 The understanding of emission metrics and how they canbe used, particularly for SLCF, has advanced but there iscurrently no agreed recommendation Issue of metrics and how they can be used may be further
considered based on new scientific literature forcoordination across WG reports (particularly WGI & WGIII)

Future work on SLCF inventories
decided by IPCC-49 in May 2019

Decision taken at IPCC-49 in May 2019 (1) Taking into account the conclusions andrecommendations from the Expert Meeting in May
2018, the IPCC at its 49th Session in May 2019decided (Decision IPCC-XLIX-7) that:
 IPCC TFI produces an IPCC Methodology Report on
SLCFs following the Appendix A to the PrinciplesGoverning IPCC work The preparatory work for the Methodology Report:
 Completed as soon as possible, starting in the AR6cycle
 Followed by further methodological development in theAR7 cycle

Decision taken at IPCC-49 in May 2019 (2)During AR6 cycle

 Expert meetings will produce a series of supporting
materials to be published after each meeting but nolater than 2022
 These supporting materials will be used to informthe scoping of methodological work for SLCFs
 The scoping meeting will take into consideration thework on SLCF underway in the reports of Working
Group I (April 2021) and III (July 2021)
 The outline will be presented for approval to the
Panel soon after the scoping meetingThank you
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