Background and outcome of the Expert
Meeting on SLCF in May 2018 and possible
future work on SLCF inventories
UNFCCC COP24 IPCC TFI side event
Katowice, Poland
13 December 2018
Kiyoto Tanabe, Co-Chair of IPCC TFIOutline• Background• Expert Meeting on SLCF
• Conclusions and recommendations• Possible future work on SLCF inventories

BackgroundBackground (1): Expert Meeting in 2005
 Recognizing the potentially significant
influence of aerosols on climate change
as identified in the IPCC Third
Assessment Report (TAR)
published in 2001, an IPCC Expert
Meeting on Emission Estimation ofAerosols Relevant to Climate
Change was held in May 2005.
Primary focus was on carbonaceous aerosols
such as black carbon.

Background (2): Expert Meeting in 2005
The expert meeting in 2005 concluded, among others:• Global inventories of emissions of aerosols relevant to climatechange contained significant sources of uncertainty.
• It was not yet possible to reliably produce internationallycomparable national emission estimates and estimate realdifferences in emission characteristics between countries.
• Work was needed to reduce some of the uncertainties.
• Further similar meetings participated by WGI, TFI and other aerosol
inventory experts should be held.
However, no follow-up expert meeting was held.

Background (3): IPCC Assessment Reports
Understanding of aerosol radiative
forcing advanced through AR4(2007) and AR5 (2013).
However, AR5 still concluded thataerosols contributed the largest
uncertainty to the total radiative
forcing estimate.
AR6 production has started. WGI Contribution
will be produced for approval/acceptance by theIPCC Plenary in 2021.
• Chapter 6 “Short-lived Climate Forcers”

Background (4): Emerging Issue - SLCF
Recently, the potential importance of reducing
emissions of short-lived climate forcers (SLCF)
such as methane, black carbon, and precursors oftropospheric ozone is recognized more and more.
to mitigate climate change;
to improve air quality; and therefore
to bring near-term co-benefits in terms of humanhealth, agricultural yields and ecosystems.

Expert Meeting on SLCF

Expert Meeting on SLCF
At the 45th Session in Guadalajara (March 2017), somemember governments proposed on work of IPCC,
among others:• development of robust inventory methodologies onestimation of 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 ofemissions and climate effects. (Decision IPCC/XLVI-6)
The meeting, organised jointly by TFI and WGI, took
place on 28-31 May 2018 in Geneva, Switzerland.

Objectives of Expert Meeting To review existing methodological work to estimate emissions ofSLCF with a view to considering suitability for the IPCC todevelop methodological guidance; To consider which species of SLCF should be prioritized in thepossible future work to develop inventory methodology, taking
account of uncertainties in emission estimates and possible
applicable common metrics as well as the extent to which it willcontribute to inform decision making in mitigation policies andmeasures;
 To consider how the inventory methodology on SLCF wouldrelate to the existing inventory methodology on greenhousegases;

Objectives of Expert Meeting To identify gaps in scientific understanding on estimates ofSLCF emissions that need to be filled in by scientific researchcommunity; To review existing methodological work to quantify the global
radiative direct and indirect effects of SLCF, with a focus on newdevelopments since the AR5;
 To identify gaps in scientific understanding on estimates of
direct and indirect climate effects of SLCF on radiative forcing
and climate response, including implications on clouds, thatneed to be filled in by scientific research community.

Substances discussed
 It should be noted that inventory methodologies on methane and
HFC are already well covered by the 2006 IPCC Guidelines forNational Greenhouse Gas Inventories produced by TFI as wellas the on-going work by TFI to refine the 2006 IPCC Guidelines.
 Therefore, the substances of interest at this meeting are:
• Black Carbon• Organic Carbon• PM2.5• NOx• CO• NMVOC (including BVOC)
• SO2
• NH3

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 consideration of future work ofTFI; and• are also 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, and climate sensitivity),

Conclusions and recommendations

Conclusions and recommendations (1)Science has advanced. Need has arisen.
 There has been substantial improvement in scientificunderstanding of emissions and climate effects of SLCFs
since the last Expert Meeting in 2005, and continued
improvements since the AR5 (2013).
 Improved SLCF emission inventories and methodologies
are necessary: 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 United Nations Framework Convention on
Climate Change (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, all
SLCFs should be considered with more focus on species
and sources that are not well covered in existingguidance.

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 SLCFinventory.

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).

Possible future work
on SLCF inventories

Future work plan proposed at IPCC-48
A future work plan was proposed at IPCC-48 (Oct 2018, Incheon, Republic of Korea).

(1) Late 2019 – A paper will be prepared by asmall task team about the alignment of the 2006
IPCC Guidelines and the EMEP/EEA Guidebook.

(2) Early 2020 - An expert meeting will be heldby TFI, possibly jointly with UNECE/TFEIP.

(3) Outcomes of the steps (1) and (2) will bereported to the Panel as IPCC supporting
materials.
They will help
countries start
producing
SLCF
inventories.

(4) A further work plan will be developed after
consideration of the outcomes of the steps (1)and (2) above.

Future work plan proposed at IPCC-48
 At the step (4), the future work plan should take into
account discussion by the Panel at a future session ofIPCC as well as the views of the UNFCCC.
•••

One possible approach may be to organize a series of expert
meetings focusing specific sources/SLCF species to come up
with detailed methodological advice.
Another possible action is to organize a joint TFI/WGI expert
meeting on SLCF again in late 2021, building on the WGIcontribution to the AR6 which will be approved/accepted in April
2021 as well as the outcomes of TFI expert meetings.
Production of a new Methodology Report which deals with SLCF
inventory, if necessary, may be done in the AR7 cycle, buildingon the outcome of these steps.

Decision to be taken at IPCC-49 In response to this proposal, several delegatesmade interventions - different views were heard:• Prefer an earlier start of the work on SLCF inventory
guidelines so that a new Methodology Report can be
developed in this AR6 cycle.
• Support TFI proposal to produce a new Methodology
Report during AR7 cycle because it is important to build
it on the new findings of WGI’s Contribution to AR6
report, and also because of the already tight schedule.

 IPCC will discuss and take a decision on the TFI’s
future work plan on SLCF inventory methodology atits 49th Session in May 2019 in Kyoto, Japan.

Thank you
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