TWN Info Service on Climate Change (Aug24/02)
15 August 2024
Third World Network

Governments approve IPCC’s Short-Lived Climate Forcers Methodology Report outline

Kathmandu, 15 August (Prerna Bomzan) – At the 61^st session of the Intergovernmental Panel on Climate Change (IPCC-61) which met from 27 July to 2 August 2024 in Sofia, Bulgaria, governments successfully approved the outline of the “2027 IPCC Methodology Report on Inventories for Short-lived Climate Forcers” which will be prepared and approved in the second half of 2027.

It will be the first Methodology Report of the current seventh assessment cycle (AR7) and the second AR7 product after the Special Report on Cities, the outline of which was approved as well by IPCC-61 (See TWN Update). The second Methodology Report on Carbon Dioxide Removal Technologies, Carbon Capture Utilisation and Storage (MR CDR/CCUS) is also listed in the AR7 products pipeline.

(The IPCC is the UN body for assessing the science related to climate change. It produces three Working Group Assessment Reports – WG I on ‘The physical science basis’; WG II on ‘Impacts, Adaptation and Vulnerability’; and WG III on ‘Mitigation of climate change’. A Synthesis Report is usually produced synthesising information from the three WG reports and other Special Report/s – assessment on specific issue – produced during an assessment cycle. Methodology Report/s produced by the IPCC provide practical guidelines for the preparation of greenhouse gas inventories.)

Taking the AR6 WGI report as the reference point, Short-lived Climate Forcers (SLCFs) are a set of chemically and physically reactive compounds with atmospheric lifetimes typically shorter than two decades but differing in terms of physiochemical properties and environmental effects. SLCFs can be classified as direct or indirect, with direct SLCFs exerting climate effects through their radiative forcing, and indirect SLCFs being precursors of direct climate forcers.

Direct SLCFs include methane (CH₄), ozone (O₃), short-lived halogenated compounds such as hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), and aerosols. Aerosols consist of sulphate (SO₄^2-), nitrate (NO₃^_), ammonium (NH₄⁺), carbonaceous aerosols such as black carbon and organic aerosols (OA), mineral dust, and sea spray.

Indirect SLCFs include nitrogen oxides (NO_X), carbon monoxide (CO), non-methane volatile organic compounds (NMVOCs), sulphur dioxide (SO₂) and ammonia (NH₃).

From the outset on 27 July, negotiations on the outline of the Methodology Report on Short-Lived Climate Forcers (MR SLCF) proved difficult given sharply divided views particularly on its scope, with regard to whether or not to include the following references in the species list:

(i) Particulate matter 2.5 (PM_2.5) – in relation to black carbon (BC) and organic carbon (OC) in carbonaceous aerosols, selected as direct SLCFs. Primary PM_2.5 was not listed as it is not a species, however it was referenced as a measurement for BC and OC emissions in the instructions to IPCC authors.

(PM_2.5 are particles with a diameter of 2.5 micrometres or less. PM_2.5 is referred to as "primary" if it is directly emitted into the air as solid or liquid particles, and "secondary" if it is formed by chemical reactions of gases in the atmosphere.)

(ii) Hydrogen (H₂) – having indirect effect, and not listed in the AR6 WGI “Table 6.1” from which the SLCFs species were derived and selected on the basis of anthropogenic primary emissions not already covered in the 2006 IPCC Guidelines for National Greenhouse Gas Inventories. However, H₂ was now listed in the proposed outline which was the central contention.

The other divergence was on the title of the MR SLCF, on whether or not it should be a stand-alone report independent from the existing 2006 IPCC Guidelines.

The following is a snapshot of the contested negotiations, prominently in lengthy late hour huddles (informal setting aiming for agreement in principle), which eventually led to a consensus on the key issues in a show of “maximum flexibility” and “balance”, paving the way for the approval of the outline (decision IPCC-LXI-7) on the closing day on 2 August.

Key issues of contention on MR SLCF outline

The key issues were title and status of the report; inclusion/exclusion of PM_2.5 and H₂; reference to interlinkages with air pollution and health.

In the proposed outline (IPCC-LXI/Doc.6) prepared by the Co-Chairs of the Taskforce on National Greenhouse Gas Inventories (TFI,) resulting from the scoping meeting, the proposed title and status of the report and the scope coverage of species were as follows:

·         Proposed Title: “2027 Supplement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories: Short-lived Climate Forcers (2027 Supplement on SLCFs)”

·         Paragraph 4 (Annex 1, Draft Terms of Reference): “Species covered by the new Methodology Report will be NO_X, CO, NMVOCs, SO₂, NH₃, BC and OC (BC and OC can be presented in terms of fraction of PM_2.5; along with the total amount of PM_2.5 emitted), and H_2.”

The language in brackets on PM_2.5 refer to the instructions to authors in paragraph 46, Annex 3: Instructions to Experts and Authors.

The reference to “Interlinkages with air pollution and health” was contained in the introduction section of Volume 1: General Guidance (Annex 2: Table of Contents). (Volume 2: Energy Sector; Volume 3: IPPU Sector [industrial processes and product use]; Volume 4: AFOLU Sector [agriculture, forestry and other land use]; Volume 5: Waste Sectors).

During the contentious talks, the TFI Co-Chairs provided clarifications on these issues highlighting their rationale of using the AR6 WGI Table 6.1 to derive and select the species, showing which are “anthropogenic primary emissions” and are also not covered by the existing “2006 IPCC Guidelines”, citing methane as already covered so is out of the scope of the report. Hence, this was for them another reason to call it a “supplement rather than an independent SLCF report”.

Status and Title of MR SLCF

On the title and status of the report, the TFI Co-Chairs further clarified that the reason to supplement it to the 2006 IPCC Guidelines is to ensure consistency in terms of definitions, scope, categories, and tiers. However, it is up to countries to choose given different national circumstances. It does not replace or refine the 2006 IPCC Guidelines but should be used in conjunction with it. A “Supplement” is a stand-alone IPCC MR e.g. the Wetlands Supplement, and it has no status under the UNFCCC and its Paris Agreement (referring to paragraph 20, decision 18/CMA.1 on the PA Article 13 transparency framework dealing with the methodologies, parameters and data of the national greenhouse gas inventory report). Any IPCC MR will be considered and agreed upon by the Parties – through a decision – before being used for reporting under those agreements.

(Paragraph 20 of decision 18/CMA.1 reads, “Each Party shall use the 2006 IPCC Guidelines, and shall use any subsequent version or refinement of the IPCC guidelines agreed upon by the Conference of the Parties serving as the meeting of the Parties to the Paris Agreement (CMA). Each Party is encouraged to use the 2013 Supplement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories: Wetlands”.)

A representative from the UNFCCC Secretariat was also called to elaborate on the status of the report, who “expected” Parties to the UNFCCC and its PA “will be using for their transparency reports”. However it is up to the Parties to determine to what extent they would like to use since it is not mandatory, and the title is irrespective of its use. She also referred to decision 18/CMA.1 pointing to paragraph 2 which requests the UNFCCC’s Subsidiary Body for Scientific and Technological Advice to undertake the first review of the transparency framework no later than 2028.

As mandated by IPCC Chair Professor Jim Skea (UK), negotiations on the issue were carried out in contact groups led by Ireland and Belize. However towards the end, it required a “huddle” to seek agreement which was led by IPCC Vice Chair Ramon Pichs-Madruga (Cuba) on 30 July.

China said that it is important to take into account the different capacities of developing and developed countries when talking about any methodologies, and that countries should have the right to select options according to their national circumstances, based on a voluntary principle. On the issue of consistency with existing methods, it pointed out that consistency has to start with the difference between Annex 1 and non-Annex 1 countries (categorising developed and developing countries respectively) under the UNFCCC. On consistency in terms of the scientific fact it added that some countries have to reduce emissions by 25% to 40% below 1990 levels by 2020.

Further, the difficulty to ensure consistency between gases and particles/species in terms of reporting measurements and estimations was highlighted. Given the nature of SLCFs is different from GHGs China saw no relation to previous guidelines and stressed on further understanding between gases and other particles or species which is being undertaken as new work under the IPCC. It emphasised that the credibility of the process is solid and concrete evidence as well as information that will be accepted by Parties in their decision-making process domestically and internationally. It therefore called for the report to be neutral, stand-alone, independent of other mandatory reporting under the UNFCCC.

Russia agreed with China on the voluntary principle, that countries should have the option to include the report in their systems or not.

India expressed its concern on the proposed title, that it was not acceptable stating that any linkage to the 2006 IPCC Guidelines creates a whole new set of linkages to obligations and commitments through other channels in other processes and it was therefore not appropriate to put it as a supplement. It called for “option A” contained in the report of the scoping meeting for a “stand-alone independent” report with the title “2027 IPCC Guidelines for National Short-lived Climate Forcers inventories”. India added any consistency with the 2006 Guidelines has to be feasible, scientifically tenable and not mechanically applied, and since this is about breaking new ground with a shift from gases to particles/species, calling the report only “2027 IPCC Guidelines for SCLFs inventories” would be perfectly in keeping with the current scenario.

South Africa also supported previous speakers saying it is too premature to call the report a supplement. Iraq, Algeria and Morocco argued for a stand-alone independent report.

Denmark, Spain, Sweden and the US preferred a supplement as an appropriate title.

The TFI Co-Chairs then proposed a revised title which read “2027 Supplementary Methodology to the IPCC Guidelines for National Greenhouse Gas Inventories: SLCF”. Co-Chair Takeshi Enoki (Japan) explained that reference to “2006” was dropped after hearing it is not so “agreeable”. It will be an independent report but consistent with the principles and approaches of the existing guidelines.

The US expressed flexibility to go with the TFI Co-Chairs’ proposition, which was also supported by Denmark, the UK, Norway, Belgium, Sweden, Germany and Togo. However, India responded stating the term “supplementary methodology” further increases ambiguity and saw no reason for the report to be a supplement to earlier guidelines. Following lack of consensus, Chair Skea then proposed a bridging title as “2027 Methodology Report for SLCFs” which was supported by Saudi Arabia and Algeria, but the Netherlands stressed on a sub-title reading “supplement to 2006 Guidelines”.

TFI Co-Chairs next proposed the title as, “IPCC Methodology Report on Short Lived Climate Forcers: supplement to IPCC national GHG inventory” and also proposed the term “guidance” to replace “guidelines” in response to views heard.

However, the Netherlands insisted that the sub-title should also include “2006 IPCC National GHG Inventory Guidelines”. In response, India reiterated that it was useful to reflect the new ground taken on “species” and proposed a bridging title as, “IPCC Methodology Report on SLCF: Guidance to national GHG inventories”, which was supported by China and Saudi Arabia for the way forward. China further suggested to combine to a single title and proposed it as, “IPCC Supplementary Methodology Report on SLCFs” for a clear and concise message.

But, given no movement on the issue, IPCC Chair Skea (UK) proposed a “huddle” led by IPCC Vice Chair Pichs-Madruga (Cuba) which eventually reached consensus on an independent, stand-alone report with the final title approved as “2027 IPCC Methodology Report on Inventories for Short-Lived Climate Forcers”.

Particulate Matter 2.5 (PM_2.5) and Hydrogen (H₂)

During the negotiations, TFI Co-Chair Enoki (Japan) provided clarifications on these two sticky issues after hearing views from government delegations.

On PM_2.5, it was explained that there was no consensus on its inclusion in the scoping meeting, and since primary PM_2.5 is not a species it is not listed. However, it is to be included as ancillary information, when estimating BC and OC emissions, is derived from primary PM_2.5. It was also explained that the climate impact of aerosols depends on their shape, size, composition and optical properties. Therefore, for PM_2.5 only characterising the size does not inform on climate net effect.

On H₂, it was explained that the issue was not discussed in the expert meetings but came up in the scoping meeting. Experts agreed to include it although it has an indirect impact, but is considered a rapidly raising anthropogenic source and thus to be addressed. The potential importance of H₂ technology in future mitigation efforts was considered. However, it was not listed in the AR6 WGI Table 6.1. The idea is to leave it to authors to consider, given IPCC principles and guidelines provide for an “appendix” where there is potential for future methodological improvement (refer to paragraph 22, Annex 3 contained in the proposed outline).

The two issues were treated as a package, mainly addressed and eventually resolved in contested “huddles” in the final hours, with the process led by IPCC Vice Chair Ladislaus Chang’a (Tanzania).

On PM_2.5, India pointed out that there was no consensus on the inclusion of PM_2.5 yet it was referenced in the outline in the instructions to authors (paragraph 46 of Annex 3) which was contradictory. It asked for the removal of PM_2.5, reasoning that its entire range is not SCLFs – that it has components that provide both positive and negative forcing as well as there is a wide range of other particles in it not connected to radiative forcing. Therefore, the focus should be on BC and OC to be estimated independently.

India further argued that the proposed measuring of fraction of PM_2.5 is scientifically unsound, and it was therefore unacceptable to single out PM_2.5 as the only method to measure BC and OC emissions. It also contextualised the issue with the distinction between air pollution and climate change, the former being at the local level while the latter through global warming. It emphasised that the two are not coterminous as scientifically settled in AR6 WGI and hence, asked for the linkage between air pollution and global warming to be removed from the outline.

Saudi Arabia started with the question of margin of error or level of possible inaccuracy that will result from the SLCFs estimation. It elaborated on the complexities and challenges identified in AR6 WGI that were centred around three key issues:

(i) complex interactions: understanding the intricate interplay between SCLFs and long-lived GHGs remains complex; and the interactions among different aerosol types and their impacts on climate are still not fully understood;

(ii) regional variability: the issue of data scarcity given reliable data on SLCF emissions and concentrations, particularly in developing regions is limited; and the issue of model limitations given climate models struggle to accurately represent regional-scale impacts of SLCFs, especially in complex terrains;

(iii) ⁠uncertainty in climate forcing: on aerosol radiative forcing, quantifying the net radiative forcing of aerosols with precision is challenging due to uncertainties in their properties and interactions; and on indirect effects, assessing it of aerosols on clouds and precipitation remains a significant challenge.

On the issue of PM_2.5 it stated that the TFI Co-chairs themselves have said that it falls outside of the scope of the report and therefore, it would not be agreeing on its inclusion.

China seconded previous speakers, stressing the need to have solid scientific basis, adding that there is no mature studies on PM_2.5 in comparison to other gases.

Russia also questioned the list of species included which does not have GHG qualities citing sulphur dioxide as a case in point and asked for a clear explanation from the TFI Co-Chairs on the importance of including each species.

Iraq, Algeria, South Africa, Azerbaijan, Libya, and Korea also expressed their reservations.

Those who explicitly supported PM_2.5 inclusion were Chile, the US, the UK, Sweden, Denmark, Germany, Switzerland, Norway, Japan, Luxembourg, Belgium, Canada, Spain, Ukraine, St. Kitts, Togo, Mexico and Turkey.

On the issue of H₂ as the key stumbling block that was only resolved on the closing day, the US mainly drove the agenda for its inclusion, fundamentally disagreeing that there is no scientific literature on the issue, highlighting “climatological relevance” to replace “radiative balance”. It said that H₂ has been referenced in AR4, AR5 and AR6 and insisted that any text on species will need to include H_2.

However this was consistently pushed back by developing countries led by China, India, and Saudi Arabia on the basis of not only inadequate, contested scientific literature but also that H₂ was not listed in the AR6 WGI Table 6.1 from where the species were derived and hence out of report’s scope.

In one of the initial huddles, given the persistent push by the US on the inclusion of H₂ as its redline, China questioned whether such a stance also carried any economic interests on the issue to which the US responded that it was in the context of the declaration on hydrogen and derivatives that was agreed in Dubai by some Parties at the UNFCCC’s 28^th Conference of the Parties (COP 28) in 2023, in which it was also involved. The US said that it was interested in seeing the “certification schemes” and “international standards” mentioned in the declaration of intent.

China pointed to the different views around H₂ with no mature studies currently in place and that it was not listed in the AR6 WGI Table 6.1 that is used as the basis for species. It suggested deletion of H₂ from the inventory, stressing that the yardstick in the IPCC scientific platform should be robust and adequate which is fundamental to science-based parameters. There was no sufficient literature yet on H₂ having a global warming potential and given literature on H₂ is emanating with no comprehensive review, the validation of literature is not consensual.

Saudi Arabia emphasised that still there is more research needed to come to established scientific conclusions and that it is important to assess literature from across regions. Given limited and immature literature on the issue it questioned the level of confidence and criteria used to determine the efficacy of the research so far. It pointed out the uncertainties of H₂ in terms of its emissions rate and reiterated that it was also not included in the scope of AR6, and that the issue could be revisited in AR8 when literature is more advanced.

India said that the issue of H₂ is work in progress, whether as a GHG or species, which is a distinctive issue of scientific study. Highlighting the paucity of current literature, it suggested to wait for proper assessment in AR7 WGI and subsequently to consider the matter in AR8. The issue was not the measurability of H₂ but of its impact on radiative forcing. It expressed concerns regarding H₂ as a renewable energy fuel, that this is far-fetched at the moment.

Other countries who largely supported the exclusion of H₂ were South Africa, Iraq, Algeria, Egypt, Libya, Morocco, Azerbaijan, Korea, Russia, Kenya, Venezuela, Congo, Uganda, Comoros, Nigeria, Burundi, Syria, and Zambia.  

On the other hand, those vocally supporting its inclusion were led by the US and supported by the Netherlands, Chile, the UK, Sweden, Ukraine, New Zealand, Denmark, Luxembourg, Germany, Spain, Monaco, Belgium, Switzerland, Japan, Canada, Australia, Norway, Italy, the European Union, Iceland, Turkey, Malaysia, Mexico, Argentina, Brazil, Peru, St. Kitts and Nevis, Antigua and Barbuda, Bahamas and Kiribati.

On 30 July, after extended heated huddles, in a show of flexibility to accommodate the US which clearly signaled its redline, the landing ground on H₂ as well as PM_2.5 as a package was agreed allowing the following lines:

Paragraph 4 of the outline text on the scope coverage of species read, “Taking into account that this work aims to cover 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 [footnote 1] assessed and potentially covered by the new Methodological Report will be NO_x, CO, NMVOCs, SO₂, NH₃, BC, OC, as well as emissions of primary particulate matter relevant for radiative balance, as appropriate”.

Footnote 1 contains three options on H₂ for consideration as follows:

“Option 1: Given the different views, H₂ is within the scope to explore basis for future methodological development of a Tier 1 method for estimating H₂ emissions; although where science is assessed to be robust enough to provide guidance for a Tier 1 methodological approach it will accordingly be included

Option 2: Further SLCFs will be studied in this AR7 by Working Groups for future methodological guidance

Option 3: Given the different views and noting further SLCFs will be studied in AR7 by Working Groups, for this report H₂ is within the scope to explore basis for future methodological development of a Tier 1 method for estimating H₂ emissions. This will be reassessed at the end of AR7. If science is assessed to be robust enough before the literature cutoff date to provide guidance for a Tier 1 methodological approach it will accordingly be included”.

Given the agreement on the reference to PM_2.5 to be dropped altogether, the related paragraph 46 (Annex 3. Instructions to Experts and Authors) was also changed to “For BC/OC emissions, authors should provide guidance, including on techniques of measurement and all variables used to derive emission factors”.

In the huddles that followed on the resolution of the language on H₂, eventually a text proposed by Saudi Arabia as a bridging proposal was picked up as the basis which read, “Given the different views in the Panel on its uncertainties, radiative forcings, and taking note that it has not been well assessed as a climate forcer by IPCC WGI, H2 may be considered to be explored as an appendix as a basis for future methodological development estimating emissions relevant for radiative forcing, while providing special consideration to the different views expressed by the Panel as well as Government reviews and subject to the approval of the panel”.

The US in its interventions had signaled the idea of at least an “appendix” as a potential option on the matter.

On the closing day of 2 August, after the text evolved into multiple options and iterations, agreement was finally reached on the language to be reflected on H_2. This is referenced in the “footnote” to the “species” contained in paragraph 4 (Annex 1, Draft Terms of Reference) of the outline. In the approved outline, the language on the species coverage and H₂ reads:

Paragraph 4: “Taking into account that this work aims to cover 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 [footnote 2] 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.

Footnote 2: “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”.

Interlinkages with Air Pollution and Health

Following from the consensus reached on PM_2.5 the reference to “Interlinkages with Air Pollution and Health” contained in the table of contents, it was eventually deleted from the outline, which Chair Skea (UK) said was “out of scope”.