The Intergovernmental Panel on Climate Change reaches landmark decision on short-lived climate forcers.

At its 49th session in Kyoto, Japan, the Intergovernmental Panel on Climate Change (IPCC) decided to develop methodologies that will enable countries to establish emission inventories for short-lived climate forcers (SLCFs) like black carbon and other air pollutants.

The decision enables the development of comprehensive and integrated air pollution and greenhouse gas reduction strategies at global to local levels, and across sectors. Countries will be able to use the methodology to account for SLCFs emission reductions which complement carbon dioxide mitigation, and to report on short-lived climate forcers in their National Communications and Nationally Determined Contributions (NDCs).

Norway’s Minister for Climate and Environment, Ola Elvestuen, welcomed the decision saying: "This is an important milestone in the global effort to reduce emissions of short-lived climate forcers."

Helena Molin Valdes, Head of the UN Environment hosted Climate and Clean Air Coalition said: “The new methodology should help maximise the co-benefits from efforts to reduce all climate and air pollutants. It will enable different types of emissions to be compared and modelled and removes an important layer of uncertainty when developing mitigation policies.”

Currently there is a lack of globally relevant methodology for quantifying emissions of non-greenhouse gases. Many countries see the current guidance developed by the United Nations Economic Commission for Europe (UNECE) to be euro-centric. The decision will help countries in the Climate and Clean Air Coalition’s Supporting National Action Planning (SNAP) initiative, account for emissions of black carbon and air pollutants with their greenhouse gas emission inventory and include them in their required Biennial Update Reports and National Communications to the United Nations Framework Convention for Climate Change (UNFCCC).  

Another benefit that a global methodology brings is the ability for countries to use current capacity and resources within their official greenhouse gas inventory systems to include short-lived climate and air pollutants in their emission inventory efforts.

In many countries air pollution and climate change are dealt with by different ministries. For example, short-lived climate pollutants, like black carbon, are the responsibility of air quality divisions within ministries of environment, while climate change divisions focus on greenhouse gas emissions. Having short-lived climate forcer and greenhouse gas guidance will help consolidate emissions reduction efforts by increasing cooperation and officially integrating black carbon and air pollutant emissions into climate inventories. Air pollution co-benefits from climate action (and vice versa) can help drive ambitious climate and air quality policies.   

The implication of the IPCC decision is that it potentially removes the barriers to integrating black carbon and other short-lived climate forcers into the emission inventory and reporting systems created for greenhouse gases. In most countries the greenhouse gas inventory system is better developed and more sustainable than any air pollution emission inventory process (if it exists at all). Therefore, putting emissions of short-lived climate forcers under the IPCC emission inventory framework, and providing a globally relevant methodology for quantifying emissions should allow for a much more robust assessment of both climate change and air pollution.  

The Coalition’s SNAP initiative has shown that to effectively abate short-lived climate pollutants and to integrate air pollution and climate change mitigation, it is important to quantify emissions consistently. Further, it is important to express the relevance of implementing a particular mitigation measure in terms of impacts both on climate, health and crops.  Emissions of all relevant greenhouse gases, short-lived climate pollutants and air pollutants need to be considered. The IPCC decision should make it easier for countries to meet this requirement, and to undertake such an assessment.

The process leading to this landmark result was driven by several CCAC partners, with the support of the Coalition’s Scientific Advisory Panel. At the 46th session of the IPCC, in September 2017, the Parties approved a proposal submitted by Mexico, Chile and Kenya and supported by Norway, Saudi Arabia, Belgium, Germany, the U.S. and others, to hold an Expert Meeting on short-lived climate forcers and develop recommendations on future work of the IPCC Task Force on Inventories. 

The Expert meeting was held in Geneva, Switzerland in May 2018 and hosted by the World Meteorological Organization (WMO) and IPCC Secretariat, with generous funding from Switzerland and Norway. The Expert Meeting recommended that the IPCC prepare guidance to estimate emissions of short-lived climate forcers.  

Durin the 49th session of the IPCC, in May 2019, the Panel decided (IPCC-XLIX-7) that the Task Force on Inventories will produce a methodology report on short-lived climate forcers.

The scoping of the new methodology report has not yet been undertaken, but the report will likely include particulate matter, black carbon, and all air pollutants that are precursors to tropospheric ozone and secondary particulate matter – like organic carbon, sulfur oxides (SOx), nitrogen oxides (NOx), ammonia (NH3), carbon monoxide (CO), and non-methane volatile organic compounds (NMVOCs). Methane and halogenated compounds were not included, because inventory methodologies for them are already provided in the 2006 IPCC Guidelines for National Greenhouse Gas Inventories.

The Panel also approved the modalities for preparing the report, which are contained in an annex to the decision and state that:

• the preparatory work for the methodology report (including supporting materials and scoping) is to be completed as soon as possible, starting in the sixth assessment cycle;
• further methodological development will take place in the seventh assessment cycle;
• three to four expert meetings will produce a series of supporting materials to be published after each meeting but no later than 2022;
• these supporting materials will be used to inform the scoping of methodological work for SLCFs;
• the scoping meeting will consider the work of WG I (April 2021) and WG III (July 2021); and
• the report’s outline will be presented for Panel approval soon after the scoping meeting.

The IPCC defines short-lived climate forcers as:

“Gases and particles that affect the climate. They have lifetimes in the atmosphere of a few days to a decade, and many of them are also air pollutants. Human activities contribute to SLCF emissions to the atmosphere. The impacts of SLCF species on climate are complex and depend on multiple factors, for example, where and when they are emitted. Methane is the longest lived SLCF and is also included under the well mixed greenhouse gases.”

You can read the report on short-lived climate forcers prepared by the Co-Chairs of Task Force on National Greenhouse Gas Inventories for the IPCC’s 49th Session here.