Q: What is double counting?

Double counting is a situation in which a single greenhouse gas emission reduction or removal is counted more than once towards achieving climate change mitigation. Double counting can occur through double issuance, a situation in which more than one emissions unit is issued for the same emissions or emission reductions; double use, a situation in which the same emissions unit is counted twice towards achieving climate change mitigation; and double claiming, a situation in which the same emission reduction or removal is claimed by two different entities towards achieving climate change mitigation: once by the country in which the emission reduction or removal occurs, and once by the country or entity using an emissions unit, such as an aeroplane operator under CORSIA.

Q: What is CORSIA?

In 2016, the Assembly of the International Civil Aviation Organization (ICAO) established the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) to help achieve its aspirational goal of carbon-neutral growth starting in 2021. Under the CORSIA, aeroplane operators will be required to purchase eligible emissions units to meet their carbon offsetting requirements. Carbon offset-crediting programs that wish to provide offset credits for use under CORSIA must be approved by the ICAO Council.

Q: What is the purpose of the Guidelines? Who is the intended audience?

These Guidelines are written for carbon offset-crediting programs. The Guidelines are intended to assist programs in establishing or revising relevant program documents – such as standards, procedures, guidelines and forms – in order to implement good practices and satisfy the provisions for avoiding double counting in the CORSIA Emissions Unit Eligibility Criteria.

Q: Who are the members of the Avoiding Double Counting Working Group? What was their process for developing the Guidelines?

The Guidelines were developed through a multi-stakeholder consensus decision-making process, by a working group consisting of representatives of the American Carbon Registry, Carbon Market Watch, Climate Action Reserve, Environmental Defense Fund, the Gold Standard Foundation, the International Emissions Trading Association, Verra, and the World Wildlife Fund, with critical input from outside experts. The “Avoiding Double Counting (ADC) Working Group” defined consensus as no dissent. The entire content of the Guidelines reflects a consensus outcome of the ADC Working Group, with one important exception:


ADC Working Group members Carbon Market Watch, Environmental Defense Fund, and World Wildlife Fund stress that while paragraph 77d in the Annex to Decision 18/CMA.1 on "Modalities, procedures and guidelines for the transparency framework for action and support referred to in Article 13 of the Paris Agreement" and paragraph 17 of Decision 4/CMA.1 on "Further guidance in relation to the mitigation section of decision 1/CP.21” provide important foundational elements for avoiding double counting, application of these CMA Decisions:


a) does not necessarily represent best practice,

b) may not be sufficient to avoid all forms of double counting, and

c) could be undermined by future CMA decisions.


For example, if the CMA were, in the future, to decide that Parties need not make corresponding adjustments when authorizing the use, for purposes other than towards NDCs, of credits issued for emissions reductions and removals originating outside the scope of NDCs, such a decision, in the view of these Working Group members, would allow double counting of mitigation efforts with CORSIA, undermining CORSIA’s environmental integrity. In such a case, these Working Group members would object to the use of such double counted credits for CORSIA compliance even though the Guidelines could be interpreted to allow such use.


The ClimateWorks Foundation initiated the working group process, provided financial support, and participated in ADC Working Group deliberations. The Meridian Institute served as co-convener of the ADC Working Group, facilitated the meetings of the working group and assisted the group to achieve a consensus outcome. The Stockholm Environment Institute supported the process through the involvement of Derik Broekhoff and Lambert Schneider, two subject matter experts who prepared an initial options paper, followed by successive drafts of the Guidelines based on substantive inputs from Working Group members.

Q: The Guidelines are published as “Version 1.0.” When will another version be released?

The Guidelines presented here are a first version. They may be updated in the future considering any new standards and recommended practices (SARPs) adopted or amended under ICAO or any decisions adopted by the CMA, in order to support consistency between these Guidelines and decisions under ICAO and the Paris Agreement.

Q: Is it possible to submit comments on the Guidelines, and if so, how?

Yes, the Guidelines are open for comments, which will be reviewed and incorporated in the event that a second version of the Guidelines is released. The timeline for a second version is uncertain, for the reasons noted above. To submit comments, please email with the subject line “Comments on the Guidelines Version 1.0” and include your name and organization in the body of the email.

Q: How can I learn more?

To learn more about the Avoiding Double Counting Working Group, you may email or directly contact a Working Group member.