Article 6 of the 2015 Paris Agreement sets out how countries (“Parties”) may cooperate voluntarily to implement their nationally determined contributions (NDCs). It is intended to allow higher ambition in mitigation and adaptation while promoting sustainable development, and it conditions cooperation on environmental integrity, transparency and robust accounting, especially to avoid double counting of the same mitigation outcome across countries’ NDCs.
The article establishes three cooperation pathways. Under Article 6.2, Parties may use “cooperative approaches” to transfer and use internationally transferred mitigation outcomes (ITMOs) through bilateral or multilateral arrangements, subject to guidance adopted by the Conference of the Parties serving as the meeting of the Parties to the Paris Agreement (CMA). Article 6.4 creates a UNFCCC-supervised crediting mechanism—referred to by the UNFCCC as the Paris Agreement Crediting Mechanism (PACM)—that registers mitigation activities and issues units (A6.4ERs), including provisions such as a share of proceeds for the Adaptation Fund and cancellation of a portion of units to deliver an overall mitigation in global emissions (OMGE). Article 6.8 establishes a framework and work programme for “non-market approaches”, which support cooperation without international transfers of mitigation outcomes.
Implementation depends on cross-cutting accounting and transparency arrangements that link Article 6 reporting to the Paris Agreement’s transparency system (Article 13), including tracking through registries and, where required, “corresponding adjustments” to ensure that an internationally used mitigation outcome is reflected in only one Party’s NDC accounting. Parties adopted the core “Article 6 rulebook” at COP26, and later CMA decisions have continued to operationalize technical standards and reporting infrastructure. The impacts of Article 6 remain debated, particularly around environmental integrity, governance capacity and the risk of over-crediting.
Background and purpose Article 6.1 of the Paris Agreement recognizes that some Parties may choose to pursue voluntary cooperation in implementing their nationally determined contributions (NDCs) “to allow for higher ambition” in mitigation and adaptation actions, while promoting sustainable development and ensuring environmental integrity.
Article 6 frames cooperative approaches as voluntary tools that may be used in implementing NDCs to support higher ambition. The mechanism established under Article 6.4 is also intended to “deliver an overall mitigation in global emissions”, in addition to enabling the transfer of mitigation outcomes between Parties. Article 6 also links cooperation to sustainable development: cooperative approaches under Article 6.2 are to promote sustainable development, and the Article 6.4 mechanism is intended to contribute to mitigation while fostering sustainable development.
For cooperative approaches under Article 6.2, the Paris Agreement requires Parties to ensure environmental integrity and transparency (including in governance) and to apply robust accounting “to ensure, inter alia, the avoidance of double counting”, consistent with guidance adopted by the Conference of the Parties serving as the meeting of the Parties to the Paris Agreement (CMA). The CMA guidance adopted at COP26 (CMA.3) includes requirements on “corresponding adjustments” and reporting intended to apply these accounting and integrity principles in practice.
Key concepts and terminology Article 6 summaries often use specialized accounting and carbon-market terminology; later sections explain these concepts in more detail.
Internationally transferred mitigation outcomes (ITMOs): quantified mitigation outcomes (emission reductions or removals) transferred between Parties under Article 6.2 and used toward an NDC or another authorized international purpose, subject to agreed reporting and accounting rules intended to avoid double counting. Authorization and first transfer: authorization is a host Party decision specifying whether mitigation outcomes may be used internationally and for what purpose; “first transfer” refers to the first international transfer step that is linked to reporting and, where applicable, accounting under CMA guidance.
Corresponding adjustment: the accounting adjustment used to prevent double claiming between Parties by ensuring a transferred outcome is reflected in only one Party’s NDC accounting, consistent with CMA guidance.
Double counting: umbrella term commonly used for different problems, including double issuance (more than one unit issued for the same outcome), double claiming (both Parties claim the same outcome toward their NDCs), and double use (the same unit is used more than once or for more than one claim).
Mitigation outcome vs. carbon credit: the mitigation outcome is the underlying quantified reduction or removal; a carbon credit is a unit issued by a crediting programme that can represent such an outcome and may be used in Article 6 cooperation if eligible and authorized by Parties.
Registries and tracking and Article 6.4 features: Article 6 relies on registry and reporting infrastructure to record issuance, transfers, cancellations and use, supporting transparency and reconciliation across Parties and time periods. COP26 decisions for Article 6.4 also included a share of proceeds for the Adaptation Fund and cancellation of a portion of units to deliver an overall mitigation in global emissions (OMGE).
Approaches under Article 6 The Paris Agreement offers three ways in which Parties may cooperate on a voluntary basis.
Article 6.2: Cooperative approaches Article 6.2 provides for “cooperative approaches” in which Parties may voluntarily transfer and use internationally transferred mitigation outcomes (ITMOs) without relying on the centralized crediting mechanism established under Article 6.4. Participating Parties are to promote sustainable development, ensure environmental integrity and transparency (including in governance), and apply robust accounting consistent with guidance adopted by the Conference of the Parties serving as the meeting of the Parties to the Paris Agreement (CMA), including measures intended to avoid double counting.
In practice, ITMOs can represent quantified emission reductions or removals and may be expressed in greenhouse-gas metrics (such as tCO2e) or, where Parties determine, in other metrics. Cooperative approaches can be implemented through a variety of bilateral or multilateral arrangements, including crediting-based transfers and policy-based cooperation such as linked emissions trading systems, provided Parties authorize the use of outcomes and apply the agreed accounting framework.
CMA guidance links key accounting steps to authorization and “first transfer”. Where an ITMO is authorized for use toward another Party’s NDC (or other international purposes), Parties apply corresponding adjustments and disclose relevant information through Article 6 reporting under the Paris Agreement’s transparency framework (Article 13).
Commentators debate whether Article 6.2 transfers primarily lower costs and mobilize finance or risk undermining environmental integrity through over-crediting, unambitious baselines (“hot air”), or weak governance; assessments emphasize that outcomes depend on ambition and the strength of accounting, transparency and review safeguards.
Paris Agreement Crediting Mechanism (Article 6.4) Under Article 6.4, Parties established a UNFCCC-supervised crediting mechanism—referred to by the UNFCCC as the Paris Agreement Crediting Mechanism (PACM)—to register mitigation activities and issue units for verified emission reductions or removals, while supporting sustainable development and delivering an overall mitigation in global emissions.
The PACM registers eligible mitigation activities and issues units known as Article 6.4 emission reductions (A6.4ERs), which are recorded in a mechanism registry with unique identifiers to enable tracking (e.g., issuance, transfer, cancellation, and use). COP26 decisions also included a share of proceeds for the Adaptation Fund and cancellation of a portion of issued units to deliver an overall mitigation in global emissions (OMGE).
Host Parties may determine whether A6.4ERs are authorized for international use (for example, toward another Party’s NDC or other international mitigation purposes) or retained as mitigation contribution units intended to support mitigation in the host Party. Authorized A6.4ERs interact with the broader Article 6 accounting and transparency framework intended to avoid double counting, including corresponding adjustments where applicable under CMA guidance.
The mechanism operates under the authority of the CMA and is supervised by the Article 6.4 Supervisory Body, which oversees the mechanism’s implementation framework and centralized infrastructure for registration, issuance and tracking.
Host Parties participate through domestic arrangements, including designating national authorities and providing required approvals for activities and, where relevant, authorizations when A6.4ERs are intended for international use.
In outline, an Article 6.4 activity is developed against approved requirements (including methodologies), validated and registered under the mechanism, monitored and independently verified for a crediting period, and then issued as A6.4ERs into the mechanism registry. Host Party approvals and any authorization for international use are part of this activity cycle, and the registry records whether issued units are authorized for transfer or retained as mitigation contribution units.
Article 6.8: Non-market approaches Article 6.8 establishes a framework for voluntary cooperation through “non-market approaches” (NMAs). Unlike cooperative approaches under Article 6.2 and the crediting mechanism under Article 6.4, NMAs do not involve the international transfer of mitigation outcomes between Parties. UNFCCC guidance describes NMAs as cooperation that can integrate mitigation and adaptation and may also involve finance, technology transfer, and capacity building, while contributing to sustainable development and poverty eradication.
At the COP26 meeting (CMA.3, Glasgow, 2021), Parties adopted a work programme under Article 6.8 and established the Glasgow Committee on Non-market Approaches (GCNMA) to support implementation of the framework. The work programme’s initial focus areas include adaptation, resilience and sustainability; mitigation measures that contribute to sustainable development; and development of clean energy sources. UNFCCC materials describe work programme activities such as identifying opportunities for coordination and synergies across instruments and institutional arrangements, developing and sharing case studies and best practices, and maintaining UNFCCC web-based tools (including a platform and discussion forum) for recording and exchanging information on NMAs.
The GCNMA began its work in 2022 and holds regular meetings and workshops, alongside calls for submissions and technical papers, as part of a multi-year work programme.
Accounting, reporting and transparency architecture Article 6 cooperation is linked to the Paris Agreement’s transparency framework (Article 13). Participating Parties are expected to report what they authorize, transfer, acquire, cancel or use, and how those actions are reflected in NDC accounting, including the corresponding adjustments used to avoid double claiming for authorized international uses.