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Credit: UN Climate Change

Access Registry Regulations

What is a mechanism registry?

A registry is a system that keeps track of specific activities and their effects over time. When it comes to climate action, it serves as a digital record that keeps track of the amount of greenhouse gas (GHG) emissions reduced or removed from the atmosphere. In other words, it is an official tracking tool that ensures emissions reductions are accurately recorded, monitored, and used as intended.

The Article 6.4 Mechanism Registry is a specific type of registry created under the Paris Agreement. It records the emission reductions and removals (called A6.4ERs) generated by activities approved under the Paris Agreement Crediting Mechanism (PACM).

These reductions and removals are assigned unique identifiers, making it easy to see when and where they were created, who owns them, and how they are used—whether for trading, meeting climate commitments, or being retired from use.

How does the Article 6.4 mechanism registry work?

Each tonne of reduced or removed emission is represented as an Article 6.4 Emission Reduction (A6.4ER) within the registry, ensuring transparency and accountability. Each A6.4ER issued in the registry receives a unique identifier that provides important details such as:

The activity responsible for the emission reduction or removal
The host Party (country) where the activity is registered
The year ("vintage") in which the A6.4ER was generated

The registry includes accounts that track the ownership of each A6.4ER. Parties (countries) and authorized public or private entities can open accounts to hold, trade, or use these units. The secretariat, acting as the registry administrator, first issues new A6.4ERs into a special "pending account" before distributing them according to the instructions of the activity participants.

Trading and use of A6.4ERs

A6.4ERs can be traded among account holders within the registry. However, their ultimate use depends on whether they have been "authorized" by the host Party:

Authorized A6.4ERs (AERs): If the host Party designates an A6.4ER for use in a cooperative approach under Article 6.2 of the Paris Agreement, it becomes an "Authorized Emission Reduction" (AER). Additional metadata is attached to indicate its purpose, such as which international mitigation goal it contributes to. AERs can be transferred to the international registry or Party registries once interoperability arrangements are in place.
Mitigation Contribution Units (MCUs): If an A6.4ER is not authorized for transfer, it remains within the mechanism registry as an MCU. These units contribute to the host Party's Nationally Determined Contribution (NDC) and cannot be used by other Parties. However, MCUs can support climate finance and domestic environmental programs. Under specific conditions, MCUs may later be authorized and converted into AERs.

Procedural background

Under Article 6 of the Paris Agreement, Parties acknowledged that voluntary cooperation could help achieve their NDCs. Article 6.4 established a market-based mechanism to facilitate this cooperation.

Key decisions defining the mechanism registry and its functions include:

Decision 3/CMA.3: Establishes the rules, modalities, and procedures of the Article 6.4 mechanism.
Decision 7/CMA.4: Elaborates on registry requirements, transaction processes, and connections with the international registry.
Decision -/CMA.6: Provides additional guidance on interoperability with Party registries and ensuring registry access to all Parties.
Decisions 2/CMA.3, 6/CMA.4, and -/CMA.6: Outline requirements for internationally transferred mitigation outcomes (ITMOs), applicable to authorized A6.4ERs (AERs) within the registry.

Frequently Asked Questions (FAQs) on the Article 6.4 mechanism registry

Can I open an account in the mechanism registry? How does it work?

This answer is valid for the final mechanism registry.
Please refer to the interim mechanism registry provisions explained below.

Yes, you can open an account in the mechanism registry by submitting a request through the dedicated interface on the UNFCCC website.

If you’re a public or private entity, you’ll need authorization from a Party (a participating country), agree to the terms and conditions, and pay the account opening fee.

Public and private entities participating in activities can get a holding account based on their Letter of Authorization from the Party that authorized them. Additional accounts can also be opened following the same process.

Can an A6.4ER be authorized by a Party that is not the host Party?

No. Only the host Party (the country where the activity took place) can authorize A6.4ERs issued for that activity.

Can my Party registry connect to the mechanism registry?

Yes. The mechanism registry will allow Party registries to connect if the Party has submitted an initial report confirming its participation in the mechanism and has nominated its registry in that report. This connection will enable the transfer of AERs and provide access to information about holdings and transaction history.

This functionality is part of ongoing interoperability developments by the secretariat.

How does the mechanism registry relate to Article 6.2?

The mechanism registry will be linked to the international registry. This connection will allow the transfer of AERs and enable “pull and view” access to information on holdings and transaction history.

This interoperability feature is currently being developed by the secretariat.

What’s the difference between MCUs, AERs, and CERs?

AER (Authorized Emission Reduction): An A6.4ER that has been authorized for use in achieving a country's NDCs or for other international mitigation purposes. AERs can be transferred to connected registries, including the international registry.
MCU (Mitigation Contribution Unit): An A6.4ER that has not been authorized for international use and instead contributes to the host Party’s NDC. MCUs stay within the mechanism registry but may later be converted into AERs if permitted by the host Party.
CER (Certified Emission Reduction): A unit issued under the Clean Development Mechanism (CDM) for emission reductions before 2021. If certain conditions are met, CERs can be transferred to the mechanism registry and used toward a country’s first or first updated NDC or for voluntary cancellation.

What does "vintage" mean in the registry?

The "vintage" of an A6.4ER refers to the year when the greenhouse gas reduction or removal actually took place. This information is part of the unique identifier assigned to each A6.4ER in the registry.

What are the features and limitations of the interim mechanism registry?

The interim mechanism registry is an offline tool used by the secretariat to issue A6.4ERs, retire transferred CERs and perform the essential set of other mandated transactions before the final mechanism registry goes live. Only Parties and activity participants can open accounts in the mechanism registry. Post-issuance authorization will not be available in the interim registry. The interim mechanism registry will also produce all necessary data, but it will not pre-fill annual reporting for Parties.

When will the final mechanism registry be made available?

The procurement and implementation process for the final mechanism registry is still under way. The secretariat will make the necessary announcements in due course. You can register your interest and get notified when public announcements about the mechanism registry are made.