Avoidance of double counting is a foundational integrity principle in international carbon markets and greenhouse gas accounting. It prevents the same tonne of emission reduction or removal from being counted twice toward climate commitments—whether by two countries, by a country and a company, or under two overlapping schemes.
The concept is most prominently codified in Article 6 of the Paris Agreement, which governs cooperative approaches between Parties. Article 6.2 requires that countries engaging in the transfer of Internationally Transferred Mitigation Outcomes (ITMOs) apply corresponding adjustments: when one country sells a mitigation outcome, it must add the transferred tonnes back to its own emissions inventory, while the buyer subtracts them. This mechanism prevents both the host and the acquiring country from claiming the same reduction toward their respective Nationally Determined Contributions (NDCs).
Double counting can take several forms:
- Double issuance — the same reduction generates credits under two separate programs.
- Double use — one credit is used twice (e.g., retired by two buyers).
- Double claiming — both the host country and a foreign buyer (or a company under CORSIA) count the same tonne.
The principle also underpins CORSIA, the International Civil Aviation Organization's offsetting scheme for international aviation, which requires that host countries authorize and apply corresponding adjustments for credits used by airlines. Voluntary carbon market standards such as Verra and Gold Standard have likewise updated their methodologies to align with Article 6 rules adopted at COP26 in Glasgow (2021) and refined at subsequent COPs.
Robust avoidance of double counting depends on transparent registries, consistent reporting under the Paris Agreement's Enhanced Transparency Framework, and reconciliation between national inventories and market transactions. Without it, headline emission reduction figures can overstate real-world mitigation, undermining the environmental integrity of the entire climate regime.
Example
In 2021 at COP26 in Glasgow, negotiators agreed on Article 6 rules requiring Switzerland and Ghana to apply corresponding adjustments to their national inventories when transferring mitigation outcomes from a clean cookstove project, ensuring the reductions counted only once toward NDCs.
Frequently asked questions
Through corresponding adjustments under Article 6.2: the selling country adds transferred tonnes back to its inventory while the buyer subtracts them, so only one party claims the reduction toward its NDC.
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