Carbon markets under Article 6 exist to help countries achieve their Nationally Determined Contributions more cost-effectively. To fully grasp carbon accounting, you need a firm understanding of how NDCs function within the broader Paris Agreement architecture.
What Is an NDC?
Nationally Determined Contributions are defined under Article 4 of the Paris Agreement. Every nation must prepare and maintain successive NDCs that reflect its highest possible ambition.
An NDC is essentially a national emissions target packaged alongside concrete policy measures. Key components typically include:
- A headline emissions reduction target (such as a percentage reduction against a base year).
- A definitive target year (usually 2030 for the current cycle).
- Sector-specific commitments covering energy, transport, land use, industry, and waste.
- Adaptation commitments to build climate resilience.
- Conditional elements that explicitly depend on international support.
The Paris Agreement emphatically avoided imposing top-down targets. Instead, it relies on a global stocktake every five years to dynamically assess collective adequacy and build intense political pressure for greater national ambition.
NDCs are not legally binding emissions targets in a punitive sense. The Paris Agreement legally binds countries to submit and heavily update their NDCs, but the specific numerical targets are self-determined. The ultimate goal is honest participation and progressive enhancement.
The Five-Year Ratchet Mechanism
The ratchet mechanism serves as the engine of progressive ambition. Each Party must submit a new NDC every five years, and each successive submission must push significantly further than the last.
The sequence unfolds neatly:
- 2020: First NDCs submitted.
- 2025: Second NDCs due following the first global stocktake.
- 2030: Third NDCs due.
- 2035: Fourth NDCs due.
The ratchet mechanism operates exactly like a physical wrench. You can only turn it forward to tighten ambition, never backward to loosen it. Although there is no formal enforcement police, reputational pressure strongly discourages backsliding.
What It Means to Achieve an NDC
A country achieves its NDC when its officially reported greenhouse gas emissions fall at or below its target. Countries report this progress through National Greenhouse Gas Inventories, converting all major greenhouse gases to CO2-equivalents using standardized Global Warming Potential (GWP) factors.
Importantly, achieving an NDC does not require a country to meet its target strictly through domestic mitigation. Under Article 6, nations may use internationally transferred mitigation outcomes (ITMOs) to legally contribute toward their success. When Country B purchases ITMOs from Country A and properly logs a corresponding adjustment, Country B's effective emissions tally is instantly lowered.
This sets up a critical distinction:
- Domestic mitigation action: Tangible reductions achieved inside the country's own borders.
- ITMO use: An accounting adjustment negotiated internationally that lowers the nation's NDC bill.
Both pathways are equally legitimate.
Additionality in the NDC Context
In standard voluntary carbon markets, additionality tests whether a project would have occurred without carbon revenue. Under the NDC framework, additionality becomes far more complex.
If a host country pledges to build 20GW of solar power by 2030 and a foreign buyer purchases ITMOs from a solar project inside that nation, is that project additional? The emission reduction might already be baked into the host country's baseline domestic plans.
This scenario highlights why Article 6.2 rules ruthlessly mandate corresponding adjustments. If a country sells ITMOs derived from activities already embedded in its NDC, it must urgently choose to either:
- Find further domestic reductions to compensate for what it sold.
- Revise its overall NDC ambition upward to safely account for the exported reductions.
Scenario: Safeguarding NDC Integrity Country X has a target to reduce emissions by 30%. It confidently expects to hit 35%, leaving a comfortable 5% headroom.
It opts to sell 3% of that headroom as ITMOs to Country Y. Country X logs a corresponding adjustment securely. Country X must now achieve 33% domestically (its base 30% plus the 3% exported). Meanwhile, Country Y happily counts the purchased 3% against its own official target.
Why Countries Pursue Article 6
Over 78% of all submitted NDCs explicitly indicate an intention to use at least one Article 6 mechanism. This stunning adoption rate stems from basic economics.
Meeting NDC targets entirely through domestic action can be prohibitively expensive. International cooperation allows different nations to leverage their unique advantages:
- Developed buyer countries can offset their extremely expensive domestic abatement costs by purchasing ITMOs from regions with lower-cost opportunities.
- Developing host countries can utilize Article 6 as a powerful tool to attract direct international climate finance for vital green infrastructure.
- Countries with ambitious conditional NDCs can seamlessly convert these conditional pledges into reality by securing structured, ongoing international investments.
Country Use vs. Corporate Use
Understanding who holds the credits fundamentally changes the accounting rules. The Article 6 framework is purpose-built for sovereign cooperation between nations, which differs wildly from a corporation purchasing voluntary carbon credits.
When a country uses Article 6 ITMOs:
- The ITMO is formally authorized by both governmental parties.
- A corresponding adjustment mathematically ensures the reduction is counted accurately.
- The transaction visibly progresses through official UNFCCC reporting channels.
When a company purchases voluntary carbon credits:
- The company typically retires the credit in a private voluntary registry (like Verra or Gold Standard).
- No corresponding adjustment is automatically triggered unless the credit carried a specific Article 6 authorization.
- The emission reduction technically remains housed within the host country's national inventory, natively contributing to its NDC success.
If a corporation buys an authorized A6.4ER, the host country has surrendered that emission reduction and must find domestic replacements to meet its own NDC. In contrast, if a corporation cheerfully buys a standard mitigation contribution unit, that emission reduction inherently benefits the host country's NDC progress while offering the company a voluntary offset claim. Article 6 deliberately engineered these layers to accommodate both strict national accounting and flexible private investment.
Key Takeaways
- 1NDCs are self-determined national climate plans that must ratchet upward every five years under the Paris Agreement
- 2Countries can achieve their NDCs through domestic mitigation, ITMO purchases, or a combination of both - both pathways are equally legitimate
- 3Over 78% of submitted NDCs indicate intent to use Article 6 mechanisms, driven by the cost savings of international cooperation
- 4When a host country sells ITMOs from activities already in its NDC, it must find additional domestic reductions or raise its ambition to compensate
- 5Corporate voluntary credit purchases without corresponding adjustments do not remove the reduction from the host country's NDC ledger - a critical distinction from sovereign ITMO trades