GHG Protocol and ISO Merger: The New Single Carbon Standard

For decades, corporate carbon accounting has run on two parallel rulebooks: 

• The GHG Protocol Corporate Standard, with its familiar Scope 1, 2 and 3 structure; 

• And the ISO 1406X family, led by ISO 14064-1, ISO's standard for measuring and reporting organisational greenhouse gas emissions.  

The two broadly agree, but not entirely, and companies working across both have long had to reconcile differences in terminology, boundaries and reporting requirements. 

That is about to change. On 29 July 2026, the GHG Protocol and the International Organization for Standardization (ISO) confirmed they will consolidate their corporate carbon accounting standards into a single, co-branded global standard. It is one of the most significant shifts in carbon reporting in over a decade, and it will shape how every organisation measures and reports emissions from 2028 onwards. 

Why are the GHG Protocol and ISO standards merging?

The rationale is straightforward: fragmentation helps nobody. The GHG Protocol and ISO standards were developed separately, with different scopes and different verification guidance. A business reporting under the GHG Protocol for a customer questionnaire, then verifying under ISO 14064-3 for an assurance engagement, is effectively translating between two dialects of the same language. Multiply that across auditors, software providers, consultants and regulators, and the cost of maintaining two systems becomes hard to justify. 

The consolidation aims to fix this at source. One standard, one set of definitions, one public consultation process, and consistency across markets and jurisdictions. GHG Protocol CEO Tim Mohin put it plainly: a single corporate standard will simplify reporting, reduce duplication, and let companies spend more time reducing emissions rather than reconciling frameworks. 

When will the new GHG Protocol and ISO standard be published?

The groundwork was laid on 9 September 2025, when ISO and the GHG Protocol announced a strategic partnership to harmonise their portfolios. At that stage the plan was co-branded standards developed in parallel, covering corporate accounting, product carbon footprints and project-level accounting. 

The July 2026 announcement goes further. Rather than updating each standard separately, the two organisations will now fold the GHG Protocol's Scope 1, Scope 2, Scope 3 and Actions and Market Instruments (AMI) workstreams together with ISO 14064-1 into one consolidated corporate standard. 

The timeline set out in the new Standard Development Plan is: 

• Q2 2027: a draft of the consolidated standard published for a single, integrated public consultation 

• Q4 2028: publication of the final joint corporate standard 

In the meantime, the technical work continues. The Scope 2 consultation closed with nearly 1,100 responses from 56 countries, and the working groups meet through late 2026 to reconcile that feedback. The planned Scope 3 consultation, originally expected in the second half of 2026, may change as the Scope 1, 2 and 3 work is brought together into the new joint standard. A joint product carbon footprint standard, building on ISO 14067 and the GHG Protocol Product Standard, is being developed in parallel. 

Crucially, the existing standards remain in force until the new one is published. 

What is likely to change under the new ISO X GHG Protocol standard?

The new combined standard will bring together ISO's corporate standard with changes the GHG Protocol was already developing across Scope 2, Scope 3 and Actions and Market Instruments (AMI).

The final content will not be settled until after the 2027 consultation, so anything beyond the timeline is informed speculation. But the consultation materials and standard development plan give some strong signals. 

Multi-statement reporting. The most striking potential change is that companies might report multiple distinct statements, rather than a single inventory: 

• Statement 1 (physical inventory): operational emissions across Scope 1, Scope 2 location-based only, and Scope 3. This is the "foundation" statement. 

• Statement 2 (market-based inventory): market-based accounting across Scope 1, 2 and 3, using environmental attribute certificates. Crucially, this is where the Scope 2 market-based method as we know it today could be extended to cover things like green steel, cement, chemicals, sustainable aviation fuel (SAFs) and renewable natural gas, not just electricity. 

• Statement 3 (GHG impact statement): beyond-value-chain mitigation, carbon dioxide removal and financed reductions, using consequential accounting against a counterfactual baseline. 

• Statement 4 (non-GHG indicators): KPIs and intensity metrics that don't reduce to a tonnage figure. 

The idea is to keep these different types of climate information separate, rather than rolling everything into a single carbon footprint number. The physical emissions a company is responsible for, the environmental attributes it purchases through market instruments, and the impact of climate action beyond its value chain could all be reported separately.

Market instruments beyond Scope 2. As highlighted above, this is closely linked to the proposed Statement 2 market-based inventory. Folding the AMI workstream into the corporate standard could broaden reporting well beyond today's market-based Scope 2 figure, with market-based accounting potentially extending into other scopes and companies reporting the consequences of their decarbonisation actions alongside their inventory. This is potentially one of the biggest conceptual changes being explored. Today, most companies will recognise market-based accounting through renewable electricity tariffs, PPAs and certificates. The AMI work could apply a similar principle to other products and fuels, allowing the environmental attributes associated with lower-carbon production to be allocated through certificates.

Exactly how this would work in practice - and whether these approaches make it into the final standard - is still up for discussion.

It is also one of the areas likely to attract the most debate. NewClimate Institute and others have flagged a real risk that, without a strict hierarchy between statements, companies could end up implicitly netting Statement 3 impacts against their Statement 1 inventory in communications, even if the standard itself keeps them formally separate. 

Read our detailed guide on the proposed Scope 2 changes for more information.

Tighter Scope 3 reporting requirements. The proposed scope 3 changes point towards more granular data, greater transparency about how emissions are calculated, and tighter rules around what can be excluded.

Verification built in from the start. ISO 14064-1 was designed with third-party verification in mind, and its influence on the merged standard is likely to raise expectations on data quality, documentation and assurance readiness across the board. 

How should businesses prepare for the new standard?

Keep reporting under the current standards. The consolidated standard is over two years away, and transition arrangements will be confirmed nearer the time. But the direction is clear enough to prepare for: stronger data foundations, more granular Scope 3 activity data rather than spend-based estimates, and reporting systems flexible enough to produce multiple statements rather than one number. 

If you already measure your full footprint properly, with transparent methods and good underlying data, this consolidation should make life simpler, not harder. One standard, one language, and less time spent translating between frameworks. We will be following the Q2 2027 consultation closely and will break down the draft standard as soon as it is published.

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