ISO Meets GHG Protocol: A Unified Carbon Standard for Real Asset Investors

The two most prominent corporate carbon accounting standards are being brought together in the biggest step towards simplification in more than two decades. On 29 July 2026, the International Organization for Standardization (ISO) and the Greenhouse Gas Protocol (GHG Protocol) announced that they will combine their corporate carbon accounting frameworks into a single, co-branded global standard. The two organisations remain separate bodies: it is their standards, not the institutions themselves, that are merging.

For real asset investors and managers, this is not simply a technical footnote to add to carbon accounting reports. Almost every portfolio-level carbon disclosure produced over the last fifteen years, including GRESB, TCFD, lender due diligence packs and SBTi targets, has been built on either the GHG Protocol or ISO 14064 methodology. When the foundation of reporting changes, every report built on it is affected.

The process is being deliberately staggered. Rather than publishing a finished standard overnight, ISO and GHG Protocol are phasing the merger of their standards over several years. A single, integrated public consultation on the combined corporate standard is planned for Q2 2027, with final publication targeted for Q4 2028. In EVORA’s experience, the consolidation of the frameworks is consistent with changes across the reporting landscape: fewer, more structured and more rigorously verified frameworks are replacing the patchwork of reporting requirements that real estate investors have had to navigate over the past decade.

Setting the scene

This move builds on a strategic partnership the two organizations announced in September 2025 and follows through on a commitment made as part of last year’s COP30 action plan to close the gap between the world’s most widely used emissions accounting frameworks. It is expected to remain a live workstream until the ultimate publication in 2028.

The new standard will combine the GHG Protocol’s Scope 1, 2, and 3 with Actions and Market Instruments (AMI) guidance together with ISO’s 14064-1 standard for organisational greenhouse gas accounting. The two bodies intend to produce one trusted methodology that regulators, investors, and reporting companies can point to as a single source of truth.

GHG Protocol has already published the results of its public consultation on the Scope 2 standard revision and released preliminary feedback from its AMI request for information. The workstream now feeds directly into the combined standard.

The Four Aims of Convergence

At a high level, the unified standard is intended to:

1. Remove duplication between GHG Protocol’s Scope 1–3 guidance and ISO 14064-1, which currently overlap in places and diverge in others. This will reconcile the two methodologies so it is easier to report on the GHG accounting in hand.
2. Create a single coordinated consultation process, so that businesses, verifiers, and policymakers only need to engage with one standard-setting process rather than tracking two separate ones on different timelines.
3. Reduce the compliance burden created by fragmented global reporting requirements, particularly for multinational portfolios that must meet both GHG Protocol-based frameworks, such as CDP and SBTi, and ISO-based verification and certification schemes across different markets.
4. Strengthen interoperability with mandatory reporting regimes, including the EU’s CSRD/ESRS and the ISSB’s IFRS S2, both of which currently reference GHG Protocol and ISO methodologies in different ways.

Why this matters for real asset investors and managers

Reporting consistency across jurisdictions. Real estate and infrastructure portfolios are rarely confined to a single regulatory regime. A fund with assets across the UK, EU and North America is often reconciling GHG Protocol-based Scope 3 categorisation with ISO-referenced verification requirements from local certification bodies. A single standard removes a genuine source of inconsistency in portfolio-level carbon footprints.

Lower verification and assurance costs. Third-party verifiers currently need to be fluent in both frameworks, and clients often pay for that dual expertise indirectly through assurance fees. A harmonised standard should, over time, reduce the cost and complexity of getting Scope 1–3 data independently assured.

A more stable target for data infrastructure investment. Asset managers who have spent the last few years building out carbon data collection, categorisation, and Scope 3 estimation processes will want assurance that this investment remains fit for purpose once the standard consolidates. Early indications suggest the combined standard is being designed for continuity with existing Scope 1–3 categories rather than a wholesale redesign, but the detail will only become clear once the Q2 2027 consultation draft is published.

Sharper scrutiny of AMI and market-based instruments. The Actions and Market Instruments workstream – covering how carbon credits, PPAs, and other market instruments can be counted toward targets – is being folded into the same process. Portfolios relying on market-based Scope 2 accounting or offset-supported claims should watch this closely, given the direction of travel across other recent standards has been toward tighter restrictions on market instruments rather than looser ones.

How This Fits Alongside Other Standards Activity

This consolidation sits within a broader pattern rather than in isolation. It follows closely behind ISO’s publication of the consultation draft for ISO 14060, the first independently verifiable international standard for net-zero-aligned organisations, and alongside jurisdiction-specific frameworks such as the UK’s Net Zero Carbon Buildings Standard.

In practice, the relationship should be complementary rather than competing. The unified GHG Protocol/ISO standard will most likely continue to govern how emissions are measured and categorised at the corporate and portfolio level, while frameworks like ISO 14060 and the UK NZCBS govern how credible net-zero claims and building-level performance are established on top of that data. Organisations that get their underlying emissions accounting right will be far better positioned to meet the requirements layered on top of it.

What Real Asset Managers Should Do Between Now and 2028

1. Document current methodology choices. Portfolios that can clearly show which GHG Protocol and/or ISO 14064-1 conventions they currently apply and why will find it far easier to map across to the unified standard once it lands.
2. Engage with the consultation process. The Q2 2027 public consultation will be the primary opportunity to flag real asset-specific issues, particularly around Scope 3 categorisation for tenant and supply chain emissions, before the standard is finalised.
3. Avoid over-rotating on interim guidance. With final publication not expected until Q4 2028, there is a risk of over-investing in workarounds for problems the unified standard may resolve directly. Build data infrastructure that is methodology-agnostic where possible.

 A Final Note on Timings

• 29 July 2026: ISO and GHG Protocol announce intention to merge frameworks
• Q2 2027: Integrated public consultation on the combined corporate standard
• Q4 2028: Final publication targeted
• Through 2028: Live workstream feeding into the Global Stocktake

How EVORA Can Help

Navigating two accounting frameworks has been a persistent, quiet cost for real asset investors for years: reconciling categorisations, managing verifier relationships across both standards, and translating outputs for different regulators. A single standard is good news, but the transition period between now and 2028 will require careful tracking.

If you’d like support benchmarking your portfolio’s current GHG Protocol and ISO 14064-1 methodology choices, or want a clear view of how the consolidation could affect your reporting timelines, our sustainability advisory team would be glad to talk it through.

Glossary

• AMI (Actions and Market Instruments): GHG Protocol workstream governing how carbon credits, PPAs, and other market instruments can be counted toward emissions targets.
• CDP: A global disclosure system through which companies report environmental data, historically built on GHG Protocol methodology.
• CSRD/ESRS: The EU’s Corporate Sustainability Reporting Directive and its European Sustainability Reporting Standards.
• GHG Protocol: The global standard for greenhouse gas accounting and reporting across Scope 1, 2 and 3 emissions.
• Global Stocktake: The UN process, held every five years under the Paris Agreement, assessing collective progress on climate goals.
• GRESB: A global ESG benchmark for real asset investment performance.
• IFRS S2: The ISSB’s climate-related disclosure standard.
• ISO 14064-1: The ISO standard for organisational-level greenhouse gas quantification and reporting.
• ISO 14060: A forthcoming ISO standard for independently verifiable net-zero-aligned organisations.
• SBTi (Science Based Targets initiative): An organisation that validates corporate emissions reduction targets against climate science.
• UK NZCBS: The UK’s Net Zero Carbon Buildings Standard, governing building-level net-zero performance claims.

The integrated public consultation on the combined GHG Protocol/ISO corporate standard is expected in Q2 2027, with final publication targeted for Q4 2028. EVORA will be tracking the consultation closely and will publish further analysis as the draft standard becomes available.