Towards a Common Language for Carbon Accounting: ISO and GHG Protocol Join Forces
Summary
In what could become a common global language for carbon accounting, the International Organization for Standardization (ISO) and the Greenhouse Gas (GHG) Protocol announced a strategic partnership on 9 September 2025. The partnership aims to develop harmonised, co-branded international standards, bringing together the ISO 1406X family of standards with the GHG Protocol’s Corporate Accounting and Reporting Standard, Scope 2 Guidance, and Scope 3 Standard. While there are many perspectives on the differences and overlaps between the two frameworks, we at MyCarbon welcome this partnership. From our point of view, there are three key areas that will be particularly important to watch as the standards move towards integration.
From Broad Principles to Granular Guidance
One of the most important areas to monitor will be how the two frameworks integrate the level of granularity in calculation methods offered by the GHG Protocol into the ISO standards. The GHG Protocol provides clear methodologies for each scope and for all fifteen categories of Scope 3 emissions. ISO, by contrast, sets out the structure for reporting direct and indirect emissions at the organisational level and even at the project level. The integration of these two approaches paves the way for greater interoperability, combining the GHG Protocol’s sector-specific calculation methods with ISO’s principles on materiality thresholds and verification norms. The outcome could be a unified set of recommended calculation methods per sector and Scope 3 category, adopting the GHG Protocol’s detailed approach but with stronger alignment to ISO’s assurance requirements.
Treatment of removals or reductions of GHG
The GHG Protocol’s Land Sector and Removals Guidance remains in draft form and, importantly, does not mandate verification. The fact that this guidance is still only in draft underlines why harmonisation with ISO, which already has robust verification standards, is so critical. ISO 14064-2 provides a detailed framework for quantifying, monitoring, and reporting GHG emissions reductions or removal enhancements at the project level, such as at a carbon capture and storage facility or an anaerobic digester. It will be fascinating to see how the merged framework addresses reductions and removals of GHG, including unified definitions of permanence and leakage in projects, clearer terminology for removals, and consistent methods for quantifying them.
Strengthening Credibility Through Assurance
The GHG Protocol uses the word “may” in the context of verification of GHG calculations or emissions profiles, meaning that third-party verification is optional across several operational boundaries. In contrast, ISO 14064-3 provides a structured framework for verifying and validating reports of GHG emissions, reductions, and removals. ISO standards are built on four key principles of independent assessment:
- Impartiality
- Ethical conduct
- Fair presentation
- Due professional care
Many regulatory bodies worldwide already require ISO 14064-3 verification in mandatory accreditation systems such as emissions trading schemes. The GHG Protocol, meanwhile, focuses primarily on the accounting and reporting of emissions rather than their assurance. At present, the GHG Protocol also does not prescribe a universal materiality threshold; instead, acceptable thresholds are determined by reporting programmes or agreed between companies and verifiers. We anticipate that the integration of the two standards could accelerate the shift towards assurance and verification of GHG emissions reporting as a standard practice rather than an optional one. By combining the GHG Protocol with ISO 1406X standards, companies calculating emissions under the GHG Protocol would also need to demonstrate alignment with ISO’s verification criteria. This evolution would be critical for organisations, regulators, and stakeholders such as investors and capital providers, all of whom rely on accurate and credible sustainability information to make informed decisions.
What’s next?
For businesses, this could mean:
Stronger push for supplier data: The GHG Protocol already encourages supplier-specific data but allows companies to rely on generic factors if needed. Under ISO, however, verification requirements make it harder to justify generic data where supplier data is material. The harmonised framework could therefore turn supplier engagement from a “best practice” into a “standard expectation.”
- Verification as a standard: Third-party assurance, currently optional under the GHG Protocol, may become the norm under the harmonised framework.
- Tighter rules on removals: Organisations using carbon capture, reforestation, or other removal projects will face clearer definitions of permanence, leakage, and accounting boundaries.
- Global consistency: There would be a greater comparability amongst businesses as this could become the common language of carbon accounting
- Regulatory readiness: Ahead of the future potential disclosure laws, businesses could prepare the GHG inventory using the unified framework to be ahead of the curve and even out the cost associated with it before it becomes a solid law.
Looking ahead, the partnership between ISO and the GHG Protocol is not just a technical exercise but a significant step towards a unified, trusted global framework. The integration of the GHG Protocol’s detailed methodologies with ISO’s rigour in assurance could close long-standing gaps between disclosure and verification. With optimistic hopes that this will be a success, this harmonisation will provide the consistency, credibility, and comparability that regulators and investors have long demanded. For businesses, the message is clear: preparing internal systems to align with both frameworks now will place them ahead of the curve once the harmonised standards are finalised.
MyCarbon’s Perspective
At MyCarbon, we view the partnership between ISO and the GHG Protocol as a pivotal step in the evolution of carbon accounting. For many organisations, however, moving from today’s fragmented guidance to a harmonised global standard will be a complex journey. Our team is here to help bridge that gap, working with you to refine existing processes, align with the forthcoming standards, and position your business ahead of the curve.
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