ISO & GHG Protocol Combine: What the New Unified Carbon Accounting Means

What Happened

On September 9, 2025, ISO (International Organization for Standardization) and the GHG Protocol (by WRI & WBCSD) announced a strategic partnership to harmonize their greenhouse gas (GHG) accounting and reporting standards.

Key points from the agreement:

Their existing GHG standards (ISO's 1406X family + GHG Protocol's Corporate, Scope 2, Scope 3 Standards) will be combined into harmonized, co-branded international standards.
They will also co-develop a joint product carbon footprint standard to meet demand for more granular emissions data across value chains.
The aim is to produce a common global language for emissions accounting, to simplify reporting, improve consistency, reduce confusion / duplication, and better support decarbonization efforts.

Why It Matters

Challenge Before	What the Unified Framework Offers
Multiple overlapping standards (ISO vs GHG Protocol) with sometimes differing terminology, verification guidance, or boundary definitions.	A single, co-branded standard reduces ambiguity and could reduce the need for organizations to translate or adapt reports for different frameworks.
Fragmented metrics across corporate, product, and project-level accounting.	Harmonization across all levels (corporate / product / project) will allow more consistent measurement and comparability.
High burdens in gathering Scope 3 / value chain emissions data, due to lack of alignment or varying methodologies.	A shared standard for product carbon footprints + aligned methodology for Scope 3 interpretation can simplify and strengthen data validity.
Regulatory / investor expectations using different references.	With unified standards, regulators, investors, auditors will have clearer, more consistent references. Helps reduce risk of misalignment.

What's Changing & What's Transitional

Co-branded standards: The upcoming standards will bear both ISO and GHG Protocol marks.
New / merged documents: Future standards will merge elements from ISO 1406X series and from key GHG Protocol standards (Corporate Accounting & Reporting; Scope 2; Scope 3).
Product-level standard: A joint product carbon footprint standard is being developed.
Verification / assurance processes: Presumably, verification guidance will be harmonized, but many details (how audits or verifications will transition) are still in work.

What Organizations Should Do Now

While full implementation details are still being developed, companies and institutions preparing for the transition can start positioning themselves to adapt smoothly:

1. Map current practices

Identify how your organization currently uses ISO 14064 / other ISO 1406X standards and/or GHG Protocol standards (for corporate, product, scope 2/3).
Note gaps, overlaps, mismatches in terminology, boundary definitions, etc.

2. Strengthen Scope 3 / value chain data

Because product carbon footprinting and more granular value chain emissions are central to the new combined standard, start improving data collection, supplier engagement, estimation methods where needed.

3. Review verification / audit arrangements

Talk to your third-party verifiers / auditors about how they will adapt to the unified standard.
Ensure that your data systems and documentation are robust, traceable, transparent.

4. Watch regulatory alignment

Monitor how this unified framework is referenced or required by emerging regulations (e.g. EU CSRD, ISSB, other jurisdictional climate disclosure rules).
If your organization reports across jurisdictions, anticipate which standard references may change.

5. Engage in feedback / working groups

ISO and GHG Protocol are likely to form technical committees / working groups to finalize standards. Organizations that can contribute can help ensure usability and relevance.

Potential Risks & Things to Watch

Weaker rules risk: Harmonization should not mean watering down requirements. Some stakeholders warn that merging needs to preserve rigor.
Transition period complexity: For a time, organizations may need to maintain compliance/reporting against older standards while shifting to the combined one.
Cost and capacity issues: More detailed value-chain / product-level accounting may create resource burdens, especially for small / midsize firms.
Governance & transparency: It's crucial that development processes remain inclusive, with inputs from a wide range of stakeholders (SMEs, developing country perspectives, civil society) so that the standards are usable and fair.

Implications for ESG / Sustainability Professionals

The unified standard is likely to become a de facto global baseline for GHG accounting and reporting. Being ahead of the curve gives a competitive / reputational advantage.
Integrated frameworks make comparing performance across peers, supply chains, sectors easier, improving benchmarking, investor communication.
Helps simplify audit and assurance work, reducing the overhead of demonstrating compliance with multiple frameworks.
Push toward more transparency and narrower tolerances for estimation / uncertainty; data quality and rigor will matter more.

Conclusion

The ISO-GHG Protocol partnership marks a major turning point in the carbon accounting landscape. What was once a fragmented set of rules and frameworks is moving toward a unified, coherent set of standards covering corporate, product, and project emissions.

For organizations, the message is: start preparing now. Those who adapt early—strengthening data systems, clarifying internal definitions, engaging in the standardization process—are likely to benefit most.

Ready to prepare your organization for the unified carbon accounting standards? Contact Sustain74 to discuss how we can help you map your current practices, strengthen your Scope 3 data collection, and position your organization for a smooth transition to the new harmonized framework.