The Greenhouse Gas (GHG) Protocol remains the backbone of corporate, project-level, and policy accounting for greenhouse gas emissions. In 2025, it stands at an inflection point: a substantial revision of core standards, deeper alignment with jurisdictional disclosure rules, and most consequentially a formal partnership with ISO to co-develop a harmonised portfolio of GHG accounting standards. Together, these developments promise a decisive step toward a consistent, globally interoperable system for emissions measurement and reporting.

This article explains what has changed (and what has not) across the GHG Protocol suite in 2025, how the Protocol is integrating with fast-evolving disclosure regimes, and what the ISO–GHG Protocol partnership could mean for companies, investors, auditors, and policymakers. It also highlights priority technical workstreams now underway and offers a practical table to help organisations select the right GHG Protocol standard for their needs.

A revised foundation and a broader perimeter

The GHG Protocol’s revised corporate standard suite clarifies core principles, boundaries, and quality criteria across scope definitions, consolidation, and reporting architecture, reflecting lessons from two decades of practice and the demands of new disclosure regimes. Organisations will recognise enduring concepts, control and equity share, scopes 1–3, relevance, completeness, consistency, transparency, accuracy, now framed with updated guidance to improve comparability and assurance-readiness across markets. [1]

Alongside the revision, the Protocol has published a concise overview of how its standards intersect with emerging disclosure frameworks, mapping where GHG inventory content underpins regulatory reporting and where additional narrative, governance, and financial-materiality elements must be layered in (e.g., under international or jurisdictional rules). For preparers, this integration guide is a practical bridge between “how to count” and “what to disclose.” [2] Clear Scope 3 accounting is increasingly necessary to comply with emerging jurisdictional disclosure rules (e.g., California SB 253).

A landmark ISO–GHG Protocol partnership

In September 2025, ISO and the GHG Protocol announced a strategic partnership to harmonise their existing portfolios and co-develop new standards, with dual-logo outputs expected to cover corporate, product, and project accounting. The scope explicitly includes alignment between the ISO 1406X family and the GHG Protocol Corporate, Scope 2 and Scope 3 Standards, plus a joint product carbon footprint standard, an area of rapidly growing demand as companies seek more granular value-chain data to drive decarbonisation. The stated aim is to deliver a “common global language” for emissions accounting that reduces market confusion, increases policy consistency, and lowers reporting burden. [3]

This is more than a coordination pledge. It creates a governance mechanism for long-term co-development, with technical processes integrating expert communities across ISO and GHG Protocol. In practical terms, companies could plan on one converged set of core rules serving as the basis for both voluntary protocols and regulatory references, critical for auditors and verifiers who require stable, consistent criteria. The partnership has been welcomed by capital markets standard-setters and G7-adjacent business fora, signalling momentum toward a more consolidated global baseline. [3]

Technical workstreams: what’s moving in 2025

The GHG Protocol’s governance and technical pipelines are busy in 2025, with multiple workstreams shepherded by Technical Working Groups (TWGs) and the Independent Standards Board (ISB):

• Scope 2 Guidance revision. The ISB approved a 60-day public consultation on updates to location- and market-based methods. Proposed changes include updated emission-factor hierarchies and hourly and regional deliverability criteria for market-based claims, tempered by feasibility measures, load profiles for hourly matching, small-entity exemptions, a legacy clause for existing contracts, and phased implementation before mandatory adoption. [4]
• Corporate Standard topics (phase 2). Active discussions include base-year recalculation and data-quality improvements, building on earlier work on consolidation approaches. Preliminary outcomes presented to the ISB will inform downstream assurance and comparability. [4]
• Scope 3 revisions. Phase 1 revisions have gone to the ISB; phase 2 starts with boundary-setting across the 15 Scope 3 categories, an area where users have long requested crisper criteria to separate inventory from avoided-emissions narratives and to align supplier-level product data with inventory roll-ups. [4]
• Actions & Market Instruments (AMI). A Phase 1 white paper will outline multi-statement reporting of actions and instruments (e.g., EACs, offsets, transition certificates) in a comprehensive GHG report, aiming to improve transparency and avoid claim inflation or double counting. [4]
• Forest carbon accounting. Proposals are before the ISB, which is weighing trade-offs across permanence, leakage, and baselines, issues central to both compliance and voluntary markets. [4]

Using the suite beyond the corporate inventory

The GHG Protocol is not only a corporate inventory standard. Its suite spans policy evaluation, mitigation goal-setting, city-scale inventories, projects, and product footprints, useful for companies that engage in policy advocacy, run climate programmes, or design low-carbon products and services.

• Corporate Value Chain (Scope 3) Standard. The authoritative framework for measuring and reporting value-chain emissions, structuring 15 categories from purchased goods and services to use of sold products and end-of-life. It remains the de facto reference for regulators and investors expecting full value-chain disclosures. [5]
• Global Protocol for Community-Scale GHG Emissions (GPC). Essential for city and regional programmes and for companies partnering with municipalities on ecosystem decarbonisation, infrastructure, and just transition. [6]
• Mitigation Goal Standard. For public and private actors setting and tracking progress to absolute or intensity-based goals, including base-year and fixed-level targets. [7]
• Policy and Action Standard. To estimate the ex-ante and ex-post GHG effects of policies or discrete actions, useful when corporates contribute to policy pilots or sector initiatives and wish to attribute emissions impact credibly. [8]
• Product and Project standards. Product rules support cradle-to-gate or cradle-to-grave accounting tools that many buyers now require in procurement; the Project Protocol remains fundamental for project-based accounting and for interpreting claims associated with interventions. [9][10]

Table 1. Selecting the right GHG Protocol standard in 2025

Objective	Recommended GHG Protocol standard(s)	Primary users	Typical outputs
Company-wide inventory (Scopes 1–3)	Corporate Accounting & Reporting; Corporate Value Chain (Scope 3)	Corporate reporters, auditors	Annual inventory; basis for jurisdictional disclosure
Electricity procurement strategy	Scope 2 Guidance (revisions in consultation)	Energy buyers, utilities, auditors	Location- and market-based Scope 2; hourly/deliverability claims
Product carbon footprint	Product Standard (and forthcoming ISO–GHGP joint PCF standard)	Product teams, suppliers, customers	PCF (cradle-to-gate/-grave), procurement specs
Project-level intervention	Project Protocol	Developers, financiers, verifiers	Project GHG report; crediting basis (where applicable)
Policy or programme impact	Policy and Action Standard	Policymakers, corporates in coalitions	Ex-ante/ex-post GHG impact estimates
Goal-setting and tracking	Mitigation Goal Standard	Corporate sustainability, public agencies	Target definition; progress tracking
City/regional footprints	GPC	Cities, regions, corporate partners	Community-scale inventory

Note: Dual-logo standards with ISO are in development for corporate, product, and project scopes; consult partnership updates for timing. [3]

Interoperability with disclosure regimes

The GHG Protocol’s integration guide provides a roadmap for aligning inventories with multi-jurisdictional disclosure rules. Key themes for reporters in 2025 include: (i) scope coverage expectations (Scope 3 increasingly required or strongly expected), (ii) the role of assurance and internal controls, and (iii) the delineation between the inventory (numerical accounting per GHG Protocol) and the disclosure narrative (governance, strategy, risk, metrics and targets). [2]

• ISSB and national adoptions. Many jurisdictions are localising or referencing ISSB’s global baseline; inventories prepared under the GHG Protocol provide the emissions metrics backbone. The ISO–GHG Protocol convergence should further simplify cross-market reporting and audit. [3]
• US and state rules. California’s SB 253 mandates Scope 1–3 disclosures for large companies, with assurance phasing and a public platform. A GHG Protocol-compliant inventory is the most robust starting point for methodology consistency.
• Other national regimes. Australia’s ASRS and similar rules emphasise Scope 3 and scenario analysis—again anchored by inventory quality and traceability.

What companies should do now

1. Lock in inventory quality. Treat your GHG inventory like financial data: document boundaries and consolidation approach, upgrade activity-data pipelines (especially for Scope 3 purchased goods and services), and implement data-quality scoring. The revised corporate materials sharpen expectations on recalculation, restatements, and transparency. [1]
2. Plan for Scope 2 evolution. If you disclose market-based figures, evaluate your ability to meet potential hourly matching and deliverability criteria. Assess contract vintages, grid-region definitions, and data access, and model phased transition scenarios (including exemption thresholds for smaller entities). [4]
3. Strengthen value-chain engagement. The Scope 3 Standard remains the lodestar, but supplier-level PCFs are rising in importance; prepare to integrate product-level data with accounting category roll-ups, supported by the forthcoming ISO–GHG Protocol joint product standard. [5][9][3]
4. Clarify claims on actions & instruments. Expect tighter expectations for multi-statement reporting (e.g., separate your inventory totals from claims associated with certificates, credits, and avoided emissions). This will help mitigate greenwashing risk and improve assurance outcomes. [4]
5. Anticipate dual-logo standards. Track the ISO–GHG Protocol work programme and, where feasible, design internal policies and controls that will remain valid across both brands, simplifying assurance and regulator engagement across borders. [3]

Outlook: from plurality to coherence

For years, companies have navigated overlapping standards: GHG Protocol for counting; ISO for systems and verification; a patchwork of disclosure rules for reporting. In 2025, the centre of gravity is shifting toward coherence. The GHG Protocol’s revisions, its explicit mapping to disclosure requirements, and the ISO partnership together indicate a more stable, interoperable landscape ahead, one where organisations can spend less time reconciling rulebooks and more time reducing emissions.

That is good news for markets and the climate. As product-level data mature, hourly electricity attributes scale, and policy evaluation methods converge with inventory practice, the GHG Protocol will continue to serve as the technical spine of decarbonisation, now with a clearer path to global harmonisation and assurance-ready reporting. For practitioners, the work remains exacting; the direction of travel, finally, is unmistakably aligned.

References:

[1] GHG Protocol, Revised Standard (consolidated corporate guidance). https://ghgprotocol.org/sites/default/files/standards/ghg-protocol-revised.pdf

[2] GHG Protocol, Overview: Integration with Disclosure Rules (Jan 2025). https://ghgprotocol.org/sites/default/files/2025-01/Overview-Integration-Disclosure-Rules-Jan-2025.pdf

[3] ISO, “ISO and GHG Protocol announce strategic partnership to deliver unified global standards for greenhouse gas emissions accounting,” 9 September 2025. https://www.iso.org/news/2025/09/iso-and-ghgp-partnership

[4] GHG Protocol, “Newsletter: September 2025 – ISO partnership; Scope 2 consultation; TWG updates; AMI workstream.” https://ghgprotocol.org/blog/ghg-protocol-newsletter-september-2025

[5] GHG Protocol, Corporate Value Chain (Scope 3) Accounting and Reporting Standard. https://ghgprotocol.org/sites/default/files/standards/Corporate-Value-Chain-Accounting-Reporing-Standard_041613_2.pdf

[6] GHG Protocol, Global Protocol for Community-Scale GHG Emissions (GPC). https://ghgprotocol.org/sites/default/files/standards/GPC_Full_MASTER_RW_v7.pdf

[7] GHG Protocol, Mitigation Goal Standard. https://ghgprotocol.org/sites/default/files/standards/Mitigation_Goal_Standard.pdf

[8] GHG Protocol, Policy and Action Standard. https://ghgprotocol.org/sites/default/files/standards/Policy%20and%20Action%20Standard.pdf

[9] GHG Protocol, Product Standard. https://ghgprotocol.org/product-standard

[10] GHG Protocol, Project Protocol. https://ghgprotocol.org/project-protocol