Overview
The GHG Protocol (Greenhouse Gas Protocol) is a set of standards and tools developed jointly by the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD). First published in 2001, it has become the most widely used international greenhouse gas accounting framework in the world. If a company reports its carbon footprint, sets a science-based target, or issues a green bond, it almost certainly used the GHG Protocol as its measuring stick.
The Protocol’s central contribution is the three-scope framework, which organises emissions by their source and relationship to the reporting company. This framework is now so embedded in corporate reporting that “scope” language appears in regulatory filings, investor questionnaires, news coverage, and political speeches, often without explicit attribution. The GHG Protocol is the grammar of corporate climate disclosure.
The Protocol covers multiple greenhouse gases, not just CO2 but also methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulphur hexafluoride (SF6), and nitrogen trifluoride (NF3). These are all converted into CO2-equivalent (CO2e) using their respective global warming potentials (GWPs), allowing a single aggregated figure. For context on why some of these gases matter so much: HFCs, for example, are now addressed by the Montreal Protocol Kigali Amendment precisely because of their potency as climate pollutants.
The Three Scopes
The GHG Protocol divides emissions into three categories, called scopes, based on where they occur relative to the reporting organisation. See GHG Scopes for a full treatment, but briefly:
Scope 1 covers direct emissions from sources the company owns or controls: combustion in company boilers and furnaces, company-owned vehicles, intentional and unintentional releases from industrial processes.
Scope 2 covers indirect emissions from purchased energy, mainly electricity, heat, steam, and cooling. The company does not produce these emissions itself, but its demand for energy drives them. Scope 2 can be accounted for using market-based methods (renewable energy certificates) or location-based methods (the average grid emissions factor).
Scope 3 covers all other indirect emissions in the company’s value chain, both upstream (suppliers, raw materials, business travel, employee commuting) and downstream (product use, end-of-life disposal). Scope 3 is typically the largest category for most companies and the hardest to measure. For financial institutions, Scope 3 Category 15 covers financed emissions, the emissions associated with loans and investments.
Corporate Standard vs Other Standards
The GHG Protocol family includes several distinct standards. The Corporate Accounting and Reporting Standard (the “Corporate Standard”) is the main framework most people mean when they say “GHG Protocol.” It sets the rules for company-level inventories. Separate standards cover project-level accounting, corporate value chain (Scope 3 specifically), product lifecycle emissions, and city-level inventories.
The Protocol also underpins most national and regional compliance systems. The EU Emissions Trading System (Cap-and-Trade), reporting requirements under the CSRD, the US EPA’s mandatory reporting rule, and the accounting methodologies used in national emissions inventories all draw on GHG Protocol principles. It is, in a meaningful sense, the foundational layer of the entire global carbon accounting system.
Limitations and Evolution
The GHG Protocol’s dominance is also a source of tension. Its Scope 3 standard, in particular, is criticised for allowing inconsistent methodologies, double-counting between companies in the same supply chain, and significant estimation error. When a company claims a Scope 3 figure, the underlying data quality varies enormously.
The Protocol was last updated in 2011 (Corporate Standard). Discussions about updating it, particularly to address financed emissions, carbon removal accounting, and alignment with net-zero target-setting, have been ongoing. The Science Based Targets Initiative (SBTi) has developed its own guidance on top of GHG Protocol to address some gaps in net-zero accounting. The tension between measurement consistency and scientific accuracy is an ongoing challenge for the field.