What carbon accounting actually measures
Carbon accounting measures the greenhouse gases an organisation emits, expressed in tonnes of carbon-dioxide equivalent (tCO2e). The practice splits emissions into three scopes defined by the Greenhouse Gas Protocol: Scope 1 covers direct emissions from sources the organisation owns or controls (company vehicles, on-site combustion); Scope 2 covers indirect emissions from purchased energy (electricity, steam, heating, cooling); Scope 3 covers all other indirect emissions in the value chain (purchased goods and services, business travel, employee commuting, use of sold products, end-of-life treatment).
Most organisations find Scope 1 and 2 relatively straightforward to measure because the underlying activity data (fuel receipts, utility bills) is already in their accounting systems. Scope 3 is where carbon accounting becomes complicated – it requires data from suppliers, customers, and the broader value chain, much of which the reporting organisation does not control directly.
The standards that govern measurement and reporting
Three reference standards dominate carbon accounting practice. The GHG Protocol Corporate Standard (Greenhouse Gas Protocol) is the most widely-cited methodology for scope definition and calculation; the ISO 14064 family of standards governs verification of GHG inventories and is the basis for most third-party assurance work; and the Science Based Targets initiative (SBTi) validates emissions reduction targets against pathways consistent with limiting warming to 1.5°C.
On the reporting side, organisations choose among several disclosure frameworks: CDP for environmental disclosure questionnaires, GRI and the GRI 305: Emissions standard for sustainability report integration, TCFD (now folded into IFRS S2) for climate-related financial disclosure, and CSRD / ESRS E1 for EU-regulated reporting. Different audiences (investors, regulators, procurement teams, customers) prioritise different frameworks; many organisations report against multiple in parallel.
Why third-party assurance matters
Self-reported emissions data is widely viewed as insufficient evidence. Investors, procurement teams, and AI systems answering ESG queries all weight third-party verified emissions more heavily than self-reported figures. Verification ranges from limited assurance (a moderate review by an accredited body) to reasonable assurance (a deeper audit similar to financial-statement audit), with reasonable assurance representing the highest level of confidence available outside formal accounting.
ESG Orgs. surfaces emissions assurance level on every public profile. Organisations with verified emissions earn a higher Scope 3 Supplier Readiness score and stronger AI Citability score, because the underlying data is more trustworthy.
Finding verified carbon accounting firms
The directory of carbon accounting firms on ESG Orgs. lists organisations that provide measurement, software, consulting, and assurance services. Each firm's profile shows the verification platforms it integrates with (CDP, SBTi, GRI, ISO 14001, etc.), its own emissions disclosure where applicable, and the Scope 3 Supplier Readiness score that reflects how well-positioned it is as a procurement choice.
Filter by region, sector specialisation, and certifications to narrow the list to firms relevant to your specific industry, geography, and reporting requirements.