Carbon Glossary

The principle that carbon removal or emissions reductions would not have occurred without the incentive of carbon finance. Essential for ensuring carbon credits represent real climate benefits.

Afforestation plants trees on land that has not carried forest in recent history; reforestation restores tree cover on land that was forested and has since been cleared. Both remove CO₂ from the atmosphere as the trees grow.

The section of the Paris Agreement governing how countries cooperate on emissions reductions, including transferring them internationally. It sets the rules for authorisation, corresponding adjustments, and a UN supervised crediting mechanism.

The reference scenario describing what emissions or carbon storage would have been without the project. Credits are issued for the difference between the baseline and what the project actually achieved.

Independent risk assessment of carbon projects using satellite data and AI analysis. Provides ratings from AAA to D based on additionality, permanence, and overestimation risks.

Stable carbon created through pyrolysis of organic materials. Provides long-term carbon storage while improving soil fertility and agricultural productivity.

Carbon stored by coastal and marine ecosystems such as mangroves, seagrass meadows, and salt marshes. These habitats hold carbon in waterlogged soils as well as in living biomass.

Reserve of carbon credits set aside to cover potential reversals or overestimation in carbon projects. Provides insurance against project risks and uncertainties.

Carbon neutral usually means balancing measured emissions with an equivalent volume of carbon credits. Net zero means cutting emissions deeply in line with climate science first, then neutralising only the small remaining residual with durable carbon removal.

A widely used but imprecise term for a carbon credit applied against emissions elsewhere. Carbon Compared prefers carbon removal or carbon avoidance, because the two describe very different climate outcomes.

Database system that tracks the ownership and transfer of carbon credits to prevent double counting. Examples include Verra, Gold Standard, and American Carbon Registry.

Additional environmental and social benefits beyond carbon removal, such as biodiversity conservation, water quality improvement, or local economic development.

A market where regulated entities must surrender allowances or approved carbon units to meet legally binding emissions limits. Examples include the EU Emissions Trading System, the UK ETS, and China's national carbon market.

A set of ten benchmark criteria for carbon credit integrity published by the Integrity Council for the Voluntary Carbon Market (ICVCM). Credits produced under a methodology that passes assessment can carry the CCP label.

An accounting entry in which the country hosting a project adds the emissions reduction back to its own national inventory, so a buyer abroad can claim it instead. Required under Article 6 of the Paris Agreement for authorised international transfers.

The Carbon Offsetting and Reduction Scheme for International Aviation, run by ICAO, under which airlines cancel eligible carbon credits against growth in international flight emissions. Only units from ICAO approved programmes qualify.

The fixed span of time during which a project may generate credits under its approved methodology. Lengths vary by verification standard and project type, and periods are often renewable with the baseline reassessed at renewal.

Technology that uses specialized machines to capture CO₂ directly from ambient air. Often combined with permanent geological storage for high-permanence carbon removal.

When the same tonne of emissions reduction is claimed more than once, whether by two buyers, by two registries, or by a buyer and the host country. Serial numbers, single-registry issuance, and corresponding adjustments exist to prevent it.

Process that accelerates natural rock weathering to capture CO₂ from the atmosphere. Creates permanent carbon storage through mineral carbonation reactions.

Ex-post credits are issued after the reduction or removal has occurred and been verified. Ex-ante credits are sold in advance, based on outcomes a project expects to deliver in future.

Funding emissions reductions or removals inside your own supply chain rather than buying credits from an unrelated project. The benefit is accounted for as a scope 3 reduction instead of as an offset.

The point at which a registry creates carbon credits in a project's account following verification, each carrying a unique serial number. Only issued credits can be transferred or retired.

When carbon removal activities in one area lead to increased emissions elsewhere. Must be accounted for in project design and carbon accounting methodologies.

The approved rulebook a project must follow to quantify its emissions reductions or removals. Each verification standard maintains its own methodologies, covering baseline setting, monitoring, and how credits are calculated.

System for measuring, reporting, and independently verifying carbon removal or emissions reductions. Critical for ensuring project integrity and transparency.

The duration that removed CO₂ remains stored and unavailable to return to the atmosphere. Ranges from decades to millennia depending on the storage method and technology used.

Forward or pre-purchase agreements for credits that have been (a) verified but not yet issued, or (b) expected in the future based on projected project performance. Delivery and retirement happens later, once the registry issues the credits

The project has been designed and documented but has not yet been validated by a third-party auditor

The project's design has already been validated. The project is operational, and is now preparing for the verification audit

A third-party auditor has confirmed the reported emission reductions/removals for a specific monitoring period

Projects that protect standing forests facing a demonstrable threat of clearing or degradation. These are avoidance credits: they prevent emissions rather than removing CO₂ already in the atmosphere.

Permanently cancelling a carbon credit in a registry so that it cannot be sold or used again. Retirement is the step that allows the holder to make a claim against their emissions.

The body that validates corporate emissions reduction targets against climate science. Its Corporate Net-Zero Standard sets out how companies should cut their own emissions and how carbon credits may and may not be used.

The three categories the GHG Protocol uses to organise a company's emissions: direct emissions from owned or controlled sources (scope 1), purchased energy (scope 2), and everything else across the value chain (scope 3). Scope 3 is usually the largest and the hardest to measure.

Carbon credits that have already been issued and are sitting in a registry account, ready for transfer immediately

The standard unit of the carbon market: one metric tonne of carbon dioxide, or the amount of another greenhouse gas with an equivalent warming effect. One carbon credit represents one tCO₂e.

The accredited independent auditor that checks a project against its methodology, first at design stage (validation) and later against actual performance (verification). VVBs are accredited independently and approved by the programme they audit under.

The year when carbon removal or emissions reduction occurred. Important for pricing and compliance as more recent vintages often have higher value and acceptance.

The market where companies and individuals buy carbon credits by choice rather than legal obligation. Projects are certified against independent verification standards such as Verra, Gold Standard, and Puro.earth.