CORSIA Glossary: Every Term Defined

The requirement that an emission reduction would not have occurred without the revenue from selling carbon credits. If the activity was already profitable, already legally required, or already common practice, it is not additional. The most contested criterion in the carbon market. See the emissions unit criteria.

The entity operating a flight, generally identified by its Air Operator Certificate and ICAO designator. The party with CORSIA obligations. Not necessarily the aircraft owner or the marketing carrier on a code share.

The volume of Annex 16 to the Chicago Convention containing the CORSIA Standards and Recommended Practices. The technical source of truth for monitoring, reporting and verification requirements.

The report an operator submits each year covering CO2 emissions from international flights in the preceding calendar year. Must be independently verified.

The Paris Agreement article governing cooperative approaches and international transfer of mitigation outcomes. Article 6.2 covers bilateral cooperative approaches; Article 6.4 establishes a centralised crediting mechanism. The source of the corresponding adjustment requirement.

The sector-wide reference emissions level against which growth is measured. Originally the 2019-2020 average; reset by the ICAO Council to 2019 alone after the pandemic traffic collapse.

Distinct from the CORSIA baseline. The scenario describing what emissions would have occurred without a carbon project, against which its reductions are measured.

Moments when an aircraft leaves and arrives at its parking position. Several fuel monitoring methods use tank readings taken at these points. See fuel monitoring methods.

A reserve of credits held back by a crediting programme to cover reversals in storage-based projects — a forest fire, for example. The main mechanism addressing permanence risk.

The Committee on Aviation Environmental Protection, ICAO's technical committee. Develops standards and recommends to the Council. See CORSIA governance.

Permanently removing a unit from circulation in a registry, designated for CORSIA compliance. This, not purchase, discharges an offsetting obligation. Irreversible. See registries and cancellation.

The ICAO CO2 Estimation and Reporting Tool. Estimates emissions from flight data without full fuel monitoring. Available to small emitters and for filling data gaps.

Documentation tracking a sustainability attribute from fuel producer to aircraft uplift. Required for any CORSIA Eligible Fuels claim.

The 1944 Convention on International Civil Aviation establishing ICAO. Its Annexes carry international aviation standards, including Annex 16 Volume IV.

A three-year block over which offsetting requirements accumulate and are settled by cancelling units. See compliance periods and deadlines.

A carbon credit that may be used for CORSIA compliance — from an ICAO-approved programme, in an eligible vintage, with a host-State corresponding adjustment, meeting all the Emissions Unit Criteria. See EEUs.

Sustainable aviation fuel or lower carbon aviation fuel meeting the CORSIA sustainability criteria, certified under an approved scheme, with documented chain of custody. Reduces the offsetting requirement. See CORSIA Eligible Fuels.

The accounting entry by which a host State adds authorised transferred tonnes back into its own national inventory, so the same reduction is not claimed twice. The binding constraint on CORSIA supply. See corresponding adjustments.

Emissions on route pairs where both origin and destination States participate in CORSIA. The base to which the growth factor applies. Smaller than total international emissions.

A standards body that publishes methodologies, registers projects, oversees verification and operates a registry. ICAO approves programmes, not individual projects. See approved crediting programmes.

The government body authorised to grant Article 6 authorisations and corresponding adjustments in a host State. Where none exists, CORSIA supply from that country is effectively impossible.

The Directorate General of Civil Aviation, India's national authority for CORSIA. See CORSIA in India.

Claiming the same emission reduction more than once. Takes three forms: double issuance, double use, and double claiming. The last is the hard one, remedied by corresponding adjustments.

The document describing how an operator will monitor and report emissions. Must be approved by the national authority before monitoring begins. See the EMP.

ICAO's criteria defining what makes a carbon credit usable for CORSIA. Eight requirements, all of which must hold. See the emissions unit criteria.

The report filed with the national authority identifying units cancelled against an offsetting obligation. Closes the compliance loop.

The proportion of covered emissions that must be offset. Sectoral growth factor measures growth across the whole covered sector; individual growth factor measures an operator's own growth and gains weight from 2030. See baseline and growth factors.

The International Civil Aviation Organization, a UN specialised agency. Administers CORSIA but cannot enforce directly against operators.

Induced Land Use Change. Emissions caused when fuel feedstock production displaces other land use. Added to lifecycle emissions when assessing CORSIA Eligible Fuels.

An operator's own emissions growth relative to the baseline. Enters the obligation calculation from 2030 at 15% weight, rising to 30% from 2033.

Internationally Transferred Mitigation Outcome. The Article 6.2 term for an authorised, corresponding-adjusted mitigation outcome transferred between parties.

Lower Carbon Aviation Fuel. A fossil-based aviation fuel with lower lifecycle carbon intensity than the conventional baseline, for example through refinery carbon capture.

Well-to-wake emissions covering feedstock production, transport, conversion, distribution and combustion. The basis for assessing CORSIA Eligible Fuels, not combustion emissions alone.

A chain-of-custody model allowing physical commingling of sustainable and conventional fuel while tracking the sustainability attribute, requiring quantities to balance over a defined period.

The threshold above which a misstatement in an emissions report matters. Set relative to reported emissions, tighter for larger emitters.

Monitoring, Reporting and Verification. The annual cycle every in-scope operator runs, whether or not offsets are owed. See CORSIA MRV explained.

Maximum certificated Take-Off Mass. CORSIA applies to aeroplanes above 5,700 kg MTOM.

Nationally Determined Contribution. A country's climate target under the Paris Agreement. Authorising a corresponding adjustment makes an NDC harder to meet, which is why governments hesitate.

The criterion requiring a project not to contravene host-State law or cause social or environmental harm. Land tenure disputes are the most common failure.

The tonnes of CO2 an operator must offset, calculated as covered emissions × growth factor, less any CORSIA Eligible Fuels reduction. See the calculation.

The requirement that a reduction is not reversible, or that reversal risk is addressed through a buffer pool or equivalent. Straightforward for avoided emissions, difficult for stored carbon.

A structure allowing multiple similar small activities to register under one umbrella with a shared methodology, making otherwise uneconomic projects viable through aggregation.

A system holding serialised carbon units and recording issuance, transfer and cancellation. Operated by crediting programmes — there is no single CORSIA registry.

An origin and destination State combination. An offsetting obligation arises only where both participate in CORSIA.

Sustainable Aviation Fuel. Renewable or waste-derived aviation fuel. Qualifies as a CORSIA Eligible Fuel if it meets the sustainability criteria and is properly certified and documented.

Standards and Recommended Practices. The instruments in ICAO Annexes; Standards are binding on Member States, Recommended Practices are advisory.

Growth in covered emissions across the whole sector relative to the 2019 baseline. The sole basis for obligations through 2029. Means an operator whose own emissions fell can still owe offsets.

Unique identification of each carbon unit, encoding programme, project, vintage and batch position. Prevents double use and establishes chain of custody.

The State that issued the operator's Air Operator Certificate, and therefore the State whose authority administers CORSIA for that operator.

A scheme ICAO has approved to certify CORSIA Eligible Fuels against the sustainability criteria.

Technical Advisory Body. The independent expert group assessing crediting programmes against the Emissions Unit Criteria and recommending to the ICAO Council.

An accredited independent organisation that verifies an operator's Annual Emissions Report. Must be independent of any party that advised on the report.

The monitoring period during which a reduction physically occurred. Not the issuance date. Must fall within an eligible window for the relevant compliance period. See vintages and eligibility windows.