The Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) is the first sector-wide, market-based climate mechanism adopted at the global level. It was agreed at the 39th Assembly of the International Civil Aviation Organization (ICAO) in October 2016 and is designed to address CO2 emissions from international civil aviation, a sector excluded from the Kyoto Protocol's binding targets and largely outside the scope of national pledges under the Paris Agreement.
Under CORSIA, airlines operating international flights between participating states must monitor, report, and verify (MRV) their CO2 emissions, and purchase eligible emissions units ("offsets") to compensate for growth in emissions above an established baseline. Originally the baseline was set as the average of 2019 and 2020 emissions, but in 2020 the ICAO Council adjusted the baseline to 2019-only levels to prevent the COVID-19 collapse in air travel from making the scheme unduly stringent.
The scheme runs in phases:
- A pilot phase (2021–2023) and first phase (2024–2026), both voluntary, in which roughly 120+ states have indicated participation.
- A mandatory phase from 2027, covering all ICAO member states except those exempted (least developed countries, small island developing states, landlocked developing countries, and states with very small shares of international aviation activity).
Eligible offset credits are screened by ICAO's Technical Advisory Body; in the pilot phase, credits from programs such as the American Carbon Registry, Climate Action Reserve, and the Architecture for REDD+ Transactions (ART) were approved, with restrictions on vintage. Sustainable aviation fuels (SAF) and lower-carbon aviation fuels can also reduce an operator's offsetting obligation.
Critics, including the International Council on Clean Transportation and several NGOs, argue CORSIA's offsetting approach does not deliver absolute emissions cuts and risks reliance on low-integrity credits. Supporters counter that it is the only operational global cap on aviation emissions growth and complements ICAO's 2022 long-term aspirational goal of net-zero international aviation CO2 by 2050.
Example
In 2023, major carriers including Lufthansa and IAG reported their international CO2 emissions under CORSIA's pilot phase and began purchasing eligible offset credits to cover growth above the 2019 baseline.
Frequently asked questions
Participation is voluntary during the pilot phase (2021–2023) and first phase (2024–2026), and becomes mandatory from 2027 for most ICAO member states, with exemptions for least developed countries, small island developing states, and landlocked developing countries.
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