ICAO releases first-ever growth factor for airlines’ CORSIA offsetting requirements

ICAO has confirmed governments participating in its CORSIA scheme will shortly be informing airlines of their first-ever carbon offsetting requirements under the international agreement. The emissions data collected or estimated from 138 member states was used to calculate the global growth of emissions from international civil aviation for 2024, the start year of the voluntary First Phase of the scheme, against a baseline of 85% of total 2019 CO2 emissions. By applying the Sector’s Growth Factor for 2024, which has just been released, to emissions data submitted by each airline, governments can calculate the amount of CO2 each airline needs to offset through the purchase of CORSIA Eligible Emission Units (EEUs). In other CORSIA news, following earlier recognition by ICAO under the Pilot and First Phase, Gold Standard and Verra have been approved to supply credits for its Second Phase (2027-2029). ICAO has also approved Isometric to issue its verified carbon removal credits to airlines under CORSIA.

The primary objective of CORSIA is to maintain carbon neutral growth of international aviation – so excluding domestic aviation – and airlines with flights between participating countries, called State pairs, are required to offset emissions that exceed a baseline determined under ICAO Assembly Resolution A42-22.

According to ICAO, the baseline of 85% of total 2019 CO2 emissions for all State pairs subject to offsetting requirements in 2024 was set at 305,522,071 tonnes. The total 2024 emissions for all applicable State pairs, as reported by 126 States and estimated for 12 more, amounted to 361,159,641. This has resulted in the 2024 Sector’s Growth Factor being calculated as 0.15405257.

Information on emissions and other data submitted by Member States through the CORSIA Central Registry (CCR), along with CORSIA documentation, is published on the ICAO website.

“This open sharing of data supports accountability and offers all stakeholders a clear view of collective progress for the robust implementation of the scheme,” says ICAO. “We and our Member States will continue to provide regulatory frameworks, capacity building and technical support to ensure effective implementation and continuous improvement of the scheme.”

Meanwhile, Gold Standard has been approved by ICAO to supply eligible emission units for CORSIA’s Second Phase, covering the period 2027 to 2029. The organisation says this follows several key steps it has taken in recent months to facilitate the supply of CORSIA-eligible credits, including the approval of three insurance policies to manage double-counting risk and the first labelling of credits as eligible for the First Phase.

In its decision, ICAO has maintained existing eligibility restrictions for Gold Standard credits under CORSIA’s First Phase and added new restrictions related to the calculation of the fraction of non-renewable biomass (fNRB) and project baselines, a crucial metric in carbon offsets relating to cookstove projects.

“These updates are consistent with Gold Standard’s recent revisions to align fNRB calculations and methodologies with the Paris Agreement framework,” the Swiss-based non-profit reports. “This alignment reinforces the importance of these updates in ensuring access for Gold Standard project developers to compliance markets.”

Commented Gold Standard CEO Margaret Kim: “Access to markets is essential for accelerating climate action. With this approval, Gold Standard project developers can have greater confidence that their high-integrity credits will meet growing compliance demand. Our role is to help developers of all sizes turn ambition into measurable, science-based impact providing the trusted frameworks and tools they need to bring projects to market efficiently and credibly.”

ICAO has also approved Verra’s Verified Carbon Standard (VCS) Program to supply EEUs for use in CORSIA’s Second Phase and confirms the continued eligibility of Verified Carbon Units under CORSIA.

“This approval validates the work of our team and partners around the world who continue to raise the bar for climate finance and environmental integrity,” said Mandy Rambharos, CEO of Verra. “We remain committed to aligning with international frameworks and evolving in step with the needs of the global climate challenge.”

Following ICAO approval, airlines can now also use carbon removal credits verified by Isometric to unlock additional supply for CORSIA, says the carbon removal registry.

“This marks another step in the wider shift from low-quality offsets towards high-quality, verifiable carbon removal,” said Lukas May, Chief Commercial Officer for Isometric. “Approval under the scheme’s First Phase follows a comprehensive evaluation conducted by ICAO, which found Isometric met its standards for transparency, scientific rigor and environmental integrity.”

Carrie Harris, Director of Sustainability at British Airways, one of the airline industry’s biggest purchasers of carbon removals, commented: “Expanding the global carbon removals is essential for aviation to achieve net zero emissions. ICAO’s recognition of Isometric for CORSIA compliance is a significant step, providing a credible pathway towards setting a long-term net zero goal.

“This move also creates a strong demand signal for carbon removal project developers and supports airlines in meeting their CORSIA obligations with credible carbon removals.”

The airline says that by 2050, around one-third of its total emissions reductions are expected to come from carbon removals.

Airline industry body IATA reports the cost of compliance with the ICAO CORSIA carbon offsetting scheme is anticipated to grow to $1.7 billion for 2026, up from $1.3 billion for 2025.

In CORSIA’s First Phase (2024-26), IATA expects airlines to purchase upwards of 200 million EEUs for cancellation and compliance by late 2027, costing an estimated $4-5 billion, and increasing to nearly 2 billion EEUs through to 2035.

Christopher Surgenor
Editor