According to the Intergovernmental Panel on Climate Change, aviation (domestic and international) accounts for approximately 2 per cent of global CO₂ emissions produced by human activity. In 2015, approximately 65 per cent of global aviation fuel consumption was from international aviation (see ICAO 2019 Environmental Report); applying this share to CO₂ emissions, international aviation is responsible for approximately 1.3 per cent of global CO₂ emissions.

The CORSIA has three phases: a pilot phase (2021 – 2023); a first phase (2024 – 2026); and a second phase (2027 – 2035). The difference between the phases is that the participation of States in the CORSIA offsetting in the pilot phase and in the first phase is voluntary, whereas the second phase applies to all ICAO Member States.

States that voluntarily decide to participate in CORSIA offsetting may join the scheme from the beginning of a given year, and should notify ICAO of their decision to join by June 30 of the preceding year. The figure below illustrates the different phases of CORSIA.

ICAO CORSIA Implementation Element is reflected in the ICAO document entitled "CORSIA States for Chapter 3 State Pairs" referenced in Annex 16, Volume IV.

The third edition of this ICAO document has been approved by the ICAO Council and contains the States that participate in CORSIA from 1 January 2023 and is available here:https://www.icao.int/environmental-protection/CORSIA/Pages/state-pairs.aspx

For a given year (starting in 2021), the States included in ICAO document entitled "CORSIA States for Chapter 3 State Pairs" define the State pairs subject to CO₂ offsetting requirements in CORSIA in that year.

Paragraph 10 of the Assembly Resolution A40-19 defines the coverage of the CORSIA offsetting on the basis of routes between States, with a view to minimizing market distortions between aeroplane operators on the same routes.

For this purpose, the approach is to provide equal treatment of all aeroplane operators on a given route. Specifically:

· A route is covered by the CORSIA offsetting if both States connecting the route participate in the scheme.

· A route is not covered by the CORSIA offsetting if one or both States connecting the route do not participate in the scheme.

It should be noted that the applicability of CORSIA offsetting requirements and the applicability of CORSIA monitoring, reporting and verification (MRV) requirements are not the same. Even if an international flight is not covered by the offsetting requirements, it is still covered by the MRV requirements. The figure below illustrates CORSIA’s route-based approach, and the applicability of MRV and offsetting requirements.

According to paragraph 10 of the Assembly Resolution A40-19, all international flights on the routes between States, both of which are not included in the CORSIA offsetting, are exempted from the offsetting requirements of the CORSIA, while retaining simplified reporting requirements.

The requirement to monitor, report and verify CO₂ emissions from international aviation is thus independent from the offsetting requirement.

The data reported by States will be used for the calculation of the CORSIA baseline, which is the average of 2019 and 2020 CO₂ emissions, as well as for the calculation of the aeroplane operators’ offsetting requirements, where applicable. This baseline will be revised after the decision of the 41^st ICAO Triennial Assembly.

In general, offsetting is done through the purchase and cancellation of emissions units, arising from different sources of emissions reductions achieved through mechanisms (e.g. UNFCCC’s Clean Development Mechanism), programmes (e.g. REDD+) or projects (e.g. substituting coal-fired stoves with solar cookers).

The buying and selling of eligible emissions units happens through carbon market. The price of the emissions units in the carbon market is influenced by the law of supply (availability of emissions units) and demand (level of offsetting requirements).

For CORSIA, an aeroplane operator is required to meet its offsetting requirements by cancelling CORSIA Eligible Emissions Units in a quantity equal to its total final offsetting requirements for a given compliance period. CORSIA Eligible Emissions Units are to be determined by the ICAO Council, and information on eligible units will be made available on the ICAO CORSIA website.

Paragraph 11 of the Assembly Resolution A40-19 addresses the distribution of the total amount of CO₂ emissions to be offset in a given year among individual aeroplane operators. Offsetting requirements will be calculated as follows:

a) From 2021 through 2029 a 100 per cent sectoral approach (and 0 per cent individual approach) will be applied. This applies to the pilot phase, the first phase, and the first compliance period of the second phase.

b) During the second compliance period of the second phase (2030 through 2032) at least 20 per cent of offsetting requirements would be calculated according to the “individual approach”. From 2033 to 2035, at least 70 per cent of offsetting requirements would be calculated according to the “individual approach”.

For each compliance period the State will sum up the offsetting requirements for each year within that compliance period, and the result will be the operator’s total offsetting requirement for that compliance period. The figure below describes the calculation of an aeroplane operator’s offsetting requirements.

Paragraph 15 of the Assembly Resolution A40-19 determines that CORSIA has three years compliance cycles, for which the operators need to reconcile their offsetting requirements.

The compliance periods are:

· Compliance period 1: years 2021 – 2023;

· Compliance period 2: years 2024 – 2026;

· Compliance period 3: years 2027 – 2029;

· Compliance period 4: years 2030 – 2032;

· Compliance period 5: years 2033 – 2035.

It should be noted that an operator will report its CO₂ emissions on an annual basis, corresponding to calendar years.

For the purposes of CORSIA, the sectoral baseline is defined as the average of total CO₂ emissions for the years 2019 and 2020 on the routes covered by CORSIA offsetting in a given year from 2021 onwards. This baseline will be revised after the decision of the 41^st ICAO Triennial Assembly.

From 2021 onwards, operators can reduce their CORSIA offsetting requirements by claiming emissions reductions from CORSIA Eligible Fuels.

In order to do this, the operator will:

· Use the amounts of CORSIA Eligible Fuels purchased, based on purchase records;

· Use the life-cycle emissions values to determine emissions reduction factors for each CORSIA Eligible Fuel;

· Obtain valid sustainability certification document; and

· Report and claim verified reductions of its emissions from the use of CORSIA Eligible Fuels to the State.

The State will calculate the operator’s total final offsetting requirements at the end of each compliance period by subtracting the emissions reductions from the use of CORSIA Eligible Fuels from the operator’s offsetting requirements during the compliance period.

The figure below provides an illustration of accounting the benefits from CORSIA Eligible Fuels.

Paragraph 13 of the Assembly Resolution A40-19 provides the following exemptions from the CORSIA offsetting requirements for the purposes of avoiding an administrative burden from the application of CORSIA due to low levels of international aviation activities:

1. Aeroplane operators with a low level of annual emissions from their international aviation operations (less than 10 000 metric tonnes of CO₂ emissions per year);

2. Aircraft with less than 5.700 kg of Maximum Take-Off Mass (MTOM);

3. Humanitarian, medical and firefighting operations.

In addition to being exempted from CORSIA offsetting requirements, these activities are also exempted from CORSIA MRV requirements.

Paragraph 12 of the Assembly Resolution A40-19 refers to “new entrants” as aeroplane operators that commence an aviation activity falling within the scope of the CORSIA. This paragraph outlines criteria to determine when “new entrants” should start participating in the CORSIA offsetting, with the exemption period being the earliest out of the following two:

· Three years from commencing aviation activities within the scope of CORSIA; or

· The year in which new entrant’s annual emissions exceed 0.1 per cent of total emissions in 2020.

It is important to note that the CO₂ emissions of a new entrant are still to be reported from the year after the new entrant falls under the applicability of CORSIA MRV requirements (also see question 3.19), regardless of the exemptions from the CORSIA offsetting requirements.

Reference in Annex 16, Volume IV: Part II, Chapter 2. CORSIA’s MRV (Monitoring, Reporting and Verification) system consists of three components:

• Monitoring of CO₂ emissions is either based on a Fuel Use Monitoring Method, or the on use of the ICAO CORSIA CERT.

For the former, each operator has to collect accurate information on the fuel use per each flight and calculate CO₂ emissions by multiplying the amount of fuel used with a conversion factor representing the amount of tonnes of CO₂ produced from using one tonne of fuel.

An aeroplane operator is required to describe its approach to CO₂ emissions monitoring in an Emissions Monitoring Plan, which the operator will submit for approval by the State.

• After monitoring and calculating CO₂ emissions, the necessary information will be reported from aeroplane operators to their State Authority, and from States to ICAO, by using harmonised templates and procedures. ICAO consolidates the CO₂ emissions data, calculates the annual Sectoral Growth Factor, and communicates the Growth Factor to States.

•  Verification of CO₂ emissions information is to ensure that the data is accurate and free of errors. A very basic idea of verification is that a third-party checks that everything has been done correctly. This is similar to the accounting practices that are performed in the financial world

Are there any exemptions? Reference in Annex 16, Volume IV: Part II, Chapter 2, 2.1. All aeroplane operators conducting international flights are required to monitor, report and verify CO₂ emissions from these flights from 1 January 2019 until 31 December 2035. It should be noted that the requirement for the MRV of CO2 emissions is independent from participation in CORSIA offsetting.

As per Annex 16, Volume IV, the MRV requirements do not apply to:

· An aeroplane operator that produces annual CO₂ emissions from international flights less than or equal to 10 000 tonnes

· Aeroplane(s) with a maximum certificated take-off mass less than or equal to 5.700 kg

· Humanitarian, medical and firefighting flights, as well as flights preceding or following a humanitarian, medical or firefighting flight, provided that such flights were conducted with the same aeroplane, and were required to accomplish the related humanitarian, medical or firefighting activities or to reposition thereafter the aeroplane for its next activity.

Reference in Annex 16, Volume IV: Part II, Chapter 2, 2.2.2 and Appendix 4. An aeroplane operator falling under the applicability of CORSIA MRV requirements is required to submit an Emissions Monitoring Plan to the State Authority for approval.

An Emissions Monitoring Plan is a collaborative tool between the State and the aeroplane operator that identifies the most appropriate means and methods for CO₂ emissions monitoring on an operator-specific basis, and also facilitates the reporting of required information to the State.

An Emissions Monitoring Plan has four main components:

· Aeroplane operator identification;

· Fleet and operations data;

· Methods and means of calculating emissions from international flights; and

· Data management, data flow and control.

Full contents of an Emissions Monitoring Plan are included in Annex 16, Volume IV, Appendix 4.

The ICAO CORSIA CERT will have different versions over time. The 2018 version of the ICAO CORSIA CERT allows operators to estimate their CO₂ emissions from international flights and assess their eligibility or not of using the ICAO CORSIA CERT as a simplified monitoring method.

2019 version of the ICAO CORSIA CERT includes a functionality to not only estimate CO₂ emissions, but also to generate aeroplane operator’s annual Emissions Report. Regarding the estimation of the CO₂ emissions, the 2019 version of the tool allows either estimating CO₂ emissions based on either Great Circle Distance, or on Block Time input.

From 2021 onwards, the ICAO CORSIA CERT will be updated by including a list of States Pairs subject to CORSIA offsetting requirement for each year.

Τhe ICAO CORSIA CERT is available for download here: (https://www.icao.int/environmental-protection/CORSIA/Pages/CERT.aspx)

Reference in Annex 16, Volume IV: Part II, Chapter 2, 2.2.3. After an aeroplane has monitored its fuel use, the operator is required to determine the CO2 emissions by using the following equation:

CO2 Emissions = Mass of fuel × Fuel Conversion Factor of given fuel type

Fuel conversion factors are:

· 3.16 kg CO₂/kg of fuel for Jet-A and Jet-A1 fuel; and

· 3.10 kg CO₂/kg fuel for AvGas or Jet-B fuel.

If an aeroplane operator is using the ICAO CORSIA CERT for CO2 emissions monitoring, the tool automatically estimates the CO₂ emissions, and no separate calculation of emissions is needed.

The CCR is one of the five implementation elements of CORSIA. It is an information management system that will allow States to submit CORSIA-related data and information to ICAO in a standardized format.

Using the CCR, the ICAO Secretariat will store the submitted information, perform calculations, develop the necessary reports for CORSIA, and make available the required information for transparency.

Verification on emissions data intends to ensure the consistency of information, and to identify any potential errors in the aeroplane operator’s annual Emissions Report.

CORSIA foresees a three-step verification pathway:

· At Step 1, a voluntary internal pre-verification by an aeroplane operator is recommended. This means that the aeroplane operator conducts a verification of its data before submitting it to a third-party verification body. The internal pre-verification is likely to increase the quality of the Emissions Report, but it does not replace the requirement for third-party verification.

· At Step 2, a third-party verification is performed by an independent thirdparty verification body, before the operator reports to the State Authority. The requirements for the third-party verification will be based on existing Standards from the International Organization for Standardization (ISO), as well as on CORSIA-specific requirements from Annex 16, Volume IV. A third-party verification body is contracted by an aeroplane operator.

· At Step 3, the State Authority conducts an order of magnitude review. This is the check performed by a State to verify the data against different sources of information that the State has access to.

The ICAO Assistance, Capacity building and Training programme on CORSIA (ACT CORSIA) is aimed at supporting Member States to implement CORSIA’s monitoring, reporting and verification (MRV) requirements as per Annex 16, Volume IV.

ACT-CORSIA, which was officially launched during the ICAO Seminar on CORSIA. It is designed to harmonize and bring together all relevant actions, promoting coherence to CORSIA capacity building efforts, and includes a number of activities and products, namely: CORSIA buddy partnerships; model regulations; frequently asked questions (FAQs); brochures and leaflets; videos; seminars and related materials; online tutorials; and other background information.

All information on ACT-CORSIA is accessible through the ICAO CORSIA website.