IMSML Web Article 14/2026: Resolution MEPC.400(83) - Amendments to the 2021 Guidelines on the Operational Carbon Intensity Reduction Factor Relative to Reference Lines (CII Reduction Factors Guidelines, G3)(Originally in Resolution MEPC.338/76)

The amendments to the 2021 Guidelines are found in the Annex. The amendments were made during the Marine Environment Protection Committee (MEPC) at its 83rd meeting. The amendments were necessary as Regulation 28.5 of MARPOL Annex VI required CII Reduction (Z) factors to be established for each ship type that fall under Regulation 28. Note that the 2021 Guidelines can be traced back to Resolution MEPC.338(76) which did not defined Z factors, although designating its application for the years 2027 to 2030. At the 83rd meeting of the MEPC, it was time to review the CII regulations as Regulation 28.11 of MARPOL Annex VI requires that the International Maritime Organisation (IMO) should complete a review by 1 January 2026. CII Factors are IMO’s Carbon Intensity Factors which function to measure a ship’s operational carbon emissions relative to cargo capacity and distance travelled.

In Malaysia, the amendments were introduced via Malaysian Shipping Notice (MSN) 06/2025 which contained all the Resolutions Adopted by the 83rd Session of the Marine Environment Protection Committee (MEPC 83). MSN 06/2025 was issued by the Director of MArine on 9 October 2025.

What are the Reduction Factors for the required annual operational CII of ship types?

There is a new table introduced in Annex 4 for the Reduction Factors which function (Z%) for the CII relative to the 2019 reference line. There is a steady increase of percentages, which start at 5% in 2023, rising to 11% in 2026 and then peaking at 21.500% by 2030.

What is the Work Plan for Phase 2 of the Review of the Short-Term GHG Reduction Measure?

Annex 5 contains various stages of review starting from Spring 2026, to Autumn 2026 and Spring 2027, all the way to Spring 2028.

What is planned for Spring 2026?

Scheduled for further consideration and finalisation of the development of enhanced SEEMP framework at MEPC 84. The 84th session of MEPC is currently planned for 27 April to 1 May 2026. There is planned inter-sessional and correspondence groups.

Note, that SEEMP is IMO’s Ship Energy Efficiency Management Plan which is a mandatory operation mechanism Under Annex IV of MARPOL. It functions to improve ship energy efficiency, lower greenhouse emissions and reduce fuel costs.

MEPC 84 will also further consider and finalize the development of the cgHRS metric for cruise passenger ships.

Note, cgHRS is the Carbon Intensity per Gross Tonnage and Hours. It is a specialised matrix for the calculation of emission from cruise ships. The metric is defined as total carbon dioxide emissions, divided by the cruise vessel’s gross tonnage and its operational hours. The focus of the metric is on operational hours, instead of distance-based which is used for cargo vessels. It is part of an initiative to amend IMO’s Carbon Intensity Indicator (CII) regulations. The current method of measurement penalises cruise ships for short voyages and long berths in ports where engines are still running to power the requirements of onboard hotels and/or entertainment.

Other planned objectives for MEPC 84 (see Annex 5) include:

[1] Consider proposals to ensure synergies between the IMO carbon intensity/energy efficiency framework and the IMO net-zero framework (e.g. energy-based approach) with a view to finalization as soon as possible;

[2] Pursue incentives for energy efficiency and for the adoption of better operational practices in the shipping value chain or other technologies to reduce emissions from ships in line with the 2023 IMO GHG Strategy.

What is planned for Autumn 2028?

MEPC 85 is scheduled for 23-27 November 2026, and will further consider the development of other CII metrics. Additional proposal under consideration include the following:

[1] Proposals to ensure synergies between the IMO carbon intensity/energy efficiency framework and the IMO net-zero framework (e.g. energy-based approach) with a view to finalization as soon as possible;

What is planned for Spring 2027?

At MEPC 86 there are plans to consider the development of other CII metrics, and additional concrete proposals for CII correction factors, as well as reference line adjustments (if any). Further considerations that will be made include the following:

What has been planned for Spring 2028?

MEPC 87 will conclude the consideration of other CII metrics, as well as finalising the development or revised reference lines. There will also be further considerations of further concrete proposals for CII correction factors and/or reference lines adjustments (as appropriate). A big part of MEPC 87 will also be the finalising of PHASE 2 of the Review. Further considerations at MEPC 87 will also include the following:

[1] Proposals to ensure synergies between the IMO carbon intensity/energy efficiency framework and the IMO net-zero framework, with a view to finalization as soon as possible, and develop a possible way forward for the IMO carbon intensity/energy efficiency framework beyond 2030, as appropriate;

Thank you for reading IMSML Web Article 14/2026

Stay tuned for the next IMSML Web Article 15/2026: Resolution MEPC.401(83) - Amendments to the 2024 Guidelines for the Development of a Ship Energy Efficiency Management Plan (SEEMP0 Originally Made Under Resolution MEPC.395(82).

Signing-off for today,

Dr Irwin Ooi Ui Joo, LL.B(Hons.)(Glamorgan); LL.M (Cardiff); Ph.D (Cardiff); CMILT

Professor of Maritime and Transport Law

Faculty of Law

Universiti Teknologi MARA Shah Alam

Selangor, Malaysia

Tuesday, 7 April 2026

Note that I am the corresponding author for the IMSML Website Articles. My official email address is: uijoo310@uitm.edu.my