IMO GHG Strategy

Background and history

Climate change at the IMO before 2003

The first sustained engagement by the IMO with climate change came in 1997, the year of the Annex VI Protocol and the year that the United Nations Framework Convention on Climate Change (UNFCCC) adopted the Kyoto Protocol. Article 2.2 of the Kyoto Protocol assigned responsibility for the limitation or reduction of greenhouse gas emissions from “marine bunker fuels” to the International Maritime Organization, with developed-country Parties to the UNFCCC obliged to “pursue limitation or reduction” through the IMO. The same provision assigned aviation bunkers to the International Civil Aviation Organization (ICAO).

The 1997 Annex VI Protocol Conference adopted Resolution 8 inviting MEPC to “consider what CO₂ reduction strategies might be feasible in light of the relationship between CO₂ and other atmospheric and marine pollutants”. MEPC 42 in November 1998 considered the first paper on the subject and commissioned a study from the Chalmers University of Technology in Gothenburg, Sweden, in cooperation with the Marintek research institute in Trondheim, Norway. The Marintek study was delivered in 2000 and quantified, for the first time, the total CO₂ emissions of international shipping at approximately 419 million tonnes per year (Mt CO₂/yr), or approximately 1.8% of global anthropogenic CO₂. The study became the empirical foundation for all subsequent IMO climate work.

Assembly Resolution A.963(23) of 2003

The IMO Assembly at its 23rd session in December 2003 adopted Resolution A.963(23) on IMO Policies and Practices Related to the Reduction of Greenhouse Gas Emissions from Ships, formally launching the IMO’s climate work programme. The resolution requested MEPC to identify and develop the mechanism or mechanisms needed to achieve limitation or reduction of GHG emissions from international shipping. The MEPC was given a “soft” mandate, with no binding emission target and no entry-into-force deadline; the resolution acknowledged the difficulty of allocating emissions from a globally mobile fleet to specific national jurisdictions and the consequent unsuitability of the bunker-fuel emissions for inclusion in nationally-determined climate reduction commitments.

Between 2003 and 2009 MEPC discussed candidate emission reduction measures in seven biannual sessions. The discussions focused on three broad approaches: technical measures (engine and ship-design improvements), operational measures (slow steaming, route optimisation, weather routing) and market-based measures (a global emissions trading system or a global bunker levy). Progress was slow because of fundamental disagreement between developed and developing-country members about the principle of common but differentiated responsibilities (CBDR), inherited from the UNFCCC framework, and how it could be reconciled with the IMO principle of equal treatment of all flag states.

Second IMO GHG Study 2009 and the Vision Statement

The Second IMO GHG Study, prepared by Marintek, MIT and the Indian Ship Research Institute and adopted by MEPC 59 in July 2009, updated the 2000 figures to a baseline year of 2007. The study estimated total CO₂ emissions of international shipping at 870 Mt CO₂/yr in 2007, or approximately 2.7% of global anthropogenic CO₂; total emissions including domestic shipping and military operations were estimated at 1,046 Mt CO₂/yr. The study also projected business-as-usual emissions to 2050, with a central scenario of 2,772 Mt CO₂/yr, an increase of 218% over 2007. The figures provided the empirical basis for MEPC 59’s adoption of a “Vision Statement” calling for substantial reductions in absolute emissions and for the development of a comprehensive package of technical, operational and market-based measures.

Third IMO GHG Study 2014 and the EEDI / SEEMP foundation

The Third IMO GHG Study, prepared by a consortium led by University College London and CE Delft and adopted by MEPC 67 in October 2014, updated the figures for the period 2007 to 2012. The study found that international shipping CO₂ emissions had peaked at 921 Mt CO₂/yr in 2008 (driven by the pre-financial-crisis trade boom) and declined to 796 Mt CO₂/yr in 2012, partly because of the financial-crisis-driven reduction in trade and partly because of slow steaming by ship operators responding to high bunker prices. The 2008 figure became the 2008 baseline against which all subsequent IMO emission reduction targets are measured.

The 2014 study was completed against the background of the recently-adopted EEDI and SEEMP regulations under MARPOL Annex VI Chapter 4 (Resolution MEPC.203(62) of 2011, in force 1 January 2013). Although those regulations were the first mandatory energy-efficiency rules for any international transport sector, they were widely seen as insufficient to deliver the absolute emission reductions consistent with global climate targets. The Third Study’s projection of business-as-usual emissions to 2050 (50% to 250% above 2012, depending on the scenario) made the need for further action evident.

Paris Agreement and the renewed mandate (December 2015)

The Paris Agreement adopted at COP 21 in December 2015 took a different approach to international transport bunkers from the Kyoto Protocol. Rather than assigning the responsibility to ICAO and IMO by treaty, the Paris Agreement was silent on bunker emissions. Article 4 of the Paris Agreement requires Parties to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of the century; international shipping emissions are not formally included in any Party’s nationally determined contribution (NDC), but the Agreement implicitly assumes that shipping emissions will be addressed at the IMO.

The 2018 Special Report on Global Warming of 1.5°C published by the Intergovernmental Panel on Climate Change (IPCC) showed that the Paris Agreement’s 1.5°C temperature goal required global net-zero CO₂ emissions by approximately 2050. Translated to international shipping, that implied an absolute emission reduction trajectory inconsistent with the IMO’s then-existing programme of work. Pressure on the IMO from the Marshall Islands, the Pacific Islands Forum, the European Union and a number of major flag states grew sharply through 2016 and 2017.

MEPC 70 roadmap (October 2016)

MEPC 70 in October 2016, under the chairmanship of Hideaki Saito of Japan, agreed a Roadmap for developing a comprehensive IMO strategy on reduction of GHG emissions from ships. The Roadmap (MEPC 70/INF.21) identified a three-step process: a Data Collection System under Regulation 22A of MARPOL Annex VI (in force 1 March 2018); an Initial Strategy to be adopted at MEPC 72 in April 2018; and a final Revised Strategy to be adopted by 2023, informed by the data collected from 2019 onward. The Roadmap was the first concrete commitment to a defined timeline for IMO climate action, and it set the political framework within which the Initial Strategy was negotiated over the following 18 months.

The Initial IMO Strategy (MEPC 72, April 2018)

The Initial IMO Strategy on Reduction of GHG Emissions from Ships was adopted at MEPC 72 in London on 13 April 2018 by Resolution MEPC.304(72). The strategy was the product of an Intersessional Working Group on GHG Emissions from Ships (ISWG-GHG) that met three times between July 2017 and April 2018, working from successive draft texts proposed by the Marshall Islands (the so-called “Tony de Brum proposal”, named after the late Marshall Islands Foreign Minister), the European Union, the African Group of Negotiators, and a coalition of major flag states led by Panama and Liberia.

Vision

The Initial Strategy adopted the following vision:

“IMO remains committed to reducing GHG emissions from international shipping and, as a matter of urgency, aims to phase them out as soon as possible in this century.”

The reference to “as soon as possible in this century” was the product of intense negotiation; the EU, the Pacific Islands and the Marshall Islands had pressed for a 2050 absolute net-zero target, while a number of developing-country members objected that such a target conflicted with the principle of CBDR. The compromise text avoided a binding date but signalled an intent to phase out emissions in the long term.

Levels of ambition

The Initial Strategy set three quantitative levels of ambition:

1. Strengthen energy efficiency design requirements for ships, with the percentage improvement for each phase of the EEDI to be reviewed periodically and tightened where appropriate.
2. Reduce CO₂ emissions per transport work, as an average across international shipping, by at least 40% by 2030, pursuing efforts towards 70% by 2050, compared to 2008.
3. Peak GHG emissions from international shipping as soon as possible and reduce the total annual GHG emissions by at least 50% by 2050 compared to 2008, while pursuing efforts towards phasing them out as called for in the vision and consistent with the Paris Agreement temperature goals.

The first ambition is the trajectory followed by the EEDI Phases 0 to 3 (Resolution MEPC.231(65)). The second ambition is the trajectory implemented by the CII regime under Regulation 28 of Annex VI and the Required CII calculator. The third ambition is the absolute target that drives the mid-term measures discussed below.

Guiding principles

The Initial Strategy listed eight guiding principles, including the IMO’s principle of equal treatment of ships, the requirement that any measure be evidence-based and impact-assessed, the consideration of the impact on developing states, in particular Small Island Developing States (SIDS) and Least Developed Countries (LDCs), and the consideration of safety and energy security.

The interaction between the IMO principle of equal treatment of all flag states and the UNFCCC principle of CBDR remained unresolved in the Initial Strategy. The compromise was to require, as part of the impact assessment for any specific measure, an analysis of the disproportionately negative impacts that the measure might have on SIDS and LDCs, with mitigation actions to be developed if such impacts were identified. This compromise has shaped every subsequent IMO climate measure, including the design of the Net-Zero Framework approved at MEPC 83 in April 2025.

Candidate measures

The Initial Strategy listed candidate short-term, mid-term and long-term measures:

• Short-term measures (to be agreed and implemented between 2018 and 2023) included: further improvement of the EEDI; development of an EEXI for existing ships; adoption of a CII for operational efficiency; SEEMP enhancement; data analysis from the IMO DCS; and “operational efficiency measures” such as port-call optimisation and just-in-time arrival.

• Mid-term measures (to be agreed between 2023 and 2030) included: implementation of low-carbon and zero-carbon fuels; new and innovative emission-reduction technologies; market-based measures such as a global GHG fuel standard or an economic instrument; and a global certification scheme for marine fuel lifecycle GHG intensity.

• Long-term measures (to be considered after 2030) included: research and development of zero-emission technologies; development of zero-carbon fuel infrastructure; and “any other innovative emission reduction mechanisms” identified through the strategy review process.

The short-term measures were operationalised through the 2021 amendments to MARPOL Annex VI (Resolution MEPC.328(76)), introducing the EEXI, enhanced SEEMP Part III and CII rating. The mid-term measures became the focus of work between 2021 and 2025, culminating in the Net-Zero Framework approval at MEPC 83. The long-term measures remain under discussion as of 2026.

Reception and criticism

The Initial Strategy was widely welcomed as a significant step forward, but it was also widely criticised as insufficient. The European Union (and in particular Germany, the Netherlands and France) had pressed for the at least 50% by 2050 ambition to be calibrated against an absolute peaking date of 2008 and a steeper trajectory; the African Group of Negotiators had pressed for a longer trajectory consistent with the development needs of African coastal economies; the Marshall Islands and the Pacific Islands had pressed for an explicit 1.5°C-aligned target. The compromise reached in the Initial Strategy was widely understood as a “first step” rather than a final position, and the 2023 review was anticipated as the moment when the ambition would be tightened.

The shipping industry through its principal trade associations (the International Chamber of Shipping (ICS), BIMCO, INTERTANKO, INTERCARGO and the World Shipping Council) supported the Initial Strategy as a global framework that would prevent a fragmentation of regulation between regional regimes. Industry positioning subsequently shifted in 2020 when ICS proposed an industry-funded R&D fund (the IMO Maritime Research Board, financed by a USD 2 per tonne bunker levy) to accelerate development of zero-emission technologies; the proposal was discussed at MEPC 75 and 76 but not adopted, although the underlying concept of a bunker levy was carried forward into the mid-term measures negotiation.

Implementation of the Initial Strategy 2018 to 2023

Between MEPC 72 in 2018 and MEPC 80 in 2023, the IMO made substantial progress on the short-term measures and began detailed work on the mid-term measures.

Short-term measures: EEXI, CII, SEEMP Part III

MEPC 76 in June 2021 adopted Resolution MEPC.328(76), inserting the EEXI (Regulation 25), the CII (Regulation 28) and SEEMP Part III (Regulation 26) into MARPOL Annex VI Chapter 4. The amendments entered into force on 1 November 2022 with effect from 1 January 2023 (CII) and from the first survey on or after 1 January 2023 (EEXI). The implementing guidelines (MEPC.336(76) on the operational CII, MEPC.339(76) on the rating boundaries, and MEPC.350(78) on the reduction trajectory) were adopted in parallel.

The reduction trajectory of the Required CII (a 5% per year reduction from 2023 through 2026, with the post-2026 trajectory to be reviewed) was widely seen as a partial down-payment on the Initial Strategy’s first ambition. The corresponding calculation tools implement the trajectory; the 3-year corrective action plan calculator implements the regulatory consequence of failing to meet the trajectory.

Medium-term work: discussion on market-based measures

Discussion on the mid-term measures formally began in 2021 at MEPC 76 and accelerated through 2022 (MEPC 77 and 78) and 2023 (MEPC 79 and 80). The principal options on the table were:

• A global bunker levy or contribution scheme, proposed by the Marshall Islands and Solomon Islands at MEPC 76 (the so-called “USD 100 per tonne CO₂” proposal). The proposal would establish a flat-rate levy on bunker fuel proportional to its CO₂ content, with the revenue funding decarbonisation in developing states.
• A cap-and-trade scheme, proposed by the European Commission as the IMO analogue of the EU ETS Maritime. The scheme would set a global cap on shipping CO₂ emissions and require ships to surrender allowances on a per-tonne basis.
• A GHG Fuel Standard (GFS), proposed by Austria, France, Germany, Italy, the Netherlands and Spain. The standard would mandate a phased reduction in the well-to-wake GHG intensity of the fuel mix used by ships, similar in concept to FuelEU Maritime.
• A combined technical-and-economic instrument, proposed by the United States, Canada, Japan, Norway, the Republic of Korea and the United Kingdom. The instrument would combine a GFS-style technical measure with an economic instrument generating revenue.

By MEPC 80 in July 2023 a degree of convergence had emerged around the combined technical-and-economic option, with the GFS to set the regulatory backstop and the economic instrument to provide the financial incentive for over-compliance and the financial penalty for under-compliance.

Long-term work: research and development

The IMO Maritime Research Board proposed by ICS, INTERCARGO, INTERTANKO and BIMCO at MEPC 75 in 2020 was extensively discussed at MEPC 76, 77 and 78 but was not adopted. The proposal would have established a USD 5 billion R&D fund financed by a USD 2 per tonne bunker levy. The principal objection from a number of developing-country members was that the proposed Board would have been industry-controlled, with no formal IMO oversight. The conceptual approach (industry-financed R&D for zero-emission technologies) has been taken up under the IMO GreenVoyage 2050 Project, the Maritime Decarbonisation Hub at the Lloyd’s Register Foundation, and a number of bilateral and regional industry initiatives.

The Revised IMO Strategy (MEPC 80, July 2023)

The 2023 IMO Strategy on Reduction of GHG Emissions from Ships, adopted at MEPC 80 in London on 7 July 2023 by Resolution MEPC.377(80), is the substantive revision of the Initial Strategy that the 2016 Roadmap had committed the IMO to deliver. The Revised Strategy was negotiated against the backdrop of the IPCC AR6 reports (2021 to 2022), the energy-price dislocation following the Russian invasion of Ukraine in February 2022, the entry into force of the EU ETS Maritime on 1 January 2024 and the publication in 2023 of the Paris-aligned shipping decarbonisation pathways developed by Lloyd’s Register, DNV and the University Maritime Advisory Services consortium.

Revised vision

The Revised Strategy adopts the following vision:

“IMO remains committed to reducing GHG emissions from international shipping and, as a matter of urgency, to phasing them out as soon as possible, while promoting, in the context of this Strategy, a just and equitable transition.”

The phrase net-zero GHG emissions by or around 2050 appears in the levels of ambition (paragraph 3.1.3, see below) rather than in the vision proper. The adoption of “net-zero by or around 2050” was the central political achievement of MEPC 80; the strategy is widely characterised in the secondary literature as the maritime sector’s Paris-aligned commitment, although the phrase “1.5°C compatible” is conspicuously absent from the operative text.

Revised levels of ambition

The Revised Strategy sets three quantitative levels of ambition, replacing those of the Initial Strategy:

1. Carbon intensity of the ship to decline through further improvement of the energy efficiency for new ships: to review with the aim of strengthening the energy efficiency design requirements for ships.
2. Carbon intensity of international shipping to decline: to reduce CO₂ emissions per transport work, as an average across international shipping, by at least 40% by 2030, compared to 2008.
3. Uptake of zero or near-zero GHG emission technologies, fuels and/or energy sources to increase: zero or near-zero GHG emission technologies, fuels and/or energy sources to represent at least 5%, striving for 10%, of the energy used by international shipping by 2030.
4. GHG emissions from international shipping to reach net-zero by or around, i.e. close to, 2050 taking into account different national circumstances, whilst pursuing efforts towards phasing them out as called for in the Vision.

(The Revised Strategy numbers these as 3.1.1, 3.1.2 (a) and (b), 3.1.3.)

Indicative checkpoints 2030 and 2040

In addition to the three quantitative levels of ambition, the Revised Strategy introduces two indicative checkpoints to chart the trajectory towards net-zero by or around 2050:

• Indicative checkpoint 2030: reduce the total annual GHG emissions from international shipping by at least 20%, striving for 30%, by 2030, compared to 2008.
• Indicative checkpoint 2040: reduce the total annual GHG emissions from international shipping by at least 70%, striving for 80%, by 2040, compared to 2008.

The indicative checkpoints are not formally targets in the same sense as the levels of ambition; they are explicitly described as indicative, to be revisited as scientific evidence and the implementation of measures progresses. Nevertheless, the figures are widely used by the shipping industry, finance institutions and regulators as the de facto interim targets that the mid-term measures must deliver.

Zero/near-zero fuel uptake target 2030

The 2030 zero/near-zero fuel uptake target (5% to 10% of total energy used) is the most concrete of the Revised Strategy’s quantitative ambitions. International shipping consumed approximately 300 Mt of bunker fuel in 2022 (approximately 12 EJ of energy); 5% of that energy is approximately 0.6 EJ, equivalent to 12 to 18 Mt of LNG-equivalent low-carbon fuel. The target requires significant new low-carbon fuel production capacity to come on-stream between 2025 and 2030. The principal candidates are bio-LNG, green methanol, green ammonia and biofuels. LNG per se does not count toward the target unless it is well-to-wake at or below the threshold defined in the IMO LCA Guidelines (typically interpreted as approximately 70% of the well-to-wake GHG intensity of conventional HFO).

Reception and criticism

The Revised Strategy was widely welcomed by the shipping industry as a clear long-term signal that justified investment in zero-emission technologies and fuels. The Pacific Islands Forum welcomed the net-zero target while expressing disappointment that the 2030 and 2040 checkpoints were not aligned with the IPCC’s 1.5°C-compatible trajectory (which would have required approximately 37% reduction by 2030 and approximately 96% by 2040, according to the University Maritime Advisory Services analysis). The European Commission characterised the Strategy as “ambitious but realistic” and aligned with the EU’s Fit for 55 package; the United States Treasury characterised it as “the most ambitious global climate commitment by any UN sectoral agency”.

A number of developing-country members, in particular Argentina, Brazil, China, India and South Africa, expressed concern about the impact of the implementing measures on developing-country export economies, particularly those reliant on long-distance shipping (e.g. iron ore exports from Brazil to Asia, soybean exports from Argentina). The Strategy explicitly preserved the requirement that any specific measure be subject to an impact assessment with particular attention to disproportionately negative impacts on SIDS and LDCs, with mitigation to be developed where such impacts are identified.

Lifecycle GHG accounting (LCA Guidelines, MEPC.376(80))

A central methodological innovation of the Revised Strategy is the formal adoption of the well-to-wake (WtW) accounting framework. The 2024 IMO Guidelines on Lifecycle GHG Intensity of Marine Fuels (LCA Guidelines), adopted by Resolution MEPC.376(80) at MEPC 80 in July 2023 and refined by Resolution MEPC.391(82) at MEPC 82 in October 2024, set out the methodology for quantifying the well-to-wake GHG intensity of any marine fuel pathway in g CO₂-equivalent per MJ.

Well-to-wake methodology

The well-to-wake intensity comprises three components:

1. Well-to-tank (WtT) emissions: all emissions from fuel production, conversion, processing and transport to the bunkering point. For fossil fuels, these are typically dominated by the upstream extraction and refining processes; for biofuels, they include feedstock production, transport, conversion and any indirect land-use change emissions; for synthetic e-fuels, they include the renewable electricity generation, hydrogen electrolysis, carbon capture and synthesis stages.
2. Tank-to-wake (TtW) emissions: all emissions from on-board fuel use, including CO₂ from combustion and any methane (CH₄) and nitrous oxide (N₂O) emissions converted to CO₂-equivalent using the GWP100 metric (28 for CH₄, 273 for N₂O).
3. Methane slip and N₂O slip: explicitly accounted for. The methane slip CO₂-equivalent calculator and the methane slip mass-rate calculator implement the GWP100 conversion. The ammonia NOx + N₂O slip calculator implements the equivalent for ammonia engines, where N₂O slip is the principal climate impact concern.

The WtW intensity is reported in g CO₂-equivalent per MJ of fuel energy (lower heating value basis). The IMO LCA Guidelines provide default values for the principal fuel pathways and a procedure for certifying ship-specific values where actual data are available.

Default well-to-wake values per fuel pathway

The default WtW values from MEPC.391(82) are approximately:

(The figures are illustrative and round; the exact values are set out in MEPC.391(82) Table 1.)

The biofuel and e-fuel figures in the table use the net of biogenic CO₂ convention, on the basis that the CO₂ released at combustion is matched by CO₂ absorbed during feedstock growth (or by direct air capture in the case of e-fuels). The convention is consistent with IPCC AR5 and AR6 methodology and with the EU Renewable Energy Directive RED III, but it is contested by a number of NGOs that argue that crop-based biofuels can have substantial indirect land-use change emissions that are not captured in the IMO defaults. The LCA Guidelines explicitly require that biofuels meet the sustainability criteria of the host-state legislation (EU RED III in the EU, the California Low Carbon Fuel Standard in the US, etc.) to qualify for the net-of-biogenic accounting. The LNG well-to-wake calculator implements the methodology for the LNG pathways.

Sustainability criteria for biofuels

The LCA Guidelines recognise the EU RED III sustainability criteria as the international reference standard for biofuel certification. RED III requires that biofuels demonstrate at least 65% (or 70% for new installations) GHG reduction relative to the fossil fuel comparator (94 g CO₂-eq/MJ for transport fuels), that they are produced from listed feedstocks, and that they comply with land-use, biodiversity and water-stewardship criteria. Biofuels not meeting the criteria are accounted at their gross WtW value, including the biogenic CO₂ from combustion.

The IMO LCA Guidelines are explicitly fuel-pathway-neutral: any fuel that meets the GFI threshold may be used, and the WtW accounting captures the actual climate impact regardless of the technology pathway. This contrasts with some regional regimes (e.g. the German “Future Fuels Strategy” prioritising e-fuels over biofuels) that prefer specific pathways for industrial-policy reasons.

Mid-term measures: GFS and economic instrument

GHG Fuel Standard (technical element)

The GHG Fuel Standard (GFS) is the technical element of the mid-term measures basket. It establishes a maximum permissible well-to-wake GHG intensity of the fuel mix used by each ship, expressed in g CO₂-equivalent per MJ. The Required GFI declines annually on a defined trajectory anchored to the 2008 baseline (approximately 92 g CO₂-equivalent/MJ for the average international shipping fuel mix in 2008).

The reduction factors agreed at MEPC 83 in April 2025 are:

• 2028: 4% reduction
• 2030: 17% reduction
• 2035: 30% reduction
• 2040: 65% reduction

The 2028 starting point reflects a deliberate phase-in strategy, with the steepest reductions clustered between 2030 and 2040 to align with the indicative checkpoints. The 2040-to-2050 trajectory (and the post-2040 reduction factors) will be reviewed at MEPC 92 in 2031 in light of the actual implementation experience and the trajectory of zero-emission fuel cost reductions.

Economic instrument (pricing element)

The economic instrument is the pricing element of the mid-term measures basket. It establishes a price for Remediation Units (RUs) that ships exceeding the Required GFI must surrender. The unit of account is one tonne CO₂-equivalent of well-to-wake emissions in excess of the Required GFI. The initial price agreed at MEPC 83 is approximately USD 100 per tonne CO₂-equivalent in 2027, rising on a defined trajectory.

A second threshold, the Direct Compliance Threshold (DCT), is set tighter than the Required GFI. Ships emitting at or below the DCT earn Surplus Units (SUs), which may be banked for future use or traded. The architecture is conceptually similar to the cap-and-trade design of the EU ETS Maritime but operates on a global, fuel-intensity basis rather than a regional, total-emissions basis.

The revenue from RU surrender flows into the IMO Net-Zero Fund, established by MEPC 83 as a dedicated mechanism for funding decarbonisation infrastructure in developing states, particularly SIDS and LDCs. The Fund is the principal compromise mechanism that secured the agreement of developing-country members; the principle is that ships in developed-country trade pay into the Fund and that the proceeds are used to support port-side bunkering infrastructure for low-carbon fuels in developing-country markets, helping to ensure that the global transition is genuinely globally accessible.

Architecture options 2024 to 2025

Between MEPC 80 in July 2023 and MEPC 83 in April 2025, MEPC and its intersessional working groups debated five principal architecture options:

• Option A: Pure GFS, with no economic instrument. Compliance through fuel switching only.
• Option B: GFS plus a flat per-tonne contribution from each ship into a fund (proposed by the Marshall Islands and Solomon Islands).
• Option C: GFS plus a cap-and-trade with global allowance allocation (proposed by the European Commission and Norway).
• Option D: GFS plus a “feebate” (fee for non-compliance, rebate for over-compliance) using the RU/SU architecture eventually adopted (proposed by the United States, Japan and the United Kingdom).
• Option E: Cap-and-trade only, with no GFS (proposed by the United Arab Emirates).

The Net-Zero Framework approved at MEPC 83 in April 2025 is essentially Option D, modified to include a Fund mechanism similar to that proposed in Option B for the use of the RU revenue. The choice was driven by the need to combine a clear regulatory backstop (the GFS, providing certainty for fuel suppliers and shipowners) with an economic mechanism that incentivises over-compliance and penalises under-compliance without setting a hard cap on global shipping emissions.

MEPC 83 approval of the Net-Zero Framework (April 2025)

MEPC 83 met in London from 7 to 11 April 2025 and on the final day approved the IMO Net-Zero Framework as a complete revision of MARPOL Annex VI Chapter 4, adding a new “Chapter 4 ter” comprising the GFS and the economic instrument. The framework was adopted by a majority vote (the first time in the IMO’s history that a major MARPOL amendment has been adopted by majority rather than consensus); the dissenting votes were cast principally by oil-exporting states (Saudi Arabia, the United Arab Emirates, Iran and Russia) and a small number of developing-country members. The instrument was approved subject to formal adoption at MEPC 84 in October 2025 and entry into force on 1 January 2027.

The MEPC 83 approval is widely characterised as the most consequential IMO climate decision since the 1997 Annex VI Protocol itself. It is the first global GHG pricing mechanism for any international transport sector and is expected to drive a fundamental restructuring of the global bunker market over the period 2027 to 2040.

Sectoral and intergenerational considerations

Just and equitable transition

The Revised Strategy explicitly references a “just and equitable transition” in its vision. The phrase has multiple meanings:

• Just transition for seafarers: the global maritime workforce of approximately 1.9 million seafarers (per the BIMCO/ICS Seafarer Workforce Report 2025) must be retrained for the operation of zero-emission vessels and the new bunkering infrastructure. The STCW Convention competencies are being revised through the IMO HTW Sub-Committee to incorporate ammonia, hydrogen and methanol fuel handling.
• Just transition for developing economies: the cost of implementing the Net-Zero Framework must not be disproportionately borne by developing states, particularly SIDS and LDCs. The IMO Net-Zero Fund mechanism is the principal instrument for this objective.
• Intergenerational equity: the strategy recognises that the climate impact of shipping emissions is largely borne by future generations, and that the current generation has a responsibility to bring shipping emissions to net-zero on a timeline consistent with the Paris Agreement temperature goals.

Disproportionately negative impacts on developing states

The IMO process for assessing disproportionately negative impacts on SIDS and LDCs has been formalised through the comprehensive impact assessment required by Annex 11 of the 2018 Initial Strategy and refined through MEPC.1/Circ.885 (2022). The assessment covers: GDP impact (typically the most concentrated for SIDS reliant on long-distance import of essential goods); food security impact; trade-cost impact; and the impact on national port and bunkering infrastructure. Mitigation measures developed under the impact-assessment framework include: differentiated implementation timelines for SIDS-flagged vessels; preferential access to the Net-Zero Fund for SIDS infrastructure investment; and Technical Cooperation under MARPOL Annex VI Regulation 23.

Revenue use from the economic instrument

The use of the revenue from the economic instrument is one of the most contested issues in the implementation of the Net-Zero Framework. The principal options are:

• In-sector use: revenue used for shipping decarbonisation projects, including R&D, port infrastructure, fuel-pathway scaling, and crew training.
• Climate finance use: revenue used as international climate finance under the UNFCCC, transferred to the Green Climate Fund or to bilateral climate-finance windows.
• Hybrid use: a portion for in-sector use and a portion for climate finance.

MEPC 83 agreed in principle that the IMO Net-Zero Fund will operate principally on the in-sector model, with a defined share (initially proposed at 20% to 30%) directed to the UNFCCC climate finance system. The exact split and the governance of the Fund will be finalised at MEPC 84 in October 2025 and reviewed every five years thereafter.

Comparison with national / regional climate frameworks

Paris Agreement

The IMO GHG Strategy is not formally part of the Paris Agreement framework, but the 2023 Revised Strategy is widely understood as the maritime sector’s contribution to the Paris temperature goals. The “net-zero by or around 2050” trajectory is broadly aligned with the global net-zero CO₂ trajectory implied by the 1.5°C goal, although the IMO trajectory does not formally claim 1.5°C compatibility. The 2023 IPCC AR6 Synthesis Report identified international shipping as one of the “hard-to-abate” sectors requiring dedicated decarbonisation pathways.

EU Green Deal and Fit for 55

The European Union has implemented an ambitious package of shipping climate measures since 2018, including the EU ETS Maritime (entered into force 1 January 2024), FuelEU Maritime (entered into force 1 January 2025), and the FuelEU pooling and multiplier framework. The EU framework is generally tighter than the IMO Net-Zero Framework in the period 2025 to 2030 but converges with the IMO trajectory by 2040. The interaction between the two regimes is governed by the EU’s stated commitment to “support and integrate” the IMO measures while preserving the EU’s autonomous regulatory authority within EU waters.

US Inflation Reduction Act and shipping

The United States Inflation Reduction Act (IRA) of 2022 established a series of tax credits and grants for the production of low-carbon hydrogen, sustainable aviation fuel and clean ammonia. While not directly addressed at international shipping, the IRA’s hydrogen production tax credit (45V), with values up to USD 3 per kg of hydrogen produced, is the principal financial driver for the development of green-ammonia and green-methanol bunker fuel production capacity in the United States. The combination of IRA financial support and IMO regulatory demand is widely seen as the principal mechanism by which the 2030 zero/near-zero fuel uptake target will be achieved.

Compliance projection and the marginal abatement cost curve

Multiple consultancy and academic studies have modelled the marginal abatement cost curve (MACC) for international shipping decarbonisation under the Revised Strategy. The principal studies are: DNV’s Maritime Forecast to 2050 (annual editions); the Global Maritime Forum’s Getting to Zero Coalition analyses; the University Maritime Advisory Services’ Pathway 1.5°C studies; and the Mission Possible Partnership’s Industry Transition Strategy.

The studies converge on a MACC with three principal segments:

• Operational and technical efficiency (USD 0 to 100 per tonne CO₂ abated): includes slow steaming, trim optimisation, weather routing, hull cleaning, propeller polishing, air lubrication, wind-assist devices and engine retrofits.
• Drop-in low-carbon fuels (USD 100 to 300 per tonne CO₂ abated): includes bio-LNG, bio-methanol, B20 and B30 biofuel blends for residual fuel ships.
• Zero-carbon fuels and new ship types (USD 300 to 800 per tonne CO₂ abated): includes green ammonia, green methanol, hydrogen, full-electric propulsion for short-sea routes, and new-build vessels designed for these fuels.

The Net-Zero Framework’s initial RU price of USD 100 per tonne CO₂-equivalent is calibrated to drive uptake of the operational and technical efficiency measures and the cheapest drop-in low-carbon fuels. Higher RU prices over time will be needed to drive uptake of the zero-carbon fuels and new ship types. The DNV Maritime Forecast 2025 projects that the RU price would need to reach approximately USD 250 per tonne CO₂-equivalent by 2035 and USD 400 by 2045 to drive net-zero by or around 2050.

Critical assessment

Is the strategy ambitious enough?

The Revised Strategy’s “net-zero by or around 2050” target is broadly aligned with the IPCC 1.5°C-compatible global net-zero trajectory but is not formally claimed to be 1.5°C-compatible. The 2030 indicative checkpoint of 20% to 30% is below the 37% reduction that the University Maritime Advisory Services has identified as the 1.5°C-compatible figure. The 2040 indicative checkpoint of 70% to 80% is closer to the 1.5°C-compatible 96% but still below it.

The shipping industry’s own assessment, through the Getting to Zero Coalition, is that the Revised Strategy is “consistent with well below 2°C and reasonably consistent with 1.5°C with limited overshoot”. The Pacific Islands Forum’s assessment is that the Strategy is “a significant step forward but insufficient for 1.5°C”. The European Commission’s assessment is that the Strategy is “ambitious but realistic”.

Is it realistic?

The principal concern about realism relates to the supply of zero/near-zero fuels to meet the 2030 uptake target. The IEA’s World Energy Outlook 2024 projects total global low-carbon fuel production capacity (across all transport sectors) of approximately 0.5 EJ in 2030, against shipping’s 5% target of approximately 0.6 EJ. Even at the lower 5% bound, the target requires shipping to capture the great majority of global low-carbon fuel production in 2030, which is widely regarded as challenging given the competing demand from aviation, road transport and industry.

The 2040 indicative checkpoint of 70% to 80% emissions reduction is contingent on the rapid scaling of zero-carbon fuels, which in turn is contingent on the scaling of global renewable electricity production. The World Bank’s Charting a Course for Decarbonising Maritime Transport (2024) identifies the renewable electricity scaling as the principal binding constraint on the 2040 trajectory.

Industry positions

The principal industry positions on the Revised Strategy are:

• International Chamber of Shipping (ICS): supportive, with caveats about the need for adequate fuel supply and the importance of preserving competitive neutrality through global rather than regional regulation.
• BIMCO: supportive, with focus on the implications for charter parties (the BIMCO CII clauses of 2022 and the BIMCO EU ETS clause of 2023 provide the contractual framework).
• INTERTANKO: supportive of the GFS, sceptical of the economic instrument architecture before MEPC 83 confirmed the Direct Compliance Threshold mechanism.
• INTERCARGO: supportive of the strategy, focus on impact on bulk carriers serving developing-country trades.
• World Shipping Council (WSC): strongly supportive, with continuous engagement on the implementing rules.
• Cruise Lines International Association (CLIA): supportive, with focus on the application of the strategy to cruise vessels and the parallel CARB at-berth regime in California.
• Clean Shipping Coalition (NGO observer): supportive of the direction but critical of the speed and the exact reduction trajectory; have called for the indicative 2030 checkpoint to be tightened to the 30% figure (the upper bound of the 20% to 30% range).

Future outlook

The principal regulatory developments expected through 2030 are:

• MEPC 84 (October 2025): formal adoption of the Net-Zero Framework with finalised reduction trajectory and economic-instrument design.
• MEPC 86 (mid-2027): review of the CII reduction factors beyond 2026 and entry into force of the Net-Zero Framework.
• MEPC 88 (mid-2028): first reporting cycle under the Net-Zero Framework; first RU surrender by ships in deficit.
• MEPC 90 to 92 (2029 to 2031): comprehensive five-year review of the Net-Zero Framework against the 2030 indicative checkpoint and the levels of ambition.

By 2030 the IMO is expected to have a clearer picture of the trajectory toward the 2040 indicative checkpoint and the 2050 net-zero target. Significant uncertainties remain about the supply of zero-carbon fuels, the cost trajectory of the Net-Zero Framework, the political sustainability of the international consensus that produced the 2023 Revised Strategy, and the interaction with regional regimes that may tighten faster than the IMO global framework. The Revised Strategy will itself be reviewed at MEPC in 2028 (per the timeline set out in paragraph 5 of MEPC.377(80)), with the next major revision expected to coincide with the 2030 indicative checkpoint.

Related Calculators

• CII Rating (A–E) Calculator
• EEXI Attained Calculator
• LNG Methane Slip, GWP20 / GWP100 GHG Calculator
• LNG, Otto MS / Otto SS / Diesel WtW Calculator
• MARPOL Annex VI/22, SEEMP Calculator
• MARPOL Annex VI/22A, Data collection system Calculator
• MARPOL Annex VI/28, CII Calculator
• CII Required Calculator
• MARPOL Annex VI/26, SEEMP revised Calculator
• CII 3-year Corrective Plan Calculator
• CH₄ Methane Slip Calculator
• Ammonia Fuel, NOx + N₂O Slip Calculator
• MARPOL Annex VI/23, Transfer of efficiency tech Calculator
• CII Attained Calculator
• CII Voyage Adjustment & Exclusion Calculator
• CII, Year-on-Year Improvement Calculator
• CII, SFOC & Fuel Mix Quick Check Calculator
• EEDI Attained Calculator
• EEDI Required Calculator
• EEDI Reference Line Calculator
• EEDI Phase Factor Calculator
• EEDI Ice-class Correction (fⱼ) Calculator
• Cubic Capacity Correction (fcᵤbᵢc) Calculator
• Voluntary Structural Enhancement (fᵥˢᵉ) Calculator
• EEDI Innovative Tech Credit Calculator
• EEXI Required Calculator
• MARPOL Annex VI, EEXI Required Index Calculator
• IMO DCS, Annual Fuel Report Calculator
• MARPOL Annex VI/27, Data collection system Calculator
• SOₓ from Fuel Sulphur Calculator
• Black Carbon Calculator
• PM10 / PM2.5 Calculator
• EU ETS, Annual Allowance Cost Calculator
• FuelEU Maritime, GHG Penalty Cost Calculator
• EU MRV Emissions Report Calculator
• ESI, Environmental Ship Index Calculator
• Norway NOx Fund Levy Calculator
• Engine, Thermal Efficiency Calculator
• Engine, CO₂ per kWh Calculator
• Cube Law Fuel Ratio Calculator
• Ship Recycling GHG Calculator
• RightShip GHG Rating Calculator
• MARPOL Annex VI/5, Survey and certification Calculator
• MARPOL Annex VI/6, IAPP certificate Calculator

See also

• MARPOL Annex VI - the IMO instrument that operationalises the GHG Strategy through binding regulations
• MARPOL Convention - the parent treaty
• SOLAS Convention - the principal IMO safety treaty interacting with the GHG Strategy on energy efficiency
• STCW Convention - training and watchkeeping standards being revised for zero-emission fuel handling
• What is CII - the carbon intensity indicator implementing the operational efficiency level of ambition
• What is EEDI - the energy efficiency design index implementing the design-phase level of ambition
• What is EEXI - the energy efficiency existing ship index applied retroactively as a short-term measure
• Slow steaming and CII - the principal operational lever for the carbon-intensity reduction trajectory
• EU ETS for shipping - the principal regional cap-and-trade regime running in parallel with the IMO framework
• FuelEU Maritime explained - the EU’s parallel well-to-wake intensity regime
• FuelEU penalties, pooling and multipliers - the FuelEU compliance mechanics
• IMO DCS vs EU MRV - parallel reporting regimes underpinning both the IMO and EU climate frameworks
• Cold ironing and shore power - in-port emission reduction technique
• Biofuels in shipping - low-carbon fuel pathway central to the 2030 fuel uptake target
• LNG as marine fuel - dual-fuel transition fuel
• Methanol as marine fuel - alternative fuel pathway for the Net-Zero Framework
• Ammonia as marine fuel - zero-carbon fuel pathway for the Net-Zero Framework
• Heavy fuel oil - the residual fuel that the Strategy aims to phase out
• Marine gas oil - the distillate fuel commonly used in ECAs
• Specific fuel oil consumption - the engine efficiency metric central to EEDI / EEXI / GFS
• IMO 2020 sulphur cap - the related but separate Annex VI air-pollution amendment
• Exhaust gas cleaning system - the scrubber technology used for sulphur compliance with possible CO₂ co-benefit
• Selective catalytic reduction - the SCR after-treatment used for Tier III NOx
• Marine diesel engine - the engine technology subject to EEDI / EEXI calculation
• LNG fuel system - the gas-handling system on dual-fuel ships subject to GFS calculation
• Port state control - the enforcement mechanism for IMO climate measures in foreign ports
• Classification society - Recognised Organisations conducting energy-efficiency certification surveys
• Flag state and flag of convenience - the flag-state responsibility for IMO Strategy implementation
• COLREGs Convention - the parallel IMO instrument addressing collision avoidance
• CII attained calculator - the operational CII calculation
• CII required calculator - the regulation-driven Required CII calculation
• CII rating calculator - the A-to-E rating mapping
• CII 3-year corrective action plan calculator - the Regulation 28.10 plan trigger
• CII voyage adjustment calculator - the voyage-level CII analysis
• CII year-on-year improvement calculator - the year-on-year reduction trajectory
• SFOC-to-CII converter - engine SFOC to ship CII rating
• EEDI attained calculator - the design-phase index calculation
• EEDI required calculator - the regulation-driven Required EEDI calculation
• EEDI reference line calculator - the 2008 baseline for the EEDI trajectory
• EEDI phase factor calculator - Phases 0 to 3 reduction factors
• EEDI ice-class fj calculator - ice-class correction
• EEDI fcubic calculator - hull-form correction
• EEDI fvse calculator - voluntary structural enhancement
• EEDI innovative-tech calculator - innovative technology credit
• EEXI attained calculator - the EEXI as-built calculation
• EEXI required calculator - the regulation-driven Required EEXI calculation
• MARPOL EEXI required calculator - the regulation-anchored variant
• SEEMP calculator - SEEMP Part I structure
• SEEMP revised calculator - SEEMP Part III CII operational plan
• IMO DCS report calculator - annual fuel-consumption report
• IMO DCS Reg 22A calculator - data collection plan
• IMO DCS Reg 27 calculator - data submission
• Methane slip calculator - LNG dual-fuel methane-slip mass rate
• Methane slip CO₂-equivalent calculator - GWP100 / GWP20 conversion
• Ammonia NOx + N₂O slip calculator - the ammonia-engine GHG slip
• LNG well-to-wake calculator - LNG WtW intensity for GFS calculation
• SOx from fuel sulphur calculator - SOx mass-emission rate
• Black carbon calculator - IMO Black Carbon Reference Method
• PM10 / PM2.5 calculator - particulate-matter emission estimate
• MARPOL EU ETS cost calculator - EU ETS surrender cost
• MARPOL FuelEU penalty calculator - FuelEU non-compliance penalty
• EU MRV emissions calculator - parallel European reporting
• ESI score calculator - Environmental Ship Index voluntary recognition
• Norway NOx Fund calculator - national NOx levy
• Brake thermal efficiency calculator - engine thermal efficiency from SFOC
• Engine CO₂ emission per kWh calculator - engine CO₂ rate
• Engine cube-law fuel calculator - speed-fuel relationship for slow steaming
• Lifecycle recycling GHG calculator - end-of-life recycling GHG accounting
• RightShip GHG index calculator - voluntary fleet GHG benchmarking
• Survey calculator - Annex VI survey cycle for IEE Certificate
• IAPP certificate calculator - IAPP issue and endorsement
• ShipCalculators.com calculator catalogue - full listing of IMO climate and emissions calculators

References

1. IMO MEPC. Resolution MEPC.304(72) - Initial IMO Strategy on Reduction of GHG Emissions from Ships. IMO, 13 April 2018.
2. IMO MEPC. Resolution MEPC.377(80) - 2023 IMO Strategy on Reduction of GHG Emissions from Ships. IMO, 7 July 2023.
3. IMO MEPC. Resolution MEPC.376(80) - 2024 Guidelines on Lifecycle GHG Intensity of Marine Fuels. IMO, 7 July 2023.
4. IMO MEPC. Resolution MEPC.391(82) - 2024 Update to LCA Guidelines (Default Pathways). IMO, October 2024.
5. IMO MEPC. Resolution MEPC.328(76) - Amendments to MARPOL Annex VI (EEXI, CII, SEEMP Part III). IMO, 17 June 2021.
6. IMO MEPC. Resolution MEPC.336(76) - 2021 Guidelines on the Operational Carbon Intensity Indicators. IMO, 17 June 2021.
7. IMO Assembly. Resolution A.963(23) - IMO Policies and Practices Related to the Reduction of Greenhouse Gas Emissions from Ships. IMO, 5 December 2003.
8. IMO. Second IMO GHG Study 2009. IMO, London, 2009.
9. IMO. Third IMO GHG Study 2014. IMO, London, 2014.
10. IMO. Fourth IMO GHG Study 2020. IMO, London, 2020.
11. IMO. Net-Zero Framework: Approval Document. MEPC 83/INF.3, April 2025.
12. IMO. MEPC 70/INF.21 - Roadmap for Developing a Comprehensive IMO Strategy on Reduction of GHG Emissions from Ships. IMO, October 2016.
13. IPCC. Special Report on Global Warming of 1.5°C. IPCC, Geneva, 2018.
14. IPCC. Sixth Assessment Report (AR6) Synthesis Report. IPCC, Geneva, 2023.
15. United Nations. Paris Agreement. UN, New York, 12 December 2015.
16. United Nations. Kyoto Protocol. UN, New York, 11 December 1997.
17. CE Delft, UMAS et al. The Pathway 1.5°C Studies. London, 2022 to 2024.
18. DNV. Maritime Forecast to 2050. DNV, Oslo, annual editions 2017 to 2025.
19. Global Maritime Forum. Getting to Zero Coalition - Annual Reports. Copenhagen, 2019 to 2025.
20. Mission Possible Partnership. Industry Transition Strategy: Shipping. Energy Transitions Commission, London, 2022.
21. World Bank. Charting a Course for Decarbonising Maritime Transport. World Bank, Washington, 2024.
22. International Energy Agency. World Energy Outlook 2024. OECD/IEA, Paris, 2024.
23. UMAS. Reducing the Maritime Sector’s Contribution to Climate Change and Air Pollution: Scenario Analysis. UCL Energy Institute, London, 2023.

Further reading

• IMO. IMO and the Environment. IMO Publishing, London, 2024.
• Doelle, M. and Chircop, A. (eds). Climate Change and the Law of the Sea: Adapting the Law of the Sea to Address the Challenges of Climate Change. Brill, Leiden, 2022.
• Faber, J. et al. Reduction of GHG Emissions from Ships: Fourth IMO GHG Study. IMO, London, 2020.
• Smith, T. et al. The Pathway to Decarbonisation in International Shipping. UMAS, London, 2024.
• Lloyd’s Register and UMAS. Zero-Emission Vessels: Transition Pathways. London, 2017.

External links

• IMO GHG page - official IMO climate landing page
• IMO Initial Strategy text MEPC.304(72) - official PDF
• IMO 2023 Revised Strategy text MEPC.377(80) - official PDF
• IMO LCA Guidelines MEPC.376(80) - official PDF
• Getting to Zero Coalition - industry-NGO coalition tracking IMO climate progress
• UMAS - University Maritime Advisory Services research portal
• European Commission Maritime Climate Page - EU implementing measures