IMO’s work to cut GHG emissions from ships


Acting to cut emissions from ships 

IMO is committed to supporting UN Sustainable Development Goal 13 - to take urgent action to combat climate change and its impacts – in line with the 2015 Paris Agreement to cut greenhouse gas (GHG) emissions which cause global warming. 

The International Maritime Organization (IMO) adopted the first set of international mandatory measures to improve ships' energy efficiency on 15 July 2011. Since then, IMO has taken additional action including further regulatory measures, the adoption of the Initial IMO GHG strategy in 2018, and, in 2023, the revised Strategy on Reduction of GHG Emissions from Ships. To support their implementation, IMO executes a comprehensive capacity building and technical assistance programme, including a range of global projects. Read more about that work here.

2023 IMO Strategy on Reduction of GHG Emissions from Ships 

In July 2023, IMO Member States adopted the 2023 IMO Strategy on Reduction of GHG Emissions from Ships, with enhanced targets to tackle harmful emissions. 

The revised IMO GHG Strategy, adopted at the Marine Environment Protection Committee (MEPC 80) includes an enhanced common ambition to reach net-zero GHG emissions from international shipping by or around, i.e. close to 2050, a commitment to ensure an uptake of alternative zero and near-zero GHG fuels by 2030, as well as indicative check-points for international shipping to reach net-zero GHG emissions for 2030 (by at least 20%, striving for 30%) and 2040 (by at least 70%, striving for 80%).  

In particular, the 2023 IMO GHG Strategy envisages a reduction in carbon intensity of international shipping (to reduce CO2 emissions per transport work), as an average across international shipping, by at least 40% by 2030. The new level of ambition relates to the uptake of zero or near-zero GHG emission technologies, fuels and/or energy sources: they are to represent at least 5%, striving for 10%, of the energy used by international shipping by 2030. 

It is envisaged that a review of the 2023 IMO GHG Strategy will be finalized when the Marine Environment Committee meets in autumn 2028, with a view to adoption of the 2028 IMO Strategy on reduction of GHG emissions from ships. 

More detail about the Revised Strategy is available here, and you can download the text of the strategy (subject to final editorial amendments) here

The downloadable infographic below outlines key regulatory and implementation support steps as set out in the 2023 IMO Strategy on Reduction of GHG Emissions from Ships.

2023 GHG Strategy timeline infographic.jpg

2023 candidate mid-term GHG measures 

The 2023 GHG Strategy states that a basket of candidate measure(s), delivering on the reduction targets, should be developed and finalized, comprised of both:  

  1. a technical element, namely a goal-based marine fuel standard regulating the phased reduction of the marine fuel's GHG intensity;  and  
  2. an economic element, on the basis of a maritime GHG emissions pricing mechanism.  

The candidate economic elements will be assessed observing specific criteria to be considered in a comprehensive impact assessment, with a view to facilitating the finalization of the basket of measures.  

The mid-term GHG reduction measures should effectively promote the energy transition of shipping and provide the world fleet with an incentive while contributing to a level playing field and a just and equitable transition. 

A Work Plan to progress the development of mid- and long-term GHG reduction measures in line with the Initial IMO Strategy was approved in 2021. Phase 1 identified the key issues in relation to each proposed measure that required consideration. Phase 2 built upon that work and selected which measure(s) to further develop as a priority. The focus of Phase 3 is the finalization of the development of a measure or measures within (an) agreed target date(s). Read more about the Work Plan here

Outcomes of the latest Intersessional Working Group (ISWG -GHG) and MEPC can be found here 

Support for developing countries  

The 2023 IMO GHG Strategy acknowledges the challenges that developing countries, in particular least developed countries (LDCs) and small island developing States (SIDS), may face in the implementation of the Strategy. IMO, with funding assistance from Member States, provides support for LDCS and SIDS through a series of capacity-building and technical cooperation programmes 

2018 Initial IMO GHG Strategy 

The 2018 IMO Initial Strategy on the reduction of GHG emissions from shipping set IMO on a pathway to reducing GHG emissions. It envisaged reducing total annual GHG emissions from ships by at least 50% by 2050 compared to 2008, and included a series of candidate short-, mid- and long-term measures that built on already-adopted mandatory energy-efficiency requirements for ships.  

You can read the full text of the Initial Strategy here. An infographic which outlines key regulatory and implementation support steps as previously set out in the 2018 Initial IMO GHG strategy is available here. 

IMO climate events  

IMO hosts and co-organizes climate conferences and events to support implementation of the GHG strategy - see more information here.  


IMO contributes to international action led by the United Nations to address climate change, including by attending UN Framework Convention on Climate Change (UNFCCC) COP meetings. 

Read more here on IMO and UNFCCC and see links to IMO at COP

Latest figures on GHG emissions from shipping  

The IMO 4th GHG study (2020) provides the latest statistics on GHG emissions from shipping. Key findings and a link to download the full report are available here.  

See also:

IMO Data Collection System annual reports.

Study on the readiness and availability of low- and zero-carbon ship technology and marine fuels Summary report of the study

Mandatory energy efficiency requirements - what ships must do 

Under a framework developed as part of the 2018 Initial IMO Strategy on Reduction of GHG Emissions from Ships, technical and operational amendments to the International Convention for the Prevention of Pollution from ships (MARPOL) Annex VI require ships to improve their energy efficiency in the short term and thereby reduce their GHG emissions  

In simple terms, these measures are aimed at achieving the carbon intensity reduction aims of the Initial IMO GHG Strategy. 

On 1 January 2023 it became mandatory for all ships to calculate their Energy Efficiency Existing Ship Index (EEXI) and to establish their annual operational carbon intensity indicator (CII) and CII rating. In other words, ships get a rating of their energy efficiency (A, B, C, D, E – where A is the best). A ship running on a low carbon fuel gets a higher rating than one running on fossil fuel. 

There are many things a ship can do to improve its rating, such as hull cleaning to reduce drag; speed optimization; installation of low energy light bulbs; installation of solar/wind auxiliary power for accommodation services; etc. 

Read more about EEXI and CII ratings here. 

Alternative fuels 

Low- and zero-carbon fuels will be needed to decarbonize shipping. See the results of a future fuels mapping exercise here. 

There is great potential for developing countries to become key suppliers of low and zero carbon fuels for shipping. Read more here: IMO Symposium on alternative fuels. 

Potential future fuels and propulsion for shipping include ammonia, biofuels, electric power, fuel cells, hydrogen, methanol, and wind.  

For different fuel options, there is a need to consider issues such as safety, regulation, pricing, infrastructural availability, lifecycle emissions, supply chain constraints, barriers to adoption and more.  

Download a workshop package on alternative fuels here. The workshop considers potential production pathways, emission reduction potential, infrastructure and onboard requirements, as well as implications on cost. The overall aim is to better understand some of the possible alternative fuels in the future marine fuel mix and assess opportunities and any barriers to each option. 

IMO has adopted Guidelines on life cycle GHG intensity of marine fuels (LCA guidelines) - read more about these here). These allow for an assessment of greenhouse gas emissions from the fuel production to the ship (Well-to-Wake), from primary production to carriage of the fuel in a ship's tank (Well-to-Tank, also known as upstream emissions) and from the ship's fuel tank to the exhaust (Tank-to-Propeller or Tank-to-Wake, also known as downstream emissions). Work continues on the development of the Life Cycle GHG Assessment (LCA) framework. 

Candidate future low-carbon and zero-carbon fuels for shipping have diverse production pathways - for example, different generations of biofuels, hydrogen-based fuels - entailing significant differences in their overall environmental footprint. 

Future fuels and technology project

The Government of the Republic of Korea and IMO "Future fuels and technology for low-and zero-carbon shipping" project (FFT project), has completed a study to identify the state-of-play and projections regarding the global uptake and dissemination of low- and zero-carbon marine technology and fuels.

The project will further work on:

  • identifying and supporting possible incentives/regulatory mechanisms, including safety and training issues, to promote the uptake of low- and zero-carbon fuels and technology including mid-, long-term GHG reduction measures; and
  • promoting technical cooperation (e.g., pilot projects) and organizing outreach activities to reinforce mutual understanding and cooperation between developed and developing countries and global shipping industry.

Download Study on the readiness and availability of low- and zero-carbon ship technology and marine fuels Summary report of the study

Safety matters

The IMO Maritime Safety Committee (MSC) has included on its agenda, an output on "Development of a safety regulatory framework to support the reduction of GHG emissions from ships using new technologies and alternative fuels", starting with MSC 108 (mid-2024).

A correspondence group  has been established to: identify and update a list of fuels and technologies which will assist international shipping to support the reduction of GHG emissions from ships using new technologies and alternative fuels; conduct an assessment for each identified fuels and new technologies (e.g. the state of knowledge of risks and the technical considerations of solutions, Hazards and Risks, Risk Control Measures) in relation to persons, ships (new built and converted) and applicable operations for the same, from e.g. projects applying alternative design and approval process where permitted; based on the outcomes, develop a record for safety obstacles and gaps in the current IMO instruments that may impede the use of the alternative fuel or new technology; and submit a written report to MSC 108.

The IMO Sub-Committee on Carriage of Cargoes and Containers (CCC) has already been playing a vital role in the development of technical provisions for alternative fuels and related technologies, ensuring that safety implications and potential risks associated with the use of alternative fuels and related technologies are duly addressed. Guidelines already developed include: Interim guidelines for the safety of ships using methyl/ethyl alcohol as fuel (MSC.1/Circ.1621); Interim guidelines for ships using fuel cells (MSC.1/Circ.1647); interim guidelines for the safety of ships using LPG fuels (MSC.1/Circ.1666 ).

The following video outlines the importance of transitioning to low- and zero-carbon fuels and renewable energy sources to power ships:


Supporting innovation 

Shipping will undoubtedly need new technologies, new fuels and innovation to meet the GHG targets. There needs to be investment in R&D, infrastructure and trials. 

A range of IMO-executed projects is addressing this, focusing on supporting developing countries to implement MARPOL Annex VI energy efficiency measures and promoting trials and training.   

IMO climate action projects list:

Carbon capture and storage and marine geoengineering 

As the Secretariat for the London Convention and London Protocol, IMO regulates carbon capture and storage (CCS) beneath the seabed to mitigate the impacts of increasing concentrations of carbon dioxide (CO2) in the atmosphere, as well as ocean fertilization and other marine geoengineering activities. 

CCS is a technology that aims for the permanent isolation and storage underground (sequestration) of CO2. CCS has been regulated by the London Protocol since 2006.

In 2013, the London Protocol was amended to regulate ocean fertilization. This will, when in force, provide a legally binding mechanism to regulate the placement of matter for ocean fertilization, while also “future-proofing” the LP to enable regulation of other marine geoengineering activities that fall within its scope.   

An area of growing interest is that of onboard carbon capture (OCC). IMO's Intersessional Working Group is due to consider several proposals related to the technology and how its regulation might be accommodated within IMO's current regulatory framework. The Working Group hopes to provide advice on a way forward to the Marine Environment Protection Committee at its meeting in April 2024. 

Read more here on how global regulation can deal responsibly with climate change mitigation technologies to protect the marine environment.

Watch an interview with IMO Secretary-General, Kitack Lim (2021):


This video from 2021 explains IMO's role in cutting GHG emissions from shipping: