IMO’s work to cut GHG emissions from ships


Acting to cut emissions from ships

IMO adopted the first set of international mandatory measures to improve ships' energy efficiency  on 15 July 2011. In the past decade, IMO has taken further action, including further regulatory measures and the adoption of the Initial IMO GHG strategy. To support their implementation, IMO has been executing a comprehensive capacity building and technical assistance programme, including a range of global projects.

Video interview with IMO Secretary-General Kitack Lim (14 September 2021)Cutting GHG emissions from shipping - IMO's role (14 September 2021)

Download the infographic outlining key regulatory and implementation support steps. You can download a high resolution version of this infographic by clicking on it and then saving the file.


IMO was present at the United Nations climate conference COP 27 (6-18 November). IMO organized, in collaboration with UNCTAD, IRENA and the World Bank, a side-event on 10 November during COP 27 on exploring opportunities for developing States in renewable fuel production for the maritime industry (18:30, 10 November, Akhenaten). Read more about the side-event here.

IMO was at COP 26 in November 2021. Read more on IMO at COP 26 here. 

2018 Initial IMO GHG Strategy

The IMO Initial Strategy on the reduction of GHG emissions from shipping sets key ambitions. This is a policy framework. The main goals are:

  • Cut annual greenhouse gas emissions from international shipping by at least half by 2050, compared with their level in 2008, and work towards phasing out GHG emissions from shipping entirely as soon as possible in this century. 
  • The Initial 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, pursuing efforts towards 70% by 2050, compared to 2008. 

The Initial Strategy will be revised by 2023.

Read more detail about the strategy here.   

Download the full text of the IMO Initial GHG Strategy here

Meeting the goals

The Initial GHG Strategy includes a series of candidate short-, mid- and long-term measures, building on already-adopted mandatory energy-efficiency requirements for ships.

Some have already been addressed.

Since the adoption of the Strategy, IMO has approved a Programme of follow-up actions of the Initial Strategy up to 2023 and made good progress with the consideration and implementation of some of the short-term GHG reduction measures included in the list of candidate measures.

These include:   

  • adoption of MEPC resolution to invite Member States to encourage voluntary cooperation between the port and shipping sectors to contribute to reducing GHG emissions from ships (resolution MEPC.323(74));
  • approval of the Procedure for assessing impacts on States of candidate measures (MEPC.1/Circ.885);
  • further improvement of the existing energy efficiency framework with a focus on EEDI and SEEMP, in particular by adoption of the amendments to MARPOL Annex VI on the early application of the EEDI Phase 3 requirements for certain ship types, which will enter into force in April 2022 (resolution MEPC.324(75));
  • adoption of the MEPC resolution on Encouragement of Member States to develop and submit voluntary national action plan to address GHG emissions from ships (resolution MEPC.327(75)) - see submitted national action plans here;
  • adoption by MEPC 76 of amendments to MARPOL Annex VI on the short-term goal-based carbon intensity reduction measure setting out technical and operational energy efficiency measures for ships (EEXI and CII - ship carbon intensity rules and rating system); together with approval of a comprehensive impact assessment;
  • commissioning, oversight and approval of the Fourth IMO GHG Study 2020;
  • initial development of life cycle GHG assessment guidelines by the Intersessional Working Group on Reduction of GHG Emissions from Ships (ISWG-GHG) – read more here;
  • initial consideration of other candidate measures listed in the Initial Strategy, including proposal for the establishment of an International Maritime Research Board to coordinate and oversee R&D efforts; and
  • continued and enhanced technical cooperation and capacity-building activities,  including the establishment of a voluntary multi-donor trust fund to sustain the Organization's technical cooperation and capacity-building activities to support the implementation of the Initial Strategy ("GHG-TC Trust Fund").

Mid-term GHG measures

MEPC 76 in June 2021 adopted a work plan on the concrete way forward to make progress with candidate mid- and long-term measures, including measures to incentivize the move away from fossil fuels to low- and zero-carbon fuels to achieve decarbonization of international shipping. Read more here.

Outcome of Intersessional Working Group (ISWG -GHG 10) here.

Support for developing countries

The Strategy promotes support for developing countries, especially small island developing States (SIDS) and least developed countries (LDCs). Read more below.

Review of the Strategy

IMO Member States have pledged to revise the Strategy in 2023.

Latest figures on GHG emissions from shipping 

The latest statistics can be found in the IMO 4th GHG study (2020)  - overview and download here.

Mandatory energy efficiency requirements - what ships must do

  • In 2011, IMO agreed to include a new chapter on "energy efficiency" in MARPOL Annex VI and adopted mandatory energy efficiency regulations for ships – Energy Efficiency Design Index (EEDI) for new ships, Ship Energy Efficiency Management Plan (SEEMP) for all ships.
  • The EEDI has subsequently been strengthened through further amendments.
  • In 2016 IMO adopted the mandatory IMO Data Collection System (DCS) for ships to collect and report fuel oil consumption data from ships over 5,000 gt  - first calendar year data collection completed in 2019.
  • A range of IMO-led global projects initiated since 2012 support developing countries in ratifying MARPOL Annex VI and to implement the energy efficiency measures and to support and encourage pilot projects, innovation and R&D.
  • In 2020, the IMO 2020 0.50% sulphur limit entered into force – cutting total sulphur oxide emissions from shipping by over 75%.
  • In June 2021, IMO adopted short-term measures to reduce carbon intensity of all ships by 40% by 2030, compared to 2008.

Short term measure to cut carbon intensity

The short-term measure is aimed at meeting the target set in the IMO Initial GHG Strategy – to reduce carbon intensity of all ships by 40% by 2030, compared to 2008. These will be mandatory measures under MARPOL Annex VI. They will bring in 

  • Attained Energy Efficiency Existing Ship Index (EEXI) is required to be calculated for ships of 400 gt and above, in accordance with the different values set for ship types and size categories. This indicates the energy efficiency of the ship compared to a baseline. Ships are required to meet a specific required Energy Efficiency Existing Ship Index (EEXI), which is based on a required reduction factor (expressed as a percentage relative to the EEDI baseline).  
  • Annual operational carbon intensity indicator (CII) and CII rating.

In simple terms, the short-term term measure are aimed at achieving the carbon intensity reduction aims of the IMO initial GHG Strategy.

They do this by requiring 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 clearly gets a higher rating than one running on fossil fuel.

Read more: FAQ on the EEXI and CII. 

Watch the video: Cutting GHG emissions from shipping - IMO's role (14 September 2021)

There are many things a ship can do to improve its rating through various measures, 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.



Asessment of possible impacts of candidate measures on States

The initial strategy recognizes that the impacts on States of a measure should be assessed and taken into account as appropriate before adoption of the measure. Particular attention should be paid to the needs of developing countries, especially small island developing States (SIDS) and least developed countries (LDCs). When assessing impacts on States the impact of a measure should be considered, as appropriate, inter alia, in the following terms:

  1. geographic remoteness of and connectivity to main markets;
  2. cargo value and type;
  3. transport dependency;
  4. transport costs;
  5. food security;
  6. disaster response;
  7. cost-effectiveness; and
  8. socio-economic progress and development.

Disproportionately negative impacts should be assessed and addressed, as appropriate.

MEPC 74 (May 2019) approved the Procedure for assessing impacts on States of candidate measures for reduction of GHG emissions from ships. The procedure identifies four steps:

  • Step 1: initial impact assessment, to be submitted as part of the initial proposal to the Committee for candidate measures;
  • Step 2: submission of commenting document(s), if any;
  • Step 3: comprehensive response, if requested by commenting document(s); and 
  • Step 4: comprehensive impact assessment, if required by the MEPC.

Impact assessments should be evidence-based and should take into account, as appropriate, analysis tools and models, such as, cost-effectiveness analysis tools, e.g. maritime transport cost models, trade flows models, impact on Gross Domestic Product (GDP); updated Marginal Abatement Cost Curves (MACCs); and economic trade models, transport models and combined trade-transport models.

Alternative Fuels

Low and zero-carbon fuels will be needed to decarbonise shipping. There is great potential for developing countries to become key suppliers of low and zero carbon fuels for shipping. (Read more here:  Symposium on alternative fuels.)

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. 

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

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 potential alternative fuels in the future marine fuel mix, and assess opportunities and barriers of each option.

We  know that the whole lifecycle needs to be looked at. A candidate measure in the IMO Initial GHG Strategy refers to developing "robust lifecycle GHG/carbon intensity guidelines for all types of fuels, in order to prepare for an implementation programme for effective uptake of alternative low-carbon and zero-carbon fuels".

The lifecycle refers to the 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).

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

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 are addressing this, focusing on supporting developing countries to implement MARPOL Annex VI energy efficiency measures and promoting trials and training.  

Some examples include:

  • The European Union-funded GMN MTCC project has pilot projects ongoing. One in the Pacific has installed solar panels on a ferry - leading to fuel savings of 32% in operation and 87% reduction in GHG emissions at anchor. Other examples include collecting and analysing ship fuel consumption data; helping to improve ship trim optimization; developing technology needs assessments; and carrying out port energy audits. Data from pilot projects is shared to facilitate scaling up and roll out elsewhere.
  • The Global Industry Alliance (GIA) to Support Low Carbon Shipping has developed a Just-in-Time guide.  Watch the video animation 
  • The GIA has launched a free to access E-Learning course aimed at seafarers and anyone interested in this aspect of shipping. Access the course here: Course: Introductory Course on Energy Efficient Ship Operation ( self-paced course, 'An Introduction to Energy Efficient Ship Operation' is intended as a first glimpse into how GHG emissions from ships can be addressed. 
  • The GreenVoyage2050 project has launched a workshop package on 'Alternative fuels and energy carriers for maritime shipping' – Download here  - Workshop Packages: GreenVoyage2050 ( 

Climate action projects list

Carbon capture and storage and marine geoengineering

IMO’s work on climate change extends beyond shipping. 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.  

Read more: The London Protocol and London Convention - How global regulation can deal responsibly with climate change mitigation technologies to protect the marine environment.