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Greenhouse gas emissions from international shipping activities currently account for 3% of global emissions. Without rapid action to decarbonise the sector, these emissions are likely to grow in the coming decade. Although seen as a challenging to decarbonise sector, the UK Government has recently included shipping in its sixth carbon budget, starting in 2033. As a result, the UK’s share of the sector has become part of the goal to reach net zero emissions by 2050.  

The two main approaches to reduce emissions are either to improve efficiency or to replace heavy fuel oil or marine diesel with low-carbon alternatives. A variety of measures and technologies are currently available to increase the efficiency of shipping activities and provide short-term emission reductions. This includes design improvements, route optimisation and wind-assisted technologies. However, uncertainty around the reliability of these options and structural factors specific to the sector currently limit their use.  

To achieve full decarbonisation in the long term, a switch to zero or net zero emissions fuels or drive systems will be required. A number of low-carbon fuels are currently in commercial use, such as LNG or biofuels, but their scalability and compatibility with a net zero goal have been called into question by many stakeholders. Several zero and net zero emissions fuels and technologies are currently under development, such as electrofuels, green hydrogen and ammonia. However, these will require significant investment and policy interventions to drive infrastructural development and uptake in commercial vessels. 

International shipping is governed by the International Maritime Organization (IMO). The IMO currently has a target of at least a 50% reduction in GHG emissions by 2050, compared to 2008 levels. This target has been widely criticised for a lack of ambition and a variety of stakeholders, including the UK, support a net zero by 2050 goal for the sector. In 2023, the IMO will revise its GHG strategy, which will include mid- and long-term measures to decarbonise the sector and a likely tightening of the 2050 target. 

Key points  

  • International shipping is responsible for 3% of global greenhouse gas (GHG) emissions.   
  • The sector is difficult to decarbonise owing to the long lifetime of ships, the complex network of actors in the sector and uncertainty around low-carbon technologies.  
  • Options are available for short-term reductions in GHG emissions but a transition to zero-emissions technologies will be required to fully decarbonise the sector.  
  • A number of zero-emissions fuels and drive systems are currently being developed.  
  • Emissions from international shipping are primarily regulated by the International Maritime Organization (IMO).
  • The IMO’s GHG targets are to be revised in 2023 and will need to be strengthened to meet the Paris Climate Agreement. 


POSTnotes are based on literature reviews and interviews with a range of stakeholders and are externally peer reviewed. POST would like to thank interviewees and peer reviewers for kindly giving up their time during the preparation of this briefing, including: 

  • Department for Transport*
  • Maja Dittel, European Commission, Climate Action
  • Eoin Devane, Climate Change Committee
  • Carolina Dopico-Gonzalez, Maritime and Coastguard Agency
  • John Booth, Maritime and Coastguard Agency
  • Thomas Skew, Maritime and Coastguard Agency
  • Rory Megginson, CORE POWER
  • Giulio Gennaro, CORE POWER
  • Bud Darr, Mediterranean Shipping Company*
  • Stewart Inglis, Mediterranean Shipping Company*
  • Dr Yuan Ruoyang, University of Sheffield and Supergen Bioenergy Hub
  • Prof Patricia Thornley, Aston University and Supergen Bioenergy Hub
  • Dr Andrew Welfle, University of Manchester and Suergen Bioenergy Hub
  • Dr Joanna Sparks, University of Aston and Supergen Bioenergy Hub
  • Sofia Frstenberg Scott, Fürstenberg Maritime Advisory
  • Conor Frstenberg Scott, Fürstenberg Maritime Advisory
  • Diane Gilpin, Smart Green Shipping Alliance*
  • Kay Tigges, Siemens Energy
  • Michael Welch, Siemens Energy*
  • Dr Tristan Smith, UCL Energy Institute*
  • Dr Nishatabbas Rehmatulla, UCL Energy Institute*
  • Gareth Giles, University of Southampton
  • Dr Wassim Dbouk, University of Southampton*
  • Prof Stephen Turnock, University of Southampton*
  • Prof Dominic Hudson, University of Southampton*
  • Dr Simon Bullock, Tyndall Centre, University of Manchester*
  • Prof Alice Larkin, Tyndall Centre, University of Manchester*
  • Prof Alan Mckinnon, Keuhne Logistics University*
  • Dr Alan Murphy, University of Newcastle
  • Prof Peilin Zhou, University of Strathclyde
  • Dr Paul Balcombe, Queen Mary University of London
  • Natasha Brown, International Maritime Organization*
  • Jesse Fahnestock, Global Maritime Forum
  • Anna Zhou, UK Chamber of Shipping*
  • Simone Bennett, International Chamber of Shipping
  • Eirik Nyhus, DNV*
  • Dr Carlo Raucci, Lloyd’s Register
  • Richard Westgarth, MarRI-UK and BMT* 

* denotes people and organisations who acted as external reviewers of the briefing  

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