Shipping and climate change

Illustration of a blue ship with lots of smoke

This page gives an overview of the impact of shipping on climate change, and of measures that could reduce greenhouse gas (GHG) emissions. These include the International Maritime Organisation’s (IMO) Energy Efficiency Design Index (EEDI) for new ships, and measures to reduce fuel consumption such as limiting and reducing operational speed(s) of ships.

What is the impact of shipping on climate change?

The Third IMO GHG Study (2014) estimated that for the period 2007–2012, shipping emitted 1,000 Mt CO2, equaling approximately 3.1% of annual global CO2 emissions. The latest update to the study by CE Delft projects shipping emissions to increase by up to 120% by 2050 if other sectors decarbonise successfully. Under a business-as-usual scenario and if other sectors of the economy reduce emissions to keep global temperature increase below 2 degrees Celsius, shipping could represent some 10% of global GHG emissions by 2050.

What is the EEDI?

The IMO’s Energy Efficiency Design Index (EEDI), approved in July 2011, is the first globally-binding design standard aimed at abating climate change. It applies to (almost) all new ships and entered into force in 2013. The index requires new ships to become more energy efficient, with standards that will be made increasingly more stringent over time. Read our questions and answers on the IMO's EEDI.

How much more fuel efficient will EEDI ships have to be, and by when?

Different classes and sizes of ships will have different standards to meet. Standards are compared to the baseline, set as the average efficiency of ships built between 1999-2009.

  • Phase I: an overall 10% improvement target in vessel energy efficiency applies to new ships built between 2015 and 2019;
  • Phase II: ships built between 2020 and 2024 will have to improve their energy efficiency by 15 and 20%, depending on the ship type;
  • Phase III: Ships delivered after 2025 will have to be 30% more efficient;

Smaller ships have different efficiency requirements for each phase.

New ship designs less fuel-efficient than those built in 1990

Ships built in the first decade of the 2000s were, on average, less fuel-efficient than those built in the 1990s, according to the first ever study of the historical development of the design efficiency of new ships.

Aircraft and cars have become more fuel efficient, but despite a generation of technological improvements, ships have largely gone backwards for most of the past 25 years. The EEDI for new ships itself needs a revision and strengthening if the standard is not supposed to merely bring us back to levels achieved 25 years ago.

The most recent design efficiency data indicates that new ships built in 2013 were, on average, 10% less fuel-efficient than those built a quarter of a century ago. Bulk carriers, tankers, and container ships built in 2013 were on average 12, 8 and 8% less fuel-efficient than those built in 1990. The findings contradict the shipping industry’s narrative that it has been constantly improving its environmental performance. Market forces failed to result in more fuel-efficient ships being built. Oil prices in the late 1980s and early 1990s, the time when new ships were historically most fuel efficient, were around a quarter of the levels seen in the 2008-2013 period. Since 2013, however, the design efficiency of ships has improved considerably. Industry claims it is due to the EEDI but this cannot explain some of the extraordinary levels of over-compliance being seen: certain types of new ships over-comply with the 2025 Phase III EEDI requirements almost a decade in advance and sometimes by a factor of 2. Cyclical higher fuel prices and low freight rates are more likely to be the drivers leaving the EEDI lagging well behind. Although the current over-compliance is welcome news, without strengthening the EEDI news ships will likely be less efficient when market conditions (long-term fuel prices and freight rates) change.

EEDI standards too weak to drive improvements

IMO discussion has acknowledged that the EEDI is not stimulating the uptake of new technologies, nor is it driving efficiency improvements. Read the study here. Since 2013 newly-built ships subject to the EEDI have performed much the same as those not covered by the regulation.

At least two-thirds of containerships, half of general cargo ships and a quarter of tankers launched in 2015 already overshoot the requirement for 2020 without using innovative new technologies. This shows that the EEDI is not incentivising the uptake of new technologies – all it may do is prevent a reversion to the worst designs of the past. These recent efficiency gains are part of a recognised historical trend for ship design efficiency to fluctuate according to economic cycles and fuel prices.

The latest CE Delft study, incorporating 2016 data, confirms that a considerable number of ships in different ship categories and sizes continue to comply and over-comply with EEDI requirements – providing further evidence that the requirements need strengthening. The results, however, also suggest that recent improvements in ship design efficiency stalled in 2016, with the average design efficiency of new build bulk carriers, tankers and gas carriers in 2016 being worse than in 2015. 

While reducing design speed is a very effective way of improving the design efficiency of a ship, there has in fact only been a modest reduction in the average design speed of new vessels according to the data anlaysed (and that has largely been limited to container ships). Meanwhile the design efficiency of new vessels has improved considerably. With efficiency improvements via new technologies and speed reduction largely untapped, there remains considerable potential for further design efficiency improvements but these will not be taken up unless the IMO incentivises them through stricter EEDI requirements.

What is slow steaming?

Slow steaming refers to the practice whereby the (operational) speed of the ship is reduced. It basically means that the ship’s engine is not used at full power, thus saving fuel, reducing CO2 and air pollutant emissions.

Reducing ship speed by 10% will lead to a 27% reduction of the ship’s emissions. Overall, if all ships were to slow-steam, the available capacity on the market would be reduced (more ships would be needed to carry out the same transport work). If the additional emissions of building and operating these new ships were considered in the equation, then reducing the fleet’s speed by 10% would lead to overall CO2 savings of 19%.

What is the purpose of developing slow steaming?

Reducing the (operational) speed of ships multiplies the positive effects of an energy efficiency index, as it results in burning less fuel and therefore emitting less CO2 and other greenhouse gases. It also contributes to significantly lower emissions of air pollutants such as NOx and PM, with benefits greatly outweighing costs. Slow-steaming is often regarded as the most cost-effective way to reduce CO2 emissions as it can be done at almost no cost while translating into operational savings.

Is the industry already practicing slow steaming?

The industry started to slow steam in order to deal with the overcapacity resulting from the economic crisis and the subsequent drop in international trade. In a seminar organised in October 2011 by T&E and Seas at Risk, a representative of Maersk – the world's largest container shipping company – described how they had been successfully using slow steaming since 2007, decreasing their engines’ load by 35% without any technical problems for ship owners. On the contrary, slow steaming has brought about fuel savings and reduced costs for maintenance and operational issues. The Maersk representative also said that his company sees no technical problems in implementing so-called super-slow steaming, which would mean decreasing the engine power by up to 90%.

Is regulated slow steaming legally and technically enforceable?

The findings of the first ever study on the feasibility of regulated slow steaming indicate that it is technically possible and legally enforceable without any major administrative burden and at no cost for the shipping industry. The report – carried out by the Dutch consultancy CE Delft, and commissioned by T&E and Seas at Risk – showed that reducing the average operational speed of the world fleet can have dramatic reductions in global ship CO2 emissions even after taking into account the need to build and operate additional ships to deliver the same amount of transport work. Slow steaming could be enforced globally using the Automatic Identification System (AIS), already mandatory on all large ships, since it provides real time information on the ship’s location, speed and direction. It is therefore impossible to cheat the system.