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 emissions. These include the International Maritime Organisation's Energy Efficiency Design Index (EEDI) for new ships, and measures to reduce fuel consumption such as reducing the speed of ships.

What is the impact of shipping on climate change?

The Third IMO greenhouse gas study estimates that for the period 2007–2012, on average, shipping accounted for approximately 2.7% of annual global CO2 and the study's scenarios project an increase of 50-250% in the period up to 2050.

Shipping CO2 emissions already increased by approximately 70% since 1990. Under a business-as-usual scenario and if other sectors of the economy reduce emissions to keep global temperature increases below 2 degrees Celsius, shipping could represent a whopping 10% of global GHG emissions by 2050.

What is the EEDI?

The Energy Efficiency Design Index (EEDI), approved in July 2011 by the International Maritime Organization (IMO), is the first globally-binding climate change standard. It applies to 180 states and  entered into force on 1 January 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 of ship will have different standards to meet. However:

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

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

New ships are on average less fuel-efficient than those built in 1990, 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 redesign 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 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.

EEDI standards too weak to drive improvements

EEDI standards are not stimulating the uptake of new technologies or 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.

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 standard will not encourage 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.

While reducing design speed is a very effective way of improving efficiency, there has only been a modest reduction in the average design speed of new vessels, and that is largely limited to container ships. 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 a stricter EEDI requirement.

What is slow steaming?

Slow steaming refers to the practice whereby the 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 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 speed of ships multiplies the positive effects of an energy efficiency index, as it makes them burn less fuel and therefore emit less CO2 and other greenhouse gases. It would also contribute to significantly cut their 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 costs and translate into savings for the operators.

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 have successfully been 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 consultant CE Delft, the University of Southampton and the International Council on Clean Transportation (ICCT) and commissioned by T&E and Seas at Risk - recommends that a global speed limit for shipping be implemented with an international agreement to reduce the risk of retaliation. Read our briefing about this.