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ICCT study finds GHGs from shipping on the rise

Emissions of greenhouse gases (GHGs) from global shipping are on the rise again, according to a new study released by the International Council on Clean Transportation (ICCT). Overall, the study found that maritime fuel consumption increased from 291 to 298 million tonnes (+2.4%) from 2013 to 2015, compared to a 7% increase in shipping transport work. Accordingly, CO2 emissions from global shipping (oceangoing vessels, domestic ships, and fishing vessels) increased from 910 to 932 million tonnes over the same period.

The report notes that these increases in GHG emissions are being driven by the rising demand for shipping and, as a result—despite improvements in operational efficiency for many ship classes—by the increased consumption of fossil fuels.

The ICCT has submitted the report to the IMO’s second GHG intercessional meeting (ISWG-GHG-2), which meets next week in London to continue to develop the structure and to identify core elements of the draft initial IMO Strategy on reduction of GHG emissions from ships. (The planned third intercessional meeting in April 2018 is to finalize the draft IMO GHG strategy.)


The new ICCT study combines global ship operations (AIS) data with detailed vessel characteristics for more than half a million ships to estimate GHG emissions and air pollution from shipping at high resolution (1° x 1°) on an hourly basis for the years 2013 to 2015.

The study highlights that three ship classes and six flag states (country of registration) are responsible for the majority of emissions.

  • Container ships (23%), bulk carriers (19%) and oil tankers (13%) accounted for more than half of CO2 emissions.

  • Ships registered to Panama (15%), China (11%), Liberia (9%), Marshall Islands (7%), Singapore (6%), and Malta (5%) were the largest emitters. These flags account for 66% of the global shipping fleet’s deadweight tonnage.

Share of CO2 emissions by ship class (left) and flag state (right), 2013–2015. Source: The ICCT. Click to enlarge.

Shipping fuel consumption was dominated by residual fuels—72% of total shipping fuel consumption in 2015. Distillate fuel accounted for approximately one quarter of fuel consumption, with LNG representing approximately 2% of fuel consumption. Similar proportions of residual, distillate, and LNG fuel consumption were observed for 2013 and 2014.

One contributing factor to the trend of increasing fuel consumption is that the biggest ships are speeding up and emitting more. While average speeds remained largely flat between 2013 and 2015 for most ships, the largest oil tankers (>200,000 dwt) and container ships (>14,500 TEU) increased their cruising speed over ground (SOG) nearly 4% and more than 11%, respectively.

Even in cases in which a ship class became much more efficient, their CO2 emissions increased. For example, although the CO2 intensity of general cargo ships decreased by 5%, CO2 emissions increased by 9%; increases in distance traveled due to a greater demand for shipping more than offset gains in operational efficiency during the period studied.

Only refrigerated bulk carriers managed to reduce their CO2 emissions by a greater percentage than they reduced their CO2 intensity, owing to a 5% drop in overall supply for these ships from 2013 to 2015. The disconnect between CO2 intensity and total emissions suggests that business as usual improvements in energy efficiency are unlikely to yield substantial reductions in CO2 emissions from ships.

—ICCT report

The International Council on Clean Transportation (ICCT) 2
Change in CO2 emissions and CO2 intensity for key ship classes. The ICCT. Click to enlarge.

The study also identifies black carbon as the second most important climate pollutant after CO2, representing between 7% to 21% of the total climate impact of shipping.

This study shows that business as usual improvements in shipping efficiency will not be enough to reduce GHG emissions from ships. Concerted action is needed from IMO to promote low and even zero carbon technologies if the shipping industry is to pull its weight in protecting the global climate.

—Dan Rutherford, the ICCT’s program director for marine and co-author

The shipping industry is a major emitter of greenhouse gases. If it were a country, the global marine transportation sector would have ranked 6th in terms of CO2 emissions in 2015, just below Germany and well above Korea. Marine CO2 emissions are projected to double by 2050 as international trade expands unless effective policies are developed to constrain emissions growth. International shipping was not included in the 2015 Paris climate agreement.



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