International shipping is commonly considered the most efficient and lowest-carbon transport mode, and is also seen as having significant potential remaining to reduce emissions still further. This assessment, performed by researchers at the University College London as part of the International Council on Clean Transportation’s World Shipping Efficiency Indices project, seeks to quantify just how efficient ships are as they move goods around the world to better understand how some ship owners are achieving lower climate impacts. It is the first study to utilize global satellite Automatic Identification System (AIS) data on ship movement to assess the detailed variation in technical and operational efficiency and carbon emissions across all international shipping vessels.
The analysis indicates that new ships with high technical efficiency—as promoted by the Energy Efficiency Design Index standards—is translating to more efficient vessels in real-world operating conditions. Yet there is wide variation in ships’ operational efficiency and carbon emissions, driven primarily by factors like ship speed. Including technical and operational differences, the top 5% most efficient cargo-hauling vessels achieve greater than a 50% reduction in carbon intensity (in grams of CO2 emitted per ton-mile) from the industry average, although the results differ somewhat for each of the nine analyzed ship types (e.g., container, tanker, dry bulk, gas). The assessment also reports more generally on the strengths and limitations of using satellite ship movement data for future work.