Today the OECD has released experimental estimates for CO2 emissions from global shipping.1 The new database contains monthly figures for CO2 emissions by type of ship and by country. The estimates were developed using a near-real time data source derived from location tracking devices used for maritime vessels, including all types of ships making international voyages. The data from these devices feeds into a ship-tracking dataset, known as the Automatic Identification System (AIS), which was developed by International Maritime Organization (IMO) of the United Nations (UN) and is available on the UN Global Platform.2 Allocation to countries in the database is based on the residence of the companies that operate the ships.3
Researchers at the OECD developed a model to predict CO2 emissions for each vessel in the global shipping fleet. These estimates can be used to calculate total CO2 emissions for global shipping. In 2022, there were an estimated 858 million tonnes of CO2 emissions globally from the shipping industry, compared with 739 million tonnes of CO2 emissions from air transport (domestic and international flights); and 63% of emissions from global shipping came from vessels operated by companies based in OECD countries.
The AIS data is collected from onboard transmitters approximately every 6 seconds and is available from January 2019. The results from the OECD’s estimation model show that around half of total emissions are from container ships and bulk carriers and another one-fifth are from the transport of fossil fuels (oil and liquefied natural gas tankers). The smaller types of maritime vessels (cruise ships, for example) have relatively little impact on the total emissions (Figure 1).
Emissions during the COVID-19 pandemic
The OECD’s estimation model starts from the year before the COVID-19 pandemic. The impact of the pandemic on CO2 emissions from global shipping can be seen in March-April 2020 and the following months (Figure 2). The impact varied according to ship type. Cruise ships were particularly affected, and this is reflected in the sharp fall in emissions in March and April 2020. Cruises continued to suffer throughout the pandemic and emissions from cruise ships only reached pre-pandemic levels again in the mid-year high season of 2022. On the other hand, container ships were less affected at the start of the pandemic, and by August 2020 their emissions had returned to the levels recorded in January.
The trend for total CO2 emissions from global shipping is driven by large vessels such as container ships. By contrast with global CO2 emissions from air transport, which fell by 46% between 2019 and 2020 and remained 21% below 2019 levels in 2022, total CO2 emissions from global shipping fell by only 4% in 2020, and by 2022 they were 2% higher than in 2019.
- The scope of ‘global shipping’ is maritime (seagoing) vessels above 300 gross tonnage transporting people and cargo, excluding some fishing vessels; it may include some large ships on inland waterways.
- https://unstats.un.org/wiki/display/AIS/AIS+data+at+the+UN+Global+Platform
- The OECD’s country-level estimates are based on the residence principle, which is used both in national accounting and in the System of Environmental-Economic Accounting (SEEA). Results may differ from the official estimates produced by countries for the SEEA Air Emission Accounts because of differences in methods for compiling the estimates.
