Summary - In IMO’s fourth greenhouse gas (GHG) study, a consortium headed by research establishment CE Delft has found that GHG emissions from global shipping are growing and are expected to continue to increase.

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Greenhouse gas (GHG) emissions from shipping have increased by nearly 10% from 2012 to 2018 – growing from 977M tonnes in 2012 to 1.1Bn tonnes. Over 90% of shipping’s GHG emissions during the period have come from carbon dioxide (CO2) emissions. However, methane emissions have increased by 151% over the period studied.

University Maritime Advisory Services (UMAS), which led the work on the emissions inventory, said the growth of methane emissions in the sector far exceeds the use of LNG as a marine fuel and partly attributed the increase to the use of dual-fuel reciprocating engines with high levels of methane slip.

The study projected that overall emissions from the maritime sector could increase by as much as 50% through 2050, relative to 2018 levels. The increase is expected to happen alongside demand growth in goods transportation and despite expected efficiency gains. Further, UMAS said that while the Covid-19 pandemic will cause a decline in emissions this year, the decline is not expected to significantly affect the study’s projections.

Satellite tracking established an inventory of emissions for 2012-2018 which helped in estimating the GHG emissions for each ship in the global fleet, on every voyage sailed. 316M tonnes of the total 1.1Bn tonnes of shipping CO2 emissions (2.9% of total anthropogenic emissions) were within national emissions responsibilities. UMAS said advances in this new study’s methods estimated that 30% of total shipping emissions fall directly within a national government responsibility, twice the magnitude previously estimated. “The study shows strong, clear policy action must be taken for the sector to urgently transition away from the use of fossil fuels.”

UMAS director Tristan Smith said most countries count shipping emissions inaccurately, on the basis of fuel sold to shipping as opposed to actual voyages and activity. This is at odds with IPCC-aligned methods. Mr Smith said poor GHG accountancy can create “persistent underestimation” of the problem.

“Hopefully this study will encourage countries to look again, and bring shipping firmly into their national GHG policy, hydrogen strategies and action,” he said.

IPCC guidelines state that IMO is responsible for shipping emissions that occur when ships sail on a voyage between two countries. In case of a voyage between two ports in the same country, the emissions are the responsibility of that country – and should be accounted for and have reductions managed within that country’s emissions inventory and commitments.

UMAS leader of the emissions inventory work Elena Hauerhof said this marked the first time a study used “a fully IPCC-aligned approach to estimate international shipping emissions.” She added “The study has also significantly advanced the accuracy of AIS-based estimations for any ship, and evidences this by undertaking a detailed validation against fuel consumption and other key parameters reported in EU MRV for over 9,000 ships."

The study was a collaboration between nine organisations from six countries: CE Delft, ClassNK, UMAS, University College London, Dalian Maritime University, Fudan University, Institute of Economic Research Foundation, University of São Paulo, Manchester Metropolitan University, National Maritime Research Institute, National Institute of Maritime, Port and Aviation Technology, Purdue University and The International Council on Clean Transportation.

The report can be accessed in full here and answers to frequently asked questions prepared by UMAS can be found here.