Mitigation of CO2 Emissions from International Shipping through National Allocation

International ships carry roughly 90 percent of global trade by volume and produce more CO₂ emissions annually than Saudi Arabia, at two percent of of global emissions.

Despite this, neither international treaties nor domestic policies control CO₂ emissions from international maritime shipping. The industry also does not lend itself to easy governance, as it is global in nature, is intrinsically tied to the global economy and contains opaque webs of ownership sometimes spanning multiple continents for one vessel.

The world’s countries have delegated the control of CO₂ emissions from international vessels to the International Maritime Organization (IMO), but after two decades of discussion, the forum has done little beyond implementing mandatory efficiency standards. Despite gains in efficiency, emissions may increase by up to 50 percent by 2050 unless further action is taken.

In a new journal article published in Environmental Research Letters, Henrik Selin, Yiqi Zhang, Rebecca Dunn, Noelle E. Selin and Alexis K. H. Lau discuss how mitigation of CO₂ emissions from international shipping could be mitigated by allocating these emissions to countries based on the location of a shipping actor, assessing five potential allocation options.

In the context of achieving the Paris Agreement, the authors analyzed five national allocation options and, for the first time, used spatially resolved data to understand how each option might impact national carbon budgets.

Their results found that a clear majority of CO₂ emissions could be distributed to ten countries under each of the allocation options examined, but that the top ten countries varied across allocation options, as did the impacts to countries’ carbon budgets. China and the United States would see less than a percent increase to their carbon budgets across all options, whereas the amount of CO₂ emissions allotted to other countries could increase their carbon budgets thousand-fold or more. Countries within the Organization for Economic Co-operation and Development (OECD) would receive the majority of CO₂ emissions under three of the options the authors looked at, whereas non-OECD countries would receive the most CO₂ emissions under two of the options.

Based on an analysis of objectives, principles for decision making and geographical coverage of both the United Nations Framework Convention on Climate Change (UNFCCC) and the IMO, the authors concluded there are strong reasons for the UNFCCC to implement any future allocation scheme. They also highlighted that allocating CO₂ to the “owner country” best meets the criteria related to equity and effectiveness.

While any allocation option may be politically difficult, the authors explain it is critical to address all CO₂ emissions sources in order to meet the Paris Agreement’s temperature goals, which seeks to limit global average temperature increases to well below 2°C above pre-industrial levels (and to pursue efforts to limit them to 1.5°C.

New and more ambitious measures are needed to help countries meet their individual and global climate commitments.

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