In 2023, the International Maritime Organization (IMO) adopted a revised strategy that aims to reduce greenhouse gas (GHG) emissions from international shipping to net-zero by or around 2050. The strategy includes indicative checkpoints targeting a 20% reduction in GHG emissions by 2030 (striving for 30%) and a 70% reduction by 2040 (striving for 80%), both measured against 2008 levels. While these targets align with a well-below 2 °C pathway, defined as 1.7 °C by the ICCT, they fall short of limiting warming to 1.5 °C. Ultimately, it is the cumulative emissions until net-zero is achieved that will determine shipping’s contribution to future global warming.
The IMO has already implemented short-term technical and operational measures to improve the GHG intensity of ships, and is now developing mid-term measures, including a global fuel standard (GFS) and an economic measure such as a GHG levy to close the price gap between fossil and renewable fuels. Together, these measures can result in additional operational efficiency improvements that make it easier to achieve the 2030 and 2040 targets. These mid-term measures are expected to be finalized by April 2025 and could enter into force in 2027.
This report is a gap analysis, detailing the reduction in the global average GHG fuel intensity (GFI) and the operational efficiency improvements that would be necessary for the IMO to achieve its climate goals.
In this study, we model three decarbonization scenarios:
- IMO Minimum: The GHG emissions from international shipping decline by 20% by 2030 and 70% by 2040 compared with 2008 emission levels, and the sector achieves net-zero emissions by 2050.
- IMO Striving: The GHG emissions from international shipping decline by 30% by 2030 and 80% by 2040 compared with 2008 emission levels, and the sector achieves net-zero emissions by 2050.
- 1.5 °C: Cumulative GHG emissions from international shipping are below the shipping sector’s proportional share of the carbon budget that aligns with a 67% chance of limiting warming to 1.5 °C.
The analysis estimates cumulative emissions from 2020 to 2050 and compares them with shipping’s proportional share of global carbon budgets for 1.5 °C, 1.7 °C, and 2°C warming scenarios. Emission reductions are achieved by either reducing the global average GFI of marine fuels alone, or by combining the GFI reduction with operational efficiency improvements.
Key findings
We find that the global shipping sector is on a trajectory to exhaust its proportional 1.5 °C carbon budget by 2030, its 1.7 °C budget by 2037, and its 2 °C budget by 2047. Mid-term measures aligned with the targets in the IMO Minimum or IMO Striving scenarios could achieve cumulative emissions that are consistent with limiting warming to 1.7 °C. As illustrated in Figure 1, projected operational efficiency improvements resulting from the IMO mid-term measures could reduce cumulative emissions by about 10% between 2020 and 2050. The remaining 90% will require replacing fossil fuels with net-zero GHG fuels or energy on a life-cycle basis, which can only be achieved by advanced technologies that have not yet been fully commercialized.
Reducing the global average GFI using the GFS would require that the regulation, and the guidelines used to implement it, accurately account for the well-to-tank and tank-to-wake GHG emissions of marine fuels and prevent the use of food- and feedbased biofuels. It would also require an unprecedented level of financial investment in the nascent and pre-commercial technologies necessary to produce genuinely zero-carbon fuels.
If the real-world well-to-wake GHG intensity of the fuel mix used to satisfy the GFS requirements is not accurately accounted for, then the life-cycle GHG emissions from shipping will be higher than implied by the policy. To bridge this gap, regional and national governments would need to implement their own policies to regulate the GHG intensity of the fuels ships use on voyages to, from, or between their ports. These policies would need to be considerably more ambitious than current international best practices, as contained in the FuelEU Maritime regulation.
The results indicate that achieving the IMO’s GHG emission reduction targets will necessitate unprecedented ambition in GFS requirements and economic measures that ensure an effective carbon price signal. In addition, these mid-term measures should promote the use of scalable zero-emission fuels that can bring meaningful climate benefits: renewable hydrogen-based e-fuels. The findings underscore the urgency of finalizing and implementing these policies to align shipping with global climate goals.
Source: ICCT
