International Shipping

The CAT rates the 2030 'indicative checkpoint' emissions reduction goal of 20% below 2008 levels as “Insufficient”, indicating that the target is consistent with limiting warming to between 2°C and 3°C, if all other sectors were to follow the same approach as international shipping.

Our rating is based on the CO₂ emissions level only.

If the IMO were to achieve the 30% reduction in emissions it is “striving for” in its 2023 Revised Strategy, this would improve the 2030 rating to “Almost Sufficient”. The 2030 carbon intensity target (40% reduction) falls in the ‘Insufficient’ rating.

The CAT rates 2030 emissions under the current level of policy action as ‘Highly insufficient’, indicating that the target is consistent with limiting warming to between 3°C and 4°C, if all other sectors were to follow the same approach.

It is not possible to quantify or rate the net zero GHG target due to an imprecise timeframe (“by or around 2050”) and lack of information on residual emission levels. Any remaining emissions would otherwise need to be counterbalanced by other means such as biofuels and carbon capture.

A real zero emissions target for international shipping for 2050 would be 1.5°C compatible.

To rate the international shipping and international aviation sectors, we start with the observation that to achieve the Paris Agreement’s temperature goal, global CO₂ emissions need to reach net-zero around mid-century (IPCC, 2018, 2023). If the shipping and aviation sectors decarbonise later than mid-century, other sectors will need to reach net-zero carbon emissions sooner, and/or deployment of corresponding negative emission technologies will be needed.

To reflect that different sectors should share the decarbonisation burden, we applied the principle that international shipping should decarbonise at the same average rate as emissions from energy and industrial processes, thereby taking a comparable share of emissions efforts. This implies these sectors (together with all emissions from energy and industrial processes) should reach zero CO₂ emissions by around 2060.

We have taken the global CO₂ emission pathways for energy and industrial processes provided by the IPCC Integrated Assessment Models (IAMs) using the latest AR6 scenario database. We filtered these pathways to exclude those that exceed sustainability limits for Bioenergy with Carbon Capture and Storage (BECCS) and Agriculture, Forestry and Other Land Use (AFOLU), as defined by (Fuss et al., 2018). This gave us 23 scenarios that are consistent with the Paris Agreement and that we define as “CAT Filtered Pathways” (Climate Analytics, 2023). This is the same filtering approach that we used for developing the domestic action rating used in individual country assessments. In our previous assessment, we used the IPCC Special Report (SR1.5) scenario database.

We have also extracted pathways that lead to a temperature increase between 1.5˚C-2˚C; between 2˚C-3˚C; between 3˚C-4˚C; and >4˚C from the IPCC IAM database, so we have five sets of pathways that correspond to each temperature category.

From each pathway set, we took the median emission levels between 2010 and 2100, in ten-year intervals. Using these median levels, we calculated the annual growth rate for each temperature pathway and applied the growth rates to the historical average for the period of 2008-2018 for international shipping emissions, extrapolating from the 2018 base year emissions. We take a historical average as there is significant variation in year over year levels.

This exercise supplied us with five temperature pathways, leading to global temperature increases ranging from 1.5˚C to over 4˚C compared to pre-industrial levels. We have assigned a rating to each of these temperature categories: 1.5˚C and 2˚C compatible correspond to those temperature levels, while the Insufficient, Highly Insufficient, and Critically Insufficient ratings correspond to between 2˚C-3˚C; 3˚C-4˚C; and >4˚C, respectively.

The 1.5˚C pathway reflects the maximum level emissions from international shipping that can be emitted for the sector to be rated as ‘1.5°C compatible’. Given the uncertainties in these levels, striving for the lowest level of emissions (and the most stringent reductions) possible is prudent.

Relation to CAT country assessments
We have developed a bespoke method to rate international aviation and shipping as it was not possible to apply the approach used by the CAT for country assessments for these international sectors. That said, this approach is most like the method the CAT uses to determine the level of reductions needed within a country’s borders (which we refer to as ‘modelled domestic pathways’). Adopting a fairness approach was not possible due to methodological challenges. To do so would have required the attribution of GHG emissions from these sectors to countries, and there is no consensus on how best this should be done. The CAT overcomes this limitation by using a range for a country assessment, but that would have been too complicated to replicate for international bunkers.