Analysing recent trends and drivers of maritime transport CO₂ emissions: Insights from a decomposition analysis for the OECD and the world

International shipping is a cornerstone of global trade, but comes with a significant carbon footprint, at 2.5% of total energy-related CO₂ emissions in 2024. The decarbonisation of maritime transport has thus become a central focus in climate policy discussions. This paper uses the OECD’s experimental maritime transport emissions database to assess recent trends and drivers of CO₂ emissions, contrasting dynamics for the OECD and the world. Global emissions rose by 9.3% between 2019 and 2024, with container ships and bulk carriers contributing the most. A decomposition analysis is then applied to disentangle the relative contributions of six key effects: transport intensity, economic activity, capacity underutilisation, distance, emission factors, and fuel intensity. It shows that the increase in emissions was driven primarily by GDP growth, reinforced by rising transport intensity, with improvements in fuel intensity and a negative distance effect only partially offsetting these effects. Capacity underutilization had a positive effect at global level, and mildly negative for the OECD. The emission factor effect played only a minor role. Analysis of decomposition results for top-emitting ship types shows significant dynamics which can be explained by exogenous shocks (Covid pandemic, disruptions to transport routes, wars) combined with structural and longer-term changes in fleet dynamics and environmental regulation.