The International Maritime Organization aims to achieve full decarbonization by 2050 in response to climate change. This ambitious goal demands well-defined strategies guided by techno-economic assessments. The complexity of global shipping systems makes predicting long-term maritime trade patterns challenging, necessitating scenario-building rather than precise forecasts. Investigating shipping demand scenarios is crucial due to the uncertainty brought by the energy transition and its role as the primary driver of shipping emissions. This paper improves the representation of maritime shipping in Integrated Assessment Models (IAMs) by examining the impacts of climate targets on future shipping demand. A novel econometric model, grounded in advanced gravity theory and integrated with machine-learning algorithms, is proposed to estimate the elasticities of variables in bilateral seaborne trade. By coupling this model with the WITCH IAM, we explore various scenarios, providing deeper insights into trade patterns and their implications. The results show that stricter climate policies and higher carbon taxes reduce GDP due to higher abatement costs, higher fuel prices, and therefore reduced seaborne trade, especially for oil products and containerized cargo. Early adoption of carbon taxes in Europe may shift oil production and consumption patterns, temporarily boosting seaborne trade. Sub-Saharan Africa could experience significant demand growth due to economic and population increases.

As climate change continues to pose a significant threat to our planet, international maritime shipping plays a crucial role in mitigation efforts. Recognizing the urgency, the International Maritime Organization (IMO) has revised its targets, now aiming for full decarbonization by 2050. However, there is no established pathway to get to the target. To achieve this, there is a need for models depicting possible futures of the maritime sector, and finding feasible pathways. This research aims to find the most suitable way to develop models to find pathways toward decarbonization targets. This involves evaluating existing ranges and scenarios to understand current estimations and their underlying assumptions and assessing the most suitable modeling methods based on defined criteria. Considering the context, the most suitable models for this objective should perform on a global scale. They should include dynamics between shipping demand & supply as well as the derived fuel demand and supply and emissions; integrate the sector with other parts of the economy; incorporate various technologies into the framework; and span multiple scenarios. The study has two main parts. First, existing scenarios on the future of maritime shipping are analyzed to identify current estimations and assumptions impacting these estimations. Second, various modeling frameworks are assessed against the defined criteria to identify the most suitable modeling structure for achieving the decarbonization targets. Many projections do not meet the IMO’s updated targets, highlighting the need for a paradigm shift in setting targets and finding feasible pathways rather than focusing solely on individual measures. Integrated Assessment Models (IAMs) have been identified as suitable for such projections and policy analysis, although international shipping is often underrepresented in current models. Future research should combine the insights of sectoral models in integrated frameworks such as IAMs to develop integrated strategies to investigate pathways to achieve zero-emission targets. The ultimate goal is to understand how to effectively reduce the sector’s emissions and achieve more environmentally friendly international maritime shipping.

The decarbonization of shipping has become an important policy goal. While integrated assessment models (IAMs) are often used to explore climate mitigation strategies, they typically provide little information on international shipping, which accounts for emissions of around 0.7 GtCO₂ yr⁻¹. Here we perform a multi-IAM analysis of international shipping and show the potential for decreasing annual emissions in the next decades, with reductions of up to 86% by 2050. This is primarily achieved through the deployment of low-carbon fuels. Models that represent several potential low-carbon alternatives tend to show a deeper decarbonization of international shipping, with drop-in biofuels, renewable alcohols and green ammonia standing out as the main substitutes for conventional maritime fuels. While our results align with the 2018 emission reduction goal of the International Maritime Organization, their compatibility with the agency’s revised target is still subject to a more definitive interpretation.