The United Nations International Maritime Organization’s (IMO) revised greenhouse gas reduction strategy puts shipping on course to exceed its current share of the world’s 1.5 °C carbon budget by 2032. As the IMO works to develop its enforcement mechanisms, nations and regions face an imperative to develop mandatory policies to align the industry with a 1.5 °C pathway.

This paper assesses the scalability of port-to-port green shipping corridors and suggests a collaborative model to build on corridor development. In addition to corridors, nations, sub-nationals and their ports can align with regional partners to create international blocs of high ambition ports. By leveraging economic buying power and public-private investments and aggregating demand for renewable electricity and zero-emission (ZE) fuels, regional alliances can develop infrastructure at scale, create clusters for innovation and promote rapid deployment of ZE ships. We examine arguments ports cite as concerns about decarbonisation policies, including cargo diversion, increased costs and reduced profits. By looking to existing examples of regional policy and multi-port collaboration, we challenge the assertion that first movers will suffer loss of business. Regional alliances can generate a rising tide – ensuring that ports of all sizes, economic niches and vessel specialisation can reduce emissions on a trajectory commensurate with our climate emergency.