Maritime shipping is vital to the global economy, facilitating 80% of trade and enabling trillions of dollars in annual economic activity. It is also responsible for more than 700 million tonnes (Mt) of carbon dioxide (CO₂) a year—a larger carbon footprint, if taken alone, than all but about six of the world’s countries. And with its emissions forecast to continue growing under business-as-usual, the maritime sector’s misalignment with the energy transition is coming into ever-starker relief.