A huge part of the world fleet will have to be replaced with zero-emission vessels in little more than two decades if regulators set a goal of decarbonising shipping by 2050.

The industry will have to start the transition to zero-emission ships by around 2030 at the latest to have any hope of decarbonising in time, according to government submissions to the International Maritime Organization.

The decarbonisation debate has focused on whether owners can be incentivised to build zero-emission ships through regulation or emissions trading schemes.