As a side-note, please be careful to distinguish between local pollution from dirty fuel (SOx emissions, particulates), and global pollution from _carbon emissi

As a side-note, please be careful to distinguish between local pollution from dirty fuel (SOx emissions, particulates), and global pollution from _carbon emissions_. They are two wildly different things, and often there is a big trade-off where cutting one raises the other (c.f. the VW scandal). Cruise ships, as it happens, are horrible on both measures.