The huge amount of time saved with plane vs boat makes the former the superior option. There's no way a ton of CO2 is worth the comparative QALY loss you get fr

The huge amount of time saved with plane vs boat makes the former the superior option. There's no way a ton of CO2 is worth the comparative QALY loss you get from five days in a boat compared to the other things you could be doing with that time (if you're on a properly efficient liner rather than a super inefficient modern luxury cruise liner). Even the extreme upper end of CO2 externalities don't go above $1000/ton with most reasonable estimates below $100/ton.