Couldn't we make the same argument for an airliner:

X cubic meters of CO2 divided by 200 odd passagers in an airliner.

Vs.

Y cubic meters of NOx/SO2/CO2 divided by that person and however purchased the freight goods in the container.

We could argue that the cargo ship would sail irrespective of that passenger, but we could equally make the same reasoning for people buying last minute seats that would otherwise fly empty.

Without doing the maths this risks making very fortunate people feel good about themselves and distracts from corporation practices that are orders of magnitude more harmful.

Again I do not have the numbers but what is the carbon impact of halting all german flights versus decomissioning all german coal plants?

> We could argue that the cargo ship would sail irrespective of that passenger, but we could equally make the same reasoning for people buying last minute seats that would otherwise fly empty.

Sure but the cargo ship business isn't moving passenger. If they always fill all the passengers rooms, they won't decide to bring more ships into the equation. Whether there's 0 passenger or 15, the ship will still go through that same amount of fuel.

Someone else did gave some good example of energy usage that a passenger will cause, like the water he will consume will need to be desalinated, or if he get sick and that require diverting a ship.