Because otherwise it's just "we need to do something about that" handwaving and it gets nowhere. So, single out cruise ships - a straightforward way to reduce global pollution by a good degree with minimal effects on the individual.

The problem with ships is that once they enter international waters they can do whatever they want.

Which is exactly what they do, burn bunker fuel outside territorial waters and switch to cleaner fuel when they approach a country (because they are forced to).

There is simply no enforcement outside territorial waters, and if anyone tried to, they'd be immediately condemned by everyone else.

Why don't we ban container ships?

Is it possible that you are a member of a group of individuals that do not enjoy nor participate in cruises and therefore do not give anything up by calling for their ban? You can feel good about it without personally sacrificing anything and instead forcing others to make that sacrifice.

How would you feel if it were the inverse and others were calling for a ban on an activity you enjoy?

I might enjoy eating babies, that doesn’t make someone claiming this practice should be banned on ethical grounds wrong.

In many countries people eat young lamb or veal, some consider it acceptable and others don't.

It is very easy to call for a ban on something that you personally do not enjoy because you lose nothing. In fact a majority of the world's population likely does not enjoy cruising, just as a different majority does not enjoy snow sports, water sports, car racing, motorcycles, horse racing, skydiving, rugby, rock climbing, etc..

There is some form of ethical or safety concerns for each of those but the world would be a very boring place if we banned them all.

It's more efficient to remove the cause of emissions than to tax it and try to compensate for it. All carbon emissions should be taxed, but some things should just not be allowed.

Tax the purchase of bunker fuel for its emissions content. Cruise ships aren't going to drill for oil in international waters.

Is burning bunker fuel at sea really a big problem? My understanding is that the impurities (sulphur mostly) in bunker fuel are bad for people to breathe and create smog, so they shouldn't be burned around population centres. The main greenhouse gas is carbon dioxide, and you produce roughly the same amount of that per watt of power no matter what hydrocarbon you burn.

Hydrocarbons are molecules that are various combinations of H and C atoms. The H burns to H2O, the C to CO2. A hydrocarbon with a greater quantity of H is going to emit less CO2 when burned.

Sure, but H weighs 1/12 as much as C. Most of the fuel mass goes to CO2 no matter what you do: whether you slap on 1.5 H atoms or 3 for each C, it makes up a small part of the molecular weight.

Of course, it could be that the C-H bonds contribute much more to the energy released by burning the fuel than the C-C. But this doesn't seem to be case. Here's a paper in favour of switching to lighter fuels for ships: it argues that the total supply chain CO2 contribution would be higher (it takes energy to refine those fuels), but only by 1%.

I think that "bunker fuel is really bad and ships switching to lighter cleaner fuels is important for the environment" is a seductively easy but bad target for carbon reduction. There are way better places to spend our efforts.

[0] https://www.tandfonline.com/doi/pdf/10.3155/1047-3289.58.4.5...

> There are way better places to spend our efforts.

The easiest, most economically efficient, most productive way to do it is to tax the C content of fuels. Use the monies raised to subsidize green energy.

Banning is an indiscriminate club that does a lot of collateral damage.

But that's exactly what wouldn't be suitable for reducing pollution from bunker fuel. Shippers would pay the same taxes as for burning kerosene or diesel, plus or minus a few percent, but they'd go with the cheaper option and cause huge sulphur pollution in port cities.

The regulations we have now (no high-sulphur fuels in cities, no leaded gasoline...) are better than taxing only CO2 emissions, even if they're not perfect.

So do the obvious - tax the sulfur content of the fuels, too.

The problem with banning is its inflexibility. For example, let's say you have a bunker-fueled emergency generator for a hospital that you use only when the power goes out. The pollution it emits is negligible. But by banning bunker fuel, you'll have to replace the emergency generator, at considerable expense and environmental cost.

With taxes instead, you:

1. bunker fuel will only be used when there's high value for it, and you won't have to add a plethora of exemptions into the regulation

2. have a revenue center for the government instead of a cost center - revenue that can be used to subsidize green initiatives