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