IN a perfect world, decarbonisation would go something like this:

This April, the International Maritime Organization passes a simple climate levy paired with a green fuel standard, to help narrow the cost gap between fossil and green fuels.

It doesn’t even have to be high, as long as you have a GFS so ships know what to burn instead.

No one will tell you with what price they’d be happy. But let’s just say about $100 per tonne of CO2e in 2028, rising steadily to, say, $250 per tonne CO2e in 2050.

This raises a mountain of cash for an IMO GHG Fund. Some goes to green R&D, building shore power in ports and training seafarers to use ammonia. Part of it goes to developing countries to pay for their higher fuel and trade costs.

We’ll need green e-fuels. Here’s how to make them:

First, build a massive solar/wind farm. Hook it up to an electrolyser, which cracks water into hydrogen and oxygen. Take the hydrogen and add nitrogen (to make green ammonia) or carbon (to make methanol or methane). Fill up your ship and rejoice.

This would cost an awful lot. Meeting the IMO’s emissions targets would require shipping to replace the equivalent of 200m-300m tonnes of oil with zero- or near-zero carbon fuels by the 2040s. We’d need something like $1.6 trillion invested on land, with about $400bn needed by 2030 alone.

Luckily, the carbon price makes it happen. South Korea has estimated that a GHG levy at $18.75 per tonne CO2e would bring in $11.9bn in 2030, while at $150 it would rake in a whopping $95.3bn — the largest single environmental fund ever proposed.

Take that money and build massive wind and solar farms in the developing world, making green energy for export and lessening the power of Opec and its ilk. Old, dirty ships are scrapped en masse, helping rebalance markets and improve safety.

Ships are retrofitted to green ammonia in drydock, and over time the plunging cost of solar power brings down prices and lessens the need for taxes and subsidies. Shipping joins hands and sails towards a bright green future.

Unless, of course, we get the policy wrong. If instead of a levy, shipping gets another ETS in the form of a fuel standard with credit trading.

UCL, Maersk and Vitol have warned relying on such a tool instead of a levy would fail to raise enough money to decarbonise shipping, lock the industry into fossil fuels by giving LNG an unfair leg-up, and scramble the market signal that e-fuel investors need.

The IMO could produce a messy, vague compromise which gets nothing done, as it has done so many times before.

Or worse still: The talks collapse into acrimony, the negotiators go home, and instead draw up national or regional taxes — one from the EU, one from China, one from the US and so on.

Green rules are levied or axed with each new government, depending on local politics. Shipping splits into an old, dirty fleet and a new, green fleet. Rampant biofuel fraud and fake “green” fuels proliferate.

Natural disaster risk to ships and ports increases insurance costs; more boxes fall overboard.

The worst-case scenario isn’t usually what happens. But it’s worth thinking about when you next glaze over at another IMO headline or net zero policy document.

Countries will see how much money can be made by fleecing shipping, so the green taxes will come, with all their higher costs and other hassles. The only question is whether they do any good.

That’s why such boring debates matter. Good policy is the difference between salvation and disaster.