Q 2: It is just a tax, isn’t it?

The employed mechanism is a hybrid quantity-price instrument, not just a tax, pure price instrument. The level of the levy is not set arbitrarily as in a tax but it is determined by the quantity goal (cap on emissions) and the prevailing market carbon price. The carbon price, created by the EU ETS and other mechanisms, in fact enables this hybrid mechanism. Without it the scheme could not exist. Secondly, the revenue raised is directed to reduce emissions as per the cap.

Furthermore, the scheme provides an option to go some way in correcting the market failure relating to the lack of adequate investments in shipping R&D for the significant emission reductions required. Additional revenue for technology research and transfer can be raised, but only if the levy is set higher than the level dictated by the emission cap and carbon price.
Some emission reductions would inevitably occur within the shipping sector driven by underlying economics. Only the remainder of reductions needed would be purchased from other sectors. How much is purchased from other sectors is driven by what is most cost efficient.