In the fight to cut ship emissions, the International ­Maritime Organization’s ­mandatory Carbon Intensity Indicator (CII) is likely to have unforeseen effects, particularly on cruiseships.

Under the CII, ships are given a rating of A to E based on their annual carbon dioxide emissions and distance travelled. Ratings of A to C are acceptable, but if a ship receives D or E, a corrective plan needs to be developed and approved to get it up to at least a C.