As the International Maritime Organization made strides in setting tough decarbonisation targets for shipping this month, environmental groups were disappointed by a lack of progress on their calls for a ban on exhaust gas scrubbers.

The Clean Arctic Alliance said that the groups’ claims — asserting that IMO rules allowing uses of the devices an exception to the IMO ban on fuel sulphur content are in conflict with the UN Law of the Sea — have been referred to the UN shipping regulator’s legal division.