I See No Ship's (Emissions)?

Being an 'offshore activity', marine shipping firms have, thus far, entirely avoided having to deal with their climate-changing emissions of carbon dioxide (https://www.theguardian.com/environment/2021/oct/05/shipping-cut-emissions-low-carbon-tech-climate). The International Marine Organisation (IMO) is currently committed to a 50% reduction in emissions by 2050. This would be wholly insufficient to prevent further climate change. The International Chamber of Shipping (ICS) is an organisation to which many owners of shipping fleets belong. It claims they are prepared to go further than the IMO but only if governments provide support for the development of low carbon technologies. One such technology might involve fuelling ships with ammonia, so they could burn hydrogen to power their engines. The ICS suggest that a $2 per tonne levy on current shipping fuel, could be used to pay for the development of low carbon technologies. If the levy is agreed, they say, shipping will vow to reduce emissions by 25% by 2030 and achieve zero emissions by 2050. Green campaigners are unconvinced. They maintain that the levy would generate insufficient cash to develop the needed technologies. One might also ask, why it is not the responsibilty of the fleet owners to upgrade their own ships without government support? The environmentalists also point out that carbon dioxide is not the only problematic emission from marine shipping. Shipping fuel also produces substantial amounts of black carbon (soot) emissions. These also have a powerful effect on global heating.