International shipping contributes about 3% of total global CO2 emissions, about the same as that of Germany. In 2018 the IMO set out its ambitions for eliminating CO2 emissions. Since then concrete proposals have been thin on the ground. Mandatory slow steaming seems dead in the water, with concerns that it would delay introduction of carbon neutral tonnage. To facilitate this a new proposal has been put to the IMO just before Christmas by various international shipowner associations, such as BIMOC and the International Chamber of Shipping. The proposal is to introduce a mandatory levy of US$2 per tonne on bunker fuel purchases to fund a US$5 billion ten year programme to accelerate the R&D effort required to decarbonise the shipping sector and to catalyse the deployment of commercially viable zero-carbon ships by the early 2030s. The programme could be put in place by 2023 via amendments to the existing IMO Convention for the Prevention of Pollution from Ships (MARPOL).
In the meantime CO2 emissions from international shipping are likely to increase. The 2018 report of the Intergovernmental Panel on Climate Change (IPCC) gives a remaining global carbon budget of 420 gigatons of CO2 for there to be a 67% chance of stabilising the global temperature at 1.5 degrees Celsius over pre industrial levels (p 108 of chapter 2 of SR15). The current rate of CO2 emissions is 40 gigatons per annum. The maths is not hard to do.