IMO published its Fourth Green House Gas Study which shows a 9.6% increase in shipping emissions, mostly due to the continuous increase of global maritime trade. The study estimates that shipping emitted 1,056 million tons of CO2 in 2018, compared to 977 tonnes in 2012. This amount accounts for about 2.89% of the total global CO2 emissions in that year.

The study also includes data on the carbon intensity of maritime transport as well. The shipping sector's carbon intensity as a whole, and for most ship types has fallen between 2012 and 2018. This carbon intensity, as an average for all types of shipping was between 21% and 29% lower than in 2008, when the CO2 emissions reached 794 million tonnes.

The document also demonstrates that the IMO's 2050 green house gas reduction ambitions cannot be reached only through energy-saving technologies and speed reduction of ships. Therefore, the adoption of greener technologies and alternative fuels will be essential to fulfill these objectives.

An executive summary of the study can be found at: 

https://wwwcdn.imo.org/localresources/en/OurWork/Environment/Documents/Fourth%20IMO%20GHG%20Study%202020%20Executive-Summary.pdf