This study assesses the impact of international sulphur emission reduction regulations on global shipping. Ships emit a large amount of sulphur oxides that have significant health impacts. To mitigate these, international regulations cap the sulphur content of ship fuel. In certain parts of the world, emission control areas (ECAs) with even stricter standards have been established. In the emission control areas, new requirements introduced in 2015 limit the sulphur content of ship fuel to 0.10%. A new, lower global sulphur cap of 0.50% is planned for 2020. This report examines the 2015 cap effects on shipping and the potential effects of the new requirements foreseen for 2020. It assesses the cost increase for maritime transport associated with the sulphur caps, impacts on shipping operations as well as on other transport modes, and on the environment. The report also highlights policy gaps and challenges for the enforcement of sulphur emissions regulation for shipping.