JRC analysis quantifying greenhouse gas and air pollutant emissions from ships transiting EU ports in 2019, drawing on the MRV-THETIS database, alongside a meta-analysis of life cycle assessments for maritime fuel alternatives. The emissions picture is clear: shipping is a significant and growing source of CO₂, SO₂, NOₓ, and particulate matter, and energy efficiency improvements alone are insufficient to bend the trajectory without fuel switching. The LCA meta-analysis documents the extent to which the decarbonisation potential of alternative fuels depends on the upstream energy chain — green ammonia and green hydrogen perform well only when the electricity used to produce them is genuinely low-carbon, a condition that constrains deployment timelines considerably.