In terms of global warming potential, they are nowhere close to that. The "50 million cars" statistic is specific to the SOx output of the ships (sulfur oxides)

In terms of global warming potential, they are nowhere close to that. The "50 million cars" statistic is specific to the SOx output of the ships (sulfur oxides). These cause local impacts (breathing issues, view haze, damage to plants etc) and wide impacts (acid rain) [1]. Because of the strong local impacts, fuel grades for cars, trucks, etc had strong reductions to sulfur content, but ships did not (though often they are required to use more expensive, more refined fuel in port or 20km of shore or what have you). All this to say, these ships do create super high emissions of Sulfur Oxides, but their CO2/equivalents emissions are quite low (the lowest per kg*km of any means of transport! [2] ). Worth addressing, but not nearly the equivalent of 50 million cars in the "emissions" that the common dialogue refers to. [1] https://www.epa.gov/so2-pollution/sulfur-dioxide-basics https://www.epa.gov/so2-pollution/sulfur-dioxide-basics [2] https://www.theguardian.com/sustainable-business/2014/aug/01/sustainable-shipping-is-making-waves https://www.theguardian.com/sustainable-business/2014/aug/01...