>>1350707There's a distinct lack of numbers in this thread so I tried to estimate your question.
The Queen Mary 2 burns 261 tons of heavy fuel oil and 237 tons of marine gas oil daily while underway. It has a capacity of 2620 passengers on a 7-day, 5503km trip from Southampton to New York. Running all those conversions through my possibly dodgy math, the QM2 achieves 5.25 passenger-kilometers per liter of fuel burned. Meanwhile, according to the International Council on Clean Transportation, the cleanest Transatlantic airline in 2014 was Norwegian, flying at 40 passenger-kilometers per liter. The dirtiest airlines were only 50% worse, so still considerably more efficient than the QM2.
So unless I really fucked something up, it does seem like the most climate-friendly way to practically cross the Atlantic is via budget airline on a fuel-efficient twinjet, unless you own a sailboat fitted for transoceanic voyages and are sufficiently skilled.
Sources:
https://www.beyondships2.com/faq-cruise-ship-fuel-mileage.htmlhttps://media.uk.norwegian.com/pressreleases/norwegian-named-most-fuel-efficient-airline-on-transatlantic-routes-1262733https://prodepc.blob.core.windows.net/epcblobstorage/GPCDOC_X_cbe_26724_key_140007515295_201302281447.pdfUnit conversions from Google and WoframAlpha.
