Carbon output numbers for flying vs. cruising are not polemics.
Maybe, maybe not. You don’t know how those numbers were calculated and unless you do, you don’t know whether they have been calculated fairly or not. There are any number of ways I can think of that the figures may be biased as all hell. One just doesn’t know. And when those figures are usually given in the context of an otherwise transparently polemical piece, my confidence in their accuracy isn’t high.
CO2 is fungible, so come up with a cost per ton. The Obama administration came up with a social cost of $50/ton, though IMO that’s probably an underestimate. Charging everyone the same price means it’s hard to game the system. The emitted CO2 is exactly proportional to the burned fuel and therefore easy to calculate.
Alternatively, set a fixed total emissions limit and let the market set the price. Again, it’s fungible and hard to game.
By my math, the Oasis of the Seas is emitting in the ballpark of 3 tons of CO2 per passenger-week. Smaller ships are likely less efficient. Regardless, charge them by the ton and spend the money on carbon-free energy subsidies. Do the same for all other carbon emitters as well.
Your final sentence is very important. Because IME what many who consider the footprint of cruise vessels fail to do is consider the footprints of what the thousands of passengers would have done if they didn’t go on the cruise.
Or have fun, or want to do it ever again, which kind of goes against cruise lines’ business model.
The OP is considering ships as transportation, not as a floating resort. Just like with airlines, nobody wants to ride on the plane or the ship as such; they just want to be wherever it’s going. If Star Trek transporters existed, they’d use those instead.
Obviously the discomforts one can tolerate for 2 or 12 hours are very different from 2 or 10 days. So the ship will have to have more creature comforts, food, etc. Ships are inherently vastly more efficient. Which effect predominates? Seems pretty clear to me that ships are by far the more efficient choice, if fuel / CO2 is the only factor being considered. But humans value their time.
I was figuring on some combination of mostly carbon tax pricing (as Dr.Strangelove mentioned) and a little flygskam accomplishing that IF there’s a “spot” where an ocean liner can be fast enough and comfortable enough to have just significantly less enough carbon emissions than flying that companies would bother to offer the service and travelers would bother to take it.
But with cruise ships (more emissions than flying) on one hand and container ships (efficient because speed is minimized and occupancy maximized) on the other, I didn’t know if that “spot” even exists. Hence my OP.
I was trying mostly to pull the thread back to what I thought was the point of the OP, while everybody else seemed to be focused on cruising = waterborne resorts. I wasn’t really offering my own opinion; just my own outline of the problem.
My own view is that the total demand for people-transport is very price-sensitive and very time-sensitive.
From the pre-COVID baseline of, say, trans-Atlantic traffic, a doubling of price would more than halve the demand. And changing from the current half-day service to 3- or 4-day service would cut demand to 10% of what it was. At best.
So IMO there’s a very narrow window where society could raise carbon pricing enough to all-but cancel air travel and still have any meaningful remaining demand for long distance travel by any means.
Assuming we have real carbon pricing with the full externalities priced in:
The embedded transportation costs of goods would be vastly larger, so goods from raw material to finished product would be sourced much closer to point of use, or done without altogether. The rank and file citizenry would stay-cation; longer-distance leisure travel would drop to near zero, and with it the entire tourism economy. The wealthy and big business leadership would move about with impunity as they do now since they’re simply not price sensitive in the slightest.
At least all the above would be true if carbon pricing went up faster than adaptations could be made. The trick is to make the taxes or whatever sting enough to spur action without hurting so much as to kill the demand that funds the profits that fund the research to make the adaptations. And, as with luring the donkey with a carrot on a fishing pole, as industry catches up to making the taxes hurt less, they need to be steadily increased to keep the pain = pressure on for more adaptation until we get to true zero, not the “convenient zero” that comes when you carefully ignore the contributions of this, that, and the other well-connected exceptions.
Ships do provide a viable transportation, but only for shorter journeys. We tend to call them ferries.
Cruise ships are an anomaly, mostly the passengers have no care where the ship goes, and if it sailed around in a circle they would probably be quite happy. Passengers pay to stay on the ship, and desire longer, not shorter stays aboard. Liners on the other hand involved destinations, and a desire to get somewhere fast. People pay more to stay less time aboard. Jet travel is hard to beat here. Prices are ridiculously low, and fast enough that the discomfort is bearable.
The problem most people have is time. A three week vacation is not going to be much of a holiday if two of the three weeks are spent in a box. People put up with a couple of days total in a long white tube. But it gets a bit wearing after that. (Those of us that live in Oz are resigned to lots of time in long white tubes to get most places.)
But ferrys work well in some parts of the world. When the journey (or a part) can be done in a day, and you can hotel hop along a coast, taking time to enjoy things, sea travel works for the leisure traveller. Many ferries will carry cars, so there is flexibility not otherwise available. Many ferries have no need of cabin accommodation, and can pack passengers in.
I can’t see many Australians ferry hopping their way to Europe, even if a service was established. But back in the glory days of flying boats, it wasn’t vastly different. One did need to be seriously rich, in both time and money.
My parents emigrated to Oz from the UK by ship. In principle I have made the journey from Oz to the UK and back by ship as well, but I was 2, so I have no recollection. But it wasn’t that long ago that it was the accepted thing.
One notes that in the world cargo ships that LNG is being seriously considered for new ships, with at least a few already launched. The sulphur emission restrictions have made things harder, and advances in getting diesels to run on LNG have pushed things along. Ubiquity of LNG facilities around the world as a result of mass transport of LNG as a commodity make logistics viable. Not quite a zero carbon fuel, but steps on the way. Hydrogen looks a lot closer when you consider how far along LNG has got.
There are some fairly long ferry routes around. For example there’s one between Alaska and Washington state that takes 38 hours. And that’s no where close to the longest, although some googling did not find a definitive answer as to which is the longest. And some of those long ones are more like cruise ships than ferries.
Also note that a number of short route ferries have been converted to electric ships and more will be converted in the near future. But these are almost all very short routes, most, if not all, less than 25 km between ports.
Focusing on the fuel that a vehicle uses is too narrow. Fuel is a part of an energy storage system. It’s the energy source (and total amount used) that determines the environmental impact of a vehicle. If the source is fossil carbon or other non-renewable resource, then it’s a bad impact. If the source is a renewable resource, then it’s not necessarily bad.
Taxing carbon emissions does not scale well. There are many emitters. Instead, it’s better to tax the fossil carbon sources–tax it as it comes out of the ground. Fossil carbon extraction is much more centralized than the emitters. And, if you like, rebate it as carbon gets permanently sequestered. Let the market distribute the costs.
Give a couple of examples of what those passengers could have done if they didn’t go on that cruise and that:
a) Is anywhere near comparable
and
b) isn’t also considered an environmentally unfriendly choice
Yes, there are lots of issues with calculating carbon footprints, but the impact of those issues depend a lot on the nature of the activity or product being examined. It’s not enough to say “These are just polemics! There are issues!”, you actually have to show that any issues have the potential to be relevant to the comparison.
FWIW, large ship powerplants are more akin to those used in fixed electrical generation plants - for example, the LM2500 turbines that the Navy uses in multiple makes of ships are also adapted for use as natural gas powered electrical generation turbines on land. (and interestingly enough, are all derived from aircraft gas turbines)
The catch is totally the scale that large ships are at, not the inability of technology to provide a low/lower emission solution. I mean, there’s no real technical reason that someone couldn’t have a LNG powered electric motor driven ocean liner, but the catch is that it’s effectively a floating electrical generation plant like you’d use to power a good sized city or town.
Actually, cruise ships do relocation voyages across the Atlantic every year. It would be interesting to see what kind of economy they get doing that, and how it is affected by transit time.
If the kite can be skewed 50 degrees to the wind, that’s what the ship can do. It runs parallel to the kite. You may notice that when a yacht is sailing upwind the sail is operated close-hauled. Effectively it’s not exactly parallel to the direction of motion, and neither is the kite – but a ship isn’t far off the capabilities of a yacht – if you think 10 or 15 degrees isn’t much 
A ship with a kite and a keel can sail against the wind, just like a ship with any other kind of sail. That “50 degrees” is not “130 degrees”.
Yep. No CO2.
Or windjammers, they have windjammers cruises they are very popular.
https://www.libertyfleet.com/windjammer-cruises/#:~:text=A%20windjammer%20sailing%20cruise%20is,and%20peacefulness%20on%20the%20water.
2023, 2024, 2025 Caribbean Cruises | Caribbean Vacations | Windstar Cruises
Windjammer cruises are very popular.
A very luxurious clipper ship could cross the Atlantic in about two weeks, during nice weather.
Sailing from CA to Hawaii could easily be done, mostly year around.
That’s not super-obvious to me. If the kite is symmetrical, the string is going to be exactly parallel with the wind. You could design a kite to be controllable, I suppose, though it seems like it wouldn’t have much control authority compared to a sail (or better yet, and airfoil).
That said, you could design it to go straight upwind. Hook a generator up to the winch that deploys the kite line. If designed efficiently, it’ll generate more power as it unreels than it takes to drive the ship forward. When you run out of line, furl the kite, reel it in, and repeat. You could use the same method to kite downwind faster than the wind.
Our last (and only) cruise was on the Wind Surf:
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That’s a 342 passenger luxury cruise ship capable of crossing oceans under sail or power. It’s an absolutely amazing ship, and a real luxury experience. While we were on it, I think something like 70% of all travel was under sail alone. The sails are fully automated and require no crew to furl and unfurl the sails.
IMO, small ships like this are the future of cruising. The large cattle car ships have always been hotbeds of disease spread. These ships, with a high crew to passenger ratio and lots of open space per passenger, are much better. And they aren’t much more expensive. We did a 7 day Caribbean cruise for $1799 ea, all inclusive except for premium alcohol. And the food is all five-star gourmet fare. You can get those cruises for $1599 now, I see. That tells you the sailing aspect isn’t all that more expensive.
Sounds great!