Elheru Aran wrote: 2019-10-14 10:57am
I don't have the time to look it up for myself, so out of curiosity: what's the carbon footprint of taking a ship across the ocean, versus a plane? (assuming standard diesel or bunker-fueled liner)
That's complicated - there's a difference between a lavish cruise ship and something that's bare-bones transport. But, after a brief google, it looks like
roughly a 3:1 ration of flying costs vs. boat costs traveling long distance. Keep in mind, though, a typical cruise ship might well have a LARGER negative impact than an airline flight between energy generation costs for all the amenities and the dumping of sewage and garbage at sea. Some cargo ships also come off worse than airplanes due to continuing to burn high-sulfur fuel.
Potentially boats are better but
in practice the opposite may be true.
That's one reason I'm leery of suggestions to simply ban air travel - it may not have the desired effect. If no airplanes means more big boats generating more pollution than the airplanes did we have gained nothing at all.
Ferries tend to be pretty good in comparison to flights - if you have an option to cross water via ferry or via airplane then ferry is
probably the more environmentally responsible option. Cruise ship from, say, Florida to a resort in, say, the Yucatan? Contrary to initial assumptions, a direct airplane flight might actually have a smaller carbon footprint than taking the ride in a fancy cruise ship. Of course, you can also ask whether that trip is "needed", or perhaps better said, "justifiable" in the first place.
Maybe people would have to save up "carbon coupons" - you get points (or whatever) for reducing driving, meat-eating, making your home more energy efficient, buying stuff second instead of first hand and after a decade or so they can trade them in for a plane trip or cruise from Florida to the Yucatan as a reward for reducing their carbon footprint. You could probably do it in such a manner that even after turning in the "carbon coupons" they still don't emit as much carbon as they would have without making changes.
While some folks (particularly those reading this thread) will make lifestyle changes out of a sense of responsibility or morality a lot of other people won't. So set up a system where normal human selfishness (I want X) results in them making choices that wind up benefiting the planet. You don't get very far telling people to spend money on weather-proofing their homes because some city on the other side of the planet is threatened by rising sea levels. You will get more buy in if you tell folks "hey, for an initial investment of X you will save Y on your fuel bills the first winter and continue to save going forward, which in Z amount of time will match X, after which you'll still continue to save money".
Anyhow, boats these days generally take 6-8 days to cross the Atlantic - call it a week on average. (The Pacific, of course, will take longer due to greater size.) Some ships have done it quicker - I believe the sailing record is less than four days at this point - but those are usually purpose-built ships with little carrying capacity, basically boats designed to race and not to carry cargo or passengers.
If we went back to sail (probably with an engine back-up) that would definitely be environmentally friendly method, but it requires more crew and more skills and it wouldn't be any faster and let's face it, time is a factor in travel. It's certainly possible, though, as centuries of sail-powered cargo proved before the steam engine became a viable means of propulsion.
There is also the problem of piracy, which is still a problem on the high seas. It's a
lot harder to stop an airplane over the ocean and board it than to stop a ship on the ocean and board it.
For that matter, airships might also be more environmentally friendly - they, too, tended to take 4-7 days, slightly faster than ships BUT far, far more vulnerable to weather problems. Fixed wing aircraft eliminated trans-oceanic airship travel (actually, pretty much all airship travel) by being faster AND safer, even with early 20th Century technology. An additional wrinkle is the lifting gas requirement - helium is a very limited resource. Hydrogen is actually superior from the standpoint of lifting mass off the ground, but it's flammable and the Hindenburg disaster soured the public on it long-term. IF we could get the public to accept hydrogen as a lift gas then airships could be propelled by much less energy-intensive means, possibly even solar, but certainly since airships don't burn fuel to stay aloft, but just to push themselves through the air, they burn less fuel for the same mass transported the same distance.