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Comment by johngalt | Hacker News Reader

Air travel is already quite efficient. If we break it down per passenger, the gas mileage is around 50mpg. Cutting total flight distance only cuts the amount of time that the aircraft is in it's most efficient travel regime (high level cruise). With no corresponding change to the amount of fuel used to climb up to cruising altitude.

Adding extra days to every trip is not cost free. Mode switching for travel is also not cost free. Creating gigantic airports at the nearest points between continents etc... Large scale, expensive and difficult to coordinate changes; which are trying to squeeze more efficiency out of an already optimized system.

Don't mean to sound overly critical, these are interesting ideas on systemic change.

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> Adding extra days to every trip is not cost free.

Ah, it's a bit (read: very) terrible that the system we now live in focuses so much on work and "productivity" that for the most of us, we only get just a few days a year to enjoy our lives. Even less for Americans. And even less for the people working in slave-ish conditions.

Unless you're a billionaire, I guess, then life's a bit easier. Says me, who, with my middle class income, is part of the 1% in the global scale...

I’m not sure if it’s what the author intended, but I understood that to be talking about the actual trip being more expensive. I’ve looked into sea travel before for short (e.g. Melbourne to Tasmania) and longer (e.g. Melbourne to New Zealand), and it consistently ends up a good deal more expensive than air travel because it’s basically a hotel and restaurant for overnight or however many days or weeks or whatever, whereas with air travel that part is minimised, and accommodation and food at both ends can be much cheaper (e.g. free accommodation between one’s own home and friends’ homes).

Too bad we used productivity gains to consume more rather than give us more leisure time. I think if I had Tim Bray flexibility, I’d be willing to do take nothing but bicycle touring vacations.

> With no corresponding change to the amount of fuel used to climb up to cruising altitude

Yes, but

1) a plane flying a larger distance has to lift a heavier load of fuel

2) emissions tend to do more damage at high altitude than they do at ground level

so I would not discount the benefits of reducing flight distance as much as possible.

Source: How Bad Are Bananas? by Mike Berners Lee

>emissions tend to do more damage at high altitude than they do at ground level

I've always been a bit dismissive of aviation as a carbon emissions contributor because globally it only accounts for around 2%. Thanks for pointing this out, I was unaware of this fact. Is the relationship between altitude and warming effect known? Are we talking linear or something worse?

2% is plenty anyway. I mean, we have to start somewhere.

I think we're still puzzling it out, as there's both radiative forcing and contrails (the vapor, or condensation trails planes emit).

If you check out these two emission factors from the UK government, one taking radiative forcing and contrails into effect and one not:

https://www.climatiq.io/explorer/emission-factor/domestic-fl...

You'll see a noticeable difference, (almost a doubling)

Full disclaimer: Work at Climatiq, but the emission factors are not from us directly.

Appreciate the detailed answer - I was unaware that contrails were significant. TIL!

You're welcome!

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