Air travel is not a problem because the emissions per kilometer are that bad but because one can easily travel one or two orders of magnitude farther than one usually would.

Exactly. It's not like if you couldn't fly from Los Angeles to New York once a month - you would just drive by yourself - and produce the same amount of carbon.

You wouldn't produce any carbon, because you'd likely never make the trip!

Yes, this is why dealing with air is so tricky in economic terms, because "uninducing demand" does have more intrinsic downsides. Car -> rail is a mere political problem, once you get there it "unlocks" more travel so it is clearly economically good.

I guess thank god for 9/11 boosting security theater. Don't like all the other patriot act garbage, but the degree to which air travel is so awful really helps here.

After 9/11 air travel plateaued for 3–4 years, then afterward rebounded to the original trend line (i.e. massively expanded, and continues to expand).

It doesn’t seem that all of the unpleasant security theater is enough to significantly deter people from flying.

No one its own, but I think it would make a difference had we avoid hsr alternative.

So your preferred solution is to restrict the allowed travel radius of people, a bit like with medieval serfs?

Restrictions may not be needed. Remove subsidies and price in externalties.

Most people dont realise that aircraft industry and fsrming use special fuel and pay no tax on it. While it makes sence that we sibsidiae cost of food, it is less clear why we subsidise airlines

> While it makes sence that we sibsidiae cost of food

That's already a thorny subject given that most governments also subsidize food sources that are vastly inefficient and resource-intensive even in cases where reasonable alternatives exist. Meat/dairy producers are still the primary recipients of subsidies in the US and many other countries, at least in Europe.

This number distinguishes between fruit/vegetables and other products, although the article apparently suggests that the use of corn/soy in meat production makes this figure more relevant:

> According to recent studies, the U.S. government spends up to $38 billion each year to subsidize the meat and dairy industries, with less than one percent of that sum allocated to aiding the production of fruits and vegetables.

https://jia.sipa.columbia.edu/removing-meat-subsidy-our-cogn...

If intentions are the same then these still can be seen restrictions on mobility.

Maybe encourage more high speed rail instead?

What a rhetoric device.

Is your preferred solution to let people die in droves to a mass extinction ?

My preferred solution is buttloads of nuclear, carbon neutral solutions to liquid fuel (e.g. pulling CH4 out of atmosphere with Sabatier) and general carbon capture.

While producing clean energy would be great, a significant share of our travel issues is related to land use.

Ok, but... airplanes use the least land?

Much like the difference in land use with or without cars is not simply roads and parkings, but also the horizontal development of cities rather than vertical, the land use involved by planes is not simply the airstrips. Among others, it is also all the land developed specifically for vacation in remote places. If you look at [1] for instance, this area would simply not be developed if planes were not a thing.

[1]: https://www.google.com/maps/@21.1715988,-86.8077681,1041m/da...

What is wrong with vacations in remote places?

What mass extinction? From climate change? Has the Intergovernmental Panel on Climate Change said that because I’ve never seen that as a scientific claim.

We are currently going through a well-documented extinction[1]. It's not recent in human terms, but it's been accelerating recently, with industrialization.

Climate change is not the only, nor the major cause in the current extinction, but it contributes. In a way, this is unfortunate: it would be easier to have only one problem.

The relevant body for scientific information is not the IPCC, but the IPBES [2]. Like the IPCC, it releases reports summarizing the situation and its causes [3].

[1]: https://en.wikipedia.org/wiki/Holocene_extinction

[2]: https://en.wikipedia.org/wiki/Intergovernmental_Science-Poli...

[3]: https://en.wikipedia.org/wiki/Global_Assessment_Report_on_Bi...

I don’t think it’s necessarily the commenter’s solution but it does seem to be the one the world is going all in on.

It's hard to take something away from people once they have already had it. Yet if we had never discovered flight then we wouldn't spend much time lamenting the lack of air travel. Instead we would get on with life within the limitations we have just like we do for other constraints.

Nobody in this thread has suggested that.

Someone has now: https://news.ycombinator.com/item?id=27725760

True, but when you start comparing denominators in absolute terms you would also conclude that not traveling at all is the far superior choice. And also, that anything emitter (say, a gas grill) that’s unrelated to travel has infinite emissions per kilometer.

And if we use your co2 per mile approach we can all conclude that a rocket is the way to travel.

People judge these things in terms of how much co2 is emitted by industry, companies, individuals etc. The particular mechanism of emissions is not that relevant. Air ambulance flights are treated differently to private jets carrying bankers.

Why is further travel, per se, the problem?

> While on many routes a car is worse in terms of CO2 emission per trip than a small to mid sized airliner if there are less than 3 people in the car.

Wow. I read that one plane trip can increase your carbon footprint by a greater magnitude than all your typical actions to reduce it.

Does anyone know where to find some data?

EDIT: Here's some data https://www.bbc.com/news/science-environment-49349566

https://theicct.org/blogs/staff/planes-trains-and-automobile...

Also, planes have other problems:

* cars can be powered by carbon-free energy. There's not much current prospect for planes.

* planes also do great harm from non-CO2 emissions: "The climate effect of non-CO2 emissions from aviation is much greater than the equivalent from other modes of transport, as these non-CO2 greenhouse gases formed at higher altitudes persist for longer than at the surface and also have a stronger warming potential"

Jet engines are pretty robust to fuel quality within broad ranges. Atmospheric CO2 to a carbon-neutral jet fuel is technically possible now. (I don’t think it competes economically with Jet-A/kerosene/diesel at the moment.)

> While on many routes a car is worse than a small to mid sized airliner if there are less than 3 people in the car.

I never said cars. Cars are terrible. I would not complained if passenger-only cars were banned everywhere.

> Similar for your suggestion that we should take ships over the ocean, because cruise ships are much more polluting per passenger mile than modern airliners.

There are alternatives like wind power + giant batteries. The fact that weight doesn't matter for ships so much (container ships are more efficient than rail, scaling up is equivalent to shrinking the viscosity of water) opens a lot of doors.

Air travel is generally more energy efficient than trains, beyond a 300-400 mile range, depending on what you're traveling over/through.

Track and right-of-way is a scarce resource with large amounts of embedded energy. The sky, not so much.

That depends on passenger volume. Trains require massive initial investments, but the marginal cost per passenger is very low. Air travel is mostly about marginal costs, and it requires massive infrastructure at endpoints. For example, an aiport serving 50 million passengers/year is two orders of magnitude larger than a railway station with a similar passenger volume. And while the airport would be one of the 30-40 busiest in the world, the railway station would not be particularly noteworthy.

Yea, which is why trains costs are so sensitive to distance- it's massive up front cost is a function of that distance. It's not the stations, it's the rails and right-of-way.

The problem most people ignore is that train marginal-increases max-out at some number of trains per day, before you need an additional set of tracks.

And that happens at a much lower number than most people assume, especially if you're planning on sharing that track with other routes. And even worse if you have to use or cross a freight track.

So not only does efficiency have a min bounds, but also a local-max bounds, where you need a large enough marginal increase to justify the additional rails.

Whereas the airline equivalent is whether to schedule an additional flight. Which is easier to commit to than whether a new track is justified.

Train costs are sensitive to sparsely populated regions. As long as there is a sufficiently large city every hour or so, distances don't really matter.

Multi-track railways are common near major cities. They are not that expensive, because adding another set of tracks increases the width of the corridor only marginally.

The airline equivalent of a new set of tracks is building a new runway. Because that's often impossible, landing slots at busy airports have become very valuable. For example, airlines have paid tens of millions for a daily landing slot at Heathrow.

"Multi-track railways are common near major cities. They are not that expensive, because adding another set of tracks increases the width of the corridor only marginally."

About a quarter of all railway passengers in Czechia take the suburban trains around Prague.

We sorely need extra sets of tracks from all directions, because the current tracks are overloaded. Especially the faster trains from other regions do not mix well with the regional trains that stop every 2 km or so.

But it is almost impossible to build those extra sets of tracks in a densely populated major city like Prague. Lots of NIMBYs, the needed land would be very expensive, many buildings would have to be torn down, plus the centre is a protected zone (historical buildings) and the protecting authorities fight tooth and nail against anything that changes the look and feel of the inner city.

As a result, we are stuck with old infrastructure even if new one is sorely needed. There might be a way, namely, to build all the new tracks underground - but that would be very, very expensive.

Do it as subways in a way like the new lines in Barcelona did.

edit: By that I mean something like illustrated here https://ca.wikipedia.org/wiki/L%C3%ADnia_9_del_metro_de_Barc...

Make them 15 to 16 meters in diameter to be usable by any train, or use 2 of them side by side. Problem mostly solved.

It can be done, but geology under Prague is terrible. A lot of broken layers with lots of sediments and water.

Our subway system was rather expensive to build and maintain, doing this with trains would probably be too expensive even for a fairly rich city like Prague.

There are some rudimentary plans for railway tunnels under the very center of the city, but the expected cost is eye-watering.

Tap into the limitless cornucopia of the EU. For protecting the historic scenery, cultural heritage, being good for the environment, enabling shorter travel times, supporting tourism, intercultural exchange...

We're in a phase of low interest rates, resulting in easy money politics. Burn some billions before others do ;->

>"Whereas the airline equivalent is whether to schedule an additional flight. Which is easier to commit to than whether a new track is justified."

Except many world's biggest airports, like Heathrow, are operating at peak capacity and building another runway at heathrow is expensive, controvertial, involves relocating people's homes and is still a political football

Air still has the advantage- runway is not a function of distance to the destination, and runways are not destination specific.

So it's more appropriate to compare it to part of the station cost, along the lines of another boarding area & track, increasing arrivals and departures.

With dedicated track, though, those limits can be quite high. The Yamanote Line in Tokyo carries around 4 million passengers per day on two tracks.

Yes- and imho, that's the way to do it. Make it competitive in terms of time and trouble and cost and usability. But it's still not going to be more energy efficient than air for most situations & destinations.

The key point, though, is that there should be no easy way for individuals to travel beyond 3-400 miles. It simply is not possible, today or in the foreseeable future, to travel this far without outsized environmental impacts.

But...FREEDOM!

... and fast fashion is probably worse than both if what I read is correct.

FTR: Years go by between everytime I travel by plane so I don't feel I have anything to defend, I just think it is good to keep the big picture in mind.

Agree, and the airlines absolutely need to keep working to become more climate friendly just like we need to make road travel better.

But climate-shaming specifically air travel while at the same time driving a non-electric car or using air conditioning without having solar panels is very hypocritical because both of those and many other things are a far bigger part of the total emissions.

People insulting others as hypocritical for critizing something needs to stop.

It's not an insult. What you call criticising, climate shaming someone over one activity while engaging in other more polluting activities, is the exact definition of the word hypocrisy:

> Hypocrisy is the practice of engaging in the same behavior or activity for which one criticizes another

We coupd sctuallu fly even more efficiently, but slower, with turboprops

There’s a practical maximum amount of thrust to get from a single turboprop engine; to meet performance requirements in the event of the failure of one engine, that puts a practical upper limit on the size of two engine turboprops. Four engine turboprops would likely not be competitive with modern two engine jets, except on the shortest of legs.

Turboprops also fly lower, meaning they’re much more affected by en route weather that turbojets can often climb over. (Low and mid twenties [thousands of feet] is where much of the uncomfortable weather is. Storms that rise into the mid-30s are diverted around by most airplanes.)

Turboprops have their place, but so do jets in air carrier ops.

It looks like the future is a bit of a mashup of a turboprop and turbofan. Check out the efficiency of the Pratt and Whitney geared turbofans. On the A220-100 fuel burn (~3,800 pph) is comparable to a CRJ-900 with 35 more seats in a dual class configuration. That’s quite a leap. I’ll see if I can find someone to compare it to a B717 fuel burn, it’s the same number of seats.

On the the other hand commercial air travel is one of the safest means of travel. If you wanted to optimize for safety you would take a scheduled flight to your destination than go by road.

Ah, well. You think so. But would that hold up if traveling by air so much more, for so many shorter trips? What could go wrong?