rationalskepticism.org

I've had it in my mind for 15 years at least that air travel is bogeyman number 1 as far as AGW goes, ever since an environmental economics module at uni. What's the scientific understanding today? I suppose my personal main gripe with air travel in particular is that it's overwhelmingly completely unnecessary. Commercial passenger flights have been around for 5 minutes, in terms of the time humans have been on the planet, yet many now seem to use them as if their happiness depends on them.

https://en.wikipedia.org/wiki/Environmental_impact_of_aviation

This does not strike me as being a well put together page, unfortunately. EG:

The level and effects of CO2 emissions are currently believed to be broadly the same regardless of altitude (i.e., they have the same atmospheric effects as ground-based emissions).

But then further down the page:

For perspective, per passenger a typical economy-class New York to Los Angeles round trip produces about 715 kg (1574 lb) of CO2 (but is equivalent to 1,917 kg (4,230 lb) of CO2 when the high altitude "climatic forcing" effect is taken into account)