What's the True Carbon Footprint of Flying?

We usually just talk about the plane, but it is a lot bigger than that.

It's a constant source of discussion on TreeHugger and a battle with our consciences about whether we should be flying or not. I recently flew and justified it this way:

I am flying to Portugal to try to convince a couple of hundred people that we need to decarbonize our buildings and our transportation (which means less flying) and that we have to use less of everything (including airplanes). I get the contradiction and even the hypocrisy, but I am not ashamed; it's my job. I think I am good at it and that I make a difference doing it.

And besides, flying is only responsible for two percent of emissions. That's not so bad, is it? I even quoted some climate scientists writing on Ensia that it is not so bad, and that we should be "thoughtful and selective about all travel."
Writing in Ensia in response to that article, Parke Wilde is having none of this. He's the professor at Tufts University who is trying to get academics to stop flying, and whom I quoted last year when I tried to justify my first trip to Portugal. He says the emissions are far higher. The latest numbers put flying at 2.97 percent in 2017, and that's just the beginning.

Aviation is responsible for more “radiative forcing” or (roughly speaking) climate impact than one would expect from the carbon emissions alone, because the emissions take place at high altitude where they induce contrail formation. The U.K. uses a multiplier of 1.9, meaning that the full climate impact of aviation is almost twice as great as the statistics above would indicate.

Wilde also notes that we are only looking at the emissions from the jet fuel burn, and not the impact of "transportation to the airport, the energy emissions to produce and transport jet fuel, the ground operations for airports, and the embedded emissions for everything from the aircraft themselves to the airport infrastructure."

Arne Müseler via Wikipedia/CC BY 3.0

I am illustrating this post with photos of the new Beijing Daxing Airport, 7,500,000 square feet of swirly Zaha concrete that will be the busiest airport in the world. It's made of 52,000 of steel and 1.6 million cubic meters of concrete, which includes about 14 percent cement, the manufacture of which pumped out about 656,000 tonnes of CO2*. A flight from New York to Beijing generates 1.5 tons of CO2 per person, so building the airport put out as much CO2 as flying 433,000 people to it.

Arne Müseler via Wikipedia/CC BY 3.0

And we haven't even started with the trains and highways getting us to and from the airports, or the planes themselves; a 737 weighs about 41,000 kg (90,000 lbs), mostly virgin aluminum and magnesium alloys engineered specifically for airplanes. Making a kg of aluminum puts out 12kg of CO2 so that's almost 450,000 Kg of CO2 to build each plane.

We really don't know where it ends. What's the footprint of the meal we ate on the plane, with its disposable plastic packaging? It all adds up to a number that is far greater than just the fuel burn. Yet all over the world people are building new giant airports and new planes to fly between them.

Arne Müseler via Wikipedia/CC BY 3.0

Just with the radiative forcing, aviation could be equivalent to 6 percent of CO2 emissions. Add in everything else, and it's likely way higher.

It's also something that we actually have some ability to control personally, if we really want to, if we really have the discipline and the will to say no. I am not sure my original justification is good enough anymore.

*"the manufacture of which pumped out about 656 million tons of CO2" – this seemed incredibly high. it is. it should be 656 million kilograms or 656 thousand tons of CO2. half a million flights.

Here's the math:
1.6 million cubic meters of concrete: Source: Reuters.
The CO2 produced for the manufacture of structural concrete (using ~14% cement) is estimated at 410 kg/m3 Wikipedia "The CO2 emission from the concrete production is directly proportional to the cement content used in the concrete mix; 900 kg of CO2 are emitted for the fabrication of every ton of cement, accounting for 88% of the emissions associated with the average concrete mix."