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In the spirit of David MacKay's wonderful freely available book "Sustainable Energy – without the hot air" let's do a back-of-the-envelope estimate to roughly q

by shoo 6y ago

In the spirit of David MacKay's wonderful freely available book "Sustainable Energy – without the hot air" let's do a back-of-the-envelope estimate to roughly quantify how bad: The aircraft is a Qantas B787-9 Dreamliner with 236 seat passenger capacity [1]. This trip took 134 passengers and lasted for 7 hours [2]. A Boeing B787-9 has a fuel consumption of roughly 5600 kg fuel / hour [3]. Following the Australian government, we assume the aircraft is 100% fueled by Aviation Turbine Fuel [4] aka "avtur" aka Jet A1. Jet A1 fuel has an emissions factor (kg CO_2 / kg fuel) of 3.15 [5] . Note: this emissions factor is pretty close to a naive estimate of how much CO_2 you'd get if you burned petroleum ( 1kg of petroleum at 85% C by mass gives 0.85 kg of C gives mass(C) * molar_mass(CO_2) / molar_mass(C) = 3.12 kg CO_2 ). So, fuel burned per passenger = (7 hours * 5600 kg fuel / hr ) / 134 passengers = 293 kg fuel / passenger. CO_2 emissions per passenger = 293 kg fuel / passenger * 3.15 kg CO_2 / kg fuel = 922 kg CO_2 . But, we're not just burning things at ground level, we're burning jet fuel in the sky, which the 1999 IPCC special report on "aviation and the global atmosphere" explains has an additional impact in terms of radiative forcing. As summarised by MacKay: > Is flying extra-bad for climate change in some way? Yes, that’s the experts’ view, though uncertainty remains about this topic [[ 6 ]]. Flying creates other greenhouse gases in addition to CO2, such as water and ozone, and indirect greenhouse gases, such as nitrous oxides. If you want to estimate your carbon footprint in tons of CO2-equivalent, then you should take the actual CO2 emissions of your flights and bump them up two- or three-fold. [7] So using MacKay's suggested 2x -- 3x multiplier, we get: Global warming impact per passenger for a single 7 hour flight to nowhere: equivalent to around 1.8 -- 2.8 metric tons of non-aviation CO_2 emissions. For reference, that's around 7 -- 11% of an average Australian per-capita annual climate footprint, or 19% -- 29% of an average EU28 per-capita annual climate footprint [8]. [1] https://www.qantas.com/au/en/qantas-experience/onboard/seat-maps/boeing-787-9.html https://www.qantas.com/au/en/qantas-experience/onboard/seat-... [2] https://www.qantas.com/au/en/promotions/great-southern-land.html https://www.qantas.com/au/en/promotions/great-southern-land.... [3] https://alliknowaviation.com/2019/12/14/fuel-consumption-aircraft/ https://alliknowaviation.com/2019/12/14/fuel-consumption-air... [4] https://www.infrastructure.gov.au/aviation/environmental/emissions/files/Managing-the-Carbon-Footprint-of-Australian-Aviation.pdf https://www.infrastructure.gov.au/aviation/environmental/emi... [5] https://www.verifavia.com/greenhouse-gas-verification/fq-how-are-aircraft-co2-emissions-calculated-11.php https://www.verifavia.com/greenhouse-gas-verification/fq-how... [6] https://www.researchgate.net/publication/224795892_Aviation_and_the_Global_Atmosphere_Summary_for_Policy_Makers https://www.researchgate.net/publication/224795892_Aviation_... [7] http://www.withouthotair.com/c5/page_35.shtml http://www.withouthotair.com/c5/page_35.shtml [8] http://climatecollege.unimelb.edu.au/ndc-indc-factsheets http://climatecollege.unimelb.edu.au/ndc-indc-factsheets

lightgreen 6y ago
> you should take the actual CO2 emissions of your flights and bump them up two- or three-fold Why two-three? Why not 1.1-1.2? Why not 10-20? > that's around 7 -- 11% of an average Australian per-capita annual climate footprint And just to be fair, most people cannot afford long-haul flight, only richer people can. So it's rich people who produce CO2 when flying, but the same rich people produce more CO2 when they do everything else. The argument let's ban flying because rich people produce CO would become the argument as let's ban building new houses with concrete, because only rich people can afford them, and concrete emits CO2. Total emission of CO2 from all aviation including freight including poor countries is about 2% of all CO2 emissions.
- shoo 6y ago
  > > you should take the actual CO2 emissions of your flights and bump them up two- or three-fold > Why two-three? Why not 1.1-1.2? Why not 10-20? Read the IPCC special report on aviation and global atmosphere and look at the discussion about radiative forcing -- they give estimates of the impact in terms of radiative forcing from aviation CO_2 alone and also from various other non CO_2 factors caused by aviation: https://www.researchgate.net/publication/224795892_Aviation_and_the_Global_Atmosphere_Summary_for_Policy_Makers https://www.researchgate.net/publication/224795892_Aviation_...
  - lightgreen 6y ago
    OK, I got it. TL;DR effects of contrails is actually higher than from _accumulated_ CO2. It's very interesting, I did not know that. So if we continue flying, we will continue increasing CO2, but the effect of contrails will stay the same, and relatively effect of contrails will be lower. So, again, the effect is very interesting, I did not know about it. But the conclusions you made are probably oversimplified and inaccurate.

by shoo 6y ago

lightgreen 6y ago

> you should take the actual CO2 emissions of your flights and bump them up two- or three-fold Why two-three? Why not 1.1-1.2? Why not 10-20? > that's around 7 -- 11% of an average Australian per-capita annual climate footprint And just to be fair, most people cannot afford long-haul flight, only richer people can. So it's rich people who produce CO2 when flying, but the same rich people produce more CO2 when they do everything else. The argument let's ban flying because rich people produce CO would become the argument as let's ban building new houses with concrete, because only rich people can afford them, and concrete emits CO2. Total emission of CO2 from all aviation including freight including poor countries is about 2% of all CO2 emissions.

shoo 6y ago
> > you should take the actual CO2 emissions of your flights and bump them up two- or three-fold > Why two-three? Why not 1.1-1.2? Why not 10-20? Read the IPCC special report on aviation and global atmosphere and look at the discussion about radiative forcing -- they give estimates of the impact in terms of radiative forcing from aviation CO_2 alone and also from various other non CO_2 factors caused by aviation: https://www.researchgate.net/publication/224795892_Aviation_and_the_Global_Atmosphere_Summary_for_Policy_Makers https://www.researchgate.net/publication/224795892_Aviation_...
- lightgreen 6y ago
  OK, I got it. TL;DR effects of contrails is actually higher than from _accumulated_ CO2. It's very interesting, I did not know that. So if we continue flying, we will continue increasing CO2, but the effect of contrails will stay the same, and relatively effect of contrails will be lower. So, again, the effect is very interesting, I did not know about it. But the conclusions you made are probably oversimplified and inaccurate.