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Thread: What's better; CO2 high in the atmosphere or low in the atmosphere?

  1. #1 What's better; CO2 high in the atmosphere or low in the atmosphere? 
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    Hi,

    I was wondering if it would be better for planes to fly higher or lower, or if it does not matter when it comes to the effect CO2 has on the environment. Of course CO2 in lower parts of the atmosphere would probably be worse for the actual environment itsself (forests etc.) but does flying higher impact the ozone more or does it really not matter?


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    Genius Duck Dywyddyr's Avatar
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    I don't know about the effects altitude with regard to CO2 but I can tell you that aircraft engines (jet at least) are far more efficient at high altitude.
    So even if it turned out that CO2 is "better" being produced at low altitude there'd also be the question of offset: vastly more CO2 would be produced by having aircraft fly lower and that could well outweigh any advantage (if there is one) of it being done at lower levels.


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    Forum Ph.D.
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    My understanding is that for climate purposes it won't make a difference; it ends up well mixed over short time scales compared to how long it hands around. Atmospheric circulation - Hadley cells, Ferrel cells, Polar cells - mix high and low atmosphere around very effectively. Whilst there are climate consequences at lower altitudes - more radiant heat gets re-radiated back down from atmosphere above - it is ultimately the slowed rate of heat radiated by the upper atmosphere out to space that influences the overall balance of heat coming in to heat going out. That lower atmosphere effect is small compared to heat being moved about by atmospheric circulation.
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    Your Mama! GiantEvil's Avatar
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    Quote Originally Posted by Dywyddyr View Post
    I don't know about the effects altitude with regard to CO2 but I can tell you that aircraft engines (jet at least) are far more efficient at high altitude.
    So even if it turned out that CO2 is "better" being produced at low altitude there'd also be the question of offset: vastly more CO2 would be produced by having aircraft fly lower and that could well outweigh any advantage (if there is one) of it being done at lower levels.
    Is the greater efficiency due mostly to less drag on the fuselage from less dense atmosphere, or is it significantly for the engine?
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    Genius Duck Dywyddyr's Avatar
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    Quote Originally Posted by GiantEvil View Post
    Is the greater efficiency due mostly to less drag on the fuselage from less dense atmosphere, or is it significantly for the engine?
    Sort of both.
    The less drag then the faster the aircraft can fly. The faster it flies the more efficient the engine - ideally exhaust velocity should be as close to flight speed as possible. Of course you could configure the engines to produce less thrust (i.e. match them to slower speeds), but then the 'plane would be flying for longer and producing more CO2.
    Down low (even ignoring increased drag) gives a denser atmosphere and more kinetic heating/ loading (= higher structure weights and/ or more costly materials).
    Last edited by Dywyddyr; October 9th, 2017 at 11:03 PM.
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    Your Mama! GiantEvil's Avatar
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    Quote Originally Posted by Dywyddyr View Post
    Quote Originally Posted by GiantEvil View Post
    Is the greater efficiency due mostly to less drag on the fuselage from less dense atmosphere, or is it significantly for the engine?
    Sort of both.
    The less drag then the faster the aircraft can fly. The faster it flies the more efficient the engine - ideally exhaust velocity should be as close to flight speed as possible. Of course you could configure the engines to produce less thrust (i.e. match them to slower speeds), but then the 'plane would be flying for longer and producing more CO2.
    Down low (even ignoring increased drag) gives a denser atmosphere and more kinetic heating/ loading (= higher structure weights and/ or more costly materials).
    Makes sense. Thanks!
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