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Homework Help: Methane and CO2 atmospheric lifetime math problem

  1. Nov 24, 2013 #1
    1. The problem statement, all variables and given/known data

    On a per-molecule basis, methane is 26 times more effective as an infrared absorber than is CO2. Calculate the corresponding ratio on a per-unit-mass basis, and compare it with the 20-year GWP for methane. What's the reason for any discrepncy you find?
    (CO2 atmospheric lifetime = 1000 years, GWP relative to CO2 is 1 in 20 years)
    (Methane atmospheric lifetime = 11 years, global warming potential relative to CO2 in 20 years is 23)

    2. Relevant equations

    3. The attempt at a solution

    I am not sure how to start this problem. I think I need to make a ratio between methane and CO2 but am not sure if that is right or how to do so.
  2. jcsd
  3. Nov 26, 2013 #2
    It gives you the ratio between their effectiveness per molecule. How to change this ratio considering the effectiveness per mass instead of molecule?
  4. Nov 26, 2013 #3


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    Suppose 1 molecule of CO2 has absorption rating X.
    Complete the following:
    1 molecule of methane has absorption rating ...
    1 molecule of methane has mass ... atomic units
    1 molecule of CO2 has mass ... atomic units
    ... atomic units of CO2 has absorption rating X
    1 atomic unit of CO2 has absorption rating ...
    1 atomic unit of methane has absorption rating ...
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