Jeff Engr asked in EnvironmentGlobal Warming · 7 years ago

Methane - CH4 - is an irrelevant GHG?

I just read a very interesting article that makes some very interesting points.

1. CH4 is a very powerful GHG when taken in isolation. well known and very much discussed on this site.

2. CH4 is irrelevant in the real world earth atmosphere. Due to the fact that its absorption bands for light are within the absorption bands of water vapor. given that water vapor is a much larger part of our atmosphere the GHG impact of CH4 is irrelevant.

Of course #2 would have to assume that the ppm for CH4 in the atmosphere remains very small in comparison to water vapor.

I find this concept very interesting. Does anyone have any non-political data sources that might demonstrate errors in this idea?


I am very much interested in the idea that CH4 in the bands identified is purported to nearly completely eclipsed by water vapor.

On the higher altitudes and being colder thus a higher relative concentration of CH4 vs water vapor. Wouldn't these higher elevations also have a relatively lower net impact as GHG given that more f the irradiative heat released in the upper atmosphere more readily escapes into space than it would at lower elevations?

8 Answers

  • JimZ
    Lv 7
    7 years ago
    Favorite Answer

    Some1 suggests that CO2 is a much longer lived GHG yet interestingly he can't tell us by how much. The cause requires a very long residence so he obliges with the assumption. I think Raisin is correct, that the most important reason CH4 is not that threatening is because it rapidly decays to CO2; therefore, it has no long term threat. The residence time for CO2 is more controversial. If it is short, than methane and CO2 aren't nearly as big a threat IMO. GC's point doesn't really address the point of water vapor, which is much more important GHG, Even at altitude and in the cold, I suspect water vapor is much more powerful GHC than CH4. Still even if it adds a bit of heat, it seems to me that it would be temporary and no long term threat. If greenhouse gases won't create a significant threat, then there is no reason to tax it or have the government restrict or control it. That was the point of the article. Jackasses are trying to restrict dairy cows using flawed science that I notice GC has no problem with.

  • Anonymous
    7 years ago

    I think that question still remains unanswered of the affect of various molecules absorbing the same set of wavelengths. CH4 is generally not very important because of it prevalence and its lifetime in the air. It has a half-life of only 12 years in the atmosphere, at which point it usually breaks down to CO2. While it is 34 times more powerful as a GHG than CO2, it is also about 300 time less prevalent.


    I SAY that methane breaks down to CO2 very specifically. As for adding CO2 in the atmosphere, it cause 1 degree of warming per doubling. that is not an underestimation, and is indeed what most climate scientists say.

    I do not pretend the world is ruled by positive feedbacks to the point of more than quintupling the amount of warming. This is where you and I disagree. This is the portion of climate science that is extremely variable. even as a feedback factor, your mdoels don't place as much importance on methane as on additional CO2 and water vapor. So you can pretend I am wrong all you want.

  • Kano
    Lv 7
    7 years ago

    I think is still has some importance as a GHG but not that much,

    One big misconception is that it is a much stronger GHG than CO2, it is not, it is much weaker, why it is consider stronger (wrong word inportant is more like it) is because in it's much smaller concentrations it is not saturated, and there is room for more warming, it could be of some importances but only in extreme cases of large emissions over a short period, say like a major breakdowm of methane chlathrate deposits, the amount of methane emmited by animals is ridiculously unimportant.

  • gcnp58
    Lv 7
    7 years ago

    The radiative forcing from water vapor is a strong function of altitude and temperature, since as temperature decreases so does the vapor pressure of water (until ice forms, at which point water vapor pretty much goes away). In contrast, methane never condenses so its mixing ratio is almost constant with altitude up to the stratosphere (where it reacts with ozone to make water vapor) and with temperature. So if you cool the atmosphere the greenhouse effect from water vapor decreases but it stays the same for methane. This goes back to the idea that water vapor is a feedback, not a forcing, and water vapor by itself can't change global surface temperature. It's just along for the ride as something else forces the radiative balance.

    There is a reason people who understand this subject list methane as having a very high GWP, and it's not because they are ignorant of the relevant IR absorption bands. In contrast, Sheahan does appear to be rather clueless about how the atmosphere and radiative transfer works. In other words, he's a typical climate skeptic. You probably think he's a genius.

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  • John
    Lv 4
    7 years ago

    This link should give you a working knowledge on each of the greenhouse gases. -

    Raisin Caine makes a good point that the concentration levels of CH4 in the atmosphere are small when compared to the amount of CO2 in the atmosphere. The main points that Raisin Caine misses are that methane levels are rising faster than are the CO2 levels and that one of the components that methane breaks down to is CO2. CO2 is much longer lived greenhouse and the added methane only adds to the problems of both the global warming and contributing to the overall amount of CO2 that ends up in the atmosphere. I believe that Raisin Caine greatly under plays the effects of adding more CO2 into the atmosphere, most assuredly when you consider the rate of increase we are observing with the methane levels in the atmosphere. .... When it is all said and done, it is less about the amount of each greenhouse gas that exists in our atmosphere as it is for the potency of each greenhouse gas and its ability to trap heat from returning back into space.

  • Maxx
    Lv 7
    7 years ago

    Another reason why methane is irrelevant is because it only makes up 0.000179% of the atmosphere and it's senseless to think it can have any measurable impact on climate. But any excuse will serve a tyrant, so the Obama Administration is trying to tax cow emissions.

    Watch this short 2 minute video to understand how little methane there is in the air.

    Youtube thumbnail



  • Gringo
    Lv 6
    7 years ago

    <<Does anyone have any non-political data sources that might demonstrate errors in this idea? >>

    How about you use a non-political, non-religious source as a starting point?

    Dr Sheahan (CEO President, Western Technology, Inc Energy Consulting, Vice-president SEPP, Director, Institute for Theological Encounter with Science and Technology) isn't exactly non-political, let alone not influenced by religion.

    If you are looking for unbiased answers, the best ways is to assure that your questions are not biased to start with.

  • 7 years ago

    Ask ur chemistry teacher

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