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Thread: How many physicists agree with Climate Change being caused by CO2?

  1. #1 How many physicists agree with Climate Change being caused by CO2? 
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    I'm not doubting that temperatures are rising. But from a physics standpoint, the argument that CO2 is causing it looks seriously weak sauce.


    Looking it up, Carbon Dioxide only makes up 0.04 % of Earth's atmosphere.


    https://useruploads.socratic.org/TJh..._image253b.gif

    (I apologize, I can't get the image to display here)


    That's not very much. And CO2 isn't a very potent greenhouse gas to begin with.

    Most of Earth's greenhouse comes from evaporated moisture. And evaporated moisture has a kind of feedback effect, like when you put a microphone too near to the speaker that is being used to amplify it. If it's hotter this year, more moisture will evaporate, making it still hotter next year, causing even more moisture to evaporate............ etc.

    So absolutely any warming effect will become a greenhouse effect, after it gets amplified by the evaporated moisture cycle.



    After considering this, we can look at Venus, which is often pointed to as an example of a runaway greenhouse effect. However what we find, is that it's CO2 content is around 97% (quite a bit more than 0.04%). Not only that, but Venus has about 10 times more total atmospheric volume than Earth.

    Temperatures are hot enough to melt lead, and most peoples' ovens in their home can't quite get hot enough to mirror it, but for receiving about 1.7 times the sunlight Earth receives, it's still kind of underwhelming.


    I understand how there can be unanimous, or near unanimous support for the theory in other fields of science. Rising CO2 does correlate strongly with rising temperatures (although any science will tell you: correlation is not necessarily causation...)

    But I don't understand how a physicist can agree with it. The physics are just way off. Or is there something I'm missing here?


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  3. #2  
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    Quote Originally Posted by The Raven View Post
    I'm not doubting that temperatures are rising. But from a physics standpoint, the argument that CO2 is causing it looks seriously weak sauce.


    Looking it up, Carbon Dioxide only makes up 0.04 % of Earth's atmosphere.


    https://useruploads.socratic.org/TJh..._image253b.gif

    (I apologize, I can't get the image to display here)


    That's not very much. And CO2 isn't a very potent greenhouse gas to begin with.

    Most of Earth's greenhouse comes from evaporated moisture. And evaporated moisture has a kind of feedback effect, like when you put a microphone too near to the speaker that is being used to amplify it. If it's hotter this year, more moisture will evaporate, making it still hotter next year, causing even more moisture to evaporate............ etc.

    So absolutely any warming effect will become a greenhouse effect, after it gets amplified by the evaporated moisture cycle.



    After considering this, we can look at Venus, which is often pointed to as an example of a runaway greenhouse effect. However what we find, is that it's CO2 content is around 97% (quite a bit more than 0.04%). Not only that, but Venus has about 10 times more total atmospheric volume than Earth.

    Temperatures are hot enough to melt lead, and most peoples' ovens in their home can't quite get hot enough to mirror it, but for receiving about 1.7 times the sunlight Earth receives, it's still kind of underwhelming.


    I understand how there can be unanimous, or near unanimous support for the theory in other fields of science. Rising CO2 does correlate strongly with rising temperatures (although any science will tell you: correlation is not necessarily causation...)

    But I don't understand how a physicist can agree with it. The physics are just way off. Or is there something I'm missing here?
    Yes, there is something you are missing here, since the world's climatologists are not all fools, obviously.

    There are others here who know much more about this than I do (PhDemon, for instance, has worked as an atmospheric research chemist), but my limited understanding is that the moisture effect has a self-limiting component due to condensation and rainfall, whereas the CO2 effect is cumulative, so shifts the equilibrium point, at which point the effect of water vapour amplifies the shift. There are plenty of sources of information about this on the web, of which I have read a few. But admittedly there is just so much stuff about this now that it can be hard to zero in on the answer to one particular question.


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    Yep, you are missing something... there is an efficient removal mechanism for excess water vapour from the atmosphere. We smart arse atmospheric scientists call it rain...

    Adding more water vapour to the atmosphere at a given temperature has a negligible effect on warming as it is rained out (having said that, as exchemist points out, once the atmosphere is warmer for other reasons it can hold more water vapour and this feedback is included in the models).

    There is no such removal mechanism for CO2 and this accumulates in the atmosphere.
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    Quote Originally Posted by PhDemon View Post
    Yep, you are missing something... there is an efficient removal mechanism for excess water vapour from the atmosphere. We smart arse atmospheric scientists call it rain...
    Adding more water vapour to the atmosphere at a given temperature has a negligible effect on warming as it is rained out (having said that, as exchemist points out, once the atmosphere is warmer for other reasons it can hold more water vapour and this feedback is included in the models).
    There is no such removal mechanism for CO2 and this accumulates in the atmosphere.
    Then the cause of global warming is that it rains less than before?
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    Idiot.
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    Quote Originally Posted by exchemist View Post

    There are others here who know much more about this than I do (PhDemon, for instance, has worked as an atmospheric research chemist), but my limited understanding is that the moisture effect has a self-limiting component due to condensation and rainfall,
    If I'm not mistaken, from a physics perspective, the limiting mechanism is radiative emission. As the whole world heats up, it begins radiating more energy into space, and eventually this gets strong enough to put a stop to the feedback cycle. (Otherwise a single hot summer could trigger doom!!)


    https://en.wikipedia.org/wiki/Dew_point

    whereas the CO2 effect is cumulative, so shifts the equilibrium point, at which point the effect of water vapour amplifies the shift. There are plenty of sources of information about this on the web, of which I have read a few. But admittedly there is just so much stuff about this now that it can be hard to zero in on the answer to one particular question.
    That's my point: water vapor amplifies the shift. In theory, it would amplify any shift, regardless of the cause.

    It's one thing to believe that a 0.04% component of the atmosphere can cause it. In theory anything can cause it because of the amplification effect.

    It's another to arrive at the conclusion that a 0.04% component is causing it.

    Removing CO2 would be very expensive at this point. It would be quite a shame to actually go to all that expense, and then have the world keep getting warmer anyway.

    Quote Originally Posted by PhDemon View Post
    Yep, you are missing something... there is an efficient removal mechanism for excess water vapour from the atmosphere. We smart arse atmospheric scientists call it rain...

    Adding more water vapour to the atmosphere at a given temperature has a negligible effect on warming as it is rained out (having said that, as exchemist points out, once the atmosphere is warmer for other reasons it can hold more water vapour and this feedback is included in the models).

    There is no such removal mechanism for CO2 and this accumulates in the atmosphere.
    Yes. It does rain out. And also more evaporates.

    It's like how in a rain forest there always some plants dying, and other plants growing. The total volume of plant life can go up or down in spite of this. Even though every plant that is ever born will eventually die.

    But as the temperature goes up, the total amount of moisture that the atmosphere holds at any given time will most likely get higher and higher. And the greenhouse effect generated by that atmospheric moisture will intensify.

    Direct warming/cooling happens when water either evaporates, or is released, but those two direct effects generally cancel each other out in the long run.,
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    The information and evidence that warming is not driven by water vapour is out there and is overwhelming. But you are choosing wilful ignorance. I can't fix that and frankly can't be bothered with those who can't or won't understand it.
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    Quote Originally Posted by PhDemon View Post
    The information and evidence that warming is not driven by water vapour is out there and is overwhelming. But you are choosing wilful ignorance. I can't fix that and frankly can't be bothered with those who can't or won't understand it.
    If by "out there" you mean dam near impossible to find, then maybe. You won't get anything useful from a Google search.

    Remember, though, that it's not "driven by" water vapor. It's *amplified* by water vapor.

    Imagine if you have a sound amplification system in the center of a football field. A sensitive microphone and loud speaker that picks up any nearby noise and amplifies it into the speaker. A deer 100 meters away steps on a twig, and it gets picked up by the microphone.

    Where will you hear the most noise? By the deer? Or by the loud speaker that amplified the noise?


    I'm not ruling out CO2. I just want some strong evidence. Something that requires less suspension of disbelief than a religion requires. The threat of an "eternity in hell for nonbelievers" sounds awful similar to the "existential threat of a permanently warmed earth" if we don't act fast.

    For as many scientists, hundreds, even thousands who have taken interest in this, I think it is reasonable for the public to expect a better articulation of evidence. It's disappointing for so many apparently capable minds to build such a flimsy and scattered narrative.

    Have there been any actual laboratory tests using a sunlamp to warm a region covered in air that has 0.04% CO2 . Even if they raised the amount to compensate for the light passing through only a meter of such air (as opposed to the 100,000+ meters between us and space). If they can show that measurable warming would occur from the slight change from 0.035 to 0.041 or so, that would be really helpful. (Although they also need to account for differences in volume, total mass, and total illumination.)


    By my estimate, Venus has more than 20,000 times more CO2 per square meter of surface area than does Earth. It receives somewhere between 1.7 and 1.9 times as much Sun. But it's only about 9 times a hot.
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    I think maybe this will turn out to be what I'm looking for, or the area to research.

    https://en.wikipedia.org/wiki/Carbon...9;s_atmosphere

    Since you two seemed so convinced of CO2's ability to do what is claimed, even at 0.04% concentration, I decided to devote time to reading about CO2's properties, and see what could possibly explain it.

    I guess the reason CO2 is so ineffective in Venus' situation is because Venus, being hotter, emits IR radiation at a higher frequency than Earth.

    But in Earth's case, it's a very close match to Earth's present blackbody peak emission at the surface. I guess? So until the Earth gets 100 degrees hotter or something, CO2 will be a kind of "perfect match" which makes it an ideal greenhouse gas on Earth, but not so ideal on Venus.

    I'm having trouble getting the exact numbers for that, because some sources report the total black body average to space, and what we need is black body emission rates at the surface. But I'm willing to take it on faith for now that the emission/absorption spectra line up.



    If that's the argument, then I think I can run with that.

    I've been trying to decide if it's really worth it to reduce the Earth's CO2 levels, or if that's going to turn out to be a giant rabbit hole that you get to the bottom of only to find out nothing has been solved.

    One of the classic scams people often fall for is the "Rain Maker" scam. A variation of which is to propose a task to someone that is so large they can't possibly achieve it, and then keep telling them that they need to achieve it in order to get a reward. Always being careful to make sure no matter how much they do it "isn't enough yet".

    But I think the CO2 problem can be solved. Just want to make sure it's gonna be worth the price.
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    The further you study the clearer it will be that there is no Big Mistake or Big Omission. Or Big Lie. Climate science got to where it is legitimately, the hard way. Harder than other important science based understandings because economic interests, that base their preferred position on how addressing it affects short term business costs, competitiveness and profitability rather than how climate change itself works or impacts anything, have sought to prevent and delay economy wide responses by encouraging misinformation and misunderstandings. By doubt, deny, delay. "But CO2 is small" is one such false argument along with "but scientists just say it to keep getting funding" and other slanders. If the scientists were incompetent and wrong it would only take competent science to show it; despite decades of trying to show mainstream science is wrong, follow up studies persistently show the science is right.

    CO2 is the biggest single factor, confirmed by multiple independent studies, with other GHG's (CH4 and N2O mostly) adding more.

    0.04% may not sound like much but the atmosphere is many kilometres thick; it was already enough concentration to absorb most Long UV between Earth and space before we raised them. About 1/3rd of (enhanced) Ghg warming comes from CO2 (and other GHG's) directly, about 2/3rds from the water vapor rise the warming from that CO2 induces; it gets counted as from the CO2 because we don't get the raised water vapor content without the CO2 rise. It is a consequence of warmer air holding more water vapor.

    It wasn't until all the conceivable factors that can cause global average temperatures to change were quantified (mid to late 1970's) that we got a firm, science based conclusion that CO2 is the dominant factor. Multiple independent studies confirm the relative influence of those factors. These are the ones that were found to have some impact over the time scales under consideration; others, like internal (volcanic) heat, orbital changes have been found to be far too small and, whilst not ignored, are passed over for practicality.
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    Quote Originally Posted by Ken Fabos View Post
    it gets counted as from the CO2 because we don't get the raised water vapor content without the CO2 rise. It is a consequence of warmer air holding more water vapor.
    Even this being true, it still hurts climatologists' credibility.

    You must try to understand that, from the perspective of history, science hoaxing is nothing new.

    Lysenkoism was used by Joseph Stalin to deliberately inflict hunger on the people of the Soviet Union, because in the fallout of it, he got to pick who would starve. Nobody dared oppose him for that reason. Now Climate Change is being used to disrupt supply chains, which may soon cause quite a lot of hunger. The threat of famine is exactly the tactic that was used to institute the USSR, and execute the Tsar in the first place. It's a powerful tool if you want to restructure the political landscape toward totalitarianism. (The draw back being that you'll have to keep using it, if you want that totalitarian regime to stay in power.)


    You shouldn't fool yourself that everybody wants the economy to run well. People are becoming increasingly jealous of successful industrialists, but kind of ignoring the banks right now (especially Wall Street itself).

    Does that mean the science is bad? No.

    Does it mean it's good? No.

    Only looking at the data itself can tell you that. Consensus arguments, historically, are only used by people who can't prove their point with evidence. Consequently I'm ignoring the number of scientists who agree, because I don't think it matters.





    It wasn't until all the conceivable factors that can cause global average temperatures to change were quantified (mid to late 1970's) that we got a firm, science based conclusion that CO2 is the dominant factor. Multiple independent studies confirm the relative influence of those factors. These are the ones that were found to have some impact over the time scales under consideration; others, like internal (volcanic) heat, orbital changes have been found to be far too small and, whilst not ignored, are passed over for practicality.
    Yeah, I've looked into the orbital argument, and we're simply in the wrong part of the Milankovich cycle to be experienced any kind of serious warming. Volcanic eruptions are known to sometimes cool the Earth, if they expell enough sulfur.

    There was an article I found about Pluto getting warmer, and suggesting a change in our Solar system's location in the galaxy, but Pluto's warming almost certainly IS being caused by orbit (in that Pluto is reaching a point in its long orbit where it gets closer to the Sun.)

    I'm not so much interested in proving CO2 isn't the cause. More I just want to be totally sure before I accept. Anytime you do anything real with the economy, you are placing a bet. And it it's something like this, where the economic investement required to make a difference is extremely large, you really can't bet it on a weak probability.
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  13. #12  
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    Quote Originally Posted by The Raven View Post
    I think maybe this will turn out to be what I'm looking for, or the area to research.

    https://en.wikipedia.org/wiki/Carbon...9;s_atmosphere

    Since you two seemed so convinced of CO2's ability to do what is claimed, even at 0.04% concentration, I decided to devote time to reading about CO2's properties, and see what could possibly explain it.

    I guess the reason CO2 is so ineffective in Venus' situation is because Venus, being hotter, emits IR radiation at a higher frequency than Earth.

    But in Earth's case, it's a very close match to Earth's present blackbody peak emission at the surface. I guess? So until the Earth gets 100 degrees hotter or something, CO2 will be a kind of "perfect match" which makes it an ideal greenhouse gas on Earth, but not so ideal on Venus.

    I'm having trouble getting the exact numbers for that, because some sources report the total black body average to space, and what we need is black body emission rates at the surface. But I'm willing to take it on faith for now that the emission/absorption spectra line up.



    If that's the argument, then I think I can run with that.

    I've been trying to decide if it's really worth it to reduce the Earth's CO2 levels, or if that's going to turn out to be a giant rabbit hole that you get to the bottom of only to find out nothing has been solved.

    One of the classic scams people often fall for is the "Rain Maker" scam. A variation of which is to propose a task to someone that is so large they can't possibly achieve it, and then keep telling them that they need to achieve it in order to get a reward. Always being careful to make sure no matter how much they do it "isn't enough yet".

    But I think the CO2 problem can be solved. Just want to make sure it's gonna be worth the price.
    I'm not sure why you keep banging on about CO2 being 0.04% of the atmosphere. What counts is what gases absorb in the IR. Most of the gases in the atmosphere are non-polar diatomic molecules. As such they do not absorb in the IR at all. So they are irrelevant.

    It has now been explained to you that although water vapour does absorb, it is self-limiting at any given temperature, due to precipitation. That leaves the others that do not limit themselves by precipitation. CO2 is one of them. Methane is another (though there is a removal process for that, by eventual chemical decomposition).

    If you serious about wanting to understand why the models focus so much on CO2, I suggest you read one of the many explanation of these models on the internet and revert to us with specific points that you have difficulty with.

    Forget Venus for the moment, the situation there is totally different - not least the presence of sulphuric acid vapour.
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    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by The Raven View Post
    I think maybe this will turn out to be what I'm looking for, or the area to research.

    https://en.wikipedia.org/wiki/Carbon...9;s_atmosphere

    Since you two seemed so convinced of CO2's ability to do what is claimed, even at 0.04% concentration, I decided to devote time to reading about CO2's properties, and see what could possibly explain it.

    I guess the reason CO2 is so ineffective in Venus' situation is because Venus, being hotter, emits IR radiation at a higher frequency than Earth.

    But in Earth's case, it's a very close match to Earth's present blackbody peak emission at the surface. I guess? So until the Earth gets 100 degrees hotter or something, CO2 will be a kind of "perfect match" which makes it an ideal greenhouse gas on Earth, but not so ideal on Venus.

    I'm having trouble getting the exact numbers for that, because some sources report the total black body average to space, and what we need is black body emission rates at the surface. But I'm willing to take it on faith for now that the emission/absorption spectra line up.



    If that's the argument, then I think I can run with that.

    I've been trying to decide if it's really worth it to reduce the Earth's CO2 levels, or if that's going to turn out to be a giant rabbit hole that you get to the bottom of only to find out nothing has been solved.

    One of the classic scams people often fall for is the "Rain Maker" scam. A variation of which is to propose a task to someone that is so large they can't possibly achieve it, and then keep telling them that they need to achieve it in order to get a reward. Always being careful to make sure no matter how much they do it "isn't enough yet".

    But I think the CO2 problem can be solved. Just want to make sure it's gonna be worth the price.
    I'm not sure why you keep banging on about CO2 being 0.04% of the atmosphere. What counts is what gases absorb in the IR. Most of the gases in the atmosphere are non-polar diatomic molecules. As such they do not absorb in the IR at all. So they are irrelevant.
    What matters most is if it is specifically attuned to the particular band of IR where Earths peak emission spikes at.


    It has now been explained to you that although water vapour does absorb, it is self-limiting at any given temperature, due to precipitation. That leaves the others that do not limit themselves by precipitation. CO2 is one of them. Methane is another (though there is a removal process for that, by eventual chemical decomposition).
    I think the overal capacity for holding moisture still goes up with greater temperature, though. And each increase in capacity, will trigger an increase in temperature.

    So its a chicken - egg kind of feedback loop. Earth gets a bit warmer, so total capacity to hold moisture goes up. That increases greenhouse effect, causing temperature to rise again, which increases the airs capacity to hold moisture again, which causes more greenhouse, which increases temperature.............. etc....

    We are dealing with averages, so the specifics of when or where the moisture is absorbed or precipitated only matter insofar as they impact the average temp/capacity.






    If you serious about wanting to understand why the models focus so much on CO2, I suggest you read one of the many explanation of these models on the internet and revert to us with specific points that you have difficulty with.
    Almost everything you can find in a google search is astoundingly simplistic. CO2 = Bad. No really! CO2 BAD!!!!

    But if instead it can be explained that CO2 holds a special place, being tuned specifically to Earths blackbody emission frequency, that helps a lot. Then you realize its kind of like if Earth were a radio station, and CO2 were a radio that has been turned specifically to its channel. EM that would normally bounce off or pass through transparently is being absorbed, and converted to energy by its one perfect partner.

    Ok. Then maybe 0.04% is enough. The same way a radio antenna kilometers away from me can impart enough energy to my car antenna to play me a song.




    Forget Venus for the moment, the situation there is totally different - not least the presence of sulphuric acid vapour.
    Yeah. I have heard that sulfur has a cooling effect.
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    Quote Originally Posted by The Raven View Post
    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by The Raven View Post
    I think maybe this will turn out to be what I'm looking for, or the area to research.

    https://en.wikipedia.org/wiki/Carbon...9;s_atmosphere

    Since you two seemed so convinced of CO2's ability to do what is claimed, even at 0.04% concentration, I decided to devote time to reading about CO2's properties, and see what could possibly explain it.

    I guess the reason CO2 is so ineffective in Venus' situation is because Venus, being hotter, emits IR radiation at a higher frequency than Earth.

    But in Earth's case, it's a very close match to Earth's present blackbody peak emission at the surface. I guess? So until the Earth gets 100 degrees hotter or something, CO2 will be a kind of "perfect match" which makes it an ideal greenhouse gas on Earth, but not so ideal on Venus.

    I'm having trouble getting the exact numbers for that, because some sources report the total black body average to space, and what we need is black body emission rates at the surface. But I'm willing to take it on faith for now that the emission/absorption spectra line up.



    If that's the argument, then I think I can run with that.

    I've been trying to decide if it's really worth it to reduce the Earth's CO2 levels, or if that's going to turn out to be a giant rabbit hole that you get to the bottom of only to find out nothing has been solved.

    One of the classic scams people often fall for is the "Rain Maker" scam. A variation of which is to propose a task to someone that is so large they can't possibly achieve it, and then keep telling them that they need to achieve it in order to get a reward. Always being careful to make sure no matter how much they do it "isn't enough yet".

    But I think the CO2 problem can be solved. Just want to make sure it's gonna be worth the price.
    I'm not sure why you keep banging on about CO2 being 0.04% of the atmosphere. What counts is what gases absorb in the IR. Most of the gases in the atmosphere are non-polar diatomic molecules. As such they do not absorb in the IR at all. So they are irrelevant.
    What matters most is if it is specifically attuned to the particular band of IR where Earths peak emission spikes at.


    It has now been explained to you that although water vapour does absorb, it is self-limiting at any given temperature, due to precipitation. That leaves the others that do not limit themselves by precipitation. CO2 is one of them. Methane is another (though there is a removal process for that, by eventual chemical decomposition).
    I think the overal capacity for holding moisture still goes up with greater temperature, though. And each increase in capacity, will trigger an increase in temperature.

    So its a chicken - egg kind of feedback loop. Earth gets a bit warmer, so total capacity to hold moisture goes up. That increases greenhouse effect, causing temperature to rise again, which increases the airs capacity to hold moisture again, which causes more greenhouse, which increases temperature.............. etc....

    We are dealing with averages, so the specifics of when or where the moisture is absorbed or precipitated only matter insofar as they impact the average temp/capacity.






    If you serious about wanting to understand why the models focus so much on CO2, I suggest you read one of the many explanation of these models on the internet and revert to us with specific points that you have difficulty with.
    Almost everything you can find in a google search is astoundingly simplistic. CO2 = Bad. No really! CO2 BAD!!!!

    But if instead it can be explained that CO2 holds a special place, being tuned specifically to Earths blackbody emission frequency, that helps a lot. Then you realize its kind of like if Earth were a radio station, and CO2 were a radio that has been turned specifically to its channel. EM that would normally bounce off or pass through transparently is being absorbed, and converted to energy by its one perfect partner.

    Ok. Then maybe 0.04% is enough. The same way a radio antenna kilometers away from me can impart enough energy to my car antenna to play me a song.




    Forget Venus for the moment, the situation there is totally different - not least the presence of sulphuric acid vapour.
    Yeah. I have heard that sulfur has a cooling effect.
    The Earth's surface radiates more or less as a black body. So there is no "spike" in IR emission, no "emission frequency" as such. The emission profile is just a curve, covering the entire IR spectrum. CO2 absorbs in certain bands, within the envelope of this curve. (Unlike atoms, molecules do not absorb in sharp lines at a particular frequency. They absorb in bands covering a range of frequency. This is because, for every vibrational excited state, there are a myriad possible rotational states, which combine with the vibrational frequency to generate a wide range of slightly different energy levels.)

    You are right about the feedback loop involving water, which is why water vapour amplifies the effect of the IR-absorbers that accumulate, as has already been pointed out. Also as pointed out previously, because of precipitation, for a given temperature the amount of water vapour tends to stabilise, rather than running away in a +ve feedback loop. It is the cumulative absorbers, those that build up without being removed, which shift the equilibrium, their effect being magnified by the concomitant increase in water vapour content of the atmosphere.
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    Quote Originally Posted by exchemist View Post

    The Earth's surface radiates more or less as a black body. So there is no "spike" in IR emission, no "emission frequency" as such. The emission profile is just a curve, covering the entire IR spectrum.
    This is false. Or at least it is only half true. All blackbodies have a peak emission frequency range. A curve that statistically favors (and often overwhelmingly) a particular frequency, and the frequencies nearest it.

    It's similar to statistical bell curves, where one outcome will happen most frequently, and then you'll see "standard deviations", where about 95% or so of results fall within a certain range, and then 95% of the remainder fall within the next range.......... etc.

    It is true that all frequencies are present *to some degree*, but most of the spectrum outside the peak is vanishingly small in its actual amounts. There is a difference between something being present, and something being present in quantities large enough to noticeably affect an outcome.

    From what I have been able to find researching this topic, the frequency range that Earth's surface emits in noticeable quantities overlaps pretty well with the frequency range that CO2 resonates with. While the frequency range that Venus' surface emits in noticeable quantities does not overlap with CO2's resonant frequency range.

    CO2 absorbs in certain bands, within the envelope of this curve. (Unlike atoms, molecules do not absorb in sharp lines at a particular frequency. They absorb in bands covering a range of frequency. This is because, for every vibrational excited state, there are a myriad possible rotational states, which combine with the vibrational frequency to generate a wide range of slightly different energy levels.)
    Yeah. And that actually makes it more dangerous. Because blackbody doesn't hit a specific, exact frequency. It centers on a narrow range going + or - some amount from that central value. A molecule that absorbs over that range can theoretically capture all of the peak emission values. While a single atom, which might ignore half of it or something, because it is so focused on one, specific value.
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  17. #16  
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    Quote Originally Posted by The Raven View Post
    Quote Originally Posted by exchemist View Post

    The Earth's surface radiates more or less as a black body. So there is no "spike" in IR emission, no "emission frequency" as such. The emission profile is just a curve, covering the entire IR spectrum.
    This is false. Or at least it is only half true. All blackbodies have a peak emission frequency range. A curve that statistically favors (and often overwhelmingly) a particular frequency, and the frequencies nearest it.

    It's similar to statistical bell curves, where one outcome will happen most frequently, and then you'll see "standard deviations", where about 95% or so of results fall within a certain range, and then 95% of the remainder fall within the next range.......... etc.

    It is true that all frequencies are present *to some degree*, but most of the spectrum outside the peak is vanishingly small in its actual amounts. There is a difference between something being present, and something being present in quantities large enough to noticeably affect an outcome.

    From what I have been able to find researching this topic, the frequency range that Earth's surface emits in noticeable quantities overlaps pretty well with the frequency range that CO2 resonates with. While the frequency range that Venus' surface emits in noticeable quantities does not overlap with CO2's resonant frequency range.

    CO2 absorbs in certain bands, within the envelope of this curve. (Unlike atoms, molecules do not absorb in sharp lines at a particular frequency. They absorb in bands covering a range of frequency. This is because, for every vibrational excited state, there are a myriad possible rotational states, which combine with the vibrational frequency to generate a wide range of slightly different energy levels.)
    Yeah. And that actually makes it more dangerous. Because blackbody doesn't hit a specific, exact frequency. It centers on a narrow range going + or - some amount from that central value. A molecule that absorbs over that range can theoretically capture all of the peak emission values. While a single atom, which might ignore half of it or something, because it is so focused on one, specific value.
    No, it is not a narrow range. It is a wide range. That is why I described it as a curve rather than a spike. Of course there is a maximum to this curve, but the emission does not fall off rapidly on either side of the maximum.

    Here is a picture illustrating it: https://www.e-education.psu.edu/eart...3/fig10out.png

    The yellow curve is the expected black body IR radiation. The red part is the actual emission, the difference being due to absorption by water, CO2, CH4 and O3, mainly. It is a logarithmic scale, showing that emission curve extends from about 3 micron to 60 micron in wavelength.


    Last edited by exchemist; July 15th, 2022 at 07:41 AM.
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    On graphs that go from 1 micron to 70 micron, yeah. It looks pretty wide. If the graph had a wider range of values, it would look like a spike.

    We're just arguing aesthetics at this point. We clearly understand each other.
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  19. #18  
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    Quote Originally Posted by The Raven View Post
    On graphs that go from 1 micron to 70 micron, yeah. It looks pretty wide. If the graph had a wider range of values, it would look like a spike.

    We're just arguing aesthetics at this point. We clearly understand each other.
    The range involved comprises a bit more than the whole of what the ISO standard considers the mid-IR region of the EM spectrum, 3 - 50μ. No spectroscopist would think of a region this large this as just a peak.
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    The graph is quite instructive as it illustrates that a significant amount of energy is indeed absorbed by CO2.

    Although, I wonder how it can get worse. Almost all the energy in the exitation range of CO2 is already absorbed. It does not seem like more energy will be absorbed if the CO2 level increases further.��

    So, I thought that the goal of all anti-carbon actions was to stabilize the amount of CO2 in the atmospher. Is it in fact to reduce it? To which amount?
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    Quote Originally Posted by Ouray View Post
    The graph is quite instructive as it illustrates that a significant amount of energy is indeed absorbed by CO2.

    Although, I wonder how it can get worse. Almost all the energy in the exitation range of CO2 is already absorbed. It does not seem like more energy will be absorbed if the CO2 level increases further.��

    So, I thought that the goal of all anti-carbon actions was to stabilize the amount of CO2 in the atmospher. Is it in fact to reduce it? To which amount?
    That is a misunderstanding; higher CO2 levels mean the IR going spacewards is absorbed lower in the atmosphere - almost the basic definition of enhanced greenhouse effect. It doesn't "saturate" and start letting the excess pass through.

    Whilst stopping CO2 levels from rising ever higher (stabilising) is a primary goal of most serious emissions reductions policies (build an abundance of clean energy to replace fossil fuel burning) there is good reason to believe the ability to reduce CO2 levels would be very useful. Some of the scenarios for stabilising CO2 levels include that, overly optimistically I think. Our ability to do that is very limited so it won't be a matter of choosing an ideal target level and reaching it but of assessing how much reduction we can afford, which will be far short of reaching any ideal level.

    We make more CO2 than all other waste combined, more than any commodities we make apart from ones like sand and gravel that we don't really make; any CO2 removal industry will cost money without having any intrinsic way to be profitable. It has to be subsidised, by levies on fossil fuels or on taxpayers. Stopping doing it won't be a problem when doing it at all (at scales that count) is so difficult.
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  22. #21  
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    Quote Originally Posted by Ouray View Post
    The graph is quite instructive as it illustrates that a significant amount of energy is indeed absorbed by CO2.

    Although, I wonder how it can get worse. Almost all the energy in the exitation range of CO2 is already absorbed. It does not seem like more energy will be absorbed if the CO2 level increases further.��

    So, I thought that the goal of all anti-carbon actions was to stabilize the amount of CO2 in the atmospher. Is it in fact to reduce it? To which amount?
    In fact, if the graph were really accurate it would show a bit of emission at the wavelengths at which CO2 absorbs. What CO2 does is absorb and then re-radiate in random directions, instead of straight up to space as the Earth's surface does. That has the effect of slowing down the rate at which the IR radiation at these wavelengths leaves the atmosphere, thus heating it up.

    The more CO2 you have, the longer the path length for the radiation, due to repeated absorption and re-emission, before it can finally reach the top of the atmosphere and escape. So more heating.
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    Ok, thanks for the detailed answers.
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    unburnt gas causes more damage to the atmosphere then burnt gas so that might be it
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    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by The Raven View Post
    On graphs that go from 1 micron to 70 micron, yeah. It looks pretty wide. If the graph had a wider range of values, it would look like a spike.

    We're just arguing aesthetics at this point. We clearly understand each other.
    The range involved comprises a bit more than the whole of what the ISO standard considers the mid-IR region of the EM spectrum, 3 - 50μ. No spectroscopist would think of a region this large this as just a peak.
    Compared to the range that black bodies cover, it's nothing.

    As you can see here, the emission spectrum of the Sun only overlaps slightly with that of Earth. Mostly not overlapping. But there are stars out there much hotter than our Sun.




    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by Ouray View Post
    The graph is quite instructive as it illustrates that a significant amount of energy is indeed absorbed by CO2.

    Although, I wonder how it can get worse. Almost all the energy in the exitation range of CO2 is already absorbed. It does not seem like more energy will be absorbed if the CO2 level increases further.��

    So, I thought that the goal of all anti-carbon actions was to stabilize the amount of CO2 in the atmospher. Is it in fact to reduce it? To which amount?
    In fact, if the graph were really accurate it would show a bit of emission at the wavelengths at which CO2 absorbs. What CO2 does is absorb and then re-radiate in random directions, instead of straight up to space as the Earth's surface does. That has the effect of slowing down the rate at which the IR radiation at these wavelengths leaves the atmosphere, thus heating it up.

    The more CO2 you have, the longer the path length for the radiation, due to repeated absorption and re-emission, before it can finally reach the top of the atmosphere and escape. So more heating.

    That kind of explains why a small amount can matter, too. For any given beam of IR light traveling in a straight line, in any given direction, the probability of it encountering a CO2 molecule and being absorbed by it depends on how far it has to go, and what % of the atmosphere is CO2. If the distance is large, even a low concentration of CO2 can yield a nearly 100% probability of hitting one. And each one it hits will reemit it in a random direction, meaning it has a slightly lower than 50/50 probability of reemitting it back in the direction of the surface, instead of outer space.

    That means the relationship between quantity of CO2 and warming from CO2 is not 1 to 1. It can be worse than 1 to 1 as we approach a certain critical level (the point where nearly 100% is getting absorbed and reemitted). Then it would peak, and stop increasing. (Because at 100% absorb/reemit rate each photon has slightly less than 50/50 odds of getting out, and that's as bad as it gets.) Will the Earth still be livable at that point? I don't know. I think Venus is well past that point.
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    So if I understand correctly now, the problem is determining how much CO2 does it take before a beam of IR emitted from the surface has a nearly 100% probability of being absorbed by a CO2 molecule on its way to space?

    If 0.04% is enough to have a noticeable probability of that then yeah I guess we're screwed. If we look at every meter it passes through as a separate roll of the dice, then even a very small probability can become a large probability cumulatively. It's like playing Russian Roulette a lot of times. Play it once and your odds of dying are about 16.6%. Play it ten times and your odds of NOT dying are 16.1%
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    Quote Originally Posted by Ouray View Post
    The graph is quite instructive as it illustrates that a significant amount of energy is indeed absorbed by CO2.

    Although, I wonder how it can get worse. Almost all the energy in the exitation range of CO2 is already absorbed. It does not seem like more energy will be absorbed if the CO2 level increases further.��

    So, I thought that the goal of all anti-carbon actions was to stabilize the amount of CO2 in the atmospher. Is it in fact to reduce it? To which amount?

    I'm curious about this too. I wonder if the CO2 encounter rate is actually noticeably higher at 0.04% than at 0.02%?

    I don't know the odds of any given photon making it out into space for either percentage.

    That is a really good question to ask! Way to sum it up!

    If the odds of escape are the same or near the same, then the rate of escape should also be near the same, but if the odds of escape are dramatically different then the rate of escape would also be dramatically different.

    The values are different, but in principle its like the difference between playing Russian Roulette 100 times with a 6 cylinder revolver vs a 12 cylinder revolver. The odds of chambering a bullet and the number of pulls can lead to dynamic, sometimes even counter intuitive differences in the likelihood of surviving to the end of the gauntlet. It is still highly predictable, but I wouldn't try to solve for an outcome without a calculator.
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  28. #27  
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    Quote Originally Posted by The Raven View Post
    Quote Originally Posted by Ouray View Post
    The graph is quite instructive as it illustrates that a significant amount of energy is indeed absorbed by CO2.

    Although, I wonder how it can get worse. Almost all the energy in the exitation range of CO2 is already absorbed. It does not seem like more energy will be absorbed if the CO2 level increases further.��

    So, I thought that the goal of all anti-carbon actions was to stabilize the amount of CO2 in the atmospher. Is it in fact to reduce it? To which amount?

    I'm curious about this too. I wonder if the CO2 encounter rate is actually noticeably higher at 0.04% than at 0.02%?

    I don't know the odds of any given photon making it out into space for either percentage.

    That is a really good question to ask! Way to sum it up!

    If the odds of escape are the same or near the same, then the rate of escape should also be near the same, but if the odds of escape are dramatically different then the rate of escape would also be dramatically different.

    The values are different, but in principle its like the difference between playing Russian Roulette 100 times with a 6 cylinder revolver vs a 12 cylinder revolver. The odds of chambering a bullet and the number of pulls can lead to dynamic, sometimes even counter intuitive differences in the likelihood of surviving to the end of the gauntlet. It is still highly predictable, but I wouldn't try to solve for an outcome without a calculator.
    The question has already been answered to the satisfaction of the questioner. What part of the answer do you not understand, or do you consider incomplete?
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    How wonderful to return here after so many years to find a potentially charged subject calmly,clearly and politely discussed. Plus I learned a lot of science. Thanks all
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  30. #29  
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    Quote Originally Posted by Guitarist View Post
    How wonderful to return here after so many years to find a potentially charged subject calmly,clearly and politely discussed. Plus I learned a lot of science. Thanks all
    Blimey! A blast from the past. Good to see you are still alive!
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