# How do we know that C02 is a greenhouse gas? **URL:** \ **Category:** Great Debates\ **Created:** [February 27, 2010, 3:01am UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602 "2010-02-27T03:01:44Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 28, 2010, 9:02pm UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/41 "2010-02-28T21:02:14Z")
I didn’t realize that there was _any_ dispute that “before this century is over billions of us will die”. But that doesn’t have anything to do with climate change. ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [February 28, 2010, 9:20pm UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/42 "2010-02-28T21:20:05Z")
> [@Chronos](#): > > I didn’t realize that there was _any_ dispute that “before this century is over billions of us will die”. But that doesn’t have anything to do with climate change. Sorry about that, I guess I should had linked directly. In the post to Deltoid there was the link from James Lovelock reporting how climate change will be the reason for billions dying, he reports that the temperature will rise 8 degrees centigrade in temperate regions and 5 degrees in the tropics. Really alarmist stuff that is not well supported. [http://www.independent.co.uk/opinion/commentators/james-lovelock-the-earth-is-about-to-catch-a-morbid-fever-that-may-last-as-long-as-100000-years-523161.html](http://www.independent.co.uk/opinion/commentators/james-lovelock-the-earth-is-about-to-catch-a-morbid-fever-that-may-last-as-long-as-100000-years-523161.html) ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [March 1, 2010, 1:24am UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/43 "2010-03-01T01:24:15Z")
Moving to GD from GQ. Colibri General Questions Moderator ---
**Author:** ![Chief\_Pedant](https://avatars.discourse-cdn.com/v4/letter/c/a6a055/32.png) [@Chief\_Pedant](https://boards.straightdope.com/u/Chief_Pedant)\ **Post date:** [March 1, 2010, 3:54am UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/44 "2010-03-01T03:54:05Z")
> [@septimus](#): > > I’ll admit perhaps to “snarking” but I _did_ read the Lindzen column. I was just pointing out that your back-to-back posts seemed to exhibit a double standard. I do see why you preferred to cite the WSJ piece: Lindzen’s language there would never pass peer review. You still missed the point. GIGObuster criticized the WSJ post as “opinion” and offered “opinion” as counter-cites. That is why I made the comment I did. Lindzen’s piece was for the lay press and not intended to “pass peer review.” He has published papers which did pass peer review and he is a legitimate scientist, so to speak. The point I was making was that there is opinion out there among scientists that the science of AGW, with particular reference to the ability of current models to make accurate predictions, is not settled. I realize this is a minority opinion on this board, and in general am not inclined to try and change that opinion through this particular medium of a tedious one on one tit for tat exchange. I’d have a better chance of converting a devout Mormon to Islam, I suspect. To your question about habitat destruction: I’ve posted elsewhere that unless we control the human population, worrying about habitat destruction from AGW is like worrying about the ocean eroding the cliff at the base of your house while it’s on fire. The fire is over-population, already way out of control. We could eliminate further warming tomorrow and we’ll still overrun the earth with current population projections… ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 1, 2010, 4:02am UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/45 "2010-03-01T04:02:26Z")
> [@](#): > > The point I was making was that there is opinion out there among scientists that the science of AGW, with particular reference to the ability of current models to make accurate predictions, is not settled. Actually, the point you made was that there is that opinion out there among one scientist, not scientists plural. The reason Lindzen comes up so often in these discussions is because it’s really hard to find any other scientists who agree with him. And last I saw, the current population projections had population stabilizing at a number not all that much greater than what it is now. Yes, over-population is a problem, but it’s one we’re well on our way to solving. So let’s start solving some other problems, too. ---
**Author:** ![Kimstu](https://avatars.discourse-cdn.com/v4/letter/k/ecd19e/32.png) [@Kimstu](https://boards.straightdope.com/u/Kimstu)\ **Post date:** [March 1, 2010, 4:18am UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/46 "2010-03-01T04:18:24Z")
> [@Chief Pedant](#): > > The point I was making was that there is opinion out there among scientists that the science of AGW, with particular reference to the ability of current models to make accurate predictions, is not settled. I realize this is a minority opinion on this board, That depends on how you define “accurate” and “settled”. I don’t think there’s anybody on this board who would claim that the science about AGW has no serious uncertainties or that we can confidently pinpoint projected temperature rises even within a few degrees. However, the notion that because AGW science still has uncertainties we must remain totally “agnostic” about all its aspects, even about such basic questions as whether the AGW hypothesis is likely to prove valid, probably **is** a minority opinion on this board. It is certainly a minority opinion among the posters on this board who appear to be best informed about climate science. > [@Chief Pedant](#): > > and in general am not inclined to try and change that opinion through this particular medium of a tedious one on one tit for tat exchange. I’d have a better chance of converting a devout Mormon to Islam, I suspect. Probably. But that’s not so much because the people you’re arguing with are closed-minded as because your arguments are generally crap. ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [March 1, 2010, 4:33am UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/47 "2010-03-01T04:33:29Z")
> [@Chief\_Pedant](#): > > The point I was making was that there is opinion out there among scientists that the science of AGW, with particular reference to the ability of current models to make accurate predictions, is not settled. I realize this is a minority opinion on this board, and in general am not inclined to try and change that opinion through this particular medium of a tedious one on one tit for tat exchange. I’d have a better chance of converting a devout Mormon to Islam, I suspect. Oh, well, he is back to the Armchair Psychologist insults. I was not going to continue, but I see that this is now in Great Debates. BTW it is not just because of his posting in the WSJ that Lindzen is not considered a reliable source. [http://scienceblogs.com/deltoid/2006/06/lindzen\_in\_wsj.php](http://scienceblogs.com/deltoid/2006/06/lindzen_in_wsj.php) > [@](#): > > Judd Legum has already debunked Richard Lindzen’s repetition of Benny Peiser’s discredited study, but I want to add one point. Lindzen wrote: > > > [@](#): > > > > ``` > > More recently, a study in the journal Science by the social scientist Nancy Oreskes claimed that a search of the ISI Web of Knowledge Database for the years 1993 to 2003 under the key words "global climate change" produced 928 articles, all of whose abstracts supported what she referred to as the consensus view. A British social scientist, Benny Peiser, checked her procedure and found that only 913 of the 928 articles had abstracts at all, and that only 13 of the remaining 913 explicitly endorsed the so-called consensus view. Several actually opposed it. > > > > ``` > > Note that he got her name wrong (it’s Naomi), what she said she’d found (which was that 75% implicitly or explicitly accept the consensus) and what the corresponding claim by Peiser was (that only one third of the papers accepted the consensus). It seems likely that he never checked what Oreskes actually wrote and relied on a second or third hand account. > > Lindzen also writes: > > > [@](#): > > > > ``` > > A clearer claim as to what debate has ended is provided by the environmental journalist Gregg Easterbrook. He concludes that the scientific community now agrees that significant warming is occurring, and that there is clear evidence of human influences on the climate system. This is still a most peculiar claim. > > > > ``` > > Lindzen concedes that warming is occurring, but on the question of human influences argues that there has been a “clear attempt to establish truth not by scientific methods but by perpetual repetition”. > > One of the examples of this repetition that Lindzen gives is the 2001 NAS panel report which unequivocally stated: > > > [@](#): > > > > ``` > > Greenhouse gases are accumulating in Earth's atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise. Temperatures are, in fact, rising. > > > > ``` > > Lindzen does not mention that he was one of the authors of this report. He says one thing in a scientific report and another thing in an op-ed. > > Lindzen continues: > > > [@](#): > > > > ``` > > Even more recently, the Climate Change Science Program, the Bush administration's coordinating agency for global-warming research, declared it had found "clear evidence of human influences on the climate system." This, for Mr. Easterbrook, meant: "Case closed." What exactly was this evidence? The models imply that greenhouse warming should impact atmospheric temperatures more than surface temperatures, and yet satellite data showed no warming in the atmosphere since 1979. The report showed that selective corrections to the atmospheric data could lead to some warming, thus reducing the conflict between observations and models descriptions of what greenhouse warming should look like. That, to me, means the case is still very much open. > > > > ``` > > The report absolutely does not say that satellite data shows no warming since 1979. It states: > > > [@](#): > > > > ``` > > For observations during the satellite era (1979 onwards), the most recent versions of all available data sets show that both the low and mid troposphere have warmed. > > > > ``` As for your continuous insults, it is better to deal with them here: > **[Stop being an Armchair Psychologist Chief Pedant.](https://boards.straightdope.com/sdmb/showthread.php?t=554105)** > > http://boards.straightdope.com/sdmb/showthread.php?t=553874 Regarding Posts 33, 36 and now 44 \[QUOTE=Chief Pedant\] The link referenced has to do with how an author’s reaction to criticism unfolded. It was not characterized by me as “evidence” of... ---
**Author:** ![SteveG1](https://avatars.discourse-cdn.com/v4/letter/s/bb73d2/32.png) [@SteveG1](https://boards.straightdope.com/u/SteveG1)\ **Post date:** [March 1, 2010, 6:32am UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/48 "2010-03-01T06:32:20Z")
> [@Exapno\_Mapcase](#): > > Don’t listen to them! They’re all liars, under the pay of Big Nitrogen! There’s never been a study of CO2. There never will be. You know why? It doesn’t exist! The glaciers are just hiding waiting to pounce! You’ll see. You’ll all be sorry when you’re sitting under a mile of ice in your skivvies! At least my beer will stay cold 😃 ---
**Author:** ![toofs](https://avatars.discourse-cdn.com/v4/letter/t/4491bb/32.png) [@toofs](https://boards.straightdope.com/u/toofs)\ **Post date:** [March 1, 2010, 7:05am UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/49 "2010-03-01T07:05:28Z")
> [@Chief\_Pedant](#): > > To your question about habitat destruction: I’ve posted elsewhere that unless we control the human population, worrying about habitat destruction from AGW is like worrying about the ocean eroding the cliff at the base of your house while it’s on fire. The fire is over-population, already way out of control. We could eliminate further warming tomorrow and we’ll still overrun the earth with current population projections… Too many billions of humans consuming, consuming, consuming. Yet we continue to create even more humans, all of whom will create as many humans as they can support. So many of our problems begin with our massive population. Too bad religion interferes with an honest discussion of the need to control our unchecked reproduction. ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [March 1, 2010, 1:51pm UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/50 "2010-03-01T13:51:58Z")
> [@toofs](#): > > Too many billions of humans consuming, consuming, consuming. Yet we continue to create even more humans, all of whom will create as many humans as they can support. > > So many of our problems begin with our massive population. Too bad religion interferes with an honest discussion of the need to control our unchecked reproduction. Of course this attention to overpopulation is a valid one, the only problem is that, as seen in this discussion, this point is used in an effort to discredit the push to control greenhouse gases. Environmentalists already report that overpopulation also has to be taken into account, that does not magically prevent them from pointing that we should still do something about AGW. [http://www.sierraclub.org/population/factsheets/pop\_and\_globalwarming.asp](http://www.sierraclub.org/population/factsheets/pop_and_globalwarming.asp) ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [March 2, 2010, 4:13am UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/51 "2010-03-02T04:13:30Z")
> [@Chief\_Pedant](#): > > For a nice little example, follow the story of the rebuttal of David Douglass’s 2007 paper questioning the validity of the IPCC global climate models and their relationship to observed results. > > Douglass’s take on how the criticism unfolded [here](http://www.americanthinker.com/2009/12/climate_conspiracy_appendix_b.html) makes for a wry read. Since you bring up the Douglass paper, let’s discuss a little bit of the science behind it. What the Douglass paper purported to show is that the observed structure with height of the warming in the tropics was incompatible with model predictions. They did this by comparing the warming that had occurred with the standard error of the prediction made by many different models (some with multiple runs). [The “standard error” is essentially the standard deviation divided by the square root of number of model runs.] To understand how boneheaded a mistake this is, it is useful to consider another experiment. Suppose, I toss a single die. Now suppose that I want to simulate this using a computer model. Since it is easy to do, I could very quickly run the simulation about 1 million times and determine that the mean value I got on tossing the die is something like 3.5000 +/- 0.0001 where the quoted uncertainty is the “standard error” in the mean. Using Douglass et al.'s logic, I would then conclude with essentially complete certainty that my model is incompatible with my experiment (because we all know very well that the die will come up with one of the integer values between 1 and 6 and any of these values are so far outside the quoted “uncertainty” range as to be astronomically improbable). Of course, in Douglass et al., the number of model runs was not as dramatic…and there wasn’t this integer quantization that happens with dies that makes the absurdity of using the standard error like this quite so obvious. But, the basic problem is the same. (If you think that this problem only occurs when the average value doesn’t correspond to a possible value for an individual experiment, you can make the experiment be the tossing of two dies, in which case the mean value is to roll a 7. And, in fact, a 7 is the most likely value on a roll of two dies, but you will still get something else ~83.33% of the time.) If I was in Douglass’s shoes…and had his determination to apparently not admit a mistake, I suppose I too might be trying to distract attention from the fact that my paper was an utter piece of crap by focusing instead on the private e-mails of scientists who were interested in publishing something to point out its obvious flaws. ---
**Author:** ![blouis79](https://avatars.discourse-cdn.com/v4/letter/b/f14d63/32.png) [@blouis79](https://boards.straightdope.com/u/blouis79)\ **Post date:** [November 11, 2011, 9:43pm UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/52 "2011-11-11T21:43:35Z")
> [@figure9](#): > > Everyone knows that carbon dioxide absorbs infra red radiation and warms our planet. But how do we know? Has anyone ever done an experiment that shows CO2 absorbing infra red? It looks like a scientific magic trick. Hanging around with climate scientists has not revealed _ANY_ experiments since tyndall. I have read the full copies of tyndall’s original papers to see what he did. Tim Casey got me started: [http://tyndall1861.geologist-1011.mobi/](http://tyndall1861.geologist-1011.mobi/) Tyndall’s papers here: [Contributions to molecular physics in the domain of radiant heat : Tyndall, John, 1820-1893 : Free Download, Borrow, and Streaming : Internet Archive](http://www.archive.org/details/contributionsto03tyndgoog) As explained by Casey, Tyndall measured “failure of transmission”. Tyndall did not measure absorption or heating of the gas. The disposition of the energy “absorbed” was not elucidated. Some could be retained as heat, some will be reemitted in random directions. The relative contributions of these have not been demonstrated in any experiment I can find or that anyone I have asked can point me to. I have gotten as far as figuring that about 3.4m thick of 100% CO2 is about the same amount as exists in the atmosphere from ground to top of troposphere. So an experiment could be done in a column of CO2 in the sun - eg a 3.4m length of plumbing pipe with a blackbody surface closing the bottom and a polyethylene membrane (IR transparent) at the top. It is only a matter of time until someone with equipment to measure small temperature changes does an experiment like this… ---
**Author:** ![Attack\_from\_the\_3rd\_dimension](https://avatars.discourse-cdn.com/v4/letter/a/b38774/32.png) [@Attack\_from\_the\_3rd\_dimension](https://boards.straightdope.com/u/Attack_from_the_3rd_dimension)\ **Post date:** [November 11, 2011, 10:38pm UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/53 "2011-11-11T22:38:35Z")
I’m trying to recall if I’ve seen Chief Pedant in the pit yet. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [November 11, 2011, 11:15pm UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/54 "2011-11-11T23:15:38Z")
Okay, I’ve got a genuine question (translation: bona fide ignorance here) about CO[sub]2[/sub] as a green house gas, that I’ve not seen even mentioned let alone discussed above in this thread nor anywhere else that I recall. (Maybe this doesn’t belong in this thread, which appears to be a debate-about-the-debate rather than a discussion of greenhouse gas facts.) Just how much CO[sub]2[/sub] does it take to have a significant greenhouse effect, and why? By all accounts I’ve ever seen, the air is about 78% N and 21% O, and just 1% everything else, and CO[sub]2[/sub] is just a small fraction of even that last 1%. Now, speaking as a chemistry near-ignoramus, it just seems highly non-intuitive to me that such a small concentration of CO[sub]2[/sub] would have so much effect. Can somebody explain this? ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [November 11, 2011, 11:46pm UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/55 "2011-11-11T23:46:28Z")
First, this is a zombie thread. > [@blouis79](#): > > It looks like a scientific magic trick. > > Hanging around with climate scientists has not revealed _ANY_ experiments since tyndall. I have read the full copies of tyndall’s original papers to see what he did. > > Tim Casey got me started: [http://tyndall1861.geologist-1011.mobi/](http://tyndall1861.geologist-1011.mobi/) > Tyndall’s papers here: [Contributions to molecular physics in the domain of radiant heat : Tyndall, John, 1820-1893 : Free Download, Borrow, and Streaming : Internet Archive](http://www.archive.org/details/contributionsto03tyndgoog) > > As explained by Casey, Tyndall measured “failure of transmission”. Tyndall did not measure absorption or heating of the gas. The disposition of the energy “absorbed” was not elucidated. Some could be retained as heat, some will be reemitted in random directions. The relative contributions of these have not been demonstrated in any experiment I can find or that anyone I have asked can point me to. > > I have gotten as far as figuring that about 3.4m thick of 100% CO2 is about the same amount as exists in the atmosphere from ground to top of troposphere. So an experiment could be done in a column of CO2 in the sun - eg a 3.4m length of plumbing pipe with a blackbody surface closing the bottom and a polyethylene membrane (IR transparent) at the top. > > It is only a matter of time until someone with equipment to measure small temperature changes does an experiment like this… Second, this a zombie trick.. 🙂 The updated version of the experiment looking this time at the atmospheric layers was made by Plass in the old days of the 50’s. (Plass was looking for the background heat in the atmosphere to make better heat seeking missiles, this big piece of the AGW issue was found actually a serendipitous result of the cold war) [http://www.aip.org/history/climate/co2.htm](http://www.aip.org/history/climate/co2.htm) > [@](#): > > But would adding carbon dioxide in the upper layers of the air significantly change the surface temperature? Only detailed computations, point by point across the infrared spectrum and layer by layer down through the atmosphere, could answer that question. By 1956, such computations could be carried out thanks to the increasing power of digital computers. The physicist Gilbert N. Plass took up the challenge of calculating the transmission of radiation through the atmosphere (he too did it out of sheer curiosity, as a diversion from his regular work making calculations for weapon engineers). He nailed down the likelihood that adding more CO2 would increase the interference with infrared radiation. Going beyond this qualitative result, Plass calculated that doubling the level would bring a 3-4°C rise. Assuming that emissions would continue at the current (1950s) rate, he expected that human activity would raise the average global temperature “at the rate of 1.1 degree C per century.”(26) > > The computation, like Callendar’s, paid no attention to possible changes in water vapor and clouds, and overall was too crude to convince scientists. “It is almost certain,” one authority scolded, “that these figures will be subject to many strong revisions.”(27) Yet Plass had proved one central point: it was a mistake to dismiss the greenhouse effect with spectroscopic arguments. He warned that climate change could be “a serious problem to future generations” — although not for several centuries. Following the usual pattern, Plass was mainly interested in the way variations in CO2 might solve the mystery of the ice ages. “If at the end of this century the average temperature has continued to rise,” he wrote, then it would be “firmly established” that CO2 could cause climate change.(28) ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [November 11, 2011, 11:56pm UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/56 "2011-11-11T23:56:04Z")
> [@Senegoid](#): > > Just how much CO[sub]2[/sub] does it take to have a significant greenhouse effect, and why? > > By all accounts I’ve ever seen, the air is about 78% N and 21% O, and just 1% everything else, and CO[sub]2[/sub] is just a small fraction of even that last 1%. > > Now, speaking as a chemistry near-ignoramus, it just seems highly non-intuitive to me that such a small concentration of CO[sub]2[/sub] would have so much effect. Can somebody explain this? I’m sure you’ve seen those desktop toys where you have a globe or some other object suspended in air between two magnets. You might also be aware that if you take two regular magnets and try to accomplish the same thing, you’ll fail. The thing that you’re trying to levitate will always be pulled to the top or bottom magnet, instead of floating perfectly. The desktop toy has some gadgetry inside of it that rapidly changes the strength of the magnets to keep everything in alignment, even if there’s changes in air flow, an earthquake, or whatever else might happen to nudge the globe one direction. But so just think, in a closed off room, no particular air flow, a constant temperature, a fixed position, no Earthquake, if you tried to keep a globe centered between two magnets, you wouldn’t be able to do it no longer how you tried unless you had complex gadgetry to solve for changes too subtle for you to detect. To you, the 0.001 mph wind in your room is unnoticeable, but to the system which you are looking at, it’s an irrecoverable disaster unless you include equally imperceptible nudges to correct the issue. My point in all of this is that what seems big or small to you isn’t necessarily big or small. The planet we live on seems huge to you, and yet it’s infinitesimally tiny compared to the Sun, which is itself infinitesimally tiny compared to many other stars. Changing the temperature by a couple of degrees globally might seem like a massive change to you, but on a cosmic scale it’s barely noticeable. The thing being that life as we know it has evolved to fill a very narrow and fickle niche temperature gradient, so it’s significant to us and other lifeforms on the planet. ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [November 11, 2011, 11:56pm UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/57 "2011-11-11T23:56:17Z")
> [@Chronos](#): > > And last I saw, the current population projections had population stabilizing at a number not all that much greater than what it is now. Yes, over-population is a problem, but it’s one we’re well on our way to solving. So let’s start solving some other problems, too. What do those projections say is the cause for the slowdown in the rate of population growth? ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [November 12, 2011, 12:06am UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/58 "2011-11-12T00:06:19Z")
> [@Senegoid](#): > > Okay, I’ve got a genuine question (translation: bona fide ignorance here) about CO[sub]2[/sub] as a green house gas, that I’ve not seen even mentioned let alone discussed above in this thread nor anywhere else that I recall. (Maybe this doesn’t belong in this thread, which appears to be a debate-about-the-debate rather than a discussion of greenhouse gas facts.) > > Just how much CO[sub]2[/sub] does it take to have a significant greenhouse effect, and why? > > By all accounts I’ve ever seen, the air is about 78% N and 21% O, and just 1% everything else, and CO[sub]2[/sub] is just a small fraction of even that last 1%. > > Now, speaking as a chemistry near-ignoramus, it just seems highly non-intuitive to me that such a small concentration of CO[sub]2[/sub] would have so much effect. Can somebody explain this? > **[How do we know more CO2 is causing warming?](https://skepticalscience.com/empirical-evidence-for-co2-enhanced-greenhouse-effect-advanced.htm)** > > \An enhanced greenhouse effect from CO2 has been confirmed by multiple lines of empirical evidence. Satellite measurements of infrared spectra over the past 40 years observe less energy escaping to space at the wavelengths associated with CO2.... > [@](#): > > What the science says… > > The amount of warming caused by the anthropogenic increase in atmospheric CO2 may be one of the most misunderstood subjects in climate science. Many people think the anthropogenic warming can’t be quantified, many others think it must be an insignificant amount. However, climate scientists have indeed quantified the anthropogenic contribution to global warming using empirical observations and fundamental physical equations. > **[How substances in trace amounts can cause large effects](https://skepticalscience.com/CO2-trace-gas.htm)** > > Examines the science and arguments of global warming skepticism. Common objections like 'global warming is caused by the sun', 'temperature has changed naturally in the past' or 'other planets are warming too' are examined to see what the science... > [@](#): > > We know the amount of CO2 in the atmosphere has increased because we have measured it. We know the climate has warmed from current and historical data. The link between increasing greenhouse gases and increasing temperature is clear: just as ink makes water more colored, CO2 makes the atmosphere more absorbing. The extra CO2 in our atmosphere is trapping energy that would otherwise escape to space. The measured global warming matches closely with the amount of energy trapped from the greenhouse gases added to the atmosphere. > > A doubling of the trace molecule CO2 from 280 ppm to 560 ppm is still a trace, but just like with arsenic, the difference between a small trace and a larger trace is fatal. > **[How CO2 warming is driving climate](https://skepticalscience.com/co2-warming-35-percent.htm)** > > \The Nature commentary by Penner et al. on which this argument is based actually says that on top of the global warming caused by carbon dioxide, other short-lived pollutants (such as methane and black carbon) cause an additional warming... > [@](#): > > Although it is important to reduce the remaining climate uncertainties, such as the magnitude of the impacts of short-lived pollutants, it does not change the fact that CO2 is very likely the driving force behind the current global warming, or that if we double the amount of CO2 in the atmosphere from pre-industrial levels, the planet will likely warm in the range of 2 to 4.5°C. ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [November 12, 2011, 12:13am UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/59 "2011-11-12T00:13:50Z")
Darn it, missed the edit window, two posts up this was supposed to be there: Plass was looking for the background heat in different layers of the atmosphere to make better heat seeking missiles, the experiments made by Plass gave us a big piece of the AGW puzzle that was found serendipitously thanks to the cold war! ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 12, 2011, 8:06pm UTC](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602/60 "2011-11-12T20:06:23Z")
> [@](#): > > Quoth **blouis79** : > The disposition of the energy “absorbed” was not elucidated. Some could be retained as heat, some will be reemitted in random directions. What do you think “heat” is, anyway? You just said that some of the energy ends up as heat, while some of it ends up as heat. > [@](#): > > Quoth **Frylock** : > What do those projections say is the cause for the slowdown in the rate of population growth? As I understand it, it’s mostly due to industrialization of the Third World. Industrial countries have lower birthrates than undeveloped countries. Many first-world nations even have rates below the replacement level of 2.0. I’m not a sociologist, though. [Previous page](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602.md?page=2) [Next page](https://boards.straightdope.com/t/how-do-we-know-that-c02-is-a-greenhouse-gas/530602.md?page=4)