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Is the CO2 effect saturated?

What the science says...

Select a level... Basic Intermediate Advanced

The notion that the CO2 effect is 'saturated' is based on a misunderstanding of how the greenhouse effect works.

Climate Myth...

CO2 effect is saturated

"Each unit of CO2 you put into the atmosphere has less and less of a warming impact. Once the atmosphere reaches a saturation point, additional input of CO2 will not really have any major impact. It's like putting insulation in your attic. They give a recommended amount and after that you can stack the insulation up to the roof and it's going to have no impact." (Marc Morano, as quoted by Steve Eliot)

At-a-Glance

This myth relies on the use (or in fact misuse) of a particular word – 'saturated'. When someone comes in from a prolonged downpour, they may well exclaim that they are saturated. They cannot imagine being any wetter. That's casual usage, though.

In science, 'saturated' is a strictly-defined term. For example, in a saturated salt solution, no more salt will dissolve, period. But what's that got to do with heat transfer in Earth's atmosphere? Let's take a look.

Heat-trapping by CO2 in the atmosphere happens because it has the ability to absorb and pass on infra-red radiation – it is a 'greenhouse gas'. Infra-red is just one part of the electromagnetic spectrum, divided by physicists into a series of bands. From the low-frequency end of the spectrum upwards, the bands are as follows: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. Gamma rays thus have a very high-frequency. They are the highest-energy form of radiation.

As our understanding of the electromagnetic spectrum developed, it was realised that the radiation consists of particles called 'photons', travelling in waves. The term was coined in 1926 by the celebrated physicist Gilbert Lewis (1875-1946). A photon's energy is related to its wavelength. The shorter the wavelength, the higher the energy, so that the very high-energy gamma-rays have the shortest wavelength of the lot.

Sunshine consists mostly of ultraviolet, visible light and infra-red photons. Objects warmed by the sun then re-emit energy photons at infra-red wavelengths. Like other greenhouse gases, CO2 has the ability to absorb infra-red photons. But CO2 is unlike a mop, which has to be wrung out regularly in order for it to continue working. CO2 molecules do not get filled up with infra-red photons. Not only do they emit their own infra-red photons, but also they are constantly colliding with neighbouring molecules in the air. The constant collisions are important. Every time they happen, energy is shared out between the colliding molecules.

Through those emissions and collisions, CO2 molecules constantly warm their surroundings. This goes on all the time and at all levels in the atmosphere. You cannot say, “CO2 is saturated because the surface-emitted IR is rapidly absorbed”, because you need to take into account the whole atmosphere and its constant, ongoing energy-exchange processes. That means taking into account all absorption, all re-emission, all collisions, all heating and cooling and all eventual loss to space, at all levels.

If the amount of radiation lost to space is equal to the amount coming in from the Sun, Earth is said to be in energy balance. But if the strength of the greenhouse effect is increased, the amount of energy escaping falls behind the amount that is incoming. Earth is then said to be in an energy imbalance and the climate heats up. Double the CO2 concentration and you get a few degrees of warming: double it again and you get a few more and on and on it goes. There is no room for complacency here. By the time just one doubling has occurred, the planet would already be unrecognisable. The insulation analogy in the myth is misleading because it over-simplifies what happens in the atmosphere.

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!


Further details

This myth relies on the use of a word – saturated. When we think of saturated in everyday use, the term 'soggy' comes to mind. This is a good example of a word that has one meaning in common parlance but another very specific one when thinking about atmospheric physics. Other such words come to mind too. Absorb and emit are two good examples relevant to this topic and we’ll discuss how they relate to atmospheric processes below.

First things first. The effect of CO2 in the atmosphere is due to its influence on the transport of 'electromagnetic radiation' (EMR). EMR is energy that is moving as x-rays, ultraviolet (UV) light, visible light, infrared (IR) radiation and so on (fig. 1). Radiation is unusual in the sense that it contains energy but it is also always moving, at the speed of light, so it is also a form of transport. Radiation is also unusual in that it has properties of particles but also travels with the properties of waves, so we talk about its wavelength.

The particles making up radiation are known as photons. Each photon contains a specific amount of energy, and that is related to its wavelength. High energy photons have short wavelengths, and low energy photons have longer wavelengths. In climate, we are interested in two main radiation categories - firstly the visible light plus UV and minor IR that together make up sunshine, and secondly the IR from the earth-atmosphere system.

The Electromagnetic Spectrum

Fig. 1: diagram showing the full electromagnetic spectrum and its properties of the different bands. Image: CC BY-SA 3.0 from Wikimedia.

CO2 has the ability to absorb IR photons – it is a 'greenhouse gas'.So what does “absorb” mean, when talking about radiation? We are all familiar with using a sponge to mop up a water spill. The sponge will only absorb so much and will not absorb any more unless it's wrung out. In everyday language it may be described, without measurements, as 'saturated'. In this household example, 'absorb' basically means 'soak up' and 'saturated' simply means 'full to capacity'. Scientific terms are, in contrast, strictly defined.

Now let's look at the atmosphere. The greenhouse effect works like this: energy arrives from the sun in the form of visible light and ultraviolet radiation. A proportion reaches and warms Earth's surface. Earth then emits the energy in the form of photons of IR radiation.

Greenhouse gases in the atmosphere, such as CO2 molecules, absorb some of this IR radiation, then re-emit it in all directions - including back to Earth's surface. The CO2 molecule does not fill up with IR photons, running out of space for any more. Instead, the CO2 molecule absorbs the energy from the IR photon and the photon ceases to be. The CO2 molecule now contains more energy, but that is transient since the molecule emits its own IR photons. Not only that: it's constantly colliding with other molecules such as N2 and O2 in the surrounding air. In those collisions, that excess energy is shared with them. This energy-sharing causes the nearby air to heat up (fig. 2).

CO2 heat transfer

Fig. 2: The greenhouse effect in action, showing the interactions between molecules. The interactions happen at all levels of the atmosphere and are constantly ongoing. Graphic: jg.

The capacity for CO2 to absorb photons is almost limitless. The CO2 molecule can also receive energy from collisions with other molecules, and it can lose energy by emitting IR radiation. When a photon is emitted, we’re not bringing a photon out of storage - we are bringing energy out of storage and turning it into a photon, travelling away at the speed of light. So CO2 is constantly absorbing IR radiation, constantly emitting IR radiation and constantly sharing energy with the surrounding air molecules. To understand the role of CO2, we need to consider all these forms of energy storage and transport.

So, where does 'saturation' get used in climate change contrarianism? The most common way they try to frame things is to claim that IR emitted from the surface, in the wavelengths where CO2 absorbs, is all absorbed fairly close to the surface. Therefore, the story continues, adding more CO2 can’t make any more difference. This is inaccurate through omission, because either innocently or deliberately, it ignores the rest of the picture, where energy is constantly being exchanged with other molecules by collisions and CO2 is constantly emitting IR radiation. This means that there is always IR radiation being emitted upwards by CO2 at all levels in the atmosphere. It might not have originated from the surface, but IR radiation is still present in the wavelengths that CO2 absorbs and emits. When emitted in the upper atmosphere, it can and will be lost to space.

When you include all the energy transfers related to the CO2 absorption of IR radiation – the transfer to other molecules, the emission, and both the upward and downward energy fluxes at all altitudes - then we find that adding CO2 to our current atmosphere acts to inhibit the transfer of radiative energy throughout that atmosphere and, ultimately, into space. This will lead to additional warming until the amount of energy being lost to space matches what is being received. This is precisely what is happening.

The myth reproduced at the top – incorrectly stating an analogy with roof insulation in that each unit has less of an effect - is misleading. Doubling CO2 from 280 ppm to 560 ppm will cause a few degrees of warming. Doubling again (560 to 1130 ppm) will cause a similar amount of additional warming, and so on. Many doublings later there may be a point where adding more CO2 has little effect, but recent work has cast serious doubt on that (He et al. 2023). But we are a long, long way from reaching that point and in any case we do not want to go anywhere near it! One doubling will be serious enough.

Finally, directly observing the specific, global radiative forcing caused by well-mixed greenhouse gases has - to date - proven elusive. This is because of irregular, uncalibrated or limited areal measurements. But very recently, results have been published regarding the deep reinterrogation of years of data (2003-2021) from the Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua Satellite (Raghuraman et al. 2023). The work may well have finally cracked the long-standing issue of how to make finely detailed, consistent wavelength-specific measurements of outgoing long-wave radiation from Earth into space. As such, it has opened the way to direct monitoring of the radiative impact (i.e. forcing + feedback) of greenhouse gas concentration changes, thereby complimenting the Keeling Curve - the longstanding dataset of measured CO2 concentrations, down at the planet's surface.

Note: Several people in addition to John Mason were involved with updating this basic level rebuttal, namely Bob LoblawKen Rice and John Garrett (jg).

Last updated on 31 December 2023 by John Mason. View Archives

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Further reading

V. Ramanthan has written a comprehensive article Trace-Gas Greenhouse Effect and Global Warming.

Further viewing

Video by Rosh Salgado on his "All about Climate" YouTube channel in which he debunks Will Happer's claim that the CO2 effect is saturated in the atmosphere:

Comments

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Comments 676 to 698 out of 698:

  1. BothoStr

    I commend you for wading through the discussion from @587 onwards. I trust that you also reviewed the basic, intermediate, and advanced rebuttals, which are excellent. The comments contain a lot of great information along with some misinterpretation, misinformation, just plain wrong thinking, and quite a bit of misunderstanding about word choices. Being new, it takes serious study and critical thinking to sort it out, although it can become rather simple after some tough concepts are understood. I would be interested in which argument was most convincing to you. In addition to this discussion of “Is the CO2 Effect Saturated”, there is a closely related thread “The Beer Lambert Law and CO2 Concentration” that has more information.

    To your point, reasonable sounding claims often begin with a kernel of truth that are misinterpreted and become distorted. Despite all of the technical explanation and arguments, it seems that almost everyone accepts that the effect of increasing CO2 tends to be logarithmic rather than linear. This means that each additional 100 ppm in CO2 has less effect than the prior increments (e.g., 100 to 200 to 300 to 400 ppm, etc.). It also means that each doubling of concentration (e.g., 100 to 200 to 400 to 800 ppm, etc.) has the same effect. The subjective debate is about whether CO2 is on the steep part of a linear curve or on a plateau. After plotting it, I conclude that it is in the middle. The effect may be diminishing or saturating, but it is not saturated.

    This leads to another interesting observation. Where is methane, currently at 1.9 ppm, on its curve of effect? The answer is that it is on the steep part, and therein lies a reason for its strong power as a GHG.

    Response:

    [BL] Link added to the text to point to the thread "The Beer Lambert Law and CO2 Concentration".

  2. Charlie_Brown @676,
    The logarithmic relationship between CO2 and climate forcing is an empirical one and somewhere there is set out a ruling that it can be used for CO2 levels between (if I remember correctly) 150ppm up to 1,300ppm.

    A good reference for the CO2-Forcing relationship is Zhong & Haig (2013) which shows the wavelengths of the CO2 forcing up to 12,000ppm and in their Fig6b the total forcing up to levels above 100,000ppm. Note that a logarithmic relationship would appear as a straight line in Fig6b, and the CO2 forcing does climb above that 'straightness' for concentrations above 1,300ppm.

    You also mention CH4. At today's concentrations, the total forcing (from zero CH4) is something like 1Wm^-2. Note on that Fig6b, the forcing for CO2 with a similar concentration (I think it is 1,500ppb) is shown at something like 5.5Wm^-2. Like-for-like, CO2 is by far the more powerful GHG.

  3. BothoStr and everyone following this thread,

    Thanks to MA Rodger for providing the link to Zhong & Haig. I was not aware of this reference, but I suspect it has been made somewhere in this thread. I highly recommend it for everyone to read or re-read. It is an excellent high-level discussion of this topic. It is 6 pages of dense reading, but is a much better source for learning about the effect of CO2 than wading through hundreds of comments.

    MA Rodger
    I completely agree with your comments on the logarithmic relationships.

    For the power of CH4, I was referring to its Global Warm Potential which is often cited (at least in the U.S.) as being about 28-30. It is defined as the cumulative warming effect over 100 years for one ton of CH4 emission compared to one ton of CO2 emission at current concentrations of 1.9 ppm CH4 and 415 ppm CO2. On a molecular basis, there is a factor of 2.75 difference in like-for-like just due to the molecular weight. The rest of the GWP is due to the starting point of current concentrations, which puts CO2 on a shallower part of the forcing curve shown in Fig 6a. CH4 has a similar forcing curve, but to your point, the values are lower for CH4 than for the same concentrations of CO2.

  4. Searching for keywords in comments, I found that the Zhong & Haigh (2013) paper has been referenced several times in this thread, including in Jan 2019 @ 489, Sept 2019 @ 527, and others. I found excellent responses by MA Rodger and others to critiques about the paper by some who either didn’t understand the article or the physics, or just dismissed it with subjective superlatives. As I mentioned previously, it takes serious study to sort through the discussion. It helps to have a solid understanding of energy balances, fundamentals of radiant energy transfer, and basics of atmospheric physics.

    I also found several references to Univ of Chicago’s free, online version of MODTRAN Infrared Light in the Atmosphere. It is an excellent educational tool for self-study, and can be used to create the radiative forcing curves for CO2, as was done @609, and other GHGs (less rigorous than a line-by-line model using the HITRAN database, but still quite adequate for educational purposes). While learning about the greenhouse effect myself over the past few years, it was so helpful to me that I wanted to share it with my peer chemical engineers. To that end, I wrote an article for Chemical Engineering Progress, May 2022, “Introduction to an Atmospheric Radiation Model,” with Dr. David Archer (whose book is referenced in Zhong & Haigh) and Dr. Valerie Young as co-authors. It would be a good start for someone interested in learning-by-using the model. It offers background and step-by-step instructions for some example problems including the saturation effect. Unfortunately, Chemical Engineering Progress is not open access, but it might be found at the library or from a friend who is a member of the American Institute of Chemical Engineers.

  5. We all intuit that the more blankets you put on the bed, the warmer you'll be, so the article's argument has an intuitive appeal.  It has an embedded assumption, though, that the heat transfer up the atmosphere will stay constant.

    The physics is more complicated.  In the dense lower atmosphere, convection matters more and will change as temperature changes.  An excited CO2 molecule will lose its energy by bumping into an N2 or O2 molecule before it can radiate it away.  Around the tropopause there's a laser effect, in which CO2 radiation stimulates other CO2 molecules to emit their own radiation, so more CO2 means more radiation transfer.  A somewhat arduous calculation of the physics by van Wijngaarten and Happer can be found at arxiv.org/pdf/2006.03098.pdf.  They estimate doubling CO2 from 400 to 800 PPM would raise temperatures by 1.4C, in line with other published estimates.

    In other words, the article's original statement is a strawman.  Even a notorious climate denier like Will Happer agrees that there is a greenhouse effect, and more CO2 causes some warming.  So what exactly is being debunked?

    Moreover it's not clear what the SS authors believe to be the case instead.  If 1.4C isn't the right number, what is--5.0C?  Do you maintain there is no saturation effect at all, that the greenhouse response is linear, and we would see the same 5.0C going from 0 to 400 PPM, or 2000 to 2400?  That would seem to be implied by the article's physical argument.

  6. Gootmud @680... Did you miss my explanation of the greenhouse effect before?

  7. Rob @681, yes, your chart motivated me to read the paper that goes through the physics in detail.  

  8. Gootmud @680 ,

    The explanation of "Greenhouse" by Rob Honeycutt @681 is basic and straightforward, if you stop to think it through.   And yet a vast number of climate-science-deniers completely fail to understand the concept (most likely because they wish to stay in denial mode).

    You are right that the eminent Dr Happer (et Wijngaarden) has re-invented the wheel, and finds that all the climate scientists are correct about the climate sensitivity of atmospheric CO2 as being (roughly) 1.2 degC for CO2 change alone, without feedbacks.   Here, we definitely should trust the experts.

    Strangely, most of the denizens at WattsUpWithThat blog (and similar) are giving out the impression that Happer has shown them (the denialists) to be right and all the climate scientists to be wrong.   Very strange indeed.   Perhaps they (the denialists) are not actually reading/understanding Happer's confirmation of previously-known climate science  ~  I suspect they they are in sympathy with Happer's extremist wingnut politics (which he makes no effort to hide).

    Probably they are using wishful thinking, in that they use the faulty paradigm : 'Happer is an eminent scientist and he is "one of us wingnuts"  ~ and therefore the mainstream scientists must be wrong.'    [~ Which does not compute.]

    (B)  Gootmud , I must beg you to tell more about this idea you present about a CO2 laser effect at the tropopause level.  I have not heard of this before (unless it is something to do with a certain notorious Congresswoman who talks of Jewish Space Lasers ).

  9. Gootmud @680,

    Responding to the individual detail of your post not addressed so far:-

    ☻ The blanket analogy is not useful when the detailed mechanism of AGW is considered. The temperature of the air against the outer blanket will remain effectively constant when extra blankets are added. The emission-to-space altitude of the planet at the CO2 IR-emitting frequencies (and thus the temperature which dictates the level of emission-to-space) varies with the level of CO2 in the atmosphere. CO2 is well-mixed up to 50km and more.

    ☻ Convection is not a great player in cooling the planet. The atmospheric cells of the troposphere are responsible for the trade winds and if convection were significant, these would be premanently of super hurricane strength. It takes about two weeks for a packet of air to rise to the tropopause in these cells and potentially half the convection is seen in cyclones which are relatively rare events.

    ☻ Pretty-much all CO2 molecules excited by IR lose their excitation through collision. There are many many more CO2 molecules excited by collision and the level of IR-emission is thus determined by air temperature which sets the level of collision.

    ☻ Sympathetic emission from an excited CO2 molecule (your laser effect) occurs at all altitudes.

    ☻ The greenhouse effect from increased CO2 is not linear except when CO2 levels are very small. For higher levels, the relationship is rougly logarithmic. This the forcing resulting from CO2 levels increasing 200ppm to 400ppm would roughly equal that of 2,000ppm to 4,000ppm. There is actually a boost above that logarithmic relationship for high levels of CO2, beginning at ~1,500ppm, as an emissions frequency at around 10 microns begins to be significant. In this, you may find Zhong & Haig (2013) 'The Greenhouse Effect & Carbon Dioxide'  a useful read.

  10. Gootmud @ 680 - you said:

    An excited CO2 molecule will lose its energy by bumping into an N2 or O2 molecule before it can radiate it away. Around the tropopause there's a laser effect, in which CO2 radiation stimulates other CO2 molecules to emit their own radiation, so more CO2 means more radiation transfer.

    To expand on what MA Rodger says in comment 684, your first sentence is almost correct. Nearly all absorbed radiation energy will be lost thermally to surrounding molecules - but a very small proportion will be emitted as radiation again. As has been mentioned in previous comments here, there is a good description of the time constants involved at Eli Rabett's blog.

    Your second sentence is not so correct. Nearly all energy that is used to emit radiation in the atmosphere comes from the reverse of your first sentence: CO2 or other greenhouse gas molecules gain energy by collision with other molecules. Again, most of that will be lost by thermal collisions with other molecules, but a small amount will be emitted as radiation. As the temperature rises, more thermal energy is transferred by collisions, and more will be emitted as radiation.

    This dance between IR absorption, thermal collisions, and IR emission occurs at all levels in the atmosphere, not just the tropopause.. At each level, the exact quantities in each energy flow will depend on local temperature. You also get vertical energy transfer through convection. The overall temperature profile depends on a balance of all these energy flows.

    All this is incorporated into climate models. It is not news.

    The feedback question is important - distinguishing the "no feedbacks" response to doubling CO2 from the total response when proper feedbacks are included.

    I suggest you read a previous comment of mine in this thread for more information and links to two relevant papers from the 1960s. (Like I said: this is not news.)

  11. Also note that the van Wijngaarden and Happer paper has previously been discussed here, starting at comment # 587:

    https://skepticalscience.com/argument.php?p=24&t=676&&a=82#136341

  12. Gootmud... I'm curious where you get the idea anyone thinks the GHE is linear. The GHE is logarithmic. That's why sensitivity is expressed as degrees per doubling of concentration.

  13. Gootmud...  Reading through that Happer paper is interesting in that they're essentially confirming the consensus position on man-made climate change is correct. Their climate sensitivity figure of 1.4K is the direct effect without water vapor feedback. The 2.9K is with WV feedback per M&W1967, and the 2.2K figure is with updated calculations for WV. 

    So, why is that 2.2K figure so much lower than the central estimates of ~2.9K/2xCO2? Well, there are other feedbacks that are not included in Happer's calculations, like ice sheet feedbacks.

    This paper is a good demonstration that Happer knows the climte science is correct but he continues to speak out against it, ostensibly in order to instill doubt in the research.

    Why? If you up for a little light reading, try Oreskes/Conway's The Merchants of Doubt. (Hint: it's not really about the science.)

    It's also important to note, the warming we've seen over the past 60 years is largely in line with central estimates for climate sensitivity. We've increased CO2 by about 50% and we seem committed to around 1.5°C of warming. The numbers kind of work, unfortunately.

  14. Rob @687, as I said it's not clear to me what's in genuine dispute. To say the CO2 response is logarithmic means something is saturating, delivering less oomph with each additional unit. If you're saying it doesn't saturate, you're saying the response curve is not logarithmic but linear or concave, right?  If not, what does "no saturation" mean exactly?

  15. Gootmud @689 ,

    it would be helpful if you could state whether (or not) the English language is your mother tongue.  I mention that, because some of the faulty communication here may be simply a communication problem of the meanings of words (plus or minus their translated meanings).

    Example : the word "saturated" has a range of meanings in English ~ ranging from the colloquial (or even hyperbolical) through the standard formal and through to the technical and through to the scientific.   When we say "this garment is saturated" it means (formally) that the garment is so wet that it cannot get wetter.   But that is not the meaning of the term saturated in relation here to CO2 levels.

    The (roughly) logarithmic effect of rising CO2 means that there will be no actual halt to the warming effect of rising CO2 levels.  Which is why the "CO2 doublings" is the mathematical concept used in climate science.

    Science-deniers sometimes use "saturation" as an argument that more CO2 cannot have a harmful effect on Earth's climate ~ sometimes they do this out of ignorance, and sometimes they do this out of bad faith & a desire to deceive others (including deceiving themselves).   And I am sure that sort of misunderstanding occurs too in languages other than English.

  16. Gootmud @ 689:

    Think about what Eclectic says @ 690, and ask yourself "what does 'saturation' mean exactly". It's very hard to define "no saturation" unless "saturation" is defined first.

    ..but to try to answer your question, nearly any time someone comes up with the argument "CO2 is saturated", it is usually in the context of a claim that adding more CO2 to the pre-industrial levels will have no effect. That is, any IR absorption effect that exists for CO2 below 280-300ppm has already "saturated", so raising CO2 to 400, 500, or 600ppm wil not cause any warming. As you are discovering with  your reading, this simply is not true.

    It is often difficult to get climate contrarians to define what they mean by "saturation". A common "argument" is that any IR radiation emitted from the surface will be absorbed by CO2 close to the surface in the wavelengths that CO2 absorbs strongly. They will then argue that since none of this IR ecapes directly to space already, adding more CO2 doesn't affect this. This argument totally ignores the fact that CO2 will also emit IR radiation - so you still see IR radiation at greater heights (that did not originate at the surface) - and that what happens between the surface and the height where absorption reaches "effectively zero" still matters and will change as CO2 is added.

    This post on CO2 absorption and Beer's Law may help.

    Although there are a lot of comments on this thread, you might benefit from taking a few pages and looking at them to see what arguments are made, and explanations of what is wrong with them. You will find that new people come and go, making the same wrong arguments over, and over, and over (and over, and over)...

  17. Bob @691, I confess I haven't made it through the years of comments because I'm still stuck on the original article.  I'm not sure it's relevant that contrarians are often difficult to pin down, because the author got to choose which contrarian and which claim to rebut.  If it's not clear what that person meant by saturation or what its implications are, then that would seem to be a recipe for pages and pages of duplicative objections. Perhaps the article needs to be rewritten or retired?

    Are there are contrarians out there who claim additional CO2 will cause zero warming due to saturation?  I haven't run into them, and that's not quite what the Marc Morano quote says.  In fact all the contrarians named in this corner of the thread seem to be saying the same thing as y'all, that temperature response drops off logarithmically and the radiative impact of doubling CO2 from current levels is a degree or so of warming. 

    I'm trying to pin down what if anything is in dispute, because everyone seems to be in violent agreement at least on this saturation point.  

  18. Gootmud @ 692.

    Yes, there are many contrarians that deny that CO2 will have any effect, and "it's saturated" is a common argument. You need to take the Morano quote in the context of his decades-long history of trying to dismiss human-caused climate change as a hoax.

    Although the quote is a bit vague - not specifying at what level CO2 will saturate - that is the typical style of people like Morano. Leave enough in that is true, but then cascade into untruths or illogical "consequences".

    You can read more about Morano over at DesmogBlog. You will not find anything that indicates that he holds a position remotely related to the actual science.

    Where have you looked for people that say CO2 will not cause any warming because it's already saturated? As recently as comment 648 in this thread, we had someone making the claim. A little earlier in this thread, another person with another variant. And here. And there are still nearly 600 earlier comments I have not searched. Those links cover the past couple of years, and the comments started in 2009, so it's a small part of the collection.

    Any saturation point with respect to CO2 will be at such high concentrations (many times current concentrations) that any use of the argument in the context of projections for the next 50-100 years is completely bogus.

  19. Bob @693, saturation is an effect, not a point.  Again, if you think it's not happening but temperature response is still somehow logarithmic, one must ask what you mean by saturation?

  20. Gootmud @694 ,

    Exactly correct of you ~ "saturation" is a meaningless term.

    Meaningless, at least, in this climate context.

    The saturation argument is used by "fools and knaves".

    Gootmud, you have not yet answered whether you are a native speaker of English.  If you are not a native speaker, then I ought to explain the archaic phrase "fools and knaves".

    Fools and Knaves does exactly describe those people using the saturation argument against AGW.     ....And as this thread approaches 700 comments, perhaps we could amend the phrase, to read "fools and knaves and sealions".

  21. Gootmud:

    Don't play word games. It's the climate contrarians that make the claim that "the CO2 effect is saturated". You need to get the ones making that claim to explain what they mean.

    In years of watching this (I've been studying climatology since the late 1970s, specialized in the subject for my PhD, and taught it at university for a number of years, and for over a decade made my living measuring climatologically-important radiation fluxes), I have yet to find a climate contrarian who can define it in a way that actually presents a real description of radiative transfer processes.

    The people that make the claim pretty much always end up demonstrating a critical lack of understanding of how radiation transfer theory works. As you try to get them to define what they mean, it readily becomes apparent that they don't know what they are talking about.

    There are several variations in the contrarian "CO2 is saturated" meme, and each goes wrong in a slightly different way. The term is rarely seen in proper radiation transfer discussions of climate, because the very few ways in which it is a meaningful term are ones that are not an issue for earth's climate - past or future.

    The few climate contrarians that do understand radiation transfer theory do not make the "CO2 is saturated" claim - as you have discovered. They make other bad claims, but not the "CO2 is saturated" one.

  22. Gootmud... The "CO2 saturation" claim is a red herring used by climate deniers to try and instill doubt about the science. Don't get stuck on whether the claims are technically accurate. Fundamentally, people rejecting climate science are mostly politically or ideologically motivated and are using this topic as a cudgule to further their goals.

    The "saturation" of CO2 is a nuanced element of the science that is well understood and does not change the accepted position that human emissions of CO2 are precipitously warming the earth. I was offering the animated graphic I posted to help you understand why this is the case.

    You can't get around the basic fact that energy in = energy out, and when you add more greenhouse gases to the atmosphere the surface must warm. Functionally, the effect is occurring up higher in the atmosphere where CO2 is not saturated. When you add more CO2, the point where that occurs rises and, again, the surface sees a corresponding warming (per my graphic).

  23. Gootmud’s comment @680 and the responses have been informative and educational. Thank you Rob, Eclectic, MA Roger, and Bob. However, based on today’s reality, I think this Rebuttal should be updated.

    The potential magnitude of global warming due to a doubling of CO2, and the related denial tactic of claiming the CO2 effect is ‘saturated’ or not a significant concern, is now only an academic matter. It was an important matter for leaders to be aware of 30 years ago when it was vigorously argued against by ‘people with interests that were contrary to this improving understanding’. But since warming beyond 1.0 C has already occurred, and warming beyond 1.5 C is already likely due to a lack of responsible leadership action to limit the harm done, it is no longer a relevant leadership considerations.

    Note: Disappointing people who have developed undeserved perceptions of opportunity, prosperity, advancement or superiority based on harmful unsustainable activity and related beliefs ‘is not harmful’. Governing to limit harm done is essential to the advancement of civilization.

    The Story of the Week “1.5 and 2°C: A Journey Through the Temperature Target That Haunts the World” in the “2022 SkS Weekly Climate Change & Global Warming News Roundup #50” makes it clear that decades ago the following was understandable:

    • warming above 1.0 C risks significant harm (that is now proven by today’s reality).
    • warming beyond 2.0 C is very risky (hopefully that will never be proven in a near future reality).

    That understanding fits with the 1.5 C ‘long term maximum harmful impact objective’ paired with the need to limit the ‘temporary peak harmful impact level’ to significantly less than 2.0 C.

    The IPCC FAQ Chapter 1 provides additional information regarding the targets. An important bit of information is that 1.0 C warming was reached in 2017. When the formal global leadership agreement was established in 2015 human impacts were almost certain to exceed 1.0 C. And the significant costs of the failure to limit the peak human impacts to 1.0 C are also now harder to deny.

    The reality today is: No matter what someone wants to believe regarding the sensitivity of global average surface temperature to increasing CO2 the actual evidence makes that debate irrelevant. What is now undeniable by leadership is the need for the unprofitable safe removal of carbon from the atmosphere to bring the harmful impact level back down below 1.5C. And it is also undeniable that the people who benefited most from the harm done need to do the most to limit how much worse the problem is at the peak, pay to remove the excess carbon, and help everyone harmed by the impacts of what they benefited from.

    Leaders no longer need to be guided by the science of the potential rate of warming due to a doubling of CO2 levels. That type of pursuit of understanding is also ‘hopefully’ very unlikely to be relevant to the future of humanity. Responsible leadership would prevent that magnitude of harm done from ever becoming a reality.

  24. My arguement is not against global warming, but in falsely ascribing it to CO2.

    The NASA data on the absorption of earth's radiation show clearly that no energy is leaving the earth in the 14-16 micron band.  This is the only significant absorption band for CO2 absorbing our radiation.  Snce it is saturated/opaque, more CO2  has no effect.

    This causes the earth to warm up a bit to increase radiation in other wave lengths and balance out the loss in the 14-15micron range.  

    This very detailed Nasa data can now be found at NASA Technical Memorandum 103957, Appendix E.  All 90 pages of it.  It was produced in 1992, but was unavailable to the public till now.  However, it has been in use by theNASA  Infra-red astronomy project Gemini, for over 20 years, proving its validity.

    Previously the best data available was from the 1960's NASA  Nimbus satellite.  This utilized a very broad band sensor, seemingly like 20microns.  This obviously could not pick up a 2 micron minimum band and  gave a gently curved spectrum showing a maximum absorption of about 50%.  

    A full discussion can be seen in "Carbon Dioxide - Not Guilty" on kindle for 99c.

    My conclusion is the CO2 is not the cause of our global warming, and I have no idea as to what is the cause.  We are wasting our time and money on a false premise, and should rather find the real cause.

    Response:

    [BL] repetition of previous points made on other threads snipped.

    You have been down this road before, (here, and here) and you have been warned before.

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

     

  25. I reviewed your Basic Rebuttal to CO2 greenhouse effect saturation, and believe that the author's analogy with the buckets of water is incomplete and misleading.  If I understand this analogy, it is comparing the water with heat energy, the bucket with the atmosphere, and the hole in the bucket corresponds to a path for the heat energy to reach outer space. Finally, the plug for the hole corresponds to the CO2 greenhouse effect. CO2, however, can absorb (or block) IR radiation only within a narrow band at a 15 micron wavelength, which is a small fraction of the total IR energy going into space.  In order to complete the analogy, one would need to blow a massive hole in the other side of the bucket to allow for IR energy to escape at other wavelengths.

    Response:

    [BL] Should you wish to inform yourself (which seems highly unlikely), you should read more about the bucket analogy on this thread.

    You may also wish to acquaint yourself with the definition of "analogy". An analogy is not typically expected to be a full model of an entire system - just a simple way of explaining part of it:

    analogy

    A relationship of resemblance or equivalence between two situations, people, or objects, especially when used as a basis for explanation or extrapolation

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