Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.


Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup


All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Support

Twitter Facebook YouTube Pinterest MeWe

RSS Posts RSS Comments Email Subscribe

Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...

New? Register here
Forgot your password?

Latest Posts


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)

The mistaken idea that the Greenhouse Effect is 'saturated', that adding more CO2 will have virtually no effect, is based on a simple misunderstanding of how the Greenhouse Effect works.

The myth goes something like this:

  • CO2 absorbs nearly all the Infrared (heat) radiation leaving the Earth's surface that it can absorb. True!
  • Therefore adding more CO2 won't absorb much more IR radiation at the surface. True!
  • Therefore adding more CO2 can't cause more warming. FALSE!!!

Here's why; it ignores the very simplest arithmetic.

If the air is only absorbing heat from the surface then the air should just keep getting hotter and hotter. By now the Earth should be a cinder from all that absorbed heat. But not too surprisingly, it isn't! What are we missing?

The air doesn't just absorb heat, it also loses it as well! The atmosphere isn't just absorbing IR Radiation (heat) from the surface. It is also radiating IR Radiation (heat) to Space. If these two heat flows are in balance, the atmosphere doesn't warm or cool - it stays the same.

Lets think about a simple analogy:

We have a water tank. A pump is adding water to the tank at, perhaps, 100 litres per minute. And an outlet pipe is letting water drain out of the tank at 100 litres per minute. What is happening to the water level in the tank? It is remaining steady because the flows into and out of the tank are the same. In our analogy the pump adding water is the absorption of heat by the atmosphere; the water flowing from the outlet pipe is the heat being radiated out to space. And the volume of water inside the tank is the amount of heat in the atmosphere.

What might we do to increase the water level in the tank?

We might increase the speed of the pump that is adding water to the tank. That would raise the water level. But if the pump is already running at nearly its top speed, I can't add water any faster. That would fit the 'It's Saturated' claim: the pump can't run much faster just as the atmosphere can't absorb the Sun's heat any faster

But what if we restricted the outlet, so that it was harder for water to get out of the tank? The same amount of water is flowing in but less is flowing out. So the water level in the tank will rise. We can change the water level in our tank without changing how much water is flowing in, by changing how much water is flowing out.

water tank

Similarly we can change how much heat there is in the atmosphere by restricting how much heat leaves the atmosphere rather than by increasing how much is being absorbed by the atmosphere.

This is how the Greenhouse Effect works. The Greenhouse gases such as carbon dioxide and water vapour absorb most of the heat radiation leaving the Earth's surface. Then their concentration determines how much heat escapes from the top of the atmosphere to space. It is the change in what happens at the top of the atmosphere that matters, not what happens down here near the surface.

So how does changing the concentration of a Greenhouse gas change how much heat escapes from the upper atmosphere? As we climb higher in the atmosphere the air gets thinner. There is less of all gases, including the greenhouse gases. Eventually the air becomes thin enough that any heat radiated by the air can escape all the way to Space. How much heat escapes to space from this altitude then depends on how cold the air is at that height. The colder the air, the less heat it radiates.

(OK, I'm Australian so this image appeals to me)

So if we add more greenhouse gases the air needs to be thinner before heat radiation is able to escape to space. So this can only happen higher in the atmosphere. Where it is colder. So the amount of heat escaping is reduced.

By adding greenhouse gases, we force the radiation to space to come from higher, colder air, reducing the flow of radiation to space. And there is still a lot of scope for more greenhouse gases to push 'the action' higher and higher, into colder and colder air, restricting the rate of radiation to space even further.

The Greenhouse Effect isn't even remotely Saturated. Myth Busted!

Basic rebuttal written by dana1981

Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial


Last updated on 7 July 2015 by pattimer. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

Argument Feedback

Please use this form to let us know about suggested updates to this rebuttal.

Related Arguments

Further reading

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


Prev  1  2  3  4  5  6  7  8  9  10  11  12  13  Next

Comments 501 to 550 out of 609:

  1. Thanks all. Continues to be really informative, and I think I now have a good handle on the different possible ways in which increasing co2 could increase troposphere temperatures. What isn't so clear is how significant those effects are at marginal increases from 400 ppmv, but to br honest I could probsbly spend the next 6 months studying the topic in detail and not be that much more certain given the myriad complexities.

    MA: The Zhong and Haigh paper is really interesting, but I'm not quote following figures 5a and b, top row, which seem to show minimal change in radiative flux (when averaged across the spectrum) even up to 32x co2. I'm not convinced they have taken into account all those phenomena when working out thr logarithmic relationship - they say

    "our calculations assume no change in the surface or atmosphere, do not consider the climate response to the RF, or any issues related to climate sensitivity"

    But perhaps there's something intrinsic to the models that goes without saying. My point was more that it be *more* of a factor going forward, as the proportion of time when thr altitude of emission is in a scenario where increasing altitude does not mean decreasing temperatures is presumably increasing with increasing co2.

    Given the point has been made to me repeatedly that the science is apparently so settled no one's even really looking at it anymore, i thought it might be useful to go back and look at past predictions to see how they measure up against present day. This might not be the right page to discuss such matters, but I came across this analysis of a Hansen 1988 paper, in which apparently actual temperatures are matching up in line with his 'zero co2 increase after 2000' scenario Thoughts?

  2. @eclectic: it appears that is the case. the point wasn't about a single altitide; rather it's about where the altitude of emission is in an area where increasing altitude no longer leads to decreasing temperatures

  3. LTO @501 ,

    A/  Please note that you have duplicated your post #501as #502 and #503. Do not be too embarrassed ~ a Moderator will correct that reduplication.   Likewise with your other duplication !

    B/  On #504 [soon to be #502, I expect] , you will need to explain what you mean by your first and second sentences.   What is the case?   What is the misunderstood point?   There seems to be considerable confusion of communication here.

    Take a look at the atmospheric temperature versus altitude graphs.   For most of the troposphere, the temperature reduces with height.   Above that, the temperature holds steady for a short distance ~ and above that, temperature increases with altitude through the stratosphere.   You need to integrate that information with the decreasing air density ~ because both factors are important in comprehending the (15um) radiative loss to space.   The low density in stratosphere is the reason the tropospheric (15um) loss is vastly more important (and why the weighted average "emission height" is generally in the troposphere, affected by the lapse rate there).

    Things get more complex, if we consider other radiative output from CO2 ~ and also other radiative properties of H2O and all molecules of 3 or more atoms.   But for our mutual purposes, it is enough to consider the 15um band, here in this thread.

  4. LTO , you have mentioned the "realclimatescience" website.

    Perhaps you are not yet aware ~ but that is not a science website, it is a propaganda website.   "Fake News".   As a pointer, one should always be on the alert for disinformation, on any site prominently quoting Feynman, Popper, or Galileo.   [ Feynman, Popper and Galileo are of course very worthy gentlemen in their own right ~ but their philosophies are seriously abused by propagandists hoping to drape themselves with reflected glory . . . propagandists hoping to mislead the uninformed/unthinking reader. ]

    As to your question on Hansen etcetera ~ the propagandists are diverting your attention onto some old predictions/projections of 30+ years ago, in the early days of such assessments.   Worse by far, they are deceiving you by comparing to more recent high-altitude data, not the planetary surface temperatures.   That is classic bait-and-switch deception.

    Also, note that site's reference to "the 52% consensus" ~ based on some very unrigorous survey of members of some meteorological society.  No detailed explanation.   Quite shameless propaganda.

    LTO , please get your information from an honest scientific website.   For instance : RealClimate.  (You can see how the anti-science propagandists are trying to piggy-back, by using a similar sounding name such as realclimatescience, to mislead the careless into their own site.)

  5. Erp . . . I have committed an unfortunate ambiguity, in the second post above this one.   "the temperature reduces with height" should read "the temperature reduces with increased height" ~ which is much clearer !   My apologies for that initial statement, which might well pass in colloquial conversation, but which was very open to misinterpretation (in written form).

  6. LTO:

    A scientific discussion of Hansen's 1988 paper is here Realclimate discussion .  Note that this is the website the denier site "realclimatescience" is attempting to hijack. 

    Hansen's projections were skillful but the release of greenhouse gasses was not what he forecast. While he forecast lower CO2 emissions, he forecast higher cloroflurocarbon emissions.  Simplistic evaluations of only CO2, like the one at realclimatescience, ignore these important greenhouse gasses. 

    The writers at realclimatescience have had the opportunity to read the correct science at Realclimate and continue to push their incorrect ideas.  In my book that is a deliberate lie.  I recommend you stop wasting your time (and ours looking up the correct analysis) reading denier web sites.

    There is an easy way to find out how increasing CO2 affects temperature: read the IPCC summary and figure they are correct!!  It is a waste of time to attempt to calcualte or completely understand the atmosphere yourself, it is too complex. 

  7. LTO @501: "i thought it might be useful to go back and look at past predictions to see how they measure up against present day."

    You can easily do that right here on SkS. Scroll up to the "thermometer" in the left-side banner. Under that are some rectangular "buttons". Click on the "Lessons from Predictions" button. That will take you to a page listing blog posts dealing with past predictions/projections and how they have measured up.

  8. LTO @501,

    Concerning Zhong & Haigh (2013), you ask about the meaning of "our calculations assume no change in the surface or atmosphere, do not consider the climate response to the RF, or any issues related to climate sensitivity." This is simply saying that they calculate the climate forcing due to these changes in CO2 levels. Such forcings would increase global temperature and the resulting changes to other GHG levels, cloud, surface albedo, etc, which would result from that forcing are not being considered. This is solely about the direct effect of the CO2 and not any feedbacks.

    And the top row of their Fig 5a/b is simply the traces within all the other rows plotted together. The one rather confusing part of this Fig 5 is that Fig5a plots the zero CO2 alongside all the other CO2 levels while Fig5b plots the difference between each different level and a current level (as was) of 389ppm. Thus the second row of Fig5a shows both zero (lt blue) and 1.5ppm (green) but the difference between 389ppm & 1.5ppm (green) appears down in the fourth row of Fig5b.

    Note I still intend to tap out a screed as I promised @492.

  9. LTO - Responding to your earlier questions about energy exchange via collisions, and the relative energies of emitting GHGs and the rest of the atmosphere (sorry this is weeks later, just got back to this thread after a while):

    At sea level each molecule in the atmosphere collides with others at about 10^9 times per second. The time for an excited CO2 molecule to emit IR is about 10^-6 seconds. Therefore (comparing relative numbers) each CO2 molecule collides ~1000 times before emitting. Thus the CO2 molecules emit at a rate tied directly to the gas temperature. 

    The tropopause (where the break-even point of CO2 emission lies, ending convection) ranges from about 7 to 20 km, poles to equator. Air pressure at 15km is roughly 100mb, 1/10 sea level, meaning that at that altitude each CO2 molecule collides 100 times with other atmospheric molecules before emitting. So again, CO2 molecules emit at rates tied directly to atmospheric temperature. 

    One side point, since I've seen this a particular error occur repeatedly - emitting CO2 molecules are by no means tied to absorbing CO2 molecules, and neither are the absorption energies directly tied to emission energies on a photon by photon basis. The gases warm due to convection and IR absorption, that temperature gets shared, and the emissions from any particular gas volume are statistical expressions of the GHG emission spectra from GHGs at that temperature. There's no immediate one-to-one connection. 

  10. michael sweet @506, instructing readers to blindly accept the IPCC summary and not "waste" time trying to understand the atmosphere is not wise if you are trying to gain consensus. There is no scientific method that ends in "trust me". 

    I'm focused on mathematics and, to a lesser extent, the physics of the arguments and most of the posts on this science seem reasonable and well-intentioned. I've been studying the IPCC reports and find it difficult to opine without more research. This site is typically useful although I find the proponents of ACG less reasonable than the skeptics. 

    On the topic of CO2 saturation, the math is not necessarily flawed, but the assumptions are immense and I'm not at all comfortable with the magnitude of error analysis required to reach some of the conclusions. For example, identifying the factors that support a convective heating model with CO2 are statistically impossible. Anthropogenic CO2 is approximately 0.0012% of the atmosphere. But the anthropogenic concentration would have to be increasing dramatically to support the 400ppm if the natural portion were to be static. Of course, we know that the natural portion of the CO2 concentration has increased in recent decades as the planet has been greening. This is the first of many assumptions that do not have much scientific basis. We know the current concentration and its fluctuations through a 12-month cycle. We know natural CO2 has increased although we don't know entirely from where. We know anthropogenic concentrations have increased although we don't know how much is being contributed from each continent. We know that reflective heating has almost peaked. So the assumption is convection but we don't know how much of the convective heating is due to other molecules. So scientists guess at what might be happening and how much heat might be involved in different transfer models without knowing exactly which molecule is involved and to what degree each molecule is contributing to convection. Mathematically speaking we've already reached a level of uncertainty with only the points I've mentioned to make the entire convection from CO2 theory basically worthless. The error rates are exceeding 50% in some models. In any other field of study, such a large error rate would be considered a SWAG and not worthy of publishing. Since the climate argument has gone tribal, the science is not being mathematically supported as long as the conclusion is that the result supports the bias of the publisher. 

    That you would recommend we "trust" the IPCC summaries when the details have so many mathematical SWAGs is intellectually disingenuous. I will fully admit to not understanding the chemistry enough to know how much error is introduced with each atmospheric assumption (not to mention the ocean carbon sink assumptions), but I can say with some authority that the mathematics is not tight enough to support any engineering application. And since we're talking about taking trillions of dollars away from more present and tangible efforts such as disease, I think it is fair to question the outcome of these models that carry such broad ranges of uncertainty.

    Recent temperatures have not followed recent CO2 measurements. It appears that CO2 concentrations might be less convective than the IPCC asserts. And if that is the case, we're pretty much back to guessing on why there appears to be a temperature correlation with CO2 emissions in the first place. I don't think the public or the lawmakers realize how important this CO2 convection issue is to the broader argument of CO2 related climate change. 

    So, my response is, NO! Do not trust the IPCC summary on the topic of heat transfer related to atmospheric CO2 convection since the math is weak. Use the scientific method, question every assertion, and come up with a better explanation for the heat fluctuations in the atmosphere. If somebody doesn't understand the science, learn the science, don't ignore it.

    I would encourage the readers of this site to ignore any advice that suggests a conclusion should be assumed valid if even a single assumption is left untested.


    [PS] This is offtopic. This thread is about myth that adding more CO2 would not increase temperature. If you can do the maths, then Michael Sweet comment does not apply, but you would be better off delving into atmospheric physics text book for starter (eg this one). For a paper start with Ramanathan & Coakley 1978. The Radiative Transfer Equations are key to numerous technologies other than climate science (USAF is source of main database) and the maths has been checked against observation at top of atmosphere or from ground in numerous papers. A very direct observation can be found here. The full IPCC report is massively cross-referenced with the papers. If you dont like their summary of the research, read the papers. You certainly cannot discuss it sensibly with a comic-book view of what the science actually says. Do not discuss offtopic here - they will be deleted. Try Search or Arguments | by taxomony to find for relevant threads. CO2 is just a trace gas, human CO2 is tiny. I cannot understand your "convective" assertion at all.

  11. Jjworld, most of your post is off-topic. This thread is about the argument that additional CO2 is not going to have an effect, as quoted from Marc Morano at the top of the page. That argument is ignorant and worthless. For more detail, see the Real Climate threads named "A saturated gassy argument." I'm sure they are referenced here somewhere and they are easy to find with RC' search function. The additional effect is in the wings of the spectrum. The rest of your objections belong in other threads. I have seen skeptics arguing that CO2 could fall as carbonic snow in Antarctica, that waste heat was the real cause of warming or that MODTRAN was just a computer model without basis in reality so, to me, the idea that skeptics are more reasonable is laughable beyond description.

  12. Your post is full of very confusing pieces. The following need clarification

    "convective heating model with CO2." What exactly is that?

    'the anthropogenic concentration would have to be increasing dramatically to support the 400ppm if the natural portion were to be static." What does that mean? Anthropogenic contribution is approximately 100 times that of volcanic activity, it has increased immensely in the recent past, a blink of an eye in geological scales. What does natural mean? Geological, biological, both? Most living creatures are carbon neutral since they get their carbon, directly or indirectly, from the atmosphere. Plants that fix carbon are in fact carbon negative if they are not burned. You need to be more specific.

    'we know that the natural portion of the CO2 concentration has increased in recent decades as the planet has been greening." This does not follow. The greening suggest plant biomass increases in some regions, not increased contribution to atmospheric CO2 from natural sources.

    "Recent temperatures have not followed recent CO2 measurement." Actually, they have, with the normal wiggles of variability, the trend continues, in all datasets.

    "CO2 concentrations might be less convective than the IPCC asserts" Say what? This requires a detailed explanation, starting with the Trenberth schematic so you can explain where exactly the concentration of a radiatively active gas has convective properties. Perhaps you should tell everyone what you think is "convective."

    "heat transfer related to atmospheric CO2 convection." Once again, you need to clarify what that means. 

    You start your post by saying "the math is not necessarily flawed" and then concludes with "the math is weak." Which is it? What math are you refering to? Demonstrate how it is weak or provide references to peer-reviewed publications that do so. As it stands, you post is a gish gallop of confusing language without a single reference, full of advice that you do not seem to follow yourself.


    [PS] Thank you. The poster does not appear the understand the science he/she is criticizing but hopefully will do some more research. Please respond to any further comments in an appropriate thread.

  13. I re-read my post to make sure I didn't misstate anything and you've proven one of my points regarding proponents being less reasonable. In your third sentence of a two post response you call my comments ignorant and worthless. So you didn't even bother to follow my statements to the conclusion. That makes you unreasonable.

    My initial response was to the statement from michael sweet that readers should not "waste" time trying to "understand" the science. Seriously? What about that premise is not directly on topic with this or any thread? And what part of my critique about using the scientific method are you calling ignorant and worthless?

    My second portion is precise and accurate if you were willing to process it before calling my efforts ignorant and worthless. The math can be accurate and weak. Those adjectives are not mutually exclusive. Taking time to explain the language to you is far more off topic than my original post. For example, if f(x) = ax + bx and both a and b are assumptions derived from estimates, the math is potentially correct but definitely weak. Before you attack someone who is trying to learn and instruct, perhaps you should be more REASONABLE and consider the position first. My advice is to research, be skeptical and prove each point. I was responding to another poster's advice to ignore the science and trust a group of people that are still learning and evolving their positions as much as any other research group. I don't need any examples to recommend that readers not follow bad advice.

    This post relates to saturation. The argument in this post is that saturation is not the issue since heat is being transferred to CO2 by convection. I'm not making up the topic, the 11 pages of comments brought up the topic as it relates to saturation. I'm directly on the topic if you cared enough to process my comments. 

    Since there is no mention of convection in the IPCC summary, I had to try and explain some of the details from the supporting references, all of which are already mentioned in this and other posts. So, I don't need to re-reference material here. I tried to be pithy since the post was getting long and you picked apart the abbreviated supporting points while leaving the premise untouched. 

    Thus far, this response is completely off topic since I'm having to defend my language which you chose to attack rather than consider. In an effort to get back on topic and honor the spirit of this site, I'll summarize as follows:

    This topic suggests that the ONLY reason that the saturation argument doesn't hold is because of CO2 heat transfer via convection. For reference, read the post and the comments. I'm not arguing the math or the physics related to CO2 convection. I'm familiar with the calculations in a controlled environment. And despite your incorrect statement, the last several decades DO NOT correlate temperature and CO2. CO2 has steadily increased while the temperature spiked, leveled, and spiked again. Convection does not exhibit this pattern and cannot explain the temperature changes. In order for the convection argument to trump the saturation argument, the convection would need to involve something OTHER THAN CO2. Since the anthropogenic portion of CO2 in the atmosphere is less than 20ppm, there is no way CO2 can explain the temperature. I'm not arguing about the totality of climate change. I'm simply stating the physical limitations with the argument that CO2 convection can adequately explain the storage of IR heat in the atmosphere. The theory (and it is still a theory since the scientific method has not proven it), is that other GHGs are also contributing to convective heating. That discussion is off-topic for this post. But the IPCC math makes huge assumptions regarding the contribution of CO2 in the convective process. Are you suggesting that isn't true? And since the anthropogenic portion of CO2 is extremely small it cannot explain the totality of the temperature anomaly. The IPCC reports do cover this topic, but it goes beyond this thread's subject.

    In summary, the convection story does NOT invalidate the saturation argument. This is the statement I was trying to make and encourage readers to research the topic and NOT trust the IPCC report just because one poster recommended it. Convection only explains the heat differential with one or more of the following:

    1) Non CO2 GHGs are contributing more heat via convection than CO2. If this is true, than what are the ratios of those GHGs? The question remains unanswered without using a model to guesstimate the ratios. I'm a mathemetician and don't support guesstimates as scientific. (the non CO2 GHG question is beyond the scope of this thread)

    2) More CO2 is coming from natural sources or indirectly caused by temperature change (thawing tundra, etc). If this is true, the CO2 is coming from temperature changes and not causing temperature changes. (the CO2 is leading or following temperature change is beyond the scope of this thread)

    Regardless, the IPCC reports support my statements. My conclusion is simple. Since the source of the heat cannot be explained without assumptions on CO2 sources that cannot yet be proven, the math is unable to accurately predict future temperatures with any reasonable accuracy. From a mathematical scenario, a range of 1.5C to 4.5C is not reasonable accuracy. In the lower range, we have little change to worry about. If the upper range, we have dramatic regional climate changes. The math has a 50% error range and cannot be relied upon to divert trillions of dollars. 

    Other than my last sentence, I don't think many would disagree with any of my assertions. This thread is titled "Is the CO2 effect saturated?". The response to the question is YES, CO2 is saturated as it relates to radiant heat, but convection provides the difference. 

    To the readers, research the IPCC reports in detail since the IPCC summary does NOT mention convection. Convective heat transfer is a linear temperature model unless pressure or concentrations change. The temperature changes do not follow the path of a convection heat transfer based on the current CO2 concentrations without additional interference. There is plenty of support for this statement on this site. 

    Consider this article:

    In order to explain the current temperature trajectory, assumptions have to be made for time of year, location, and concentration. Those variables create the huge range of error in the climate models that predict 1.5C to 4.5C over a doubling of CO2. In other words, the models that predict these temperature changes still need dramatic improvements since we simply do not know how to treat all these variables under so many different conditions.  

    I say again, the math is not necessarily flawed, but it is weak. It relies on huge assumptions that no applied mathematician would support since each assumption adds more room for error. In other words, we don't know! CO2 does appear to be saturated for radiated IR and trapped convection doesn't explain the temperature anomaly.

    But I'm "ignorant" and my comments are "worthless" according to the "reasonable" Philippe Chantreau. If only we had a scientific method to help us formulate, test, and MODIFY our hypotheses.   

  14. It's you who need to re-read my post. I very specifically mentioned Marc Morano's comment, quoted at the top of the page on this thread. That comment belongs to Morano, and it is demonstrably ignorant and worthless, as can be shown by any examination of the science behind the radiative properties of CO2.

  15. I'm not sure when green boxes appear in this thread as I'm new to the site. So I'll respond to that one here. 

    Why is my comment regarding the math behind the CO2 saturation question off topic but this comment is considered reasonable?

    There is an easy way to find out how increasing CO2 affects temperature: read the IPCC summary and figure they are correct!! It is a waste of time to attempt to calcualte or completely understand the atmosphere yourself, it is too complex.

    If nobody questioned the IPCC reports we'd be stunting our progress. 

  16. It appears that you confuse radiation and convection. Since you seem enclined to stay on topic, let's go back to the topic at hand, namely the saturation argument, as expressed in the Morano quote. That argument is wrong. Do you have any science to demonstrate otherwise? 

  17. Philippe, I don't understand what you gain by calling anyone ignorant or worthless (me, Morano, or anyone). It is why I made my comment about proponents being less reasonable. If you count the name calling on this site you'll find the majority coming from folks like you that try to bully those of us that want to understand the issue fully before giving a blank check to governmental organizations that don't have a history of good stewardship. 

    I believe the CO2 saturation statement is relevant since the heat stored in the atmosphere cannot be explained by anthropogenic CO2 alone. Temperature observations do not support convection via CO2. The IPCC conclusions agree with my statement and introduce other GHGs to fill in the blanks. That's where I believe the math doesn't work without huge assumptions. I don't trust assumptions without tight mathematical tolerances. A previous poster seems we should take all the IPCC assumptions as gospel. That set me off, and here we are. 

  18. And, by the way, the answer is not yes, it is saturated; it is not. As I said earlier, the extra absorbtion happens in the wings of the spectrum. You do not provide any refutation of that. Convection can not add heat to the system, that's nonsense. The only ways to add heat  to the system is by impairing the cooling of the surface or adding solar insolation.

  19. Marc Morano's comment indicates his lack of understanding of the science, showing ignorance. It leads to a conclusions that's entirely wrong, so it is also worthless. These are objective facts. Calling it anything else wouldn't do it justice.

  20. "Convection via CO2" is nonsense. CO2 does not cause by its presence changes to convection. Convection can not act as a forcing. Additional energy in the system can alter convection patterns, different thing altogether. You clearly lack an understanding that would allow you to formulate an cogent, well informed opinion. The article you linked does not support your position at all, read it more carefully. You also need to read the RC posts on the saturated argument.

  21. Well no, I think we are both agreeing that Morano is correct if we are only talking about radiative heat. 

    Perhaps I don't understand the thread, but I think the site is arguing that Morano is not including heat retained by convection. That doesn't make Morano ignorant or worthless. It makes him accurate but incomplete. There's a huge difference to those of us trying to understand the issues. You can't call him wrong when he is actually correct. The rebuttal in the post suggests there is more to the greenhouse effect than just radiative heat. I agree. So Morano's statement is incomplete but it puts a greater burden on other methods of heat retention such as trapped convection. This is a tremendously important concept since most climate change sites don't mention anything about how the heat is stored other than radiative heat captured by CO2 molecules. It's an oversimplification that is repeated on many climate energy budget graphics. 

    I don't have evidence refuting or supporting Morano. I do have concerns with the calculations that attempt to explain the amount of heat trapped by convection. As I explained in a prior post, the IPCC math is complicated but not impossible to follow. I just wish sites like this one would give a little on how much we DON'T know. Billions in research and we have little more than guesswork on precisely how much heat is being convected through CO2. 

    So, I put it back to you. I agree that Morano is incomplete. But the only hard evidence that he is incomplete, is a suspicion that heat is being convected which cools the surface but heats the atmosphere. OK, we know some of that is happening because it has to. But we don't actually know that CO2 is the primary convection delivery molecule. Maybe it is, maybe it isn't. CO2 certainly is NOT the most efficient of the GHGs at convecting heat. And water vapor is far more abundant but pretty easy to measure. 

    The premise of this thread is that Morano is wrong because he's leaving out convection. The bulk of the responses focus on CO2 alone. We're being beat over the head that CO2 is the key.

    We all agree that CO2 radiated heat is saturated and not responsible for the temperature increases. The top of the thread states that "... the saturation of the absorption at the central frequency does not preclude the POSSIBILITY to absorb more energy." OK, so is Morano wrong or is he possibly wrong? I don't see the myth here. Morano is correct about part of the story. If CO2 can possibly hold more heat through convection, it can possibly not hold enough heat to explain the temperature anomalies. 

    The thread quotes Hulburt and he hedges his conclusion: "Apparently the uncertainties and omissions have conspired to counteract each other to some extent." I agree entirely. 

    So how does the fact that heat is stored in CO2 across a wider band than previously considered 100 years ago change the fact that CO2 can only hold a certain amount of energy for a limited amount of time? In order for the recent temperature records to be modeled, a tremendous variability has to be answered. I just don't think the math works without assuming too much. Again, I'm not talking about the lab coefficients of CO2. I'm talking about the global scenario Morano explores. When the climate moves the molecules around we have tremendous negative feedback. Heat is absorbed all over the planet and it escapes all over the upper atmosphere. None of this changes the fact that Morano is at least paritally correct and we have no idea where the heat goes. We know where large portions go but when the portions are added together we end up with too much heat or not enough depending on the IPCC model that is chosen.

    I don't know why my questions have produced such ire. We know what I'm saying is correct by nature of the number of climate models that are currently in the works. I'm in California and there are 18 models just in Northern California that attempt to predict precipitation:

    These models are off topic but look at the graphic at the top of the article. Would any mathematician actually agree to consider any of this worth publishing? The error rate is so large that we might as well just stop spending money on models and admit we don't know. 

    That's my only premise: Morano is correct but probably incomplete. We don't know where the heat goes and we don't even know if CO2 molecules are the primary convection vehicle or just a secondary heat transport. They might be, but nobody has proven it yet. And since CO2 concentrations fluctuate so much across the planet and year, we aren't likely to prove or disprove anything soon. 

    I just wish we could be intellectually honest about what we don't know and how much variability that lack of knowledge causes before we slam scientists for being incomplete.


    [PS] Your statements here are causing concern because you are making assertions based on you dont know and assuming that science dont know either. You do not appear to be reading material commentators have pointed you to and continue to postulate an incorrect version of how atmospheric physics work.

    It would not be intellectually honest to say we dont know about that things that are perfectly well understood in theory and confirmed by numerous observations and experiments.

    If you want to continue this argument, asserting science is wrong or incomplete, then first you cite the science statements that you beleive is incorrect (eg from the IPCC report). Then you cite the evidence that you believe contradicts the science. You cannot get anywhere postulating the science is based on your bizarre ideas about the role of CO2 molecules in "convective" heat transport. This is nonsense and if that is what the science did postulate, then you would have a point. Take Phillipe's advice and learn what the actual physics is. I recommend Science of Doom's excellent series for the basics. And throw away your own preconceptions for starters.

  22. jjworld,

    You do spout a lot of nonsense. If you are genuinely hoping to understand the science of the greenhouse effect, you will need to stop spouting and take on board that science being presented to you, but probably in small bits.

    And note that @521 you write "I don't know why my questions have produced such ire." yet you don't actually present any questions; just bold unsupported assertions.

    Your assertion that there is some sort of convective effect attached to the greenhouse effect is unsupported by anything anywhere in these threads. Convection is discussed as the mechanisms of heat transfer through the upper troposphere include convection, there being large convective circulations throughout the troposphere. The other mechanism is radiation and for that you need greenhouse gases. 99.95% of the upper troposphere is transparent to radiation. Only 0.05% is radiatively active. These gases are directly responsible for a quarter of the +35ºC greenhouse effect and indirectly responsible for the other three-quarters.

    I hope this reply to your various comments begins to be helpful.

  23. JjWorld :

    As a reader of this thread, permit me to make the observation that your posts present you as highly confused about the physical realities of the Earth's atmosphere.

    Perhaps part of your problem is that you are using neologisms (such as "CO2 convection" ~ a term which is, at face value, meaningless) and you are failing to use the precise terminology of science.   And this failing gives the strong (but perhaps unjustified?) impression that you have not grasped the essential basics of the situation.   Once you attain an understanding of the physics, then you will be able to apply your mathematical skills.

    But to talk of mathematical ideas of error margins etc before you understand the the underlying science of what is happening with the radiation, the molecules, the heat/energy transfers . . . is to put the cart before the horse, and risks you embarrassing yourself even further.

    It might help, if you gave indications of the source of your misinformation ~ for it is clear that you have not used physics textbooks or genuinely scientific formal websites such as the N.A.S., the U.K. Royal Society, the A.A.A.S., or the more informal ones like RealClimate, S.O.D., SkepticalScience, etcetera.


    # FYI, Mr Morano is not a scientist but a propagandist (with a long track record of giving misinformation and disinformation to the general public).   Nor has he redeemed himself, in the matter of CO2 "saturation".

  24. Jjworld,

    You have a severe reading comprehension problem. I did not call you, Morano, or anyone ignorant or worthless. I called Morano's comment ignorant and worthless, and I stand by that statement. There is plenty of scientific literature to justify calling it that, literature that you have declined to discover, despite being repeatedly pointed toward it. Now if you want to have your little feelings all hurt and be a snowflake by proxy of an inanimate thing like a comment, be my guest.

    You say "I think the site is arguing that Morano is not including heat retained by convection." You think wrong. The site does not mention convection a single time. I read it again, the word convection does not appear in the OP. You pulled it out of thin air, showed that you do not understand what it means, then argued about it. That pathetic attempt at spreading the confusion raging i your mind is evident here too: "the convection story does NOT invalidate the saturation argument." There is no convection story othe than what you made up.

    jjworld " I do have concerns with the calculations that attempt to explain the amount of heat trapped by convection." I am not aware of any atmospheric dynamics that can accomplish that, you must cite scientific works including such calculations and expose where you believe the weaknesses are. 

    Further "convection delivery molecule". What in the world is that? How do molecules deliver convection?

    "The thread quotes Hulburt." No, it does not. Where is the quote? Who the heck is Hulburt, why is it relevant? The name, or a quote from the person does not figure anywhere in the OP.

    "The error rate is so large" talking about the diagrams at the top of this page. What is the error rate? Where is the error rate in the diagrams? These diagrams have no other purpose than to explain concepts in a graphic way to a lay audience; as such they do not contain any numbers. They are not graphs of exact data, they are not calculations, they are not from scientific publications, so your attack of "who would want to publish that" is once again BS, completely removed from any reality. Nothing but hot air.

    "When the climate moves the molecules around we have tremendous negative feedback." SO the climate moves molecules around? I would have thought that weather does that. In any case, there is an immense scientific literature on feedbacks, positive and negative. Your arguments seems to be that negative feedbacks prevail; it is again, nothing but hot air if not supported by scientific work, where are the citations?

    "we don't even know if CO2 molecules are the primary convection vehicle or just a secondary heat transport." What in the world could this possibly mean other than that you do not have any grasp of the subject? 

    This funny one " I think we are both agreeing that Morano is correct if we are only talking about radiative heat." So grotesque, it truly falls within the not even wrong category. We do not agree at all, and Morano is so far from being correct that he would need a super fast "vehicle" (of convection or other) to make it back to relelvance within his lifetime.

    This "If CO2 can possibly hold more heat through convection, it can possibly not hold enough heat to explain the temperature anomalies." comes in response to being pointed to the fact that having the central part of the radiation spectrum of CO2 saturated does not preclude the possibility of absorbing more heat, namely in the wings of the spectrum. In a sort of lawyer fashion, you latch on the word possibility and attempt to sow confusion, as if it meant probability, when in this case, it means capability. The gas does absorb more, that can be demonstrated by both experiment and calculation. 

    This gem is priceless "I just wish we could be intellectually honest about what we don't know" and then a suggestion that Morano is a scientist, and "incomplete." I'll let readers appreciate the supreme irony.

    You have been pointed in the right direction and have refused to engage with that. You have attributed fantasy-like concepts to the OP, and a careful read shows that it is all pure invention on your part. You have been asked repeatedly to support you extremely wide-ranging and bold assertions with references, and the only one you mustered does not accomplish anything close to that.

    You have contributed thousands of words to this thread, and so far they amount to little more than technical sounding word salad.

  25. In the discussion about the effect of CO2 on the climate there are certain images which may be said to incorporate the essential part of the arguments. Such iconic graphs are the driving force in changing one's view of the world. A good example is the sun with the planets rotating around it. This stopped all phantasies about what happens at the edge of the (flat) earth. This iconic image made it possible to sail Westward in 1492 in order to reach India.

    For CO2 the iconic image is the rippled increasing graph of the CO2 concentration as measured at Mauna Loa from 1960 onwards, sometimes extended over the past thousand years by observations from tree rings and ice cores to obtain the "hockey stick". For the influence of CO2 on climate the iconic graph is given in Wikipedia (last updated 23 August 2019)

    Caption: "Atmospheric gases only absorb some wavelengths of energy but are transparent to others. The absorption patterns of water vapor (blue peaks) and carbon dioxide (pink peaks) overlap in some wavelengths. Carbon dioxide is not as strong a greenhouse gas as water vapor, but it absorbs energy in longer wavelengths (12–15 micrometers) that water vapor does not, partially closing the "window" through which heat radiated by the surface would normally escape to space."

    The graph shows that the effect of water vapour, H2O, is much greater than the effect of CO2. It also shows the saturation of the absorption due to CO2. The first argument (about water vapour) is valid. We can't do anything about the concentration of H2O though, except perhaps by increasing the temperature. So we will just have to accept this effect. The second argument (about saturation) is also valid. The absorption at wavelength 4 - 4.4 μm is 100% over most of the region, and so too at 12-15 μm. In comparison with H2O the peaks of CO2 are very steep and the wings have little effect. It is only the thin peaks at 2 μm and at 4.9 μm which will grow significantly if the concentration of CO2 is increased.

    The basic physics is simple: A photon of light at a wavelength of 14 μm is passed from one CO2 molecule to the next performing a kind of random walk until it exits the atmosphere. There are two exits, outer space and the earth. Saturation means that a photon starting from the earth has very little chance of exiting to outer space. It is almost certain to exit the atmosphere to the earth, where like shortwave radiation it will be re-emitted at a different wavelength. Even if the new wavelength with probability a half lies in an absorption band of CO2 or H2O, this only means a stay of execution. In the end the photon will escape to outer space through one of the long wave gaps in our atmosphere.

    The graph in Figure 2 in Zhong & Haigh (2013) is perhaps more precise, but the vertical scale runs over twelve orders of magnitude, (twelve orders of magnitude is from one mm to a million km, or from one gram to a Megaton). The result of this scale is that I am not able to comprehend the significance of the graph. Figure 5b, bottom, gives the difference between the radiative flux for the present level of CO2 (389 ppmv) and a level increased by a factor 32 (12500 ppmv). The total negative impact is almost cancelled by the positive impact around 15 μm. This impression is reinforced by Figure 6a where the graph is practically horizontal beyond 400 ppmv. In Figure 6b we see an increase in the slope beyond ten thousand ppmv. In that graph the horizontal axis is logarithmic and runs up to a million ppmv, which is a pure CO2 atmosphere. These results are based on models and therefore should be taken with a pinch of salt.

    The conclusion is: The direct impact on the temperature of the earth of the increase in CO2 from the present level of around 400 ppmv is relatively small. This is due to saturation at the bands where CO2 absorbs long wave radiation.

    Is the graph above misleading? It is described as "(Illustration adapted from Robert Rohde.)". Clicking on Robert Rohde results in the message: refused to connect.
    If anyone knows a better graph I would be very happy to obtain a link.

    There is a nice course on climate denial presented by the University of Queensland The course is free of charge and contains a huge amount of good information on climate change. Unfortunately the course does not address the topic of the absorption of CO2 at specific wavelengths. Neither does the basic rebuttal by dana 1981.

    The near saturation of CO2 at present levels makes it difficult to convince people to vote for a cut in CO2 emissions or for a tax on such emissions.


    [RH] Your image was breaking the page formatting. I can add it back in but it needs to be smaller than 450 px wide, which for that image was going to render it unreadable.

  26. GwsB "the wings have little effect"

    That is false.

    The links at the bottom of this page to RC's saturated gassy arguments threads explains it, as well as other sources.

  27. GwsB @525,

    You ask if that Wiki graph you show @525 is misleading. It certainly is!!

    That Wiki graph simply shows the chance of a photon travelling vertically through today's atmosphere without a particular species of GHG absorbing it en route. It shows nothing of how many such photons would be travelling at each wavelength or even in what direction. The CO2 absorption band at 2.7μm is stopping solar radiation coming in from the sun not IR going out. The CO2 absorption band at 4.3μm sits in the gap between incoming solar radiation and outgoing IR - there are effectively no photons to be absorbed so it has no relevance to climate. And the inability of a photon to travel un-absorbed by GHGs out through the atmosphere does not prevent the mechanisms of the greenhouse effect from gaining strength through additonal levels of GHG. And I should add that the Wiki page you took the graph from provides a woeful attempt to describe the mechanisms of the GH effect.

    You say "The basic physics is simple: A photon of light at a wavelength of 14 μm [15μm] is passed from one CO2 molecule to the next performing a kind of random walk until it exits the atmosphere. There are two exits, outer space and the earth. Saturation means that a photon starting from the earth has very little chance of exiting to outer space." The effect of this 'saturation' is solely that there will be a random walk as all photons will be absopbed. This does not of itself make the chances of IR resulting from that absorption exiting into space small.

    Interestingly, you cite Zhong & Haig (2013) 'The greenhouse effect and carbon dioxide' yet you fail to acknowledge the finding of that paper which is "We conclude that as the concentration of CO2 in the Earth’s atmosphere continues to rise there will be no saturation in its absorption of radiation and thus there can be no complacency with regards to its potential to further warm the climate."

    Instead you set out contradictory conclusions of your own - "The total negative impact is almost cancelled by the positive impact around 15 μm."

    The GH-effect works because the emission & re-emission of IR from the atmosphere containing GHGs will only occur at those same wavebands which subject to are absorption. But the rate of re-emission is set by air temperature. As the temperature drops through the troposphere, the point where emissions will get out into space through the thinner upper atmosphere; that point in the troposphere will be colder. Thus the GHG at that higher altitude will re-emit less IR because it is colder. The more the GHG in the atmosphere, the higher the altitude and the bit of troposphere which emits into space and thus the less IR is emited.

    Of course, as the graphics in Zhong & Haig show, that mechanism will go into reverse as the altitude becomes high enough to reach the stratosphere. In the stratosphere, temperature rises with altitude and so the more GHG the greater the IR emissions into space. This is the mechanism which you mention being apparent in their Fig5b which you say results in the increasing GH-effect being "almost cancelled." However, the extra GHG effect of CO2, although reduced with increasing CO2 concentrations in the well-konwn logathithmic relationship, does not peak even if the 15μm band is taken in isolation. It keeps on increasing. And at CO2 levels above 2500ppm(v), the 15μm band is boosted by a compound absorption band at 10μm.

    The climate forcing of CO2 does not hit an upper limit. In the words of Zong & Haig (2013), "as the concentration of CO2 in the Earth’s atmosphere continues to rise, there will be no saturation in its absorption of radiation."

  28. GwsB @525 ,

    you have completely failed to understand the CO2 (and H2O) mechanism of "greenhouse".

    Before you embarrass yourself by making further comments about CO2 saturation, please read & think about Dana's OP, and check out RealClimate & other information above. 


    [PS] Please watch tone.

  29. GwsB:

    You have received a rather negative reaction, because you have made some pretty strong claims based on some faulty reasoning. Regulars here can be pretty impatient with such proclamations from newcomers.

    Let me try to explain where your error lies. To begin, thanks for making it clear just what you think "CO2 effect is saturated" means - often people that make that argument are less than clear. You have based your argument on the (correct) observation that very little IR radiation can travel directly from the surface to space.

    The part where your argument breaks down is actually hinted at in your post. You state that IR radiation absorbed in the atmosphere can be re-radiated - sometimes up, sometimes down. Eventually, that energy will be emitted to space, but it is delayed. Let us look at the implications of that.

    Radiation absorption is a logarithmic function, expressed by Beer's Law. If  a certain thickness of the atmosphere can absorb 10% of the IR radiation,and transmit 90%, then the amount passing directly through is 0.9 of the original value. The next layer (same properties) then transmits 90% of 90%, or 09.*0.9=0.81. The third layer will allow 0.93 = 0.729, and so on.

    The figure below shows that decline. It also shows the same result for a case where each layer transmits 95%, instead of 90%. The layer-by-layer sequence for 0.95 is 0.95, 0.952, 0.953 etc. Note the following:

    • After 200 layers, both curves show essentially zero transmission, fitting your "saturated" argument.
    • In the middle, however, the two curves are clearly not the same.For a coefficient of 0.9, it takes almost 23 layers to reduce transmission to 0.1. For a coefficient of 0.95, it takes almost 46 layers. (Yes, the doubling of the distance is an exact mathematical result of Beer's Law, and the per-layer doubling of absorption from 0.05 to 0.1.)

    The "saturation" argument fails to include that intermediate difference, and that is where it goes very, very wrong. This difference in how much IR radiation is transmitted how far is essential to understanding the greenhouse effect. Adding CO2 has a neglible effect on how much IR radiation can pass directly from the surface to space in a single step, Adding CO2 does affect how far IR radiation gets in a single step, and this affects how many steps it will take before it can finally reach high enough in the atmosphere to escape to space.


    Beers Law decay


    You can see this in the figure I provide, if you read it from right to left - i.e., think of the right as the surface, and the left as space. IR radiation emitted upward (to the left) at layer 10 has a 39% chance of escaping to space for a coefficient of 0.9, but a 63% chance for a coefficient of 0.95.

    (Note: the values and layers in the diagram are purely illustrative. Radiation transfer in the atmosphere needs to be calculated at many different wavelengths, not a single number as shown above. The general principle is correct, though.)

    As CO2 or other greenhouse gases increase, the IR lost to space originates at a higher altitude, where the atmosphere is colder. This means less IR lost to space, until the atmosphere can warm to compensate.

    An analogy for your "saturation" argument would be a foggy night, where you can't see the building two blocks away, but you can see a building one block away. From the perspective of the distant building, visibility is "saturated" - no light from the distant building is reaching your eye. Does this mean that adding more fog has no effect? No, because additional fog will eventually make it impossible to see the building that is only one block away.

    Proper examiniation of the effects of adding CO2 to the atmosphere requires that the effects throughout the atmosphere be included, not just the direct transmission from the surface to space in a single step. And the calculation that include all those effects show clearly that adding CO2 leads to surface and tropospheric warming.

  30. I am sorry for perhaps making a basic question (my first post). But in that last submitted graph the first layer is numbered to the left where most of the effect is happening. So shouldnt that left side be seen as the surface of the earth? And the right side be seen as space?

  31. OK, i see what you mean after i reread your post. But the graph description also says Beers Law decay. Is that curve really applicable for energy transmitted into space for each layers?

    If yes, what coeffecient is 400 ppm corresponding to, compared to 800ppm?

  32. PringlesX:

    Let me try to explain from a slightly different approach. First, keep track of the point that a coefficient of 0.95 means IR radiation is more easily transmitted through a single layer that when the coefficient is 0.9. So the 0.9 curve is the one with higher absorbing gases.

    In the graph I posted in comment 529, moving from left to right tells you the probability of a photon being transmitted through to layer #x. After 20 layers:

    • with a coefficient of 0.95, the probability is 0.397
    • with a coefficient of 0.9, the probability is 0.135

    Another way of thinking about it is the absorption. By layer 20:

    • with a coefficient of 0.95, the probability of being absorbed before reaching the top of layer 20 is 0.603
    • with a coefficient of 0.9, the probability of being absorbed before reaching the top of layer 20 is 0.865.

    Now, iet's think about what happens to a photon that is emitted upwards from high in the atmosphere, 20 layers from space. What are its chances of either being absorbed in those 20 layers, versus its chances of being transmitted to space in one step? We can get that from the graph, too, because the graph gives us both the probability of absorption and the probability of transmission:

    • with a coefficient of 0.95, the probability of transmission through 20
    • layers (i.e., reaching space) is 0.397
    • with a coefficient of 0.9, the probability of transmission is 0.135

    Getting back the the "saturation" argument, we can see that decreasing the transmission coefficient from 0.95 to 0.9 (increasing absorption, due to increasing greenhouse gas concentrations) reduces the chance that IR radiation from a height 20 layers from space will be lost directly to space. So, the IR radiation that does reach space is more likely to be emitted at a higher altitude (close to space).

    The "fact" that the whole atmosphere (200 layers) is "saturated" (no direct transmission) misses this important feature.

    Does that help?

  33. Thanks for your answer. 

    As i see it, this graph depicts how diffused this transmission border is. And its already thin and very high up in the athmosphere compared to the number of layers the photons have to process.  

    Isnt safe to say that the areas ABOVE the lines, are the real difference between the CO2 levels from a photon perspective?  If that is so, then it can be argued that the scenario is more or less saturated?

  34. PringlesX:

    Please note that the graph I have provided is not an accurate cacluation of IR transmisison in the atmosphere - it is a very crude example of how IR radiation would be transfered in an idealized "200 layer" situation. For real atmospheric transmission, the same Beer's Law applies, but you need to also consider:

    • A very large number of specific wavelengths of IR radiation, each with its own absorption coefficients
    • A large number of radiatively-active gases (of which CO2 is but one), each absorbing in varying amounts at a number of different wavelengths.
    • Each layer in the atmosphere also emits IR radiation (upwards, downwards, and sideways), so the total travelling either upwards or downwards at any height is a combination of the amount emitted in that layer plus the amount transmitted from adjacent layers.
    • The emissions or IR radiation depend on local temperature and gas concentrations. (Good absorbers are also good emitters, so adding CO2 makes the atmosphere emit IR radiation more efficiently.)
    • Radiation is not the only mechanism moving energy up and down through the atmosphere. Convective motion transfers energy, as either heat or water vapour (evaporated at the surface and condensed at altitude).

    So the figure above is a very simplistic version of total IR radiation transfer.

    Climatologists have "done the math" on this. (Well, a lot of the radiation theory was extensively developed by the military in the 1960s so their heat-seeking missles could use IR radiation to detect hot items they wanted to blow up.) The math says that adding CO2 will have a significant effect on radiation transfer in the atmosphere.

    The math says "the atmosphere is not saturated for IR radiation transfer, for any useful or accurate concept of "saturation". The only "saturation" that occurs is for useless and innacurate descriptions of the process.

    The area under or over the curves in my graph simply demonstrates that for two reasonable absorption coefficients, where the start and end points are the same (1 @ layer 0, and 0 @ layer 200, so "saturated" by one definition), you get very different results in the middle. When you see someone arguing that "the CO2 effect is saturated", there are two possibilities:

    1. They haven't done the proper math and looked at what happens in the middle (or are relying on a source that hasn't told them about what happens in the middle).
    2. They know that what happens in the middle and are not telling you about it because they know it refutes their argument.

    My guess is that most people fall under category 1. If they are relying on a source for their information (rather than calculating it themselves), then most of the time they are relying on a source that can probably be connected eventually to someone that falls in category 2.

  35. Yes, it has an effect on how broad/diffuse the radiation border is. But still, sorry, i cant see the big difference in insulation effect with the information you are providing.

    Also on top of that, CO2 frequency bands not covered by Water vapour is only responsible for about 7% of the energy (?). Decreasing that already very thin transmission border even thinner doesnt seem to be able to do any catastrophic changes in insulation effect by itself.

    Unless we could find better curves or explanation. Do you have some good sources that made you convinced about the large effect?

  36. PringlesX , it might be worthwhile taking a step back, to look at the bigger context.

    The planetary energy balance is determined by fluxes at the Top Of Atmosphere.  But the TOA is a band of altitudes, depending on different radiatively-active molecules.  The H2O effect is large — but occurs at lower altitude, because cold-temperature precipitation means that H2O molecules are scanty at the high altitudes (where CO2 is still "going strong").

    So despite the IR radiation overlap between CO2 and H2O, the end result is that the CO2's greenhouse effect is disproportionately large for its small presence.

    ( I'm quite uncertain about the correctness of the 7% figure you mentioned ~ but there are knowledgeable posters here who might be prepared to discuss that particular point.  But whether 7% or 17% etcetera, it is the end result of energy balance which matters.)

    The other point is that you must consider the lapse rate , in looking at the mechanism of "greenhouse".   Very important.

  37. Might also be worth pointing out that Bob's diagrams are worth studying for understanding what is going on, but for real applications (whether GPS, heat-seeking missiles or climate models), you need to do full integration of the radiative transfer equations which funnily enough back the consensus science. Observations of change in radiation as CO2 increases from both earth looking up and satellite looking down match the solutions from the RTE integration with very high precision. See the examples here.  My favourite paper working through it all is Ramanathan and Coakley 1978.

    I am curious as to where the "7%" came from. This paper which I believe to be the consensus position makes it more like 20%.

  38. Thank you both.

    I believe The 7% figure is the Co2-band area minus the H2O overlap.  
    But yes, regarding the total effect causing increase in temperature there are different complicated models taking feedback effects into account
    that talks about much higher percentage effect.

    "The planetary energy balance is determined by fluxes at the Top Of Atmosphere. "
    Yes, that seems to be the case.  

    (The last clips in this series (about 40-61) are explaining how the frequency overtones developes with altitude which could be interesting for those readers not familiar with it.)

  39. The straight radiative balance (ie doubling CO2 gives you an extra 4w/m2 of surface irradation) would only raise temperatures 1.1C. It is the feedbacks that lift this to around 3C, in part from increased water vapour as well as albedo and clouds.

  40. PringlesX:

    You ask, "Do you have some good sources that made you convinced about the large effect?"

    I am reminded of a time, many years ago when we had some construction workers at a research site I worked at, who were quite intrigued by all the instrumentation and such. One asked "what did you do to get a job like this?" I answered, "I have a PhD in Physical Geography". I think that was more preparation and work than he had hoped for.

    [My speciality was Climatology.]

    There is no one source that "convinced" me. There is a huge body of science behind our understanding of climate, dating back to the 1800s. If you are curous about the history, I suggest reading "The Discovery of Global Warming".

    I first started learning about climate as an undergrad in the 1970s, mostly via textbooks. In the 1980s, as a grad student, I was introduced to much of the primary literature (as it was at the time). As such, much of my understanding comes from the primary literature, not web pages or books. Here at SkS, I have on several occasions referenced the following paper:

    Manabe and Wetherald (1967) Thermal Equilibrium of the Atmosphere With a Given Distribution of Relative Humidity

    The link to the journal is here, and a free copy is also available here. The paper describes a one-dimensional climate model that includes exactly the kind of calculations I have been discussing with you. The fact that this is from 1967 should tell you that people have been working on this for a long time.

    Of course, our understanding has improved since then. People often refer to the IPCC reports, which attempt to give a summary of current understanding. For a simpler version, I think the very first report in 1990 is easier to read than the later ones, because it covers the basics to a greater extent.

    If you want to focus on IR radiation transfer only, then you can play with a model on-line at this web site. Note that radiation transfer is dependent on things like cloud, temperature, other gases, location,  etc., so that web page gives you a lot of options to choose some typical defaults. You can choose an altitude, and direction (up or down). At the very least, playing with that model might help you realize that there is no one single source of information that will convince you (or anyone).

    As the discussion continues, be careful with statements like "But still, sorry, i cant see the big difference in insulation effect with the information you are providing." That starts to look like an argument from increduility, which is a pretty weak position.

    Scaddenp has already referred to CO2 doubling causing a reduction of 4W/m2 in outgoing IR radiation at the top of the atmosphere. Before you say "gee, that seems small", the climatological question is "what changes have to happen to bring the system back into equilibrium?"That answer was already provided by scaddenp, too: 1.1C temperature rise (global average) without feedbacks, or more like 3C with known feedbacks. You can see some of this in the Manabe and Wetherald paper I reference above. To put it simply, adding 4W/m2 to every part of the surface, for the length of time it takes to readjust, adds up to a lot of energy.

  41. PringlesX @538,

    You link to a particular YouTube lecture which is No 19 of a series of 61. We can see a 7% figure for the CO2-contribution to the total GH-effect as being part of the conclusions reached in Lecture 52. It would be incorrect to suggest this 7% figure is the actual value. It is not.  In the absence of other GHGs, CO2 would provide 25% of today's GH-effect. With other GHGs, the actual figure is dependent on the proportion of cloud/clear-sky so cannot be precisely calculated but is not far short of 20%.

    There are many video lectures in the lecture series you cite, so which rabbit-holes it dives down to reach its eventual conclusions in Video 61 would take a lot of viewing. Suffice to say, I have seen no indication that the lecturer with all his mathmatical confidence properly understands the effect of CO2 on our climate and his insistence that H2O is the stronger GHG is presented without mention of the H2O only being in that atmosphere in significant levels because of the presence of CO2.

    I'm not sure of the source of this graphic below (it features deep in a Clive Best comment-thread) but it is quite instructive, as is this video which uses the same W Pacific IR data, The areas  where the IR into space is dropped below the surface temerature S-B line show the size of the GH-effect and the contribitions from different gases.

    GHG & outward IR

    The 61 iLectureOnline lectures yo cite @538 makes much of how much IR makes it unabsorbed from the surface into space. The GH-effect does not work like that, It relies on the temperature of the atmosphere at the altitude from which IR can make it unabsorbed into space.

    Add H2O and this will not effect the 15 micron band. The level of CO2 means the altitude with a clear run at space is far above any significant H2O effect. So that important altitude remains defined by CO2.

    Add more CO2 and the important altitude rises and, excepting the small central part that is already up in the stratosphere, such a rise in altitude means a lower temperature at the altitude emitting into space. The lower the temperature, to less the emitted radiation (as per the S-B curves) and the resulting need for the planet to warm until inward/outward radiation are again in balance.

  42. Bob Loblaw's curves in 529 exhibit exponential decrease. The decrease actually is a power law, more precisely the fraction exiting at the top is inversely proportional to the length of the column (or the density). If photons only travel upwards there would be exponential decrease. However photons are emitted by the CO2 molecules in all directions.

    Here is the argument for (the discrete version of) 20 layers, which I number by 0 ... 19 from bottom to top. Bottom is the surface of the earth, top is outer space. Each layer contains the same amount of CO2. The argument is schematic. At the end of the post I come back to the topic of saturation.

    Assume at level k there are 20-k photons for k=0, ..., 19. Half the photons jump downwards (to k-1) half upwards (to k+1). So level k loses all 20-k photons, but receives (21-k)/2 photons from its neighbour below and (19-k)/2 from its neighbour above. Thus it ends up with 20-k photons. This is the steady state. The bottom level, k=0, and the top level, k=19, need special consideration. These two levels form the boundary of the system.

    1) At level k=0 half the photons go down into the earth and leave the atmosphere, and half go up to level 1. On the other hand level 0 receives 19/2 photons from level 1. In order to have a steady state we must assume an influx of 21/2 photons from the earth (due to heat radiation of the earth).

    2) At level 19 there is one photon. Half this photon goes up into outer space, half down to level 18. Level 19 receives 2/2 photons from level 18 and none from outer space. So it ends up with one photon. Steady state.

    The full picture is: At each step there is an influx of 21/2 photons from earth (due to the heat of the earth) to level zero and an outflow of 10=20/2 photons from level zero to the earth and an outflow of 1/2 photon from level 19 to outer space. That results in a steady state.

    This description agrees with observations. Doubling the length of the cylinder (or the density of CO2) will reduce the amount of radiation into outer space by 50%.

    The actual situation is more complicated. At each level there are millions of photons. Each photon flips a coin to decide whether it takes a step upwards (if the coin shows heads) or a step downwards (if the coin shows tails).

    The actual situation is more complicated. The photon will travel a random distance in a random direction (uniformly distributed over the unit sphere) before being absorbed. The distance is in the order of ten meters, the time between being absorbed and re-emitted is of the order of 100 femtoseconds. Since the photon moves at the speed of light the whole random walk from leaving the heat bath of the surface of the earth until returning to the earth or flying off into outer space occurs in a twinkle of the eye. On my imac I can simulate a hundred thousand such random walks in a matter of minutes using a program of twenty lines of code in R.

    Actually it might be better to speak of reflection. CO2 reflects some of the photons back to earth and others manage to pass to outer space. We speak of saturation if 99% or more of the photons are reflected back to earth, equivalently if 1% or less of the photons manage to escape to outer space.

    The figure below gives a good picture of the effect of an increase of the amount of CO2 for different wave numbers. The proportion which manages to escape depends on the density of CO2 and on the wavelength of the photon. At wavelength 15 μm (650-680 cm-1) there is saturation. In the shoulders we are close to saturation. Doubling the density of CO2 will halve the number of photons which manage to escape. In the far wings the majority of the photons manage to escape and only a small proportion is reflected back to earth. Doubling the intensity will double the number of photons reflected back to earth. This also holds for the 10 μm wavelength (the red curve for wave number 850-1100).

    If one makes plots for these different wavelengths with the amount of CO2 on the horizontal axis and the number of photons reflected back to earth on the vertical axis, and if one uses a logarithmic scale on the horizontal axis and a linear scale on the vertical axis, one obtains the plot below:

    The curves are exponential curves because of the logarithmic scale on the horizontal axis. The black, sky blue and green curves have the form y=a-exp(-c(x-b)) where $x$ varies from 1 to 6. The constant a, b and c depends on the colour: a=0 (black), a=8.5 (sky blue) and a=9 (green). The red blue and pink curve have the form y=a+exp(c(x-b)). In the plot below the coefficients a, b and c have been chosen so as to get a reasonable fit.

    The plot at the top is Figure 6(c) in Zhong & Haigh (2013) "The greenhouse effect and carbon dioxide". The plot at the bottom is a free hand fit by exponential curves. At present the contribution for the six wave number intervals is approximately the same. Saturation holds at the central interval, but not yet at the shoulders. The contribution of the wings will become predominant if the amount of CO2 passes the level 40 000 ppmv, when CO2 makes up more than 4% of the atmosphere. At that moment saturation holds at the shoulders. The instantaneous radiative forcing is approximately 9 for all five curves which adds up to 45 (see Figure 5(b) in Zhong & Haigh) which corresponds to an increase in temperature of 11K. That increase is without feed back effects.

  43. The two figures in post 542 were not copied. They seem to be in the wrong format. I refer the reader to Figure 6(c) in Zhong & Haigh (2013) "The greenhouse effect and carbon dioxide" for the first figure, see

    The second figure is less important. It shows an approximation to the first figure in terms of exponential curves. The reader can make these approximations himself if she is interested. I am unfortunately not able to insert the pdf file into this window.

  44. GwsB @543,

    Figure 6 from Zhong & Haig (2013) is below with caption added beneath.

    Zhong & Haig (2013) fig6

    Caption (a) Instantaneous Radiative Forcing of CO2 (relative to the present‐day concentration) as a function of volume mixing ratio. The red curve is for the whole infrared region, 0–3000cm−1. The blue curve covers only the spectral region 550–800cm−1 (i.e. the 15μm band). (b) As (a) but extending to higher CO2 mixing ratios and presented against the logarithm of volume mixing ratio. (c) Radiative Forcing against CO2 mixing ratio for the six spectral intervals.

    I'm not sure if fig6c is as easy to understand as Fig 5 of that same paper which I paste below, again with caption. (Plus it does provide both wavelength and wavenumber which is helpful, and being less wide, it can be displayed a bit biggerer than Fig6.)

    Zhong & Haige Fig5

    Caption (a) The top of atmosphere infrared spectrum calculated with CO2 mixing ratio (ppmv) of 0 (light blue curve), 1.5ppmv (green), 389ppmv (black), 2 × 389ppmv (purple) and 32 × 389ppmv (red). The vertical dashed lines mark the sub‐intervals discussed in the text: the CO2 15μm band core (650–680cm−1), the band central regions (590–650cm−1 and 680–750cm−1), the band wings (450–590cm−1and 750–850cm−1), and the CO2 10μm bands (850–1100cm−1) which overlap the O3 9.6μm band. (b) The differences between each CO2 spectrum in Figure 5(a) from that with the current CO2 concentration (389ppmv).

  45. GwsB,

    In post 542 you describe 20 atmospheric layers.  If the atmosphere had 20 layers with the same amount of CO2, they would not all be the same thickness.  The top layer would be many times thicker because the atmosphere is thinner higher up.  Molarity is much lower higher up. There is much less water because it is very cold.  The CO2 path length is many times longer due to the lower CO2 concentration (400 ppm means lower Molarity at lower pressure.  You appear to think the same Molarity of water and CO2 exist throughout the atmosphere.  Ppm is not concentration, it is a fraction of concentration)

    It appears to me that you have not considered the concentration differences at altitude so your model is incorrect.  In general it is a waste of time to compare your own model to peer reviewed data.

    The key to saturation is the lower CO2 and water concentration at height.  Essentially no water exists at the escape altitude.  Your model ignores these facts.  At the escape altitude there is no saturation and adding more CO2 increases the absorption.  That increases the escape altitude and causes surface warming.

  46. GwsB,

    It may be the problem with your model is that the number of photons emitted from one layer is not related to the number of photons it receives from other layers.  The number of photons emitted is determined solely by the temperature of the layer. 

    Esentially all of the photonic energy received is immediately turned into heat.  Then photons are emitted according to the Boseman relationship (t to the fourth power).  Higher layers emit less photons per m2 than lower layers because they are colder.  Your model ignores the temperature differences.  A single photon does not random walk to outer space.  A modeled walk at light speed does not account for the time spent as heat. 

    When higher layers absorb more photons coming up (because the CO2 concentration is higher due to man made CO2) the escape altitude increases.  The temperature is lower at the new escape altitude because the atmosphere cools as you go higher (at the lapse rate).  This causes an energy imbalance because less energy is emitted at the cooler altitude according to the Bozeman relationship.  The new altitude has to warm to return to energy balance.  This warming is transmitted down according to the lapse rate and results in surface heating.

    At the escape altitude the CO2 absorbtion bands are not saturated so increasing CO2 increases absorbtion.  Water is essentially not present so overlap of bands with water does not count either.  The escape altitude increasing is the key to understanding the greenhouse effect.  The lapse rate is 6C per kilometer.  The escape altitude is about 10,000 meters.  If the escape altitude increases 100 meters the surface temperature increases 0.6C.

  47. Thank you MA Rodger for posting the figures in Zhong and Haigh (2013). Would it be possible to print 6(c) separately in a post so one can read the explanation inside the figure.

    The black line in Fig 6(c) which is horizontal to the right of 10**2 shows the instantaneous relative forcing due to the central interval of the CO2 absorption 650-680/cm, which is 15 μm plusminus 2%. At the present level of 400 ppmv there is saturation. Fig 2 in Zhong and Haigh (2013) shows that 650-680 is the peak of the absorption coefficient for CO2 between 500 and 1500/cm. The absorption coefficient in the central interval lies between 100 and 1000. In the shoulders the absorption coefficient lies between 1 and 100 and in the wings it is less than one. This is a rough impression. Figure 2 is not very detailed. The statement: "At wavelength 15 mm there is saturation" is true. The statement: "The contribution of the shoulders compared to the central region around 15 μm is negligible" is also true if one looks carefully at Figure 2. It is only by looking better at Figure 6(c) that one sees that the shoulders 590-650/cm and 680-750/cm do make a significant contribution and that saturation at these wavelengths is still far off (it will occur at 40 000 ppmv).

    Zhong and Haigh (2013) have used the latest version HITRAN2008 for the analysis which underlies their paper. It is possible that older versions give different results for which the absorption of the shoulders is weaker. The notion of saturation is based on the iconic figure in Wikipedia which was removed from my post 525 since it was too large. Saturation is a serious objection and it takes a lot of work (see Zhong and Haigh (2013)) to counter it.

    The post 542 tries to get at the basics of "absorption" or "reflection" for long wave radiation at around 15 mm. The model I describe is a basic description in terms of photons. Since I am a mathematician specialized in probability theory it seems quite natural to me to use a random walk. I was surprised to see how well it fits with Figure 6(c) in Haigh and Zhong (2013) where one looks at narrow bands of wavelengths. The logarithmic increase shown in Figure 6(b) between 50 and 5000 is a fluke. It is meaningless. It is the result of adding a constant function, two concave functions and three convex functions in Figure 6(c).

    The basic description in terms of reflection in post 542 does not take secondary effects like temperature differences in the troposphere into account. It is based on the idea that photons don't just disappear. They may be absorbed, but are emitted again within a fraction of a second. So I have problems with the first paragraph of post 546 by Michael Sweet which seem to suggest that there is no conservation of photons.

    My understanding is that the amount of heat (energy) due to the vibration caused by the absorption of photons at around 15 mm is negligible, and that it is the long wave radiation reflected back to earth as described in the random walk model which is the "greenhouse effect".

  48. Many of those spectrum in previous comments, is not showing the whole infrared transmission spectrum below 400 1/cm. Why?    It seems be manipulative if there isnt good reason for it. 

    Anyway, I found a interesting site from chicago university that simulates the band saturation.

    CO2 band saturation effect

    (The site used in the following video:)


    [DB] Please limit image widths to 450.  Subsequent violations will be removed.

    Inflammatory snipped.

  49. We seem to agree on that the effect lays in the TOA and the transmission curve at high altitudes.

    So, just for fun, is it possible to explain the argumented athmospheric big effect with some analogy? :-)
    If i am outside in antartica in 100 layers of sleeping bags. But the most outer sleeping bag is only a cotton layer so it radiates a lot from this layer at all its internal altitudes with the wind blowing though it etc.
    Double the amount of CO2 to 800ppm corresponds to exchanging that 100th cotton layer into a regular sleeping bag.   So now the transmission curve has changed drastically of the top layer.

    But i was already in 99 nice sleeping bags. Could you alter the effect in this scenario that corresponds to what you believe is actually happening?

  50. PringlesX , 

    sorry, but your "sleeping bag" analogy  simply doesn't fit the situation.

    And there seems to be no connection between Greenhouse and the "hockey stick".

    Since the Hockey Stick has been well validated by a number of subsequent scientific studies (even without tree-ring data) . . . then it sounds like "Manhattancontrarian" is probably just one of those many clickbait blogsites.  You know ~ one of those clickbait sites with stuff like "Scientists prove Earth is flat" . . . "Infrared photos show English Queen is a Lizardperson" . . . "Russian lasers show Moon is green cheese" . . . and so on.

    Really, PringlesX, if Mr Manhattancontrarian has some astounding new earth-shattering information on The Hockey Stick (info is which strangely unreported by the world's media) ~ then please, please give us readers a succinct summary of it.  On the appropriate SkS thread, of course.  Let's not go down the brainless clickbait path !


    [PS] Please refraim from discussing "hockey stick" on this topic. Discussions of that belong here.

Prev  1  2  3  4  5  6  7  8  9  10  11  12  13  Next

Post a Comment

Political, off-topic or ad hominem comments will be deleted. Comments Policy...

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.

Link to this page

The Consensus Project Website


(free to republish)

© Copyright 2022 John Cook
Home | Links | Translations | About Us | Privacy | Contact Us