From the press package:
The findings confirm that carbon dioxide is the most potent greenhouse “control knob”
This seems like a last ditch effort (in the face of falling public opinion) from Gavin Schmidt et al. to make CO2 more important than water vapor in regulating the temperature of the planet.
Via emailed press package, embargoed until 2PM EST 10/14/2010:
Of all the greenhouse gases in the atmosphere, carbon dioxide exerts the most control on Earth’s climate, researchers report. Although carbon dioxide’s greenhouse effect has been known for more than 100 years, its primary role in climate warming is still not universally acknowledged.
For example, water vapor is a powerful greenhouse gas and is more abundant in the atmosphere than carbon dioxide. But, it condenses and precipitates from the atmosphere and thus plays a different role than carbon dioxide and other, noncondensing greenhouse gases, such as ozone, methane and chlorofluorocarbons. Andrew Lacis and colleagues conducted a set of idealized climate model experiments in which various greenhouse gases were added to or subtracted from the atmosphere, in order to illustrate their roles in controlling the temperature of the air.
The findings confirm that carbon dioxide is the most potent greenhouse “control knob” and that its abundance determines how much water vapor the atmosphere contains. Without carbon dioxide, the Earth would plunge into a frozen state, the researchers report, though they caution that increasing levels of this atmospheric gas are also worrisome. “This makes the reduction and control of atmospheric CO2 a serious and pressing issue, worthy of real-time attention,” they write.
[Seems a bit out of balance though.]
- Fig. 1. Attribution of the contributions of individual atmospheric components to the total terrestrial greenhouse effect, separated into feedback and forcing categories. Horizontal dotted and dashed lines depict the fractional response for single-addition and single-subtraction of individual gases to an empty or full-component reference atmosphere, respectively. Horizontal solid black lines are the scaled averages of the dashedand dotted-line fractional response results. The sum of the fractional responses adds up to the total greenhouse effect. The reference atmosphere is for conditions in 1980.
Article #14: “Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature,” by A.A. Lacis; G.A. Schmidt; D. Rind; R.A. Ruedy at NASA Goddard Institute for Space Studies in New York, NY.
Contact: Andrew A. Lacis at alacis@giss.nasa.gov (email).
Here’s the paper: lacis101015 (PDF)
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David A. Evans says:
October 14, 2010 at 10:46 pm
The evaporation, & subsequent convective movement of the energy involved is huge in comparison to CO2 radiative absorption & re-radiation,
And the loss to space by radiation is infinitely bigger than the loss by convection!
Phil. says:
“…the loss to space by radiation is infinitely bigger than the loss by convection!”
Wrong once again. Light atoms [eg; helium] and molecules [hydrogen] routinely escape to space. They don’t do it by radiation.
They seem to be confusing C02 with clouds and the oceans, but yes, the earth does have a pretty remarkable thermostat, keeping our temperatures fairly even.
When all you have is a C02 hammer, everything looks like a climate nail.
Roger Pielke Snr sums up nicely:
My conclusion is that their paper does not present new scientific insight but is actually an op-ed presented in the guise of a research paper by Science magazine.
http://pielkeclimatesci.wordpress.com/2010/10/15/comment-on-the-science-paper-atmospheric-co2-principal-control-knob-governing-earth%E2%80%99s-temperature-by-lacis-et-al-2010/
Phil. says:
October 15, 2010 at 10:13 am
Perhaps I wasn’t clear enough.
I know that ultimately radiation is the main loss of energy but how does the radiative loss from the surface compare?
The switch from double to triple glazing is far more effective than IR radiative mirroring which suggests that conduction & convection play a much larger rôle than that attributed.
DaveE.
Mike says:
October 15, 2010 at 9:07 am
“… Now imagine that 2/1,000ths of 1% devastating planet earth…..because I can’t!
Have at it…am I way off on this?”
I think you got it. That’s why I call this “Pathalogical Science”. They want to attribute fantastic effects to such a small input.
“”” Gareth says:
October 14, 2010 at 1:23 pm
I sometimes wonder why empirical evidence is not being obtained to support man made climate disruption warming change along the lines of creating artificial atmospheres that match Earth’s in sealed units with different concentrations of CO2 but other variables constant, expose them to a regulated light source and demonstrate that the extra CO2 results in a warmer temperature. “””
Gareth you are right; it is not that difficult experiment to do. As far as I know, it has NEVER been done in public so we could all watch. People have certainly tried to do it in public; but they have ALL made the same mistake that you just made:-
“”” expose them to a regulated light source “””
There is your problem. the “Greenhouse Gas” effect has absolutely NOTHING TO DO WITH LIGHT.
LIGHT by definition is visible to the HUMAN eye, and is generally in the spectral range of 400 to 800 nm wavelength.
The Greenhouse gas effect that involves CO2, H2O, CH4, O3 , whatever is involved with ONLY that thermal LWIR radiation that is emitted by the gound, ocean and atmosphere due to their Temperatures, and generally is limited to the spectral range from about 5.0 microns to about 80 microns (98%) corresponding to a mean earth Temperature of about 288K, or +15 deg C.
So you can do the experiemnt but instead of your “light source” you have to use a LWIR thermal radiation source; such as perhaps an ordinary brick out of your garden; whcih you can chill down to about 15 C with a few minutes in the fridge.
Well actually nobody is going to rag on you if you just leave the brick at room temperature of maybe 20-25 deg C. But that is the correct sort of energy source that you need to use to demonstrate the greenhouse warming effect in your two atmospheric samples containing different trace amounts of CO2.
Unlike light which the human eye can detect; the LWIR thermal radiation from a brick; which would be about 390 W/m^2 at +15 deg C, is NOT DETECTABLE by ANY human sensory mechanism. We don’t detect it as “light”; we certainly don’t detect it as “heat”.
So yes it is quite trivial to do the experiment as you suggest; it is just that everyone who tries it; decides to fake it; and use some other source of energy; which simply is an invalid experiment.
And once again we learn that molecules of “whatever” are perfectly happy to emit copius quantities of electromagnetic radiation while they are part of either a solidd mass, or a liquid mass; but that the instant they are freed from that constraint, to become independent gas molecules they instantly cease radiating electromagnetic radiation. Simply amazing that such a phenomenon seems to be not well known as it should be.
Pamela Gray says:
October 14, 2010 at 7:42 pm
“Manmade …” …okay…I can’t say it. And I’m quite sure I would be snipped if I did.
“Manmade …Global Knob Twisting?”
Frank K,
citation:
Furthermore, the atmospheric residence time of CO2 is exceedingly long, being measured in thousands of years (23). This makes the reduction and control of atmospheric CO2 a serious and pressing issue, worthy of real-time attention.”
Ref 23 is to the paper of Joos et al, who have provided the IPCC with their carbon cycle model, and confirm their model in this paper. The entire IPCC AR4 is based on their work. No small wonder that they found the same.
Another error is the following:
The Sun is the source of energy that heats
Earth. Besides direct solar heating of the ground,
there is also indirect longwave (LW) warming
arising from the thermal radiation that is emitted
by the ground, then absorbed locally within the
atmosphere, from which it is re-emitted in both
upward and downward directions, further heating
the ground and maintaining the temperature gradient
in the atmosphere. This radiative interaction
is the greenhouse effect, which was first discovered
by Joseph Fourier in 1824 (2), experimentally
verified by John Tyndall in 1863 (3),
and quantified by Svante Arrhenius in 1896 (4).
This nonsense is based on backradiation of a solid black body. CO2 is a gas, not abody. It loses its absorbed energy by vibration, rotation and movement. Not by acting as a solid mass. It is not. The range of its emissions are limited by the pressure at which it is.
The entire paper is BS. I sincerely ask myself why I used to have such high esteem of papers published in Science?
And I did never smoke pot.
Anything that may be construed by serious minds [sorry, Pamela] as “a control knob” for a process must necessarily act comprehensibly in advance of changes in that process. This fundamental causal requirement is what makes CO2 a non-starter as a climate regulator. Whether it’s ice core proxies at millennial scales or instrument measurements at monthly or yearly scales, changes in CO2 concentrations demonstrably LAG the temperature signal in all real-world observations. We can argue until we’re blue in the face about what unvalidated theories say about the expected “climate sensitivity,” but there’s no in situ data demonstrating that modern-era changes in CO2 concentrations have any coherent effect on global temperatures. The two metrics are either virtually incoherent, or CO2 consistently follows T as a product of oceanic outgassing.
P.S. to Pamela: Having previously noted your fondness for wine, dare I ask whether Knob Creek is one of your favorites?
“Andrew Lacis and colleagues conducted a set of idealized climate model experiments in which various greenhouse gases were added to or subtracted from the atmosphere”
David Springer and collegues conducted a set of idealized NASA management experiments. After a series of five colder than normal North American winters and springs with late killer frosts Gavin Schmidt and James Hansen were asked to resign.
George E. Smith says:
October 15, 2010 at 12:12 pm
So what’s up with the term ultraviolet light? Or infrared light?
In fact George, light isn’t just what can be seen by the naked eye. What can be seen by the naked eye is called visible light.
George E. Smith;
in response to Gareth says
Gareth you are right; it is not that difficult experiment to do. As far as I know, it has NEVER been done in public so we could all watch. People have certainly tried to do it in public; but they have ALL made the same mistake that you just made:>>
The experiment in fact has been done, documented, and published. There was no mistake made in terms of using a simple light source, the researcher is quite detailed in terms of the specific IR frequencies used, how they were generated and measured as well as document the manner in which the artificial atmosphere was created right down to the water vapour. It is a pretty easy read and the conclusions easy to understand. There is much criticism of this paper in that there are matters in the real atmosphere that this experiment does not mimic, the change in water vapour levels with altitude for one example, but in terms of the experiment Gareth describes, it has in fact been done. No one has ever debunked it, all the criticism is in regard to what happens in a real atmosphere versus a closed cylinder:
http://www.john-daly.com/artifact.htm
Mike;
The amount of CO2 in our atmosphere is 390 ppm.
Of that amount, we humans are responsible for about 5%.>>
You begin with this assumption and the balance of your math is predicated upon it. In all things climate (or any science) it depends on whose numbers you believe are credible. In general however, the discussion of gobal warming refers to background or natural levels of CO2 as being 280 PPM with current levels at 390 PPM. So for starters the argument is based on a 30% to 40% increase from human emissions, not 5%.
Secondly, calculating the percentage of the atmosphere that is man made CO2 and concluding that it is too small to be significant is not valid. That would be like claiming that visible light goes through a triple pane glass window 3 cm thick, so a coat of paint 1 mm thick couldn’t possibly stop it. You have to dig deeper into the physics, and it is of course far more complicated that just stopping it or not.
That said, in my mind the real issue is that once you get past all the details of the physics and how CO2 potentially contains infrared radiance, the calculations boil down to two issues. The first is that CO2’s effects are logarithmic. If you have a pair of sun glasses that stop 50% of the light, and put another identical pair in front of them, do they stop 100% of the light? Of course not. The first pair blocks 50% and the second pair blocks 50% of what is left, so 25% gets through. Put another pair in the series and you are down to 12.5%. CO2 is precisely the same, which brings us to the second issue which is sensitivity. How much does the first pair of sunglasses (280 PPM of CO2) raise the temperature? Let’s say it is 1 degree. To get a two degree rise, we would need 560 PPM. To get a 3 degree rise, we would need 1,120 PPM. Here is the real place where global scarum theory falls apart. Based on the last century or so, sensitivity is well under 1 degree per doubling. So… for CO2 to increase global temperatures by 2 degrees over natural background levels of 280 PPM, we would have to burn about 10 times as much fossil fuel as we are right now annually, and we would have to do it for a few centuries.
If you understood all that, it isn’t hard to verify. Then you’ll be ready for a discussion of feedback loops…
A. Lacis
Your modeling study appears to be well researched and executed – much of the criticism here is no doubt unfair. It might even be a reasonable characterisation of the effect of atmospheric CO2 on climate heat – under one condition: that the planet under study is devoid of multi-cellular life.
However earth is covered by multicellular life, and this is what clouds the picture somewhat. It brings a huge step-up in complexity and even chaos to the dynamics of atmosphere and climate. An arid lifeless planet might possibly have an atmosphere that could be reasonably approximated by computer models based on radiative balance and some assumptions about convection. But life changes everything.
A paper by Frank et al 2006 (Leif Svalgaard posted a link to this paper some months ago) summarised the history of all life on earth on a billion year timescale in terms of a “corridor” of survivability, in between the planet’s fiery formation and its ultimate heat sterilisation by an aging and expanding red giant sun.
http://www.biogeosciences.net/3/85/2006/bg-3-85-2006.pdf
Essentially we multicellulars have around a billion years left, bacteria perhaps 1.7 billion. The paper includes timelines of global temperature and of atmospheric CO2, as well as estimates of life biomass in the categories of prokaryotes, single and multicelled eukaryotes. One very striking feature of these time-lines is an abrupt transition at -0.5 billion years (Byrs) shown in figures 2 and 6. This is the Cambrian explosion: multicellular life appeared and rapidly expanded, and both temperature and CO2 decreased sharply.
Why did temperature and CO2 both plunge down together – was it global warming in reverse? Some excellent and detailed research by Beerling and others supplies a probable answer. Plants spread over land from the Silurian to the Carboniferous, and steadily became more efficient in sequestering CO2 from the air by photosynthesis, with evolution of trees and broader more efficient leaves. As if prepared by a cosmic gardener, the Sturtian and Marinoan/Varanger ice ages between 750 and 635 MYa had deposited on the continents “weathered silicates”, the precursors of soil; the end-Ordovician ice age contributed further (these ice ages may have been of the “snowball earth” variety). Plants and trees mixed humates into these silicates to give our soil covered land surface and a profound change in climate. Water was retained on land in much larger quantities and water precipitation and the hydrological cycle stepped up sharply in intensity.
The sharp fall in CO2 in the early Phanerozoic resulted from a period of coupled positive feedback between evolution of photosynthesising plants and especially trees and broader leaves, sucking more of the (then) abundant CO2 from the air and, as the gas diminished in consequence, favouring more and more efficient CO2 extraction. This is described by Beerling and Berner 2005:
http://www.pnas.org/content/102/5/1302.full.pdf+html
The very weak or non-existent correlation between temperature and CO2 on timescales short of the BYr magnitude – including some further research by Beerling – show that the most likely reason for the fall in temperatures following the Cambrian explosion was the expanded hydrological cycle and clouds – not CO2. CO2 fell due to the evolution of trees and more efficient photosynthesis by plants in general.
The scientific rebuttals off Gore’s “Inconvenient truth” pointed to the ice core data of the last MYrs or so which reveal that changes in atmospheric CO2 follow temperature swings rather than leading them – thus making CO2 driving of temperature very unlikely. Beerling and Royer in their 2002 paper “Reading a CO2 signal from fossil stomata” add important detail to this:
http://www.palaeobiology.org.uk/publications/nph153_387.pdf
The introduction of this paper says this:
Coupled with isotopic measurements on the ice, analyses of ice cores have shown that CO2 oscillated between 180 and 280 ppm in 100 000 years cycles, in phase with changes in temperature (Petit et al., 1999; Shackleton, 2000). An interesting feature of the high resolution analyses of the millennial palaeoclimate records is that a change in air temperature can apparently occur quite rapidly without changes in CO2 , whereas the converse has not yet been seen to occur (Falkowski et al., 2000).
So temperature can change independent of CO2, but CO2 clings to the skirts of temperature and follows it.
So multicellular life brought water and clouds and reduced CO2, and immeasurably complexity, even chaos, to earth’s climate. In the orderly and sterile pre-Cambrian world CO2 might possibly have been a temperature driver (although the Huronian ice age more than 2 BYa was not deterred by almost 50% atmospheric CO2). However in the present more chaotic regime the hydrological cycle and clouds have become the dominant drivers and marginalised the effect of CO2, possibly to almost zero. We learned recently that cloud formations themselves follow the laws of nonequilibrium dynamic chaos, react to each-other spontaneously and display Lyapunov stability:
http://wattsupwiththat.com/2010/08/12/cloud-cellular-communication/
Thus the dispute between climate AGW orthodoxy and climate skepticism is one between order and chaos. This is one of the things I like most about it – since the resolution of this conflict will elevate the understanding and study of dynamic chaos and nonequilibrium pattern from the margins of science toward the mainstream.
Finally, returning to the biosphere’s gloomy timeline for extinction in Frank et al 2006 paper, figure 6 shows something important. What is it that will deal the coup do grace of final extinction to all life on earth? Getting too hot? No – starvation of CO2.
Is it a coincidence that NASA appears to be funding an army of climate change advocates? http://disccrs.org/ Is this new funding?
Plus, when you can’t dazzle them with Science, try more propaganda from your friends in media, the arts, and even religion. http://www.cbbulletin.com/399483.aspx
You see, it is their moral obligation. http://www.fw.msu.edu/documents/MoralObligationsOfScientists.pdf
“When scientists reject advocacy as a principle, they reject a
fundamental aspect of their citizenship. Because of the nature and
depth of their knowledge, they have a special responsibility. It is a
perversion of democracy to muffle the voice of the most
knowledgeable among us and consequently amplify the voice of
those with the greatest ignorance.”
Science, Media, Education, a perversion of religion, Big Energy and the Government. What a glorious Monster.
Re: Mike and davidmhoffer and the likelihood of AGW through anthropogenic CO2.
Both of you are responding to what I call the Reasonable Man Hypothesis: that a reasonably educated self-thinker (of all genders and preferences) can look at a complicated scenario with multiple parameters, each with its own error bar or uncertainty, and come to a “reasonable” conclusion if the output of the scenario is worth getting excited about. The IPCC supported CAGW seems to me to fail this test. We know that each parameter of input has its uncertainties, but the output is said to be quite certain. Yes, the math is such-and-such, and the computer models predict/project such-and-such. But somewhere in the process we have lost the uncertainties that build one on the other. We also know that the process is biased towards the negative side of the data that is collected, the negative side of data manipulation and the negative side of trend predictions/projections: 1) deselection of stations, non-incorporation of satellite data, 2) refusal to accept significant UHIE, extrapolation and interpolation of data in areas already considered anomalously high, systematic reductions in historic and increases in modern temperatures, 3) non-consideration of negative feedback of clouds as temperature rises, immediate extension of short-term trends of long-term cycles (when possibly catastrophic only), including using bad weather yesterday as a harbinger of bad climate in 100 years. Of course I could continue this with the one-sided MSM criticism of skeptical viewpoints and portrayal of potential calamaties as certainties. But, you know, beating a dead horse and all that.
The Reasonable Man Hypothesis here says that the person thinking each of these thoughts and noting that each step leads towards one place and away from another place would be able to “abjure, curse and detest” what he is told to believe by authorities with a vested interest in the outcome . This is, as indicated by the quote, the reverse of what Galileo was told to do by the Vatican vis-a-vis heliocentricism. The Reasonable Man orders himself to listen to his own interpretation, as he is qualified to be suspicious of what he is told, if not even to make his own determination. As Galileo is said to have muttered after he recanted on fear of death, “Still, it moves!”, the Reasonable Man would say “It doesn’t make sense,” after reading AR4 or watching An Inconvenient Truth.
Reasonableness should trump a litany of “facts”, calculations and arguments. Reasonableness in the human spirit is what stopped us from leaving the cave on hearing growling noises even though the attractive dude smiling at our girlfriend said it was just the wind howling through the trees.
On reflection I contradicted myself a bit in the last post:
The very weak or non-existent correlation between temperature and CO2 on timescales short of the BYr magnitude …
Beerling and Royer 2002:
Coupled with isotopic measurements on the ice, analyses of ice cores have shown that CO2 oscillated between 180 and 280 ppm in 100 000 years cycles, in phase with changes in temperature (Petit et al., 1999; Shackleton, 2000). An interesting feature of the high resolution analyses of the millennial palaeoclimate records is that a change in air temperature can apparently occur quite rapidly without changes in CO2 , whereas the converse has not yet been seen to occur (Falkowski et al., 2000).
So temperature can change independent of CO2, but CO2 clings to the skirts of temperature and follows it.
“No correlation on <BYa timescales … but CO2 following temperature, i.e. correlation".
To clarify, on scales of tens and hundreds of millions of years, the CO2 – temperature correlation is very weak indeed. However on shorter, multi-millenial scales, there is a significant correlation – the question is if temperature or CO2 leads – evidence suggests the former.
If "rapid" changes in temp can be unaccompanied by CO2 changes, while (presumably slower) changes in CO2 are associated with temperature change, the difference could be the ocean. Slower changes in temperature are accompanied by ocean temperature change and CO2 in air is controlled by the changing solubility of CO2 in seawater at changing temperatures. The "rapid" temperature changes with no CO2 change could be ones unaccompanied by ocean temperature change – at least in the short term.
There is no correlation between a rise in CO2 and a subsequent rise in temperature.
How many times does this non-correlation have to be pointed out?
OTOH, there is a clear correlation between a rise in temperature and a subsequent rise in CO2, both at short term and long term time scales.
The more we learn, the clearer it is that rising CO2 is a function of rising temperature, not vice-versa. Of course, those scientists who have hitched their careers to the CO2=CAGW bandwagon must still argue against the empirical evidence, because they cannot reverse themselves and publicly admit that rather than CO2 controlling the climate, it is temperature that controls atmospheric CO2 levels.
If they admitted the truth of the CO2/temperature relationship, this hockey stick would turn down faster than you could say “rajendrapachauri“.
Smokey says:
October 16, 2010 at 3:57 pm
We re in agreement, the CO2 time lag strongly indicates ocean temperature forcing of atmospheric CO2. A time lag in either direction between two similar wavetrains does not necessarily destroy mathematical correlation between them – but as we know, correlation and causation are different things.
CO2 is a fine tuning control. Older folks here will recall when televisions had a central knob that changed changed channels and a ring surrounding it that fine-tuned the selected channel. The channel changer in this case is water in all its phases.
It is clear from looking at the really long term data (500 million years) that there is NO correlation between CO2 and temperature. There DOES appear to be a correlation between temperature and cosmic rays. And, since cosmic rays may have a strong effect on cloud cover, that makes sense. I have a graph here. http://howcanpeoplebesostupid.com/?p=3148
davidmhoffer…Thank you for the quick explanation of the physics of CO2…
“In general however, the discussion of gobal warming refers to background or natural levels of CO2 as being 280 PPM with current levels at 390 PPM. So for starters the argument is based on a 30% to 40% increase from human emissions, not 5%.”
I have been told that the CO2 levels pre-industrial revolution were about 280 ppm. Today it is 390 ppm. therefore the entire increase (39%) is man-caused…which is a leap. But getting back to the math…are the figures I cited accurate? In addition, isn’t the physics of CO2 limited by the scarce amount of CO2 in the atmosphere? This you alluded to here…”Based on the last century or so, sensitivity is well under 1 degree per doubling. So… for CO2 to increase global temperatures by 2 degrees over natural background levels of 280 PPM, we would have to burn about 10 times as much fossil fuel as we are right now annually, and we would have to do it for a few centuries.”
Which leads me to Doug Proctor and his Reasonable Man Hypothesis. The more I look at the math, coupled with your lesson on the physics of CO2 the more proposterous the AGW hypothesis appears to me. It does not ring true.
Mike;
But getting back to the math…are the figures I cited accurate?>>
In terms of figures you cited they are not so much “accurate” as “close enough” for the purposes of this discussion. Your conclusion that the amount of man made CO2 is too small a percentage to be serious however isn’t fair in my mind. It is more complicated than that.
Warming theory exists in two parts. The first part is that the earth emitts photons in the IR spectrum. These are readily absorbed by CO2 molecules which will then re-emitt them in a random direction. As a result, any given photon emitted from earth’s surface has a percentage chance of being absorbed by a CO2 molecules, and when re-emitted it has a percentage chance of being re-emitted back toward earth. While at first blush it would seem that with such a small concentration in the atmosphere most photons would never encounter a CO2 molecule and would travel straight out to space, in reality there are so many “layers” of CO2 molecules along the way that the chance of a photon hitting one is pretty high. Each CO2 molecule can absorb and emitt all day (and night) without pause, so the question is not what is the percentage of the atmosphere that is CO2, the question is what is the increased percent chance that a photon will be absorbed and re-emitted back to earth.
Part 2 regards feedback. Again the classic theory is that warm air can hold a lot more moisture than cold air. A 10 degree rise in temperature equates (if memory serves me correctly) to the capacity of air to double in terms of the amount of moisture it can hold. Since water vapour is itself a greenhouse gas, theory has it that a small rise in temperature must result in higher levels lf water vapour, and the greenhouse effect of the additional water vapour is a positive feedback that must be added to CO2’s effects.
In practice of course it is not so simple. For starters, since CO2 and water vapour absorb IR in roughly the same spectrum, they are competitors for any given IR photon. If their concentrations were the same, CO2 would absorb about 3 times as many photons as water vapour, but the concentrations are not the same. At sea level at the equator, water vapour is in the 2% to 3% range. So even though CO2 is a more efficient absorber, water molecules outnumber them hundreds or thousands to one, making their effect negligible. As you rise in altitude however, temperatures fall and so does the amount of water vapour that the air can hold. Hence the effect of CO2 should be higher at high altitudes because it is a larger percentage compared to water vapour. In theory, the warming we would expect to see from CO2 should be most prevalent at certain levels in the troposphere, in practice that “hot spot” doesn’t seem to exist.
The conundrum has not been resolved, but is most likely related to an under estimation of negative feedbacks. Clouds are composed not of water vapour, but of ice crystals which were formed from water vapour. The coldest days of winter are accompanied by a clear blue sky with nary a cloud to be seen. But the coldest (OK, least hot) days of summer are those with high cloud cover. Before the purists start howling that I am over simplifying it, clouds can be either negative or positive depending on a variety of factors, the point being that increased water vapour means changes in cloud cover, not all of which will be positive feedback.
In addition, should a photon rising from the earth be intercepted by a CO2 molecule at high altitude, the chance that it would have been intercepted at a still higher altitude by water vapour or some other greenhouse goes away, cooling the higher altitude and reducing the levels of water vapour there. The same thinking applies to that photon that has been absorbed and re-emitted back toward earth. If indeed water vapour has increased significantly, then the chance that a downward travelling photon will be absorbed by water vapour before it strikes earth surface and is re-emitted, potentially back toward outer space, also increases and so is another negative feedback.
So… while I agree with your ultimate conclusion, the effects are minor once all the positives and negatives are added up, I think it a mistake to simply dismiss CO2 based on how small a percentage of the atmosphere it is.