NOTE: This has been running two weeks at the top of WUWT, discussion has slowed, so I’m placing it back in regular que. – Anthony
UPDATES:
Statistician William Briggs weighs in here
Eduardo Zorita weighs in here
Anonymous blogger “Deep Climate” weighs in with what he/she calls a “deeply flawed study” here
After a week of being “preoccupied” Real Climate finally breaks radio silence here. It appears to be a prelude to a dismissal with a “wave of the hand”
Supplementary Info now available: All data and code used in this paper are available at the Annals of Applied Statistics supplementary materials website:
http://www.imstat.org/aoas/supplements/default.htm
=========================================
Sticky Wicket – phrase, meaning: “A difficult situation”.
Oh, my. There is a new and important study on temperature proxy reconstructions (McShane and Wyner 2010) submitted into the Annals of Applied Statistics and is listed to be published in the next issue. According to Steve McIntyre, this is one of the “top statistical journals”. This paper is a direct and serious rebuttal to the proxy reconstructions of Mann. It seems watertight on the surface, because instead of trying to attack the proxy data quality issues, they assumed the proxy data was accurate for their purpose, then created a bayesian backcast method. Then, using the proxy data, they demonstrate it fails to reproduce the sharp 20th century uptick.
Now, there’s a new look to the familiar “hockey stick”.
Before:
After:
Not only are the results stunning, but the paper is highly readable, written in a sensible style that most laymen can absorb, even if they don’t understand some of the finer points of bayesian and loess filters, or principal components. Not only that, this paper is a confirmation of McIntyre and McKitrick’s work, with a strong nod to Wegman. I highly recommend reading this and distributing this story widely.
Here’s the submitted paper:
(PDF, 2.5 MB. Backup download available here: McShane and Wyner 2010 )
It states in its abstract:
We find that the proxies do not predict temperature significantly better than random series generated independently of temperature. Furthermore, various model specifications that perform similarly at predicting temperature produce extremely different historical backcasts. Finally, the proxies seem unable to forecast the high levels of and sharp run-up in temperature in the 1990s either in-sample or from contiguous holdout blocks, thus casting doubt on their ability to predict such phenomena if in fact they occurred several hundred years ago.
Here are some excerpts from the paper (emphasis in paragraphs mine):
This one shows that M&M hit the mark, because it is independent validation:
In other words, our model performs better when using highly autocorrelated
noise rather than proxies to ”predict” temperature. The real proxies are less predictive than our ”fake” data. While the Lasso generated reconstructions using the proxies are highly statistically significant compared to simple null models, they do not achieve statistical significance against sophisticated null models.
We are not the first to observe this effect. It was shown, in McIntyre
and McKitrick (2005a,c), that random sequences with complex local dependence
structures can predict temperatures. Their approach has been
roundly dismissed in the climate science literature:
To generate ”random” noise series, MM05c apply the full autoregressive structure of the real world proxy series. In this way, they in fact train their stochastic engine with significant (if not dominant) low frequency climate signal rather than purely non-climatic noise and its persistence. [Emphasis in original]
Ammann and Wahl (2007)
…
On the power of the proxy data to actually detect climate change:
This is disturbing: if a model cannot predict the occurrence of a sharp run-up in an out-of-sample block which is contiguous with the insample training set, then it seems highly unlikely that it has power to detect such levels or run-ups in the more distant past. It is even more discouraging when one recalls Figure 15: the model cannot capture the sharp run-up even in-sample. In sum, these results suggest that the ninety-three sequences that comprise the 1,000 year old proxy record simply lack power to detect a sharp increase in temperature. See Footnote 12
Footnote 12:
On the other hand, perhaps our model is unable to detect the high level of and sharp run-up in recent temperatures because anthropogenic factors have, for example, caused a regime change in the relation between temperatures and proxies. While this is certainly a consistent line of reasoning, it is also fraught with peril for, once one admits the possibility of regime changes in the instrumental period, it raises the question of whether such changes exist elsewhere over the past 1,000 years. Furthermore, it implies that up to half of the already short instrumental record is corrupted by anthropogenic factors, thus undermining paleoclimatology as a statistical enterprise.
…
We plot the in-sample portion of this backcast (1850-1998 AD) in Figure 15. Not surprisingly, the model tracks CRU reasonably well because it is in-sample. However, despite the fact that the backcast is both in-sample and initialized with the high true temperatures from 1999 AD and 2000 AD, it still cannot capture either the high level of or the sharp run-up in temperatures of the 1990s. It is substantially biased low. That the model cannot capture run-up even in-sample does not portend well for its ability
to capture similar levels and run-ups if they exist out-of-sample.
…
Conclusion.
Research on multi-proxy temperature reconstructions of the earth’s temperature is now entering its second decade. While the literature is large, there has been very little collaboration with universitylevel, professional statisticians (Wegman et al., 2006; Wegman, 2006). Our paper is an effort to apply some modern statistical methods to these problems. While our results agree with the climate scientists findings in some
respects, our methods of estimating model uncertainty and accuracy are in sharp disagreement.
On the one hand, we conclude unequivocally that the evidence for a ”long-handled” hockey stick (where the shaft of the hockey stick extends to the year 1000 AD) is lacking in the data. The fundamental problem is that there is a limited amount of proxy data which dates back to 1000 AD; what is available is weakly predictive of global annual temperature. Our backcasting methods, which track quite closely the methods applied most recently in Mann (2008) to the same data, are unable to catch the sharp run up in temperatures recorded in the 1990s, even in-sample.
As can be seen in Figure 15, our estimate of the run up in temperature in the 1990s has
a much smaller slope than the actual temperature series. Furthermore, the lower frame of Figure 18 clearly reveals that the proxy model is not at all able to track the high gradient segment. Consequently, the long flat handle of the hockey stick is best understood to be a feature of regression and less a reflection of our knowledge of the truth. Nevertheless, the temperatures of the last few decades have been relatively warm compared to many of the thousand year temperature curves sampled from the posterior distribution of our model.
Our main contribution is our efforts to seriously grapple with the uncertainty involved in paleoclimatological reconstructions. Regression of high dimensional time series is always a complex problem with many traps. In our case, the particular challenges include (i) a short sequence of training data, (ii) more predictors than observations, (iii) a very weak signal, and (iv) response and predictor variables which are both strongly autocorrelated.
The final point is particularly troublesome: since the data is not easily modeled by a simple autoregressive process it follows that the number of truly independent observations (i.e., the effective sample size) may be just too small for accurate reconstruction.
Climate scientists have greatly underestimated the uncertainty of proxy based reconstructions and hence have been overconfident in their models. We have shown that time dependence in the temperature series is sufficiently strong to permit complex sequences of random numbers to forecast out-of-sample reasonably well fairly frequently (see, for example, Figure 9). Furthermore, even proxy based models with approximately the same amount of reconstructive skill (Figures 11,12, and 13), produce strikingly dissimilar historical backcasts: some of these look like hockey sticks but most do not (Figure 14).
Natural climate variability is not well understood and is probably quite large. It is not clear that the proxies currently used to predict temperature are even predictive of it at the scale of several decades let alone over many centuries. Nonetheless, paleoclimatoligical reconstructions constitute only one source of evidence in the AGW debate. Our work stands entirely on the shoulders of those environmental scientists who labored untold years to assemble the vast network of natural proxies. Although we assume the reliability of their data for our purposes here, there still remains a considerable number of outstanding questions that can only be answered with a free and open inquiry and a great deal of replication.
===============================================================
Commenters on WUWT report that Tamino and Romm are deleting comments even mentioning this paper on their blog comment forum. Their refusal to even acknowledge it tells you it has squarely hit the target, and the fat lady has sung – loudly.
(h/t to WUWT reader “thechuckr”)
Hahahahahahah. Exactly
Mike Roddy says:
August 15, 2010 at 8:04 pm
“Mann’s hockey stick and the blogosphere (not scientific) controversy that came from it was studied by NAS, or the National Academy of Sciences. His work was vindicated in all respects, and was shown to be robust.”
I fear that you missed the point to the parable of the “Emperor’s New Clothes”. Get ready for more “disciplined reviewed literature” to pile onto this robust abomination of statistical nonsense. M&M, Wegman, the blogosphere and now M&W, you have to realize that you have been worshiping a turnip. I am not saying that there is not room for improvement on the “Anthropogenic Side”, us skeptics find *CAGW* is * FUNDAMENTALLY* flawed for only a political reason.
Just because O.J. Simpson was found innocent in the criminal case, does that force you to understand that he did not kill his ex-wife? That is why politics need to stay out of science.
Mike Roddy, your link does not support your assertion.
I’ve read it before, I’ve re-read it now. It does not vindicate his hockey stick; at best it shows there is no evidence he intentionally falsified research. Many people here would probably disagree with the the whitewashed conclusion that his mistakes were unintentional, but whatever.
To reference that investigation as vindication of his results is insulting. I can’t figure out what your purpose was. Did you mean to link something else?
“Climate scientists have greatly underestimated the uncertainty of proxy based reconstructions and hence have been overconfident in their models. ”
Why does uncertainty of global temperatures as deduced from proxies necessarily mean there is no AGW problem? Couldn’t it also mean that the problem is even worse than predicted? Would it not be wise to prepare for the worst case scenarios?
I would hope the building I am sitting in right now was not desigened assuming every day would be 60 degrees with no wind or precipitation, but was designed with consideration for weather cases that are possible in this region even though the engineer might not be “certain” they would ever happen.
The findings were Mann was not right, but also not pathological. One of those findings was a courtesy. Can you spot it?
moondog,
Pascal’s gamble is a religious argument, made by the faithful. It is not a principal upon which to build global energy policy.
Mike Roddy: The authors of the 20- odd studies that confirmed Mann’s data are not really interested in what professional statisticians and mathematicians are saying about it.
I’m confused. Which side are you arguing here? You write this as if you think it is a good thing that a bunch of paleontologists are (mis)using statistical techniques like PCA and don’t care what the trained professionals think. Am I missing something?
moondog says:
August 15, 2010 at 10:01 pm
Why does uncertainty of global temperatures as deduced from proxies necessarily mean there is no AGW problem? Couldn’t it also mean that the problem is even worse than predicted? Would it not be wise to prepare for the worst case scenarios?
Here’s the way I see it. We may have a problem, we may not. I would prefer to have unbiased scientists study the question. The current cabal of “climate scientists” have repeatedly told us the debate is over, the science is settled. Well, I guess they were wrong. That makes them either foolish or dishonest, you may choose. As a US taxpayer, paying the salary, benefits and potential retirements for these so called “scientists”, I’ve seen enough of this obvious scam. I’d like to see people fired over this. Let’s get some real honest scientists that thrive on debate and fully understand that science is never settled. If a new crop of quality scientists who are unafraid to share their data and methods can make a strong case that we have a problem, I’m perfectly willing to listen and do my part to mitigate the problem. The Gore, Mann, Jones, Schmidt team is a bust. Time for some new blood.
Pascal’s gamble is a religious argument, made by the faithful. It is not a principal upon which to build global energy policy.
More to the point, it is a case where taking precaution comes at no cost and where said precaution is guaranteed effective if the danger proves real.
In the case of CO2 “solutions”, the cost is intolerable and the efficacy dubious.
For the 1 or 2 here who seem to be in dobt over the Medieval Warm Period
Papers ranked in 3 levels, one of which allows direct comparision of MWP temps
to todays. Also Shows rather nicely that MWP was global in nature.
http://www.co2science.org/data/mwp/mwpp.php
Hope this helps you come to the realization that climate change IS real, but very
little to do with mankind…
cheerio..
Jim
moondog says:
August 15, 2010 at 10:01 pm
“Why does uncertainty of global temperatures as deduced from proxies necessarily mean there is no AGW problem? Couldn’t it also mean that the problem is even worse than predicted? Would it not be wise to prepare for the worst case scenarios?”
It doesn’t mean there isn’t an AGW problem. It means the people proclaiming the problem were amateurish(to be charitable). Yes, it could be worse than we thought, but that’s not likely seeing that the climatologists were overstating their levels of certainty, as seen in this study and others.
Still, it doesn’t hurt to be prudently cautious. By that, I mean to ensure the precautionary measures don’t do additional and probably more harm than the “supposed” potential harm.
What we are seeing today isn’t prudent caution.
A question for you: What is the most deadly, socially disruptive, health damaging, ecologically destroying, violence causing, economically burdensome, liberty taxing human condition ever known to man throughout written history?…………………………. Give up?
The answer is poverty.
Care to tally what our “preparation” has done for us so far? Moondog, the proposed cures are worse than any real or imagined threat a little warming could do to us.
Henry@ur momisuglyEvan Jones
Evan, on what (actual) measurements do you base your believe that CO2 is a greenhouse gas i.e that its warming properties are greater than its cooling properties?
Evan, you say:
So far, not on a lot. Too many unknown. There is behavior under lab conditions. And there has been some measurable warming. But I am guessing the trend is exaggerated by a factor of two between spurious adjustments and various site biases (UHI, microsite, TOBS, what have you).
Then there is natural recovery from the LIA and non-CO2 anthropogenic issues such as land use and particulates (i.e., “dirty snow”).
Not to mention the mysteries of how the atmosphere behaves in practice and all the oceanic and interactive variables (clouds, pressure variables, what have you).
To say nothing of radiation, which is what CO2 GH theory is all about.
Then there are all the unknown factors. Since we don’t know them, we can’t list them.
Between all that, there is still room for CO2, though not a heck of a lot. Possibly the raw effect is real, but damped down by negative feedback.
Thank goodness we have microwave proxies for lower troposphere or we’d not only be shooting in the dark, but aiming at a raindrop while standing on a revolving platform.
Henry @ur momisugly Evan again, just to let you know:
I posted this question to the university of Cape Town here (hoping to get an answer of the state of research on CO2 in South Africa) :
Dear Prof. Shillington
I heard you on the radio this afternoon and it seemed to me that you are also getting to a point where you are starting to get doubts about the influence of CO2 on global warming. Please bear with me to hear my story, and see if you can perhaps provide an answer to the questions that I have.
A few months before Climategate broke, I started my own investigations to see if my carbon footprint (CO2) really causes global warming, as claimed. To start off with, I found Svante Arrhenius’ formula completely wrong and since then I could not find any correctly conducted experiments (tests & measurements) that would somehow prove to me that the warming properties of CO2 (by trapping earth’s radiation between the wavelengths 14-15 um) are greater than its cooling properties (by deflecting sunlight at various wavelengths between 0 – 5 um). Even more disconcerting to me was finding that pupils at school and college are shown experiments with 100% carbon dioxide (representing earth’s atmosphere of only 0.04% or 380 ppms CO2!) and a light bulb as an energy source (representing the sun!). Obviously such crude experimentation can only lead to incorrect results and completely incorrect conclusions…e.g. what about the IR and near IR absorptions of CO2 and the UV absorptions of CO2 that have only been discovered recently and that also deflect sunlight?
I also found untruths in Al Gores story (An Inconvenient Truth). A lot of CO2 is dissolved in cold water and comes out when the oceans get warmer. Any chemistry student knows that the first smoke from the (warmed) water in a kettle is the CO2 being released. So, quite a number of scientists have reported that the increases of CO2 in the atmosphere in the past lagged the warming periods by quite a few hundred years… Cause and effect, get it? Smoking causes cancer but cancer does not cause smoking. But Al made it look from the past that our CO2 output must be the cause of global warming.
Just to put the carbon dioxide content of the atmosphere into the right perspective: it has increased by about 0.01% in the past 50 years from ca. 0.03% to 0.04%. This compares with an average of about 1 % for water vapor in the air. Note that most scientists agree that water vapor is a very strong green house gas, and a much stronger green house gas than carbon dioxide… (if indeed carbon dioxide is a green house gas, which, like I said before, has yet to be proven to me). It is also logical for me to suspect that as a result of human activities relating to burning, bathing, cooking, boiling, countless cooling processes (including that for nuclear energy), erection of dams and shallow pools, etc. etc. a lot more water vapor than carbon dioxide is put up in the air. (sunshine on shallow water causes a lot of water vapor!)
The paper that confirmed to me that CO2 is (also) cooling the atmosphere by re-radiating sunshine is this one:
http://www.iop.org/EJ/article/0004-637X/644/1/551/64090.web.pdf?request-id=76e1a830-4451-4c80-aa58-4728c1d646ec
they measured this radiation as it bounced back to earth from the moon. So the direction of the radiation was:sun-earth-moon-earth. Follow the green line in fig. 6, bottom. Note that it already starts at 1.2 um, then one peak at 1.4 um, then various peaks at 1.6 um and 3 big peaks at 2 um.
This paper here shows that there is absorption of CO2 at between 0.21 and 0.19 um (close to 202 nm):
http://www.nat.vu.nl/en/sec/atom/Publications/pdf/DUV-CO2.pdf
There are other papers that I can look for again that will show that there are also absorptions of CO2 at between 0.18 and 0.135 um and between 0.125 and 0.12 um.
We already know from the normal IR spectra that CO2 has big absorption between 4 and 5 um.
So, to sum it up, we know that CO2 has absorption in the 14-15 um range causing some warming (by re-radiating earthshine) but as shown and proved above it also has a number of absorptions in the 0-5 um range causing cooling (by re-radiating sunshine). This cooling happens at all levels where the sunshine hits on the carbon dioxide same as the earthshine. The way from the bottom to the top is the same as from top to the bottom. So, my question is: how much cooling and how much warming is caused by the CO2? How was the experiment done to determine this and where are the test results? (I am afraid that simple heat retention testing might not work here, we have to use real sunshine and real earthshine to determine the effect in W/m3 [0.03%- 0.06%]CO2/m2/24hours). I am also doubtful of just doing analysis (determining surface areas) of the spectral data, as some of the UV absorptions of CO2 have only been discovered recently and I think the actual heat caused by the sun’s IR at 4-5 maybe underestimated, e.g. the amount of radiation of the sun between 4 and 5 maybe small but how many Watts does it cause? Here in Africa you can not stand in the sun for longer that 10 minutes, just because of the heat of the sun on your skin.
Anyway, with so much at stake, surely, someone actually has to come up with some empirical testing?
If this research has not been done, why dont we just sue the oil companies to do this?? It is their product afterall.
I am going to state it here quite categorically again that if no one has got these results, then how do we know for sure that CO2 is a greenhouse gas? Maybe the cooling properties are equal to the warming properties?
I have also been thinking of the ozone concentration in the air: Assuming that its cooling properties are higher than its warming properties (did anyone test that?), then lower concentrations, as in the past, before CFC’s were banned, can be a cause for global warming; increasing levels, as noted in the past 10 years can be a cause of global cooling?
So the net effect of the increases in CO2 and ozone is close to zero or even cooling?
(I have no financial interest in any of this, I just started my investigations because I felt a bit guilty about driving my car. I do think that if this research has not been done we should still do it, I think it is important?)
Mann’s modelling was the cornerstone of the whole alarm over global warming and all subsequent modelling was based on the same techniques and data sets. Hence the Email exchanges with Jones that ensured they were singing from the same song sheet.
The only real question here is: Has this latest paper discredited Mann’s (and therefore most subsequent) models? If so, it is not for the sceptics to prove their case. If you remove the cornerstone from a building, it may appear to stand for a little while but it will fall.
As for arguments that even if the whole alarm over global warming is based on unreliable data we should still go ahead with measures that force the abandonment of fossil fuels: try to tell the Chinese , Indians and other developing nations that their emergence from poverty must be put on hold ‘in case’ false arguments turn out to have accidentally predicted the future.
Evan–
I think we’re on the same page re “opportunity costs”. . . Even the UN started squirming about the cost of corn a couple years ago, re the human opportunity cost of using it for fuel rather than foodstuffs.
An excellent summary about the history of the hockey stick discussion is given here:
http://www.quadrant.org.au/magazine/issue/2010/7-8/the-tree-ring-circus
This thread contains little, if any, actual analysis of the MW2010 paper… is this the best so-called “skeptics” can do/offer? Comical – indeed! I’d appreciate even a token attempt to question the techniques, results, claims/conclusions… you know, a chance to read something other than 300+ comments vilifying Mann, or repeated shouts of “vindication”, or high-fivin/back-slappin. Are there any real skeptics in the house?
richyRich: Did you not even read this article? Did you miss the exact quotes from the paper? What part of “We find that the proxies do not predict temperature significantly better than random series generated independently of temperature” do you not understand?
RE: Mike Roddy: (August 15, 2010 at 8:04 pm) “Mann’s hockey stick and the blogosphere (not scientific) controversy that came from it was studied by NAS, or the National Academy of Sciences. His work was vindicated in all respects, and was shown to be robust.”
The problem here, I believe, is that these are all vindications in name only. These climate scientists appear to have attempted to redefine an established history by selectively ignoring data that did not conform to their beliefs. Perhaps they did this in good faith, believing they were right, but all their work seems to fall apart under the light of critical scrutiny. Most of these supposed ‘vindications’ only seem to be saying that these dedicated scientists cannot be blamed for giving it ‘the old college try.’
[REPLY – Unfortunately, and to their ultimate detriment, they gave it the “new college try”. ~ Evan]
Mike Roddy says:
August 15, 2010 at 8:04 pm
“Mann’s hockey stick and the blogosphere (not scientific) controversy that came from it was studied by NAS, or the National Academy of Sciences. His work was vindicated in all respects, and was shown to be robust.”
This is one of the truly ludicrous falsehoods of the CAGW-mongers. What the head of the NAS panel said (under oath before the congressional committee):
“CHAIRMAN BARTON: Dr. North, do you dispute the conclusions or the methodology of Dr. Wegman’s report?
DR. NORTH: No, we don’t. We don’t disagree with their criticism. In fact, pretty much the same thing is said in our report. But again, just because the claims are made, doesn’t mean they are false”
– from “The Hockey Stick Illusion”, p 255, Andrew Montford.
So Mr. Roddy, what part of Mann’s statistical methods are as phony as his cherry-picke stripbark trees do you not understand? We stand ready here to enlighten you!
Here are two simple Excel charts of that data. The top one shows a linear fit and the bottom an exponential fit. To my 20×20, 70-yeae old eyes, I can’t tell them apart.
http://i924.photobucket.com/albums/ad87/baltwo2/CO2-2.png
Andrew Russell: “richyRich: Did you not even read this article? Did you miss the exact quotes from the paper?”
“Exact quotes” do not amount to critical analysis. They merely demonstrate a facility in copying and pasting. Nor does cheerleading count as critical analysis.
Critical analysis involves taking a claim and subjecting it to scrutiny, while withholding judgement. The technical term is “scepticism”.
“Hockey Sticky Wicket”
Umpire Wegman: You can’t bat with that, it’s been made with the wrong method.
Mann: It’s OK I’ll hold it upside down. It doesn’t matter.
Umpire Wegman: No! Consult some proper bat makers and they’ll show you how it should be done.
Mann: But it’s perfectly robust. According to my PCA analysis, it fits bat making data better than traditional bats do. Look, I’ll show you. No, wait a minute, I won’t show you, but you can take my word for it.
Umpire Wegman: I’ll ask the opposing captain if he’s happy to let you bat with it.
McKintyre: Sure, as long as he doesn’t mind me using these 9 Standard deviation sized stumps his star batsman Briffa brought home from Russia.
Mann: But that’s not cricket!
McKitrick: We told you that long ago.
McKintyre: What shall we bowl with Ross? Apples or oranges?
McKitrick: Foxtail pine cones I think Steve.
Smokey says:
August 14, 2010 at 6:07 pm
Natural climate variability is not well understood and is probably quite large.
We have been saying this here for the past few years.
Well Smokey, this is called ‘projecting your ignorance on the climate professionals’.
[REPLY – Well, turnabout is fair play, wot? ~ Evan]
Not to forget, there was also another recent evaluation:
“Professor David Hand, president of the Royal Statistical Society, said that
a graph shaped like an ice hockey stick that has been used to represent the
recent rise in global temperatures had been compiled using “inappropriate”
methods.”
“Prof Hand said his criticisms should not be seen as invalidating climate
science. He pointed out that although the hockey stick graph – which dates
from a study led by US climate scientist Michael Mann in 1998 – exaggerates
some effects, the underlying data show a clear warming signal.”
Financial Times
—–
Through the link below, you can verify that David Hand (Imperial
College, London) definitely should know his Statistics,
http://www2.imperial.ac.uk/~djhand/
Interesting that he does not come to the conclusion of M&W 2010:
that the whole venture of backcasting is senseless. Clearly, there
is a need for more debate…
Henry Pool
Excellent post.
There have been two recent CO2 heating effect posts on WUWT
One by Tom Vonk saying that (I think) radiation absorption equals radiation emission in the troposphere with little or no thermalisation because of quantum mechanical considerations.
A reply by Jeff ID argues that there is a heating effect and provides a heating effect thought experiment involving a CO2 laser.
My own twopence worth of thoughts is that the CO2 molecules at troposphere temperatures will largely have only translational KE and be quite receptive to 15um and even the smaller chance of 4um ir radiation from Earth surface upwards.
These photons provide a relatively huge addition to the CO2s KE.
For 15um it is over twice the average translational KE of a molecule at that temperature.
For 4um it is over eight times!
Given that molecules experience ten to the power of ten collisions per second this extra energy is shared out by collision with N2 and O2 molecules by the equipartition of energy.
However the emission of 4um and 15um from the atmosphere seems a lot less likely than absorption.
Using Maxwell-Boltzman statistics and the back of an envelope
15um emission is only 5 per hundred absorptions.
4um emission is only 4 per million absorptions.
So if Jeff ID is correct the CO2 thermalisation effect is a temporary local heating in the atmosphere.
If Tom Vonk is correct then there is no effect as there is no thermalisation.