Does CO2 Drive the Earth’s Climate System? Comments on the Latest NASA GISS Paper
by Dr. Roy Spencer
There was a very clever paper published in Science this past week by Lacis, Schmidt, Rind, and Ruedy that uses the GISS climate model (ModelE) in an attempt to prove that carbon dioxide is the main driver of the climate system.
This paper admits that its goal is to counter the oft-quoted claim that water vapor is the main greenhouse gas in our atmosphere. (They provide a 1991 Lindzen reference as an example of that claim).
Through a series of computations and arguments, the authors claim that is actually the CO2, not water vapor, that sustains the warmth of our climate system.
I suspect this paper will result in as many opinions in the skeptic community as there are skeptics giving opinions. But unless one is very careful in reading this paper and knows exactly what the authors are talking about, it is easy to get distracted by superfluous details and miss the main point.
For instance, their table comparing the atmospheres of the Earth, Venus, and Mars does nothing to refute the importance of water vapor to the Earth’s average temperature. While they show that the atmosphere of Mars is very thin, they fail to point out the Martian atmosphere actually has more CO2 than our atmosphere does.
I do not have a problem with the authors’ calculations or their climate model experiment per se. There is not much new here, and their model run produces about what I would expect. It is an interesting exercise that has value by itself.
It is instead their line of reasoning I object to — what they claim their model results mean in terms of causation– in their obvious attempt to relegate the role of water vapor in the atmosphere to that of a passive component that merely responds to the warming effect of CO2…the real driver (they claim) of the climate system.
OUR ASSUMPTIONS DETERMINE OUR CONCLUSIONS
From what I can tell reading the paper, their claim is that, since our primary greenhouse gas water vapor (and clouds, which constitute a portion of the greenhouse effect) respond quickly to temperature change, vapor and clouds should only be considered “feedbacks” upon temperature change — not “forcings” that cause the average surface temperature of the atmosphere to be what it is in the first place.
Though not obvious, this claim is central to the tenet of the paper, and is an example of the cause-versus-effect issue I repeatedly refer to in the past when discussing some of the most fundamental errors made in the scientific ‘consensus’ on climate change.
It is a subtle attempt to remove water vapor from the discussion of “control” over the climate system — by definition. Only those of us who know enough of the details of forcing-feedback theory within the context of climate change theory will likely realize this, through.
Just because water vapor responds quickly to temperature change does not mean that there are no long-term water vapor changes (or cloud changes) — not due to temperature — that cause climate change. Asserting so is a non sequitur, and just leads to circular reasoning.
I am not claiming the authors are being deceptive. I think I understand why so many scientists go down this path of reasoning. They view the climate system as a self-contained, self-controlled complex of physically intertwined processes that would forever remain unchanged until some “external” influence (forcing) enters the picture and alters the rules by which the climate system operates.
Of course, increasing CO2 is the currently fashionable forcing in this climatological worldview.
But I cannot overemphasize the central important of this paradigm (or construct) of climate change theory to the eventual conclusions the climate researcher will inevitably make.
If one assumes from the outset that the climate system can only vary through changes imposed external to the normal operation of the climate system, one then removes natural, internal climate cycles from the list of potential causes of global warming. And natural changes in water vapor (or more likely, clouds) are one potential source of internally-driven change. There are influences on cloud and water vapor other than temperature which in turn help to determine the average temperature state of the climate system.
After assuming clouds and water vapor are no more than feedbacks upon temperature, the Lacis et al. paper then uses a climate model experiment to ‘prove’ their paradigm that CO2 drives climate — by forcing the model with a CO2 change, resulting in a large temperature response!
Well, DUH. If they had forced the model with a water vapor change, it would have done the same thing. Or a cloud change. But they had already assumed water vapor and clouds cannot be climate drivers.
Specifically, they ran a climate model experiment in which they instantaneously removed all of the atmospheric greenhouse gases except water vapor, and they got rapid cooling “plunging the climate into an icebound Earth state”. The result after 7 years of model integration time is shown in the next image.
Such a result is not unexpected for the GISS model. But while this is indeed an interesting theoretical exercise, we must be very careful about what we deduce from it about the central question we are ultimately interested in: “How much will the climate system warm from humanity adding carbon dioxide to it?” We can’t lose sight of why we are discussing all of this in the first place.
As I have already pointed out, the authors have predetermined what they would find. They assert water vapor (as well as cloud cover) is a passive follower of a climate system driven by CO2. They run a model experiment that then “proves” what they already assumed at the outset.
But we also need to recognize that their experiment is misleading in other ways, too.
First, the instantaneous removal of 100% of the greenhouse gases in the atmosphere except for water vapor causes about 8 times the radiative forcing (over 30 Watts per sq. meter) as does a 100% increase in CO2 (2XCO2, causing less than 4 Watts per sq. meter), something that will not occur until late this century — if ever.
This is the so-called ‘logarithmic effect’…adding more and more CO2 has a progressively weaker radiative forcing response.
Currently, we are about 40% of the way to that doubling. Thus, their experiment involves 20 times (!) the radiative forcing we are now experiencing (theoretically, at least) from over a century of carbon dioxide emissions.
So are we to assume that this dramatic theoretical example should influence our views of the causes and future path of global warming, when their no-CO2 experiment involves ~20 times the radiative forcing of what has occurred to date from adding more CO2 to the atmosphere?
Furthermore, the cloud feedbacks in their climate model are positive, which further amplifies the model’s temperature response to forcing. As readers here are aware, our research suggests that cloud feedbacks in the real climate system might be so strongly negative that they could more than negate any positive water vapor feedback.
In fact, this is where the authors have made a logical stumble. Everyone agrees that the net effect of clouds is to cool the climate system on average. But the climate models suggest that the cloud feedback response to the addition of CO2 to our current climate system will be just the opposite, with cloud changes acting to amplify the warming.
What the authors didn’t realize is that when they decided to relegate the role of clouds in the average state of the climate system to one of “feedback”, their model’s positive cloud feedback actually contradicts the known negative “feedback” effect of clouds on the climate’s normal state.
Oops.
(In retrospect, I suppose they could claim that cloud feedbacks switched from negative at the low temperatures of an icebound Earth, to being positive at the higher temperatures of the real climate system. But that might mess up Jim Hansen’s claim of strongly positive feedbacks during the Ice Ages).
CONCLUSION
Taken together, the series of computations and claims made by Lacis et al. might lead the casual reader to think, “Wow, carbon dioxide really does have a strong effect on the Earth’s climate system!” And, in my view, it does. But the paper really tells us nothing new about (1) how much warming we can expect from adding more CO2 to the atmosphere, or (2) how much of recent warming was caused by CO2.
The paper implies that it presents new understanding, but all it does is get more explicit about the conceptual hoops one must jump through in order to claim that CO2 is the main driver of the climate system. From that standpoint alone, I find the paper quite revealing.
Unfortunately, what I present here is just a blog posting. It would take another peer-reviewed paper that follows an alternative path, to effectively counter the Lacis paper, and show that it merely concludes what it assumes at the outset. I am only outlining here what I see as the main issues.
Of course, the chance of editors at Science allowing such a response paper to get published is virtually zero. The editors at Science choose which scientists will be asked to provide peer review, and they already know who they can count on to reject a skeptic’s paper.
Many of us have already been there, done that.
Dr Spencer-
Thank you for your useful and informative post. I look forward to the fully peer-reviewed paper you suggest is needed to debunk this nonsense.
Again, thank you for taking the time to prepare this post.
This article is interesting but some points are too abstract:
1. Reference is made to “internal” cycles without being specific about what those natural cycles are. Are we talking about some self-sustaining oscillation driven by some external energy source? I have never heard of this before in relation to the climate. What us the physical mechanism?
2. I suspect that there can be a lot of semantic confusion when describing cause and effect in a complex system with multiple interactions including feedbacks. However I cannot see water vapor as a control knob for the climate; since if you add more to the atmosphere somehow, it will simply condense as liquid, thus returning to it’s equilibrium value and thus negating the original forced changed.
Excellent post! When you say that you believe/think that CO2 plays an important part in our climate system, am I correct in assuming that you mean in respect to creating life, & the slight warming of around +3.3°C to the average global temperature.
I suppose that the human brain, the most powerful weapon & tool on the planet, is subject to frailties of preconceived ideas. Rather like (& I have no wish to offend anybody but the facts stand for themselves) homeopathic medicine, in that every effort to demonstrate its validity has ended in disaster for those constructing the proving experiment, when they were found to have pre-judged the outcome subconciously!
Thank you Dr Spencer for a wonderful posting… which has generated some very informative comments. What I particularly admire is your ability to coherently respond with reasoned arguments… especially as I find it difficult to respond meaningfully when I encounter the ravings from the asylum that simply leave me speechless because I find it very difficult to respond rationally to irrational behaviour.
For me their propositions and approach is simply non-scientific… they try to measure the current global climate and model the future global climate based upon flawed current measurements and flawed computer models which simply reflect their ignorance and selection bias… to call this science is simply insane. But their insanity does not stop there. Their next step in logic is simply breathtaking… they predict a change in climate… well that is ok as that is what climate does… the really stunning bit is that this change is blamed upon mankind burning fossil fuels because they have eliminated all other possibilities from their models and thought processes.
Now if you wished to prove that mankind was effecting the climate by burning fossil fuels then surely the place to start is by studying the impacts of burning fossil fuels. The science of combustion is fairly well understood… the burning of fossil fuels produces HEAT, WATER, CO2, SOOT and other chemicals such as carbon monoxide, nitrogen dioxide, sulphur dioxide and other compounds.
So if we see global temperatures rise then we could assume that some of this heat has been resulted from burning fossil fuels… and some of this heat has been trapped by the greenhouse gases produced by combustion i.e. water and CO2… and then, perhaps, we can add on something extra for all that black soot in the air. Now my guess is that if we let these climate science clowns put all this thorough their computer models we would discover that we all roasted to death at the start of the industrial revolution.
However, this speculation is really still nonsense… because with all computer programs we should perform a reality check to see if the answers are reasonable. This is where the real problems start because on a global scale the additions of mankind into the atmosphere as so trivial compared to the vast natural cycles (of heat, water and CO2) that they are really immeasurable… just as immeasurable as the concepts of global temperature, global CO2 level and global water vapour level.
Bottom line: Where ignorance is bliss it is folly to be wise… but we would be crazy if we let the inmates takeover the asylum.
“Specifically, they ran a climate model experiment in which they instantaneously removed all of the atmospheric greenhouse gases except water vapor, and they got rapid cooling “plunging the climate into an icebound Earth state”.”
So a big dehumidifier would ameliorate global warming?
This “experiment” only shows a computer model’s underlying assumptions sensitivities to gross inputs. That is all I can infer from the paper. From there I have to leap to a real world conclusion? Think not.
Thank you Dr. Spencer.
Best Regards,
Malaga View says: ”’
“Bottom line: Where ignorance is bliss it is folly to be wise… but we would be crazy if we let the inmates takeover the asylum.”
Unfortunately, they already have taken it over, and they are trying to put us in it.
BWD
TimM says:
October 22, 2010 at 1:55 am
So a big dehumidifier would ameliorate global warming?
Now that depends upon how much warmed dry air it pumps out 🙂
Perhaps we should add it onto the shopping list, based upon the precautionary principle, along with that giant wave machine needed to offest all that tidal generated energy, that huge fan to offset all those wind farms… and don’t forget that huge electric drill we need to make lots of holes which can be filled with all that horrible CO2 that is greening our planet.
The method the GISS paper uses is, I believe, in logic is called “fallacy”. It sounds like a subtle sub-part called innuendo. Hence the old expressions akin to “if you assume your hypothesis, the proof is easy”.
If they were really serious about CO2 perhaps they should consider banning recycling unless it is proved to reduce CO2 emissions… surely putting paper and other organic waste into a landfill is sequestering CO2.
For me the concept of recycling is seriously flawed… or, at best, not proven… as the consumer must use precious resources to sort, clean and store the waste which is then frequently driven to a collection point before it is collected for secondary sorting, cleaning and storage… before it is transported for a third time for sorting, cleaning and storage by the recycler… the recycling process then usually incorporates additional purifying processes to produce the recycled material which is then stored before it is transported for a fourth time to the manufacturer that actually uses the recycled material… perhaps that is why so much ends up in landfills anyway.
I recently encountered one of the interesting downside to recycling on my last trip to Dublin where they have issued an new Brown Bin to every household for their organic waste… each house now has three bins which they have to manage and pay for… but I digress. Now having a compost heap at the bottom of your garden if one thing… having a festering brown bin full of organic waste by your front/back door is another thing altogether… the flies and smells are horrendous in summer… especially when the winds blows them through your open doors and windows… and it is all safe to remember that smells are particulate… so think about that the next time you smell your recycling bin and your sewers….
The bizzarre paper by the RC enforcers will o down in history as the final straw that makes people see how laughable the CO2 obsession is.
This paper is transparently contrived and an obvious abuse of the scientific process.
Now not only is the LIA and MWP disappeared, but the physics of H2O are as well.
Nothing can exist, in the mind of the CO2 obsessed, but CO2.
BigWaveDave says:
October 22, 2010 at 2:28 am
Unfortunately, they already have taken it over, and they are trying to put us in it.
I think you are right… but I hope you are wrong… Blogging and commenting are possibly futile gestures… but at least they help to keep me sane… well sort of… our best hope is that El Sol continues to slumber so that nature can contradict the warmists… but even that might not be enough based upon they way they spin and dissemble…
Check this paper of Spencer’s out:
http://wattsupwiththat.com/2010/09/14/spencer-on-water-vapor-feedback/
(Or look at his book, The Great Global Warming Blunder.)
Am I missing something here.
Surely their “thought experiment” is a function of the value they apply to climate sensitivity.
We had a post not so long ago from Frank Lansner showing 9 doublings of CO2. If we take those 9 doublings and convert them into halvings, and then apply a high number for climate sensitivity, and then backtrace through the halvings, we get a huge number when we strip out all greenhouse gasses. If on the other hand we use a more realistic number, like 1degree for all GHGs we get a much smaller number.
I haven’t seen the full paper so I can’t comment with any authority, but ISTM that that is what is at play here.
Axel Sjöqvist, the answer a to why a derivative paper that says nothing about reality like Lacis, et al gets published with fanfare in Nature is that Nature is no longer about science, and their article fit in perfectly.
Thank you, Dr Spencer, for your gentle demolition job on this paper.
This sentence shows in a nutshell why arguing with AGW proponents, even on a purely scientific basis, is so difficult:
“They view the climate system as a self-contained, self-controlled complex of physically intertwined processes that would forever remain unchanged until some “external” influence (forcing) enters the picture and alters the rules by which the climate system operates.”
Where scientific experiments, ‘thought’ or otherwise, are solely undertaken and/or employed to cement and defend a world view, implying that sceptics are heretics, then science itself is the loser.
Peter Miller says on October 21, 2010 at 11:56 pm:
“So the world has to be saved from the foolishness, fraud and deceit of climate ‘scientists’ by the blogosphere – it is scary to think 20 years ago, they would have got away with it … (snip)”
Indeed!
I confess that twenty years ago, with no blogosphere, I fell for the ‘New Ice Age’ scare, became thoroughly frightened, and spent weeks pondering what I could do for my family’s survival when the glaciers started appearing.
All nicely driven by the MSM – not much change there!
@crosspatch
Loved your thinking about the effect of glaciation thickening affecting altitude and hence temperature.
I’ve not seem this mentioned before but it makes absolute sense. If I was studying the science of Ice Ages, I’d been looking closely at the possible effects that your ideas could bring to the table.
Why don’t the authors simply go out into the desert after dark, strip off all their clothes and then decide if it is lack of water vapor or lack of CO2 that freezes their ass off.
[LOL ~jove, mod]
I guess everyone recognizes this is just a GISS ModelE climate model output. It is based on calculations that James Hansen would have put into the model.
So generally, one either accepts James Hansen view of the world or one would ask for additional empirical data to be measured to back up the theoritical calculations (ie what we used to call the scientific method).
What does the empirical data tell us (with regard to this paper’s and the theory’s proposition that GHGs control 85% of the water vapour levels as well).
– Total specific humidity water vapour levels are completely FLAT (according to the NCEP reanalysis since 1948) or, (according to Hadcruh – Willet et al 2008 – at the highest estimate), there is an increase at about the levels expected by the theory. There is also annual variation tied closely to the ENSO. GISS ModelE would be calculating about a 1/2oth increase in specific humidity (and more-or-less constant relative humidity) over the period covered by this data.
http://img147.imageshack.us/img147/7908/specifichumidity.png
http://img21.imageshack.us/img21/3537/relativehumidity.png
http://hadobs.metoffice.com/hadcruh/CRUBLENDNEWjul08_ts_q_global7303.png
– Global Precipitation Levels are essentially FLAT since 1979 and precipitation on land is FLAT since 1950. GISS ModelE would be predicting about a 1.5% increase over the time period covered by this data.
http://img684.imageshack.us/img684/8974/trenberthprecipitation.png
http://img215.imageshack.us/img215/2026/riverdischargeandprecip.png
– And there has been a general decline in the level of cloudiness according to the ISCCP project – GISS ModelE would be predicting about a 1% increase in cloudiness over the period covered by this data.
http://isccp.giss.nasa.gov/zD2BASICS/B8glbp.anomdevs.jpg
http://isccp.giss.nasa.gov/climanal7.html
So, on the whole, the theory and ModelE is not matching up to the empirical data.
Dr. Spencer, doesn’t clouds’ role in feedback depend on the time of day? In the daytime, cloud cover is a negative feedback, allowing less solar energy to reach the surface. But at night cloud cover is a positive feedback, blocking re-radiation from the surface back into space.
It is the net cloud effect that counts, and it has been argued that could make clouds a ‘buffer agent’ in the atmospheric ‘solution.’
correlation does not always equal causation … could just be a coincidence …
but for one to ascribe causation you MUST have correlation …
CO2 and temperatures do not have a good correlation over the last 100 years … (they actually have a negative correlation for a good chunk of it)
until a clear verifiable explanantion of the global cooling from about 1940 to 1970 is explained I call BS on all of this witchcraft …
since this observed cooling would have taken place when CO2 was rapidly increasing, in the AGW theory this cooling mechanism had to not just cancel out the CO2 warming but completely overwhelm it …
More CO2 in the MArtian atmosphere than Earth’s. Hmm, I’ve never thought of it like that. Good factoid.
Even at zero degrees F, the amount of water vapour in the air is much larger than the amount of CO2. The whole premise of their study (that all water vapour could be removed) is bogus.
Excellent discussion, Dr. Roy Spencer, of a “climate model” that as usual follows the computer truism: Garbage In Garbage Out. Thank you for helping readers understand the tricky fine points of cause v effect.
I have a question about the circulation of political magazines like Science and Nature since so many (of us) have cancelled our subscriptions. Main reason: lack of trust, or how can we know whether science or propaganda is being presented. Are there scientific journals with a large readership at present that have actual peer review and required submission of data and methods — whose circulation we can enhance? Or has the circulation of these remained small (no funding by George Soros and his global-billionaire ilk)?
I have copies of articles you have published in Geophysical Research Letters (2007) and Journal of Climate (2008) plus a number from your site and some of your posts on WUWT. Enjoyed your discussion of the 2009 AGU presentation on the negative feedback of clouds. Two questions. 1. Where can those who want to read real science and scientific debates turn? 2. The corollary, as a counter to Science and Nature: (of) which science journals can we expand the subscription base?