How’s this for “rapid response“? This rebuttal comes out at exactly the same time the press embargo lifts in Science. We were able to obtain advance copies of the Dessler paper, plus Dr. Spencer had seen it as a poster at the recent A-Train satellite symposium. – Anthony
Update: Dessler responds here at Real Climate and makes the full paper available here at his TAMU website.
2PM EST, December 9th, 2010 by Roy W. Spencer, Ph. D.
How clouds respond to warming – the ‘cloud feedback’ problem – will likely determine whether manmade global warming becomes either the defining environmental event of the 21st Century, or is merely lost in the noise of natural climate variability.
Unfortunately, diagnosing cloud feedback from our global satellite observations has been surprisingly difficult. The problem isn’t the quality of the data, though. The problem is figuring out what the cloud and temperature behaviors we observe in the data mean in terms of cause and effect.
So, Andy Dessler’s (a Texas A&M climate researcher) new paper appearing in Science this week is potentially significant, for it claims to have greatly closed the gap in our understanding of cloud feedback.
Dessler’s paper claims to show that cloud feedback is indeed positive, and generally supportive of the cloud feedbacks exhibited by the IPCC computerized climate models. This would in turn support the IPCC’s claim that anthropogenic global warming will become an increasingly serious problem in the future.
Unfortunately, the central evidence contained in the paper is weak at best, and seriously misleading at worst. It uses flawed logic to ignore recent advancements we have made in identifying cloud feedback.
In fact, the new paper is like going back to using only X-rays for medical imaging when we already have MRI technology available to us.
What the New Study Shows
So what is this new evidence of positive cloud feedback that Dessler has published? Well, actually it is not new. It’s basically the same evidence we published in the Journal of Geophysical Research.
Yet we came to a very different conclusion, which was that the only clear evidence of feedback we found in the data was of strongly negative cloud feedback.
But how can this be? How can two climate researchers, using the same dataset, come to opposite conclusions?
The answer lies in an issue that challenges researchers in most scientific disciplines – separating cause from effect.
Dessler’s claim (and the IPCC party line) is that cloud changes are caused by temperature changes, and not the other way around. Causation only occurs in one direction, not the other.
In their interpretation, if one observes a warmer year being accompanied by fewer clouds, then that is evidence of positive cloud feedback. Why? Because if warming causes fewer clouds, it lets in more sunlight, which then amplifies the warming. That is positive cloud feedback in a nutshell.
But what if the warming was caused by fewer clouds, rather than the fewer clouds being caused by warming? In other words, what if previous researchers have simply mixed up cause and effect when estimating cloud feedback?
A Step Backwards for Climate Science
What we demonstrated in our JGR paper earlier this year is that when cloud changes cause temperature changes, it gives the illusion of positive cloud feedback – even if strongly negative cloud feedback is really operating!
I can not overemphasize the importance of that last statement.
We used essentially the same satellite dataset Dessler uses, but we analyzed those data with something called ‘phase space analysis’. Phase space analysis allows us to “see” behaviors in the climate system that would not be apparent with traditional methods of data analysis. It is like using an MRI to see a type of tumor that X-rays cannot reveal.
What we showed was basically a new diagnostic capability that can, to some extent, separate cause from effect. This is a fundamental advancement – and one that the news media largely refused to report on.
The Dessler paper is like someone publishing a medical research paper that claims those tumors do not exist, because they still do not show up on our latest X-ray equipment…even though the new MRI technology shows they DO exist!
Sound strange? Welcome to my world.
We even replicated that behavior see in the satellite data analyzed with phase space analysis — our ‘MRI for the climate system’ – by using a simple forcing-feedback climate model containing negative cloud feedback. It showed that, indeed, when clouds cause temperature changes, the illusion of positive cloud feedback is created…even when strongly negative cloud feedback really exists.
Why Dessler Assumed We Are Wrong
To Dessler’s credit, he actually references our paper. But he then immediately discounts our interpretation of the satellite data.
Why?
Because, as he claims, (1) most of the climate variability during the satellite period of record (2000 to 2010) was due to El Nino and La Nina (which is largely true), and (2) no researcher has ever claimed that El Nino or La Nina are caused by clouds.
This simple, blanket claim was then intended to negate all of the evidence we published.
But this is not what we were claiming, nor is it a necessary condition for our interpretation to be correct. El Nino and La Nina represent a temporary change in the way the coupled atmospheric-ocean circulation system operates. And any change in the atmospheric circulation can cause a change in cloud cover, which can in turn cause a change in ocean temperatures. We even showed this behavior for the major La Nina cooling event of 2007-08 in our paper!
It doesn’t mean that “clouds cause El Nino”, as Dessler suggests we are claiming, which would be too simplistic and misleading of a statement. Clouds are complicated beasts, and climate researchers ignore that complexity at their peril.
Very Curious Timing
Dessler’s paper is being announced on probably THE best day for it to support the IPCC’s COP-16 meeting here in Cancun, and whatever agreement is announced tomorrow in the way of international climate policy.
I suspect – but have no proof of it – that Dessler was under pressure to get this paper published to blunt the negative impact our work has had on the IPCC’s efforts.
But if this is the best they can do, the scientists aligning themselves with the IPCC really are running out of ideas to help shore up their climate models, and their claims that our climate system is very sensitive to greenhouse gas emissions.
The weak reasoning the paper employs – and the evidence we published which it purposely ignores! – combined with the great deal of media attention it will garner at a time when the IPCC needs to regain scientific respectability (especially after Climategate), makes this new Science paper just one more reason why the public is increasingly distrustful of the scientific community when it comes to research having enormous policy implications.
===============================================================
Abstract:
On a global scale, clouds presently influence climate in a way that cools the planet. But, they will lose some of that cooling capacity as climate warms, according to a study that supports current ideas about how atmospheric carbon dioxide affects global temperature. Clouds can potentially have both positive and negative feedback effects on climate, and this is responsible for much of our uncertainty about the amount of warming that will be caused by increasing concentrations of carbon dioxide in the atmosphere. It’s generally agreed that overall this feedback is positive, with warming being exacerbated as clouds trap larger quantities of outgoing infrared radiation, but so far we have only a general idea of this effect. Andrew Dessler has estimated the actual magnitude of the feedback effect by analyzing ten years of satellite data on the flux of radiation through the top of the atmosphere. He concludes that the feedback effect is indeed positive and of a value that agrees with the canonical range of estimates of how much warming will occur for a doubling of atmospheric carbon dioxide.
Article #10: “A Determination of the Cloud Feedback from Climate Variations over the Past Decade,” by A.E. Dessler at Texas A&M University in College Station, TX.
Contact: A.E. Dessler at +1-979-862-1427 (office phone), +1-979-220-4513 (mobile phone), or adessler@tamu.edu (email).
I’ve been using Real Climate to try to persuade Andrew Dessler to provide information that would enable a reasonable comparison to be made between his paper and Spencer and Braswell 2010, but it has been very frustrating. Although a couple of my questions were accepted, I felt that the responses were deliberately evasive. I persisted, and although I was polite and staying focused on the scientific issues, my posts were repeatedly rejected. Meanwhile, Real Climate supporters continued to successfully post offensive character assassinations against both Spencer and Lindzen. This is the first time I’ve tried posting there, and frankly I find it difficult to understand what the people running Real Climate believe they achieve by this kind of behaviour.
In any case, here is my rejected question, just in case Andrew is still hovering around here:
Although I haven’t had an answer to this yet, I did notice that Andrew provided a reply to Fred #56, which I think is relevant:
As far as I know (please correct me someone, if this is incorrect), the substantive parts of Andrew’s reply to Fred are both untrue:
[1] Andrew says that SB 2010 is “saying that if you don’t know what’s causing the temperature change, determining feedbacks is impossible.” But my understanding is that SB 2010 is suggesting you can estimate feedbacks by examining the phase space plot and that the paper provides a theoretical reason why that should be so.
[2] Andrew says that SB 2010 is “not describing a new or different way to determine the feedback.” But again my understanding is that SB 2010 is doing precisely that by using the phase space plo
Once again – we get models and studies on individual components of our climate and attempt to control for them by refusing to acknowledge either how they interact or that we don’t know.
Amazing. The logic of Dr. Dresler’s theory does indeed suggest a hot cloudless planet, which should have already been achieved, long, long ago, if we accept as fact that the earth has been warmer than today within the last 10,000 years.
The summary to all this is really very simple. Whatever controls the energy content of the ocean on such a planet as our earth is the primary driver of climate. And the answer is SWR from the sun, either increasing or decreasing at the ocean surface, is the primary driver of our planets energy budget. To assume that an effect which increases the LWR in the atmosphere at the expense of a reduction in SWR entering the oceans, controls the climate and earths energy budget, is to claim that a small puff of wind can reverse the direction of an ocean liner under throttle. Besides the seasonal changes, it is changes in cloud cover and location that primarily affect how much or how little SWR enters the ocean. An increase in LWIR can cause a short term increase in atmospheric heat content, but over a longer term the reduction in SWR heating the ocean will produce mitigate as negative feedpack to the increased hydrologic cycle.
It is a curious thing, the more the CAGW crowd tries to state that the hidden heat is in the oceans and it just takes an ever longer time to manifest, the more they diminish the role of CO2 and LWR relative to SWR. If the energy within the oceans residence time is very long, then any change in the energy most capable of heating the oceans, SWR, will have a far greater effect then the short term energy of LWR within the atmosphere. The residence time of energy within a system is in direct relationship to its heat sink capacity.
A comment I left at Dr. S’s site on this:
Andy asks, “… what is the limit that Global Temperatures could hit assuming co2 continues to increase at the predicted rate? Or will temperatures rise indefinitely?
I am of course writing this from the UK which currently resembles a large Popsicle.”
Well, best estimates are that we could barely reach 1600 ppm CO2 if we burned all the fossil fuel on the planet at once.
Dr. S, Lindzen & Choi, and others are converging on a sensitivity around half a degree C per doubling. So:
400 ppm — 0 (now)
800 ppm — +0.5
1600 ppm — +1.0
Answer: About one degree C. more than now. Hardly enough to melt a popsicle. If the sensitivity turns out to be 0.7, then a degree and a half.
And for an idea of how dangerous 1600 ppm of this dreadful pollutant is, that’s less than a quarter of the US Navy’s limit for CO2 concentration in a submarine.
What level of evaporation was assumed? I am referring to Dr Lindzen’s presentation to Congress. The GCM’s assume 1-3% per degree F. The observations suggest a much larger 5.7% per degree (Wentz, et al.). Surely, this value is fundamental to determining the sign of the feedback term. I believe, Dr Dessler’s paper is using empirical data and making no assumptions about this value. However, this data would be skewed BECAUSE the observations occurred over La Nina waters IMHO. Surely, the initial temperature of the oceans would effect whether warming resulted in more or fewer clouds because this would effect the local adiabatic lapse rate. This could be investigated by checking the apparent feedback versus local SST.
Another comment, you can have positive feedbacks without runaway warming. A net positive feedback can still exist without a closed loop gain greater than one. However, significant positive feedbacks would result in an unstable output response. It is a valid point to observe that that is not reflective of the planet we live on. I believe this fact is the source of Lindzen’s statement that it is “intuitively implausible” that the earth’s climate is dominated by positive feedbacks.
Bill Illis says:
December 10, 2010 at 4:55 am
“Nope, each increment of more clouds is still a negative feedback.
Clouds increase as it gets warmer. Clouds provide a net cooling. Therefore, clouds are a negative feedback even if they are less negative as the warming increases.”
No. Feedback is a sensitivity parameter, a partial derivative, rather than a direct quantity. Think of an easy feedback system in your home: the toilet. Within the tank is a float, which senses the level in the tank, and progressively applies greater pressure as the level rises, eventually closing the valve and keeping the water at a set level. This is a negative feedback – the closing valve counteracts the inrush of the water by applying increasing valve resistance to the flow.
Now, consider a case where this is reversed, and the float actually opens the valve more as the level rises. At every level before it is fully open, the valve is partially closed, so it is impeding the water all the time (same as your saying the clouds are cooling all the time). But, this is a positive feedback, because as the level rises, the valve’s resistance to the flow decreases.
Eventually, this will lead to overflow, unless perhaps you have a bigger float which acts to close the valve once the level reaches beyond a certain level. This would be a very strange design for a toilet, granted, but that is an analogy to how the larger negative feedbacks in the climate system would prevent a positive feedback from causing instability (or overflow, in this analogy). But, the level would undoubtedly reach a higher level with the positive feedback of the first float than with the negative feedback from it. In such a way, we see that positive feedback internal to a larger negative feedback acts to amplify the output.
A quote from the paper to help everyone get their head around this:
” … the net effect of clouds is to reduce the net flux of incoming energy at the top of the atmosphere (TOA) by ~20W/m2, as compared to an otherwise identical planet without clouds. The cloud feedback refers to changes in this net effect of clouds as
the planet warms. If, as the climate warms, cloud changes further reduce net incoming energy, this will offset some of the warming, resulting in a negative cloud feedback. If, on the other hand, cloud changes lead to increases in net incoming energy, then the change will amplify the initial warming, resulting in a positive cloud feedback.”
So, Dessler’s conclusion is that as the planet warms, the clouds will let in more incoming solar energy (even though the same paper shows they increase as the planet warms).
I guess they thin out by a larger percentage as the planet warms. Which is something that Dessler should have proven/shown rather than rely on CO2-based climate model results.
And I have to question Dessler’s number of -20 watts/m2 above because clouds represent more than half of the planet’s Albedo or let’s say at least -55 watts/m2.
That alone means there is a serious error in the paper and how the data was processed.
I’d be impressed if people could just spell Dessler’s name right.
Interesting article from the arXiv blog
http://www.technologyreview.com/blog/arxiv/26105/?p1=Blogs …
Essentially, Dallas and Vassilicos are saying that micrometer scale turbulence accelerates cloud formation and triggers rain showers.
That’s an interesting, although not entirely unexpected result that should lead to better weather forecasts. Perhaps more significantly, it could also have a big impact on climate models. Clouds have a big effect on the amount of light Earth reflects back into space. Being able to better calculate when they form is important.
And it plugs an embarrassing hole in our understanding of one of the most basic atmospheric phenomena.
Wonder how much this finding affects the climate models people like Dr Dessler use. If this really is a “new” piece of information, then the GCMs are (obviously and always) wrong.
“Amazing. The logic of Dr. Dresler’s theory does indeed suggest a hot cloudless planet, which should have already been achieved, long, long ago, if we accept as fact that the earth has been warmer than today within the last 10,000 years.”
“Dessler”, the man has a name of his own of course.
Why, yes. This apparently is a problem of language. What exactly do these climatatologists understand the word “Feedback” to mean? Anyone in a junior high auditorium experiencing the awful trill/scream of auditory “feedback” knows firsthand what it means. What is the the other meaning? Seems to have something to do with the “Climate Sensitivity” being larger or smaller than 2.0 degrees C, but in what way exactly?
Terms are important. Is Climatology a science at all???????????????????
In my business, these people would be laughed out of the room as rank amateurs, not allowed to speak after the first idiotic thing they said….
It means the same thing thought their use of positive and negative is inconsistent with the actual theory as well as function. Few acually demonstrate even basic understanding of how it works.
Mark
when you look at the basics of thermodynamics the electron is what is moving.
A cloud is nothing more than a resistor in a circuit. it can only react to changes of polarity, EMF, and it works in both directions. Clouds are a result of not the reason for the change.. but can result in a slower change to equilibrium.
However, Clouds can become a factor if excited by other forces… Galactic rays… which ionize water and form clouds can enhance the cooling by thickening the clouds and increasing the reflective properties..
I admit being in an area with which I am technically unfamiliar. But the discussion, while interesting and educational, sounds more like an argument about the question: which came first, the chicken or the egg? Even moreso, it sounds like Dessler is taking the same data as Spencer is using and putting his own personal spin on it. Which is more evidence that the science remains quite unsettled. It also proves that two scientists are very much like two attorneys: when you talk to them, they give you at least three different opinions.
CORRECTION:
original=Clouds are a result of not the reason for the change..
Corrected= Clouds are normally present and act as a buffer of changes in drivers.
when i reread my previous post i had made an error in description. the only result of outside factors on clouds is increasing or decreasing the coverage and intensity of buffering. clouds are an intermediary in the energy transfer and can act as a positive or negative feedback mechanism.
Re Bill Illis says:
December 10, 2010 at 5:32 pm
Bill, even more important then the amound of energy reduced is the wavelength. Clouds and water vapor induce tremendous solar spectrum modifications, water vapor on a clear day reduces the SWR by 20%, and considerably more in the tropics on clear day. At its most basic only two things can effect the energy content of any system in a radiative balance. Either a change in the input, or a change in the “residence time” of some aspect of those energies within the system. Residence time of energy correlates to heat capacity. The greater “residence time” of the oceans allows a far larger increase or decreases relative to any change in input then an equivalant change in the shorter road of the atmosphere. A simple traffic analogy will work to illustrate this.
On a highway if ten cars per hour enter the highway, and the cars are on the road for ten hours before exiting, there will be 100 cars on the road and as long as these factors remain the same the system is in balance. If you change the INPUT to eleven cars per hour, then over a ten hour period the system will increase from 100 cars to 110 cars before a balance is restored and no further increase occurs. The same effect as the increase in INPUT achieves can be realized by either slowing the cars down 10% or by lengthening the road 10%. In either case you have increased the energy in the system by ten percent by either increasing the residence time or the input.
3. Now lets us take the case of a very slow or long road with the same input. Ten cars per hour input, 1000 hours on the road, now you have ten thousand cars on the road. Now lets us increase the input to eleven cars per hour just as we did on the road with a ten hour residence time. Over a 1,000 hour period we have the same 10% increase in cars (energy) How ever due to the greater capacity on that road the cars, (energy) have increased 100 times, (1,000 verse 10 ) Any change in the input or the residence time on this 1,000 hour road will have a 100 times greater effect then on the 10 hour road.
This is cogent to climate in that the 10 hour road is the atmosphere, and the 1000 hour road is the oceans. Any change into the ocean input is going to have a FAR GREATER long term effect then an equivalent change in the residence time of energy in the atmosphere. The reduction in SWR induced by clouds will, over time, overwhelm the increase in LWIR clouds induce within the atmosphere.
Share your thoughts on this please. Thanks
Clouds are a result of not the reason for the change..
Which highlights the fact that they are not a positive feedback. Clouds are a result of evaporation, block the incoming SWR, which results in less evaporation, and then less clouds, which results in more evaporation, more clouds, blocking incoming SWR, resulting in less clouds…
Still, I would say that Spencer’s point that this could appear as a positive feedback is understandable, wouldn’t you? If you start looking in a year where there is less evaporation, you would see that there is more heat, and so more clouds, and be confused.
If, however, you were to study cloud behavior over the poles or deserts, it’s pretty obvious that clouds thrive on evaporation. Also clear from studying the tropics is that evaporation and cloudiness will, after a turn, lead to less clouds. So, again, where does Dessler separate the chicken from the egg?
To highlight what I mean by referring to poles or deserts, the dryness of air in these places means very few clouds, moisture seems the dominant condition. A fact that is freckled onto the shoulders I left in the Mojave sun a bit too long. Still, that is why I referred upthread aways to paleonimbus data. It would solve quite a bit, but I fear it goes in the logical direction that clouds seek to regulate forcings in order to maintain the liquid state of water, and no more or less. How’s that for a thought? You’re both right, under the right circumstances.
Bill Illis
..the NET effect of clouds… They also have a greenhouse effect.
Check the inverse relationship between low level, and medium level clouds. If you see their functions in terms of low level clouds keeping cold nights warmer, and medium level clouds reducing daytime maximums, it makes good sense of observations in terms of the response to changes in solar forcing :-
http://www.climate4you.com/images/CloudCoverAllLevel%20AndWaterColumnSince1983.gif
As Aynsley Kellow (Dec 9th, 1:43 PM) noted the uncertainty given by Dessler is so high as to make his results virtually meaningless.
Quoting from Dessler 2010, “The slope of this scatter plot is the strength of the cloud feedback, and it is estimated by a traditional least-squares fit to be 0.54 [+/-] 0.72 (2s) W/m2/K (the slope using the MERRA [data] is 0.46 T 0.75 W/m2/K).”
The scatter plot looks like a shotgun blast. The fact it has any measurable trend at all is astonishing.
Dessler showed that there might be a very small positive feedback, at some times and in some places). But there also might not be. Or the feedback could be negative.
dT
Orchestrated public relations.
As stressed in Crichton’s ‘State of Fear’ so long ago.
Silly plot line and characters. But I immensely respect anyone who attempts to offer rational thought to the masses beyond the blogosphere.
jc
I’ve been following Spencer, Lindzen and others on this crucial topic with great interest so when I heard of this paper by Dessler, I was quite interested. As noted by others, the extremely poor correlation in Dessler’s paper corresponding to Figure 2A with an r^2 of only 2% seems to really discredit this work. Any slope at all seems to be driven by a few points on the left. It seems that this work is a house of cards. The almost zero correlation suggests that the assertions and conclusions about cloud feedback and sensitivity are virtually worthless. The poor correlation seems to lead me back to the conclusion that Spencer’s work is on the right track and that the phase space and lags he shows provide a much better explanation. This coupled with the questions as to why we haven’t seen a runaway to a cloudless hot planet really puts Dessler’s work in doubt. The reliance on the blackbody radiation term to keep this from occuring seems like a desparate attempt to cover up the serious problems here. I have to wonder why Science did not include Spencer as a reviewer. Spencer as a reviewer could have asked Dessler to use his phase space technique to see if a better correlation of this data could have been obtained. This would have helped compare the two explanations much more effectively and, if there is any merit to Dessler’s claims, this would have helped make his case much more effectively.
Why Science did not include Spencer as a reviewer is a big question mark and suggests to me, after climate gate, Briffa gate and the hockey stick fiasco, we still do not have a fair peer review process and that there is a strong bias for keeping the AGW hypothesis alive no matter what. When will we be able to trust these people. I fear never. I will continue to watch developments and see how this ends up but right now, Dessler’s work looks like another red herring that has been promoted by the AGW orthodoxy in academia and the media.
Dessler says his analysis technique is the same as that used by Lindzen and Choi. Can somebody explain how they arrived at very different conclusions if Dessler’s claim is true? I don’t see it.