Confusing the net cloud effect with a cloud feedback: Very different beasts

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I stumbled upon a new post at WUWT today:

New peer reviewed paper: clouds have large negative-feedback cooling effect on Earth’s radiation budget

Note that Anthony has since changed the title to leave out the word “feedback”, which was the source of his confusion. It starts out as follows:

Oh dear, now we have three peer reviewed papers (Lindzen and Choi, Spencer and Braswell, and now Richard P. Allan) based on observations that show a net negative feedback for clouds, and a strong one at that. (…) The key paragraph from the new paper:

…the cloud radiative cooling effect through reflection of short wave radiation is found to dominate over the long wave heating effect, resulting in a net cooling of the climate system of −21 Wm−2.

The attentive reader will immediately spot the problem here. Watts is confusing two issues:

- the net radiative effect of clouds on climate (i.e. in comparison with having no clouds at all)

- the net feedback of clouds in response to a change in climate

The paper addresses the first, whereas Anthony interpreted it as if it addresses the second.

These are two distinctly different issues. The latter (clouds as feedback) is about how cloud cover and properties might change in response to a warming or cooling of the climate: Will the net cloud radiative effect (i.e. the former) become more or less negative.

The net radiative effect of clouds on Earth’ climate has long been known to be negative (i.e. cooling). See e.g this quote from the paper:

The overall global net cloud radiative effect is one of cooling as documented previously (Ramanathan et al., 1989).

That can be verified in any textbook on the subject and most introductions of papers on this topic. Or in my introductory post on aerosols, clouds and climate.

I pointed this error out in the thread, as did more than a few others after me (including Roy Spencer). Only after the author of the paper, Richard Allan, came in to say that this post mis-interpreted the paper, did Anthony change the title and added an update. The mistaken interpretations are still in the body of the text though.

Richard Allan wrote to me in email (reproduced with permission):

I was surprised that this paper was linked to cloud feedback since, as you mention, it attempts to quantify the well known influence of cloud on Earth’s radiation budget (at the top of the atmosphere, at the surface and within the atmosphere and also during day and night) and does not attempt to diagnose cloud feedback.

Watts goes on to say (bold in original):

The cooling effect is found to be -21 Watts per meter squared, more than 17 times the posited warming effect from a doubling of CO2 concentrations which is calculated to be ~ 1.2 Watts per meter squared.

He’s comparing apples and oranges. The 21 W/m2 is the top of the atmosphere (TOA) cloud forcing in reference to having no clouds at all (see table 1 in the paper); the 1.2 W/m2 is the surface forcing due to a doubling in CO2 concentrations. The TOA forcing of a doubling in CO2 is closer to 4 W/m2. But that’s not the “zero” point. The total greenhouse effect (due to water vapor, clouds, CO2 and other GHG) is about 150 W/m2.                                                                                                                   

In other words, this paper falls squarely within the mainstream; it further quantifies a (previously known) net cooling effect of clouds on the Earth’ climate; it does not quantify how clouds may change in response to warmer climate (cloud feedback), though it does provide a carrot stick in saying that these types of analyses are important “in assessing cloud climate feedbacks which contribute substantially to uncertainty in climate prediction.”. That may very well be, but it hasn’t been done in this paper (as confirmed by its author). 

Judging by the comments, many at WUWT took this, in combination with the whopping -21 W/m2, to mean that they discovered a gigantic negative feedback. Nope.

Tallbloke (from Lisbon fame) still insists that

if [cloud forcing] becomes slightly less negative, it’s still very negative, and overwhelms the effect of changes in co2.

… being very confused. Comments vary over a very wide range though. Many are confused (e.g. stating that as specific humidity goes up in a warmer world, so should cloud cover, whereas cloud formation depends on relative humidity rather than on specific humidity), there’s lots of laughing-at-the-scientists going on, but there are also sensible comments that either offer insight or good questions.

Mosher makes the following observation:

it is also fascinating because of what we dont see. usually you will see a whole crew of commeters pounce on the word “model”. This time they didnt.

They didnt because they thought the paper supported spencer. But it was on an entirely different topic. That misunderstanding kinda silenced the usual “models are bad” crew.

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81 Responses to “Confusing the net cloud effect with a cloud feedback: Very different beasts”

  1. Neven Says:

    Just when you thought Anthony Watts’ credibility couldn’t go any lower…

  2. Rattus Norvegicus Says:

    I saw this one early this morning and immediately picked up on Watts error. Didn’t comment though, as I’ve pretty much given up on that site. It is good for humor though!

  3. M Says:

    Yeah. This is pretty much a well-established pattern over there…

    Confusing feedback and forcing.

    Confusing absolute temperatures with anomalies: “OMG! High latitude stations are disappearing! That’s why the temperature record is warming!”

    Confusing current trends with future trends: “OMG! Sea level is only rising 3 mm per year – that means it will only be 30 cm higher in 2100, not 70 or 80 cm!” Also, “Greenland is only melting at X km^3 per year – so it will take 1000 years to completely melt!” (the latter also ignores the fact that partial changes can be bad too… Greenland doesn’t have to disappear in order to contribute 10s of centimeters of rise)

    Confusing temporary, minor errors with major problems – eg, “Arctic sea ice just dropped! OMG, sensor error! Get NSIDC on the phone, RIGHT NOW! Can you believe that they posted the bad data without checking it first??? OMG OMG!”

    Confusing local with global – eg, “1934 was the warmest year ever!”

    I could go on…

  4. chris Says:

    Here’s a simple-minded train of thought; any merit or is it too simplistic?

    1. As you say, cloud formation should depend on relative rather than specific humidity.

    2. There’s some expectation that as the troposphere warms, water vapour may rise to maintain approx constant relative humidity.

    3. If tropospheric warming results in enhanced water vapour (raised ispecific activity) that falls a little below maintenance of relative humidity, then in general clouds will form less easily on average and the cloud feedback will be a negative one.

    In other words might one estimate the sign of the cloud feedback from an inspection of the magnitude of the water vapour response?

  5. dana1981 Says:

    This gives me a flashback to Monckton and Pinker.

  6. grypo! Says:

    His update, which is at the end doesn’t really cover it. The entire post is still in complete unbelievable error. What is it like to never have to be embarrassed?

    Part of his “explanation”:

    My view is that clouds are both a feedback and a forcing. Others disagree.

    What? Like who disagrees with that? I don’t think he knows what his mistake is.

  7. Rob Honeycutt Says:

    Only one word comes to mind in relation to Anthony’s post: Doh!!

  8. simith Says:

    You know it wouldn’t be so bad if Watt’s didn’t regularly insult working scientists as being incompetent.

  9. J Bowers Says:

    Watts’s post will stay there for future passersby to stumble upon. Doubt cast. Job done.

    “My view is that clouds are both a feedback and a forcing. Others disagree. That’s an issue that will occupy us all for sometime I’m sure.”

  10. Hockey Schtick Says:

    Nice try:
    Multi-institutional study group finds strong negative-feedback cooling effect from clouds

    http://hockeyschtick.blogspot.com/2011/09/multi-institutional-study-group-finds.html

    The Newsletter of the multi-institution Climate Process Team on Low-Latitude Cloud Feedbacks on Climate Sensitivity outlines their significant findings to date:

    1. Clouds have a strong negative-feedback cooling effect on climate in both the tropics and extra-tropics

    2. A warmer climate enhances [increases] boundary layer clouds resulting in increasing negative-feedback

    3. Due to this strong negative-feedback, global climate sensitivity is only 0.41 K/(W m-2) – FAR less than the 3.7 W/m2 + assumed by the IPCC

    Introduction:

    The Climate Process Team on Low-Latitude Cloud Feedbacks on Climate Sensitivity (cloud CPT) includes three climate modeling centers, NCAR, GFDL, and NASA’s Global Modeling and Assimilation Office (GMAO), together with 8 funded external core PIs led by Chris Bretherton of the University of Washington (UW). Its goal has been to reduce uncertainties about the feedback of low-latitude clouds on climate change as simulated in atmospheric general circulation models (GCMs). To coordinate this multi-institution effort, we have hired liaison scientists at NCAR and GFDL, had regular teleconferences and annual meetings, and developed special model output datasets for group analysis. The cloud CPT web site http://www.atmos.washington.edu/~breth/CPT-clouds.html provides links to all its publications and activities. The cloud CPT has had many interesting subplots; here we focus on two of interesting recent results and its future plans. The results showcase a key CPT strategy – gaining insight from the use of several complementary modeling perspectives on the cloud feedbacks problem.

    Two recent findings of the cloud CPT:

    (1) The world’s first superparameterization climate sensitivity results show strong negative cloud feedbacks driven by enhancement of boundary layer clouds in a warmer climate.

    Superparameterization is a recently developed form of global modeling in which the parameterized moist physics in each grid column of an AGCM is replaced by a small cloud-resolving model (CRM). It holds the promise of much more realistic simulations of cloud fields associated with moist convection and turbulence. Superparameterization is computationally expensive, but multiyear simulations are now feasible. The Colorado State University and UW cloud CPT groups collaborated on the first climate sensitivity analysis of a superparameterized AGCM (Wyant et al. 2006b). The Khairoutdinov-Randall (2001, 2005) superparameterized CAM3, hereafter CAM-SP, was used. Each CRM in CAM-SP has the same vertical levels as CAM3, 4 km horizontal resolution, and one horizontal dimension with 32 horizontal gridpoints.

    Following Cess et al. (1989), climate sensitivity was assessed by examining the TOA radiative response to a uniform SST increase of 2K, based on the difference between control and +2K 3.5 year CAMSP simulations. Fig. 2 compares the results to standard versions of the NCAR CAM3, GFDL AM2 and GMAO AGCMs. All these models have similar clear-sky responses, so we just plot the +2K changes in longwave (greenhouse) and shortwave (albedo) cloud radiative forcings (ΔLWCF and ΔSWCF). Since ΔSWCF tends to be larger than ΔLWCF. boundary-layer cloud changes (which have little greenhouse effect compared to their albedo enhancement) appear to be particularly important. The CAM-SP shows strongly negative net cloud feedback in both the tropics and in the extratropics, resulting in a global climate sensitivity of only 0.41 K/(W m-2), at the low end of traditional AGCMs (e.g. Cess et al. 1996), but in accord with an analysis of 30- day SST/SST+2K climatologies from a global aquaplanet CRM run on the Earth Simulator (Miura et al. 2005). The conventional AGCMs differ greatly from each other but all have less negative net cloud forcings and correspondingly larger climate sensitivities than the
    superparameterization. The coarse horizontal and vertical resolution of CAM3-SP means that it highly under-resolves the turbulent circulations that produce boundary layer clouds. Thus, one should interpret its predictions with caution. With this caveat, cloud feedbacks are arguably more naturally simulated by superparameterization than in conventional AGCMs [conventional climate models], suggesting a compelling need to better understand the differences between the results from these two approaches.

  11. M Says:

    Ah, Mr. H. Schtick, three issues:

    First: units: 0.41 K/Wm-2 has to be multiplied by about 3.7 Wm-2 before it can be compared to the 2 to 4.5 K for CO2 doubling for equilibrium climate sensitivity.

    Second: transient vs. equilibrium: it isn’t clear from the linked page, but my guess (given that they could only run the model for a couple of years) is that they were actually calculating transient climate sensitivity, which is always smaller than equilibrium (my recollection is that 1.6 is about the center of the transient CS distribution, but I can’t be bothered to look it up right now)

    Third: the study was done by using a +2K constant sea surface temperature increase, which is known to produce lower climate sensitivities than a real CO2 doubling experiment (see papers by Wyant et al.).

    So: to sum up: rather than a difference between 0.41 and 3.7, as you assumed, it is actually more like a difference between 1.5 and 1.6, and there are reasons to believe that the way they did the calculations will produce an artificially low number in any case.

    Three strikes, you’re out!

  12. Rattus Norvegicus Says:

    Schtick, you might have pointed out that this was done in 2006. Has there been any published results to date, or did they run into a brick wall because superparamaterization didn’t work out that well?

  13. Hockey Schtick Says:

    Mr. M,

    1. Thanks for in essence acknowledging clouds have a strong negative-feedback effect, despite all the snarky remarks to the contrary

    2. 0.41*3.7=1.52C, HALF the IPCC best estimate of 3°C

    3. Paper indicates “The CAM-SP shows strongly negative net cloud feedback in both the tropics and in the extratropics, resulting in a global climate sensitivity of only 0.41 K/(W m-2), at the low end of traditional AGCMs Are you trying to claim they are comparing apples to oranges i.e. transient climate sensitivity to equilibrium climate sensitivity as is generally computed using traditional climate models? If they merely found a 0.1 difference in CS as you claim, it is very unlikely they would point out that their CS is “only” 0.41 and at the low end of traditional AGCMs since the range of CS calculations from traditional models is much much larger, nor would they be stating that the low CS is due to a “strong negative feedback” from clouds when traditional models assume a positive feedback.

    4. Please do notify the 3 top modeling centers and 8 other institutions right away to let them know your concerns.

  14. Rattus Norvegicus Says:

    Schtick,

    Please answer my question. The (non) paper you cited was done in 2006. Has there been anything published in the literature since then? Or has SP proven to be a dead end?

  15. Hockey Schtick Says:

    Rattus,

    Go to the link in my post for the group publications, then go to

    http://www.atmos.washington.edu/~breth for info on the continuation group studying cloud feedbacks

    now post-climategate, with no warming over past decade plus, and fact that project leader must tow the party line for the IPCC as the lead author on clouds for AR5, we wouldn’t want to suggest CS was low, now would we? I will email Bretherton to ask him about SP and let you know if I get a reply and suggest you do the same.

  16. M Says:

    Here’s the table of GCM transient and equilibrium climate sensitivities: http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch8s8-6-2-3.html

    1.5 is somewhat on the low end of transient.

    Rattus: I’ll bet there is ongoing work on superparameterization. But as I noted above, when they are limited to +2K SST experiments (rather than real oceans), that limits how good it can be. So superparameterization, all other things being equal, may be a superior approach: the problem is that to implement it, you have to sacrifice other aspects of the model. My understanding is that this technique is one of a couple of techniques to more explicitly represent clouds in models…

    Also, of course, GCMs are only one of the ways in which climate sensitivity has been estimated – superparameterization work says nothing about the climate sensitivity estimates from looking at 20th century trends, the last glacial maximum, or other methods (see Chapter 9 of AR4).

  17. Hockey Schtick Says:

    According to the IPCC and other sources, the proper terminology is Transient climate response (TCR) and equilibrium climate sensitivity (ECS). Using the term “transient climate sensitivity” appears to be improper, thus it is unlikely the study group would have said “climate sensitivity” when they were instead talking about transient climate response.

    I will also email Bretherton to confirm this.

  18. jyyh Says:

    “3. If tropospheric warming results in enhanced water vapour (raised ispecific activity) that falls a little below maintenance of relative humidity, then in general clouds will form less easily on average and the cloud feedback will be a negative one”

    This raises the interesting question of can the solar 11-year cycle be deduced from cloud data? :-) Not that it is necessary to do so, but if it is possible, that is. One could imagine as the solar heating effect is pretty much instantaneous and it takes a while for relative humidity to rise, the rising solar activity would produce less clouds than declining solar activity. This in turn brought to my mind the old question of how and if the cloud data from weather stations’ historical data is incorporated to the initialization parameters of the climate model runs?

  19. Dana Says:

    To borrow from John Cook, borrowing from Bill and Ted’s Excellent Adventure – look, it’s the Goodyear Blimp!

    Oh sorry, were we talking about Watts? The blimp distracted me.

    Watts screwed up. That’s the point of this post. Bart pointed out the error, so did the study’s author, and even Roy Spencer pointed it out. The existence of another paper which may suggest a negative cloud feedback does not change the fact that Watts royally screwed up the reporting of this study, because he completely misunderstood (and continues to misunderstand) its contents.

    And by the way, there have been a bunch of papers since 2006 finding evidence for a positive cloud feedback. See here:

    http://www.skepticalscience.com/clouds-negative-feedback-intermediate.htm

    And the central transient climate response value is 2°C for 2xCO2, with a range of 1 to 3°C.

  20. J Bowers Says:

    CLIVAR: Publications from the Climate Process Teams (CPTs)

    How Well Do We Understand and Evaluate Climate Change Feedback Processes? Bony et al (2006) (review PDF)

    Mechanisms of Low Cloud–Climate Feedback in Idealized Single-Column Simulations with the Community Atmospheric Model, Version 3 (CAM3). Zhang (2008) (PDF)

    Hockey Schtick (at their blog) — “Two recent findings of the cloud CPT:…

    I guess that means geologically recent, as in, during the Holocene.

  21. Bart Says:

    Chris,

    Your thought experiment on how RH controls cloud formation has certain merit I think, but it is probably too simplistic in practice, because besides RH there are other factors that influence cloud cover (e.g. atmospheric dynamics). It’s a good and not easily answered (at least by me) question though.

  22. Bart Says:

    Hockey Schtick’s lauding of modeling results when they suit his preconceptions and lashing out to models when they don’t (his blog offers plenty of examples of the latter), makes Steve Mosher’s observation (quoted at the end of my post) particularly apt again.

  23. dorlomin Says:

    In all the years he has been blogging I dont think he has learnt any science. He has very little ability to understand much of what he posts (his Joe Bastardi effort a month ago the case in point) yet is blissfully convinced he is on the vanguard of a revolution in climate thinking.

    Vanity and gullibility are a unbeatable combination.

  24. cynicus Says:

    Dolormin,

    “He [ed: Anthony Watts] has very little ability to understand much of what he posts [..] yet is blissfully convinced he is on the vanguard of a revolution in climate thinking.”

    This kind of reasoning you’re describing, where the subject is unable to recognize his own lack of understanding, is pretty common and one can see often examples of this in controversial subjects and frontiers of science. Free energy inventions come to mind as do cold fusion discoveries or climate science and many more.

    Two well known psychologists have published an iconic paper about this in 1999, although Charles Darwin aptly described the phenomenon in 1871 as:

    “Ignorance more frequently begets confidence than does knowledge.”

    WUWT seems to function as the everyday prove of their observation.

  25. Ron Cram Says:

    I am a little surprised Allan says the paper is not about cloud feedbacks when it mentions cloud feedbacks four times in the article, including in the abstract and the conclusion.

    The abstract reads: “The influence of cloud radiative effect on determining cloud feedbacks and changes in the water cycle are discussed. ”

    So is Allan now saying he did not do what the abstract says he did?

    From the body of the paper:

    “Thus, the radiative effect of changes in cloud cover or properties is highly sensitive not only to cloud type (height, optical thickness, extent) but also to the time of year and time of day at which the changes in cloud properties take place. This is of importance in assessing cloud climate feedbacks which contribute substantially to uncertainty in climate prediction (Bony et al., 2006).”

    So is he now saying he is wrong? Is he now saying the radiative effect of cloud changes does not play a role in assessing cloud climate feedbacks?

    From the conclusion: “These analyses are vital in constraining cloud feedback processes further and in linking to future changes in the water cycle (Stephens, 2005; Bony et al., 2006; John et al., 2009).”

    So is Allan now saying his analysis does not “constrain cloud feedback processes?”

    It is fine to say the Allan paper focuses on the radiative effects. It is wrong to say the paper does not say anything about feedbacks. It clearly does.

    Perhaps this paper is just a pre-print and Allan will make corrections to it prior to publication like Dessler is doing?

  26. grypo! Says:

    No, Watts uncorrected errors:

    The paper IS NOT in agreement with Spencer’s

    You CANNOT shoehorn a number for full cloud radiative forcing into a feedback equation that is outputting change due to CO2. The number there is just completely misleading. It’s unnerving that this is just left out there.

  27. chris Says:

    Ron’s comment is astonishing. As if belligerent and blatant misrepresentation of a scientific paper and the comments of its author constitute a useful contribution to the subject!

    Ron’s problem is highlighted if we take the last sentence that he presents raised hackles at, viz: Allen’s statement that:

    “These analyses are vital in constraining cloud feedback processes further and in linking to future changes in the water cycle (Stephens, 2005; Bony et al., 2006; John et al., 2009).”

    and add the directly preceding sentence from Allen’s paper:

    “In future work it would be informative to categorize these effects by cloud type further (e.g. Futyan et al., 2005) and compare with climate model simulations. These analyses are vital in constraining cloud feedback processes further and in linking
    to future changes in the water cycle (Stephens, 2005; Bony et al., 2006; John et al., 2009).”

    So yes Ron, Allen’s paper doesn’t “constrain cloud feedback processes”, but “future work” of the sort he describes may well help to do so. Not sure it could be any simpler (the comprehension, I mean, if not the science).

  28. Ron Cram Says:

    Chris,
    I am afraid you are confused. You seem to think that because Allan talks of the need for future studies that the present study does not contribute to the issue. Actually, it is quite common for researchers to report on an investigation and then in the conclusion say that more study is needed. In fact, guiding future research is part of the goal of a research paper. Allan is not saying his study is the final word on cloud feedbacks, but he is clearly saying the radiative issue impacts feedback estimates.

    Take this portion from the conclusion:

    Exploiting satellite measurements and combining them with NWP models initialized through assimilation of available observations enables the effect of clouds on the Earth’s radiative energy balance at the surface and within the atmosphere to be quantified for the present day climate. Consistent with previous results (Ramanathan et al., 1989; Su et al., 2010), the cloud radiative cooling effect through reflection of short wave radiation is found to dominate over the long wave heating effect, resulting in a net cooling of the climate system of −21 Wm−2.

    The first sentence discusses radiative energy balance, the main topic of the paper. The second sentence says the radiative cooling effect dominates over the long wave heating effect. The long wave heating effect is the mechanism by which positive feedback is supposed to happen. In other words, the theory says CO2 will raise temperature and increase cloud cover; water vapor in the clouds will increase warming. Allan is saying the cooling effect of clouds during the day dominates over the warming effect of clouds at night.

    So, again, how can Allan possibly say his paper does not have anything to do with cloud feedback? It is a non-sensical claim. Certainly the paper is mainly about the radiative effect, but Allan highlights in the abstract and the conclusion how this changes estimates of cloud feedback.

  29. chris Says:

    Ron, why don’t you just read what Allen actually said (which I’ll reproduce here):

    “I was surprised that this paper was linked to cloud feedback since, as you mention, it attempts to quantify the well known influence of cloud on Earth’s radiation budget (at the top of the atmosphere, at the surface and within the atmosphere and also during day and night) and does not attempt to diagnose cloud feedback.”

    and re-read Bart’s top “article”, and the we wouldn’t have to have a truly tedious discussion where you engage in false precis to pursue a misrepresentation.

  30. Eli Rabett Says:

    In other words, Allen’s work can contribute to future cloud feedback studies, but itself does not deal with them. Simple enough?

  31. sharper00 Says:

    The uncertainty monster roars again! Hopefully scientists and skeptics can work together to resolve the issue over whether the paper does or does not deal with cloud feedbacks.

    The scientists (especially Spencer and Allan) clearly need to better represent the uncertainty around their conclusions and not simply dismiss skeptics but work with them in order to better understand the implications of Allan’s work and how it connects to Spencer’s.

    This will probably take many years so in the meantime it’s best to do nothing.

  32. Rattus Norvegicus Says:

    M,

    Indeed, work does continue on SP-CAM:

    http://www.atmos.washington.edu/~mwyant/4xCO2.submitted.pdf

    The conclusions are, um, tentative to say the least and much work remains to be done.

  33. Paul Kelly Says:

    Probably wrong, but here goes. Clouds are a negative forcing. The new paper sets the forcing a bit higher than previous papers. Clouds are also a feedback whose sign is the subject of debate. Spencer says clouds do what they do to some extent independent of changes in temperature. Dressler et al strongly disagree. Corrections please.

  34. willard Says:

    sharper00,

    If you don’t mind, I posted your last comment:

    http://neverendingaudit.tumblr.com/post/10485589190

  35. Jason Miller Says:

    I find it ironic that the title was changed to “New peer reviewed paper: clouds have large negative cooling effect on Earth’s radiation budget”. Negative cooling means heating while negative heating means cooling. I realize that cold is defined as the lack of heat and that there is really no such thing as cold, just the lack of heat. But linguistically, heat is commonly defined in a bipolar manner, such as hot and cold.

  36. Ron Cram Says:

    chris Says:
    September 21, 2011 at 18:17
    Ron, why don’t you just read what Allen actually said (which I’ll reproduce here):

    “I was surprised that this paper was linked to cloud feedback since, as you mention, it attempts to quantify the well known influence of cloud on Earth’s radiation budget (at the top of the atmosphere, at the surface and within the atmosphere and also during day and night) and does not attempt to diagnose cloud feedback.”

    Contrary to what Allan wrote, this paper is clearly linked to cloud feedback as I have quoted the paper above. It is true that Allan sought to quantify the effect of clouds on radiation budget. He does not attempt to quantify the effect of clouds on feedback, but contrary to his statement his paper is clearly “linked to cloud feedback.”

    He uses the term cloud feedback four times in the paper and it was important enough for him to mention cloud feedback in both the abstract and the conclusion.

    I don’t know what Allan is denying that he linked the effect of radiation to feedback, but he clearly did.

  37. Ron Cram Says:

    Eli Rabett Says:
    September 21, 2011 at 18:51
    In other words, Allen’s work can contribute to future cloud feedback studies, but itself does not deal with them. Simple enough?

    Eli,
    Certainly that is a simple concept. The problem is that it is not true. Allan does not attempt to quantify cloud feedback, but he certainly links radiation to feedback. Simple enough?

  38. sharper00 Says:

    Ron Cram,

    “He uses the term cloud feedback four times in the paper and it was important enough for him to mention cloud feedback in both the abstract and the conclusion.”

    You’ve used the term “cloud feedback” 16 times on this post alone, perhaps even more elsewhere. Therefore your comments are at least 4 times as much linked to cloud feedback as Allan’s paper.

  39. Bart Says:

    Ron,

    Since you agree with Allan that his paper does not quantify cloud feedback, what is it exactly that you are claiming? That it is somehow “linked to” climate feedback?

    The part you quote from the paper doesn’t say what you think it does. Your interpretation

    In other words, the theory says CO2 will raise temperature and increase cloud cover

    is incorrect. The theory doesn’t (and nor does this paper) say anything of the sort.

  40. grypo! Says:

    Watts has amended the post appropriately which is a relief. Although I’m confused by “~1.2 W/m2 values are correct”. Does anyone know he means by that? Does he mean a number from Spencer’s work?

  41. sharper00 Says:

    “Although I’m confused by “~1.2 W/m2 values are correct”.

    According to the strike-through section it’s what he thinks is the figure for a doubling of C02.

  42. M Says:

    Watts has “corrected” his post. After one strikeout, he offers this explanation: “While the -21wm2 and ~1.2 W/m2 values are correct, the comparison is wrong, and it is my mistake. The values are Top of Atmosphere and Surface, which aren’t the same.”

    Except that this isn’t a TOA/Surface confusion issue, it is the difference between a change of forcing (eg, +1.6 W/m2 from CO2) and the existing forcing from a substance (eg, -21 W/m2 for clouds, or whatever the total, large, W/m2 forcing from CO2 is). As well as the confusion between forcing + feedback.

    Also, the 1.2 W/m2 I think comes from Monckton-logic: I think the logic goes somewhat like this: “Temperature change = forcing * climate sensitivity. I think that feedbacks are neutral: so rather than a climate sensitivity of 3, it is more like 1. But I can just take that factor of one third out of the climate sensitivity and apply it to forcing instead, so instead of 3.7 W/m2, it is 1.2 W/m2″. (Note: I do not claim to understand Monckton-logic. My brain can barely handle repeating it without melting down into mush.)

  43. M Says:

    Oh, sorry, I see I was mistaken, and the 1.2 may indeed be surface forcing, as described in the top post. Or maybe not. Who knows what goes through the Watts-brain.

  44. Bart Says:

    I was confused by the 1.2 W/m2 CO2 doubling as well, since it’s more often given as 3.7 or 4 W/m2. The latter is the (most commonly used) TOA forcing, and the former is the surface forcing indeed.

    The more important reason why this comparison fails, however, is that the -21 refers to the total effect of all clouds, whereas the 1.2 does not refer to the total effect of all CO2, but rather to a doubling. Different beasts.

  45. grypo! Says:

    Oh, okay, I see, in the amended version the -1.2 is not a result of any calculation by Watts but is the actual net cloud forcing of the surface radiation budget from the paper. Mystery solved.

  46. Bob Brand Says:

    Sigh…

    Watts still seems confused about two separate issues:

    1) the difference between TOA Radiative Forcing and the resultant Surface forcing, caused by a doubling of CO2;

    2) the difference between the ‘steady state’ energy budget (the -21 W/m^2 as presently caused by clouds) and the change in the energy budget (the forcing) by e.g. a doubling of CO2. *If* you want to compare these numbers at all, AT LEAST you ought to take both at TOA or both at the surface!

    About the first issue:

    A doubling of CO2 causes a 3.7 W/m^2 forcing (less energy out) at the Top-of-Atmosphere (more precisely, at the tropopause). However, that *does* work out to about an extra 1.2 W/m^2 at the surface. This has been described by the IPCC in AR4 WGI Chapter 2 figure 2.23, in two separate forcing graphs for TOA and Surface:

    http://www.ipcc.ch/publications_and_data/ar4/wg1/en/figure-2-23.html

    (Note: the caption contains an error – please read erratum 208 here: http://www.ipcc.ch/publications_and_data/ar4/wg1/en/errataserrata-errata.html)

    An excellent explanation about the difference between TOA and surface forcings can be read at Science of Doom’s place:

    http://scienceofdoom.com/2011/09/02/radiative-forcing-and-the-surface-energy-balance/

    This had me mightily confused as well, until I studied SoD’s explanation…

  47. Bob Brand Says:

    Ah… And Bart points to a third – separate – confusion:

    The more important reason why this comparison fails, however, is that the -21 refers to the total effect of all clouds, whereas the 1.2 does not refer to the total effect of all CO2, but rather to a doubling. Different beasts.

    That is number 3, then,

  48. Steven Mosher Says:

    Thanks Bart.

    Now perhaps we can get some constructive engagement on the issue that Troy found with Dessler’s paper.

    See the CA post.

  49. Deech56 Says:

    >willard Says:

    >September 21, 2011 at 20:13

    >sharper00,

    >If you don’t mind, I posted your last comment:

    OT, but imagine my delight when while searching the net for something I wrote, I found my laconic comment to TF honored by a mention on NeA.

  50. willard Says:

    Deech56,

    Here you go:

    http://neverendingaudit.tumblr.com/post/10497834617

  51. Tom Says:

    Deech 56, enjoy your 15 minutes of blogorama claim to fame. Laconic? Hardly.

  52. Ron Cram Says:

    Bart,

    Perhaps I am mistaken but it is my understanding the computer models generally show clouds to be a positive feedback to rising temps. True or false?

    It is also my understanding the models show increased temps result in greater cloud cover. True or false?

  53. Rattus Norvegicus Says:

    Ron,

    Current models generally show a small positive feedback from clouds in a warming climate. However, this feedback is generally statistically indistinguishable from 0. See Dessler 2010 for a table which lays out the various cloud feedback values from a selection of models.

    Also a change in cloud cover is not necessary for a change in feedback, merely a change in the distribution of cloud species.

  54. Bart Says:

    Bob,

    I think your number 2 refers to the same problem as what I said. Different ways of saying the same thing.
    I.e. there’s not a number 3.

  55. Ron Cram Says:

    I see Rattus has answered my question rather than Bart. Fine.

    The Dessler paper is looking at clouds over the past decade, not the prediction of models over the next 100 years. Since we did not have a warming world over the last decade, clouds could not act as a positive feedback. AR4 would is a better reference for model predictions over the time period we are discussing.

    AR4 admits there is uncertainty with clouds as some of the models have varying results. Generally speaking, in a warming climate (the only kind possible with rising atmospheric CO2 according to the models) the models show both an increase in cloud cover and a positive feedback.

    Allan’s paper attempts to quantify cloud forcing and not cloud feedback. In order to calculate cloud feedback, he would have to estimate the magnitude of change in cloud cover and the sign of the change as well as the change in cloud species.

    However, Allan’s paper clearly acknowledges that his forcing calculation will impact feedback estimates in the futures. He highlights this fact in both the abstract and the conclusion. If the models cited in AR4 are correct and a warming world increases cloud cover, then cloud feedback will be negative – quite possibly strongly negative. If the models are wrong, then the dangerous positive feedback goes away.

    Anthony’s statements were not correct, but Allan’s statements that his paper does not link forcing and feedback is not true. I do not understand why he would make it.

  56. Bart Says:

    Gotta admit Judith Curry is a good debater. Her reply to Ron Cram’s comment that this paper is about feedback (which he made here, at WUWT and at CE) is

    “He [Allan] is discussing forcing. These variations are of relevance to cloud climate feedbacks. Sort of like saying a rainfall paper is about farming if the author says rainfall is relevant to farmers.”

  57. Ron Cram Says:

    Bart,
    Kind of a straw man there Bart. Dr. Curry was not addressing something I wrote but something written by Bruce.

    To me she wrote: “The paper has a few comments on feedbacks, that is very different from the paper being about feedbacks or providing any conclusions about feedbacks.”

    Her comment is perfectly true. But I never said the paper was about feedbacks or provided conclusions about feedbacks. I specifically said the paper did not attempt to quantify feedback. But I also pointed out that Allan’s statement that forcing and feedback are not linked is untrue. In fact, the link is so important Allan comments on it in both the abstract and the conclusion.

  58. Bob Brand Says:

    Bart,

    You’re right in your comment at 10:19 – there are ‘only’ two confusions at work.

    Now that I’m rereading my comment from 23:42, it doesn’t make sense to compare forcings at the surface anyhow. As SoD explains via a quote from Ramanathan:

    ..Manabe & Wetherald’s [1967] paper, which convincingly demonstrated that the CO2-induced surface warming is not solely determined by the energy balance at the surface but by the energy balance of the coupled surface-troposphere-stratosphere system.

    The underlying concept of the Manabe-Wetherald model is that the surface and the troposphere are so strongly coupled by convective heat and moisture transport that the relevant forcing governing surface warming is the net radiative perturbation at the tropopause, simply known as radiative forcing.

    The 1.2 W/m² at the surface is only the CO2 direct radiative heating down there – while the 3.7 W/m² is the total radiative forcing deposited below the tropopause. The balance of energy (3.7 – 1.2) W/m² is absorbed within the atmosphere, between the tropopause and the surface.

    The only useful comparison would be to compare forcings (changes in the energy budget) at the tropopause.

  59. Bart Says:

    That’s right, Bob.

    Watts probably chose the 1.2 number because it is smaller, so it made the importance of CO2 (doubling) appear even smaller when nonsensically comparing it with the total (reference) effect of clouds.

  60. chris Says:

    Ron, it’s really tedious to have to keep correcting false precis which upon repetition starts to look like trolling. Here’s what Dr. Allan said:

    ““I was surprised that this paper was linked to cloud feedback since, as you mention, it attempts to quantify the well known influence of cloud on Earth’s radiation budget (at the top of the atmosphere, at the surface and within the atmosphere and also during day and night) and does not attempt to diagnose cloud feedback.””

    He said this in response to the observation that a blogger mistakenly directly linked his estimate of the effect of clouds on earth’s radiation budget to the cloud feedback as if the total effect corresponded to the feedback.

    When you assert “But I also pointed out that Allan’s statement that forcing and feedback are not linked is untrue.” you are entirely misrepresenting Allan’s statements and paper. He simply doesn’t state that at all. In fact he makes it very clear what he means, what his estimate of total cloud effect corresponds to, and how subsequent work that addresses the temperature response of clouds according to cloud type might allow the cloud feedback to be better addressed. I don’t understand why we can’t simply address what Dr. Allan says in his own words, rather than fiddle about with the meaning in order to… well, I can’t fathom what you purpose is…

  61. Ron Cram Says:

    Chris,
    Allan wrote “I am surprised to see that this paper was linked to cloud feedback…” The paper was about cloud forcing. Allan clearly linked cloud forcing to cloud feedback in the abstract and the conclusion. The two most important parts of a paper are the abstract and the conclusion. You don’t put extraneous stuff in there. You focus on the most important aspects of the study. The abstract is the way you sell readers to read your paper. The conclusion is the way you sell researchers to cite you paper. These two sections are written with the utmost care.

    Let’s look at this another way. What do you think Allen means when he is talking about feedback in the abstract and conclusion? Does the abstract promise something the paper does not deliver? Is the conclusion warranted by the body of the paper?

  62. M Says:

    “If the models cited in AR4 are correct and a warming world increases cloud cover, then cloud feedback will be negative – quite possibly strongly negative.”

    You do realize that all the AR4 models, which predict a positive cloud feedback, already show a negative net cloud forcing? Therefore, your logic that negative cloud forcing implies negative feedback is flawed.

  63. chris Says:

    Yup, as we’ve seen, a blogger made the rather astonishing blunder of confusing Dr. Allan’s estimate of the total cloud effect on Earth radiative budget with a measure of the cloud feedback which Dr. Allan made no analysis of whatsoever in his paper (that’s what this entire thread is about and it’s difficult to understand your inability to grasp this). Dr Allan pointed out that he was surprised at this blunder since, as he says very clearly, his paper “does not attempt to diagnose cloud feedback”

    Dr. Allan’s words convey his meaning without ambiguity.

    Don’t see the point of your homilies re paper construction. Allan refers in the conclusion to radiative-convective balance and the influence of different cloud types, and how it might be informative in future work to address these to further constrain cloud feedback processes. He refers to this in the abstract. What could be more straightforward?

  64. Rattus Norvegicus Says:

    Ron,

    You specifically asked about feedback effects, so I pointed you to an easy to find source. Then you go and confuse feedback and forcing again. Are you ever going to figure this out?

  65. Ron Cram Says:

    M,

    You write: “You do realize that all the AR4 models, which predict a positive cloud feedback, already show a negative net cloud forcing? Therefore, your logic that negative cloud forcing implies negative feedback is flawed.”

    Your comment would be interesting if 100% accurate and if the net radiative forcing in the AR4 models had the same level of cooling effect as estimated by Allen. Here is a quote from AR4.

    “Figure 10.11a shows globally averaged cloud radiative forcing changes for 2080 to 2099 under the A1B scenario for individual models of the data set, which have a variety of different magnitudes and even signs. The ensemble mean change is –0.6 W m–2. This range indicates that cloud feedback is still an uncertain feature of the global coupled models (see Section 8.6.3.2.2).”

    By the way, do you see how AR4 links cloud radiative forcing to cloud feedback in this paragraph?

  66. J Bowers Says:

    2010 updates to model-data comparisons

    Just saying.

  67. Robert Murphy Says:

    Ron,
    “Allan clearly linked cloud forcing to cloud feedback in the abstract and the conclusion.”

    And clearly one needs to know what the magnitude of cloud forcing is in order to accurately describe the magnitude of a possible feedback. It doesn’t by itself, however, tell you what the *sign* of the feedback is going to be. Allan’s paper does not say what sign the possible feedback is. That is not what was examined. That is what Allan said and that is what the paper says.

  68. cRR Kampen Says:

    Guess my remark didn’t make it because it must be true: that the USA are already covered by at least a mile of blue ice.

  69. Bart Says:

    cRR Kampen,

    I just check the spam folder, but can’t find your comment there, nor have I moderated it. Feel free to re-submit.

  70. cRR Kampen Says:

    O Bart sorry – I meant I posted that remark on WUWT where it didn’t make it through the censor. The remark, that is, that ‘we must all be living beneath a mile of ice cap’ – which would be the case if we lost like 21 Watts/square meter since, whenever, due to -whatever-, as Anthony Watts seemed to suggest.

  71. Rob Dekker Says:

    Bart,
    Thanks a lot for making that post at WUWT. Spencer’s confirmation of your post there triggered Watts to rewrite the post entirely. Without your post there, it would have been another contrarian orgie.

    Got another one of the cloud forcing/feedback confusionists on WUWT, from Heartland’s Willis Eschenbach :

    http://wattsupwiththat.com/2011/10/11/wrong-again/#comment-766461

    Feel free to join there. I’m already at the point where Eschenbach fails to post any defense to his obfuscating and misleading post.

  72. Bart Says:

    Rob,

    Too many things to do, too little time.

    Thanks for the heads up though.

  73. Rob Dekker Says:

    Hoi Bart,

    Eschenbach’s post is getting interesting : After I pointed out the mistakes that Eschenbach made and another poster started questioning Eschenbach’s scientific integrity and competence, Eschenbach snipped a large number of “inconvenient” comments.

    Even better, in my last response to his latest comment :

    http://wattsupwiththat.com/2011/10/11/wrong-again/#comment-769559

    I push him a bit harder on the inconsistency between his definition of cloud forcing and his use of the ERBE data, and … my comments got tossed out.

    Luckily I made a snapshot of the (two-part) post I made before it got eliminated :

    I posted these links also at WUWT, with a re-post of my comment.

    The main problem is that Eschenbach uses an (incorrect) definition of cloud forcing which does not match the definition used for ERBE data, and he is confusing cloud forcing with feedback.

    Eschenbach knows he made mistakes but does not want to admit them. He tried bullying me away (ad hominems en zo), but when that did not work he simply eliminates my comments.

    Remember this is the same guy who is trumpeting his findings on Heartland presentations and E&E and the guy who declared that climate scientists “are guilty of egregious and repeated scientific malfeasance”, and “Your response is to stick your fingers in your ears and cover your eyes”.

    Pot en ketel en zo.
    Ik heb het niet zo op hypokrieten.

    Feel free to join in (especially if my comments do not come through even in the re-post).

    Rob

  74. cRR Kampen Says:

    Rob, ‘The Cardinal of AGW’ (so titled by Watts am I) will not join in, because at WUWT facts are taboo.

    What those people do is worse than mere hypocrisy. You are looking at evil. “… the guy who declared that climate scientists “are guilty of egregious and repeated scientific malfeasance”, and “Your response is to stick your fingers in your ears and cover your eyes”.” is playing a tactic. Very consciously.

  75. Bob Brand Says:

    Hoi Rob Dekker,

    You’ve made some excellent (deleted…) comments, at that particular thread at WUWT. Confusion seems to reign there and I can only guess Watts is consciously promoting confusion and obfuscation.

    It is a perverted kind of ‘science journalism’ where Watts aims at maximising the confusion, so people will throw up their hands in despair: “it’s all too complicated!” Hypocrisy indeed.

    Please keep fighting the good fight for clarity and understanding.

  76. Marco Says:

    Bob, it would be strange if Watts is consciously promoting confusion and obfuscation. Remember that Roger Pielke Sr was adament that Anthony is devoted to the highest level of scientific robustness!
    (in case any one doubts me, just google the part “…is devoted to the highest level of scientific robustness.”).

  77. Bob Brand Says:

    Marco, in that case I must have been totally and utterly mistaken. Who could argue with that! Actually, I’ve always wondered what ‘robustness’ means, but now I know. I did have something else in mind, though… ;-)

  78. Rob Dekker Says:

    Bob Brand, thanks for the compliment.
    WUWT did let my post go through after I presented the screenshots from above. That’s now the third time this helps, so here is a lesson to be learned : if you post a controversial comment on a confusionist’s blog, always make a screenshot.

    Eschenbach, in his response, went into denial mode. Classic. You point out that “1+2-1==1″, and they will argue straw mans until your give up. Instead, I and pointed out the contradictions in his own statements. See how that goes. That’s the nice thing about confusionists : they always contradict themselves when they are on the defense. And there are always plenty of statements they make that are ludicrous enough to expose.

    cRR Kampen : ‘The Cardinal of AGW’ (so titled by Watts am I) will not join in, because at WUWT facts are taboo. Sorry to hear that. I’m having lots of fun, and I wish you would set aside your preconceived beliefs, and recognize that your creativity in posting comments are not just helpful, but essential in exposing hypocritical bigots like Eschenbach.

  79. Rob Dekker Says:

    Well, I just made a fool of myself. 1+2-1=2 and not 1. At least we can all (including me) have a good laugh at my silly analogy…

  80. Watt about the Cloud Radiative Effect? | Wotts Up With That Blog Says:

    […] cancel any anthropogenic forcings. This was nicely rebutted by Bart Verheggen in a post called confusing the net cloud effect with a cloud feedback: Very different beasts. Basically, the figure shows the net radiative forcing of clouds (measured by CERES) relative to […]

  81. Watt about the Cloud Radiative Effect? | And Then There's Physics Says:

    […] cancel any anthropogenic forcings. This was nicely rebutted by Bart Verheggen in a post called confusing the net cloud effect with a cloud feedback: Very different beasts. Basically, the figure shows the net radiative forcing of clouds (measured by CERES) relative to […]

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