ATTP, This is a discussion of clouds

ATTP,
This is a discussion of clouds precisely because they are a very important part of the climate puzzle.
“Clearing Clouds of Uncertainty by Mark Zelinka, David Randall, Mark Webb and Steven Klein. Their commentary is really a summary of our recent understanding and – as illustrated by the figure on the right – they conclude that the evidence is converging on the cloud feedback likely being positive.”
From FAR 1990 positive but cloud feedback represented the largest source of uncertainty in climate sensitivity among atmospheric models.
To SAR Second Assessment Report; 1995), more climate models were predicting the mass of cloud liquid and ice, and generally finding negative cloud opacity feedbacks, albeit of widely differing strengths. The report concluded that it was not possible at that time to judge the sign of the net cloud feedback.
TAR 2001 …the sign of [the cloud] feedback remains unknown.
AR4 2007 it is not yet possible to assess which of the model estimates of cloud feedback is the most reliable
AR5 “The sign of the net radiative feedback due to all cloud types is…likely positive”
BUT Cloud opacity feedback “is highly uncertain”

You say,
“I don’t really see why I should be expected to post comments that are certain, but wrong.”
I repeated a fact, “Averaged globally and annually, clouds cause cooling ” from the article overview. I said in view of this,
“any increase in cloud cover should have a stronger negative than a positive effect.”
The current point of view says this is likely wrong but admit to high uncertainty still in areas like cloud opacity. There is a threefold variation in the global sensitivity parameter FAR 1990 due to
differences in cloud feedback.
This is a most important discussion which is not yet settled and needs open discussion.

 

 

  • angech says:

    Your comment is awaiting moderation.

    Izen
    The article overview states
    “Averaged globally and annually, clouds cause 18W/m2 of cooling relative to a hypothetical
    cloud-free Earth. This is the net result of a 46 W/m2 cooling from reflecting sunlight back to space (an albedo effect) partly offset by a 28 W/m2 heating due to reduced terrestrial radiation emitted to space (a greenhouse effect). The net planetary cooling provided by clouds is roughly five times as large as the planetary heating from a doubling of CO2.”
    So even though the albedo effect usually works only half the time [there is a minuscule effect for moonlight etc] it produces much more cooling in that 12 hour period than a whole 24 hours of
    cloud GH positive effect.

    “Why would the albedo negative effect be larger than the cloud GH positive effect if they increase”

    Because it is positive with more clouds. As stated above in a cloud free earth it would be 18W/M energy warmer. So if there is no effect with no cloud and 18 W/m2 cooler with current cloud it stands to reason that with more cloud from global warming there should be an increase in the cooling effect.

    The authors state,
    “The overall cloud feedback is actually the aggregate effect of several individual cloud feedbacks, commonly separated into three components: cloud amount, cloud altitude,and cloud opacity feedbacks” “Nearly all current climate models simulate an overall positive cloud feedback ”

    Despite Victor’s assertion he is referring to a decreasing amount of ice and here we are referring to an increasing amount of water vapor. Which up to this point in the climate causes cooling of a known degree. The models simulate and argue for positive feedbacks from clouds from this point on without acknowledgment of how the clouds caused cooling in the first place.
    It appears to be models all the way down with “weak further support from observations”

  • paulski0 says:

    angech,

    ATTP ” they conclude that the evidence is converging on the cloud feedback likely being positive.”
    This comment must therefore be directed at the increase in clouds, not their current status as the article demonstrates an original strong negative feedback (18W/m2).

    Positive feedback in this case refers to enhancement of warming rate due to changes in cloud behaviour in response to temperature increase.

    The -18W/m2 figure refers to the net present day radiative effect of clouds, relative to a hypothetical Earth without clouds (all else remaining the same). I guess you could argue that clouds wouldn’t exist at 0K temperature, so the “warming” to present day 288K temperature has resulted in a -18W/m2 negative feedback, but the temperature at which clouds can form is so far below 288K that it makes no sense to extrapolate a continuing increase in cloud amounts with temperature.

    It’s actually fairly easy to dispel any “intuitive” idea that cloud amounts must increase with temperature at present day levels by looking at seasonal cycles. Certainly in the Northern Hemisphere mid-latitudes, Summers are considerably less cloudy than Winters.

    Putting into numbers AR5 concluded with a best estimate of 0.6W/m2/K for net cloud feedback. That means a 1K warming from now would result in a change from -18W/m2 to -17.4W/m2 cloud radiative effect. Don’t know if it’s been done, but might be interesting to produce a diagram giving some idea of how Earth’s net cloud radiative effect, total cloud fraction, low cloud fraction varies with temperature from 0K up to 300K.

  • Magma says:

    That’s a nice commentary/short review in Nature Climate Change, open-access and well worth reading.

    I have the strong impression that much of the contrarian opinion on cloud feedback originates from the fact that when one is outdoors on a sunny day and a cloud passes in front of the sun, ground level insolation and perceived temperature quickly drop. Coupling this to the undeniable facts that it still gets cold in mid-latitude winters and major coastal cities are still above sea level, it is but series of short logical steps to the “all scientists are liars and climate change is a hoax to bring about one world government” held by many of these rather dim individuals.

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  • Eric Michel says:

    Just a quick note of thanks. Not nearly well versed enough to comment on the material, but enjoy reading and learning bits and pieces.

    Eric

    On Sat, Oct 7, 2017 at 3:02 PM, …and Then There’s Physics wrote:

    > …and Then There’s Physics posted: “A few years ago I posted a video by > Andrew Dessler that was discussing whether or not Equilibrium Climate > Sensitivity could be less than 3oC. The bottom line was that the best > estimate for ECS is about 3oC. Given that we’re quite confident about water > v” >

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  • angech,
    I don’t like having to justify moderation decisions, but I will illustrate this just this once. You said

    SInce the first effect is primary ie albedo and since this effect is negative any increase in cloud cover should have a stronger negative than a positive effect.

    Well, this is wrong, as others have indicated. Yet, you said it as if you understood this well enough to make a strong claim. I don’t really see why I should be expected to post comments that are certain, but wrong.

    Your comment is awaiting moderation.

    Overview of #cloudfeedbacks in the 5 IPCC reports & beyond [link].
    An interesting blog on this over at ATTP. “A bit more about clouds”
    This is a discussion of clouds precisely because they are a very important part of the climate puzzle.
    “Clearing Clouds of Uncertainty by Mark Zelinka, David Randall, Mark Webb and Steven Klein. Their commentary is really a summary of our recent understanding and – as illustrated by the figure on the right – they conclude that the evidence is converging on the cloud feedback likely being positive.”
    From FAR 1990 positive but cloud feedback represented the largest source of uncertainty in climate sensitivity among atmospheric models.
    To SAR Second Assessment Report; 1995), more climate models were predicting the mass of cloud liquid and ice, and generally finding negative cloud opacity feedbacks, albeit of widely differing strengths. The report concluded that it was not possible at that time to judge the sign of the net cloud feedback.
    TAR 2001 …the sign of [the cloud] feedback remains unknown.
    AR4 2007 it is not yet possible to assess which of the model estimates of cloud feedback is the most reliable
    AR5 “The sign of the net radiative feedback due to all cloud types is…likely positive”
    BUT Cloud opacity feedback “is highly uncertain”

    The article overview states
    “Averaged globally and annually, clouds cause 18W/m2 of cooling relative to a hypothetical cloud-free Earth. This is the net result of a 46 W/m2 cooling from reflecting sunlight back to space (an albedo effect) partly offset by a 28 W/m2 heating due to reduced terrestrial radiation emitted to space (a greenhouse effect). The net planetary cooling provided by clouds is roughly five times as large as the planetary heating from a doubling of CO2.”
    The albedo effect works only half the time [there is a minuscule effect for moonlight etc] yet it produces much more cooling in that 12 hour period than a whole 24 hours of cloud GH positive effect.

    “The overall cloud feedback is actually the aggregate effect of several individual cloud feedbacks, commonly separated into three components: cloud amount, cloud altitude,and cloud opacity feedbacks” “Nearly all current climate models simulate an overall positive cloud feedback ”

    Too much information. The link I had from Victor Venema has gone down but the article could have said Cloud Albedo negative effect had x5 the effect of GHG doubling. That observational was very weak and most of the proof came from climate model simulations which duh incorporate positive cloud feedbacks in the first place.

    To the amateur eye if going from no clouds to what we have causes 18 W/m2 cooling any further cloud increase should cause more cooling.
    Miraculously this article has found a new physical fact on model evidence. That clouds cool the earth as it goes to a surface temp of 14 degrees and then at that precise point start to warm the atmosphere up.
    Not on the basics of testable physics.
    I do not see a kettle of water cooling down as you get past a certain point in heating it up.
    But on the basis of models, observationally wrong and incorporating the very features the claim to be looking for.
    Science, shame.

 

Jai at ATTP

angech says:
Your comment is awaiting moderation.
October 6, 2017 at 9:44 am

Jai John Mitchell says:
“The range of estimates of ECS on the low-end are dominated by observational estimates.”
Long time reader of your comments at ASIB.
Says it all really does it not?
Unreliable observational estimates are no match for real time paleological proxies and centennial-based feedbacks in models
The lower end range is not applicable as it only exists in an observational world.
Admire the effort and work that you have always put in to your comments and thanks for sharing those referrals above.
ECS range is around 3.0 at this site as befits IPCC, you can try to push it higher, I have failed to push it lower.
angech says:
Your comment is awaiting moderation.
October 6, 2017 at 10:21 am

Everett F Sargent says:
“Well RealClimate has another post on the Millar paper 2017/10/1-5oc-geophysically-impossible-or-not/”

Thanks Everett, I do not go to RealClimate as much as I should, partly as this site keeps well abreast of it which means there is no need generally. I do read a cross section of all of the others though Stoat is quiet for long periods and Tamino is dormant at the moment.

The choice of temperature data
“the conclusion that present day temperatures lie outside of the model distribution.”
remains a problem even if resorting to
” The anomaly between observations and the CMIP5 mean temperature response to cumulative emissions is halved by repeating the Millar analysis with the GISTEMP product instead of HadCRUT.”

The role of internal variability
“Both HadCRUT and GISTEMP suggest strongly negative index values for the period 2005-2014, suggesting a potential cold bias in the warming estimate due to natural variability of 0.1?C (with 5-95% values of 0.05-0.15?C).”
Which means it is 0.2 C potential natural variability shown in just a 10 year period. Interesting to contemplate what the actual range would be in a series of a 100 decades.

The low CMIP5 compatible emissions comment suggests fallibility.
” the combined evidence of the influence of natural variability on the unforced temperature estimate, the disagreement between different observational datasets on warming level, and the uncertainty introduced by an uncertain pre-industrial temperature baseline means that we can’t be confident as the Millar paper suggests on what the current level of warming is.”

and this gem on trust in models v observations ” Alternatively, we trust the cumulative emissions number and treat the models as full proxies for reality, as was done in AR5,”

DikranMarsupial an interesting post

 

  • DM,
    “Perhaps the oldest and most basic carbon cycle canard stretches its wings again. Whether anthropogenic emissions are large or small compared with the magnitude of environmental fluxes is entirely irrelevant, what matters is whether they are large or small compared with the difference between total natural emissions and total natural uptake as that is what governs the rise or fall of atmospheric CO2 concentrations”
    Thank you for the video and the X-File? music and science with it.
    Much easier to address you after having seen that and the work you put in.
    If I can try to comment without being too antagonistic which is hard when we have differing views I would put for your consideration the following.
    I agree/understand your comment on emissions and sinks.
    1. I did not want to put up a canard.
    “The extra amount we produce is still reasonably small compared with the overall yearly carbon cycle.”
    To me has the same meaning as
    “what matters is whether they are large or small compared with the difference between total natural emissions and total natural uptake as that is what governs the rise or fall of atmospheric CO2 concentrations”
    Particularly when I add “The fact that after several [many] severe outgassing of CO2 events in the past we are still here indicates to me that the biosphere and the earth sea chemical mixes have shown the needed resilience.”
    which to me means that I took sinks into consideration.
    In the video you mention the balance of the emissions with the uptake of the natural environment but then change terms to net sinks [presumably still the environment] which for 50 years have removed half the excess CO2 claimed produced by man.
    There are at least four different natural causes for CO2 in the atmosphere. One is volcanoes. One is natural chemical. Even with no life forms anywhere but the current composition of the earth there would be CO2 in the atmosphere commensurate with dissolved CO2 in the water and calcium carbonate in the rock. The level might even be as high as 280 ppm because the third component, life forms, has a mutable create/ destroy existence.
    Here [the second] emissions /sinks as you put it are in balance, have to be in balance, no choice.
    But then you add the fourth cause, still “natural” but unwanted. Human beings adding in CO2 which is different to normal life activity.
    Once you perturb the level “artificially” you activate the chemical sinks. By your own reckoning these sinks activated at a low level of CO2 increase are capable of taking 50% extra of the excess CO2 out of the atmosphere.
    Now balance is important. As you ramp up the increase in CO2 you might [*] increase the sink capacity way beyond 50%. A bit like pH rise or fall being logarithmic.
    If you choose to attribute, for very good paleontological reasons a linear 50% rise so be it.
    If ATTP chooses to believe the sinks will become saturated and run out of puff so be it.
    I do not wish to change my belief system, sorry but I do not mind being corrected on the science if and [very often I guess] it is needed.

  • angech says:

    Your comment is awaiting moderation.

    RustneverSleeps.
    “Another “why” question: Why do you so often just make things up in your head and present them as credible “just so” (yet counterfactual) representations of well-understood real-world phenonmenon”.
    Robbie Burns answer I guess. I see your making things up in my head as thinking about things in my world. The fellow with the different hats theory [De Bono] says you need people like me [questioners] to make other people think about things more clearly which helps consolidate their real world views. Does not make one appreciate the fellow in the funny hat any better though.