Guest Post by Willis Eschenbach
This is the third in a series ( Part 1, Part 2 ) of occasional posts regarding my somewhat peripatetic analysis of the data from the TAO moored buoys in the Western Pacific. I’m doing construction work these days, and so in between pounding nails into the frame of a building I continue to pound on the TAO dataset. I noticed that a few of the buoys collect data on both shortwave (solar) radiation and longwave (infrared or greenhouse) radiation at two-minute intervals. For a data junkie like myself, two-minute intervals is heaven. I decided to look at the data from one of those buoys, one located on the Equator. at 165° East.
Figure 1. Location of the buoy (red square) which recorded the data used in this study. Solid blue squares show which of all the buoys have the two-minute data. DATA SOURCE
It was a fascinating wander through the data, and I found that it strongly supports my contention, which is that the net effect of clouds in the tropics is one of strong cooling (negative feedback).
To start with, I looked (as always) at a number of the individual records. I began with the shortwave records. Here is a typical day’s record of the sun hitting the buoy, taken at two-minute intervals:
Figure 2. A typical day showing the effect of clouds on the incoming solar (shortwave) radiation.
In Figure 2 we can see that when clouds come over the sun, there is an immediate and large reduction in the incoming solar energy. On the other hand, Figure 3 shows that clouds have the opposite effect on the downwelling longwave radiation (DLR, also called downwelling infrared or “greenhouse” radiation). Clouds increase the DLR. Clouds are black-body absorbers for longwave radiation. After they absorb the radiation coming up from the ground, they radiate about half of it back towards the ground, while the other half is radiated upwards The effect is very perceptible on a cold winter night. Clear nights are the coldest, the radiation from the ground is freer to escape to space. With clouds the nights are warmer, because clouds increase the DLR. Figure 3 shows a typical 24 hour record, showing periods of increased DLR when clouds pass over the buoy sensors.
Figure 3. A typical day showing the effect of clouds on the downwelling longwave radiation (DLR).
Once again we see the sudden changes in the radiation when the clouds pass overhead. In the longwave case, however, the changes are in the other direction. Clouds cause an increase in the DLR.
So, here was my plan of attack. Consider the solar (shortwave) data, a typical day of which is shown in Figure 2. I averaged the data for every 2-minute interval over the 24 hours, to give me the average changes in solar radiation on a typical day, clouds and all. This is shown in gray in Figure 4.
Then, in addition to averaging the data for each time of day, I also took the highest value for that time of day. This maximum value gives me the strength of the solar radiation when the sky is as clear as it gets. Figure 4 shows those two curves, one for the maximum solar clear-sky conditions, and the second one the all-sky values.
Figure 4. The clear-sky (blue line) and all-sky (gray line) solar radiation for all days of the record (2214 days).
As expected, the clouds cut down the amount of solar radiation by a large amount. On a 24-hour basis, the reduction in solar radiation is about 210 watts per square metre.
However, that’s just the shortwave radiation. Figure 5 shows the comparable figures for the longwave radiation at the same scale, with the difference discussed above that the clear-sky numbers are the minimum rather than the maximum values.
Figure 5. The clear-sky (blue line) and all-sky (gray line) downwelling longwave radiation (DLR) for all days of the record.
As you can see, the longwave doesn’t vary much from clouds. Looking at Figure 3, there’s only about a 40 W/m2 difference between cloud and no cloud conditions, and we find the same in the averages, a difference of 36 W/m2 on a 24-hour basis between the clear-sky and all-sky conditions.
DISCUSSION
At this location, clouds strongly cool the surface via reflection of solar radiation (- 210 W/m2) and only weakly warm the surface through increased downwelling longwave radiation (+ 36 W/m2). The net effect of clouds on radiation at this location, therefore, is a strong cooling of – 174 W/m2.
This likely slightly overstates the radiation contribution of the clouds. This is because, although unraveling the effect on shortwave is simple, the effect on longwave is more complex. In addition to the clouds, the water vapor itself affects the downwelling longwave radiation. However, we can get an idea of the size of this effect by looking at the daily variation of longwave with and without clouds in more detail. Figure 6 shows the same data as in Figure 5, except the scale is different.
Figure 6. As in Figure 5 but with a different scale, the clear-sky (blue line) and all-sky (gray line) solar radiation for all days of the record.
Note that the minimum (clear-sky) DLR varies by about 10 W/m2 during the 24 hours of the day. Presumably, this variation is from changes in water vapor. (The data is there in the TAO dataset to confirm or falsify that presumption, another challenge for the endless list. So many musicians … so little time …). Curiously, the effect of the clouds is to reduce the underlying variations in the DLR.
This warming due to water vapor, of course, reduces the warming effect of the clouds by about half the swings, or 5 W/m2, to something on the order of 30 W/m2.
Finally, to the perplexing question of the so-called “cloud feedback”. Here’s the problem, a long-time issue of mine, the question of averages. Averages conceal as much as they reveal. For example, suppose we know that the average cloud cover for one 24 hour period was forty percent, and for the next 24 hours it was fifty percent. Since there were more clouds, would we expect less net radiation?
The difficulty is, the value and even the sign of the change in radiation is determined by the time of day when the clouds are present. At night, increasing clouds warm the planet, while during the day, increasing clouds have the opposite effect. Unfortunately, when we take a daily average of cloud cover, that information is lost. This means that averages, even daily averages, must be treated with great caution. For example, the average cloud cover could stay exactly the same, say 40%, but if the timing of the clouds shifts, the net radiation can vary greatly. How greatly? Figure 7 show the change in net radiation caused by clouds.
Figure 7. Net cloud forcing (all-sky minus clear-sky). Net night-time forcing is positive (average 36 W/m2), showing the warming effect.
In this location, the clouds are most common at the time they reduce the net radiation the most (mid-day to evening). At night, when they have a warming effect, the clouds die away. This temporal dependence is lost if we use a daily average.
So I’m not sure that some kind of 24-hour average feedback value is going to tell us a lot. I need to think about this question some more. I’ll likely look next at splitting the dataset in two, warm dawns versus cool dawns, as I did before. This should reveal something about the cloud feedback question … although I’m not sure what.
In any case, the net cloud radiative forcing in this area is strongly negative, and we know that increasing cloud coverage and earlier time of cloud onset are functions of temperature. So my expectation is that I’ll find that the average cloud feedback (whatever that means) to be strongly negative as well … but in the meantime, my day job is calling.
A final note. This is a calculation of the variation in incoming radiation. As such, we are looking at the throttle of the huge heat engine which is the climate. This throttle controls the incoming energy that enters the system. As shown in Figure 7, in the tropics it routinely varies the incoming energy by up to half a kilowatt … but it’s just the throttle. It cools the surface by cutting down incoming fuel.
The other parts of the system are the tropical thunderstorms, which further cool the surface in a host of other ways detailed elsewhere. So the analysis above, which is strictly about radiation, actually underestimates the cooling effect of tropical clouds on surface temperature.
All the best, please don’t bother questioning my motives, I sometimes bite back when bitten, or I’ll simply ignore your post. I’m just a fool like you, trying to figure this all out. I don’t have time to respond to every question and statement. Your odds of getting a reply go way up if you are supportive, on topic, provide citations, and stick to the science. And yes, I know I don’t always practice that, I’m learning too …
w.
PS — Here’s a final bonus chart and digression. Figure 8 shows the average of the actual, observed, measured variation in total downwelling radiation of both types, solar (also called shortwave) radiation and longwave (also called infrared or “greenhouse”) radiation.
Figure 8. Changes in average total forcing (solar plus longwave) over the 24 hours of the day.
Here’s the digression. I find it useful to divide forcings into three kinds, “first order”, “second order”, and “third order”. Variations in first order forcings have an effect greater than 10% of the average forcing of the system. For the system above, this would be something with an effect greater than about seventy W/m2. Figure 7 shows that the cooling from clouds is a first order forcing during the daytime.
Variations in second order forcings have an effect between 1% and 10% of the average. For Figure 8 that would be between say seven and seventy W/m2. They are smaller, but too big to be ignored in a serious analysis. With an average value of 36 W/m2, the warming from night-time clouds is an example of a second order forcing.
Finally, variations from third order forcings are less than 1%, or less than about seven W/m2 for this system. These can often be ignored. As an example of why a third order forcing can be ignored in an overall analysis, I have overlaid the Total Radiation (red line in Figure 8) with what total radiation would look like with an additional 7 W/m2 of radiation from some hypothetical CO2 increase (black line in Figure 8). This seven watts is about 1% of the 670 W/m2 average energy flowing through the system. The lines are one pixel wide, and you can scarcely see the difference.
Which is why I say that the natural governing mechanisms that have controlled the tropical temperatures for millions of years will have no problem adjusting for a change in CO2 forcing. Compared to the temperature-controlled cloud forcing, which averages more than one hundred and fifty W/m2, the CO2 change is trivial.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
Willis, this is great stuff. Now we just need to replicate this for each latitude over a year and get a real idea of the overall cloud feedback to temperature.
My money is on -20W/m^2 or thereabouts.
Thing is, it looks like the cloud feedback to temperature is only a minor part of the story. What we really want is the feedback to solar variation, via whichever mechanisms affect it. GCR’s, solar UV/plankton aerosols, stratospheric chemistry – the complexity is bewildering. Thanks for making a good start on it. 2 minute data points, now we’re talking!
Hi Willis, I just thought I’d post the reference to the fact that its too simple (and not particularly useful IMO) to think of the IR as going up and down with more CO2 involving more jumps. This is from Pierrehumbert’s article “Infrared Radiation and Planetary Temperature”
http://climateclash.com/2011/01/15/g6-infrared-radiation-and-planetary-temperature/
“Coupled vibrational and rotational states are the key players in IR absorption. An IR photon absorbed by a molecule knocks the molecule into a higher-energy quantum state. Those states have very long lifetimes, characterized by the spectroscopically measurable Einstein A coefficient. For example, for the CO2 transitions that are most significant in the thermal IR, the lifetimes tend to range from a few milliseconds to a few tenths of a second. In contrast, the typical time between collisions for, say, a nitrogen-dominated atmosphere at a pressure of 104 Pa and temperature of 250 K is well under 10^−7 s. Therefore, the energy of the photon will almost always be assimilated by collisions into the general energy pool of the matter and establish a new Maxwell–Boltzmann distribution at a slightly higher temperature. That is how radiation heats matter in the LTE limit.”
Willis: it might help to illustrate the complexity of the relationship between the cloud radiative forcing and sea surface temperatures to do short period regressions. A thermostat is probably going to show up as the relationship between the variables changing sign at certain “thresholds”, I would think, which would illustrate the problems with the traditional approach of simply regressing the full sets of anomalies of temperature on radiation flux, as most feedback analyses have done.
In response to
Willis Eschenbach says:
September 16, 2011 at 3:39 pm
Pete says:
September 16, 2011 at 11:17 am
Mr. Eschenbach …
” Observation: As a person with many hours flying aircraft, I know that oftentimes weather system clouds are layered, perhaps 3 or 4 layers (with clear air in between) in 20 – 25 thousand feet of altitude.
Query: What, if any, effect do the several layers have on the absorptiion and return properties of cloud layers as opposed to your apparently simple illustration?
“Multiple cloud layers mean that photons will perforce be absorbed and emitted by each cloud on the way up, increasing the number of “shells” in the greenhouse.”
Browsing online, I read about a NEGATIVE greenhouse effect on Saturn’s moon Titan.
Using the greenhouse model here
http://www.geo.utexas.edu/courses/387H/Lectures/chap2.pdf
I did a few simple calculations.
When the atmosphere is transparent to incoming radiation from the sun and opaque to outgoing radiation from the planet, you get a positive greenhouse effect.
When the atmosphere is opaque to incoming radiation from the sun and transparent to outgoing radiation to the planet you get a negative greenhouse effect, as happens in some frequencies on Titan.
When the atmosphere is opaque to both incoming radiation from the sun and outgoing radiation from the earth you get a zero greenhouse effect.
Roughly 60% of earth’s surface is covered by clouds, but earth only has a 30% albedo.
That means roughly 30% of incoming radiation is absorbed by clouds- the fraction of the atmosphere below the point of absorption will have a ZERO greenhouse effect on that 30% of photons radiated from that could to the earth and back to a cloud at a similar height.
“Thus the CO2 greenhouse effect is more like running through a minefield than just shining through a single window of variable opacity.” ?
maybe more like tossing ping.pong balls in the river to speed up the flow…lol
Bart says:
September 16, 2011 at 12:16 pm
Thanks, Bart. So if everything can be seen as being caused by the initial forcing and the rest is seen as feedback, can we then say that sunshine is the forcing of Shakespeare’s sonnets and that everything else is just feedback?
You are using what I might call a classic feedback paradigm, which you understand and explain very well, although I can’t follow some parts, that’s me, not you.
I made the point in “It’s Not About Feedback“, or tried to make the point, that your classical feedback paradigm is inadequate to explain the evolution of the tropical day. The evolution of the typical tropical day involves the sequential replacement of the basic atmospheric circulation pattern. The circulation starts out weak and random. At a certain point a temperature threshold is passed, and by a process described as “self-organized criticality”, that circulation pattern is rapidly replaced by a brand new pattern involving cumulus cloud and local shallow atmospheric circulation cells around those clouds.
If the day continues to warm, the circulation pattern changes abruptly for a second time. A new self-organized pattern, which involves deep tropospheric circulation driven by spontaneously generated, mobile, warmth-quenching heat engines called thunderstorms. These function as giant independently moving air conditioning machines that cool the surface.
Now, there’s lots of ways we can seek to understand and analyze that hugely complex sequence of events.
But thinking that the whole intricate story can be reduced to a Lissajous pattern and profitably analyzed in terms of classic feedback caused by the initial sunlight striking the system?
Well, maybe … but only if we can also see Shakespeare’s odes as being caused by sunlight …
w.
coturnix says:
September 16, 2011 at 3:23 pm
Then you should spend more time outdoors at night in the winter. Anyone who does so knows that the coldest nights are the clear nights. And during a clear night, when a cloud comes over, you can feel the difference immediately.
As you should, since instead of having the cold of outer space at a temperature of 3 kelvins as a backdrop when you look up, you have a cloud at around 270 K as a backdrop when you look up.
w.
TimTheToolMan says:
September 16, 2011 at 5:12 pm
Tim, it seems you are objecting to what people (not me) call “re-radiation”. This is the incorrect idea that the CO2 molecule captures and then re-radiates a photon. I agree with you that what happens is the photon is absorbed by the GHG, and then released as thermal energy through collisions with other molecules .
In terms of whether it is useful, however, the average number of times thermal radiation is absorbed on its way to space is a factor in the math of calculating how much thermal advantage is provided by the system (and thus the surface temperature).
Let me add in passing that a whole lot of the thermal energy goes to space without ever interacting with the troposphere. It is piped their by thunderstorms. Consider a molecule of water evaporated from the surface. It rises, carrying the latent thermal energy upwards. It releases that energy in the dark heart of the cloud, where the warm air drives the chimney circulation up the middle of the thunderstorm tower to the upper troposphere.
During that whole time the thermal energy travels from the surface to the upper troposphere, it does not interact with any part of the atmosphere—not with the surface mixed layer, the lower troposphere, or the middle troposphere. It does not mixed mechanically with those layers, nor does it radiate even the slightest amount to those layers of the lower atmosphere. It took the secret passage from the surface to the upper troposphere and indeed, at times into the stratosphere itself. It did not take the radiative path.
w.
Willis writes “In terms of whether it is useful, however, the average number of times thermal radiation is absorbed on its way to space is a factor in the math of calculating how much thermal advantage is provided by the system (and thus the surface temperature). ”
Again as I understand it, once the GHG’s have initially absorbed the IR from the ground (or ocean) within the first 100m or so, only about 2% of that energy is radiated again from the pointy end of the Maxwell–Boltzmann distribution. This means the rest is transmitted through the atmosphere via “other means”
This is where I wholeheartedly agree with your emphasis on the roles of thunderstorms, the importance on the latent heat of vaporisation and so on.
Meh. This is the second time I’ve insisted on better explanations of physical processes from your excellent articles. I guess I’m even more of a stickler for understanding and conveying the detail of the process than you 😉
Willis
Willis Eschenbach says:
September 16, 2011 at 7:25 pm
coturnix says:
September 16, 2011 at 3:23 pm
To me, all this shit about ‘clouds warm earth at night’ is preposterous
/////////////////////////////////
In mid lattitudes. the difference between a clear night and a cloudy night is usually just a few degrees notwithstanding your point regarding space at 3K and clouds at 270K. The reality is that for the main part, irrespective of clouds, the atmosphere radiates at about 270K.
Clouds do not warm. They may slow down the rate of cooling. Slowing down the rate of cooling is not warming. Being less cold, is not warming.
Willis Eschenbach says: September 15, 2011 at 10:59 pm
” If for some time around noon when there are no clouds the shortwave is 1400 W/m2 …:”
This number seems just plain wrong. First of all, the radiation at the top of the atmosphere is typically ~ 1365 W/m^2. UV accounts for ~ 10% of that, and much of the UV is blocked long before reaching the ground, so that is perhaps -100 W/m^2. Even with no clouds, there must be a fair amount of humidity, and H2O vapor absorbs a noticeable fraction of the solar IR – perhaps another -100 W/m^2. I can’t see how solar energy could possibly be more than ~ 1200 W/^2 at the surface. I CERTAINLY can’t see how the solar energy could be more more than 1365 W/m^2.
Willis Eschenbach says:
September 16, 2011 at 7:17 pm
“…can we then say that sunshine is the forcing of Shakespeare’s sonnets and that everything else is just feedback?”
You can say sunshine is a forcing, but you’ve expanded the “system” now to include an awful lot of stuff. There are other forcings, too, and not all signal paths are feedback – some are feed-forward.
“But thinking that the whole intricate story can be reduced to a Lissajous pattern and profitably analyzed in terms of classic feedback caused by the initial sunlight striking the system?”
Feedback means nothing more nor less than a reaction to an input which influences how the overall system responds to that input. It is a very general concept. Feedback is not necessarily, or even usually, linear and smooth (even nonlinear systems can be linearized if they are “smooth” enough). In fact, engineers make use of bang bang controls and hard limiters and hysteresis loops and pulse width modulators and other gross nonlinearities in common mechanical and electrical feedback systems all the time. Lyapunov analysis can often be used to prove local or sometimes global stability of systems employing such elements.
But, feedback often is linear, or nearly so, in natural systems, or can be profitably modeled as such, so it’s always something to watch out for in terms of common signatures it leaves behind. Even highly discontinuous feedback can often be approximated as smooth and continuous under appropriate assumptions. For example, pulse width modulators are devices which allows us to produce a train of pulses with frequency and/or width proportional to the feedback we want to provide. If the bandwidth of the system is low compared to the pulse frequency, then we can approximate the feedback as a linear , and analyze the loop using linear control analysis techniques.
It is also possible to predict limit cycles of systems with highly nonlinear and discontinuous elements using linear systems theory by considering the first harmonic response of the element, on the assumption that higher harmonics will be attenuated in the overall feedback loop. This is called describing function analysis.
In summary re feedback: You keep using that word. I do not think it means what you think it means 😉
Tim Folkerts says on September 16, 2011 at 8:59 pm
In addition, something around 40-45% is infrared, which is, we are told, absorbed in the atmosphere and likely does not make it to the ground.
richard verney says:
September 16, 2011 at 8:57 pm
I object strongly to this semantical nonsense. It doesn’t matter what you call it. The surface at night is warmer with clouds than without. Thus we can say that the clouds make the night warmer than it would be if they were not there. In common parlance, we call that warming.
For example, we say “The room is cold, let’s close the windows to warm it up.” We don’t say “Let’s close the windows to reduce the heat loss”, that part is understood. We say “I’m cold, I’m going to put on a jacket to warm up”. We don’t say “Gosh, gotta put on a jacket to cut down my heat loss.”
People keep flogging this issue over and over, as if what we called it made the slightest difference. Here’s the bottom line.
It’s warmer with clouds than without, call it what you will. The mechanics are the same. The physics are the same. The transfer of thermal radiation energy from the cloud to the surface is the same. Call it what you will.
For me, the clouds radiate energy to the surface, the surface absorbs that energy, and the surface ends up warmer as a result. I call that “warming the surface”. It is not just slowing the heat loss. It is actively adding energy to the surface … if you have another name than “warming” to describe “actively adding energy to the surface, as a result of which the surface ends up warmer than if was without the added energy”, let me know. “Slowing the rate of cooling” doesn’t work, because it is actively adding energy, not just slowing the loss.
w.
Richard Sharpe says:
September 16, 2011 at 9:17 pm (Edit)
Thanks, Richard. You’re correct, except you’ve neglected the eccentricity of the orbit. This varies the “solar constant” from a low of about 1345 to a high of 1435 W/m2 over the course of the year. In addition, the infrared from the sun is definitely not absorbed in the atmosphere, it’s the wrong frequency (as I discussed upthread), so it is measured by the pyranometers.
It is quite possible that the sensors are occasionally reading high due to unusual meteorological conditions, and in hindsight it likely would have been better to use say the median of the top five readings as the peak, rather than a single reading. Let me see what that does … OK, that reduces the peak values down to about 1350 W/m2, which seems more reasonable. It also reduces the cloud shortwave effect slightly, bringing it down from 210 W/m2 to 185 W/m2 …
Finally, you say “… H2O vapor absorbs a noticeable fraction of the solar IR – perhaps another -100 W/m^2.” This is way high. The total atmospheric absorption of shortwave is about 70 W/m2. However, much of this is from black carbon, brown carbon, aerosols, smog, and other things in the air.
So over the ocean, I would say (and the sensors agree) that 1350 W/m2 is certainly possible. As you point out, the 1400 W/m2 I quoted before, while theoretically doable (max solar is 1435), is not that likely.
All the best,
w.
Clouds do not warm. They may slow down the rate of cooling. Slowing down the rate of cooling is not warming. Being less cold, is not warming.
——-
Same could be said about greenhouse gases – they do not warm, they only slow down the rate of cooling, but actual warming is done by the sun. it is with presence of ghg that sun can warm earth more than without. of course, real world is more complex, like during polar night poles do not freeze to -200.
However, what i want to say is that may be reported ‘warming effect’ of clouds may not be radiative after all, simply because when there are clouds, there is some sort of convection, that mixes air at the ground all the way though out boundary layer, or even with the free troposphere. Free troposphere only warms and cools very little if at all during diurnal cycle, and if there is something that prevents formation of inversion during night, clouds are most likely too a result of this mixing, and not the direct cause.
richard verney says:
September 16, 2011 at 3:14 pm
Mr Gates
I would appreciate you answering a question arising out of your comment:
R. Gates says:
September 16, 2011 at 10:15 am
“…If you agree that it is essentially a spherical transimission pattern for LW being re-emitted from a greenhouse gas molecule, then I think we may differ in our definition of what “up” means. If by “up” you mean 180 degrees from the ground, then of course far less than 50% goes “up”, and this is important as the majority of the other angles, would either be back to the ground or in some other angle tangential to the ground (but not 180 degrees from the ground)…”
///////////////////////////////////////////////////////
Do you not accept that this comment applies equally to the ‘down’ scenario? If not, why not?
It appears to me that on your reasoning,something less than 5% would go down. Should you disagree please explain why you disagree and what percentage goes ‘down’ and why that is so.
As I see matters, the logical conclusion of your comment is that when one also takes into account the effect of the horizon/curvature point (which slightly favours the upward direction), the less than 5% going ‘down’ would be less than the less than 5% going ‘up’. Should you disagrre, I would appreciation your full explanation/reasoning.
————–
I actually don’t disagree with this general reasoning if geometric concerns were all that mattered. My original question to Wills was simply to find out how he arrived at his 50% up/ 50% down figure for his cloud model. The actual circumstances of the way LW radiation interacts with both clouds and greenhouse gases is far more complicated than the simple geometric and billard ball type models we’ve been discussing. I actually think that, as far as the narrow band of the tropical oceans are concerned, Willis’ model is probably roughly correct. The problem of course is that it deals with a narrow region of the earth, and only considers one very specific and simple cloud interaction. if this was all there was on this planet in terms of cloud feedbacks I would think that we would have long ago figured out the exact sensitivity of the climate to the additional greenhouse forcing.
Bart says:
September 16, 2011 at 9:11 pm
Thanks for your thoughts as always, Bart. You miss my point, which is likely from my lack of clarity. My point is that when a natural system (humans on the earth, say, or the global climate system) reaches a certain level of complexity (Shakespear’s sonnets, say, or the unexpected emergence of a thunderstorm spitting lightning), it is no longer profitable to analyze it using classical feedback theory. We are not dealing with the kinds of systems you are used to. In climate we are looking at intricately entangled emergent systems which are continuously adapting, have thresholds for self-organized criticality which when passed lead to total reorganization of circulation, spawn independently mobile heat engines that have a lifespan and then die, systems which are often running at the edge of turbulence, and are ruled by the Constructal Law.
As a result, we need to use other analysis methods which are appropriate to that situation.
Perhaps because your background is signal processing, you are using “feedback” in a much wider, more inclusive sense than is common in the climate science field. You say, for example,
And you are correct. But when people in climate science talk about “feedback”, they are talking about plain old, garden variety feedback, what I have described as “classical” feedback, not any kind of “bang bang” feedback or pulse width modulators. This concept of feedback involves some mystical percentage by which clouds are supposed to increase the warming. It is seen as a constant, and it has nothing to do with the kinds of feedback you are (correctly) referring to.
I still say, however, that the whole concept of “feedback” is a very minor part of understanding the self-organized criticality which produces a thunderstorm. Of much more importance is the existence of a critical threshold, and the fact that when it is passed, a whole reorganization of the entire circulation regime takes place … that’s the kind of thing that “feedback”, no matter how broadly defined, can’t much help us with. Sure, feedback is in there, at every level actions have consequences, feedback is assuredly taking place … but the change in the circulation pattern or the creation of say a tornado is what rules the effects, not the feedback.
My best to you,
w.
Willis writes “For me, the clouds radiate energy to the surface, the surface absorbs that energy, and the surface ends up warmer as a result. I call that “warming the surface”. It is not just slowing the heat loss. It is actively adding energy to the surface …”
Not for 71% of the “surface” Willis. As discussed at some length, the oceans dont absorb that energy to become warmer as a direct result of that energy. There is no energy actively added in the sense it enters the ocean bulk. There are no mechanisms for it to pass further than the 10um skin. Thermodynamics doesn’t allow it. Clouds DO cool less and warm the ocean as a result though.
Your argument is more valid for the ground although its still a slowing cooling effect simply because the energy you say “warms the surface” originally came from the ground.
There are no mechanisms for it to pass further than the 10um skin
—-
Sure there is, it is mixing due to waves. Have no idea how important it may be away from hurricanes, but seas are rarely calm. Conduction may not be taken into account – water conducts heat much worse than even rock.
coturnix writes “Sure there is”
There has been a lot more discussion of this here
http://wattsupwiththat.com/2011/08/15/radiating-the-ocean/
But essentially the top of the ocean is cold and mixing it down for the next few mm cools the ocean. Conduction wont happen because where the IR is absorbed at the very top of the ocean is cooler than just below. For it to conduct, it would have to break the laws of thermodynamics…
There is a reason the skin of the ocean got this temperature gradient though and thats because the net flow of energy is upwards, not downwards. It all hinges on this “slower cooling” rather than “warming” thing that Willis and many others dont like to use.
TimTheToolMan says:
September 16, 2011 at 11:15 pm
coturnix writes “Sure there is”
There has been a lot more discussion of this here
http://wattsupwiththat.com/2011/08/15/radiating-the-ocean/
But essentially the top of the ocean is cold and mixing it down for the next few mm cools the ocean. Conduction wont happen because where the IR is absorbed at the very top of the ocean is cooler than just below. For it to conduct, it would have to break the laws of thermodynamics…
🙂
Willis chose to abandon that thread without responding to these arguments, and others we provided wich show that very little energy from DLR ‘back radiation’ is getting mixed into the ocean bulk.
Tallbloke writes “Willis chose to abandon that thread ”
Yeah but this thread isn’t really the forum to explore that further. This should be more about the clouds and I somewhat regret bringing it up here.
The second law of thermodynamics states, clearly – heat only flows from (relatively) hot to (relatively) cold, if it flew the other way perpetuum mobile of second type would be possible. This also includes thermal radiation. The NET heat transfer between a warm ocean at 20 C and a cold cloud at 5 C is ALWAYS from ocean to cloud. From which it is instantly obvious that the so called DLR can’t increase ocean’s temperature. Unless air is already warmer than water – it could probably happen at western subtropical shores, where frigid water upwells. In arctic ocean, sometimes water is so much warmer than the air that once exposed it creates thick fog through evaporating.
For some ideal ocean to warm up would mean to pump up some more energy into it. Because sun shines the same all the time, it must be DLR that heats it during warm-up phase. And yet, the net thermal emission is still from the ocean to whatever is above it. One can say that backradiation started warming the ocean, but unless you can catch and count photons with your bare hands, one can just as correctly say that suddenly ocean’s emissivity dropped, and now instead of emitting all the sun’s energy into space it retains bit of it to itself. Note, that NEVER in the process of ocean warming did net thermal radiation flew towards ocean from atmosphere. Net radiation always flows from ocean to atmosphere.
tallbloke says:
September 16, 2011 at 11:51 pm
Nonsense. I got tired of asking the following question: if the DLR isn’t absorbed by the ocean, then what is keeping the ocean from freezing? The ocean gets about 170W/m2 from solar, and it’s losing about 390 W/m2 by radiation alone, not counting sensible and latent heat loss … if DLR isn’t being absorbed by the ocean, then why isn’t it frozen?
After about the fourth time I’d heard every possible tap-dance around the subject, without anyone being able to answer my question, I said “Feh”. Tallbloke’s explanation was particularly hilarious, involving some kind of invisible mist just above the water that absorbed the DLR in some dance above the surface … but even that couldn’t explain the missing energy needed to keep the ocean from freezing.
w.