Cloud Radiation Forcing in the TAO Dataset

Guest Post by Willis Eschenbach

This is the third in a series ( Part 1Part 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.

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Stephen Wilde

“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.”
Exactly and a nice post overall. Just extend the principle to the entire globe rather than limiting it to the tropics. And acknowledge that a miniscule latitudinal shift of the surface air pressure distribution would adequately deal with the thermal effect of more CO2. We would not be able to measure such a shift compared to the shifts that occur naturally from solar and oceanic variability.
One of the fundamental issues as regards the net cloud effect is the balance between shortwave denied to the system and downward longwave enhanced by energy retained in the system for longer.. AGW theory implies that the latter exceeds the former as regards the energy budget for an overall system warming.
The logical flaw in the AGW position is that shortwave denied to the system is lost completely whereas it needs to get into the system in the first place to provide the energy for downward longwave.
Thus, if solar shortwave never gets into the system it cannot provide the energy that would otherwise have been available to fuel the downward longwave and warm the surface.
If solar shortwave into the oceans declines for whatever reason then the fuel for the downward longwave declines too. The additional delay in transmission of energy to space would need to be large enough to more than offset the energy value of the shortwave denied to the system. On an intuitive basis I cannot see that to be possible and this post gives some idea as to why it cannot be possible. We would need a far denser atmosphere to make any difference and extra CO2 barely affects atmospheric density at all.

Willis, I am not a scientist so forgive me if this is a silly question. I thought that just under 50% of the radiation emitted by the sun was long wave. So why do the instruments not detect more DLR during the day than during the night ? Is the long wave radiation from the sun all absorbed by the atmosphere before it reaches the surface of the earth ? If so, how do we know how much of the DLR is back radiation originating from the earth’s surface and how much comes straight from the sun having stopped for a coffee in the atmosphere on the way down ?

Steve Keohane

Thanks Willis for putting some numbers on this. I like the way you lay it out.

Ken Methven

Willis,
Thank you so much for elucidating so much from a focused, objective and scrupulous treatment of the data. Even I got it!
Well done and keep it up when the motivation takes you.
Ken

Dr T G Watkins

Science at its best. Empirical data explained in a sensible, logical and ‘simple’ way.
Thanks Willis.

Derek Farmer

I’ve found all of your posts on cloud feeback in the tropics both facinating and very informative. The best compliment I can give is that your ideas seem simple and obvious! (with 20-20 hindsight!!!) It does beggar the question as to why ‘professional’ climatologists (being paid large amounts of our money) don’t appear tomake similar levels of progress. These numbers you are coming out with seem very significant.
Needless to say – none are in current GCMs.

Dolphinhead

Willis
I like your work. I am not a scientist but in looking at the question of weather and climate I came to the conclusion that if I were a climate scientist and I wanted to understand the climate I would start by looking at the area where where the big players in the drama strut their stuff, or as you put it ‘…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.’
Without knowing a great deal about the nuances of the climate system it seems obvious that any modulation of the forces that drive the climate that take place within the ‘heat engine’ are liklely to have a proportionally greater impact there than they would elsewhere in the system. In my view understanding what happens in the tropics – how much heat energy enters the system through the front door and how the opening of the door is modulated by low clouds – is the necessary first step to glimpsing the wonders of what must be the finest physical system of checks and balances in the universe.
keep up the good work

gnomish

wow- willils, you did it again – another brilliant piece.
it won’t be long before you’ve got enough data and analysis for a serious publication about the ‘thunderstorm thermostat’.
plz consider it – even if it takes until gore dies to get published.

Peter Pond

Thanks Willis – an easy to understand explanation.
However, your use of clear, readable English, rather than pretentious and obfuscatory polysylabbic terminology, means that “academe” will unfortunately fail to take you seriously.
PS “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 W/m2.” There appears to be a number missing at the end of this sentence (between Figs 6 & 7).
[Thanks, fixed. w.]

cba

Willis,
This is an excellent post. It has some information I’ve not found anywhere that goes right to the heart of the matter. It seems that this is a dagger in the heart for CAWG modellers who believe that clouds must be almost neutral and that combined with THE ASSUMPTION that cloud cover decreases with rising temperature creates the ‘positive’ feedback that permits their claims that there is great sensitivity to CAWG. Most of what I’ve seen out of Lindzen seems tied with the concept of cloud cover reflectivity rather than cloud cover fraction. I noticed too that your resulting reflectivity is around 61% which is definitely in the realm of realistic for clouds while the reflectivity that is associated with the modellers is half that and lower than the average of most types of clouds.
BTW, any conversion of SW incoming to LW incoming by clouds is removing incoming power capable of penetrating beyond the skin of the ocean’s surface. That means it must either heat up the surface skin or it must evaporate more h2o and increase the water vapor cycle activity.
I look forward to seeing more on this track, especially dessler’s backpeddling response.

Septic Matthew

I think that you are on to something, but have you incorporated independently acquired information on cloud cover? It looks like you infer the presence of clouds from the change in radiation, but it would be nice to related the presence of clouds to the changes in radiation.
Your comment about the small size of the CO2 effect compared to the natural radiation is only relevant to the speed at which the steady-state induced change occurs, not whether it occurs.
What you want to show is that transport of heat from the surface of the ocean to the upper atmosphere is supralinear in temperature, that a change from 31C to 32C increases heat transport more than a change from 30C to C1C. With radiation, that’s true because heat radiates proportionally to T^4. For net heat transport above the ocean, that may not be relevant to much.
Overall, I think you have found a gold mine, and I look forward to reading more.

if youi find the time, Willis, perhaps you might look at this post from John Eggerts
http://johneggert.wordpress.com/2010/09/26/the-path-length-approximation/
which might maybe give another clue to your climate thermostat idea.
And also pay attention to what commentator Bart has been posting on climate audit about how established system control theory could inform the Spencers and Dessler’s of our world. My worry is that using these techniques on monthly averaged cludged data does not mean a lot. But it might set something going for you.

JamesD

Bump of dcfl51 question. How does you analysis take into account LR from the sun?

Bernie McCune

Willis
An interesting value that we found when monitoring SW radiation at a couple of solar furnaces over several years in the southern deserts of NM has to do with effects of water vapor. During our monsoon season in late summer atmospheric moisture content is often “high” while in the fall moisture content is low and days are very clear and “crisp”. Our Normal Incident Pyrheliometer (NIP) on clear summer days often read 200 w/m^2 lower (850 w/m^2 at noon) than on dry fall days where readings would often peak at 1050 w/m^2 at noon. There were no clouds during the time of measurement. Water vapor has a significant affect on incoming SW radiation. In the early ’80s El Chicon volcanic gases and ash over a period of months dropped our year round noon NIP readings by up to 100 w/m^2 for about a year. I have always agreed with your ideas about H2O (clouds and vapor) being a very significant moderator of solar radiation be it in the tropics (I spent a year in the Seychelles) or here in the deserts of NM. The data just keeps on confirming it. Thanks for your efforts.
Bernie

Steve in SC

Willis I agree with your contention.
A small personal anecdote if I may, I spent a week after the 4th of July down in St. Croix of the US Virgin Islands. When I left South Carolina it was 99+ deg F with about 80+% RH. At St Croix it was about 85 and 75 decidedly more comfortable. You could tell that the sun was a bit stronger but clouds would pop up and it would rain for 20 minutes 3 times a day. Very comfy.
You must try the rum down there it is most highly excellent!

Willis Eschenbach

Septic Matthew says:
September 15, 2011 at 3:57 pm

I think that you are on to something, but have you incorporated independently acquired information on cloud cover? It looks like you infer the presence of clouds from the change in radiation, but it would be nice to related the presence of clouds to the changes in radiation.

Thanks, Matthew, and the other posters. The buoys do not collect any information about clouds. However, I know (from the maxima and minima) what the clear-sky values are, and from the means (averages) I know what the all-sky values are. The difference has to be the clouds …
w.

Rhoda Ramirez

Willis, I have to agree with most of the commentators above, outstanding work. Your stuff is easy to understand and follow.

Willis Eschenbach

Dolphinhead says:
September 15, 2011 at 3:03 pm

… Without knowing a great deal about the nuances of the climate system it seems obvious that any modulation of the forces that drive the climate that take place within the ‘heat engine’ are liklely to have a proportionally greater impact there than they would elsewhere in the system. In my view understanding what happens in the tropics – how much heat energy enters the system through the front door and how the opening of the door is modulated by low clouds – is the necessary first step to glimpsing the wonders of what must be the finest physical system of checks and balances in the universe.

I’m glad that someone gets the importance of the cloud throttle and the tropics. And indeed, what a magnificent system, it has kept the temperature of the Earth within a half a degree for a hundred years, and within a few degrees for thousands of years. That’s good regulation, particularly for a system governed by something as ephemeral as clouds …
w.

dlb

A very interesting post Willis, you were able to do what I couldn’t, that is finding a bouy measuring DLWR. I’d like to think you are reinventing the wheel, but you never know 🙂 anyway it is the best way to learn to figure it out for ones self. Just something else to consider, NASA’s Terra satellite flies over of a morning when there is less cloud over the land while Aqua flies in the afternoon when there is supposed to be less cloud over the ocean.

I think if you did a similar analysis at the poles where water vapor and clouds are a minimum and days are a year long, you would find that the 50 year rise in atmospheric CO2 hasn’t altered the flow of energy measurably. Finding the data to analyze is the problem.

Willis Eschenbach

man in a barrel says:
September 15, 2011 at 4:01 pm

if youi find the time, Willis, perhaps you might look at this post from John Eggerts
http://johneggert.wordpress.com/2010/09/26/the-path-length-approximation/
which might maybe give another clue to your climate thermostat idea.

That citation argues that the atmosphere is saturated for CO2, because you can’t get “blacker than black”. Which kinda makes sense … until you think about it.
What it ignores is the effect of altitude. The “blackness” of any given layer varies linearly with pressure altitude. Half the pressure, half the molecules to absorb, half the “blackness”. In those upper altitude “gray” regions is where additional CO2 has an effect.

And also pay attention to what commentator Bart has been posting on climate audit about how established system control theory could inform the Spencers and Dessler’s of our world. My worry is that using these techniques on monthly averaged cludged data does not mean a lot. But it might set something going for you.

I’m struggling to keep up and to understand the discussion between Bart and the other gentlemen. I do think he’s on to something, and I wish I knew more about it. Always more to learn …
Part of the problem is the issue of causality. Suppose the day warms, and at some point a thunderstorm forms. That thunderstorm wanders over the ocean, and it leaves the ocean cooler, often cooler than it was when the thunderstorm formed.
What would you say is the cause of that cooling? The thunderstorm? The high temperature that precipitated the thunderstorm?
This is why I’m not real comfortable with the idea of “cloud feedback”. I’m still wrestling with that concept, along with the question of whether clouds are a forcing or a feedback. I’d have to answer “both”, but I’m not sure of that …
Brings to mind the story my mom told, of how the son of a Unitarian minister said “Dad, is there a God?” “Yes, there is”, his father said. “Are you sure?” asked the son. His father replied, “If I was sure of anything, I wouldn’t be a Unitarian …”
So as to thunderstorms being feedback or forcing … count me as a Unitarian.
w.

Willis Eschenbach

JamesD says:
September 15, 2011 at 4:16 pm

Bump of dcfl51 question. How does you analysis take into account LR from the sun?

The answer is, there’s longwave, and there’s longwave. The longwave absorbed by the atmosphere might be though of as “long longwave”. It is radiated by things at a temperature from say 30°C down to -40°C or so.
The longwave from the sun, on the other hand, is “short longwave”, also called the “near infrared” because it is near to the visual spectrum. That infrared is included in the value listed as “shortwave”. I looked in the sensor specs, but found nothing about the bandwidth. However, it says they are using a pyranometer, which is designed to be as flat as possible across the entire solar spectrum.
In any case, by the time you get out to the frequencies of the “long longwave”, there is very little power from the sun in those “long longwave” frequencies. Which is why little of the solar radiation is absorbed by the pure atmosphere.
w.

Allan Tereba

Very nice post as usual and easy to follow. I am a firm believer that any system that has lasted billions of years needs to have strong buffering mechanisms. This is one good example of a strong temperature buffering mechanism. For your analysis you used an equatorial location over the ocean, which is appropriate to examine energy balance and the effect of clouds. It would be interesting to compare these results with a location at considerably higher latitudes, especially in the winter. Short wave radiation would be considerably less due to the angle of the sun and shorter daylight period. Long wave radiation may be somewhat lower due to lower temperatures but relatively more due to the longer night. In general though long wave radiation and cloud cover may have a bigger relative warming (less cooling) effect at night than it does in the tropics due to the lower total radiation. I have not seen cloud formation patterns in these latitudes but expect them to be different than equatorial cloud formation.

Bill Illis

Now if you check the temperature levels (in a Stefan Boltzmann sense), you’ll find they make no sense at all compared to the net radiation levels at any given time.
The temperature increases by a tiny fraction of a single W/m2 during the sunshine day and decreases by a tiny fraction of a single W/m2 during the no sunshine night. (Noting that a Watt equals 1 joule/second and one heck of website host as well).

Excellent post, Willis and very apt in the context of Spencer – Dessler. I’m surprised that the cloud forcing (cooling) is so much – thanks for putting it in plain old watts. It beggars belief that this has not been factored in to the IPCC equations, no wonder Trenberth can’t find the heat.
Sure, it gets more complicated as you go to higher latitudes, and when you factor in time of day and land, but with a 6:1 forcing/feedback ratio in the throttle of the climate engine (tropics), there’s no way you could come away from that analysis with anything other than the assertion that clouds are a negative feedback, and a large one at that.
I liked the way you introduced first, second and third order effects into the mix. I’ve never had it satisfactorily explained to me how it is that a third order effect can have such an influence on a first order effect that it multiplies the original effect by three. Surely if that were the case we would have cracked free energy.

Mac the Knife

Willis,
You are “the gift that keeps on giving”! Excellent analysis, presented in an easily digestible style!
One comment and one question:
Comment: You may have a typo at
“Consider the solar (shortwave) data, a typical day of which is shown in Figure 1.”
Did you mean Figure 2?
Question: In your ‘bonus Figure 8, you applied a 7 watts/meter2 of hypothetical radiation addition from CO2, to illustrate it may be a tertiary and negligible contributor. What source (or sources) were the basis for this hypothetical 7w/m2 CO2 contribution?
Thank You for an excellent contribution! This is really interesting and fundamental work!!!

Bob in Castlemaine

Great post Willis, very clearly explained.
Your day job no doubt allows time for your unstructured creative thought processes.

KingOchaos

Interesting stuff Willi’s.
Just one point in you analysis of back radiation from clouds, from the surface you will only see what is coming back through the atmospheric window directly from the clouds/in wavelengths that the atmosphere is transparent to. But it would also be blocking and re radiating in more opaque wavelengths, but these will be absorbed higher up in the atmosphere above the surface.
So i think it would be a difficult task to infer the insulating effects of clouds purely from surface measurements… cloud altitude, humidity/ the variable path length would effect it.
But interesting stuff, the diurnal variation in clouds/ or trend in them, is certainly an interesting area of inquiry.

Willis,
Nice post! Your averaging problem……yes, it is very much dependent upon the time of day. But, you have a wonderful bell curve right in front of you in which you can use to solve half the problem. I think, but don’t know, that the curve would depend very much on latitude and time of year, but that, too, may be averaged. The question then would be, do some places typically have more clouds during different times of the day and when would it occur? It may be difficult to answer, but, it may not. Meteorologists often inundate us with seemingly obscure data. Perhaps they track that sort of stuff in a manner that can be interpreted. I’d ask Anthony.
To the forcing/feedback…… whatever. It is a feedback that alters forcing and changes the dynamics of our climate, which, causes it to be a forcing. It is simply a matter of believing H2O’s natural state. Was it a cloud first or part of a body of water? I’m not big on labels. But, what if all water started as a solid? Is then the oceans a feedback? What if it was all clouds and then snowed?
As to your response about CO2 and pressure, and just because its fun, does the ideal gas law come in to play there anywhere? 😉
Thanks again,
James

Mark

Willis, in your reply to “Man in a barrel” about the John Eggerts post, you state:
“That citation argues that the atmosphere is saturated for CO2, because you can’t get blacker than black”. Which kinda makes sense … until you think about it.
“What it ignores is the effect of altitude. The “blackness” of any given layer varies linearly with pressure altitude. Half the pressure, half the molecules to absorb, half the “blackness”. In those upper altitude “gray” regions is where additional CO2 has an effect.”
If nearly all of the LW-IR is absorbed within 100 m of the surface, how does it matter what happens at high altitude or the top of the atmosphere? I fail to see how the “re-radiation” argument works. Wouldn’t collisions with other molecules near the ground affect the re-radiation? If the difference is that increased CO2 raises the altitude where the radiation finally “escapes to space”, and therefore the temperature at high altitude increases, how does that heat get back to the surface? If re-radiation is really occurring, how come UV that is absorbed by ozone not get re-radiated and passed through the ozone layer and reach the surface? I would appreciate any direction on how this works.
The rest of your series is wonderfully written. I can’t do the math but it looks like an interesting application of chaos theory. The concept of meta-stable strange attractors for the climate seems to match the historical record of rapid transitions between ice ages and inter-glacial temperatures with fairly stable temperatures between the transitions. Have you considered engaging a chaos theory specialist to assist? I look forward to additional posts!

gnomish

Bill Illis says:
September 15, 2011 at 5:42 pm
“Now if you check the temperature levels (in a Stefan Boltzmann sense), you’ll find they make no sense at all compared to the net radiation levels at any given time.
The temperature increases by a tiny fraction of a single W/m2 during the sunshine day and decreases by a tiny fraction of a single W/m2 during the no sunshine night. (Noting that a Watt equals 1 joule/second and one heck of website host as well).”
that is because temperature and heat are not the same thing – you can not convert degrees to watts.
also, a phase change releases releases or sequesters lots of heat with no temperature change.
Watts, of course, is inimitable. Long may he reign.

Mac the Knife

Willis,
One more question:
Are the data plots in Figures 2 and 3 derived from data recorded by the same buoy on the same day?
Thanks Again!

Willis Eschenbach

Mac the Knife says:
September 15, 2011 at 5:54 pm

Willis,
You are “the gift that keeps on giving”! Excellent analysis, presented in an easily digestible style!
One comment and one question:
Comment: You may have a typo at
“Consider the solar (shortwave) data, a typical day of which is shown in Figure 1.”
Did you mean Figure 2?

Thanks, fixed.

Question: In your ‘bonus Figure 8, you applied a 7 watts/meter2 of hypothetical radiation addition from CO2, to illustrate it may be a tertiary and negligible contributor. What source (or sources) were the basis for this hypothetical 7w/m2 CO2 contribution?

I just picked a number. It happened to be 1% of the dataset average, and it’s larger (almost twice) the 3.7 W/m2 change in TOA forcing from a doubling of CO2, so it made my point well.

Thank You for an excellent contribution! This is really interesting and fundamental work!!!

You’re welcome.
w.

Willis Eschenbach

Bob in Castlemaine says:
September 15, 2011 at 6:00 pm

Great post Willis, very clearly explained.
Your day job no doubt allows time for your unstructured creative thought processes.

Actually, indulging in unstructured creative thought processes when one is running a table saw is not necessarily the best plan …
w.

George E. Smith

“”””” 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. “””””
And by inference those same clouds would also be increasing the LWIR to space, since as you say, half of the cloud absorbed radiation is re-emitted to space, so the cloud which you say is an efficient black body absorber (and emitter) whereas the atmosphere is not.

Willis Eschenbach

Mark says:
September 15, 2011 at 6:53 pm

Willis, in your reply to “Man in a barrel” about the John Eggerts post, you state:

“That citation argues that the atmosphere is saturated for CO2, because you can’t get blacker than black”. Which kinda makes sense … until you think about it.
“What it ignores is the effect of altitude. The “blackness” of any given layer varies linearly with pressure altitude. Half the pressure, half the molecules to absorb, half the “blackness”. In those upper altitude “gray” regions is where additional CO2 has an effect.”

If nearly all of the LW-IR is absorbed within 100 m of the surface, how does it matter what happens at high altitude or the top of the atmosphere? I fail to see how the “re-radiation” argument works. …

Thanks, Mark. The issue is not where the radiation is intercepted on its way to space. It is how many times, on average, it is intercepted. This is because every time the radiation is absorbed, half of it goes back towards the surface. This is true even if 100% of the radiation is intercepted just off the deck.
The “greenhouse effect” works because a shell has two sides. See my discussion here and here. The heating is proportional to how many times (on average) the radiation is absorbed on its way to space.
w.

Willis Eschenbach

Mac the Knife says:
September 15, 2011 at 7:16 pm

One more question:
Are the data plots in Figures 2 and 3 derived from data recorded by the same buoy on the same day?
Thanks Again!

No, I just picked a couple of different days that each illustrated the points I wanted to make.
w.

dp

Willis – what would the effect of sea surface wave action be on the sensors and what would a churning sea vs a glassy sea look like in the data?

Willis Eschenbach

dp says:
September 15, 2011 at 8:18 pm

Willis – what would the effect of sea surface wave action be on the sensors and what would a churning sea vs a glassy sea look like in the data?

Good question, dp. I don’t have a clue … but I figure the scientists who designed, built, and installed the sucker thought about it, and they chose and designed the instrument packages accordingly.
w.

T.A.

Willis,
You said, “I know (from the maxima and minima) what the clear-sky values are, and from the means (averages) I know what the all-sky values are. The difference has to be the clouds …”
Would you kindly explain more specifically how you go from the maxima and minima to determining when there is cloud cover? Are you making assumptions, or is your conclusion based on measurement or observation of actual cloud cover?
I am not disputing your work, just want to be clear on what the evidence is. Thanks.

R. Gates

Interesting as usual Willis. This comment however, may be a bit of an oversimplification:
“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.”
How did you compute this percentage? And even if correct (50% seems way too high), it doesn’t of course mean that 50% is lost to space. LW radiation, striking a greenhouse gas molecule, which of course is not static, but moving and tumbling rapidly, would tend to be re-radiated on average in a spherical pattern, such that 50% would be too high of a percentage to be transmitted directly upward, in fact, a very small percentage would actually be transmitted directly upward, as there would be lots more angles of transmission that are possible short of directly upward . And of course, even any LW radiation going directly upward could then be absorbed and re-transimtted by another greenhouse molecule, etc, such that the LW radiation that does actually go upward from the tops of clouds is not equal to the top of the atmosphere (TOA) LW actually transmitted into space, and is in fact, far less.
The other observation I would have is that the area along the equator, while receiving the most direct insolation, is not of course indicative of the way clouds and radiation interact in other areas further from the equator. As everyone is aware, there are those large regions of descending air on the north or south sides of the Hadley cells where convection is obviously not the rule, but rather a different kind of cloud dynamics exist. See:
http://en.wikipedia.org/wiki/File:Omega-500-july-era40-1979.png
These regions, while not receiving as the same intensity of SW, actually cover a larger area of the earth both north and south of the equator, so some analysis of the balances of SW and LW in relation to clouds would be necessary in those larger areas. Finally of course, while not receiving but a minor portion of the total SW radiation striking earth, the role of clouds in the Arctic environment also needs to be considered, such as found in this study:
http://www.esrl.noaa.gov/search/publications/5724/
But your posts are always enjoyable!

anna v

Willis Eschenbach says:
September 15, 2011 at 8:33 pm
” Willis – what would the effect of sea surface wave action be on the sensors and what would a churning sea vs a glassy sea look like in the data?”
Good question, dp. I don’t have a clue … but I figure the scientists who designed, built, and installed the sucker thought about it, and they chose and designed the instrument packages accordingly.

It would be interesting seeing wavy days versus quiet days. The fractal effect, waves can increase a lot the surface available for absorbing and radiating and evaporating surface.

Septic Matthew

Willis, you wrote: This is why I’m not real comfortable with the idea of “cloud feedback”. I’m still wrestling with that concept, along with the question of whether clouds are a forcing or a feedback. I’d have to answer “both”, but I’m not sure of that …
To me, that is the only sensible evaluation of the evidence right now. My earlier question was sort of just wishing … .

R. Gates says:
September 15, 2011 at 8:58 pm
Interesting as usual Willis. This comment however, may be a bit of an oversimplification:
“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.”
How did you compute this percentage? And even if correct (50% seems way too high), it doesn’t of course mean that 50% is lost to space.
===================================================
Gates, of course, I can’t speak for Willis, but yes, the 50% is too high. Given the multi-directional release, and the spherical nature of the earth, I’m guessing only 40% or so heads back towards the earth. Obviously, it depends upon the height of the molecule. As to the other part about not being lost to space……. I think it is, at least the majority of it is……… Given the multi-directional absorption and consequent emission, and the point that Willis earlier made about pressure and density, there should be less molecules to absorb going upwards, and more to absorb going down. As established earlier, then, more would be emitted upwards than downwards. So, more than 50% gets lost to space.

Willis Eschenbach

T.A. says:
September 15, 2011 at 8:56 pm

<Willis,
You said,

“I know (from the maxima and minima) what the clear-sky values are, and from the means (averages) I know what the all-sky values are. The difference has to be the clouds …”

Would you kindly explain more specifically how you go from the maxima and minima to determining when there is cloud cover? Are you making assumptions, or is your conclusion based on measurement or observation of actual cloud cover?
I am not disputing your work, just want to be clear on what the evidence is. Thanks.

I’ll give it another shot. Let’s consider shortwave. If we take an average of all the shortwave data for each two minute interval, T.A., we are looking at what happens during “all-sky” conditions. This average includes both when the sky is clear, and when it is cloudy. It is shown as the gray line on Figure 4.
The maximum values for each two minute time span, on the other hand, have to be for times when there are no clouds at all. If there were clouds, the total insolation would be less. So that is what happens during “clear sky” conditions. This is the blue line in Figure 4.
The difference between the two is the amount that the clear-sky shortwave radiation is decreased by the addition of the clouds. If for some time around noon when there are no clouds the shortwave is 1400 W/m2, and on an average day at the same time the shortwave is 900 W/m2, then it is clear that the effect of the addition of clouds is a reflection of half a kilowatt per square metre back to space.
If you still have questions, ask’em …
w.

Richard111

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, and on an average day at the same time the shortwave is 900 W/m2, then it is clear that the effect of the addition of clouds is a reflection of half a kilowatt per square metre back to space.”
Thanks for for this. It makes the data on this site easier to understand.
http://www.milfordweather.org.uk/solar.php
Since it NEVER reaches 1400 W/m2 I assume is because the location is at 51N. Sun simply too low in the midday sky. We’ve been getting a lot of cloud this year it seems.

AusieDan

Willis – congratulations on this and your earlier posts in ths series.
I have a question which I fear discloses my ignorance, but here goes:
If the average 24 hour temperature does not vary very much, I would expect that the difference between SW and LW radiation would be a sine wave, more or less, over 24 hours, centered on zero.
Can you comment or straighten me out when you have a chance?
Regards.

AusieDan

Willis,
Having now re-read your two earlier posts and thought more about the charts in this one,
I’m feeling quite foolish.
I see now that the incoming heat is greater than the outgoing and that the balance is transferred via wind and ocean to higher latitudes.
Now two (probably even more stupid) questions arise:
1. Why is just enough heat moved up latitude (north and south) to keep equitorial temperate constant?
2. Why do the poles hold some net heat and not pass them into space, during years when the global temperature is rising (the reverse during ice ages)?
You are saying in effect that the equator acts as a very good airconditioner but that the poles can’t control their temperatures very well.
Have I grasped it and if so, why is it thus?
What drives the climate?
(Easy question).

Stephen Wilde

In order to deal with the ‘problem’ that global cloudiness decreased during the warming spell/period of more active sun it is necessary to recognise three things:
i) That a reduction in cloudiness during a period of more active sun introduces a positive system feedback by allowing more solar shortwave into the oceans.
ii) Something else has to happen to negate that positive feedback from cloud reduction.
ii) We have observed a consequent poleward shift of the climate zones with more poleward/zonal jets. That is what alters the rate of energy transfer from surface to space and that is the negative feedback. Its power comes from the water cycle and the energy transfer capabilities of the phase changes of water.
Shifting the air circulation systems latitudinally has two contradictory effects:
i) Altering energy flow into the oceans by moving the cloud bands latitudinally
ii) Altering the speed with which energy is transferred from surface to space by moving the climate zones latitudinally.
The first is a positive feedback and the second is a negative feedback and the second always limits the first with the climate price to be paid for the necessary adjustment being a change in the relative sizes and positions of all the permanent climate zones. The sign of i) and ii) can each be reversed, thus:
i) A reduction in cloudiness for a warming effect will be countered by a poleward shift increasing energy flow to space
ii) An increase in cloudiness for a cooling effect will be countered by an equatorward shift decreasing energy flow to space.
Note that it is NOT a zero sum process because the natural flow of energy from warm Earth to cold space is dominant so whereas scenario i) will limit warming of the system very effectively scenario ii) will only restrain cooling for a short while because if energy doesn’t get into the system in the first place slowing down the energy flow to space is only a short term solution.
That is all that climate change amounts to. Anything that tries to warm or cool the system is countered by a change in the rate of energy transfer to space which alters the relative sizes and positions of the permanent climate zones. All observed climate changes fit that description.
The underlying equilibrium is set by atmospheric pressure which in turn sets the energy cost of evaporation by fixing the amount of energy required to achieve the phase change of water from liquid to vapour.
Much more detail here:
http://www.irishweatheronline.com/news/environment/climate-news/wilde-weather/setting-and-maintaining-of-earth%E2%80%99s-equilibrium-temperature/18931.html
as regards the setting of the basic equilibrium temperature and here:
http://www.irishweatheronline.com/news/environment/climate-news/wilde-weather/feature-how-the-sun-could-control-earths-temperature/290.html
as to how the solar changes seek to alter the equilibrium temperature (but largerly fail as per the so called ‘faint sun’ paradox).

Willis Eschenbach

AusieDan says:
September 16, 2011 at 12:04 am

Willis – congratulations on this and your earlier posts in ths series.
I have a question which I fear discloses my ignorance, but here goes:
If the average 24 hour temperature does not vary very much, I would expect that the difference between SW and LW radiation would be a sine wave, more or less, over 24 hours, centered on zero.
Can you comment or straighten me out when you have a chance?
Regards.

You’d think it would be a sine wave but nature is rarely that simple. The day goes through various circulation regimes that mean it ends up far from a sine wave, just as the temperature is far from a sine wave. See my post “It’s Not About Feedback” for some discussion of this.
w.