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.
dcfl51 says:
September 15, 2011 at 2:38 pm
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 ?
JamesD says:
September 15, 2011 at 4:16 pm
Bump of dcfl51 question. How does you analysis take into account LR from the sun?
Willis Eschenbach says:
September 15, 2011 at 5:33 pm
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.
#####################
Shrug. AGWScience Fiction Inc has written out of the picture (see Kiehl/Trenberth ’97 cartoon) longwave infrared, aka thermal infrared aka heat, direct from the Sun to the Earth, which is what heats the land and oceans and us.
It has been replaced by the fictional science meme that shortwave radiation from the Sun, aka solar, sunlight, which is visible and the two shortwaves either side of uv and near infrared, are what actually heat the land and oceans of Earth. Of course, those not modern day scientists might recall that these are reflective energies, not thermal, they are not hot, and they do not heat molecules. They don’t have the power to move molecules of water into rotational resonance which is what heats up water, thermal infrared does have that power, and so does heat up water.
Blue light for example is in the set of reflective energies, it is absorbed briefly by the electrons of nitrogen and oxygen in our atmosphere, note electrons, and sent out the way it came, this is called reflection/scattering in the electonic transition category of effects. It is not moving the molecules, note whole molecules, of nitrogen and oxygen into rotational resonance which is what would actually heat them. Ditto, blue light does not heat the molecules of water in the ocean, not by the same process, but because blue light doesn’t even get in to dance with the electrons of water, it isn’t let in, a slight delay as it tries, and then it’s passed on, this is called transmission.
That’s the basic mechanism from real world traditional science. AGWScience Fiction Inc has given the properties of the real heat we feel from the Sun, thermal infrared, to the light we see from the Sun.
I suggest that none believing this AGWSF meme look at the blue sky, they’ll bake their eyeballs.
Willis, I too enjoy your writing, you are exceptionally clear in telling a story and enjoyable in that and in the things you find. It’s such a great pity that your basic premise is based on the junk science fictional meme now widespread through mis-education. If you could get that sorted, you’d be truly brilliant.
There are other stories around, for example:
What do you make of that?
Or this from the beginnings of the search for knowledge about Heat energy from the Sun?: http://docs.lib.noaa.gov/rescue/mwr/056/mwr-056-08-0322.pdf
From which: ”
Emden found that the stratosphere sends no radiation clownwards,
and of, course the same result came out of my
previous work. The new investigation shows that the
stratosphere sends on the average a downward flux of
longwave radiation of more than. 120 cal./cm.2/min., which
is more than 43 per cent of the effective solar radiation.
This agrees with the observations made by Angstrom on
mountain peaks and in balloons, which revealed a downward
radiation of between .13 and .16 cal./cm.2/min.
at heights between 4,000 and 5,000 metres, where, according
to Emden,’ there should have been less than .05
cal./cm.2/ min.
There’s some recent work here in this paper, for which I can’t get access, they don’t allow pay per view: http://www.agu.org/pubs/crossref/2011/2010JD015343.shtml Perhaps someone here can enlighten us as to contents.
NASA used to teach traditional well tried and tested and understood physics about this: From this NASA page:
“Near infrared” light is closest in wavelength to visible light and “far infrared” is closer to the microwave region of the electromagnetic spectrum. The longer, far infrared wavelengths are about the size of a pin head and the shorter, near infrared ones are the size of cells, or are microscopic.
Far infrared waves are thermal. In other words, we experience this type of infrared radiation every day in the form of heat! The heat that we feel from sunlight, a fire, a radiator or a warm sidewalk is infrared.
Shorter, near infrared waves are not hot at all – in fact you cannot even feel them. These shorter wavelengths are the ones used by your TV’s remote control.
Infrared light is even used to heat food sometimes – special lamps that emit thermal infrared waves are often used in fast food restaurants!
Now NASA teaches that thermal infrared doesn’t even get to us here on Earth’s surface..
What do you make of that?
How does a non-thermal energy, near infrared, manage to send whole molecules into rotational resonance?
So yes, there’s longwave and longwave, and these are heat on the move from the extremely hot Sun to us on Earth eight minutes later.
The heat we feel every day from the Sun, a fire, is thermal infrared.
So, dcfl51’s question is best answered, imho, by saying, ‘we who promote the AGWScience Fiction Inc’s meme which has reversed the properties of Heat and Light from the Sun, have no idea how to answer you, we actually don’t even understand the question.’
I on the other hand would answer, ‘You’ll have to look elsewhere for a real physics answer to you question because, as interesting as Willis is, he bases his work on a fictional through the looking glass AGWSF premise; on a different world where impossible things happen, where Light energies from the Sun heat matter and direct Heat from the Sun plays no part in heating its imaginary organic matter.’
At the very least, note there is a disjunct; both stories can’t be real physics because they each give contrary explanations of properties and processes. I would have thought this would be of interest to scientists in this subject..
Sorry, missed out the URL link to the NASA page I quote: http://science.hq.nasa.gov/kids/imagers/ems/infrared.html
While I’m here, let me fetch what I’ve found on the manipulation of mass education on this point: http://wattsupwiththat.com/2011/07/28/spencer-and-braswell-on-slashdot/#comment-711886
T the T at 10.42pm “Clouds DO cool less and warm the ocean as a result though”
Not sure on your logic? Clouds are not just some sort of valve that slows the release of heat from the ocean, they are warm entities and will direct radiation back to the surface thus reducing any net loss of energy from the ocean. If the ocean is warm it will emit radiation at a known rate for this temperature, regardless of whether there is cloud or a dry CO2 free atmosphere above it.
Just one thought for those who are insistent that downwelling LW radiation can’t enter the oceans– if you accept the notion that SW radiation stays more or less constant at the ocean surface when averaged over longer periods then how would you explain the increases in global ocean heat content when looked at over a longer period?
And some of you might benefit from looking over this excellent chart that shows the spectrum of sunlight at the top of the atmosphere compared to what is at sea level:
http://en.wikipedia.org/wiki/File:Solar_Spectrum.png
And finally, this chart:
http://en.wikipedia.org/wiki/File:Atmospheric_Transmission.png
Which shows that Willis’ estimate of 50% of the LW going up into space is way too high as the actual amount is somewhere around 15 to 30%.
coturnix says:
September 17, 2011 at 1:22 am
“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. ”
You may want to rephrase that. Although the “sun shines the same all the time”, the amount of energy arriving at the surface is dependent on lattitude and time of year. Hence, Gulf of Mexico waters are colder in winter than in summer.
Joe Born says:
September 16, 2011 at 10:46 am
”
Mark:
“If the difference is that increased CO2 raises the altitude where the radiation finall
My no doubt inaccurate paraphrase is that CO2 enrichment raises the altitude at which, seen from space, a given optical depth is reached. Given the lapse rate, that means that the earth’s effective radiation temperature for a given surface temperature decreases: there is less radiation into space.
”
There’s two factors going on that will affect the lapse rate. First off, the lapse rate is merely related to the energy flow and conservation of energy. A ‘chunk’ of atmosphere will be at a temperature where the energy coming in equals the energy going out. A change in ghg concentration will cause a bit of shifting around of temperature in order to balance again. A change upward in ghg concentration will also increase the radiative ability of the chunk of atmosphere so that it can radiate more energy at a given temperature which means the temperature change doesn’t have to be as much as a very simplistic calculation might suggest.
Perhaps Willis should embrace a little more of the averages approach to hone his current (excellent) idea to a finer point and sharper cutting edge.
Earth’s avg. T is about 288K which means that 390 w/m^2 escapes the surface. The incoming solar is about 342w/m^2 average with about 30% of that amount reflected back into space, which leaves about 239 W/m^2 to be absorbed by Earth and atmosphere. For balance, the Earth must radiate back into space about 239W/m^2 on average. Something like modtran calculator will show that about 259w/m^2 escapes to at least 70km above with clear skies and there’s not much up there. Note that we’re 20W/m^2 too much radiation over our needed average. Also note that with 390 w/m^2 leaving the surface and 239 w/m^2 being our necessary average, that there is 151 W/m^2 that must be blocked on average and ghgs only block about 130 w/m^2. Clouds, etc. are responsible for the rest. Since cloud cover is close to 50/50 (or 62/38 and variable) cloud tops can only radiate around 220 w/m^2 into space for our 239w/m^2 balance. At the ground level, there must be an average of over 151 w/m^2 LW radiation reaching the ground along with what reaches the ground from the solar.
Note that solar may be almost half IR, but it is shortwave, mostly close to visible light, not LW such as the peak of emissions for Earth temperature objects.
The nice thing about Willis’ thread here is that one can now use all those weapons from the enemy camp against them.
Willis writes… “The ocean gets about 170W/m2 from solar, and it’s losing about 390 W/m2 … if DLR isn’t being absorbed by the ocean, then why isn’t it frozen?”
…but doesn’t accept that the energy from the DLR forms part of the stefan-boltzmann energy requirement for the ocean to radiate. The upshot of this is that the DLR doesn’t warm the ocean. At leaast not in the way Willis and many others believe can happen.
OK Willis, from what we know about the skin, where does the DLR energy go? And how does it do it? You need to be quite precise because waving your hands around and saying “it goes into the ocean” simply wont cut it as an answer.
R. Gates says:
September 17, 2011 at 5:35 am
R. Gates, please learn to read. I said at any given radiation event, the radiation is emitted spherically, with just under half headed back TOWARDS the earth, and the rest headed TOWARDS space … sheesh, I get into enough trouble with what I do say, no need for you to falsify things I’m supposed to have said …
w.
Your figure 6. reminded me of an observation I made long ago on the hundreds of mornings watched sunrise from a ship in the tropics. It became sport to try to catch the morning green flash. Problem was, as sunrise approached the clouds (broken cumulus) formed to the East, essentially leading the sun. They would continue to build until the sun was almost at zenith then dissipate until the setting sun caused them to reform due to cooling. This is purely anecdotal but I’d expect the weather observations reported by ships working the TAO array would confirm with their cloud reports. I wouldn’t be surprised if those ships haven’t carried a cloud cover sensor for some period either.
TimTheToolMan says:
September 17, 2011 at 8:47 am
First answer my question and we can avoid talking past each other. Does the DLR get absorbed by the ocean, and if not, what is warming the ocean? Once we can see what we agree on, we can move forwards.
w.
Willis,
Both my own calculations and wikipedia disagree with these numbers. Wikipedia & I get 1412 and 1320 for the two values. Earth moves about 1.67% closer Jan and 1.67% farther in July. This makes the sun about 2 * 1.67% = 3.35% brighter and dimmer than average thru the year, which gives the numbers above.
These familiar images show that water vapor does indeed absorb noticeable parts of the incoming solar spectrum.
http://www.howtopowertheworld.com/image-files/solar-spectrum.png
http://www.sunwindsolar.com/a_images/co2_water_vapour.gif
The one mechanism I can imagine that might boost the surface irradiance is reflection from clouds. If the sun is shining on the surface, but nearby white clouds are also reflecting some light, that might boost the numbers a bit.
Willis Eschenbach says:
September 17, 2011 at 2:48 am
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.
What I was pointing out was that our instrumentation can’t differentiate between upwelling longwave emitted from the contiguous ocean surface, and downwelling longwave absorbed and re-emitted up and down by the highly humid air just above the ocean surface. This is a fact you didn’t try to refute.
But even if we ignore the reality of the high humidity just above the ocean surface to simplify the argument, there is the issue of what happens to the downwelling longwave after it has been absorbed in the first few um of the ocean surface, which as Tim the Toolman correctly states, is cooler than the rest of the ‘skin layer’ below it. It can’t conduct downwards without defying the second law of thermodynamics, and if the ocean is disturbed by wind the additional downward mixing is more than offset by the extra evaporation wind causes.
You’re ocean freezing argument fails because we’re not saying the downwelling longwave radiation isn’t absorbed. What we are saying is that it is re-emitted without affecting the bulk temperature of the ocean in any significant way.
Great post Willis.
dcfl51: One doesn’t have to be a scientist to Google or look it up on wikipedia. http://en.wikipedia.org/wiki/Sunlight It only makes sense that we can see in the spectrum available from the sun. Most of the Sun’s energy is in the visible range, especially when including the near-IR. I find this graphic informative: http://en.wikipedia.org/wiki/File:Solar_Spectrum.png
You’re ocean freezing argument fails because
it ain’t frozen.
period,
it’s surely not up to anybody to explain why the ocean is not frozen because it isn’t.
but perhaps you can make a model and tweak up some data and maybe you can convince yourself it should be?
i think you are buying into travesties.
gnomish says: September 17, 2011 at 12:32 pm
The point is that Willis believes (as do I) that several models that people are presenting would indeed lead to massive and continued heat loss from the ocean. Therefore their models must be incorrect (or our understanding of their models must be incorrect) since the ocean is indeed observed not be continuously cooling.
Willis Eschenbach says:
September 16, 2011 at 10:40 pm
Without a doubt, on a “micro” level, climate mechanisms are devastatingly complex. So is quantum mechanics. Yet, on a macro level, atomic and molecular systems regress to a mean behavior described by Ehrenfest’s theorem.
Many (really all, depending on how far down you go) systems are like this – very complicated in the details, yet manifesting a simple order when you pull back from the trees to view the forest. I gave the example of a pulse modulator as a very nonlinear element whose overall actions in a feedback loop can nevertheless be described using linear systems theory.
So, I think my answer to you is, yes, things may be very complicated. They may not be amenable to such simple modeling. But, then again… they may.
Tallbloke says:
The top layer doesn’t NEED to conduct any energy downward for the depper layers to warm up.
Solar radiation already penetrates thru the surface and into the bulk of the ocean (up to ~ 100 m) quite well. To prevent massive warming of the bulk of the ocean, the surface layer needs to conduct energy upwards, which it does because of the aforementioned temperature gradient.
My point that I was arguing in the previous thread is that if you reduce that temperature gradient of the skin layer by adding energy to the top of that layer — perhaps by adding more downward IR — then the conduction upward will be decreased. The energy from the sun will then not be able to escape from the bulk of the ocean, and the bulk of the ocean will warm.
To repeat – no conduction downward of energy from IR hitting the surface is needed to warm the bulk! It is sufficient for the downward IR to throttle the escape of energy.
Willis askes “Does the DLR get absorbed by the ocean”
We’ve already covered this. The DLR is absorbed into the top 10um of the ocean. This much we agree on. The ocean “warms” as a result. We also agree on that. They’re the major points in terms of a macro *effect* but the problem comes when taking a macro *view* of it. Specifically you’ve written…
“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.”
Because no. The surface doesn’t end up warmer. If there were suddenly no GHG’s then instantaneously the surface would be exactly the same temperature despite an instantaneous “drop” of all that energy you believe “warms” it. The reason the surface temperature will drop is because the energy being lost from the ocean is now greater (the DLR used to account for some of this) and it will cool more quickly with an eventual corresponding drop in the SST.
This as far as I can see is the fundamental difference in our understandings on the ocean and how its effected by GHGs.
Willis, I have read all of the posts and I think that what you wrote above is indeed a good next step: I’ll likely look next at splitting the dataset in two, warm dawns versus cool dawns, as I did before.
cba says: s
“”””
Mark:
“If the difference is that increased CO2 raises the altitude where the radiation finall
My no doubt inaccurate paraphrase is that CO2 enrichment raises the altitude at which, seen from space, a given optical depth is reached. Given the lapse rate, that means that the earth’s effective radiation temperature for a given surface temperature decreases: there is less radiation into space.
”
There’s two factors going on that will affect the lapse rate. First off, the lapse rate is merely related to the energy flow and conservation of energy. A ‘chunk’ of atmosphere will be at a temperature where the energy coming in equals the energy going out. A change in ghg concentration will cause a bit of shifting around of temperature in order to balance again. A change upward in ghg concentration will also increase the radiative ability of the chunk of atmosphere so that it can radiate more energy at a given temperature which means the temperature change doesn’t have to be as much as a very simplistic calculation might suggest.
“”””
Nice comment.
This is how it goes : In the normal troposphere, the lapse rate is close to constant (temperature decreasing linearly with altitude). This is because thermal exchanges are mainly by molecular motion and a simple thermodynamic transfer process(adiabatic transfer) yields this result. This means that the radiation exchanges are negligible and the difference of temperature between a given altitude and ground is fixed independently of ghg concentration, i.e no corrections of the type you suggest. However with increasing altitude the transition from troposphere to stratosphere is in fact the transition from temperature being controlled by molecular motion to controlled by radiation. In the stratosphere the corrections should be made.
This is why the IPCC AR4 defines ghg forcing as the change of IR radiation emitted for a given change of ghg concentration, AFTER the stratosphere has been allowed to reequilibrate.
Note : If the effective altitude of emission (altitude at which the radiation will escape to space without being reabsorbed) is indeed in the stratosphere (for a given IR wavelength), then the lapse rate is of the opposite sign and will lead to a negative change of the greenhouse effect. Corrections are only needed for this negative abnormal response.
Two remarks :
1:This business sems to me a major cause of uncertainty in evaluating the CO2 forcings: namely how do you treat the intermediate altitudes of the tropopause?
2: You can get a derivation of the logarithmic law for the troposphere forcing from a simple heuristic argument based on the lapse rate. I can post it if anyone is interested.
Tim Folkerts says:
September 17, 2011 at 1:13 pm
so true!
the facts are right, therefore the models are incorrect.
maybe radiation physics doesn’t cover phase change work at all…
maybe the models don’t have a bazillion tons of vapor condensing at sea level every time the sun sets and releasing jiggawatts of latent heat.
maybe the satellite infrared sensors can’t see thru that and aren’t really reading the ocean at all.
maybe there’s lots of unknown vulcanism.
but the models are wrong.
“daniel kaplan says:
September 17, 2011 at 5:42 pm
cba says: …
”
Daniel,
There is NO altitude which allows radiation to escape. This is a function of wavelength and on strong line centers, it never happens. Elsewhere in the spectrum, emissions from the surface go straight through. As one goes up in the atmosphere, line widths narrow, increasing the liklihood of capture, but over narrower and narrower bandwidths – hence allowing more energy through. WHen dealing with smaller areas and lower temperature differences, the liklihood of absorption for strong lines tends to approach the liklihood of emission and so there is very little net radiative transfer between these areas. Given two areas of the same temperature, there is no net thermal transfer of any kind. This doesn’t and can’t happen in the atmosphere because of the geometry of the system and we can use the plane radiative transfer approximation for this.
The lapse rate is strictly a conservation of energy situation. Conduction, convection, and radiation heat transfer in and out define what the lapse rate can be. When one hits the tropopause, that’s where convection is dwindling to a very low contribution. Conduction is not a great factor because air is a superb insulator. Without convection, all you have going is radiation.
BTW, I tend to use a line-by-line one dimenisional atmospheric model rather than a heuristic approximation. However, the true problem is that even a 1-d model of radiative transfer works well for clear skies but clouds change everything dramatically.