Guest Post by Willis Eschenbach
There is a more global restatement of Murphy’s Law which says “Nature always sides with the hidden flaw”. Parasitic losses are an example of that law at work.
In any heat engine, either natural or manmade, there are what are called “parasitic losses”. These are losses that tend to reduce the temperature differentials in the heat engine, and thus reduce the overall efficiency of the engine. In general, as a percentage parasitic losses increase rapidly with ∆T, the temperature differences in the engine. In the climate system, two main parasitic losses are the losses from the surface to the atmosphere by way of conduction and convection (sensible heat), and the losses from surface to atmosphere by way of evaporation and transpiration (latent heat). Both of these parasitic losses act to reduce the surface temperature with respect to the overlying atmosphere, by simultaneously cooling the surface and warming the atmosphere … nature siding with the hidden flaw to reduce the overall system efficiency. So I decided to see what the CERES data says about parasitic losses. Figure 1 shows the parasitic losses (the sum of sensible and latent heat losses), as a percentage of the total surface input (downwelling longwave plus shortwave).
Figure 1. Parasitic losses (latent and sensible heat loss) from the surface to the atmosphere. Percentage of parasitic loss is calculated as the sum of sensible and latent loss, divided by the total surface input (downwelling shortwave plus downwelling longwave).
I was most interested in how much the parasitic loss changes when the total surface input increases. Figures 2 to 4 shows that situation:
Figures 2-4. Scatterplots, parasitic loss in watts per square metre (W/m2) versus total surface input (W/m2). Parasitic loss is loss as sensible and latent heat. Gold line shows the loess smooth of the data. Red dots show land gridcells, which are one degree square (1°x1°) in size. Blue dots show ocean gridcells.
I was very encouraged by finding this result. I’ve written before about how at the warm end of the spectrum, parasitic losses would increase to the point where most of each new additional watt striking the surface would be lost as sensible and latent heat, and that little of it would remain to warm the surface. These graphs bear that out entirely. Here’s why.
The slope of the gold line above is the rate of increase in parasitic loss for each additional degree of warming. As you can see, the slope of the line increases from left to right, although the rate of increase goes up and down.
In order to understand the changes, I took the slope (change in parasitic loss divided by the corresponding change in surface input) at each point along the length of the gold line for both the land and the ocean separately. Figure 5 shows that result.
Figure 5. Change in parasitic loss (in W/m2) for each additional W/m2 of surface input. “Wobbles”, the looped parts in the two graphed lines reflect subtle changes in the loess smooth, and can be ignored.
Now, what are we looking at here? Well, this is how the parasitic loss changes as more and more energy is input to the surface. Where there is little surface input, the loss is low. In fact, at the South Pole the situation is reversed, and the net flow of energy is from the atmosphere to the surface. This is the result of huge amounts of energy being imported from the tropics.
The key point, however, is that as we add more and more energy to a given gridcell the amount of parasitic losses rises, in perfect accordance with nature siding with the hidden flaw. And at the right hand end of the scale, the warmest end, for every additional watt that is added, you lose a watt …
Is this relationship shown in Figure 5 entirely accurate? Of course not, the vagaries of the smoothing process guarantee that it isn’t a precise measure.
But it clearly establishes what I’ve been saying for a while, which is that parasitic loss is a function of temperature, and that at the top end of the scale, the marginal losses are quite large, close to 100%.
Now, as you can see, nowhere is the parasitic loss more than about 30% … but the important finding is that the marginal loss, the loss due to each additional watt of energy gain, is around 100% at the warm end of the planet. Here is the parasitic loss for the planet as a whole versus total surface input as shown in Figure 2:
Figure 6. Change in parasitic loss (in W/m2) for each additional W/m2 of surface input, as in Figure 5, but for the planet as a whole.Change in parasitic loss (in W/m2) for each additional W/m2 of surface input. “Wobbles”, the looped parts in the two graphed lines reflect subtle changes in the loess smooth, and can be ignored.
Note also that across the main part of the range, which is to say in most of the planet except the tropics and poles, about half of each additional watt of energy increase doesn’t warm the surface … it simply goes into parasitic loss that cools the surface and warms the atmosphere.
Best to all,
w.
PS—If you disagree with what I’ve said please quote my words. That lets all of us know just exactly what you disagree with …
All Balls and no Chain – in short (eh Willi Boy). Mental Masturbationism most unbeComing.
And Trendie`s (well he is isn`t he) peer reviewed by like-inclined individuals “Trick of the Light Fantastic” illustration is the same sort of stuff !
I think the point that is being missed is that the so called effective emission height (EEH) varies with density.
It isn’t a height above a surface that we should be looking for because the radiative fluxes within an atmosphere work in three dimensions, not two.
The greater the density of a radiatively active atmosphere (or any atmosphere, since no gases are completely inert radiatively) the closer to the surface will be the EEH.
So, how to envisage an EEH that varies with density ?
The adiabatic lapse rate slope.
As long as a molecule is at the correct height for its temperature along the adiabatic lapse rate slope then it will have DWIR and UWIR in balance and that is the EEH for that particular molecule.
Any GHG finding itself out of position, whether too high or too low, will be moved by convection back towards the correct height for its temperature.
Too cold for its height will result in it falling back towards the right position and it will warm adiabatically as it falls.
Too warm for its height will result in it rising up towards the right position and it will cool adiabatically as it rises.
The mechanism will be the temperature induced density variations that cause convection.
That is the global thermostat.
At any given moment there are the same number of molecules too warm as too cold so their net thermal effect is zero and convection always works to negate any imbalances that may arise.
Kristian said:
“It (DWIR) is treated by Robert Brown just as an independent HEAT flux which is able to go and work as just that, heat, anywhere, even towards hotter.
In reality it doesn’t heat anything. Instead it causes the GHG molecules to do additional work against gravity which cancels the HEAT by converting it to gravitational potential energy (NOT HEAT) at a greater height.
Having been pushed upwards by the temperature induced density change via convection the initially warmed GHG molecule finds itself above the adiabatic lapse rate slope and so cooler than it ‘should’ be but it continues radiating out to space which makes it even colder than it should be relative to its height and so it starts to sink again until it is below the adiabatic lapse rate slope when it picks up more IR from the ground, becomes too warm and rises above the adiabatic lapse rate slope again.
So, in rising and falling above and below the lapse rate slope a GHG first absorbs IR from the ground, carries it upward, offloads to space and falls back again for another load and the cycle continues.
GHG’s may absorb IR from the ground but they then act as a form of pumping mechanism which ensures that their thermal effect at the surface is zero.
Their absorption capability primes the pump. Density differentials then work adiabatically against gravity. Their radiating capability then discharges the energy used for priming the process to space. The molecule falls and is again primed and so it goes.
James Rollins Jr says:
March 31, 2014 at 12:34 am
How many errors can you pack into a single post?
“That’s not “back radiation” that’s infrared radiation primarily, from direct solar downwelling.”
“Downwelling” radiation, by definition, does not include incoming from the sun. How can we tell the difference? Because the spectra are totally different – there is virtually no overlap. Solar insolation includes a lot of shortwave infrared, but virtually no longwave (past, say 3um). Downwelling from the atmosphere is in the longwave infrared, with virtually no shortwave infrared. Measurements of this “downwelling” flux specifically block out the shorter wavelengths to isolate the longwave.
What Willis and others are talking about, and what was measured in the link you gave, was the longwave infrared, specifically toexclude the solar input.
The 400 W/m^2 Willis has been talking about is the typical upwelling flux density from the earth’s surface. The 324 W/m^2 typical downwelling longwave yields a difference of 76 (these are only very rough averages, of course), which is the NET radiative HEAT transfer between the surface and the atmosphere. Of course, if the atmosphere were transparent to longwave infrared, there would be no downwelling longwave flux, and the earth’s energy balance would be entirely different.
The link you provide shows the downwelling longwave infrared flux density varying between a daytime peak of about 350 W/m^2 – right where cited – and a nighttime low just below 300. I’d say an average of 324 W/m^2 is perfectly plausible given this data, wouldn’t you?
So rgbatduke above proposes a perfect Black Body with a fixed window that is transparent to Solar Spectrum plus IR & LW EMR and which contains a reservoir of material that can reach a temperature at which it achieves radiative equilibrium with a Star by use of that fixed perfect window ALONE – AND – then go on to achieve an even higher temperature of equilibrium by the addition of a veil that is opaque only to the wavelength of its initially outward LWR.
No, I don’t propose this. Read the text. This is a simplified version of a more detailed single layer model that has parameters for easily measurable differential absorption. Which is itself an approximation of the actual spectroscopy of the atmosphere, which (of you are interested in doing something other than picking nits) you can look at measured graphs of in Grant Petty’s book or many other places, which show that the atmosphere is, in fact, significantly transparent in the bulk of the approximately blackbody spectrum associated with the 6000K sun, and is, in fact, significantly opaque in the absorptive bands of CO_2 water vapor, and less opaque but still strongly absorptive in ozone, with little visible signature from other GHGs. Petty has spectrographs of that, as well, as measured both at the bottom of the atmosphere looking up and the top of the atmosphere looking down. But data, I’m sure, doesn’t matter to you.
In the end, though, yes, if there is differential absorption of the atmosphere between SW and LW radiation, there is a significant GHE. This model is without a doubt an oversimplified one, but it suffices to disprove the most often complaints of people that don’t understand thermodynamics — that the effect described in no way violates the first or second laws of thermodynamics, and results in a warmer surface with GHGs than without them. To determine accurately how much warmer is nontrivial, and cannot be done with a single layer model and ignoring other aspects of heat transport.
rgb
Duke said……………………
I`m nit picking,
I say,
I`m spoiled for choice.
it doesn`t matter how many times I might pour back on forth part of the contents of a pint glass into a smaller one it still ends up being just a pint (if I`m lucky)!!
[No, the final liquid will end up being entirely contained in the volume of the smaller jar. Or on the floor. Mod]
I want to take this time to encourage you, the individual reader, to go back and examine the claims made by Curt.
Curt and Willis are both saying things that even on cursory inspection,
are wildly inaccurate; Willis with his “80% of natural emissions from earth’s surface are radiant”
Literally so easily checked it makes one wonder what is going through his head – how could he believe a planet known to lose nearly fifty percent of it’s energy through evaporation alone,
is actually losing so much energy purely to radiation that all other losses, combined, are minor?
Reminded of the glaring conflict with reality, of this unforgivable thermodynamic error, Curt pipes up with his declaration of support for it,
and along the way has of course made a list of his own, hilarious claims.
We’ve watched Curt declare he’s very well educated, and able to understand the issues..
Curt is now saying he thought Sunlight and Earth emitted infrared light are so completely different in spectra
that the term “Downwelling Radiation” can’t mean from the sun because the sun doesn’t produce any medium or long wave radiation infrared radiation.
Look at his assertions; then look at this illustrated graph of solar spectrum.
“the Sun emits nearly zero energy to earth, in earth’s own frequency.
“The sun emits nearly no long wave infrared” Curt hilariously shouts as proof he’s right.
“The very type infrared being sampled for rules out any sunlight being in that at all!”
Look at the top of the atmosphere and the sunlight arriving.
Look at the bottom of the atmosphere and the sunlight arriving.
Compare this to Curt’s claim: “The sun emits almost no energy in the same frequency of earth.
Curt doesn’t even know generally what spectra the sun emits.
The things Curt is saying aren’t remotely possible because of
grammatical error, or inability to explain himself.
He told us all: stating it as a proof he’s thought about this, a long,
long time: The sun emits nearly zero earth spectra infrared.
Curt says:
April 1, 2014 at 7:59 am
“Downwelling” radiation, by definition, does not include incoming from the sun.
Because the spectra are totally different – there is virtually no overlap.
Solar insolation includes a lot of shortwave infrared, but virtually no longwave (past, say 3um). Downwelling from the atmosphere is in the longwave infrared, with virtually no shortwave infrared. Measurements of this “downwelling” flux specifically block out the shorter wavelengths to isolate the longwave.
I think everyone needs another opportunity to read what Curt wrote, as his proof, he thinks he understands what he’s saying so here it is.
Note that he’s referring to “the link you provided” meaning me.
That is the link Willis provided, as proof 400 w/sq/meter is upwelling from the earth. When what it actually is, is a link to an experiment showing 353 watts downwelling, from the atmosphere overall, including earth based “back” radiation and full sunlight infrared downwelling.
What I’m encouraging the typical scientifically oriented reader to do is ask themselves how it’s possible for so many kooky claims to come from people who have even a loose grasp of the realities of earth/atmospheric energy.
Curt says:
April 1, 2014 at 7:59 am
“Downwelling” radiation, by definition, does not include incoming from the sun. How can we tell the difference? Because the spectra are totally different – there is virtually no overlap. Solar insolation includes a lot of shortwave infrared, but virtually no longwave (past, say 3um). Downwelling from the atmosphere is in the longwave infrared, with virtually no shortwave infrared. Measurements of this “downwelling” flux specifically block out the shorter wavelengths to isolate the longwave.
What Willis and others are talking about, and what was measured in the link you gave, was the longwave infrared, specifically toexclude the solar input.
The 400 W/m^2 Willis has been talking about is the typical upwelling flux density from the earth’s surface. The 324 W/m^2 typical downwelling longwave yields a difference of 76 (these are only very rough averages, of course), which is the NET radiative HEAT transfer between the surface and the atmosphere. Of course, if the atmosphere were transparent to longwave infrared, there would be no downwelling longwave flux, and the earth’s energy balance would be entirely different.
The link you provide shows the downwelling longwave infrared flux density varying between a daytime peak of about 350 W/m^2 – right where cited – and a nighttime low just below 300. I’d say an average of 324 W/m^2 is perfectly plausible given this data, wouldn’t you?
Sorry James, I’m that individual reader, that thinks you’re a pompous wanker. Have a nice day. By the way Curt rules!
Curt has said to James somewhere (apparently).
“The link you provide shows the downwelling longwave infrared flux density varying between a daytime peak of about 350 W/m^2 – right where cited – and a nighttime low just below 300. I’d say an average of 324 W/m^2 is perfectly plausible given this data, wouldn’t you?”
Trendies Trip of the Light Fantastic Cartoon shows 168 (x~4 in all cases below as well) of Solar heat being absorbed by the surface from which 102 goes to thermal losses and so leaving only 66 available for surface radiation be it from cold ice through to hot Tropical surfaces and which can only heat the atmosphere by the amount provided. So to that 66 we can at best add say half of the Solar heat lost to the atmosphere at 34 (34 up and 34 down of course) and so arrive at a total flux of ~100 plus (perhaps) half (again) of the thermal loss to give at the most 150W/m2 available for DWIR back radiation – this however will be at much lower than ambient temperature than most of the surface upon which it will arrive and so then act as a cooling flux and not heating – Neither Water Vapour nor Co2 absorb nor radiate in the “Comfort Zone” below body heat and above freezing – I don`t think!
So unless you “Believe” that photons from a cooler source can accumulate to heat a warmer one upon which they fall and could be in trouble were you a financial accountant of such practice I think the IPCC and its accolytes look wrongly upon the net effect of GHG`s.
rgbatduke says, April 1, 2014 at 8:15 am:
“In the end, though, yes, if there is differential absorption of the atmosphere between SW and LW radiation, there is a significant GHE.”
The glaring problem with this statement is that the earth’s atmosphere (by the presence of the so-called ‘GHG’) actually absorbs a lot more radiative heat coming in from the sun than going out from the surface. You need only look at those famous (infamous?) global energy budget diagrams to see that. According to the numbers from Stephens et al. 2012 for instance, the atmosphere absorbs 75 W/m^2 of the incoming radiative heat, but only [398-345.6-20=] 32.4 W/m^2 of the outgoing radiative heat. (And as we all should know, HEAT (& work) is what ‘heats’ something. It is that ‘net’ flux that actually transfers HEAT (from sfc to atm), not those postulated individual radiative fluxes going up and down. They would simply spontaneously make up the heat.)
http://curryja.files.wordpress.com/2012/11/stephens2.gif
Well, 75 is a number a little bit more than 2.3 times larger than 32.4.
On top of this, the presence of ‘GHGs’ in our atmosphere, primarily through H2O, raises earth’s global albedo (0.3) far above the moon’s (0.13), causing between 55 and 60 of the W/m^2 worth of radiative heat coming in from the sun that would otherwise have been absorbed by the earth system (mostly by the surface), to be instead reflected directly back out to space.
How is this atmosphere warming the surface of the earth compared to a ‘non-GHG’ situation?
An atmosphere on top of a solar-heated surface would warm (have energy (heat) transferred to it) with or with without the presence of ‘GHGs’, through other heat transfer mechanisms than the radiative one. It could however not cool (get rid of this transferred energy (heat)) properly to space without the presence of ‘GHGs’. Because in this case, radiation is the only way. So what atmospheric gases really ‘trap’ heat from the surface? It is of course those that make up 99.5% of it: N2, O2 and Ar, that are able to absorb heat from the surface (conductively/convectively), but not adequately able to shed it to space (radiatively).
Putting ‘GHGs’ into an atmosphere does not enable it to warm. It enables it to cool.
=== === ===
Finally, think about this:
Why will a solar-heated surface naturally warm some extra once you put a massive atmosphere on top of it?
It’s all to do with the weight of the atmosphere on the surface. As soon as you insert the atmosphere between the solar-heated surface and space, there will be conductive/convective losses in addition to the radiative ones. But these losses work only by the effective movement of heated air away from the surface. So it is an inherently slow process. The atmosphere ends up functioning as a ‘conductive’ (in reality a ‘convective’) insulation layer on the surface, which can no longer release its absorbed energy as readily as before.
So it has to warm from the S-B temperature (that is, it will accumulate energy) to attain an ultimate balance between incoming and outgoing.
Ask yourself: Will an earth surface with an equally heavy atmosphere resting on top of it and with an equal input from the sun, but with a mean global temperature of only -18C (255K), manage to run an equally efficient convective ‘engine’ as the one we have at +15C (288K)?
And if it can’t, what will happen in between?
What if you made the atmosphere much lighter, same input? What would happen then?
rgbatduke says, April 1, 2014 at 8:15 am:
This model is without a doubt an oversimplified one, but it suffices to disprove the most often complaints of people that don’t understand thermodynamics (…)”
We know the Laws of Thermodynamics perfectly well, Robert. That’s the very reason why we can point out to you exactly how you violate them.
“(…) — that the effect described in no way violates the first or second laws of thermodynamics (…)”
The effect doesn’t violate them, Robert. Listen to me, it is your description of how this effect comes to be that violates (both the 1st and the 2nd) Laws of Thermodynamics.
It does not come about by adding more energy to the hot system (increasing the input), heating it from cold. It works by making less energy go out from the hot system, reducing its cooling (decreasing the output). To accomplish this all you need to do is make the temp gradient away from it smaller than before (T_2 larger relative to T_1).
It is your flawed interpretation of the radiative heat transfer equation that makes you violate the Laws of Thermodynamics. You see it as two individual Stefan-Boltzmann equations in one. It’s not. Well, mathematically it is. Physically, it isn’t. It describes ONE integrated, indivisible process. P/A (the heat) is the only answer, the only real flow of energy we find.
Recognise that the transfer of heat is ONE spontaneous and continuous process that cannot be divided into two separate heat fluxes going in opposite directions, and your problem is fixed.
Nope! David swuk goofed………………..
From the 150 DWIR deduct half of the uprising IR at 66 to revise the DWIR to 117W/m2 pl.
I too invite readers to compare James’ and my claims in the above threads. It will reveal that James has absolutely no idea what he is talking about when it comes to radiative heat transfer.
On the most basic level, no matter how many times it is pointed out to him, he does not (cannot?) understand the difference between GROSS radiative power output and NET radiative power transfer. Willis has been talking about GROSS outputs, as has been emphasized multiple times, and James thinks he is talking about NET. The difference is covered on the second or third page of the first chapter on radiative heat transfer in any text.
On to the latest point of contention: the difference between the sun’s radiative output spectrum and the earth’s. I said, “the spectra are totally different – there is virtually no overlap. Solar insolation includes a lot of shortwave infrared, but virtually no longwave (past, say 3um).”
James misquotes me multiple times (James – when you claim somebody said something they didn’t say, and put it in quotes, that’s called LYING.) and talks about the sun’s emissions. “Insolation”, the term I used, is defined as the received radiation. What’s the difference? Only about 150 million kilometers! And due to this little phenomenon called the inverse square law, the radiative flux density is about a factor of 50,000 lower at the earth than at the sun’s surface. But what’s a factor of 50,000 between friends, right?
Only about 2% of the sun’s spectrum is at wavelength’s longer than 3um, and the large majority of that is between 3um and 4um. Typically, measurements of the downwelling longwave infrared start at 4.5um, where less than 0.5% of the sun’s spectrum lies. So with a total radiative flux density from the sun of 1365 W/m^2 at earth, only about 6 W/m^2 is in the range measured for DWLWIR.
So when James says of these measurements, “That’s not ‘back radiation’ that’s infrared radiation primarily, from direct solar downwelling”, talking about measurements on earth that show over 300 W/m^2 DWLWIR (over 4.5um wavelength), he is completely and utterly wrong.
Here is a good plot of the difference between the sun’s spectrum (at earth’s distance) and earth’s own spectrum:
http://labspace.open.ac.uk/file.php/5177/moddata/resource/62834/Items/S250_3_004i.jpg
(By the way, James, I have never gotten such stringent security warnings – from multiple browsers – as on the link you provided.)
Maybe I can help James with an simple explanation using net amounts of energy. Energy in minus energy out equals zero. Using the KT figures we have 168 w/m2 input. We have 3 ways to lose this energy. Thermals (24 w/m2) Latent heat (78 w/m2) Radiation (66 w/m2).
Therefore we have 168-24-78-66= 0
Go Whitecaps!! said:
“We have 3 ways to lose this energy. Thermals (24 w/m2) Latent heat (78 w/m2) Radiation (66 w/m2).
Therefore we have 168-24-78-66= 0”
That’s not right because only radiation gets out to space.
Thermals only release radiation to space from GHGs and aerosols lifted up within them. The rest of their energy gets returned to the surface in adiabatic descent for radiation out from there.
Latent heat is contained within thermals when water vapour is present but it only releases radiation to space from condensate such as clouds and raindrops. The rest of the latent heat energy gets back to the surface on the subsequent descent of air after the condensate has been removed because the dry adiabatic lapse rate on the descent is twice the wet adiabatic lapse rate on the ascent.
In effect ALL radiation to space is either from the surface or from GHGs, aerosols, clouds and raindrops.
Anything that radiates out to space from within the atmosphere causes less convection within the atmosphere which leaves surface temperature unaffected.
The reverse is also true which is why the only effect from GHGs is a change in convection rates whether the net effect be warming or cooling.
CURT – said at 7-44am2Apr.
%3Bhttp%253A%252F%252Fscienceofdoom.com%252F2010%252F01%252F20%252Fco2-%2525E2%252580%252593-an-insignificant-trace-gas-part-two%252F%3B480%3B303
“Believe” me???
No bud because if you were playing straight you would not have fished out from all the others the graph that presents the BB emissions of Sun and Earth side by side without reference to relative size which I think is 10 the power of six, Sun over Earth, nor the one that shows the absorption lines that verify the ~200W/m2 Solar IR taken out by the cold atmosphere and so then beamed down among the relatively paltry amount of rebounded Up-rising IR/LW as one can easily infer from another graph detailing Solar intensity rating of 15,000 units max.against the Earths 0.05max. These graphs are referenced “Marble in Space” – “The Habitable Planet”- “Co2, an Insignificant Gas?”
You can find `em all @ur momisugly
………..but you know that already don`t you: Curt(ains!).
David, you are making the same mistake I explained to James that he made, which means that you don’t understand the argument at all. So let’s break it down.
The sun’s spectrum is very close to that of a black body at 5770K, which means that the radiative power flux density is sigma * T^4 = 62.8 million W/m^2 AT THE SUN’S SURFACE. But this radiation spreads out according to the inverse square law, so that each doubling of distance reduces the density by a factor of 4.
The sun’s own radius is 700,000 km. The earth’s orbital radius is 150,000,000 km. So the radiative flux density from the sun AT EARTH is about:
Qearth = 62,800,000 * (700,000)^2 / (150,000,000)^2 = 1368 W/m^2
This figure for the power flux density of the solar radiation at the top of earth’s atmosphere is utterly uncontroversial. It has absolutely nothing to do with any real or imagined greenhouse effect.
In all of the plots you referenced, as well as the one that I referenced, the fraction of the solar output at wavelengths longer than 4.5um is minuscule. Referencing the tables in one of my heat transfer textbooks, it is less than 0.5%, or 1 part in 200.
At the sun’s surface, this is still a high number. But at the earth, it is only 1368/200, or about 6 W/m^2. If the atmosphere filters any of this out, it is an even lower number So James’ claim that daytime measurements of downwelling longwave infrared radiation of 300 W/m^2 or more, which measure at wavelengths longer than 4.5um, are primarily from the solar radiation, is completely false.
Curt you’re exactly right about that and as soon as I started talking about the various spectra relative to the pyrgeometer Willis showed, I was making error after error.
Curt says:
April 2, 2014 at 5:45 pm
David, you are making the same mistake I explained to James that he made, which means that you don’t understand the argument at all. So let’s break it down.
The sun’s spectrum is very close to that of a black body at 5770K, which means that the radiative power flux density is sigma * T^4 = 62.8 million W/m^2 AT THE SUN’S SURFACE. But this radiation spreads out according to the inverse square law, so that each doubling of distance reduces the density by a factor of 4.
The sun’s own radius is 700,000 km. The earth’s orbital radius is 150,000,000 km. So the radiative flux density from the sun AT EARTH is about:
Qearth = 62,800,000 * (700,000)^2 / (150,000,000)^2 = 1368 W/m^2
This figure for the power flux density of the solar radiation at the top of earth’s atmosphere is utterly uncontroversial. It has absolutely nothing to do with any real or imagined greenhouse effect.
In all of the plots you referenced, as well as the one that I referenced, the fraction of the solar output at wavelengths longer than 4.5um is minuscule. Referencing the tables in one of my heat transfer textbooks, it is less than 0.5%, or 1 part in 200.
At the sun’s surface, this is still a high number. But at the earth, it is only 1368/200, or about 6 W/m^2. If the atmosphere filters any of this out, it is an even lower number So James’ claim that daytime measurements of downwelling longwave infrared radiation of 300 W/m^2 or more, which measure at wavelengths longer than 4.5um, are primarily from the solar radiation, is completely false.
I had misinterpreted what I thought you said by not reading it Curt
This comes from trying to mix pyrgeometer discussion with the over-arching principles of whether it’s possible for the surface of the planet to emit 80% of it’s energy through radiant transfer which is of course impossible.
Adiabatically warmed descending air needs neither to warm the surface nor inhibit surface cooling.
All it needs to do is return the temperature of the air at the surface to the temperature of the surface itself.
It achieves that on completion of the first cycle of convection.
The point being that once the temperatures of the surface and of the air above it are the same then no further conduction to the air can occur because conduction only occurs when there are temperature differences.
That is important because only by diverting radiation to conduction can one increase surface temperature because conduction is slower than radiation so if conduction stops increasing then the surface temperature stops rising.
The ability to conduct is a property of mass and is independent of the radiative properties of that mass.
Thus the greenhouse effect is caused by conduction alone which increases surface temperature for the Earth from 255K (or whatever) by 33K.
Only an energy transfer mechanism that is slower than radiation can increase surface temperature above the S-B prediction.
Whilst the atmosphere continues to recycle a fixed amount conducted energy up and down via convection no further surface temperature increase can arise.
DWIR does not increase the amount of conduction that can occur and thus cannot slow down the rate of energy transmission through the Earth system and so cannot raise surface temperature more than the 33K already caused by conduction.
Instead there are changes in convection which negate any thermal effects from GHGs, aerosols, clouds, ice crystals or raindrops.
“This comes from trying to mix pyrgeometer discussion with the over-arching principles of whether it’s possible for the surface of the planet to emit 80% of it’s energy through radiant transfer which is of course impossible.”
Pyrgeometers do not measure DWIR.
They measure the temperature of the air at the height at which they are designed to treat optical depth as a solid surface.
That is how one gets them to focus on the surface of a solid object which it is intended to measure remotely.
Pointed at a fully transparent atmosphere they record the temperature of space.
Pointed at a fully opaque atmosphere they record the temperature of the air at the instrument.
Pointed at a cloud they record the air temperature at the height of the cloud.
In every case the temperature recorded will be set by the lapse rate slope and not DWIR.
Stephan says: “That’s not right because only radiation gets out to space”
If I was discussing radiation to outer space you would be correct. However, I was discussing surface energy transfer into the atmosphere as per the KT diagram. Radiative energy balance into outer space would be 235 w/m2 as per the KT diagram versus 168+67 w/m2 input.
Of course you do not believe in GHG acting as a absorber/emitter of energy so this explanation is moot.
James Rollins Jr says:
April 1, 2014 at 7:06 pm
James, I explained this to you above. You completely ignored it. I asked you to respond to it. You have not done so. Here is the link again.
Your comments on my explanation would be interesting. Your endless, mindless attacks? Not so much …
w.