Guest Post by Willis Eschenbach
Once again, the crazy idea that downwelling longwave radiation (DLR, also called infra-red or IR, or “greenhouse radiation”) can’t heat the ocean has raised its ugly head on one of my threads.
Figure 1. The question in question.
There are lots of good arguments against the AGW consensus, but this one is just silly. Here are four entirely separate and distinct lines of reasoning showing that DLR does in fact heat the oceans.
Argument 1. People claim that because the DLR is absorbed in the first mm of water, it can’t heat the mass of the ocean. But the same is true of the land. DLR is absorbed in the first mm of rock or soil. Yet the same people who claim that DLR can’t heat the ocean (because it’s absorbed in the first mm) still believe that DLR can heat the land (despite the fact that it’s absorbed in the first mm).
And this is in spite of the fact that the ocean can circulate the heat downwards through turbulence, while there is no such circulation in the land … but still people claim the ocean can’t heat from DLR but the land can. Logical contradiction, no cookies.
Argument 2. If the DLR isn’t heating the water, where is it going? It can’t be heating the air, because the atmosphere has far too little thermal mass. If DLR were heating the air we’d all be on fire.
Nor can it be going to evaporation as many claim, because the numbers are way too large. Evaporation is known to be on the order of 70 w/m2, while average downwelling longwave radiation is more than four times that amount … and some of the evaporation is surely coming from the heating from the visible light.
So if the DLR is not heating the ocean, and we know that a maximum of less than a quarter of the energy of the DLR might be going into evaporation, and the DLR is not heating the air … then where is it going?
Rumor has it that energy can’t be created or destroyed, so where is the energy from the DLR going after it is absorbed by the ocean, and what is it heating?
Argument 3. The claim is often made that warming the top millimetre can’t affect the heat of the bulk ocean. But in addition to the wind-driven turbulence of the topmost layer mixing the DLR energy downwards into lower layers, heating the surface affects the entire upper bulk temperature of the ocean every night when the ocean is overturning. At night the top layer of the ocean naturally overturns, driven by the temperature differences between surface and deeper waters (see the diagrams here). DLR heating of the top mm of the ocean reduces those differences and thus delays the onset of that oceanic overturning by slowing the night-time cooling of the topmost layer, and it also slows the speed of the overturning once it is established. This reduces the heat flow from the body of the upper ocean, and leaves the entire mass warmer than it would have been had the DLR not slowed the overturning.
Argument 4. Without the heating from the DLR, there’s not enough heating to explain the current liquid state of the ocean. The DLR is about two-thirds of the total downwelling radiation (solar plus DLR). Given the known heat losses of the ocean, it would be an ice-cube if it weren’t being warmed by the DLR. We know the radiative losses of the ocean, which depend only on its temperature, and are about 390 w/m2. In addition there are losses of sensible heat (~ 30 w/m2) and evaporative losses (~ 70 w/m2). That’s a total loss of 390 + 30 + 70 = 490 w/m2.
But the average solar input to the surface is only about 170 watts/square metre.
So if the DLR isn’t heating the ocean, with heat gains of only the solar 170 w/m2 and losses of 390 w/m2 … then why isn’t the ocean an ice-cube?
Note that each of these arguments against the idea that DLR can’t warm the ocean stands on its own. None of them depends on any of the others to be valid. So if you still think DLR can’t warm the ocean, you have to refute not one, but all four of those arguments.
Look, folks, there’s lot’s of good, valid scientific objections against the AGW claims, but the idea that DLR can’t heat the ocean is nonsense. Go buy an infrared lamp, put it over a pan of water, and see what happens. It only hurts the general skeptical arguments when people believe and espouse impossible things …
w.
kuhnkat says:
August 23, 2011 at 7:04 pm
“Tim and gnomish,
before worrying about how to sneak between those hot DLR’s, you might consider exactly how much IR is radiated to the water by the device itself!”
Interesting question. I hadn’t specifically thought about that because I assumed it was small. Let’s see …
Emissivity of aluminum foil is ~ 0.04 (http://www.engineeringtoolbox.com/emissivity-coefficients-d_447.html). That ought be be pretty close the the value for the shiny aluminum they used.
Let’s assume the foil is as hot as 300 K (highly unlikely on a cool desert night when this was being used).
The radiation from the device itself would be
On a hot day, this could get a bit higher, but the whole point was using this during cool nights (especially in the desert). Now the emissivity could be a bit higher (especially if it gets dirty). I suppose the number could be 40 or 50 W/m^2 in real-world situations.
Compared to 300 W/m^2 or more of IR from the ground that is being blocked, the radiation from the foil is pretty minimal.
300W/m^2 is like 3 100 Watt bulbs every square yard – that seems unrealistic at night.
btw – thermometers of any kind, including IR detectors – do not measure heat.
temperature is not heat and degrees can not be converted to watts. i don’t think you can properly calculate watts via the IR radiative temperature calculation.
http://www.sciencephoto.com/media/356062/enlarge
this thing is incandescent but provides very little heat.
Gnomish, Re:
That’s very interesting, but I don’t think incandescence is applicable in your example. By definition incandescence relies on a major heat source, whereas many other low energy light sources do not. (E.G. glow-worms or my audio system remote control buttons, providing that there has been exposure to light during the day in the latter case)
Check out for example:
http://en.wikipedia.org/wiki/Luminescence
The sun is rather incandescent, but don’t look directly at it!!!!!!!!!!!!!
jae says:
August 23, 2011 at 7:43 pm
I have a life, a job, and do a host other things. The sun has been shining, so I have been painting the house. I don’t run according to your desires. I follow the weather, my dreams, and my own clock. I answer certain posts and let others go, based on considerations of which you are totally ignorant, just as I am ignorant of your reasons and considerations regarding which posts you reply to.
Sometimes I stick my head into some investigation of something like the TAO/TRITON buoys and I don’t come up for air for couple days. And sometimes I just like to let the discussion develop for a while.
If you were a cowboy you’d know that calling me chickenshit, just because I don’t do things according to your whims, would get you invited off the ranch pronto.
Here, people just point and laugh.
w.
Willis Eschenbach @ur momisugly August 24, 2011 at 12:32 am
In the time you spent evading JAE’s questions, why not instead respond at least in part, or say something like; you will get back to him soon when you have more spare time?
Why do I ask: Because I think jae’s questions are important and I’d like to know your determinations, as would maybe others.
Bob FJ
LWR further heating the surface is fiction. Supporters believe based on faith not science, evidence or logic. JAE will never receive satisfactory answers.
Slowly more and more with see the GHG backradiation theory for the nonsense it is. But it will take time for all warmists (luke and alarmists) to let this go.
gnomish says:
August 23, 2011 at 9:15 pm
“300W/m^2 is like 3 100 Watt bulbs every square yard – that seems unrealistic at night.”
Could you give some numbers to back up this impression? What calculations make 300 W/m^2 seem wrong? What do you think is wrong with my calculations?
Bob_FJ says: August 23, 2011 at 11:59 pm
Incandescence is exactly applicable — since it is a hot glowing object.
One reason he can hold it is that it has very poor thermal conductivity, so the corners can get rather cool while the center is still hot. . Another reason is that silica has good transmittance of visible light, but the transmittance gets much worse as you move into the infrared range (http://www.sciner.com/Opticsland/FS.htm). So if the center is still warm, the visible light can get out, while the infrared is blocked, again limiting the energy transmitted to his hand. Both of these properties help make it possible to see the hot glow while not getting burned.
RJ says:
August 24, 2011 at 3:27 am
“LWR further heating the surface is fiction. Supporters believe based on faith not science, evidence or logic. JAE will never receive satisfactory answers.”
If you think it is important, why don’t you provide the answers JAE wants? Find the temperatures of greenhouses in Guam and Phoenix. Explain these temperatures in terms conduction, convection, and radiation balance based on the conditions in Guam and Phoenix. Estimate the LWR in both locations and explain what effects, if any, this has on the temperatures of the two greenhouses.
Belated thanks, Willis. I never accepted “100% of the energy increase goes into evaporation” argument. The rate of evaporation at a water surface is determined by water & air temp, air humidity & pressure, water & air movement, etc. It doesn’t correlate w/the wavelength of the affecting radiations.
beng says:
August 24, 2011 at 6:39 am
The rate of evaporation at a water surface is determined by water & air temp, air humidity & pressure, water & air movement, etc. It doesn’t correlate w/the wavelength of the affecting radiations.
Yes. This is why we can’t know whether a small change in the net LR flux (if it has happened) affects evaporation rates. It will be lost in the noise of changes in the convection, pressure, humidity etc. Lots of feedbacks are in operation, so we don’t know if the non-feedback theoretical calculation for an increase in DLR for co2 has done anything or not.
However, we do know that heat isn’t conducted from cooler to hotter across the ‘skin’ of the ocean. And we know that when wind disrupts the skin, it also causes more evaporation, so DLR plus wind isn’t going to heat the ocean. And we know natural convection doesn’t happen upside down. And we know IR is stopped within 0.05mm of the surface of the water.
Konrad’s empirical experiment further supports the thesis that changes in DLR rates don’t make much difference to the cooling rate, unless evaporation is suppressed. Although his experiment didn’t include a turbulent surface, my own empirical test shows that in average conditions there is insufficient vorticity at the ocean surface to mix heat downwards against the natural buoyancy of warmer water.
http://www.john-daly.com/forcing/forcing.htm is worth a read.
Tallbloke,
I agree with most of what you wrote at 7:33 AM, but I still disagree with your conclusion — at least to some extent.
You said “we do know that heat isn’t conducted from cooler to hotter”
I’ll go a little farther and say “the greater the difference between hot and cold, the more heat (thermal energy) gets transferred.”
The ~ 0.2-0.3 K temperature gradient across the skin is sufficient to allow conduction of ~170 W/m^2 of heat. This happens to be the energy deposited in the bulk of the ocean (below the skin layer) by solar radiation, so this conduction is sufficient to keep the bulk ocean.
Even a small change in the gradient across the surface will result in a change in the ~ 170 W/m^2 of conduction thru the skin. If the top of the skin warms and the gradient across the skin is cut in half, the conduction up thru the skin will also cut in half (give or take a little).
One way to warm the top of the skin would be to add a little IR to the surface. This IR will raise the surface temperature resulting in 1) more evaporation, 2) more upward IR and 3) less energy loss from the lower parts of the ocean. If less energy is lost from the lower levels while still receiving the same solar energy, the result will necessarily be rising temperatures in the lower levels.
==================================
Konrad’s experiments do seem to show that this effect may be small (ie the IR energy goes mostly into increased IR & evaporation and not much into raising the temperature at the top of the skin, so there is little change in conduction out of the bulk). I tried quantified the magnitudes of he energy flows earlier in the discussion and concluded that the effect might be too small to see with a set-up like Konrad’s. I would love for someone else to check my numbers and provide alternate estimates of the energys and cooling rates involved.
Bob_FJ says:
August 24, 2011 at 1:52 am
Bob, what part of my following answer to jae didn’t you understand?
Read it again real slow if you have a problem, I’m glad to answer questions about it.
In particular, I don’t take ethical instruction from gerbils who accuse me of “evasion” or vermin who call me “chickenshit”, nor do I answer the questions they want me to answer.
Should I have said that I will “get back to [jae] when I have more time”? No, because that would be a lie. I don’t have either the time or the slightest desire to answer people like you and jae, and I doubt if I ever will. You go to the bottom of my list, and if I have time when I’ve finished answering every other possible post, and I’m done painting my house, I’ll get to you then.
Don’t hold your breath …
w.
The real reason why I’ve not answered a host of comments on this thread is simple. I can’t figure out what else to say. Here’s one more shot at it.
Various people keep saying over and over that DLR can’t possibly heat the bulk of the upper ocean.
Despite that claim, the bulk of the upper ocean is much warmer than it would be if heated by solar energy alone. Solar energy absorbed by the ocean is only about 170 w/m2. This is only sufficient to heat the ocean to minus 40°C (or F) or so, and that’s frozen very solid.
So if the DLR isn’t warming the bulk of the upper ocean … then what is?
When someone comes around to answer that, I’m interested. Until then, your explanations don’t explain that, and I’m not interested.
w.
[Edited to add] PS – I don’t care if you call it “warming” or “slowing the cooling”. To me, since the ocean is warmer than it would be in the absence of DLR, I say it warms the ocean. But you can call it what you like, THE END RESULT IS THE SAME no matter what name you give it.
“So if the DLR isn’t warming the bulk of the upper ocean … then what is?”
Increased solar shortwave input during the late 20th century when global cloudiness and albedo both reduced.
DLR has but a miniscule effect in comparison and is readily dealt with by increased evaporation, convection, conduction and radiation for a faster/larger water cycle and a miniscule adjustment in the surface air pressure distribution.
Insignificant and unmeasurable compared to the natural solar and ocean induced shifts in the surface air pressure distribution.
willis, can you justify the conversion of thermal IR signature (a temperature proxy reading) to watts? if that is what you are doing, it is a crucial error.
Stephen Wilde says:
August 24, 2011 at 10:34 am
Check your numbers. There’s nowhere near enough there in all of the solar, large albedo or small. Solar is about 170 w/m2. The ocean radiates about 390 w/m2, never mind sensible and latent heat loss. The ocean (being at general thermal equilibrium) must receive as much as it radiates.
What makes up the difference of several hundred watts per square metre?
w.
gnomish says:
August 24, 2011 at 11:25 am
No, but Stefan and Boltzmann can justify it. Check Wikipedia if the mathematics is too much, they’ll likely have a simpler explanation. Briefly, the radiation (watts per square metre) is proportional to the temperature to the fourth power.
w.
“So if the DLR isn’t warming the bulk of the upper ocean … then what is?”
The sun of course.
As explained in this Joseph Postma paper.
climaterealists.com/index.php?id=7457
Stephen,
You missed Willis’ point. He is not addressing the question “What raised the average SST from 18 C to 18.5 C over the last 100 years” (or whatever the actual numbers are). He is addressing the question “What in general has raised the to around 18 C to begin with, since 170 W/m^2 of average solar energy alone would predict an average temperature well below freezing”.
Stephen Wilde says:
August 24, 2011 at 10:34 am
“So if the DLR isn’t warming the bulk of the upper ocean … then what is?”
Increased solar shortwave input during the late 20th century when global cloudiness and albedo both reduced.
DLR has but a miniscule effect in comparison and is readily dealt with by increased evaporation, convection, conduction and radiation for a faster/larger water cycle and a miniscule adjustment in the surface air pressure distribution.
Insignificant and unmeasurable compared to the natural solar and ocean induced shifts in the surface air pressure distribution.
I agree with nearly all of this except that it is a small change in DLR that has but a miniscule effect in comparison…
Willis Eschenbach says:
August 24, 2011 at 10:23 am
Various people keep saying over and over that DLR can’t possibly heat the bulk of the upper ocean.
Despite that claim, the bulk of the upper ocean is much warmer than it would be if heated by solar energy alone. Solar energy absorbed by the ocean is only about 170 w/m2. This is only sufficient to heat the ocean to minus 40°C (or F) or so, and that’s frozen very solid.
When someone comes around to answer that, I’m interested. Until then, your explanations don’t explain that, and I’m not interested.
DLR doesn’t “heat” the upper ocean bulk, but the LR flux does slow the rate of cooling of the upper ocean bulk via it’s support of the adiabatic lapse rate of the atmosphere, and this is why the ocean is as warm as it is. This observation is much more than a disagreement over semantics. The substantive arguments put forward in this thread which seek to demonstrate that DLR does not directly “heat” the ocean bulk have merit. The only way changes in DLR can affect the temperature of the upper ocean bulk is via a change in the differential between surface air temperature and ocean surface temperature. This is a very, very slow way to change the temperature of the bulk of the ocean. It’s certainly not going to account for the change in ocean heat content or surface temperature 1980-2003, even though it explains why the ocean is warmer than it would be under an atmosphere devoid of radiatively active gases.
Even then, there is considerable uncertainty over the degree to which additional co2 might have changed that differential, if it has changed it at all. This is because despite the theoretical non-feedback increase in air temperature an extra 120ppmv of co2 could bring about, negative feedbacks empirically observed from satellite data by Roy Spencer and Richard Lindzen and their co-authors have substantially reduced the non-feedback value, and so the Earth’s response to this additional co2 is probably very small indeed.
Read it again real slow if you have a problem
Please stop it with this obnoxious, arrogant numpetry, I much prefer the old Willis who came up with a brilliant hypothesis about the way thunderstorms in the tropics regulate the amount of energy shooting up through the troposphere, bypassing the radiatively limited ‘atmospheric window’.
Tim Folkerts,
“Compared to 300 W/m^2 or more of IR from the ground that is being blocked, the radiation from the foil is pretty minimal.”
Hmm, by morning it wouldn’t be 300 w/m^2, but, I think you might have caught me there. The tinfoil will be radiating less than the ground which would be an improvement.
I just ran across something I am confused about. In the SpectralCalc calculator it lists Radiance and Radiant Emittance. I looked up the definitions and Radiance seems to be defined as the radiation in one direction and the Radiant Emittance is in all directions. When we are working with a surface, wouldn’t that be Radiance instead of the Radiant Emittance which would be a gas particle or something radiating in all directions? Or, since even a surface will be radiating in a hemisphere would it be in between??
Willis Eschenbach said:
“Solar is about 170 w/m2. The ocean radiates about 390 w/m2, never mind sensible and latent heat loss. The ocean (being at general thermal equilibrium) must receive as much as it radiates.”
Ok, with the help of Tim I’ve got the point. One needs the back radiation to add to the 170 to reach and maintain the ocean temperature.
However one then has to take a step back and look at first principles. Is it really GHGs that dictate the level of back radiation that we observe.
Perhaps not. Atmospheric pressure dictates the energy value of the latent heat of vaporisation so it is atmospheric pressure that dictates the rate at which energy can leave the oceans. The more it costs in terms of energy to achieve evaporation the warmer the oceans must become before equilibrium is reached.
So the oceans will build up to whatever temperature is permitted by atmospheric pressure with or without any GHGs in the air at all.
Once that ocean temperature is achieved the energy for the back radiation is then supplied to the air by energy leaving the oceans and NOT by energy coming in from the sun.
So the upshot is that the oceans accumulate solar energy until they radiate 390 at current atmospheric pressure, at that point 170 continues to be added by solar but to balance the budget the atmosphere by virtue of its density back radiates whatever is necessary to achieve balance.
A feature of GHGs is that they add to back radiation proportionately more than other gases in the atmosphere but in the end it is surface pressure that controls the energy value of the latent heat of vaporisation which is the ultimate arbiter of what rate of energy transfer can be achieved from oceans to air.
So if GHGs add a surplus to the back radiation over and above that dictated by surface pressure the system has to make an adjustment but what it cannot do is alter the energy value of the latent heat of vaporisation. So instead it is the rate of evaporation that must change to balance the budget in the absence of a significant change in surface pressure.
Do you see the point ?
Back radiation is a consequence not of atmospheric scattering of incoming solar shortwave but rather primarily a consequence of atmospheric density slowing down energy loss from sea surface to space.
So if one increases atmospheric pressure at the surface the amount of energy required to provoke evaporation at the sea surface rises and the equilibrium temperature of the whole system rises including the amount of back radiation.
The opposite if one decreases atmospheric pressure at the surface.
We have been looking at back radiation from the wrong point of view.