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.
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The choice of an infrared lamp as a heat is not the best experiment – too much visible light. Put a just-red-hot heating element over the pan of water. The point is to try to heat without visible radiation.
The heater will send out LWR and it will not get nearly as far as 1mm into the water because it is very effective at stopping it penetrating at most IR frequencies. The water will get very much hotter at the surface than a few inches below, unless it is stirred (which of course happens in a real ocean). Water stratifies very well when it is hotter on top. It of course tends to evaporate more even when calm, and when stirred, much more so t here are several considerations.
The 4 arguments seem to mix all frequencies and LWR in together, or shall I say, perhaps do not separate them well enough. Tropical ocean water is definitely heated by the 1 kW/m^2 of incident solar radiation. The question is how much more is it heated by additional LWR (only, not additional sunlight). Well it certainly is not heated deeply by LWR unless there is significant overturning, which in many cases exists, yes?
So, if we are going to live in a real world (and ocean) then we have to consider that there is a great deal of water vapour immediately above the water’s surface absorbing the IR like crazy, remaining heated and not condensing to return, condensed, to the surface. Over a real ocean, the humidity is very high near the surface. How much of the additional LWR reaches the water’s surface, if any? If it does, it will be absorbed in the very top of its surface and promote immediate evaporation in the zone there there is a continuous exchange between the surface and the very bottom of the atmosphere. Any additional LWR that reaches the top of the water will shift the balance to produce slightly more (IR absorbing) water vapour immediately above it. Rapidly too. That thin air-water exchange layer just above the surface is basically in a constant state of saturation or supersaturation and is a really good IR shield.
Please convince me that any of the downwelling IR reaches the surface of the water. I am quite prepared to be convinced and it is essential to the argument that additional downwelling IR can heat the ocean. How much IR hits the water, in Watts? Does this heat flux depend on the local temperature and wind conditions?
Roy Spencer says:
August 15, 2011 at 1:44 pm
The struggle for scientific understanding goes on, my thanks to you as well.
w.
jimmi_the_dalek says:
August 15, 2011 at 1:52 pm
Thanks, Jimmi. For those interested, see my first shot at explaining it, “The Steel Greenhouse“. It shows how a so-called “planetary greenhouse” can be made of steel, and avoids all issues of lapse rates and co2 re-emission and the like.
Still unclear on how a so-called “greenhouse” actually works? I took another stab at explaining it in “People Who Live In Glass Planets“.
Is the top part of that 1 mm heated up to the same temperature as the bottom part or is there a temperature gradient over that 1 mm?
Really? There are people that believe that? How do they have time to post because they must spend all their time rewatching Loose Change.
Without DLR heating the water, there would be no point to Bruce Brown’s Endless Summer. Next.
Yes, back in Sweden when I grew up, that first millimeter didn’t absorbed it all summer long, so it was always solide ice year round….. /sarc
In fact with little tidal change ( 1 foot on average), on a good summer (not too many), the first ten feet would be warm. You could see the thermal layer below if you snorkled.
Heat conduction, most likely?
Wave action, not so likely, it would mix out the thin thermal layer?
Heat radiating down that far? I don’t know, can infrared penetrate that far?
Lastly doesn’t heat radiate in all directions? So, that millimeter would radiate up and down right? So the millimeter below would get some heat that way too, and so on?
For those who doubt the greenhouse effect, here is a standard thermodynamics question.
If you know how to solve this, you know why Willis is correct.
Here is the problem (mechanical engineering profs should feel free to include this on the next thermodynamics exam).
1: A continuously heated, flat plate at 15 C is on one side, a parallel, continuously cooled plate at -273C is 20 meters away. What energy flux is required to maintain the heated plate at 15C under the following conditions:
The atmosphere in between is 10% CO2, 72% N2, 18% O2, 1 bar pressure.
The atmosphere in between is 20% CO2, 64% N2, 16% O2, 1 bar pressure.
2: Solve again, assuming that the energy input to the plate is constant, and determine the temperature of the plate at the higher level of CO2 if the temperature at the lower level is 15C and the second plate remains at -273C.
Now comes the part that seems to be missed by our friends in the climate field:
3: At what level of CO2 does the increase in CO2 no longer result in an increase in temperature of the first plate.
If you studied heat transfer at the university level, you may have seen a question like this. If you did, you would know that the plate would be warmer in the second instance (I am procrastinating at work right now, so will leave it as a blog post later to fully answer) and the level of CO2 would be 25%.
Cheers
JE
But surely the myth about DLR is that it is the tiny fraction of the atmosphere responsible – the less than 1% of the atmosphere that absorbs infrered is not responsible for more than a fraction of DLR. This is the deception that, like a magician diverting your attention – don’t look at that look at thislook at this -from reality to sell you on their theory
Surely the whole of the atmosphere warms and cools predominantly by conduction and convection ? And surely, like everything else in the Universe, the Nitrogen and Oxygen, being at more than absolute zero, constitute the vast bulk of the DLR – ~98% of it ? It must be impossible to seperately detect the tiny amount from GHGs ?
And surely the latent heat of evaporation of water, being some 2500 times the specific heat capacity of CO2, plays a far more important role in energy distribution on earth than DLR ?
Also surely DLR is a small component of the total radiation in the atmosphere with random emission in any direction but surely mostly upwelling following the rising thermal currents ?
So surely on earth radiation plays a minor role in energy distribution ? Else why do common objects such as a car’s “radiator” really rely on conduction and convection ? Why do they put the fan in the oven if radiation is so effective ?
And why can I sit very close to a radiative heater for long periods (not above it though) but when I touch it I’m immediately off to the emergency room ?
The answer must be that radiation, while it may be the only energy transport mechanism through space, is only a minor player on earth ? Sure it is the only escape but there are well known mechanisms for getting the energy up to the upper levels of the atmosphere and radiation is only a small part of that.
As someone else noted it is the term warming. If DWLR doesn’t reverse the direction of net flux it is not warming. There is also the legitimate question of is conductive heat transfer at the surface more significant than radiative heat transfer. Since the radiative situation is liquid water shooting photons at water vapor which shoots back etc., the average 0.8 degree temperature difference between the water and the air seems pretty reliable. With more CO2 that average may become 0.78 degrees.
Willis,
I’m beginning to see that you are a heretic, and I love it. Yes, this falsehood that DLR can’t heat the oceans has been one of the most absurd things that skeptics have said, this, and the notion that human activity has not been the principal driving cause behind the growth of atmosphere CO2 over the past several centuries.
I realize you are not a “warmist” as I am, though some people insist on lumping all “warmist” thought into the C-AGW category. Regardless, you and I might see eye to eye on more things than might first seem apparent.
The problem seems to be a lot of folks who just don’t understand thermodynamics.
Light is energy. If the water absorbs light it absorbs that energy, hence its heat increases. It oes not matter how thick the absorbing layer is.
Radiant heat transfer is not the same as conductive heat transfer. Conduction depends on the ratio of the temperatures. Radiance depends only on the temperature of the radiating body not the temperature of any sink.
Convection in the air is much different than convention in the seas. The lowest layers of air are heated then rise as they expand. In the seas it is the upper layers that heat and expand, but there is nowhere to rise because they are already above cooler denser layers.
An awful lot of Zeno’s paradox going on as well.
The basic physics of GW is relatively sound. The weaknesses lie in the guestimates of sensitivity/forcings.
Nice post . You would never see the flip side of a post like this on a AGW blog ( being critical of a AGW principle ). The true believers would not put up with it. Good science requires that weak hypotheses be appropriately dissected, which this post does.
Of course, the real question is how that energy is then distributed / mixed into the ocean,
There is no doubt that some warming takes place somewhere but the issue is whether that warming does in fact get transmitted downwards and/or whether it does in fact slow down the ‘normal’ rate of energy loss from the oceans.
As far as I can tell the DLR warming just affects individual water molecules at the very surface merely microns deep. Other wavelengths get in deeper however.
DLR having warmed those individual molecules there is an increase in all of convection conduction radiation and evaporation. Effectively all that happens is that the moment of evaporation for all the water molecules affected is brought forward by whatever energy is left over after conduction radiation and convection have taken their portions.and of course evaporation is a net cooling process as we all know.
Willis has previously told me that the increase in evaporation alone is not sufficient to deal with ALL the DLR but suppose the increased evaporation only has to mop up what is left over AFTER increased upward radiation convection and conduction. The figures are then much more believable.
Looking for some evidence one way or the other I read about that 1mm deep layer at the top of the oceans that is always (averaged globally) about 0.3C colder than the ocean bulk below.
The thing is that that layer is still there day and night so it isn’t even overcome by the coming and going of sunlight so I don’t see how DLR would make a difference.
That layer represents the net cooling effect of all surface cooling processes.It is on average globally negative.Energy is always leaving the surface layer faster than it is arriving at the surface and is replaced from below by solar shortwave that penetrated deeper. If the energy hitting the surface from DLR were penetrating downward significantly then that layer would become shallower or warmer or dissipate but on average overall it doesn’t.
So to accept what Willis says I need that point addressing. Why does that cooler layer not seem to get warmer, shallower or dissipate (except locally and temporarily) under the influence of more DLR or even under the influence of solar insolation ?
Could it be that it is a permanent feature of the ocean surfaces set by pressure and density differentials such that it provides a buffer between energy arriving in the topmost molecules and that leaving the ocean bulk for a zero effect on both energy into and out of the ocean bulk ?
I like the analogy of a tributary joining a river. The volume of flow downstream of the junction increases but the rate of flow from upstream is not changed. There may be a small area of buffering (akin to that cool layer on the oceans) where there is a slowdown in the rate of flow but nonetheless the rate of flow from higher upsatream is unaffected.
I suspect that that happens at the ocean surface too.
1DandyTroll says:
August 15, 2011 at 1:22 pm
So a IR lamp directed at a one square meter tub of water of say one meter in depth to radiate the surface at 170W wouldn’t warm that body of water if it was circulating?
If it only heats the first mm why then are several inches usually warm when going swimming? Or is that an odd question?
170W per square meter, a few billion years . . . it hasn’t done all that much though, except around the equator, has it, I mean the north atlantic, the arctic sea and the antarctic sea is cold as bloody hell year around, but where there’s lots and lots of sun the sea is pretty darn cozy all year around.
Its not an odd question its a rather unthinking question.
the LR in DLR is Longwave Radiation. This does not penetrate far at all into water a millimeter or less. However, you may notice you can see in sunlight. This is because sunlight is largely made up of visible and ultraviolet radiation and this spectrum will penetrate really deeply into the ocean provided that it is at the correct incidence (angle of insolation) and is why the light under water looks greeny blue. If the light is at any angle less than about 40 degrees then most of the light reflects from the surface (see Willis’ last post). This reflection of sunlight at low angles of insolation is another reason that the sunlight on the oceans near the poles does not warm the water much (as you pointed out).
So as you say where there is lots of sun the sea tends to stay warm – but even there – the sea surface water will be considerably cooler by dawn having both radiated and evaporated a lot of the previous day’s heat away.
I have just read your steel greenhouse post.
Surely the myth that the earth receives only 235 W/sq m insolation and thus the earth would only be ~minus 18 or 19 C is the big lie of GHG theory.
To model the earth as a disk illuminated by only one quarter of the solar constant is nonsense and we ought to say so. At noon at the equator the insolation is probably at least double the 235 W/sq m (perhaps nearly triple) so often quoted while at one of the poles it is probably close to zero.
The only thing maintaining the poles at the modest temperaturesthey are at compared to absolute zero is the energy transmission of atmospheric and oceanic currents.
I do not believe that at a place like Death Valley or central Australia DLR is responsible for the increase in energy from 235 W/sq m to the ~617 W/sq m necessary to explain a temperature of 50 C as has been observed or the 544 W/sq m required to explain the 40 C temperatures regularly recorded less than 50 km from where I live.
Clearly that energy comes from the sun so why perpetuate this “average” 235 W/sq m myth that the AGW use to distort truth and science ?
Hey – I’m not the one with the cartoon and those examples that suggest the behavior is identical.
@tallbloke
“The question is, do DLR heated water molecules make it downwards far enough for long enough to warm the ocean bulk. I think the answer is no, because warmer water molecules are naturally buoyant”
BINGO!
Give the man a cigar.
Now that I think of it, I have observed sunspots that are shaped much the same as our oceans, like a map cutout, blocking those oceans from being served up as much energy. That would explain why a rock on the beach at the equator is hotter than the ocean waves on that beach, when I touch them. I don’t know how to explain the rabbit and dragon shaped sunspots though…
No matter how patiently you explain things to some people, they won’t get it. Some people will, no matter how hard you try, still believe that radiation from the atmosphere somehow doesn’t heat the ocean. And yet the physics has been understood for hundreds of years, and tested so thoroughly that to doubt it is simply unreasonable.
Are these people unable to understand? Or are they unwilling? That’s the next interesting question.
I notice when I microwave my pasta that the outer layer may become overheated before the center gets warm, that’s why I sometimes use a lower power setting. Sometimes with soup too! Crazy huh?
How did we ever get to the moon?
I wonder how long until “you know who” shows up to comment here?!?
The Science of Doom has the first of a very good multi post series on DLR and the ocean here http://scienceofdoom.com/2010/10/06/does-back-radiation-heat-the-ocean-part-one/
Most of the questions that have been asked and will be asked are answered there.
Willis,
I note with some interest that none of your four arguments match that of the Team. Their offering is that the backscattered LWIR absorbed in the top 1mm cool skin layer of the oceans reduces the thermal gradient across this 1mm, reducing radiative, conductive and evaporative heat losses. Sadly neither their argument or yours appear to have supporting empirical studies.
To much of the AGW doctrine is based on chalk on blackboards and computer models. One thing that many WUWT readers will be aware of is the paucity of empirical testing of the AGW hypothesis. Your suggestion of putting an infra red source over a pan of water was I believe the most sensible part of your post.
This infra red source would need to be emitting only around the 15 micron frequency. The water would need to be salt water at an initial average ocean temperature. An artificial breeze would also be required across the surface of the tank, using air of the appropriate temperature and humidity. A coastal testing location may be appropriate.
I have yet to read a study based on such a test. If you have a link to such a paper Willis, I would greatly appreciate it.
What does it matter? It’s been happening for billions of years without problems, no way is it anthropogenic. Isn’t this a complete red herring in the AGW debate?
Bystander:
In terms of absorbance of radiant energy, the state property of interest is emissivity. Liquid water has an emissivity of about 0.9. Sandstone is closer to 0.7, Basalt 0.7, granite 0.95. So, some land will absorb more radiant energy, including DLR and some will absorb less. Some will indeed be exactly equivalent to water.
Hands – show of hands –
Who HAS swam in Lk Michigan and encountered warm currents on a sunny day?
From whence did they come I wonder?
Anyone – Bueller – Bueller?
.