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.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
So the physical properties of say, rock, and water are identical?
Wouldn’t DLR be absorbed deeper than a mm in water due to the difference between a solid and a liquid?
Great work again, Willis. Would you please take a moment and tell us how Warmista models treat the heat phenomena that you have described as a thermostatic system? With specific regard to infrared radiation, where does your account differ from the Warmista in the way it treats heat and where is there overlap? How do the Warmista models handle what you say about warming from sunlight, if they handle it at all?
I think that the arguement is a question of degree and residence time, not a question of does it heat, but how much? “But the average solar input to the surface is only about 170 watts/square metre.” I am not certain average is what is moat important here. SWR at the tropics and even subtropics is far greater, and because it penetrates far deeper it likely has a much greater residence time. Thus any change in SWR flux may accumulate far more energy over time then a similar W/M2 change in SWR caused by a GHG. Yet I have seen none of this quantified.
http://en.wikipedia.org/wiki/Solar_pond
if i had back issues of mother earth news i could show that this has been in the green literature almost as much as how to raise goats in your basement.
Bystander said:
“So the physical properties of say, rock, and water are identical?”
And I say . . . Huh? Is there a point to your statement? The physical properties of rock (lets say basalt) and rock (lets say limestone) are not identical, so I would suspect that rock and water do indeed differ. What has that got to do with the article?
Bystander, no, but they both absorb longwave IR in the 5-15 micron wavelength range in about a millimeter or less. Strawman argument, no cookie.
Although the end result is the same it is incorrect to state that DLR heats the surface. DLR is radiation that has already left the surface and been absorbed and re-radiated. It is the sun that does the heating. All the DLR does is slow down the heat loss from the surface. Without a heat source such as the sun the surface would gradually cool as the surface flux and DLR decline. So saying DLR heats the surface is not strictly accurate.
In examining surface temperature of night-time compared with day time it can be seen to what portion of the temperature is due to direct IR or remitted IR after absorption.
Imaging if there is a single night with 36 hours rather than 12. The heat loss would be tripled and the temp drop would likely be in the 30 degrees range where I Iive… look at this daily plot:
http://www.cita.utoronto.ca/~rjh/halifax/halifax-weather-ll.html
If night to day has such a huge effect on surface temp…..then why are we torturing ourselves about fractions of a degree? Seems to me the earth has quite a huge capacity to loose heat. We see the effect every night.
I doubt that the earth has chronic heat gain…. heat emission is a forth power of temperature.
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.
gnomish says:
August 15, 2011 at 1:08 pm
Did you get the one where Barry Commoner explained how to heat a 12 story residential building using a V-8 engine in the basement?
Dunno about the rest of the notions, but
Evaporation is known to be on the order of 70 w/m2, while average downwelling longwave radiation is more than four times that amount …
is not apt.
it is not the downwelling LWR that is significant, but the net of LW and SW, (the imbalance) that is either met by another process (convection), or results in a temperature change.
Net longwave and shortwave, in the average, is not more than four times 70 W/m^2.
David says:
August 15, 2011 at 1:08 pm
I think that the arguement is a question of degree and residence time, not a question of does it heat, but how much? “But the average solar input to the surface is only about 170 watts/square metre.” I am not certain average is what is moat important here. SWR at the tropics and even subtropics is far greater, and because it penetrates far deeper it likely has a much greater residence time. Thus any change in SWR flux may accumulate far more energy over time then a similar W/M2 change in SWR caused by a GHG. Yet I have seen none of this quantified.
============================
Yeah, I keep trying to get an answer to this question too (I think it’s part of the same question). What is the change in DLR over the tropical water vapor-containing atmosphere with 390 ppm of CO2, versus the tropical water vapor-containing atmosphere with 280 ppm of CO2, including Doppler Shift effects on the water vapor absorption, of course.
And, hate to bring up a long gone painful debate, but if DLR can heat one fluid (water) then it ABSOLUTELY CAN heat another fluid (air) and in EXACTLY the same way. Local thermodynamic equilibrium arguments notwithstanding.
Anybody who swims or snorkels the sun warmed ‘top layer’ in a lake and has felt the distinct thermoclines at colder layers beneath, has already confirmed that the surface water absorbs long wave radiation. After a day or two of moderate to brisk winds, the top layer is cooled, confirming cooling from evaporation and turbulent mixing with even cooler water below the nearest thermocline.
Spouting baseless theories and touting irrational models will never refute the simple and direct confirmation that a few days of open water swimming or near surface water temperature measurements will provide.
DLR cannot be absorbed by the first mm of water because it is clear therefore it must be absorbed by the second mm of water.
DLR cannot be absorbed by the second mm of water because it is clear therefore it must be absorbed by the third mm of water.
Actually DLR cannot be absorbed by any of the water because it is mm all the way down.
/sarc
Glad to see someone else take the flak for this for a change. Thanks, Willis. 😉
-Roy
Hi Willis,
Argument one asks what the difference is between rock and water. Warm water molecules rise to the top. Warm rock molecules conduct heat to their neighbours, which can’t go anywhere.
Argument two asks where the energy goes. The answer is:
space.
Argument three is not an argument that DLR can warm the ocean, it’s an argument that it can slow its rate of cooling.
Argument four is a numerical misunderstanding. The ocean surface very efficiently absorbs 95% of DLR, and promptly re-emits half of that (the other 5% being reflected). The other half makes it another couple of molecules deeper and then the molecules it warms become more buoyant than their neighbours and rise to the top, losing another half upwards. Now we’re down to ~72W/m^2. Lets remember the net flux is 66W/m^2 upwards at this point. So your ice cube argument fails. The ocean absorbs and re-emits the long wave radiation coming downwards from the atmosphere, the sums balance. In fact it emits 66W/m^2 more long wave radiation than it absorbs. It always has, and the oceans don’t freeze, because solar shortwave warms them to really significant depths of 100 metres and more as internal tides and currents mix its energy downwards. Some of that solar short wave energy is re-emitted as long wave from the surface along with some of the long wave which came from the atmosphere. The rest causes evaporation and thermals or is conducted upwards. The difference is, the solar derived energy can remain deep in the ocean for a long time, controlling it’s bulk temperature.
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, and because the vortices which mix solar energy so efficiently are below the wave troughs, several thousands of times deeper down than the depth DLR penetrates water to. For experimental evidence on this matter I’ve tried putting small soaked pieces of loo paper just under the surface out in the rolling waves away from the shore where they break. They don’t get sucked downwards. So that’s turbulent convection gone, what’s left? Conduction is a non-starter, because water thermally stratifies and anyway is a relatively poor heat conductor unless the heat source is underneath rather than above.
But this isn’t about absolutes. I’m sure the increased DLR warmed the ocean a little bit, or at least slowed its rate of cooling a little bit. I think the increased insolation due to (empirically measured) reduced cloud cover in the tropics 1980-1998 did a lot more to increase ocean heat content. To turn your question back to you, where else could that energy have gone?
Cheers
TB
Merrick says:
August 15, 2011 at 1:39 pm
“And, hate to bring up a long gone painful debate, but if DLR can heat one fluid (water) then it ABSOLUTELY CAN heat another fluid (air) and in EXACTLY the same way. ”
Air is mostly occuring in the gaseous phase.
You would think that the average ninth grade science student could design an experiment to measure what happens when IR hits water in a tank . . . a great Science Fair experiment.
But if a ninth grader could do it, it will be beyond the tall forehead types who walk posts on the IPCC ramparts.
Indeed, the idea that DLR cannot heat the ocean is one of the spurious arguments that should not be used. There are plenty of others. Far too many comments here claim that the Greenhouse Effect cannot be real “because it is not like a real greenhouse”. Or that it contradicts the first or second laws of thermodynamics. Stick to objecting to the infidelities of computer modelling – there is plenty of uncertainty there – the basic physics is much more secure than some people are willing to concede.
The time lag between local apparent noon and max surface temperature is no more than 4 hours. The time constant for the surface heating an cooling rate is VERY short. If every night the surface on the planet cools 2-5 degrees…or more, then what is the big deal about 0.1 degree of warming…notwithstanding the fact that the thermometer sensitivity (globally) is incapable of reporting that level of precision… as Lord Monckton has frequently said.
And I believe that is one of the most misunderstood things about greenhouse warming. Greenhouse warming doesn’t have its maximum impact when the sun is shining, it is at night. When the dominant heat flow is, at night, from Earth to space, the DLR would reduce the rate of cooling and it would moderate low temperatures. Greenhouse warming shouldn’t increase daytime highs, it should increase nighttime lows. Daytime high temperatures will be moderated by things like evaporation and clouds but the nighttime temperatures are moderated only by the blanket that lies between the surface and space.
In the daytime, the same greenhouse gasses also absorb IR from the sun and radiate half of that back into space. Roughly half the energy of solar radiation is IR. Greenhouse gasses act to moderate the amount of IR reaching the surface during the day and moderate the amount leaving the atmosphere during the night.
It is quite possible that one might get with increasing greenhouse efficiency is lower high temperatures and higher low temperatures for a reduction in diurnal range and possibly no change at all in average in the tropics. The greatest impact should be seen at the poles in winter where any enhanced “insulation” should be most easily observed.
Gary wilson says:
August 15, 2011 at 1:13 pm
You are right. To be accurate, DLR means that the surface is warmer than if the DLR weren’t there. So you are technically correct, but in common parlance we don’t usually say “It slows the cooling so it ends up warmer than it would otherwise”. We just say “it warms it”.
Thanks,
w.
Hmmmm,
So far I have to think that Tallbloke gets the cookie! Sigh! It’s not a chocolate chip cookie is it?
One more thing… What idiot proposed that LR does not heat water?
Well, two more things… Somebody give Bystander a penny so he can buy himself a clue. 🙂