Guest Post by Willis Eschenbach
It has been known for some time that the “Pacific Warm Pool”, the area just northeast of Australia, has a maximum temperature. It never gets much warmer than around 30 – 31°C. This has been borne out by the Argo floats. I discussed this in passing in “Jason and the Argo Notes“, and “Argo Notes Part 2“. I’d like to expand on this a bit. Let me be clear that I am by no means the originator of the claim that there is a thermostat regulating the maximum ocean temperature. See among many others the Central Equatorial Pacific Experiment. I am merely looking at the Argo data with this thermostat in mind.
First, Figure 1 shows the distribution of all of the ~ 700,000 surface temperature measurements taken by Argo floats to date.
Figure 1. A “histogram” shows how many data points fall in each of the 1°C intervals shown along the bottom axis. The maximum is in the interval 28°-29°C.
The number of temperature records peaks around 29°C, and drops quickly for temperatures above 30°C. This clearly establishes the existence of the mechanism limiting the oceanic temperatures.
What else can the Argo data tell us about this phenomenon? Quite a bit, as it turns out.
First, a look at the year by year evolution of the limit, and how it affects the temperatures at different latitudes.
Figure 2. Annual temperature variations measured by all northern hemisphere argo floats that exceeded 30°C. Temperature observations are colored by latitude. Click on image for full-sized graphic.
A couple points of interest. First, the cap clearly affects only the warm parts of the year. Close to the equator, that is most of the year. The further from the equator, the less of the annual cycle is affected.
Second, the majority of the breakthroughs through the ~30° ceiling that do occur are from areas further from the equator, and are short-lived. By and large, nobody exceeds the speed limit, especially those along the equator.
Figure 3 is a closeup of the years since 2005. I chose this starting point because prior to that the numbers are still changing due to limited coverage. To show how the mechanism is cropping the tops of the warmer parts of the year, I have added a Gaussian average (129 point width) in dark gray for each two-degree latitudinal band from 0°-2°N up to 10°-12°N.
Figure 3. Annual temperature variations measured by all northern hemisphere argo floats that exceeded 30°C. Dark lines have been added to highlight the average annual swings of the data by latitude band. Click on image for full-sized graphic.
As you can see, the warm parts of the yearly cycle have their high points cropped off flat, with the amount cropped increasing with increasing average temperatures.
Finally, here is the corresponding plot for the southern hemisphere:
Figure 4. Annual temperature variations measured by all southern hemisphere argo floats that exceeded 30°C. Click on image for full-sized graphic.
Note that there is less of the southern ocean that reaches 30°C, and it is restricted to areas closer to the equator.
Next, where are these areas that are affected by the temperature cap? I had always thought from the descriptions I’d read that the limitation on ocean temperature was only visible in the “Pacific Warm Pool” to the northeast of Australia. Figure 5 shows the areas which have at some point been over 30°C.
Figure 5. Locations in the ocean which are recorded at some time as having reached or exceeded 30°C.
Figure 5a. A commenter requested a Pacific-centered view of the data. We are nothing if not a full-service website.
Clearly this mechanism operates in a wider variety of oceans and seas than I had realized, not just in the Pacific Warm Pool.
Finally, here is another way to consider the effect of the temperature maximum. Here are the average annual temperature changes by latitude band. I have chosen to look at the northern hemisphere area from 160 to 180 East and from the Equator to 45°N (upper right of Figure 5, outlined in cyan), as it has areas that do and do not reach the ~ 30° maximum.
Figure 6. Average annual temperature swings by latitude band. Two years (the average year , shown twice) are shown for clarity.
Note that at say 40°N, we see the kind of peaked summer high temperatures that we would expect from a T^4 radiation loss plus a T^2 or more evaporative loss. It’s hard to get something warm, and when the heat is turned down it cools off fast. This is why the summer high temperature comes to a point, while the winter low is rounded.
But as the temperature starts to rise towards the ocean maximum, you can see how that sharp peak visible at 40°N starts first to round over, then to flatten out at the top. Curiously, the effect is visible even when the temperatures are well below the maximum ocean temperature.
Speculations on the mechanism
I want to highlight something very important that is often overlooked in discussions of this thermostatic mechanism. It is regulated by temperature, and not by forcing. It is insensitive to excess incoming radiation, whether from CO2 or from the sun. During the part of the year when the incoming radiation would be enough to increase the temperature over ~ 30°, the temperature simply stops rising at 30°. It is no longer a function of the forcing.
This is very important because of the oft-repeated AGW claim that surface temperature is a linear function of forcing, and that when forcing increases (say from CO2) the temperature also has to increase. The ocean proves that this is not true. There is a hard limit on ocean temperature that just doesn’t get exceeded no matter how much the sun shines.
As to the mechanism, to me that is a simple question of the crossing lines. As temperature rises, clouds and thunderstorms increase. This cuts down the incoming energy, as well as cooling the surface in a variety of ways. Next, this same process moves an increasing amount of excess energy polewards. In addition, as temperature rises, parasitic losses (latent and sensible energy transfers from the surface to the atmosphere) also go up.
So … as the amount of total radiation (solar + greenhouse) that is warming any location rises, more and more of the incoming solar radiation is reflected, there are more and more parasitic losses, more cold water and air move from aloft to the surface as cold wind and rain, and a greater and greater percentage of the incoming energy is simply exported out of the area. At some point, those curves have to cross. At some point, losses have to match gains.
When they do cross, all extra incoming energy above that point is simply transferred to the upper atmosphere and thence to the poles. About 30°C is where the curves cross, it is as hot as this particular natural system can get, given the physics of wind, water, and wave.
I make no overarching claims for this mechanism. It is just one more part of the many interlocking threshold-based thermostatic mechanisms that operate at all temporal and spatial scales, from minutes to millennia and kilometres to planet-wide. The mechanisms include things like the decadal oscillations (PDO, AMO, etc), the several-year Nino/Nina swings, the seasonally opposing effects of clouds (warming the winters and cooling the summers), and the hourly changes in clouds and thunderstorms.
All of these work together to maintain the earth within a fairly narrow temperature band, with a temperature drift on the order of ± 0.2% per century. It is the stability of the earth’s climate system which is impressive, not the slight rise over the last century. Until we understand the reasons for the amazing planetary temperature stability, we have no hope of understanding the slight variations in that stability.
My regards to you all,
w.
UPDATE (by Anthony):
Dr. Roger Pielke Sr. has some praise for this essay here:
steven mosher says:
February 13, 2012 at 10:19 am
Thanks, Steven. I was shocked to the core when Anthony published the N&Z nonsense without a strong disclaimer at the top. I didn’t comment on it. Not once. It turned my stomach. I fervently hoped it would die a natural death and be swallowed in silence like so many of my posts. No such luck.
Instead, it’s like an infestation of bedbugs, there’s gravity-heads and pressure-heads crawling out of the woodwork to see who can do the best job of hand-waving. They’ll say something they are convinced clearly explains a scientific concept, along the lines of “The Ideal Gas laws make it so that pressure causes the temperature to be more like it is now than it was when I got here”, and wait for the applause, and wonder why I laugh and point instead of picking up on the revealed wisdom.
I simply plan to continue letting them know they are not welcome to expound their nonsense on my threads. I’m happy to talk real science with anyone, but not drivel. And sure, they’re free to expose their unappreciated idiocy to an uncaring universe, but I’m not happy to see them do it here at WUWT, and I will continue to let them know it. Tallbloke’s Talkshop has appointed itself the center of gravity and pressure, I invite Steven Wilde and others to go there. Here, I’m not buying their nonsense, and I won’t until the Laws of Thermodynamics are overthrown. Might happen someday, but until then …
w.
http://en.wikipedia.org/wiki/Lapse_rate
“the concept can be extended to any gravitationally supported ball of gas.”
“Because the atmosphere is warmed by conduction from Earth’s surface, this lapse or reduction in temperature is normal with increasing distance from the conductive source.”
“I suspect, for example, that rocks have a hard time overcoming downward pressure.”
So you didn’t know that rocks are heavier than air ? Unlike water vapour ?
“I simply plan to continue letting them know they are not welcome to expound their nonsense on my threads.”
The threads ‘belong’ to Anthony and through Anthony the contributors. You come last.
Stephen Wilde says:
February 13, 2012 at 10:25 am
Stephen, I truly don’t care in the slightest about your pressure theories. I have no use for them. You yourself seem to be no more able to explain them than N&Z were able to explain Equation 8. I have said many times that fantastic theories that violate basic scientific principles are not welcome here. I have invited you to take them to tallblokes.
What part of “go away” are you missing? This is a post on Argo, not on your dang cockamamie pressure theories. If you want to discuss them, I’m sure you can find lots of folks at tallblokes to talk them over with. Plus they won’t call you an idiot for believing impossible things, and I definitely will. Plus they understand the nuances that I don’t care about. Heck, Roger might even let you post on your brilliant ideas there.
w.
No more discussion of N&Z theory here. All subsequent off-topic posts will be deleted.
Anthony
The Pompous Git says:
February 13, 2012 at 10:26 am
The Principle of Charity doesn’t extend to people trying to trash my reputation and damage my credibility with false allegations.
Maybe you sit still and smile when someone does that to you, Pompous.
I don’t.
w.
“No more discussion of N&Z theory here”
Ok. But what about lapse rate and the Gas Laws ?
They predate N & Z by a long way and are directly relevant to convection at the ocean surface and consequent sea surface temperatures.
Willis Eschenbach says:
February 12, 2012 at 9:30 am
“I have seen this statement several times on these pages. Can someone explain to me why surface tension should totally inhibit heat transfer from gas to liquid?
This is part of a wider misunderstanding, which claims that for various reasons the ocean can’t be heated by infrared … I just ignore them, and advise others to do the same. For some reason, the idea that infrared (thermal) radiation can heat anything but water has taken hold with these folks, and there is nothing that will convince them otherwise.
Ignore them.
w.
[edited to add: See my post, “Radiating the Ocean”, where many examples of R.M.B.’s kind of foolishness are on display … w.]”
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Willis I would say that your explanation as to how longwave infrared heating water just like rock ignores specific properties of water. I find Michael’s explanation closer to reality to what happens at the surface of water in case of longwave infrared heating:
http://wattsupwiththat.com/2012/02/12/argo-and-the-ocean-temperature-maximum/#comment-890843
michael hart says:
February 12, 2012 at 8:51 am
______________
Tim,
Simply put, the main reason is that at very short distances from the surface [approx micrometres and less] the forces that produce bulk mixing in the ocean become much less important, and diffusion becomes dominant. This diffusion constraint affects how fast heat can be transferred DOWN from the surface [the “Einstein-Smoluchowski” limit is often how it is taught in Chemistry, where it has an important effect on reaction rates]. You cannot make it go faster by simply stirring with wind/wave/convection. So when the heat cannot be rapidly transferred downwards, then more water evaporates, effectively transferring the heat UPWARDS [as latent heat]. This heat now CAN be transported efficiently by wind and convection. It will later reappear when it condenses back to water somewhere else on the planet, higher in the atmosphere, closer to the poles, etc.
Now, Infra red radiation is so strongly absorbed by the top micrometres within this surface zone limited by diffusion rates, that a resulting temperature rise [from increased IR radiation] is more easily lost by evaporation than it is transferred to depths. Dave Springer has often posted about this on these blogs, and elsewhere. It has been used to argue than “Trenberth’s missing heat” in the oceans never did enter the oceans.
————————————-
So longwave infrared may be warming the water but in limited ways controlled by diffusion and evaporation.
I personally find backradiation does heat anything, but reduces heat loss of the surface which is a different thing even if at first view might look as if having the same effect. In case the oceans are warmer then the air, if, lets say, water radiates 350 W/m2 and the radiation from atmosphere is 250 W/m2 it does not mean that the ocean gets 250 W/m2 extra heat, but the surface of the ocean is having a radiative loss of 350-250=100 W/m2. It is still a loss but smaller. The rest of the heat coming from sun is lost through evaporation.
One may argue that reducing heat loss (like isolation, like a carpet) has the same effect as adding heat, but I find that giving “backradiation” a value as if it were a heat source is what is creating confusion and wrong calculations.
———————————————————
Willis Eschenbach says:
February 13, 2012 at 9:14 am
The proof is in the fact that the ocean receives about 170 W/m2 from the sun, radiates away energy at about 390 W/m2, and loses about 100 W/m2 via evaporation and conduction/convection.
1) The ocean is frozen there where there is no radiation from the sun – between 15 and 20 million sq km. It does not radiate there – this reduces the energy the oceans radiates away with some 390*17.5 TWatt
2) In summer ice melts and most incoming radiation enters the ocean when under sun radiation, the 170 W/m2 is calculated considering also the area covered by ice – so for incomming radiation one has to add the area that melts. Also the part still covered by ice is receiving less radiation in average then the rest, so the average of the ocean under sun has a higher Watt value.
Back to the Argo question. As I said above, I don’t know the details of the mechanism. For me, it’s a simple example of where the lines cross. When the losses equal the gains the heating stops. How hard a stop that is, depends on the slope of the lines when they cross. From the fact that almost no Argo temperatures anywhere exceed 31°, I have to assume that at that point losses are climbing quite sharply.
This is in line with several things.
1. The rapid rise of evaporation with temperature. Saturation vapor pressure goes up exponentially with temperature.
2. The rapid rise of evaporation with wind, particularly thunderstorm winds. Evaporation goes up lineally with wind speed, so an increase from one m/sec to 10 m/sec (2 to 22 mph) increases evaporation by a factor of 10.
3. The T^4 dependence of radiation on temperature. As temperature rises, radiation rises much faster.
4. The rise of conduction/convection with increased wind. The sensible heat flux also varies linearly with wind speed.
5. The threshold-based nature of cloud and thunderstorm formation gives very steep rises in albedo, vertical convection, wind, downwards transport of cold rain and wind, and other surface-cooling mechanisms.
So we have evaporation (rising linearly with wind and exponentially with temperature), radiation (climbing as temperature^4), sensible heat loss through conduction/convection (rising linearly with wind and surface/air temperature difference), and a host of surface-cooling mechanisms (cloud albedo increase, surface albedo increase, cold rain and wind from aloft, etc) which rise linearly with thunderstoms. At some point that is enough to overwhelm the power of the sun plus the greenhouse effect.
Bear in mind that the combined downwelling radiation (greenhouse plus solar) in the tropics on a 24/7/365 basis is around 670 W/m2 … so it is clear that there is plenty of radiation to push the surface temperature higher. The blackbody radiation of 31°C is 485 W/m2. So it is not lack of energy that is keeping the ocean from warming further.
Now, I make no claim that that is an exhaustive list of ways that the temperature maximum is maintained. I suspect that there are subtle changes in clouds along the lines of those postulated by Lindzen. The effects of the El Nino are a possible factor.
My point is simple. At some temperature, all of the incoming energy is lost to a combination of the factors listed above. And when the sun gets hotter than that, any excess energy is shipped to the poles. There is no further temperature rise.
Finally, in the tropics, a doubling of CO2 represents a change in total forcing of less than one percent … anyone who thinks that a half-percent change will not be swallowed up by a host of compensatory mechanisms underestimates Murphy.
w.
“And when the sun gets hotter than that, any excess energy is shipped to the poles. There is no further temperature rise.”
I would say that when the WATER gets hotter than that any excess energy is shipped to the poles but:
When the SUN gets hotter then the maximum water temperature would rise.
The difference being that in the first case there is no more energy being added to the system but in the second case more energy is available at the water surface to be redistributed which will force a higher equilibrium temperature at the ocean surface.
It then follows that because GHGs do not add any extra energy to the system they would not raise the maximum sea surface temperature either. Instead there would just be a faster redistribution as the energy from the GHGs is shifted faster through the system and out to space.
The rest of that description as to how the maximum sea surface temperature might be maintained looks good to me.
However we still differ as to WHY all those mechanisms ramp up so much at the point that they do. If you have an alternative suggestion to atmospheric pressure I would be interested to hear it.
How could you say this:
“I have to assume that at that point losses are climbing quite sharply.”
without taking another step and seeing that at that point the turbulence caused by the energy at the surface rapidly overcomes the restraining influence of the weight of the atmosphere ?
Willis: Finally, in the tropics, a doubling of CO2 represents a change in total forcing of less than one percent … anyone who thinks that a half-percent change will not be swallowed up by a host of compensatory mechanisms underestimates Murphy.
what do you think of the simulations performed on Isaac Held’s blog?
http://www.gfdl.noaa.gov/blog/isaac-held/2011/10/26/19-radiative-convective-equilibrium/
It looks to me now that this is the approach that best quantifies what you wrote, and that with faster computers they will be able to model the effect of doubling the CO2.
Willis,I noted with some surprise that you responded to Richard Verneys response to my comment, yet ignored the original. In case you missed it I am reposting it for your consideration.
Original post –
Willis,
I enjoyed the post and I believe you are correct in suggesting a limit to ocean temperatures. But then I noted in your reply to Stephen Wilde that you again asserted DWLWIR has the same effect over the oceans as it does over land. I would again ask you to consider that you are in error on this point. After your post on “radiating the oceans” I conducted several experiments looking at this issue. I found that Stephen Wilde is correct and that liquid water that can evaporatively cool does not have its cooling rate effected by incident LWIR in the same manner as other materials. Subsequent to that as reported here at WUWT, Schmittner et al 2011 was published indicating that the effects of increasing CO2 may be “multi-modal” ie: different over the oceans.
I urge you to take the time to conduct you own empirical experiments into this issue. You can use microwave safe cling wrap to restrict evaporative cooling of warm water samples without greatly altering conductive and radiative cooling. Thin film LDPE is largely IR transparent at the relevant frequencies. In urging you to design and conduct your own physical experiments I would remind you that Anthony Watts, the host of this site, started out on his journey with empirical experiments into the effect of changes in white wash to latex paint on Stephenson screens.
It seems Willis is unassailable. You can’t put words in his mouth, you can’t draw him outside his comfort zone, you can’t question the data accuracy since he rounded out to 1 Celcius degree. His histogram is patently an accurate representation and shows something odd happenning at around 30 Centigrade. If you accuse him of being stupid you discover he is more intelligent than you are, if you accuse him of being wrong you had better keep well within your comfort zone.
Willis is on a roll and, I suspect, having fun. As a mere mortal I can only stand back, wide eyed and wondering at a thoroughly entertaining show. Please continue.
Richard M: Does anyone else note that Willis is taking pretty much an opposite position as he did with N&Z? Now, admittedly N&Z took their observations too far. And, I think Willis was correct in attacking some of their suppositions. However, when some of us noted that there may be some interesting observations that should be pursued, Willis had no interest.
I don’t see that at all. If you think that is true, you should support it with actual quotes.
Stephen Wilde: Surface air pressure determines the amount of heat (or rather energy) flow that one gets from a given temperature differential.
The higher the pressure at the surface the higher the temperature needs to get at the surface to enable convection to overcome the weight of air pressing down on the surface.
Increased pressure leads to increased density. Does not the increase in density also increase the rate of diffusion of heat?
Willis,
Even if it is true that the water can’t heat much above 30C, an increase in forcing caused by an increase in CO2 could cause an increase in the global mean temperature by (a) increasing the total area that is at or near the peak or (b) increasing the duration of time that the peak temperature is sustained, or both. So this analysis does not relate directly to any kind of thermostat hypothesis; something else such as increased cloud cover must constitute the thermostat.
What do you think?
Willis Eschenbach says:
February 13, 2012 at 10:06 am
No quotations or evidence needed when you attack a man?
Richard, it’s surprising. Previously, you hadn’t struck me as the kind of sleazy skank who would attack a man’s character, and then when asked for evidence to back up his nasty allegations, would say that no evidence was needed. Don’t know why, but I had a different impression, you seemed like kind of a decent honest guy.
Willis, there was no intent on attacking you and I don’t believe I did. I’m sorry if you took it in that vein. I was simply pointing out you had taken different positions on two issues that appeared to conflict to some degree. I did this because I believe you are correct here in trying learn something from observations before discounting them (as some of the commenters have done). But, you really did discount the similarities of the planets without a lot of consideration (at least that is how it appeared to me). I still believe there may be some structural aspects of an atmosphere that put constraints on the GHE. It appeared to me you were dismissing these observations because of the contrived physical mechanism specified. Did I misinterpret your stance? Correct me if I am wrong.
However, it’s good to see that you are open to observational evidence without the need for a physical explanation. I also think that is important.
Back to the topic at hand. I think the 30° limit does raise a lot of questions relative to water vapor feedback. Clearly, it doesn’t eliminate it as there are still massive ocean areas that could warm substantially before reaching 30°. However, I would guess the tropics are biggest source of water vapor and I suspect the models don’t limit the amount that could be produced there. So, this raises questions with the models that I’m sure some with a more intimate knowledge of their internals will want to investigate. Who knows, maybe they already factor this into the GCMs. But, it’s worth understanding.
“Increased pressure leads to increased density. Does not the increase in density also increase the rate of diffusion of heat?”
Yes indeed but only amongst the denser gases where it lingers longer than if the density were less.
The greater the density the more molecular collisions and the longer it takes the energy to escape.
Septic Matthew says:
February 13, 2012 at 12:53 pm
Richard M: Does anyone else note that Willis is taking pretty much an opposite position as he did with N&Z? Now, admittedly N&Z took their observations too far. And, I think Willis was correct in attacking some of their suppositions. However, when some of us noted that there may be some interesting observations that should be pursued, Willis had no interest.
I don’t see that at all. If you think that is true, you should support it with actual quotes.
Willis wrote an entire article dismissing equation 8 and the table that applies the equation … the table is essentially an observation. Did you miss it? Do I really need quote something that obvious?
“an increase in CO2 could cause an increase in the global mean temperature by (a) increasing the total area that is at or near the peak or (b) increasing the duration of time that the peak temperature is sustained, or both”
Not if the ramping up of the non radiative processes amounts to a faster ejection of energy to space.
GHGs do not add new energy to the system the way a stronger sun would, They just slow down the rate at which it passes through (though there is some debate about that given that they also radiate out to space more effectively than non GHGs) so if something else speeds it up again the net effect would be zero but there would be a small adjustment in the surface pressure distribution. In the example of the ITCZ there would simply be lower pressure under the energised ITCZ and slightly higher pressure either side where the air descends again.
My own view however is that GHGs probably have a net zero effect anyway.
The Pompous Git says:
Michael Faraday’s motor doesn’t appear to fit in at all well with Popper’s prescription:
I’ll state categorically that one can not build anything without a theory of how it will perform or function. Faraday may not have had a theory consistent with the accepted body of science in his time, but he assuredly had a theory of some kind, possibly resulting from some serendipitous discovery of his.
Although your use of ‘theory’ may well be narrower than mine.
You know you have interesting data when it causes an argument 😉
The story so far:
Willis took Argo data and turned it into pretty pictures.
We look at pretty pictures and go, “Hmm. The temperature seems to “cap off”, or hit a limit, at the 30 deg C mark. WUWT?”
People begin listing hypotheses, including convection, currents, evaporation/hydrologic cycle, clouds, air pressure, etc…
People argue about their ideas.
How about we come up with something testable and run an experiment?
Me, I can’t get past the number 30. Sure, as some have pointed out, as in every statistical data set, there are outliers, perhaps a statistically significant amount of them. That doesn’t change the fact that this limit is observed for the other 99.9%, and I am equally interested in why most of the ocean can’t break the 30 barrier and why some of it does.
Is it simply a mathematical product of energy in (sun +?) versus energy out (above hypothesis?), and 30 degrees C is the magic number that makes it balance (99.9% of the time)? At least it is a real number, and not something we plugged into a model to make the picture turn out the way we wanted.
Goooo (civil) debate!
Stephen Wilde: Not if the ramping up of the non radiative processes amounts to a faster ejection of energy to space.
That may happen, as I think I have written in comments. However, disputing a “could” with another “might” or “maybe” emphasizes the unknowns.
Richard M. : Do I really need quote something that obvious?
I thought that you were wrong. If you made an actual case with actual quotes to point out the inconsistency that you claimed, then I might see how you were right. As it stands, you are either wrong or empty.