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:
Joules Verne says:
February 12, 2012 at 8:31 am
No, it didn’t occur to me, because it is absolute nonsense. The equivalent blackbody radiation for 30°C is about 480 W/m2. The TAO data shows that the average downwelling radiation 24/7/365 at the equator is about 670 W/m2. So as usual, your claim is rubbish, not just slightly wrong but cataclysmically and stupendously wrong. And also as usual, everything coming out of your electronic pen is worse than useless, it is actively misleading.
Joules, your content-free rantings are as welcome here as those of Stephen Wilde. You have proven repeatedly that your grasp of science is abysmal. Please go to tallblokes and bother him, here we’re discussing scientific topics.
w.
High sea water temperature, memories from time spent in the Canadian Navy working in the boiler and engine room of a destroyer pulling into Manzanillo Mexico water temperature reading well into the 80’s, 30c=86f. Got just a little warmer than normal,sarc, in those work spaces. If there is a hell, been there done that. Any other stokers out there?
Maybe I misunderstood the data set.
Are these graphs only of Argo units that at some point in their lifecycle reported a temperature >30°C?
“Annual temperature variations measured by all northern hemisphere argo floats that exceeded 30°C. “
Ever heard of a thermal low?Like in southern California when the deserts heat up it creates low clouds and fog in the coastal areas(fogaggedon).Heat rises and and causes low pressure near the surface.Maybe that process(heat rising) also drives ocean temps and currents?What about salt water’s lower freezing point and lower boiling point? Shouldnt that also make it’s evaporation point lower ?Maybe a little off topic,but that what i thought about when i read the article and comments.
Mike M says:
February 12, 2012 at 9:33 am
Guys, I pointed out above where the data to test your ideas resides, it’s at KNMI. I took a look at some model runs. The average of the CMIP5 runs gives about 29°C for the temperature of the gridbox at 0-10°N, 160-180E. This agrees well with Argo data, as well as other observational datasets (HadSST, Reynolds).
So if you say the result DOES falsify their models, then show us what you are basing this claim on. I couldn’t find any support for your claim when I looked at some model data yesterday, but perhaps you can.
Look, fantasizing about how this will affect the models is meaningless. Do your homework, run the numbers, and then you can take a stand.
My guess is that overall they do a reasonable job replicating the 30°C limit, with some doing better than others. But this is not the problem, or even the symptom of the problem, with the models. That’s a whole other topic.
w.
This is a rather nice recourse for the thermodynamic properties of sea water.
http://web.mit.edu/lienhard/www/Thermophysical_properties_of_seawater-DWT-16-354-2010.pdf
One thing you are all missing is wind 30 knots will mix down to about 30 ft. At 7.5 knots white caps occure which uis of course is mixing
What is the theoretical maximum sea surface temperature, given the make-up of our atmosphere and other contributing factors? How far above 30C is it?
Willis Eschenbach says:
February 12, 2012 at 9:45 am
richard verney says:
February 12, 2012 at 6:38 am
“Nonsense. Yours is the trap that the AGW folks have fallen into, of hypothesizing in advance of the data.”
///////////////////////////////////////////////////////
Willis
Please
1. set out with full particularity the trap that you allege that I have fallen into; and.
2.identify with precision the comment and if there be more than one comment the comments that I have made that evidence that I have fallen into the trap that you assert that I have succumbed to.
Silence from you in response to my rewuest will be taken that you are unable to identify one or more of the above such that your assertions are baseless.
I look forward to hearing from you so that I may consider the serious merits of your serious allegation
The temperature is set by the atmosphere.
Less atmosphere means lower air-pressure which means lower vapour pressures which means evaporations starts at a lower temperature.
Bigger atmosphere means higher air-pressure which means higher vapour pressure which means evaporation starts at a higher temp.
Brilliant. I am amazed by what we are seeing.
Dennis Ray Wingo said:
“Another possibility that caps the heat is that some of this energy is transferred to cooler deeper regions of the ocean, which at the end of the day results in a longer term form of regulation but I was slightly surprised that you did not mention it”
________
We know if fact this happens on both a short-term and longer-term basis, depending on how deep the energy is transferred. Right now, for example, there is large subsurface mass of warmer than average (much warmer in some cases) water in the western equatorial Pacific that has been slowly growing and expanding to the east under the surface during the course of the current La Nina. This recharge activity of the Pacific Warm Pool subsurface water is not atypical of the ENSO cycle, and certainly plays a role in the regulation of surface temperatures as some of the warmth from the surface waters has gone down in to the deeper ocean, not up into the atmosphere. Some of the deeper ocean energy will find its way back to the surface to be released dring the next El Nino.
Willis , you have a knack for stating the obvious , and I mean that as a compliment because apparently so few people recognise the obvious until it is pointed out to them, myself included. You take things that appear to be obscure and interpret them in such a manner as to make them obvious. Thanks for what you do. You have ability as a teacher, you reach people with your thoughts.
Willis Eschenbach says:
February 12, 2012 at 9:57 am
Steve from Rockwood says:
February 12, 2012 at 8:11 am
“Steve, every year the energy from the sun increases and decreases. Given the sun’s intensity, for part of the year there is plenty of energy from the sun to make many ocean areas reach over 30°C … but they are not getting that warm”
///////////////////////////////////////////////////////
Willis
You may recall that for several years we have been arguing as to whether without DWLWIR, the tropical oceans would freeze. Your position is that the tropical oceans would freeze. I have suggested to you that you are misguided in that you are looking only at average conditions and failing to focus on the conditions that prevail in the equatorial regions and when one focuses on those specific conditions, even without the effects of CO2 DWLWIR,, the tropical ocean would not freeze because there is enough solar in those regions to keep the tropical ocean warm.
I take it from your comment to Steve that “..there is plenty of energy from the sun to make many ocean areas reach over 30°C…” you will now appreciate that your previously expressed view that the tropical oceans would freeze is very probably misconceived.
Willis: Thanks for this very interesting presentation. It basically shows that the Sun, all 1370 w/m**2 of it, heats the ocean. The latitude band encompassing the Tropic of Cancer (and presumably, the same for the southern hemisphere) merges into the maximum temperature band. All more northerly bands step down to lower average temperatures, as they receive correspondingly less energy the further from the equator. I would guess that the spacing of those bands is geometrically related to their latitudinal position.
In essence, the full sun (not some “sun/4”) is the heater of the ocean, which then acts to dissipate that heat by flowing, mixing and evaporating. Received LWIR has nothing to do with the ocean’s temperature (or heat content), except that it may heat air in contact with the ocean (if it does anything at all).
I have seen a “thermostat effect” in “determined” global temperature over the past half billion years or so. When CO2 was at 1200 PPMV and there were no major land masses at the poles, global temperature was generally 22 C. With CO2 at 6000 PPMV, global temperature was 22 C. When CO2 was high and there was a major burpout of methane, global temperature hit 23 C. I suspect the reason is that increase of GHGs increases the lapse rate, and the lapse rate feedback (which is negative). Greater lapse rate increases convection.
Also, according to “determinations” of the past, 23 C occurred less than 100 million years ago and 6,000 PPMV CO2 achieving a limit of 22 C occurred over 300 million years ago, and it is theorized that the sun is slightly increasing its output as it ages.
As for the 30 C limit of tropical waters: It appears to me that exceeding 30 C is causing convection that transfers heat to cooler parts of the world. Keep in mind that the equatorial tropopause is so cold (due to convection to such high altitude) that significant net loss of heat from radiation appears very unlikely to me. So, I think the heat going there mostly moves onward to less tropical parts of the world before it gets radiated to space.
In any case, I would expect the tropical ocean temperature limit to vary with the amount of sunlight directed towards Earth, roughly by the 4th root rule. Since solar output directed towards Earth peaked at about 1366.6 W/m^2 in the 1980’s maximum and even an aggressive prediction for a few decades from now calls for a Maunder-like dip around 1359.5 W/m^2, solar output is unlikely to vary by much more than 1/2 of a percent. This means solar variation is unlikely to cause the tropical ocean temperature limit to vary by much more than 1/8 of a percent or about .4 degree K, even with this extreme range of solar variation.
I do agree with a concept of increase of GHGs causing very little increase in the tropical ocean temperature limit. It appears to me that increase of GHGs warming convection-prone equatorial ocean areas requires albedo change (4th root law applies), or increase of the effective altitude of the level of the atmosphere where GHGs radiate directly to space (and I see the effect there being small).
GCM forecasts calling for increase in tropical middle and upper troposphere temperature appear to me to include excessive cloud albedo positive feedback. I am expecting the cloud albedo feedback to be positive, as convective clouds increase their efficiency with increased water vapor content and increased lapse rate. However, I expect the cloud albedo feedback to be only a fraction as positive as IPCC did as of AR4.
Also, I see positive cloud albedo feedback due to increased efficiency of convective clouds being accompanied by decrease in troposphere relative humidity, as more vigorous updrafts cover a smaller percentage of the world and downdrafts occupy a larger percentage. So, I see any positivity in cloud albedo feedback reducing the water vapor positive feedback. I think these explain why the tropical middle and upper troposphere is lacking the predicted hotspot.
“Until we understand the reasons for the amazing planetary temperature stability…”
Odd. Rumor had it that the UN War on Climate Change was the only possible mechanism for this…
Jim F said:
“In essence, the full sun (not some “sun/4″) is the heater of the ocean, which then acts to dissipate that heat by flowing, mixing and evaporating. Received LWIR has nothing to do with the ocean’s temperature (or heat content), except that it may heat air in contact with the ocean (if it does anything at all).”
_____
You, and others with similar notions are really looking at this quite incorrectly. It is not a question of what heats the ocean or more accurately, transfers energy into the ocean. Certainly the sun is the source of the majority of the energy in the ocean through the deeper and stronger penetration of SW radiation. But the question really is: “Why is the ocean not losing as much energy back to the atmosphere as it is taking up?” In this regard, you need to look at the complete ocean in all layers, and in doing so, of course you’ll find that the ocean heat content has been going up over the past 30+ years, and this is even more strongly indicated the deeper you take the metric.
Willis’s analysis of the surface temperatures indicates the mechanism whereby a limit is set on the surface temperature of the ocean, and in this regard, is a clue as to why the ocean overall is gaining energy. Sea surface temperatures are a measurement of energy being givien off to the atmospshere. This energy exchange we measure as heat. If there is a cap on the amount of “heat” at the ocean surface it means there is a cap on how rapidly the energy can flow from the ocean to the atmosphere. No doubt determined by atmospheric temperature and pressure. As the overall ocean heat content is rising, it means energy is entering in a larger amount than is leaving, as its exit is capped at a certain rate, as Willis has demonstrated.
There is a small sea area where temperatures exceeding 30 C are common. This is the Red Sea. It is disconnected enough from the global ocean to have less oceanic convection with cooler ocean areas than other tropical sea areas. Also, it is just a little too small to be favorable to formation of tropical cyclones. The southern part has *average* summertime surface temperature of 30 C.
Its high salinity, due to being in a hot and arid part of the world, accounts for only a fraction of a degree C higher temperature than other sea waters for a given amount of evaporative cooling.
richard verney says:
February 12, 2012 at 10:39 am
Glad to. You said:
This is what the AGW folks did. First they came up with the hypothesis that CO2 causes warming. Then they went out to look at the data. You are doing the same thing, insisting that I come up with a hypothesis before looking at the data. I much prefer not to do that, it warps my thinking if I already have a hypothesis in mind when looking at data I’ve never seen before.
So I am under no obligation to put forward a hypothesis of any kind, Richard. I have only offered a few comments about causation. Mostly, I’m just looking at the data. Call me crazy, but I like to have a very good handle on the reality under discussion before I start coming up with hypotheses to explain it. Goofy, huh? And that’s the trap you’ve fallen into when you insist that I hypothesize in advance of the data.
Jeez, what do you think this is, the Spanish Inquisition? You are not a lawyer, and I am not on the witness stand. I am under no obligation to answer you at all, you can’t put me on the rack and force answers out of me, and if I grow silent, my silence may only indicate that your incessant nitpicking and bitching about irrelevant details in a three-page screed has finally gotten to me.
Richard, I’m not laying out the theoretical underpinnings of a scientific revolution here. I am simply examining some data with an open mind. You should try it, you might like it, and guess what?
I don’t have to come up with a “physical hypothesis which can be tested” of any kind. I’m just investigating the data, and you don’t make the rules.
w.
PS—I finally remembered the apposite quote that has been at the edge of my brain while I’ve been writing this, which comes from Sherlock Holmes.
That was the IPCC method, and the method you advised me to follow as well when you say “First, it is necessary to put forward a physical hypothesis …”.
No, it is not necessary to theorize before one has data, it is a mistake to do so. It is what I described as being the “trap that the AGW folks have fallen into, of hypothesizing in advance of the data.”
richard verney says:
February 12, 2012 at 11:02 am
Richard, truly, I haven’t a clue what you think Steve said, or what you think I said, that has to do with whatever it is that you are talking about. That was the most opaque writing I’ve seen in a while. Clearly you think you’ve scored some massive point in the discussion, but I’m sorry, I simply can’t make heads or tails of it.
w.
Willis I know you didn’t mean to imply that those were my words, but simply a formatting error in a busy day.
I cannot speak for anyone else, but the point, I thought, I did make was:
I am not aware of any component of current models, which would limit SSTs. If there is, in fact, a mechanism which can limit T, then the underlining hypothesis is missing a key function and thereby false. Until this function is understood, validly integrated into the model, it remains falsified… If there is indeed a “cap”. The only thing you quoted from me was: This in itself would seem to falsify models. It is why I also used the word “urgent” as in high priority.
Hope that clarifies things. Cheers. GK
What this demonstrates is the known issue of the lower to mid troposphere warming and the upper troposphere/lower stratosphere not warming. What drives thunderstorms is the temperature differential between the upper troposphere/lower stratosphere and the surface.
Once the differential is high enough any instability (hot spot) at the surface that causes upward air movement kicks off a thunderstorm transferring energy to the upper atmosphere. The differential guarantees that the rising air will pass through the dew point and start isothermal expansion (since the water vapor partial pressure is dependent on temperature and exceeding the partial pressure triggers condensation).
The lack of warming higher in the atmosphere limits how warm the lower atmosphere can get.
mbur says:
February 12, 2012 at 10:19 am
Ever heard of a thermal low?Like in southern California when the deserts heat up it creates low clouds and fog in the coastal areas(fogaggedon).
I’m not sure, but you seem to mean advection fog:
http://apollo.lsc.vsc.edu/classes/met130/notes/chapter5/advect_fog1.html
and with photo (same site):
http://apollo.lsc.vsc.edu/classes/met130/notes/chapter5/advect_fog4.html
Seems more a result, rather than a cause, of ocean temps and currents.
I call BS. From the data shown in Figures 2, 3, and 4, there are multiple data points with values greater than 30 degrees C. There are data points approaching 35 degrees C.
As some great scientists noted, only one exception is required to disprove a theory. Here, there are many dozens perhaps hundreds of exceptions to the “30 degrees C maximum.”.
I suspect, but do not know with certainty, that wind across the ocean surface plays a key role in sea surface temperature regulation.
As others above also noted, the Argo data does not include shallow areas of the ocean. I suspect that those areas are also greater than 30 degrees C. If I recall correctly, the movie Endless Summer had the stars surfing off the coast of Ghana in water that was very hot, so hot the wax melted off the surfboards.
Interesting.
You have regions that are sparsely sampled. You find a temperature cap in those regions.
would you say that the unobserved locations in these regions are best estimated by
A. the cap temperature
B. a number higher than the cap
C. a number lower than the cap.
Seems like the existence of a cap argues for a more spatially coherent temperature structure
than some would like to admit. And the more coherent the temperature is spatially, the fewer
samples one needs to characterize it.