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:
Chris Colose says:
February 12, 2012 at 11:16 pm “…There will be a SkepticalScience piece published about this article any day now (written by me),,,” Oh, great. I just hope you write it in English. I’m looking forward particularly to the discussion of “…clouds as thermostats in the modern climate, since the shortwave albedo component nearly cancels the longwave greenhouse component at the top of the atmosphere (in the tropics). The details on how this cancellation plays out in a global warming scenario cuts into the heart of the climate sensitivity issue, which I didn’t really get into, but there is no compelling basis to suggest that clouds inherently buffer SST changes in a forced climate….”
Use lots of pictures, we’re pretty slow here.
Geoff Sherrington says:
February 12, 2012 at 11:33 pm
Geoff, I’m not sure why you think there is “heat coming in from below” in any significant amount.
For example, in the tropics the 24/7/365 average downwelling radiation (solar plus greenhouse) is about 670 W/m2.
The heating from below is on the order of only a tenth of a W/m2. Additionally, there is absolutely no reason to assume that it “is an accumulator”. Heat rises, so it can only accumulate at the top of the ocean, never the bottom.
A constant heating of 0.1 W/m2 will lead to a vertical (and extremely slow) heat flux of 0.1 W/m2 through the ocean, and finally to a corresponding 0.1 W/m2 increase in average ocean surface heat loss … in other words, a very slow heat flow that is not noticeably anywhere.
As to why the deep ocean is cold, that is a consequence of the giant heat engine we call the climate. It has two working fluids, air and water. The system transfers excess heat from the hot end of the heat engine (tropics) to the cold end (poles). At the poles, both the air and water lose their heat to outer space. Because air and water are denser when they are cold, both of them sink down to the bottom of their respective domains, and there they flow back towards the equator.
As a result, the deep ocean is constantly being replenished with very cold water sinking at the poles and over hundreds of years slowly circulating back to rise up at the equator and start the cycle over again.
w.
FYI, I’ve made a comment on the following solar max, SST thread that links back to here, referencing a paper that found the hydrological cycle intensifies at solar maximum, presumably in response to increased solar irradiance.
“It appears the tropics – exactly the area where the maps and floats show having the highest SSTs – are relatively low-pressure regions. They are bounded by higher pressure zones north and south. Are you saying that this contributes to the tropical seas weighing in at around 30˚C, rather than 35˚C?”
It is global average pressure that counts.
Regional pressure just reconfigures to ensure that the Adiabatic Lapse Rate is maintained as closely as possible.
The Tropics are bound to be lower pressure on a regional basis because that is where the ocean surface gets hot enough for convection to overcome the weight of the atmosphere pressing down onto the surface and rising air is associated with lower pressure.
The higher pressure either side is simply where the Tropical rising air then descends.
To get the maximum sea surface temperature persistently higher than we currently observe (and yes,there are areas hotter than 30C from time to time) we have to have an increased atmospheric mass or higher solar input to the entire Earth system. Any other variable such as more GHGs just results in an energy redistribution but no change to total system energy content.
Such a redistribution does have a climate consequence but that from the human contribution would be miniscule compared to natural variability.
I recommend that you learn about the Gas Laws. There seems to be some sort of aversion to them here.
An interesting point on Willy’s map of temperatures in the Pacific. Notice that there are a number of readings of 30 deg C off Hokkaido (the northernmost of the Japanese islands) and in the Wonsan-Vladivostok area on the mainland side of the Japanese Sea. These are places that regularly have sea-ice in winter. So there actually are places in the ocean which reach 30 degrees in summer and still freezes in winter. Makes the often heard claim that Arctic sea-ice may reach a “point of no return” sound a bit dubious doesn’t it?
markx said @ur momisugly February 13, 2012 at 12:10 am
Dunno where you got the idea I was “insisting” that there was a “correct order of procedure”. AFAICT I pointed out that there are two distinct approaches to science, the Platonic and the Aristotelian (it’s hardly novel) and asking why we prefer one over the other. Make no mistake, this distinction, and favouritism for one over the other, is behind some of the acrimony following some of Willis’s recent posts.
An observation from my years learning ag sci: the academics frequently told me that my observations were wrong just because they conflicted with Currently Accepted Theory. One agricultural academic admitted that most of the work he and his colleagues conducted was based on observation made by farmers like The Git. The Git also notes that his farming neighbours adopted some of his practices based on their observation that what The Git was doing actually worked.
I thoroughly endorse Willis’s approach because it’s fun. And my question as to why academe insists on “unfunning” science remains… unanswered.
Willis. More interesting analysis.
I don’t think it’s accurate to state there is a hard cap on sea temperatures globally. What you state seems to be true for the tropics, which is where these temperatures occur most often. However, I see small but significant punch though from subtropical and higher latitudes. (yellow and green).
The amount is small because these regions get less chance to hit that sort of temperature. I don’t think that means you should dismiss it.
I think what you say is correct for the tropics which has a climate system different from higher latitudes. I would agree that what you say seems to apply to the tropics. I think you are perhaps going beyond the evidence you have shown here is claiming this is a global cap.
Good to see you’ve fleshed out my suggestion in your other thread that point like sharpening of the positive peaks shows a negative feedback is in play.
Keep digging.
Very interesting stuff. Because we’re on a sphere, the tropics are exposed to greater incoming solar energy that anywhere else. Whatever manages to reach the surface is essentially driving the climate system on the timescale of days and weeks, through the great convective systems and the westerly windbelts with their instabilities adding to the polewards heat transfers. But of course these mighty convections produce clouds throughout the troposphere and sometimes even punching through the tropopause, and these sure look like negative feedbacks to me. The data indicating an upper bound on SST around 30C and sustained values there for long periods and large areas is interesting, as is the apparent absence of this sort of warm zone between Africa and South and Central America, and in the eastern Pacific.
Now let’s take this insight and go back to Pangea at 265 Mya.
Temperatures are close to +10C. The Pacific is one-third bigger than today. Gondwana has moved off the South Pole and its glaciers have melted. Ocean currents have open access to the North Pole so there is no sea ice there even in the winter. There is some snow, however, at the South Pole in the winter. Large deserts cover the mid-latitudes where there is more landmass than today. Earth’s Albedo is probably a lot lower at around 0.240 versus 0.298 today, given the land is weighted to the equator and there is no ice.
The Enso is still operating except it is bigger, having two-thirds the way around the planet to work with now. The western warm pool area is now the relatively enclosed Tethys ocean at the equator.
http://www.scotese.com/images/255.jpg
How hot did get in the Tethys ocean? Global temperatures are 10C higher than today. Geography should make the Tethys even warmer in relative terms than the warm pool/Indian Ocean is today.
Hello Willis!
I know this is off topic, but i hope you forgive me.
I would like to get in contact with you to discuss some thoughs.
Could you drop me an email or something? 🙂
Keep up the good work!
(mods, if you can direct Willis to this post direct, and not post it in the tread, please do so)
[Reply: Willis will see it and take action if he wants. ~dbs, mod.]
[Thanks, dbs. Done. w.]
@ur momisuglyDavy12 on February 12, 2012 at 10:54 am
@ur momisuglyStephen Wilde on February 12, 2012 at 4:13 pm
@ur momisuglyStephen Wilde on February 13, 2012 at 1:29 am
I think you all may be mixing up absolute pressures with partial pressures. The comments of Clive Best on February 12, 2012 at 9:45 am, RobL on February 12, 2012 at 3:47 am and Anton on February 12, 2012 at 1:16 am are helpful. Also, google Raoult’s law. Ideally, evaporation is independently governed by the balance between the partial vapor pressures of the substances in solution and the vapor pressures of each substance’s gaseous phase above the solution. So, the absolute pressures don’t tell you whether there will or will not be evaporation of a given substance in solution or how rapidly it will take place (or, therefore, what the equilibrium temperature will be at the surface of the ocean). Nikolov and Zeller didn’t take partial vapor pressures into account when formulating their theory. In this regard, an aqueous planet like the Earth isn’t comparable to rocky planets like Venus or Mars. The fact that 70% of the Earth’s surface is covered by a liquid makes Earth’s climate kinda different.
@Willis Eschenbach says:
February 12, 2012 at 8:50 pm
That map is a lie: We are at “La Niña”, and the south american west coast seas are not at such temperatures (above 20º), and NEVER have been. Just come and take a bath at the sea.
http://weather.unisys.com/surface/sst_anom.gif
“So, the absolute pressures don’t tell you whether there will or will not be evaporation of a given substance in solution or how rapidly it will take place ”
Averaged over the globe absolute pressure fixes a maximum achievable temperature before non radiative processes ramp up to maintain system energy content by removing energy faster to space.. And it isn’t just evaporation but conduction and convection too plus lateral winds all of which are pressure related. In fact the negative system response involves the entire surface air pressure distribution and the relative sizes, positions and intensities of all the permanent climate zones.
Simply put it is just a global extension of Willis’s own Thermostat Hypothesis.
If evaporation is slower in one place due to higher humidity (that is where vapour pressure comes in) it will be faster in another place due to lower humidity. Overall global humidity varies hardly at all and that is a pressure based phenomenon too.
Willis Eschenbach says:
February 12, 2012 at 11:03 pm
I guess that’s the advantage to being an amateur scientist. I’m not bogged down with the prejudices of the physics teachers. I can just let the data lead me wherever it wants to go.
Seriously, Pompous, investigating a dataset is best done in the spirit of play. You have to get to know the data, you need to mess about with it, simply for the sake and the joy of messing about. You need to notice the oddities, you need to cozen it into revealing the secrets and the anomalies. You need to toss it into the air and see how the wheat separates from the chaff. You need to hold it in your hands, and turn it around and look at it from different angles, try a host of vantage points and discriminant functions.
If you march in the door all armed with your whiz-bang theory, you won’t notice or see or understand all of that stuff. As the saying goes, “To a man with a hammer, every problem looks like a nail.”
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 think some of the folks here that have been arguing about the 30° limit are doing what Willis did with N&Z. It’s been interesting to watch how this has played out.
So the equator won’t heat up much, but the energy will be carried to cooler climes, which will become warmer. Sounds reasonable. Pretty much what the CAGW crowd say.
“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.”
The problem is, Sherlock Holmes is a fictional character; and its creator, Doyle, believed in all sorts of nonsense. So while it may be a catchy phrase, I wouldn’t base scientific research on it.
ferd berple says:
February 12, 2012 at 10:45 pm
Ferd, I can accept a “normal” distribution for a measurement if you confine it to a single source – such as peak temperature at the equator. But you shouldn’t expect the Argo measurements to be “normal”. In fact they should have a rather ugly distribution at lower temperatures (because there are many effects reducing temperature, but few to none increasing temperature) with a gradual peak at some maximum temperature (OK 30 degrees C) and then nothing (well maybe a few localized higher bits). The sun can only heat up the ocean to some maximum temperature as an input. Then there are all the causes trying to lower that temperature. So the temperature can go lower, but it can never go higher.
I’m thinking of a flat aluminum surface suspended in air where the temperature on its surface can be measured at any point. A heat lamp is suspended above and is moved above the surface of the aluminum at a constant distance and speed from one end to the other. This experiment is repeated many times. The temperature histogram from this experiment will not look normal because it is not possible to heat the aluminum above a maximum temperature that is defined by the energy from the heat lamp, its distance away to the aluminum and the composition of the aluminum. As long as these things remain constant (energy from the sun, rotation of the earth, distance from earth to sun, composition of the ocean etc) the peak temperature cannot be exceeded.
Now add convection, clouds, wind etc. All of these conspire to lower the peak temperature. So the physical mechanism that limits temperature is the maximum output of the sun, the distance from the sun to the earth, the composition of the ocean and the rate at which the ocean can distribute heat.
Stephen Wilde says:
February 13, 2012 at 1:29 am
I say again. Your fantasies about global average pressure ruling the temperature are not wanted on any thread of mine. They have absolutely no scientific support. Please take them elsewhere.
w.
“Does anyone else note that Willis is taking pretty much an opposite position as he did with N&Z?”
Yes I noticed that. In fact that top limit on sea surface temperature cannot realistically have any cause other than global atmospheric pressure but apparently I am unwelcome here for making the point and my polite, rational points are being censored.
AdolfoGiurfa says:
February 13, 2012 at 4:58 am
Umm … the map you sent is a map of anomalies, it doesn’t show the actual temperature.
Also, the coldest part of the upwelling is right along the coast, in a thin band that might not even show up on a global map.
w.
Konrad says:
February 13, 2012 at 12:17 am
//////////////////////////////////
I have never seen a proper explanation as to how DWLWIR can heat the oceans given the wavelength and its consequential penetrative depth.
This is doubly problematic with a turbulent body of water (such as open open ocean) where the top micron layers are little more than wind swept spray only rarely contacting with the body below.
It would appear that the extent that DWLWIR has an effect, this is to simply accelerate the surface evaporation leading to a cooling of the very top surface. How this cooling can heat the body of water below is not sufficiently explained, especially bearing in mind the reality that the top micron layer is in any event all but divorced from the body below.
Richard M said @ur momisugly February 13, 2012 at 6:10 am
Yes, interesting is the correct term. It seems to be the case that one can either engage the Platonic method (internal ideal Forms), or the Aristotelian (external world observations), but not both simultaneously. I also note that what we do to maintain the Platonic view is to either ignore observation, or explain it away. In the paradigm case of falling objects, we say that if it were not for frictional effects then the balls would reach the ground simultaneously.
Phil says:
February 13, 2012 at 4:39 am
Phil, I fear you misunderstand these folks and what they are saying. I call them “Pressure-heads”. They believe that the greenhouse effect doesn’t exist, GHGs make no difference, and that it is simple pressure that drives the temperature of the earth well above the Stefan-Boltzmann blackbody temperature … yeah, I know, stupid, right?
This is all despite the fact that I have clearly shown, in “A matter of some gravity” that if there are no GHGs and the atmosphere is transparent, then no pressure or gravity mechanism, or any other method, can raise the surface above the S-B blackbody temperature. If that happens, the surface must radiate to space more than it absorbs, which is a clear impossibility. Duh.
My advice? I would say DFFT, don’t feed the trolls, but these guys aren’t trolls, they truly believe the nonsense that they are peddling. However, it is a mistake to either disagree or to use logic to try to educate them. Here’s the problem.
If they could understand and follow simple logic, they wouldn’t believe what they believe …
w.
Philip Bradley said @ur momisugly February 12, 2012 at 11:41 pm
Much as I admire Popper, he was quite prescriptive, rather than descriptive. Michael Faraday’s motor doesn’t appear to fit in at all well with Popper’s prescription:
http://www.nuffieldfoundation.org/practical-physics/faradays-motor
Faraday built the first motor with no theory in mind and widely circulated a description. Both Faraday and Ampere subsequently formulated different theories about how it worked. Neither theory resembles the current theory.
JimF says:
February 12, 2012 at 10:57 pm
————————————–
Jim you misunderstood my post from at leaset two perspectives. I asked about the borehole meausrements, which I think are land based near the top of a 11 mile crust where the mean flow of heat through This meausrement was not plate tectonic related. Volcanism is above and beyond that. MY question was about this mean conductive flow through a three mile crust and if that could be meausred or estimated. It is only logical that it would be considerably more then the land measurements. My second point was in regard to the residence time of this energy in the deep oceans. Is todays small flow of energy still there tomorrow, next week, next year, next century. Until the residence time of this energy is known, then we will not know how much ge thermal heat is contained in the world’s oceans.
My statement about the heat flow being greater then realised in the past was not in regard to an increase in the heat, (which has naturally decreased over millions of years) but an increase in understanding. We are finding ever more evidence of volcanism in the oceans being more active then previousely understood.