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:
Johanna, thanks for that on Endless Summer!
Yes, surf board wax comes in a variety of melting points, so the surfer can use a wax that is most appropriate for the water temperature that day. Cold water can make the wax too hard, and hot water can make the wax far too gooey or thin. So, there are different waxes for the different temperature ranges.
pochas says:
February 12, 2012 at 7:45 pm
From that excellent site:
For those claiming that there is some part of the ocean over thirty degrees C … where is it?
w.
Geoff Sherrington says:
February 12, 2012 at 7:49 pm “…Given hot above and hot below…”
I’m not Willis, but I’ll give you a partial answer. The ‘hot below’ – the heat of the Earth’s interior – expresses itself only in the oceanic spreading ridges/continental rifts and in volcanoes.
The Earth’s interior heat is almost self-contained under a layer of exquisite insulator – the crust itself. However, that heat breaks through in places, for example, at the mid-ocean rifting centers where new oceanic crust is formed as extruded and intruded lavas. This material is hot and therefore less dense, and as a result it stands high (the spreading ridges are topographic ridges).
As spreading continues, newly formed seafloor rock moves away from the hot central rift zone and cools, losing heat to cold ocean water. After about 750,000 years, the seafloor rock is as cold as that ocean water, notwithstanding that the hot asthenosphere is immediately below it. It becomes so cold and dense that it begins to press down into the asthenosphere (the abyssal plain – the sea floor away from the spreading ridges – is up to hundreds of meters lower in altitude than the spreading ridge). Finally the cold, dense seafloor plunges into the hot asthenosphere, forming a subduction zone . There it will be partially melted and resurface in volcanic eruptions.
As a result, the ocean gets some heat added to it at volcanic centers and at the ridges. However, the ocean is gigantic, and water has the highest heat capacity of any natural material. As a result, if the interior of the Earth adds even one degree to the ocean, I would be astounded.
Roger Sowell says:
February 12, 2012 at 8:34 pm
If so, take your meter to the shop. I am discussing the Argo data about the open ocean, not someone’s swimming pool or close inshore in the Gulf of Mexico. Look at the data. Look at Figure 1. I don’t care what your history tells you or what you remember about the warm ocean of your childhood. LOOK AT THE DATA IN FIGURE 1. There are 700,000 measurements there. Only 1% of them are over 30°, and only ONE TENTH OF ONE PERCENT OF THEM ARE OVER 31°C
Now, if that doesn’t spell “hard limit” to your BS meter, return it to the manufacturer.
w.
Roger Sowell says: February 12, 2012 at 8:34 pm
says: “….this…. is a good example of the hockey-stick graph problem: Take a single set of data, no matter what other data exists to the contrary, then draw conclusions about the climate from it. Mann used some tree rings, Eschenbach uses Argo temperature data….”
Gee, Roger, this is the silliest thing I have seen in a long while. Straight from the circus, are we? You apparently have no limit on the hoops you will jump through or the twists you will make to align your argument.
There is a huge difference between Mann’s interpretation, manipulation, lopping and grafting of data, followed by scientific publication and his subsequent citing by international organisations…
…..and Willis’ presentation here of some data and a few questions.
Willis Eschenbach says:
February 12, 2012 at 8:50 pm
Now that is one incredible map. I’d like to blow it up to wall mural size and hang it on my wall.
Take a look at the fetch of the equatorial Pacific. All that hot water pushed west to pile up around Indonesia. If it weren’t for Indonesia, Africa would be a roaster oven. Look at that cool water “upwelling” off the western coast of South America. It’s a lava lamp in reverse! Or else, the first skin of the onion has been peeled off and pushed back to good old Indonesia, uncovering an underlying layer of cooler water.
Is there a contour map of the Earth’s surface that would show how much water is (from time to time) piled up around Indonesia? From Peru, it must look like a small hill, at least. Are there data that show the tidal ranges of both Indonesian ports and Peruvian ports during either El Nino or La Nina?
With help from some of the Antarctic Circumpolar current moving up the west coast of SA as the Humbolt current.
Geoff Sherrington says:
February 12, 2012 at 7:49 pm
Thanks, Geoff. In addition to JimF’s reply, I can add that the geothermal heat is estimated to be on the order of a tenth of a watt per square metre or so. So there is no “heat below” for the ocean other than in limited regions, there is only heat in the top 100 metres or so, the “photic zone”. This is also (not coincidentally) the depth of the upper “mixed layer” of the ocean. It is not a coincidence because it is the heat of the sun which mixes that top layer … but only at night.
You are correct to identify vertical circulation as key to the heat exchange of the ocean. It is not generally realized that the atmosphere and ocean have opposite overturning times. The atmosphere overturns during the day, and stratifies at night. The ocean is reversed, it overturns at night, and stratifies during the day.
This allows the ocean to rid itself of the sun’s heat. Another factor that is not often considered is that by and large, the amount of energy absorbed during the 24 hours of the day is also released during the same 24 hours. During the day, with the ocean stratified, the top surface is very warm. Radiation, evaporation, and conduction/convection are all high. But because of the stratification, warmest on top, energy below the surface is trapped there.
At night, the surface cools, and the cool water starts to sink. As it does so, the energy which is deeper in the ocean is slowly raised to the surface, where it radiates, evaporates, and convects its heat away and joins the descending columns of cooler water moving downwards from the surface.
So yes, you are correct that without this vertical convection the temperature balance of the ocean would be very different.
Thanks for your interesting questions,
w.
A number of contributors here have pointed out to you that it is atmospheric pressure that determines the rate of energy flow from ocean to air and which puts a lid on the achievable temperature of the sea surfaces at current levels of solar input.
Stephen, the primary driver of ocean/atmosphere heat flow is the temperature differential, with a secondary contribution from air flow/turbulence.
Which BTW, likely explains the SST outliers above 30C. In semi-enclosed seas adjacent to large land masses, say the Gulf of Aden, the air above the ocean will be influenced by air masses that originate over land. These air masses will typically be much drier and often warmer than the usual atmosphere over the ocean. The warmer air will reduce the heat flow from the ocean (reduced temperature difference) and the reduced humidity will impede the hydrological feedback (cloud formation). Thus allowing the ocean surface to warm above 30C.
I am sure Willis will eventually get to a geographic analysis that shows land proximity to these over 30C values.
JimF says:
February 12, 2012 at 8:13 pm
R. Gates says:
February 12, 2012 at 11:27 am “…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….
Do you have a link to back up this statement. I would like to see it. According to the Ocean Page, under the Reference tab here on WUWT, indeed the heat content of the upper 700 meters of the sea has increased since about 1970, although the last decade seems to be a flat spot (little or no increase).
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Jim,
Go here and click between the different depths:
http://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/
Ocean heat content is probably the best single metric for the energy imbalance of the planet. The amount it has gone up (to as deep as we are currently measuring) over the many decades is impressive. Please note that there has been no flattening at the 2000m mark, and not as much as some skeptics would have you believe down to 700m. Some skeptics seemed puzzled by the warming of the deeper ocean, and are trying to figure out why this would be impossible. After all, how could heat be forced into the deeper ocean? In the regard, it is critical to understand areas such as the Western Pacific, where, on a cyclical basis, warm water piles up, actually forming a dome of water, and underneath this dome, downwelling of warm water occurs, taking very warm water to the deeper ocean. The Mindanao dome, near the Philippines is the prime example of this area of downwelling. Eventually some of this warm water will work its way back to the east and to the surface, but as the ocean heat content has increased, especially down to the 2000m mark, it means that less energy is leaving during cycles such as El Niño, than is entering in downwelling areas all over the worlds ocean. Perhaps this warming of the deeper ocean is in response to increased greenhouse warming of the atmosphere, or perhaps not. If it is a natural cycle, then one would need a mechanism to explain it, and one would also expect it to begin to cycle back down at some point.
Thanks, Geoff. In addition to JimF’s reply, I can add that the geothermal heat is estimated to be on the order of a tenth of a watt per square metre or so. So there is no “heat below” for the ocean other than in limited regions, there is only heat in the top 100 metres or so, the “photic zone”. This is also (not coincidentally) the depth of the upper “mixed layer” of the ocean. It is not a coincidence because it is the heat of the sun which mixes that top layer … but only at night.
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I understand (?) the geothermal heat flux estimate to be from land based borehole meausrements, yet the crust thickness on land is several miles thicker then the mean ocean crust thickness. Also, the mean volcanic heat flow into the oceans may be far greater then realised in the recent past. As the deep layers of the ocean have very little circulation how long do you think this heat energy could accumalate. In other words what is the residence time of the deep ocean volcanic and geothermal heat?
Willis Eschenbach says:
February 12, 2012 at 11:44 am
richard verney says:
February 12, 2012 at 11:02 am
… 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.
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
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As regards what you said, I think you said “..there is plenty of energy from the sun to make many ocean areas reach over 30°C…” which is a quote of something you said in your post of February 12, 2012 at 9:57 am.
My comment was perhaps a liitle bit of a cheap shot. By way of elucidation, not on this thread but on various other threads posted by you (extending over a period of several years) discussing the effects of DWLWIR from CO2, you and I have exchanged views on whether but for the DWLWIR from CO2 the oceans would freeze. In these exchanges, you claim they would. I claim that even if the DWLWIR from CO2 was not taken into account, there is sufficient solar in equatorial regions which would heat the tropical ocean to a temperature above freezing, ie, the tropical ocean would not freeze.
As part of the argument on that topic, I have suggested that your view is distorted by you using average figures (ie., average solar average DWLWIR etc which you have done in your posted article) whereas one needs to utilise local prevailing not average figures. Local prevailing solar in the tropics is high.
I accordingly agree with your statement “..there is plenty of energy from the sun to make many ocean areas reach over 30°C…”. The implications of this are that in local areas where solar is most intense it is in sufficient in amount to prevent the tropical ocean from freezing.
The reason I made this cheap shot is that on many occassions you have simply side stepped doing the calculation of solar in the tropics and have simply maintained some average figure and referred me to articles I think on the scienceofdoom (I can’t recall with certainty the specific website).
I do not consider that I am scoring some points over you. But next time we get into an argument on a relevant thread concerning the effects of DWLWIR from CO2 and the impact this has on the ocean and in particular whether the oceans would freeze but for this ‘energy’ remember the strong solar forcing in the tropics.
.
PS: Don’t take my earlier post regarding the way in which the IPCC handle data, the wrong way. I was not intending to be rude. It is just that I think that in this particular case, you are rather over strecthing the data. That is intended as a constructive comment upon a data anaysis which is a work in progress.
One horrifying thought, remember when some NASA probe was screwed up because someone failed to convert metric to inches or vice versa? I hope this isn’t some weird artificial result from some idiotic mistake like, for example, a BCD to binary ‘misunderstanding’ between the hardware and software people or “Oops, I thought the other one was the overflow bit? ”
I assume someone physically tested that ARGO floats behave just as reliably in 40 degree water as they do in 10 degree water?
R. Gates says:
February 12, 2012 at 9:30 pm
Thank you. I’ll have to look at those and think a bit, but it’s late here.
regards
richard verney says:
February 12, 2012 at 8:14 pm
Yes, richard, you pointed that out. Many times. And many times I and others have pointed out that I never said there were no temperatures above 30°. I said there was a hard limit not far above 30°.
Less than a tenth of a percent of the Argo data is at 31° or above, richard. You can huff and puff all you want about that fact, but it is still a fact. Less than a tenth of a percent is 31° or more.
I call that a “hard limit”. Nor am I alone. The phenomenon has been noted by a number of others in the past. People have cited some of those references. Here’s another. Then there’s the 1991 paper of Ramanathan and Collins, viz:
So it is a mystery to me why you pursue me with your inane claim. I didn’t say there were no temperatures in the whole ocean over thirty degrees, that’s just your attempt to nitpick my words. What I wrote were just what I called them, “Argo Notes”, it wasn’t a paper for a journal or even a full-blown post. Jeez, cut me some slack, richard, your endless bitch, bitch, bitch is unseemly. Others know what I meant about the limit on ocean temperatures. I and many people have explained what I meant.
More to the point, you know what I meant. Stop acting like you don’t, you’re not that stupid. Move on to something less boring, you are embarrassing yourself.
w.
R. Gates says:
February 12, 2012 at 9:30 pm
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When I have time, I will look at your link.
In the meantime, I enquire if it is indeed the case that the deep ocean is warming, is this really a problem? What lenth of time is required for energy stored in the deep ocean to find its way to the to a height where it can significantly affect the temperature of ocean currents distributing temperatures poleward and/or the air temperature above the ocean.
Is this measured in tens of years or hundreds or even thousands of years. In otherwords, when do you envisage that this *ie, the additional energy you suggest is being stored therein) will come back to bite?
johanna says:
February 12, 2012 at 8:18 pm
As a surfer in both tropical and temperate waters, let me chime in to say that these days, you buy your wax to match the water temperature you’ll be using it in. Tropical wax (my favorite kind) doesn’t soften as easily as cold-water wax. And as an aside, the most popular brand, in a triumph of marketing, is called “Dr. Zog’s Sex Wax” … but I digress.
Back in the day when the endless summer was made, though, we used plain paraffin wax … hang on … OK, various internet sources say 50°C, or 105°F, as the melting point of paraffin. That matches with my experience.
So I doubt greatly that the water melted the wax. I’ve been in Togo, next door to Ghana, and I suspect it was the hot tropical sun melting the wax …
My best to all the surfers out there,
w.
They are spurious until their deviation from norm can be verified and explained. It is why further investigation as to latitude, water depth, salinity is required urgently. These statistical anomalies may correlate with shallower or deeper water, if shown to be valid temps. Perhaps they occur on the lee side of land masses? Who knows? Until the data is analyzed for such?
Well yes, I guess, I should have mentioned SB limits but then I should have mentioned the boiling point of seawater, as well. oops…
Consider the top few microns of water. It is intensely bombarded by photons, fiercely blasted by various particles, undergoing evaporation distillation and complex chemical changes, while constantly exchanging gases. This layer is an energized flux field, resistant to investigation and of tiny volume. Like quantum theory – much is yet possible – not much impossible. Can any of these many factors limit SST? I don’t know… evaporation is certainly affected – but we better find out, if and what, is. That’s all I have to say about that. GK
Willis, I still think your point about the S.H. oceans being cooler was curious, as they receive vastly greater heat flux from a sun which is three million miles closer in January and about 7% more intense as compared to the NH summer. Some of this may be due to ocean currents transporting heat, but could not the self regulating, evaporation, conduction, cloud formation mechanism of the oceans be a factor in this as well? Do you know if the earth’s mean cloud cover increases in January February, as opposed to June and July?
Overall the earth is considerably cooler when it is closer to the sun. At perihelion we have a permanent loss to space of ? W/2m SWR due to increased albedo and a loss of SWR to the atmosphere, as at perihelion the SWR is falling on far more ocean, where it is absorbed into the oceans for far longer then if that SWR fell on land. Do these balance (unlikely) or is the earth gaining or losing energy during perihelion??? The TOA flux should tell us and climate models should accurately predict the observation. As these immense changes in SWR TSI happen bi-annually, then how much and how rapidly changes in most things we measure in climate, temperature, cloud cover, albedo, SST, OHC, TOA flux incoming and outgoing, must be reflected in these bi-annual changes and analyzing these relative to the bi-annual 7% perihelion/aphelion flux in SWR should give deeper insight relative to heat and energy flux within our earth system.
BTW Willis, in the very clear deep waters of the tropical ocean sunlight may penetrate deeper and accumalate longer then you think. From 660 to 3,000 feet (200 to 900 meters), only about 1 percent of sunlight penetrates. This layer is known as the dysphotic zone (meaning “bad light”).
http://www.scienceclarified.com/
It’s hiding… from Kevin Trenberth :-)))
It’s just arithmetic, I think Since saline water increases more or less linearly in density with declining temperature, it is inevitable that, given enough depth, the lowest levels would be hovering just above freezing. How “thick” that coldest layer is would perhaps vary over time, and naturally with local water depth.
I’m curious about what the temp profile looks like in deep trenches in the tropics vs high latitudes.
Keith Minto says:
February 12, 2012 at 9:19 pm
Heh. I followed the link to the wikipedia reference. It’s interesting the way the thing is defined. It’s “upwelling” until an ENSO event. In my mind, unless there is some topographic structure that would cause a moving stream of cold, dense water to be pushed or channeled to the surface, somehow pushing aside warm water, the “upwelling” simply is the way things are – the cold current is the normal flow of water along the coast of SA (and it is probably underlain by even colder, denser water).
Then along comes El Nino – the equatorial trade winds die down (because there aren’t many thunderstorms going off in the equatorial Pacific), the hill of hot water over at Indonesia succumbs to gravity and spreads out over the Pacific (I wonder how fast this tide actually moves), eventually covering the normal cold water of the Humboldt current, and creating a local economic disaster. Is that “Downwelling” or simply a slow tsunami? Finally, the warm surface water is pushed back to Indonesia (La Nina) and “upwelling” (or normalcy) returns.
Otherwise, dense things rise, and less dense things sink. And that, I don’t believe.
TimTheToolMan says:
February 12, 2012 at 3:51 pm
I’ve added the following to the head post:
Regards,
w.
richard verney says:
February 12, 2012 at 8:21 pm
I can only agree, richard. Thank you.
w.
JimF says:
February 12, 2012 at 7:20 pm
Wow, I am depressed by the nattering that goes on here. I do not believe Willis has stated a Law of Nature that sea surface temperatures are “limited to 30˚C”. He has merely shown a bazillion measurements that show that sea surface temperatures, for some reason(s), tend to maximize at 30˚C +/- a bit. A few of these bazillion measurements are indeed higher, maybe as much as 15% higher, but the tendency is 30˚C.
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Exactly, or more percisely not exactly I did not read Willis to mean this as 30c is a law, but to show it as a principle to be generally true, and let us discuss the observations. The rest appears pedantic.