Guest Post by Willis Eschenbach
There is a more global restatement of Murphy’s Law which says “Nature always sides with the hidden flaw”. Parasitic losses are an example of that law at work.
In any heat engine, either natural or manmade, there are what are called “parasitic losses”. These are losses that tend to reduce the temperature differentials in the heat engine, and thus reduce the overall efficiency of the engine. In general, as a percentage parasitic losses increase rapidly with ∆T, the temperature differences in the engine. In the climate system, two main parasitic losses are the losses from the surface to the atmosphere by way of conduction and convection (sensible heat), and the losses from surface to atmosphere by way of evaporation and transpiration (latent heat). Both of these parasitic losses act to reduce the surface temperature with respect to the overlying atmosphere, by simultaneously cooling the surface and warming the atmosphere … nature siding with the hidden flaw to reduce the overall system efficiency. So I decided to see what the CERES data says about parasitic losses. Figure 1 shows the parasitic losses (the sum of sensible and latent heat losses), as a percentage of the total surface input (downwelling longwave plus shortwave).
Figure 1. Parasitic losses (latent and sensible heat loss) from the surface to the atmosphere. Percentage of parasitic loss is calculated as the sum of sensible and latent loss, divided by the total surface input (downwelling shortwave plus downwelling longwave).
I was most interested in how much the parasitic loss changes when the total surface input increases. Figures 2 to 4 shows that situation:
Figures 2-4. Scatterplots, parasitic loss in watts per square metre (W/m2) versus total surface input (W/m2). Parasitic loss is loss as sensible and latent heat. Gold line shows the loess smooth of the data. Red dots show land gridcells, which are one degree square (1°x1°) in size. Blue dots show ocean gridcells.
I was very encouraged by finding this result. I’ve written before about how at the warm end of the spectrum, parasitic losses would increase to the point where most of each new additional watt striking the surface would be lost as sensible and latent heat, and that little of it would remain to warm the surface. These graphs bear that out entirely. Here’s why.
The slope of the gold line above is the rate of increase in parasitic loss for each additional degree of warming. As you can see, the slope of the line increases from left to right, although the rate of increase goes up and down.
In order to understand the changes, I took the slope (change in parasitic loss divided by the corresponding change in surface input) at each point along the length of the gold line for both the land and the ocean separately. Figure 5 shows that result.
Figure 5. Change in parasitic loss (in W/m2) for each additional W/m2 of surface input. “Wobbles”, the looped parts in the two graphed lines reflect subtle changes in the loess smooth, and can be ignored.
Now, what are we looking at here? Well, this is how the parasitic loss changes as more and more energy is input to the surface. Where there is little surface input, the loss is low. In fact, at the South Pole the situation is reversed, and the net flow of energy is from the atmosphere to the surface. This is the result of huge amounts of energy being imported from the tropics.
The key point, however, is that as we add more and more energy to a given gridcell the amount of parasitic losses rises, in perfect accordance with nature siding with the hidden flaw. And at the right hand end of the scale, the warmest end, for every additional watt that is added, you lose a watt …
Is this relationship shown in Figure 5 entirely accurate? Of course not, the vagaries of the smoothing process guarantee that it isn’t a precise measure.
But it clearly establishes what I’ve been saying for a while, which is that parasitic loss is a function of temperature, and that at the top end of the scale, the marginal losses are quite large, close to 100%.
Now, as you can see, nowhere is the parasitic loss more than about 30% … but the important finding is that the marginal loss, the loss due to each additional watt of energy gain, is around 100% at the warm end of the planet. Here is the parasitic loss for the planet as a whole versus total surface input as shown in Figure 2:
Figure 6. Change in parasitic loss (in W/m2) for each additional W/m2 of surface input, as in Figure 5, but for the planet as a whole.Change in parasitic loss (in W/m2) for each additional W/m2 of surface input. “Wobbles”, the looped parts in the two graphed lines reflect subtle changes in the loess smooth, and can be ignored.
Note also that across the main part of the range, which is to say in most of the planet except the tropics and poles, about half of each additional watt of energy increase doesn’t warm the surface … it simply goes into parasitic loss that cools the surface and warms the atmosphere.
Best to all,
w.
PS—If you disagree with what I’ve said please quote my words. That lets all of us know just exactly what you disagree with …
rgb, I think it’s misleading to count only one direction (downelling) of the LW radiation. The surface input is either the absorbed solar only (SW) or the net radiation (SW + LW), which is also acceptable. SW + LW(downwelling) as a surface input makes no sense and it’s misleading IMO.
Willis,
You make an excellent point about CERES data when you say,
So I use them, with caveats, as the best that we have.
My research for many years has dealt with boundary layer processes, and thunderstorms and tornadoes for which I have published a number of papers (yes, peer reviewed). There does not exist the complete physics of these processes, so we make approximations and parametrizations which often rely heavily on statistics. It is not ideal for sure, but, as with CERES data, it is the best we have right now. Hopefully our understanding will continue to improve. As such all weather forecasts should be used with caveats and all forecasts are probabilities…given the initial data what is the most likely outcome given our present knowledge. Many people (a lot on this forum) want deterministic forecasts and trash the models when a forecast does not work. The models (including climate models) are all approximations and the best we have.
I am not defending climate models, or more specifically the modelers. I have had many frustrating dealings with these modelers. But the models can have use if we know and abide by their weakness, something the modelers do not seem to want to do (too many perks involved as I well know.)
rgbatduke Mar 26 12:44pm – As always, yours is a very interesting and informative comment. Thank you. However, this time, your comment seems to go a bit further than usual, and indicates that the CERES data can be used to give a reasonably firm value (or range of values) for what the IPCC calls Climate Sensitivity:-
“ Not only do you get “water vapor” feedback, you get a very accurate picture of total feedback from all sources directly from the CERES data, ready to be plugged into even a very simple single layer model to get a very simple estimate of the plausible range of global warming. The data already knows everything you need to know to handle the global problem.”
If I am understanding you correctly, CERES data shows that Climate Sensitivity is “anywhere from 0.5 C to 1.C “), which is well below the IPCC estimates but in line with theoretical calculations that others have made using eg. the expected rate of increase of the hydrological cycle with temperature [see the table on page 2 of http://www.royalsocietyhighlands.org.au/WilliamKininmonthAnswersToAdvanceQuestions.pdf
“Rate of increase of evaporation : 6%/deg C; Surface temperature response : 0.7 deg C.“].
Is there any chance of getting any of this into the peer-reviewed literature, or is WUWT as far as it can get under the present journal gate-keepers?
PS. Regarding your 12:54pm comment re LWIR. There was a long and detailed discussion on this in WUWT some time ago, in which Leif Svalgaard explained the science in ever increasing detail and with amazing patience. I doubt that the other person budged their thinking one iota, but the real benefit was that there were large numbers of other people who did learn a lot. So as long as the resolutely dumb are few and open-minded observers are many then these arguments are still worth conducting. Rather like climate science, really.
@Steven Mosher
Some really good points about radiative transfer models. This strange phenomenon occurred to me as well, so many people completely trash every aspect of climate models but are, at the same time, totally accepting satellite data as gospel. And I thought, duh…they both use radiative transfer physics to obtain modeled data. Not defending climate models, as they have many many other assumptions, but an interesting observation.
Sister Michelle says:
March 26, 2014 at 1:24 pm
Just found this post on climate change, and thought your readers would find it interesting and worth comment:
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I did not find the article interesting. Besides being grossly off topic of this thread, I found your link to contain verbose pablum, with no hard data and many platitudes. I didn’t bother to read the whole thing, but skimmed it and re- read a few lines to make sure he’d really said (waffled around) a couple of stupid remarks, trying to make his inanities have merit and seem less false as he tried to maintain some sort of hip and cool status with the me- too climate alarmist crowd. I won’t point out the number of blatantly incorrect statements made by Myles Allen, but you can keep “believing in him”, if you wish.
What do YOU think of this current post by Mr. Eschenbach?
Ps to Sister Michelle (with all apologies to Willis et al for pursuing this off- topic subject)
Ma’am, Please stick around and become a regular WUWT reader. I have no doubt that you mean well and want to do the right thing. I visited your site and you have a good heart, but you have been led astray. Give yourself time to discover the truth of things, by becoming a regular reader of these threads. You will find your beliefs challenged and it may be painful, for a time, but you may find that the truth will be better for your purposes.
How did you do that Willis? Those first two scatter plots look just like dolphins. Ok, it’s late and maybe it’s my imagination, so let me get back to reading the rest of your post.
I’m intrigued already.
Regards
Willis, Have you a comment about the interesting green spot in your first image?
It is almost above Lake Eyre in South Australia, which is below sea level.
Good to see scatterplots. Not surprising to see the global view (first graphic) resembles NASA displays of global vapor pressure or temperature. Just overlay a plot of the vapor pressure of water from zero to 40 C. Then add clouds.
The land view is interesting. Likely deserves more study from the point of view of surface albedo due to photosynthesis.
Tropical ocean surfaces are the source of most global energy. Plot the same data against latitude, should be a higher slope in the tropics. Capped at around 30 C. by clouds.
Paul Westhaver says:
March 26, 2014 at 1:40 pm
“I am elevating the notion of entropy production as a measure of efficiency to defeat so called “common- sense” assertions wrt heat transfer efficiency.”
I am puzzled by this statement, and I don’t think you are distinguishing pure heat-transfer systems from systems that are producing thermodynamic work from thermal energy.
In a heat-transfer system that does not produce work, as in a heat exchanger, you always get the maximum entropy production. In the computationally simple case of a large hot reservoir at temperature Th and a cold reservoir at Tc, for a heat transfer of Q from hot to cold (“large” here means that these temperatures don’t change materially from this transfer), the entropy production is simply S = (Q/Tc) – (Q/Th), no matter how the transfer of this amount of energy is done. The math gets more complicated if the temperatures change during the process, but the principle is the same.
If you are producing any thermodynamic work (W) in the process of removing energy Q from the hot reservoir, there will be less entropy production, because the amount of thermal energy Qc (= Q – W) arriving at the cold reservoir is less, and so the entropy production is less: S = ([Q-W]/Tc) – (Q/Th). The more work W you produce for a given Q from the hot reservoir, the higher your thermodynamic efficiency (e = W/Q by definition), but also the lower your entropy production.
The 2nd Law says that the minimum entropy production is zero, and this would occur at the Carnot efficiency. If entropy production is zero, the process (and each sub-process) is reversible. Carnot worked out what this would mean in detail – the problem is the (theoretical) Carnot cycle would take infinite time. It should be thought of as no more than an idealized theoretical limit.
Now, there is a point that if you can get the details of the work production closer to the Carnot reversible limit, you can reduce entropy reduction and increase efficiency. This is why the gradual expansion of gases in a turbine gets higher efficiency than the explosive expansion in an internal combustion engine, for the same source temperatures.
But for a given type of process, if you can increase the temperature difference, you can increase the efficiency (and reduce the entropy production). This is why a diesel engine, with its higher compression ratio and therefore higher source temperature, has a higher efficiency than Otto-cycle gasoline engines.
Enough for now. I hope we haven’t veered too far off topic.
Interesting use of the term “parasitic losses”. More generally in thermodynamics and mechanical engineering these are referred to as “irreversibilities.”
Per figures 5 & 6: Why are losses between 250- 500 W/m2 decreasing as input increases? Why is the effect more pronounced over land than ocean?
Should Figure 3 be labeled “Land Only” not “Red = land, Blue = ocean”?
Curt says:
March 26, 2014 at 12:47 pm
While I am not totally comfortable with Willis’ used of the term “parasitic losses” here, as to me that implies an “intent” to the system as in an engineered design…
——-
Consider the “design” in the context of the constructal law http://en.wikipedia.org/wiki/Constructal_law as proposed by the same Bejan cited above.
Alan Robertson says:
March 26, 2014 at 3:04 pm
Per figures 5 & 6: Why are losses between 250- 500 W/m2 decreasing as input increases? Why is the effect more pronounced over land than ocean?
———
Melting sea ice/snow cover?
Thanks, Willis. You keep pointing at interesting aspects that are basic for climate science but seem to have been overlooked in the race to declare atmospheric CO2 content the key variable.
I’ve been telling you all for years that the thermal effect of GHGs in attempting to slow energy loss to space is negated by an increase in non-radiative energy transfer mechanisms which involve the entire global air circulation and not just local emergent phenomena such as thunderstorms and dust devils.
The correct issue to address is as to how much the global air circulation is affected by our emissions as compared to natural variations caused by sun and oceans.
I’d guess it would be too small to measure.
Having established that there is such a thermostatic mechanism one then needs to address the issue as to how it can work and at that point one just has to bring in the Gas Laws.
Nor should we ignore the adiabatic warming of descending air in helping to reduce radiative energy loss from surface to space.
It is no coincidence that most of the time the Antarctic is covered by a high pressure cell with descending air and that Willis points out that
“In fact, at the South Pole the situation is reversed, and the net flow of energy is from the atmosphere to the surface.”
That net flow from atmosphere to surface cannot all be coming from inflowing tropical air because the semi permanent high pressure cell blocks such inflows for much of the time.
It isn’t DWIR that reduces surface cooling around the globe. It is adiabatically warmed descending air which, at any given moment , is half the entire atmosphere.
“And we all know that everyday objects far from a big fire are all heated by nothing but longwave radiation, sometimes to the point where they burst into flame.”
Hmmm, that’s an interesting statement.
Willis said:
“Note also that across the main part of the range, which is to say in most of the planet except the tropics and poles, about half of each additional watt of energy increase doesn’t warm the surface … it simply goes into parasitic loss that cools the surface and warms the atmosphere”
In the tropics adiabatic uplift cools the surface and at the poles adiabatic descent warms the surface.. The net effect globally from adiabatic convection is therefore zero provided the scale and speed of the convective cycle changes to counter any radiative imbalances between poles and tropics.
The main part of the range (other than poles and tropics) is then warmed or cooled depending on the ever shifting balance between poles and tropics resulting in global air circulation changes which move the climate zones to and fro.
That movement of climate zones to and fro is the negative system response in action because it regulates radiative losses to space so that energy in always equals energy out over time.
It is the speed and scale of the non-radiative processes that changes to negate any radiative imbalances so as to achieve overall radiative equilibrium despite internal system variables such as differences in atmospheric composition.
That system deals with variations in atmospheric conductive AND radiative capability, both of which can vary with atmospheric composition.
As long as the categorical distinction between conservative HEAT TRANSFER and non-conservative RADIATIVE INTENSITY is ignored, confused depictions of the climate system and mistaken attributions of “forcing” will persist. What Willis here calls “parasitic” effects are, in fact, the principal mechanisms of thermal energy transfer between Earth’s surface and the atmosphere, as seen from the myopic viewpoint of a heat engine. That may satisfy low-level academic preconceptions, but it hardly represents a credible specification of the climate system.
Willis in this post, you showed the maximum temperatures that occur when the Ocean heats http://wattsupwiththat.com/2012/02/12/argo-and-the-ocean-temperature-maximum/ Is there any way that you can correlate the “parasitic” heat loss with the energy that appears to be missing based on the Argo float temperatures? When the Ocean does not heat beyond 30C, the heat is still there, but it is somewhere else.
Curt,
One piece at a time…
“In a heat-transfer system that does not produce work, as in a heat exchanger, you always get the maximum entropy production. In the computationally simple case of a large hot reservoir at temperature Th and a cold reservoir at Tc, for a heat transfer of Q from hot to cold ”
detaS = Q/(ThTc) x (Th-Tc), for heat transfer between 2 reservoirs.
deltaS –> 0 as (Th-Tc) –> 0.
I think MaxLD used to play with aerofoils.
Not that there’s anything wrong with that . . . .
Paul: You say:
“deltaS = Q/(ThTc) x (Th-Tc), for heat transfer between 2 reservoirs.”
That is what I said – just one algebraic manipulation away…
“deltaS –> 0 as (Th-Tc) –> 0.”
Of course.
Ok Curt we agree!
Cheers.