Guest post By Ben Herman and Roger A. Pielke Sr.
During the past several months there have been various, unpublished studies circulating around the blogosphere and elsewhere claiming that the “greenhouse effect” cannot warm the Earth’s atmosphere. We would like to briefly explain the arguments that have been put forth and why they are incorrect. Two of the primary arguments that have been used are
- By virtue of the second law of Thermodynamics, heat cannot be transferred from a colder to a warmer body, and
- Since solar energy is the basic source of all energy on Earth, if we do not change the amount of solar energy absorbed, we cannot change the effective radiating temperature of the Earth.
Both of the above statements are certainly true, but as we will show, the so-called “greenhouse theory” does not violate either of these two statements. (we use quotation marks around the words “greenhouse theory” to indicate that while this terminology has been generally adopted to explain the predicted warming with the addition of absorbing gases into the atmosphere, the actual process is quite a bit different from how a greenhouse heats).
With regards to the violation of the second law, what actually happens when absorbing gases are added to the atmosphere is that the cooling is slowed down. Equilibrium with the incoming absorbed sunlight is maintained by the emission of infrared radiation to space. When absorbing gases are added to the atmosphere, more of emitted radiation from the ground is absorbed by the atmosphere. This results in increased downward radiation toward the surface, so that the rate of escape of IR radiation to space is decreased, i.e., the rate of infrared cooling is decreased. This results in warming of the lower atmosphere and thus the second law is not violated. Thus, the warming is a result of decreased cooling rates.
Going to the second statement above, it is true that in equilibrium, if the amount of solar energy absorbed is not changed, then the amount of IR energy escaping out of the top of the atmosphere also cannot change. Therefore the effective radiating temperature of the atmosphere cannot change. But, the effective radiating temperature of the atmosphere is different from the vertical profile of temperature in the atmosphere. The effective radiating temperature is that T that will give the proper value of upward IR radiation at the top of the atmosphere such that it equals the solar radiation absorbed by the Earth-atmosphere system.
In other words, it is the temperature such that 4 pi x Sigma T4 equals pi Re2 Fso, where Re is the Earth’s radius, and Fso is the solar constant. Now, when we add more CO2, the absorption per unit distance increases, and this warms the atmosphere. But the increased absorption also means that less radiation from lower, warmer levels of the atmosphere can escape to space. Thus, more of the escaping IR radiation originates from higher, cooler levels of the atmosphere. Thus, the same effective radiating temperature can exist, but the atmospheric column has warmed.
These arguments, of course, do not take into account feedbacks which will kick in as soon as a warming (or cooling) begins.
The bottom line here is that when you add IR absorbing gases to the atmosphere, you slow down the loss of energy from the ground and the ground must warm up. The rest of the processes, including convection, conduction, feedbacks, etc. are too complicated to discuss here and are not completely understood anyway. But the radiational forcing due to the addition of greenhouse gases must result in a warming contribution to the atmosphere. By itself, this will not result in a change of the effective radiation temperature of the atmosphere, but it will result in changes in the vertical profile of temperature.
The so-called “greenhouse effect” is real. The question is how much will this effect be, and this is not a simple question. There are also questions being raised as to the very sign of some of the larger feedbacks to add to the confusion. Our purpose here was to merely point out that the addition of absorbing gases into the atmosphere must result in warming, contrary to some research currently circulating that says to the contrary.
For those that might still question this conclusion, consider taking away the atmosphere from the Earth, but change nothing else, i.e., keep the solar albedo the same (the lack of clouds would of course change this), and calculate the equilibrium temperature of the Earth’s surface. If you’ve done your arithmetic correctly, you should have come up with something like 255 K. But with the atmosphere, it is about 288 K, 33 degrees warmer. This is the greenhouse effect of the atmosphere.
Tallbloke and 899,
Here’s my point in a practical way. The CO2 concentration is approximately 387 ppm. So, let’s say that 1/10 will send an emission of radiation to Earth daily, and round the figure to 39. I want to say that Earth receives whatever comes from the sun plus the 39 from CO2 per unit. I want to say that CO2 warms the Earth. You say that Earth receives whatever comes from the sun and nothing more but CO2 slows Earth’s cooling. The advantage of my approach is that it quantifies the effects of CO2 and it describes the force of emitted radiation from CO2.
jae says:
Phil explained this…but I just wanted to add one more thing, which is to demystify the 2nd Law a little bit: The Second Law is not some magical statement; it is simply a statement of what happens on a macroscopic level because of the statistics of a large number of particles or processes. So, when you put an object at some temperature T near a hotter object, it doesn’t detect the hotter object is there and magically stop radiating energy to it; it is simply that the amount of radiation that it emits and is absorbed by the hotter object is less than the amount of radiation that the hotter object emits and it absorbs.
The Second Law is really quite intuitive in most cases. For example, take the case of a box divided by an impermeable membrane with one side of the box containing a gas maintained at a certain pressure and the other side with the gas maintained at half that pressure. Now poke a hole in the membrane. The 2nd Law would say that the pressure in the first side will drop and that in the 2nd side will rise and not the other way around. However, this is intuitively obvious at the level of the atoms in the gas: there will be many more atoms of the gas impinging on the hole from the high pressure side than from the low pressure side and hence the net flow will be from high pressure to low pressure. If you made the pressures so small that one side contained only 10 atoms and the other half 5, there would in fact be some possibility of seeing a violation of the 2nd Law. E.g., you could look later and see 11 atoms in the 1st side and only 4 in the second. However, once you have something reasonably large amount of atoms (and numbers on the order of something like 10^20 are typically what are involved) then such violations become so astronomically unlikely as to be essentially impossible.
Stephen Wilde says:
July 24, 2010 at 10:42 am
“R. Gates says:
July 24, 2010 at 10:12 am (Edit)
The oceans act as a heat sink, not as a trap in the sense of GHG’s.”
And the proportionate scales are ?
If the oceans act as a sink they also act as an output.
Where does the effect of the air fit in as a comparison ?
Where does the effect of CO2 as a minor portion of the total greenhouse effect fit in as a comparison ?
Where does the effect of anthropogenic CO2 as a minor part of natural CO2 (no one suggests that ALL the recent rise is anthropogenic) fit in as a comparison.
I submit total insignificance and any such effect as there may be is negated by an unmeasurable change in the speed of the hydrological cycle as per the findings of Professor Miscolczi
________________
My point being that the oceans store heat in various longer time scales than CO2. The oceans act as a buffer to moderate to some extent the extremes in climate change. The question being: Is the 40% rise in CO2 since the 1700’s (regardless of the source, though most of the increase is certainly anthropogenic) enough to overwhelm any of the natural buffering (feedback) processes, and so bring about AGW, to whatever degree, minor or “catastrophic”?
Theo Goodwin says:
July 24, 2010 at 10:46 am (Edit)
You are calculating net radiation absorption for the object. I have no quarrel with that calculation. However, you then apply your reasoning to a individual emission of radiation and, in doing so, you deny it causality. Consider an analogy. In my fireplace are five logs of uniform size and all are blazing brightly. One log rolls out of the fireplace. I scoop it and put it back in. Net change to the fire in the fireplace is zero. There is your calculation. But then you apply it to the individual log that had rolled out and you say that it does not add energy to the fire – but that is clearly false, right? The log that I scooped back into the fireplace is a cause and has effects. You are denying causality to the emissions of radiation coming from CO2 molecules.
I don’t think I’m saying that, and apologies for failing to make it clear. To use your analogy, when the log rolls out of the fire (earth emits a longwave radiation photon into the air) the fire is then 20% cooler. You scoop it up and put it back in (greenhouse bounces photon earthwards, a bit less than 50/50 chance) and now the fire is back to where it started. No addition, no net loss. When you go out for the evening and the log rolls out again (photon escapes to space), Earth cools.
Moral, get a fire guard. 🙂
Everyone reading this forum owes you a great debt of gratitude for your first-rate contributions. Thanks so very much.
Thank you for the compliment, and thank you also for the courteous way you have debated. That goes for Jim D and everyone else on this thread too.
Peter says:
July 24, 2010 at 8:27 am
So then what does warm the surface? The nett energy flow to the surface must increase for the surface to warm, so where does it come from? It cannot receive energy from convection or evaporation, so it must be from radiation. (Admittedly, it can receive extra nett energy from the inhibition of convection etc, but you can’t blame CO2 for that) If it is from back-radiation then the surface must be receiving at least 4W/m2 in radiation in order to warm by 1.2 deg. Just because there’s a radiative imbalance at the TOA does not provide a mechanism for the surface to warm.
Peter
Joel’s right. In my “quick and dirty calculation” I got an increase of ~6.6 w/m2 at the surface – not 4w/m2. That’s becuse only ~60% of what’s emitted at the surface is emitted at the TOA. To increase TOA emittance by 4 w/m2 the surface would have to emit an extra 6.6 w/m2.
This increases surface emission from 390 watts/m2 (~288K) to 396.6 watts/m2 (~289.2K). An increase of 1.2 deg.
R. Gates says:
July 24, 2010 at 11:03 am (Edit)
This concept, often repeated here on WUWT, that LW back radiation from GHG’s in the atmosphere cannot possibly effect the ocean heat flux is too simplistic.
Whoaaah! I didn’t say that. I said downwelling longwave can’t penetrate the ocean and heat it directly.
if the absorption of the LW emission from atmospheric GH gases reduces the gradient through the narrow suface layer, the heat flux from the deeper layers will be reduced, leaving more of the heat introduced in the top 300 meters or so to remain there to increase water temperatures.
I know several experiements in the field have been carried out to prove this is exactly the case, and I’ll look for those links…
I’ll be interested to see them, thanks for taking the trouble. So far I know of several experiments which have been carried out to attempt to prove it. I’m not aware of any which convincingly do so. I’m always happy to be educated though.
anna v
There is a big difference between “very few” greenhouse gases and “no” greenhouse gases. The first few ppm cause most of the greenhouse effect.
tallbloke,
I think you agreed that there are water molecules that absorb the IR. Are these part of the ocean? I think so. Therefore, does the ocean absorb IR? Yes.
The point of the other part is that the ocean would be cooler if there were zero downward IR flux at its surface as opposed to if there were a few hundred W/m2 (as is the case). I don’t see how that could be controversial.
John Whitman says:
July 24, 2010 at 8:47 am
“[…]of delta concentration/time. It appears to me that therefore, it is the rate of change of the rate of change of T that is caused by the rate of change of CO2 concentration.
?Can this be, or do I have it backwards?”
Get rid of one derivative on each side and what do we get?
“The rate of change of T is caused by the CO2 concentration.” Can’t be – that would imply that in pre-industrial times with a largely constant CO2 con temps would have to change.
So i think you have it backwards; in my opinion
The rate of change of CO2 concentration is proportional to the temperature anomaly.
Or, if you absolutely want to use the double derivative:
The rate of change of the rate of change of CO2 concentration is proportional to the rate of change of the temperature anomaly.
Rob says:
July 24, 2010 at 10:38 am
I think this is an interesting point actually – everone talks about the warming of back radiation to the earths surface, but what about the effect it may have as it hits the oceans (71 % of the planets surface) and causes evaporation – that may have a net cooling effect. Has this ever been studied ?
Think about it, it can’t possibly be a net cooling effect!
R Gates said:
“This concept, often repeated here on WUWT, that LW back radiation from GHG’s in the atmosphere cannot possibly effect the ocean heat flux is too simplistic. It is absolutely true that LW radiation cannot penetrate beyond the skin layer of the ocean, however, the skin layer is absolutely critical in determining heat flux rising from deeper sunlight heated layers. LW heating of the skin layer of the ocean reduces the size of the temperature gradient through the skin layer and reduces the flux. Thus, if the absorption of the LW emission from atmospheric GH gases reduces the gradient through the narrow suface layer, the heat flux from the deeper layers will be reduced, leaving more of the heat introduced in the top 300 meters or so to remain there to increase water temperatures.”
Absolutely. There we have it .
One has to reduce the energy flow from ocean to air to increase overall global temperature because the heat capacity of water is so hugely greater than that of air and the sea surface temperaures (netted out globally) are what determine the air temperature with the greenhouse effect of the molecules in the air being an insignificant contribution in comparison to the oceanic effect.
Yet evaporation always has a NET cooling effect because the latent heat of evaporation ALWAYS exceeds the amount of energy required to change the water molecules from water to vapour. That is an inevitable consequence on Earth of the pressure differentials between ocean, air and space and the phase changing properties of water from ice to liquid to vapour.
SO
LW heating of the skin layer of the ocean INCREASES the size of the temperature gradient through the skin layer and INCREASES the flux.
because more evaporation ALWAYS has a NET COOLING effect.
Falsify that and I’ll reconsider.
Jim D says:
July 24, 2010 at 11:27 am (Edit)
tallbloke,
I think you agreed that there are water molecules that absorb the IR. Are these part of the ocean? I think so. Therefore, does the ocean absorb IR? Yes.
Not for long though, because the concentration of all that mighty downwelling IR promptly evaporates the surface molecules and off they go, taking the latent heat of evaporation with them.
The point of the other part is that the ocean would be cooler if there were zero downward IR flux at its surface as opposed to if there were a few hundred W/m2 (as is the case). I don’t see how that could be controversial.
See Stephen’s reply to you a short time ago. I submit that we are in the territory of Roger Pielke’s ‘don’t knows’. The evaporation will cause surface cooling. The greenhouse effect in the atmosphere will slow down cooling. Which one wins by how much for how much of the time in which part of the world? We don’t know.
I’m hungry, can we leave it there for now?
John Whitman,
“Again my thought is =>”It appears to me that therefore, it is the rate of change of the rate of change of T (temp of earth system) that is caused by the rate of change of CO2 concentration (earth atmosphere)”.
?Or do I have that backwards?”
—
I would only say: The equilibrium temperature is determined by the amount of GHGs. [Note that some people here dispute that, but I don’t, and it follows from the arguments in the main posting]. When GHGs change fast, it is difficult to say what happens in detail to the way temperature follows it because you have to take into account various time scales, including slow ocean responses. What you can say, is that if CO2 doubles and stays there, the temperature will be higher when equilibrium is reached again which may take decades [How much is also debated]. This thread is about a steady-state situation, not the details of how it goes from one steady state to another.
Anders Boman says:
July 23, 2010 at 6:13 pm
“[…]Is it really correct that the AGW alarmists think that CO2 will indirectly cause an increase in water vapour which will create an even greater greenhouse effect? That does not make much sense.[…]”
Depends. Dr. James Hansen seems to think so:
“Chp. 10: Venus. “If we also burn the tar sands and tar shale, I believe the Venus syndrome is a dead certainty.” ”
from
http://www.amazon.com/Storms-My-Grandchildren-Catastrophe-Humanity/dp/1608192008/ref=pd_rhf_p_t_2
I did not read or buy the book, though. So i’m not entirely certain if he bases the Venus Syndrome idea on water vapor feedback.
Other ideas brought forward by warmists:
-Methane-induced warming, leading to runaway breakdown of clathrates; leading to huge firestorms due to a combustible CH4-O2-mix.
-H2S rising from oceans due to dying sealife; poisoning terrestrial life; leading to a mass extinction.
I often poke fun at these ideas; hoping i trigger reactions from visiting AGW folks; sorry, a nasty habit of mine.
tallbloke,
“I’m hungry, can we leave it there for now?”
Agreed. That’s my morning shot too. Truce.
Anders Boman says:
July 23, 2010 at 6:13 pm
“[…]Is it really correct that the AGW alarmists think that CO2 will indirectly cause an increase in water vapour which will create an even greater greenhouse effect? That does not make much sense.[…]”
Re-reading your question… in a general sense, ALL the climate models use this assumption! Otherwise they are not able to produce the scary projections! The climate models are not programmed to simulate a runaway meltdown, though; at a certain point the modeled greenhouse effects of CO2 and H2O reach diminishing returns so the projected temperature rise reaches an asymptotic line.
But none of these models can explain the past temperature rise without assuming water vapor feedback! They use water vapor feedback to triple or quadruple the warming they would get from their modeled CO2 behaviour.
So, yes, not all warmists are also catastrophists, but ALL of them rely on this water vapor feedback hypothesis.
Jim D says:
July 24, 2010 at 11:53 am (Edit)
When GHGs change fast, it is difficult to say what happens in detail to the way temperature follows it
It doesn’t follow it. Temperature changes precede changes in co2 levels at all timescales.
Right, dinner…
DirkH says:
July 24, 2010 at 11:31 am
Get rid of one derivative on each side and what do we get?
“The rate of change of T is caused by the CO2 concentration.” Can’t be – that would imply that in pre-industrial times with a largely constant CO2 con temps would have to change.
So i think you have it backwards; in my opinion
The rate of change of CO2 concentration is proportional to the temperature anomaly.
Or, if you absolutely want to use the double derivative:
The rate of change of the rate of change of CO2 concentration is proportional to the rate of change of the temperature anomaly.
———————
DirkH,
Somehow I knew you would pick up on my comment based on your way up the stream comment:
DirkH, I am trying to extract from the post by Ben Herman and Roger A. Pielke Sr how the change in rate of cooling of T (temp of earth system) is related in the time change domain to their suggestions that it is caused by the change in CO2 concentration. They say if you change CO2 conc then there will be (all other things constant) a change in the rate of cooling of the earth system. The quantitative units of that would be delta CO2 conc/time causes delta T/time/time .
If it is the other way around as you suggest, namely that the rate of change of the rate of change of CO2 concentration is proportional to the rate of change of the temperature anomaly, then it does not follow from their post.
I am just probing the time change domain.
John
tallbloke says:
July 24, 2010 at 11:23 am
R. Gates says:
July 24, 2010 at 11:03 am (Edit)
This concept, often repeated here on WUWT, that LW back radiation from GHG’s in the atmosphere cannot possibly effect the ocean heat flux is too simplistic.
Whoaaah! I didn’t say that. I said downwelling longwave can’t penetrate the ocean and heat it directly.
if the absorption of the LW emission from atmospheric GH gases reduces the gradient through the narrow suface layer, the heat flux from the deeper layers will be reduced, leaving more of the heat introduced in the top 300 meters or so to remain there to increase water temperatures.
I know several experiements in the field have been carried out to prove this is exactly the case, and I’ll look for those links…
I’ll be interested to see them, thanks for taking the trouble. So far I know of several experiments which have been carried out to attempt to prove it. I’m not aware of any which convincingly do so. I’m always happy to be educated though
_____________
Here’s a bit of background:
http://journals.ametsoc.org/doi/full/10.1175/JTECH1756.1
http://www.agu.org/journals/ABS/2006/2004JC002689.shtml
http://earth.esa.int/workshops/ers97/papers/ridley/
But here’s some research:
http://adsabs.harvard.edu/abs/2006AGUSM.A44A..02M
My real point is that the effects of what happens at skin layer of the ocean from increases in downward LW radiation from GHG’s is far more complex than ‘the oceans don’t absorb LW” beyond the skin layer. The warming of that skin layer from increased LW from GHG’s does indeed play a role in heat flux from the deeper ocean layers to the atmosphere.
Roy Clark says:
July 23, 2010 at 10:21 am
The surface warming part of the ‘greenhouse effect’ is just the downard IR radiation from the atmosphere to the surface. Most of this originates in first kilometer layer above the surface. However, there is no equilibrium. The temperature of this layer is mainly set by convection from the surface. The idea that CO2 can cause any kind of climate change is incorrect.
The surface heating is dynamic….
IT IS IMPOSSIBLE FOR A 100 PPM INCREASE IN ATMOSPHERIC CO2 CONCENTRATION TO CAUSE ANY KIND OF CLIMATE CHANGE…
_____________________________________________________
Perhaps you or someone else could clear up something for me and other laymen.
I keep on hearing that the CO2 global warming theory is an untestable hypothesis, and thus incapable of being proven right or wrong. It seems that is because there are three assumptions made with regard to CO2.
The first is that CO2 absorbs and re-emits IR radiation causing a net warming effect. That is covered in this article.
The second is that CO2 is “well mixed” in the atmosphere, with the result that it impossible to test, on a local level, for the validity of the first assumption. It’s a difficult assumption for skeptics to validate with direct data, because equipment as simple as wet-bulb/dry-bulb thermometers is unavailable for making CO2 measurements at the ppm level.
The third assumption seems to be that the effect of CO2 on temperature is longer term, and is not seen in a matter of minutes or hours.
The uniformity of mixing suggests that CO2 is in equilibrium over the whole planet, and thus lacks local effects. This is unlike water, which has local effects that are decidedly proven. The land of west Texas, for example, is substantially drier than the area around Galveston and therefore has a different diurnal heat profile.
Just how well mixed is CO2, anyway? Over a short time period, such as a single day, or even a season, there are substantial variations in local CO2 concentration. Therefore just as there are local effects associated with atmospheric water, there should be local effects associated with local changes in the level of CO2.
If these local variations do exist, they lead to the possibility of using local micro-climate data to tease out the effects of the different ppm readings of CO2 in the atmosphere on the daily variation in temperatures.
So, has anyone bothered to look for effects of day-vs-night CO2 levels, and measured them?
It’s also possible to investigate the results of forcing the local CO2 level. Orchard people using water sprinklers overnight to protect their trees see a temperature of 4 to 5 degrees F at six feet above the ground while the surrounding area is at or below freezing. The local rise in temperature could be statistically linked to the increase in the partial pressure of water vapor. Similarly, one might measure the effects of injection of CO2 into the local atmosphere, and the results could provide proxy data that might help establish or disprove the uniformity of CO2 without having to undertake a wide-ranging series of difficult and expensive station measurements of CO2.
Experiments on open air “fertilization” with CO2 have been run. There were large amounts of CO2 released at lake Nyos and lake Monoun in Cameroon, West Africa. Scientists are now degassing African lakes.
Deserts are not only colder at night due to a lack of water they are much hotter during the day compared to the same latitudes where there is an abundance of moisture. Has anyone bothered to look at the data and tease out the effects of the different % of water in the atmosphere on the daily temperatures? Have they separated the effects of phase change and clouds from the IR absorption transmission energy?
REFERENCES:
The use of sprinklers to prevent heat loss is used by orchards and nurseries to prevent damage to plants during the night when temperatures are expected to go below freezing is more evidence. (However water’s effect on temperature is due to phase change energy, the effects of clouds as well as the IR absorption transmission energy.)
CO2 is Well Mixed — or is it an artifact of data gathering technique?
4.In keeping with the requirement that CO2 in background air should be steady, we apply a general “outlier rejection” step, in which we fit a curve to the preliminary daily means for each day calculated from the hours surviving step 1 and 2, and not including times with upslope winds. All hourly averages that are further than two standard deviations, calculated for every day, away from the fitted curve (“outliers”) are rejected. This step is iterated until no more rejections occur.
http://www.esrl.noaa.gov/gmd/ccgg/about/co2_measurements.html
NOAA CO2 measurement method
WHEAT
”The CO2 concentration at 2 m above the crop was found to be fairly constant during the daylight hours on single days or from day-to-day throughout the growing season ranging from about 310 to 320 p.p.m. Nocturnal values were more variable and were between 10 and 200 p.p.m. higher than the daytime values.”
CO2 depletion
”Plant photosynthetic activity can reduce the Co2 within the plant canopy to between 200 and 250 ppm… I observed a 50 ppm drop within a tomato plant canopy just a few minutes after direct sunlight at dawn entered a green house (Harper et al 1979) … photosynthesis can be halted when CO2 concentration approaches 200 ppm… (Morgan 2003) Carbon dioxide is heavier than air and does not easily mix into the greenhouse atmosphere by diffusion…”
CO2 measured up to 640PPM in 1939/1940 http://www.biokurs.de/treibhaus/literatur/kreutz/kreutzwspapprox.gif
In an earlier post I quoted.
I replied.
I have problems with this. You cannot absorbed more energy than is available to the receptive molecule. Perhaps Ben Herman and Roger A. Pielke Sr would like to quantify the amount of surface
emitted LWR that CO2 is receptive to that escapes directly into open space.
I believe my statement is correct but I need to point something out.
Whilst more radiation cannot not be absorbed than is available from the emitting body, more energy can be stored. Since radiation is expressed as a unit of energy input over time then by adding more receptive molecules we increase the energy capacity or if you like energy density per volume.
Stephen Wilde wrote, “The rate of energy release from the oceans to the air varies depending on internal ocean cycles.”
Don’t forget wind speed, direction, etc., which vary with the coupled ocean-atmospheric processes.
tallbloke: Returning to (remaining on) the discussion of longwave radiation and the oceans, the following post at RealClimate and the related paper always struck me as a reach:
http://www.realclimate.org/index.php/archives/2006/09/why-greenhouse-gases-heat-the-ocean/
In terms of experiments, it seems to lack–what’s the term?–control.
You have more discussion at your blog than I do. Is it worth a post?
Bob Tisdale says:
July 24, 2010 at 1:54 pm
In terms of experiments, it seems to lack–what’s the term?–control.
Hoooyuss. Not half mate.
You have more discussion at your blog than I do. Is it worth a post?
I’ll gladly host it, but I’d have thought E.M. Smith would be better qualified to deconstruct the ‘experiment’ than me. Should I ask him, or do you want to?
John Whitman says:
July 24, 2010 at 12:18 pm
“[…]concentration. They say if you change CO2 conc then there will be (all other things constant) a change in the rate of cooling of the earth system. The quantitative units of that would be delta CO2 conc/time causes delta T/time/time .”
You define “the rate of cooling” as delta Calories/time , it seems. Quite reasonably. Pielke&Herman say: “This results in warming of the lower atmosphere and thus the second law is not violated. Thus, the warming is a result of decreased cooling rates.
”
So the lower parts of the atmosphere warm according to that. That means the upper part must cool; because of conservation of energy. This means the temperature gradient gets steeper. That means the conveyor belt of convection and conduction becomes more effective when the temperature anomaly gets higher on the ground and lower in upper layers. Pielke&Herman left that one out.
I think it was so clear to me that i made a mental leap. But you see that without this mechanism Pielke&Herman’s description does not describe reality well. Imagine you have CO2 conc’s = N and temperature stays constant. (Idyllic pre-industrial times; man and nature in harmony.) Now the first human lights a campfire; CO2 conc’s rise to N+1. Pielke&Herman’s world would now have ever increasing temperatures if you say that delta CO2/time causes a delta T/(time^2).
A cooling mechanism becomes more efficient when the temperature gradient rises. Pielke&Herman didn’t state it explicitly but i think they don’t have to – every cooling mechanism behaves this way. Did i assume too much? I don’t think so; we’re trying to model a physical reality.