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During the past several months there have been various, unpublished studies circulating around the blogosphere and elsewhere claiming that the “greenhouse effect” cannot warm the Earth’s atmosphere.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.
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Stephen Wilde says:
July 25, 2010 at 2:57 am
“Instead the energy in the water vapour makes the vapour lighter than the surrounding Oxygen and Nitrogen so it rises towards the tropopause and at some higher level is released again when condensation occurs. However at that point the energy is much higher and is simply accelerated away to space by radiative processes.”
The main rain bearing clouds form below 3000m, this is way below the tropopause, at this altitude most of the energy released from cloud formation remains in the troposphere.
An increased rate of evaporation that has resulted from an increase in energy input is not going to cause surface cooling, in fact an increased evaporation rate is the result of surface warming.
Dear Ben Herman and Roger A. Pielke Sr. :
You are making simple statements, that are fundamentally wrong:
…”When absorbing gases are added to the atmosphere, more of emitted radiation from the ground is absorbed by the atmosphere.”….
or
…”Now, when we add more CO2, the absorption per unit distance increases, and this warms the atmosphere. “….
Here you implicitly ASSUMED that adding CO2 will increase the absorbing power of the atmosphere. The atmosphere is a complex system and its absorbing power is a function of many other things. However, this absorbing power can be computed without climate models and greenhouse theories, solely using observations and computations applying first principles.
Observations show that in the last 61 years the CO2 content of the atmosphere increased by 30 per cent and during this time the absorbing power of the atmosphere remained constant. In view of the above, your comments on the surface warming as a result of “ slowing down cooling” is obsolete. AGW is simple non existent.
Please see the details in my recent E&E article:
THE STABLE STATIONARY VALUE OF THE EARTH’S
GLOBAL AVERAGE ATMOSPHERIC PLANCK-WEIGHTED
GREENHOUSE-GAS OPTICAL THICKNESS
http://multi-science.metapress.com/content/c171tn430x43168v/?p=ad1e44ae55754e548ae474618bfb4102&pi=8
Andrew W said
“An increased rate of evaporation that has resulted from an increase in energy input is not going to cause surface cooling, in fact an increased evaporation rate is the result of surface warming.”
If evaporation has a net cooling effect then the surface warming must be more than negated by the conversion of sensible to latent heat. Either the sea surface or the surface air temperature will drop or a combination of both in proportion to the pre existing temperature differential between them because the evaporative process takes energy from where it is most readily available. Either way you get a net surface cooling from more IR. Only more energetic shorter wavelengths can get past the evaporative barrier to warm the oceans.
“The main rain bearing clouds form below 3000m, this is way below the tropopause, at this altitude most of the energy released from cloud formation remains in the troposphere.”
That’s high enough. How many thermometers do we have at 3000m ?
The energy gets shifted away from the surface fast enough to prevent surface warming. Otherwise evaporation could not have a net cooling effect.
Morris Minor says:
July 25, 2010 at 2:10 am
[–snip for brevity–]
Back radiation has not been detected, why continue with this mis-construed concept?
Why? because it makes for a good fiction …
Andrew W says:
July 25, 2010 at 3:54 am
[–snip for brevity–]
An increased rate of evaporation that has resulted from an increase in energy input is not going to cause surface cooling, in fact an increased evaporation rate is the result of surface warming.
Andrew, I think you just said the same thing twice, but disagreed with yourself …
😉
stevengoddard says:
July 24, 2010 at 9:36 pm
anna v
It is difficult to believe that direct conduction from ground to air contributes much heat to the atmosphere. The vast majority of the heat is transmitted radiatively.
It is not a matter of belief, it is a matter of the laws of physics as applied to gases. O2 and N2 have kinetic energies that can be increased by direct collisions, conduction, and by Compton scatterings by the infrared photons.
You made a statement that the planet would be cold and with no convection if there are no greenhouse gases, and this is what I am objecting to. Just the Coriolis force and the day night surface temperature differences will create seasonal winds . Convection will increase transfer of energy by conduction. N2 and O2 though not as efficient as CO2 and H2O are still there and have to behave as gases have to behave given the initial conditions.
‘An increased rate of evaporation that has resulted from an increase in energy input is not going to cause surface cooling, in fact an increased evaporation rate is the result of surface warming.’
But the process itself still removes energy from a surface.
If you were to go outside after a shower, the wind would give the energy required for water to evaporate. You would still feel the cold though, as more energy is taken from the surface. If the energy from an outside source is enough, then you wouldn’t feel the any cold from more energy been taken from the skin
cba, I can appreciate ignoring internal temps but in the deep ocean you have a very cold region bounded above and below by warmer temps. Yes we want to disregard the earth’s internal heat but I’m not sure you have a very well defined notion of surface temperature if you disregard extensive cool areas. The earths temp on the continents at deep ocean depths is quite hot (see accounts of south African mines or deep boreholes). There has to be some process removing heat from the ocean and it has to be a large effect considering the extent of deep ocean cold.
vukcevic says:
July 24, 2010 at 3:21 pm
What many climate scientists do not understand that 1 qcm of water has more than 3000 times heath capacity of a 1 qcm of air, maybe some of them have never experienced a full solar eclipse (personally 2), you can feel a nearly instant large temperature drop. Perhaps a night in a cloudless Sahara desert would be money well spent.
_________________________________________________________-
I think day and night studies spent in the Sahara Desert measuring the solar insolation, atmospheric H2O and CO2 and the resulting temperatures at various locations along the latitude line that includes desert and savanna plus areas on either side such as the the Atlantic Ocean on the west, and the Red Sea and Egypt’s Nile river on the east would yield some very interesting data. Heck you could even take an area and flood it with CO2 and study the results. Studies of plant response in FACE (free air CO2 enrichment) systems have been done as well as studies of tree response in OTC (open top chamber) systems.
Similar studies in arid desert conditions where humidity would be minimized should yield the temperature response to increased CO2…. if there is any that can be measured. The region’s low relative humidity rarely exceeds 30% and is often in the 4% to 5% range.
Andrew W says:
July 25, 2010 at 3:54 am
……An increased rate of evaporation that has resulted from an increase in energy input is not going to cause surface cooling, in fact an increased evaporation rate is the result of surface warming.
____________________________________________
Steve and Willis are talking about tropical rain clouds such as this click They form when the temperatures are high.
Steve and Willis are talking of the heat transport mechanism cloud formations (cumulonimbus) in the tropics and sub tropics and hot summers in the temperate zones. Cumulonimbus do not form when the temperatures are moderate or cold so you are correct when you state that most clouds are not cumulonimbus or thunderheads. However the cumulonimbus that Steve and Willis are talking about are the mechanism used by the earth to get rid of excess heat fast.
“Thunder storms develop on hot, humid days. When an air mass near the Earth’s surface contains excessive water vapor (humidity) and rises on updrafts (currents of air), it expands and then cools as it rises. Eventually the air mass cools so much, the vapor inside converts to liquid form. This process emits heat into the air in the immediate vicinity which causes the air to rise faster. At a rate of fifty miles per hour, thunderheads form relatively quickly and can reach altitudes of nearly 75,000 feet in about 17 minutes.“ click
So thunderheads are a heat transport system from the earth to the upper atmosphere.
I did a quicky look at the the formation of afternoon thunderstorms on the US east coast. The number of storms formed per month decreases with an increase in latitude going from about 25/month in Florida to 20/month in South Carolina. The number suddenly drops to 10/month in the middle of North Carolina where the temperatures become more moderate.
When you start talking oceans then you start talking cyclones, another mechanism for the earth uses to dump heat.
Observational evidence for an ocean heat pump induced by tropical cyclones
ABSTRACT
“Ocean mixing affects global climate and the marine biosphere because it is linked to the ocean’s ability to store and transport heat1 and nutrients2. Observations have constrained the magnitude of upper ocean mixing associated with certain processes3, 4, but mixing rates measured directly3, 5 are significantly lower than those inferred from budget analyses6, suggesting that other processes may play an important role. The winds associated with tropical cyclones are known to lead to localized mixing of the upper ocean7, 8, 9, but the hypothesis that tropical cyclones are important mixing agents at the global scale10 has not been tested. Here we calculate the effect of tropical cyclones on surface ocean temperatures by comparing surface temperatures before and after storm passage, and use these results to calculate the vertical mixing induced by tropical cyclone activity. Our results indicate that tropical cyclones are responsible for significant cooling and vertical mixing of the surface ocean in tropical regions. Assuming that all the heat that is mixed downwards is balanced by heat transport towards the poles, we calculate that approximately 15 per cent of peak ocean heat transport may be associated with the vertical mixing induced by tropical cyclones. Furthermore, our analyses show that the magnitude of this mixing is strongly related to sea surface temperature, indicating that future changes in tropical sea surface temperatures may have significant effects on ocean circulation and ocean heat transport that are not currently accounted for in climate models.”
Stephen Wilde says:
That makes no sense at all. Things radiate in proportion to the 4th power of the temperature. In order to get more radiation from the mid- or upper-troposphere into space, you have to warm it up. So, what your proposal amounts to is a claim that the mid- and upper-troposphere warm without warming (or even with cooling) the surface & lower troposphere. Where is the evidence for this?
In fact, it is recognized that on a global scale the mid- and upper-troposphere will on average warm more than near the surface, with the largest differential occurring in the tropical atmosphere. This is what is called the “lapse rate feedback”, a negative feedback included in all of the climate models that accounts for the fact that you don’t have to warm the surface as much as the upper troposphere will warm in order to re-establish radiative balance after an increase in greenhouse gases. So, your proposal is that this negative feedback is being underestimated, which is an interesting contradiction with those skeptics who claim (on the basis of some data that is known to have contaminating artifacts) that the “hot spot” in the tropical troposphere isn’t even there…i.e., that the upper troposphere is not warming significantly faster than the surface. You would need to propose that it is actually warming (relative to the surface) much faster than the models predict.
stevengoddard says:
July 24, 2010 at 9:36 pm
anna v
It is difficult to believe that direct conduction from ground to air contributes much heat to the atmosphere. The vast majority of the heat is transmitted radiatively.
===========
Steve,
a more generic stefan’s law is P = epsilon * sigma *(Tb ^4 – Ts^4) where epsilon is emissivity, sigma stefan’s constant, Tb the temperature of the object and Ts is the temperature of the surroundings which in this example are assumed to be the same emissivity as the body of interest. you’ll note when the surroundings is assumed to be he same temperature, there is no radiative transfer net power going on and only when the temperature is absolute 0 will there be the full simple stefan’s law transfer out.
at the surface of the Earth, the atmosphere is about the same temperature although its emissivity will be much less on average – that is except for strong absorption lines. However, the radiation from the surface is (at 288.2k) about 391 w/m^2 and in clear skies, ghgs permits about 274 w/m^2 to pass through to the tropopause. The average convection appears to be around 100 w/m^2 at the surface and it drops to practically 0 by the tropopause. Conduction is very low compared to convection but convection is actually quite significant down low as it’s part of the h2o cycle.
While radiative may be the majority of power transfer, it is not a vast majority lower down where convection is important also.
Yipee! My thermos flask does work after all!
And I suppose that this means that radiation emitted by colder regions of the atmosphere above the troposphere can be absorbed by CO2 in the warmer regions of the troposphere and re-radiated back into space! Wow so CO2 can cause global cooling as well as warming. But which is the greater of these two miniscule effects? Does it matter?
JM
No. First of all at 3000m AGL the densest layer of greenhouse gases lies between the cloud and the ground. In that case the GHGs act as a layer of insulation between the cloud and the ground. Second of all, due to atmospheric lapse rate, it’s going to be colder above the clouds than below them. Second law of thermodynamics – heat flows from warmer to colder. The heat will travel upwards not downwards.
Net effect, once heat gets dumped by condensation in a cloud at some significant height AGL (say 500m or more) that heat is headed upward, not downward, from there.
This doesn’t even consider what happens due to the high albedo of the cloud during the daytime where there is a much lower albedo below it (i.e. not snow or ice underneath). In that case a huge portion of insolation in the visible spectrum gets bounced right back out into space.
Andrew W says:
July 25, 2010 at 3:54 am
Stephen Wilde says:
July 25, 2010 at 2:57 am
“Instead the energy in the water vapour makes the vapour lighter than the surrounding Oxygen and Nitrogen so it rises towards the tropopause and at some higher level is released again when condensation occurs. However at that point the energy is much higher and is simply accelerated away to space by radiative processes.”
The main rain bearing clouds form below 3000m, this is way below the tropopause, at this altitude most of the energy released from cloud formation remains in the troposphere.
An increased rate of evaporation that has resulted from an increase in energy input is not going to cause surface cooling, in fact an increased evaporation rate is the result of surface warming.
=================================
so you’re claiming that 3km is below most of the ghgs? Since h2o vapor is 2/3 of the ghg effect, just how much h2o vapor is there above the cloud top?
and, you also seem to be claiming that those clouds with 30-40% reflectivity don’t increase the albedo and lower the incoming solar radiation.
note too that your cloud tops are not only above most of the h2o ghg contribution, they also radiate in a continuum, not just spectral lines. You don’t think that radiating a continuum is going to permit more power to escape than radiating in a spectrum?
oh, let me guess! incoming solar actually only occurs during a fraction of the day while our evaporation is occurring all the time and therefore clouds mostly form at night, retaining IR but raining out by morning.
Clouds typically aren’t near the 4 feet height of a Stevenson shelter.
I think the effect is mostly that when there are clouds in the sky they are typically accompanied by higher humidity level near the ground. It’s the higher water vapor content that slows the rate of night time cooling at ground level.
“Back radiation” appears to be nonsense. When two bodies out of thermal equilbrium have a transfer path between them heat flows from the warmer to the colder (2nd law of thermodynamics). The farther out of equilibrium the faster the transfer. I suppose one could envisage back radiation as what causes the slowdown in heat flow the nearer to thermal equilibrium the bodies become but that doesn’t change the end result of the net heat flow going from warmer to colder.
Well, Virginia, if you can leverage that cooler objects making warmer objects hot into the design of a Stirling Engine it will solve all the world’s energy problems in one fell swoop.
I can’t wait to see it working, Dr. Spencer. I’d wish you good luck but you’re going to need far more than luck.
I see Dr. Spencer thinks cooler objects can somehow heat warmer objects.
If he can incorporate that into a Stirling engine it would solve all the world’s energy problems. Color me skeptical until I see it working.
Here is a high resolution false color image of the IR images I previously posted (an area north of Denver):
http://mas.arc.nasa.gov/gallery/images/scene_9611028.jpg
We can now see that there are shadows to the lower left of clouds, jet contrails and some small water features (lakes or reservoirs). This helps in the analysis of the original spectral bands at lower resolution:
http://mas.arc.nasa.gov/gallery/comparison.html
I believe that the following analysis is correct, but as I am not an expert (only a BS in physics), some of the details may be wrong. Take it as an opinion.
It is noted that the spectral band images are calibrated for radiance and I will assume that equal brightness will mean similar radiation power flux (although radiance is not exactly equal to flux due to vector angle differences). These were shot by an E2 (modified U2) and could be from about 70,000 feet, but this is not mentioned in the data description. The fact that large jet contrails are in the images suggests it was much higher than the 40,000 feet that jets fly below. There is also very little atmosphere above this altitude so most of what we see will be similar to a view from space. I also assume that the grayed-out images at 2.89 and 14.21 um are caused by CO2.
In the incoming Sun shortwave flux the dark areas will indicate absorption while light areas indicate reflection back to space. For the outgoing “blackbody” longwave flux (above about 4 um where the cloud shadows disappear because the land is so bright) the bright areas indicate emission while dark areas indicate lower emission. The Sun has very low output in this region so the clouds will appear dark (reflecting very little IR from the Sun compared to the emissions from the land below).
While bands above 14.21 um were not captured by the sensor, they should look similar to 14.21 um. This is because CO2 has strong absorption in this region. There is still about 25% of the total longwave emission in this area so this is where CO2 has the most effect on warming.
Concerning the different features in the images:
Land: strongly absorbs in the visible and near IR, strongly emits in the far IR. Bare land heats the most and also emits the most. Urban features would be worse (pavement, etc.).
Vegetation: strongly absorbs in visible bands, some reflection in near IR, strongly emits in the far IR but would be cooler than bare land.
Surface Water: strongly absorbs in visible and near IR (more so than land), doesn’t emit much in far IR until you get above 5 um. Appears to reflect or emit around 3.21 to 3.52 um and absorb around 4 um.
Water Vapor: there appears to be strong absorption near 1.9 um which may be surface water vapor.
CO2: Appears to absorb at 2.89 and 14.21 um. The fact that it is a gray fog seems to suggest that it is re-emitting some radiation downward or transferring it to the surrounding air as thermal heat. It it were saturated (no longer able to absorb and emit) it would be as bright as the land and more transparent.
Clouds: Highly reflective for most incoming Sun near IR. Appears dark in longwave IR but may still be reflective. The Sun’s output in longwave IR may actually be reflecting off the top of the clouds but is much lower than the flux from the land below. Provided the clouds reflect longwave IR (and there are suggestions that cloud cover causes heat retention) this should cause warming due to partial downward (diffuse) reflecting of the outgoing earth flux.
The real question concerning AGW: is the CO2 really that important? It appears to be above 14 um and surface water appears to have some output above 5 um (it is a cooler blackbody than the hot land and should have more output at longer wavelengths). Clouds could be a negative feedback because they reflect so much of the incoming flux, but they also may reflect some of the outgoing flux back to the surface.
The spectral images have been contrast extended so no real conclusions can be drawn without access to the raw data and knowing the calibration factors. However, they do provide a layman’s view of what is actually happening by showing the CO2 fog bands, incoming flux absorption, cloud reflection and blackbody flux out.
“Ferenc M. Miskolczi says:
July 25, 2010 at 3:57 am”
Hello Professor and thanks for contributing.
Your findings suit me very well so I would be happy to see them confirmed and widely accepted.
Is anyone in authority taking your work seriously with a view to publicising the clear implication that changes in the composition of the air short of a change in total density are wholly ineffective in energy budget terms ?
re; downwelling radiation heating water
Seems simple enough to test by experiment. Put a heat lamp over a pan of water and see if the water temperature rises. I suspect it will but I also suspect that the rate of heating will be vastly effected by the relative humidity of the air above the water and also the rate of movement of the air over the water, i.e. place a fan blowing air across the water and see if that doesn’t go so far as to not just cancel the radiative heating but actually overpower it depending on the ambient humidity level.
I see a book title here:
Swamp Cooling for Dummies – How Evaporation Works to Limit Global Warming
Dave Springer said:
“Put a heat lamp over a pan of water and see if the water temperature rises. I suspect it will but I also suspect that the rate of heating will be vastly effected by the relative humidity of the air above the water and also the rate of movement of the air over the water, i.e. place a fan blowing air across the water and see if that doesn’t go so far as to not just cancel the radiative heating but actually overpower it depending on the ambient humidity level.”
Quite right, Dave.
In the open air above Earth’s oceans and on average globally the humidity is always low enough and the wind strong enough to always (on average globally) ensure that the radiative heating from downward IR is always overpowered or at least matched by the thermal net cooling effect of the increase in evaporation that it causes.
The reason for that is the relative densities and pressures of the oceans and the air and the properties of water with it’s attendant phase changes.
It also provides the mechanism whereby optimum optical depth is maintained (as per Professor Miscolczi) because the speed of the hydrological cycle just changes to meet the requirements imposed by those relative densities and pressures.
Morris Minor says:
July 25, 2010 at 2:10 am
Morris, the way you explain it, is the way I remember it explained in my school-days.
You “talk” the way an “old classic style scientist” would talk. I can understand it.
It is easy to agree.
Dave Springer:
And, this all relates to the greenhouse effect how? Could you give me an example of a greenhouse effect model (either a simple one or a complex one) that claims that the net flow of heat is going from colder to warmer? All the examples that I have seen have the net flow being from warmer to colder as the Second Law says must be the case.
I guess you are another believer in the Second Law as magic, whereby a cooler object placed near a warmer object magically detects this fact and stops radiating any of the energy toward the warmer object.
The scientific community, by contrast, believes in the Second Law as a statement of statistical physics, whereby the colder object will always absorb more heat from the warmer object than the warmer object absorbs from the colder object. From this point of view, a colder object can indeed make a warmer object warmer than it would be in the absence of the colder object.
Think of it this way: An earth with no greenhouse gases has all of the radiation that it emits going directly out into space. An earth with greenhouse gases has some of that radiation absorbed by the atmosphere….and because the atmosphere then has a nonzero temperature, it will emit radiation, some of which will go back down to the earth’s surface. (Whether you want to call this “back radiation” is a legitimate pedagogical question. Some people, like this retired meteorology professor http://www.ems.psu.edu/~fraser/Bad/BadGreenhouse.html , are quite militant about this being a poor use of terminology, but he doesn’t disagree on the physics, just how it is most accurately described.)