Guest post by Dr. Pat Michaels – reposted (with permission) from World Climate Report
A new paper just published in Geophysical Research Letters by Roger Davies and Mathew Molloy of the University of Auckland finds that over the past decade the global average effective cloud height has declined and that “If sustained, such a decrease would indicate a significant measure of negative cloud feedback to global warming.”
Davies and Molloy are quick to point out that part of the decline from 2000 to 2010 in cloud height is due to the timing and variability of El Niño/La Niña events over the same period, however, there still seems to be evidence that at least part of the decline may remain even when El Niño/La Niña variability is accounted for.
Figure 1 (below) shows the history of the effective cloud height, as determined by Davies and Molloy from satellite observations, from March 2000 through February 2010.
Figure 1. Deseasonalized anomalies of global effective cloud-top height from the 10-year mean. Solid line: 12-month running mean of 10-day anomalies. Dotted line: linear regression. Gray error bars indicate the sampling error (±8 m) in the annual average (source: Davies and Molloy, 2012).
The dotted line is the linear trend through the data as determined by Davies and Molloy and has a value of -44 meters per decade (+/- 22m). However, clearly the trend is influenced by the large negative departure centered around the beginning of 2008 that was related to a moderate La Niña event in the Pacific Ocean. To avoid the influence of the this event, Davies and Molloy calculate the difference between the cloud heights during the first and last years of their record and still find a decline of 31 m/dec (+/- 11m). Although this latter technique doesn’t fully account for the El Niño/La Niña signal in the record, it does at least give some indication of the influence of the large negative departures in the latter half of the record, and indicates that the overall decline is not simply an artifact of a single event.
The average global cloud height is linked to the average global temperature—generally, the higher the average cloud height, the higher the average surface temperature, and vice versa. The tie-in is related to the height in the atmosphere from which clouds radiate long-wave radiation to space. The higher up they are, the cooler they are, and thus the less radiation they lose to space, which means the surface stays warmer.
Davies and Molloy calculate that on a decadal basis, the radiative forcing from increasing greenhouse gases is the same as that caused by either a decrease in the total global cloud amount of ~0.3% (which would allow more short wave radiation from the sun to hit the earth’s surface) or an increase in the global average cloud height of ~19 meters (about 62 feet). All to say, that clouds play a major role in the earth’s climate and that small changes in cloud characteristics can add to (via positive feedbacks) or offset (via negative feedbacks) the warming pressure put on the climate from increasing greenhouse gases. A point well-recognized by Davies and Molloy when they write “Changes in cloud properties in response to rising surface temperatures represent some of the strongest, yet least understood, feedback processes in the climate system. “
Davies and Molloy hoped to better our understanding of cloud behavior by quantifying changes in cloud heights as determined from data obtained from the Multiangle Imaging SpectroRadiometer (MISR) carried aboard the Terra satellite. The MISR data provides stereo imaging that can be used to determine the heights of clouds. The MISR data is not perfect, as it misses very thin clouds (like high level cirrus) and very homogeneous clouds (like some cirrus from thunderstorm anvils), but perhaps its biggest shortcoming is that the period of available data is still pretty short (i.e., only begins February 2000). Nevertheless, an investigation of what data is available from the MISR instrument can provide some insight as to the variability of cloud heights and their relationship to the earth’s climate.
Which was the main purpose of the work of Davies and Molloy.
In full recognition of the limitations of the data, here is how Davies and Molloy conclude their paper, in their own words:
Finally, we note that the climate data record of [effective cloud height] anomalies may ultimately indicate a measure of long-term cloud feedback that may be quite separate from the correlations discussed above [i.e., correlations with El Niña/La Niña]. Ten years is unfortunately too short a span for any definitive conclusion, as the linear trend in global cloud height of -44 +/- 22 m over the last decade is partly influenced by the La Niña event, and may prove ephemeral. The difference between the first and last year of the decade, not directly affected by the La Niña event, is -31 +/- 11 m. If sustained, such a decrease would indicate a significant measure of negative cloud feedback to global warming, as lower cloud heights reduce the effective altitude of emission of radiation to space with a corresponding cooling effect on equilibrium surface temperature. Given the precision of the MISR measurements, we look forward to the extension of this climate data record with great interest.
According to the calculations of Davies and Molloy, the negative climate forcing from a decrease in the average global cloud amount during the past 10 years has more than offset the positive forcing from an increase in greenhouse gases from human activities. It is little wonder that the rate of global temperature rise during this period has been so paltry!
Davies and Molloy write that they “look forward to the extension of this climate data record with great interest.” We want to be the first to second that sentiment.
Reference:
Davies, R., and M. Molloy, 2012. Global cloud height fluctuations measured by MISR on Terra from 2000 to 2010. Geophysical Research Letters, 39, L03701, doi:10.1029/2011GL050506.
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richard verney says:
February 9, 2012 at 8:11 pm
“…The variations are all but infinite since variation occurs depending upon the size of the cloud both 2 dimensionally and 3 dimensionally,the composition of the cloud, the altitude at which the cloud forms, the location where the cloud forms, the time of day the cloud forms and dissipates, the day & month when the cloud forms…”
Amen to that brother – great post!!!
The massive reduction in global cloud hight in 2008 is a fascinating event, about which the authors of the paper conjecture was caused by the ‘moderate La Niña’ in the Pacific. However, this period was also the time of a prolonged period of low solar activity, and I wonder if this is another possible candidate for the observed cloud effect. Graph of sunspot number, courtesy Solen.info, available here…
http://www.solen.info/solar/cycl23_24.gif
Bart says:
February 9, 2012 at 7:04 pm
Doug Cotton says:
February 9, 2012 at 6:39 pm
“The atmosphere may well retain extra thermal energy, but temperatures underneath can only rise if there is an actual transfer of thermal energy downwards.”
(1) There is a continual transfer of thermal energy downwards. It comes from the Sun.
(2) When it is impeded from leaving, it pools up until equilibrium between incoming and outgoing can be reestablished. That pooling up leads to a rise in temperature.
________________________________________________________
(1) Yes, the Sun is what keeps you warm. It’s been happening for a few billion years without getting too hot. But the IPCC hangs its hat on a thing they inappropriately call the greenhouse effect – due to what they also inappropriately call “backradiation.” So let’s keep to the topic I was talking about, shall we?
(2) Yes, maybe the atmosphere gets a little closer to freezing point until a fraction of a second later when more radiation is emitted from the atmosphere and eventually makes its way to space, perhaps after being rejected by the surface and a billion other warmer air molecules it visits.
Michael Tobis says:
February 9, 2012 at 9:40 pm
“In addition, it indicates how climate scientists really talk to each other, and what one of the key roles of simulation models is in the actual practice of climate science.”
Michael, we already know how they talk to each other. They are full of doubt. We have read the ClimateGate e-mails. And we know that the key role of the models is not predicting the future climate; but that they only pretend to do this to ensure ongoing funding. All this is known. The MSM is currently playing catch-up and starts to explain it to their customers.
The public image of scientists will never recover from this; they will lose their aura of objectivity forever.
Dr Burns says:
February 9, 2012 at 2:36 pm
Doug Cotton wrote:
>>But my main point is that there is only one way in which thermal energy from the atmosphere can get back to the surface. It does not “fall” out of the sky by downward convection.
(1) The primary heat transport mechanism between clouds and the Earth’s surface in convection, evaporation and condensation.
(2) Radiative transfer is very small because of relatively small temperature differences (30 degrees C or so). ….
____________________________________________________________
(1) Condensation pf course leads to the precipitation I was talking about. Did you really mean to include convection and evaporation in the downward transfer of thermal energy?
(2) You seem to be talking about net upward radiation (not downward as I was discussing) for why else are you referring to a temperature difference of 30 degrees? Even the good old Stefan-Boltzmann Law would expect the warmer temperature to be the source of net radiation. Indeed such radiation from the surface is not large because there is often a temperature difference of less than 3 degrees (never, well hardly ever 30 degrees) between the surface and the first millimeter of the air – and that’s all that counts. Most thermal energy leaves the surface by diffusion, conduction, convection, evaporation and chemical processes, not by radiation – which is why that -18 deg.C figure is garbage if you follow me.
The average global cloud height is linked to the average global temperature—generally, the higher the average cloud height, the higher the average surface temperature, and vice versa.
We are cooling down.
Could we stop plotting lines through scattered data. Except for the four year dip the plot essentially flat. I clearly do not understand the tendency in things climatological to do so. It just makes it hard to consider this science instead of reading tea leaves. In most other hard sciences a value that has plus minus bars of 50% would be a dead giveaway of the randomness and a reason to hit the thinking chair some more.
Bart says:
February 9, 2012 at 7:04 pm
I note that you like to talk about dams as if thermal energy stacks up like a traffic jam or a river.with a dam. That’s not what actually happens.
Take a look at what’s really going on up there around the tropopause above which the temperature then starts to rise with increasing altitude in the stratosphere, so there’s a nice little “valley” for all your extra “heat”.
But check out what NASA satellites found up there at say 56,000 feet. Then compare 2003 with 2011 – both almost precisely the same around the -63 deg.C value. Here’s the link: http://discover.itsc.uah.edu/amsutemps/ Check all the records available (from 2002)and see how little variation there has been. Then tell me what would happen on Earth if it warmed up to, let’s say, -60 deg.C.
Say this loud and clear to every warmist you encounter: “The climate is subject to negative feedback. It is self-correcting. This means that there is no such thing as a ‘Tipping Point’ “.
The atmosphere shrank quite a bit over the past few years. I suspect this is related to the cloud deck change, sorry I don’t have a link, here is the full article from AGU 2010. One question that I have re: this article is the claim of the thermosphere cooling considerably, yet having a significant drop in density ~30% as well…does not compute to me, especially if altitude is lower.
Shrinking atmospheric layer linked to low levels of solar radiation
AGU Release No. 10–28
26 August 2010
For Immediate Release
WASHINGTON—Large changes in the Sun’s energy output may cause Earth’s outer atmosphere to contract, new research indicates. A study published today by the American Geophysical Union links a recent, temporary shrinking of a high atmospheric layer with a sharp drop in the Sun’s ultraviolet radiation levels.
The research indicates that the Sun’s magnetic cycle, which produces differing numbers of sunspots over an approximately 11-year cycle, may vary more than previously thought.
“Our work demonstrates that the solar cycle not only varies on the typical 11-year time scale, but also can vary from one solar minimum to another,” says lead author Stanley Solomon, a scientist at the National Center for Atmospheric Research’s High Altitude Observatory. “All solar minima are not equal.” Researchers from the University of Colorado at Boulder (CU) also contributed to the project.
The findings may have implications for orbiting satellites, as well as for the International Space Station. The fact that the layer in the upper atmosphere known as the thermosphere is shrunken and less dense means that satellites can more easily maintain their orbits. But it also indicates that space debris and other objects that pose hazards may persist longer in the thermosphere.
“With lower thermospheric density, our satellites will have a longer life in orbit,” says CU professor Thomas Woods, a co-author. “This is good news for those satellites that are actually operating, but it is also bad because of the thousands of non-operating objects remaining in space that could potentially have collisions with our working satellites.”
The Sun’s energy output declined to unusually low levels from 2007 to 2009, a particularly prolonged solar minimum during which there were virtually no sunspots or solar storms. During that same period of low solar activity, Earth’s thermosphere shrank more than at any time in the 43-year era of space exploration.
The thermosphere, which ranges in altitude from about 90 to 500 kilometers (55 to more than 300 miles), is a rarified layer of gas at the edge of space where the Sun’s radiation first makes contact with Earth’s atmosphere. It typically cools and becomes less dense during low solar activity. But the magnitude of the density change during the recent solar minimum appeared to be about 30 percent greater than would have been expected by low solar activity.
The study team used computer modeling to analyze two possible factors implicated in the mystery of the shrinking thermosphere. They simulated both the impacts of solar output and the role of carbon dioxide, a potent greenhouse gas that, according to past estimates, is reducing the density of the outer atmosphere by about 2 percent to 5 percent per decade.
Their work built on several recent studies. Earlier this year, a team of scientists from the Naval Research Laboratory and George Mason University, measuring changes in satellite drag, estimated that the density of the thermosphere declined from 2007–2009 to about 30 percent less than that observed during the previous solar minimum in 1996. Other studies by scientists at the University of Southern California and CU, using measurements from sub-orbital rocket flights and space-based instruments, have estimated that levels of extreme-ultraviolet radiation—a class of photons with extremely short wavelengths—dropped about 15 percent during the same period.
However, scientists remained uncertain whether the decline in extreme-ultraviolet radiation would be sufficient to have such a dramatic impact on the thermosphere, even when combined with the effects of carbon dioxide.
To answer this question, Solomon and his colleagues used a computer model to simulate how the Sun’s output during 1996 and 2008 would affect the temperature and density of the thermosphere. They also created two simulations of thermospheric conditions in 2008—one with a level that approximated actual carbon dioxide emissions and one with a fixed, lower level.
The results showed the thermosphere cooling in 2008 by 41 kelvins (about 74 degrees Fahrenheit) compared to 1996, with just 2 K attributable to the carbon dioxide increase. The results also showed the thermosphere’s density decreasing by 31 percent, with just 3 percent attributable to carbon dioxide. The results closely approximated the 30 percent reduction in density indicated by measurements of satellite drag.
“It is now clear that the record low temperature and density were primarily caused by unusually low levels of solar radiation at the extreme-ultraviolet level,” Solomon says.
Woods says the research indicates that the Sun could be going through a period of relatively low activity, similar to periods in the early 19th and 20th centuries. This could mean that solar output may remain at a low level for the near future.
“If it is indeed similar to certain patterns in the past, then we expect to have low solar cycles for the next 10 to 30 years,” Woods says.
The study, published in Geophysical Research Letters, was funded by NASA and by the National Science Foundation.
Doug Cotton says:
February 10, 2012 at 2:47 am
‘But the IPCC hangs its hat on a thing they inappropriately call the greenhouse effect – due to what they also inappropriately call “backradiation.” ‘
The “backradiation” paradigm is just an equivalent way of looking at the result in equilibrium. If you don’t like it, look at it the other more proper way, as atmospheric impedance to heat dissipation. Water cannot flow from a low point to a high point, either. Yet, a dam raises the water level upstream. You are arguing that it cannot, but I am certain that it can.
“So let’s keep to the topic I was talking about, shall we?”
Let’s not, because you are advancing a crackpot thesis: essentially that the atmosphere cannot retain heat. Atmospheric retention of heat, and consequent raising of temperature at the surface due to it, is a slam dunk. There is no doubt at all that the Earth’s surface is hotter than it would be without an atmosphere and, ignoring other processes, the addition of heat trapping gases to a homogenous unsaturated atmosphere would tend to heat it more.
BUT, I have imposed very specific conditions, here. The situation is complex. There are other processes occurring which cannot be ignored, as the IPCC wants to do. Feedback effects, e.g., from clouds, can mitigate the effect, and alter the characteristics. In addition, the atmosphere is not homogeneous and CO2 radiative emissions are nearly saturated.
Inhomogeneity and saturation mean that the partial derivative (sensitivity) of temperature with respect to added CO2 can be negative, i.e., adding CO2 can actually tend to cool, rather than heat, the surface. I believe that my little thought experiment above demonstrates that adding more CO2 to the Earth’s atmosphere should, in fact, reduce the amount needed to be radiated out by CH4 to establish equilibrium, and therefore the sensitivity of Earth’s surface temperature to additional CO2 is actually negative.
And, other negative feedback effects can (and almost certainly do) reduce the magnitude of the sensitivity in the closed loop, and alter the steady state conditions.
I am not carrying the IPCC’s water here. I am not defending their position in toto. I am very specifically stating that they have simplified the situation to the point that it no longer reflects reality. But, the fallacy does not disprove the premise. The greenhouse effect being wrong would invalidate the IPCC’s postion. But, the invalidity of the IPCC’s position does not prove that the greenhouse effect is nonexistent.
Bart says:
February 10, 2012 at 8:53 am
“There is no doubt at all that the Earth’s surface is hotter than it would be without an atmosphere “
__________________________________________________________
You are obviously unaware of the results of mathematical calculations by Claes Johnson (well-published Professor of Applied Mathematics) in his Computational Blackbody Radiation” which is linked and summarised on the ‘Radiation’ page of my site http://climate-change-theory.com .
There is no physical process whereby atmospheric impedance to heat dissipation can cause thermal energy to be transferred back to the surface, (or even the air we stand in) other than, to a negligible extent contained in precipitation. As Johnson and I have stated many times, radiation cannot transfer thermal energy from a cooler source to a significantly warmer surface of atmospheric layer.
I am not ruling out any accumulation of thermal energy in the atmosphere, but I am saying that such will not affect climate. If there had been any such accumulation, then it would surely show up in the tropopause – the temperature “valley” where temperatures stop declining and start to rise with increasing altitude. Check NASA satellite data at 56,000 feet for every year since 2002 on their site http://discover.itsc.uah.edu/amsutemps/ and you will see that it has been consistently around -63 deg.C every year with less than a degree of variation and certainly no rising trend.
The atmosphere does more in the way of cooling the Earth’s surface (by insulating it from solar radiation) and even the carbon dioxide actually also insulates and thus cools the surface. You can see how ineffective it is at keeping Antarctica warm. Surely the difference between the South Pole and the Equator shows that it is all about indicent solar raditaion levels. And you have only to consider that the Moon’s surface can go about 100 deg.C to realise that our atmosphere insulates us from solar heat. (I know it also goes below -150 deg.C on the Moon but that is partly to do with not having core heat like the Earth and also the long 13 day cooling off period in the Moon’s night.) http://www.universetoday.com/19623/temperature-of-the-moon/
The earth’s adiabatic lapse rate is primarily determined by the mass of air in the atmosphere and the relative humidity, both of which mankind has no control over. This rate sets a temperature trend line in the atmosphere. That trend is actually an extension of the trend from the core to the surface. If the atmospheric trend were to rise to a new equilibrium at the surface end for some reason, probably greater solar radiance due to orbital variations, or variations in cloud cover, then the whole temperature plot from the core would also have to rise at the surface end because thermal equilibrium will be maintained at the surface/atmosphere interface. It would take a huge amount of energy to fill the gap under the new sub-surface plot, wouldn’t it. So, for a start, we would be seeing net flow into the surface rather than out of it as is currently observed. I am not saying it could not happen, and it obviously does in long natural cyclic patterns, but I am saying it takes a long time.
So, I repeat that there is no mechanism whereby any warming of the atmosphere will then warm the surface. All surplus energy above the well-embedded temperature trend line will be simply radiated away. Only when the surface itself is warmed, by stronger solar insolation or even by variations in thermal energy generated under the surface, and only when a new equilibrium is established in the core to surface plot will be see a new equilibrium at a higher surface temperature. Processes like this appear to happen naturally in long term natural cycles beyond the control of man.
It has absolutely nothing to do with radiative feedback from WV or any atmospheric trace gases.
PS – Bart (and others)
We have seen here at WUWT that there has been a reduction in relative humidity this century which should indicate that there is no radiative feedback from water vapour having any positive effect. That in itself demonstrates what Prof Johnson is saying that any radiation from a cooler atmosphere cannot transfer thermal energy to the warmer surface or to any (significantly) warmer atmospheric layer. This does more than just negate any amplification of any carbon dioxide forcing: it also negates the possibility of any GHG forcing whatsoever, which is in accord with what Johnson has proved. If WV does not warm with “backradiation” neither will any GHG.
I have written in other posts explaining how thermal energy merely appears to transfer only from warm to cool. It does not actually itself travel at the speed of light. Only radiated energy does so. Radiated energy only gets converted back to thermal energy when it meets a target which responds appropriately and converts the radiated energy to thermal energy. For this to happen the peak frequency of that radiation has to be above the cut-off frequency for the target itself, as Johnson explains. If it is below cut-off, the radiation (if not already reflected) will be transmitted or scattered and no energy left behind in the target. The very fact that thermal energy only ever appears to go from warm to cold is fully explained by Johnson’s result and no other process. If it could go from cool to warm there would be no end to the process and infinite spontaneous adiabatic warming would be a theoretical possibility by just surrounding a small object with numerous cooler radiating bodies. Is there any evidence of waves from a radio broadcasting tower actually warming something nearby? Is there really any evidence of radiation from the atmosphere doing likewise? No.
If and only if there is conversion to thermal energy will there be any effect on the rate of warming or cooling of the target. So climate cannot be affected by radiation from the atmosphere.
Now, finally, there is considerable doubt that the capture of photons by carbon dioxide will necessarily lead to sharing of that energy among O2 and N2 molecules. These have different quantum energy steps for a start. Collisions may appear to transfer KE, but they in themselves can generate low amounts of radiation due to acceleration of electrons. What happens appears to depend very much on temperature also. If there is warming then there will be a greater propensity to radiate anyway. So, either radiation happens before any warming, or any warming causes more radiation. All radiation from the atmosphere eventually gets to space because the surface and warmer molecules lower down will not accept it.
Doug Cotton says:
February 10, 2012 at 1:55 pm
“There is no physical process whereby atmospheric impedance to heat dissipation can cause thermal energy to be transferred back to the surface…”
For the last time, the energy flux to the surface is coming from the Sun. The IR emitters in the atmosphere do not heat the surface, the Sun does.
The GHGs do not have to transfer thermal energy to the surface. They only have to impede the energy that gets there from leaving, because there is more coming in every infinitesimal unit of time.
The surface temperature is a result of retained energy from the Sun. The atmosphere also retains energy, and with more energy retained, the temperature increases. And, it will keep increasing until atmospheric radiation allows an equilibrium to be attained.
At that point, a steady state adiabatic lapse rate can be established. Without such a radiative heat sink high in the atmosphere, there can be no stable non-zero lapse rate.
In equilibrium, the incoming solar flux plus backradiation balance with the outgoing surface radiation. Only in that narrow sense can the backradiation be said to be heating the surface. But, it isn’t really. It’s just an equilibrium condition.
Kelvin Vaughan says:
February 10, 2012 at 3:09 am
The average global cloud height is linked to the average global temperature—generally, the higher the average cloud height, the higher the average surface temperature, and vice versa.
We are cooling down.
Yes, the cloud height is a proxy of the average strength of convection which itself is a proxy for the energy in the system. Less energy = cooler.
Doug Cotton says:
February 10, 2012 at 2:57 pm
“Is there any evidence of waves from a radio broadcasting tower actually warming something nearby?”
I have a little box in my kitchen which has a little radio broadcasting tower in the top. When I put food in the box, it gets hot.
The very cold temps at 400 mb the infamous level of trapping the IPCC is looking for, would also argue for lower cloud tops, at least over the last year. Interestingly enough.. the cool enso, then rapid drop off in mid trop temps and now the rapid drop off in the lower trop temps ( the air above the boundary layer would cool first) goes hand in hand with the idea that global temps respond to the large natural cycles ( in this case the turn of the PDO and the cool enso) than the fiction the AGW side is trying to push
Bart and others. Don’t joke with me about putting something on top of a radio wave generator. Try a bit to one side.
The atmosphere can violate physics? Whatever radiation meets the surface from the atmosphere, whatever the intensity or wavelength, if it came from a cooler source it cannot add thermal energy to the surface.
See section 3.9.3 regarding the Second Law of Thermodynamics applying to heat transfer by radiation.
http://arxiv.org/PS_cache/arxiv/pdf/0707/0707.1161v4.pdf
Prof Claes Johnson proves computationally how and why it applies. If he were incorrect there would be a violation of the law.
This paper also mentions on p.74 the role of the core heat in climate, something which I have written about long ago on the ‘Explanation’ page of http://climate-change-theory.com I am relieved to find a paper that mentions such.
Well, try a question mark after that: The atmosphere can violate physics? /sarc
Bart says:
February 10, 2012 at 3:06 pm
Doug Cotton says:
February 10, 2012 at 1:55 pm
“There is no physical process whereby atmospheric impedance to heat dissipation can cause thermal energy to be transferred back to the surface…”
For the last time, the energy flux to the surface is coming from the Sun. The IR emitters in the atmosphere do not heat the surface, the Sun does.
________________________________
I stand by my statement and I couldn’t agree more with yours in italic above.
So how does any thermal energy trapped up somewhere in the atmosphere (or slowed down in its inevitable exit to space) have any effect on what we call climate down here?
So at night how does radiative flux from the atmosphere add thermal energy to the surface in order to slow the rate of cooling? (Sorry, but we need to take the Sun out of the picture to focus on this nocturnal system.) Do try to remember that the Second Law of Thermodynamics also works at night.
Try reading p.74 at least from this peer-reviewed published paper. http://arxiv.org/PS_cache/arxiv/pdf/0707/0707.1161v4.pdf
You also said: They only have to impede the energy that gets there from leaving, because there is more coming in every infinitesimal unit of time.
The impeding will have no effect on climate as I said in the statement I stand by above.
Oh, and sorry, but the Sun doesn’t shine here in Sydney “in every infinitesimal unit of time.” I find things cool off at night, don’t you?, Back to about where they were the night before.
Funny how the temperature at 56,000 feet is still the same as it was a decade or so ago, namely about -63 deg.C. That must be having a huge effect on us all down here.
Bart says:
February 10, 2012 at 3:06 pm
“The IR emitters in the atmosphere do not heat the surface … Only in that narrow sense can the backradiation be said to be heating the surface. But, it isn’t really. It’s just an equilibrium condition.”
_____________________________________________
Make up your mind. EIther the radiation from the cold atmosphere is converted to thermal energy in the surface or it isn’t.. Which, my friend?
If it isn’t (which it isn’t because it’s scattered) then its effect energy-wise is exactly the same as being reflected and it can have absolutely no effect. It certainly cannot slow down other radiation or the rate of cooling of the surface in the evening or increase the rate of warming in the morning sunshine.
Now go and read what a proper published paper by German physicists has to say and I’d be happy to discuss any point in the paper – just quote section or page.
http://arxiv.org/PS_cache/arxiv/pdf/0707/0707.1161v4.pdf
“Unfortunately, there is no source in the literature, where the greenhouse effect is introduced
in harmony with the scientific standards of theoretical physics ”
.
“EIther the radiation from the cold atmosphere is converted to thermal energy in the surface or it isn’t.”
You’re just thinking about this all wrong, Doug. I think you have in mind a sort of pseudo-static situation where various entities are independently bombarding the surface with energy bundles, and the Earth is, in turn, sending them back out toward the sources. According to the 2nd law, the atmospheric particles, in this scenario, will receive back more radiation than they put in, so the net flow is outward.
That is entirely true. The net flow between the surface and the atmosphere is outward. But, all of the energy is coming from the Sun. It is coming in constantly on the day side of the planet. It is re-emitted up into the atmosphere, and some of it is re-emitted back down, and then the surface re-emits it back up again, and so on. Then net result is that more energy puddles near the surface, and so the temperature rises. But, the net flow between the surface and the atmosphere is still upward, so there is no 2nd law violation. What is left is a little larger pool of energy near the surface, and that raises the temperature.
On the night side, the net flux is still out, so there is no 2nd law violation. The only thing affected is the rate of thermal emission from the combined surface/atmosphere, which slows (not the speed of the photons, of course, but the number of emissions per unit of time which result in photons escaping the system), so the surface cools less quickly than it otherwise would have.
I don’t harbor much hope I am going to get through to you. But, in the off chance that I do, I want to point out to you how complex this really all is, which is widely unappreciated. Don’t bother reading beyond here if you are not interested.
————————————————————
All of this back-radiation and thermal energy accumulation is a positive feedback. A temperature rise causes atmospheric absorption by GHG gases, which reduces the rate of outward energy flow, which raises the surface temperature, which causes more atmospheric absorption, and so on it a self-reinforcing cycle. This will continue until the rate of surface emission outside the GHG bands of absorption plus the outward bound atmospheric emissions balances the incoming solar radiation flux.
It is exactly like my analogy of the dam and the floodgates. And, as I showed with that analogy, it is entirely possible for the addition of lower energy emitters like CO2 to cause the equilibrium temperature to go down rather than up. in fact, when you are in an equilibrium situation, as we are, in which a higher energy emitter like CH4 is producing significant emissions to balance everything out, then I believe it is even very likely that the addition of more CO2 would tend to lower the surface temperature.
There is an additional potential for a saturation effect to create more cooling. In that case, adding more CO2 would tend to broaden the peak at which absorption and subsequent radiation occurs. In my dam analogy, that would be like adding additional floodgates below the level of the previous ensemble.
SO, to sum it all up:
1) The GH effect is real
2) But, adding GH gases does not necessarily increase the surface temperature
3) In the case where there are higher energy emitters which are significantly stimulated, and/or the absorption/emittance distribution is broadened, it is quite likely that increasing the concentration will lead to cooling
4) Not discussed here, but additional feedbacks in the system (e.g., cloud dynamics) can suppress the GH effects and make any warming/cooling insignificant – this would be akin to having a spillway that circumvents the dam
Bart: You display a distinct lack of knowledge about radiation when you say “In the case where there are higher energy emitters which are significantly stimulated,.”
No spontaneous radiation from the atmosphere can have radiated energy high enough to deposit thermal energy in a warmer surface, as official explanations of the GHE speculate happens. There are several different official explanations I know, which just demonstrates the confusion, but the IPCC says backradiation leads to warming somehow.
Why are you wrong in the above statement? Because peak frequency is proportional to absolute temperature according to Wien’s Displacement Law and the energy of a photon is proportional to its frequency and thus to the temperature of the emitter. Below the mesopause the atmosphere is colder than the surface, so any photons it emits have lower energy than the photons being emitted by the surface. And if any heat were transferred it would be in breach of the Second Law. And if no heat is transferred, there is no greenhouse effect causing any warmer climate down here. It’s that simple.
It is not I who “has it all wrong.”
My belief and understanding are exactly in accord with the published physicists who wrote this paper and made this statement therein.
http://arxiv.org/PS_cache/arxiv/pdf/0707/0707.1161v4.pdf
“Unfortunately, there is no source in the literature, where the greenhouse effect is introduced in harmony with the scientific standards of theoretical physics.”.
So if you, Bart, disagree with anything in the 100+ pages therein, write and publish an official rebuttal, or try to find one – which I would love to see.
Bart you really put your foot in it here: “the net flux is still out, so there is no 2nd law violation” because the Second Law has nothing to do with net radiative flux. It has to do with heat transfer. The IPCC tries to say there is heat transfer into the surface (thus slowing the rate of cooling in the evening and increaing the rate of warming in the morning and the maximum temperature for the day), whilst all the time there is net flux out of the system. This does not make it OK to break the Second Law by transferring heat into the surface from a colder atmosphere, No transfer of heat inwards means no greenhouse effect.
(continued)
Just to clarify … Imagine three metal plates in parallel planes at equal separation in a vacuum.
1. The plate on the left is 100 cm^2 and is at 28 deg.C
2. The plate in the middle is 1 cm^2 and is at 30 deg.C
3. The plate on the right is 10 cm^2 and is 32 deg.C
(a) Net total radiative flux is left to right because the difference in surface areas dominates in S-B calculations.
.
(b) Heat flow is from right to left because of the temperature differences.
(c) The middle plate is not warmed by the cooler plate on the left despite the large flux.