Guest post by John Kehr from: The Inconvenient skeptic
There are many times when I am putting together articles that I need to compare the results of my research to the models of the theory of Anthropogenic Global Warming (AGW). In this manner I can contrast the results and predictions directly. This way I understand how the different views relate to each other.
Recently I was trying to find the total amount of energy (forcing) that the warmists claim CO2 is responsible for in the atmosphere. The reason I wanted this is because I have recently completed my full analysis of absorption and I wanted to compare my results to the warmist views. While this article is not about my results, it will focus on some interesting results that I found using their models. Because I was searching for the warmist views about energy I was using information from their sites (and citations of course). While that might seem strange, they generally have lots of good information there.
The starting point is the basic equation they use to determine the forcing caused by a change in CO2 concentration.
CO2 Forcing Equation
This equation provides the amount of energy in W/m2 that a difference in two CO2 concentrations should cause.
While looking for the total forcing of CO2 in the atmosphere, I found an interesting article on the Skeptical Science (SkS) site that had an answer to my question (citation). They state that the radiative flux caused by CO2 is 32 W/m2. I will use the information from that article several times. When I compare the energy calculated by the forcing equation using CO2 levels of 1 ppm and 390 ppm I get a result of 31.9 W/m2. So far things are looking consistent for the theory of AGW. Here is a chart of the forcing from 1 ppm to over 1000 ppm.
Proposed Model of CO2 Forcing
The next step is to determine how much warming this energy causes. For this I use the next important equation that the AGW model uses. That is the climate sensitivity.
Climate Sensitivity: Warming caused by Forcing
Again I found lots of discussion and references at the SkS website (Hansen et al. 2006) where they provide their views about climate sensitivity. This equation is straightforward and simple to decipher. They generally calculate it by looking at a period of time with a temperature change and then estimate the change in forcing. For example if increasing CO2 caused a forcing of 2 W/m2 and the observed temperature change was 5 °C, then the climate sensitivity would simply be 2.5 °C /(W/m2).
One thing to be aware of is that the sensitivity is usually not shown directly. Most warmist publications display the results in terms of temperature change that will happen as a result of forcing. For example the most commonly used quantity for climate sensitivity is 3.0 °C for a doubling of CO2. To determine the climate sensitivity they are using it is simply:
λ = (3°C / 3.7 W/m2 ) = 0.81 °C/(W/m2)
I am going to use the direct climate sensitivity instead of the temperature effect that a forcing will cause. This will make my numbers look a little different, but here is the conversion.
Proposed Range of Climate Sensitivity
When comparing climate sensitivity it is very important to know exactly which form is being used. I will be using the actual climate sensitivity instead of the CO2 doubling form. The best way to check is to look at the units being used.
The most common estimate is the 0.81 °C/(W/m2). That is what corresponds to the 3 °C temperature increase for a doubling of CO2. The full range is what I have shown in the table. Some estimates do go a little higher or lower, but the 0.43-1.13 °C/(W/m2) is the most widely accepted range.
SkS puts the climate sensitivity at the 0.81-0.92 °C/(W/m2). I am going to use the 0.81 °C/(W/m2) as the default value for the warmists as it is the most commonly used value.
So far all of this seems perfectly reasonable and hopefully acceptable. This is also where the wheels start to come off.
I decided to look at another method to determine the climate sensitivity. I am troubled by the method normally used because it is very hard to know the exact forcing and cause of the temperature change. So I decided to use what should be a less controversial method, but somehow I doubt it works out that way.
I decided to use the total Greenhouse Effect (as the ΔT) and then the energies involved. The total Greenhouse Effect is perhaps the least controversial aspect of the Global Warming debate. I will use the normally accepted value of the Greenhouse Effect as 30 °C.
Now by using the climate sensitivity value it is possible to compare what portions of the Greenhouse Effect (GHE) are caused by different components. Since the accepted forcing value for CO2 is accepted as 32 W/m2 it is now possible to determine the total impact that CO2 has on the total GHE.
ΔT = (0.81°C/(W/m2)) * 32 (W/m2) = 25.9 °C
While that might not immediately seem unreasonable. The entire stated effect of the GHE is 30 °C. So according to the accepted climate sensitivity and CO2 forcing equations, CO2 accounts for 86% of the total GHE.
So all other factors in the Earth’s climate account for 14% of the GHE and CO2 by itself accounts for the other 86%. This can also be compared to the number of CO2 doublings that take place from 1 ppm to 390 ppm. That is roughly 8.6 CO2 doublings (1,2,4,8,16,32,64,128,256,390 ppm). Using 8.6 doublings from 1 ppm gives 25.8 °C. So their model is coherent, but saying that CO2 causes 86% of the GHE is extremely incorrect.
This means that the methods being used for determining temperature change based on forcing and climate sensitivity are flawed. Any result that puts CO2 at 86% of the GHE is wrong. Earlier I showed that the forcing model and the accepted total forcing have a good match. That would indicate that the problem is with (at least partially) the estimated climate sensitivity.
So I worked backwards. Assuming that the total temperature change caused by the GHE is 30 °C and then the total energy inputs are the total forcing. The total GHE is not very controversial. Very few people will argue that the Earth is not warmer as a result of the atmosphere. Without the atmosphere the Earth would be around -15 °C and with the atmosphere it is currently about 15 °C. That 30 °C difference is caused by the insulative effect caused by the atmosphere.
That leaves forcing as the problem in determining the correct climate sensitivity. The same article that stated CO2 as 32 W/m2 also stated that water vapor causes a forcing of 75 W/m2. If I assume that water vapor and CO2 are the ONLY factors I get a total forcing of 107 W/m2. This would indicate:
λ(30%) = (30°C /107W/m2) = 0.28 °C/(W/m2)
Already using very poor assumptions the climate sensitivity is already much lower (by almost 3x) than the accepted value. This still puts CO2 at 30% of the total GHE, so even this estimate for climate sensitivity is still too high.
The normally discussed range of CO2 effect on the GHE is 9-26%. Assuming that the 32 W/m2 remains accurate for the forcing magnitude of CO2 results in climate sensitivities of:
λ (9%) = (30°C / 356 W/m2 ) = 0.08 °C / (W/m2 )
λ (26%) = (30°C / 123 W/m2 ) = 0.24 °C / (W/m2 )
At 9% of the GHE the climate sensitivity must be 10x lower than what is currently accepted. There is one more possible scenario that I want to cover.
If I look at the Radiation Budget (Kiehl, Trenberth 1997) I get a total forcing from the surface to the atmosphere of 452 W/m2. That would include the energy from evaporation, convection and radiative transfer and subtracting out the open window of 40 W/m2. If I use the 32 W/m2 for CO2 with that total energy then CO2 accounts for 7% of the total GHE. Then the climate sensitivity is:
λ (total energy) = (30°C / 452 W/m2 ) = 0.066 °C / (W/m2 )
That is what the real lower limit of the climate sensitivity is. The flaw in the estimates for climate sensitivity is the assumption that all temperature change is caused by the greenhouse gas forcing. If the climate was as sensitive as the much higher estimates currently in use are, the Earth would be a very unstable place as small changes in energy would cause large changes in temperature.
Using the total GHE determined climate sensitivities, here are the CO2 doubling effects on the climate.
GHE Determined Climate Sensitivities
What this shows is that trying to determine the climate sensitivity from a change in measured temperature and then assuming it was caused by a particular forcing is incompatible from the determination of climate sensitivity from the actual GHE. In choosing between methods it is the GHE that is a known quantity. Since the measurements have been done to determine the individual parts of the GHE, that seems to be a much more reliable method than “assuming” that a particular forcing caused a certain change in temperature.
The IPCC and the general AGW method of determining climate sensitivity is about an order of magnitude different than the method of using the total GHE and then calculating the components. This is a significant scientific disparity.
The difference the climate sensitivity makes to the temperature projections based on increasing CO2 concentrations are significant. Assuming the same CO2 forcing while using the different climate sensitivity values results in the following effects of CO2 on the global temperatures.
Red: The AGW accepted climate sensitivity of 0.81 (3C for doubling) Green: Climate sensitivity of 0.28 (1C for doubling) Blue: Climate sensitivity of 0.066 (0.24C for doubling)
The total GHE of 30 °C is incompatible with the currently accepted IPCC values of climate sensitivity and CO2 forcing. In order for the GHE to be compatible, the total effect of the greenhouse would have to be closer to 100 °C which would result in a global temperature of ~85 °C. This strong overstatement of the climate sensitivity substantially weakens the idea that CO2 could cause measurable change in the Earth’s climate, much less the type of danger that is often being stated.
This does not mean that CO2 is not a significant portion of the Earth’s greenhouse, but it does limit the role that it plays in the total GHE. The climate sensitivity is what prevents the sum of the parts from being greater than the whole and the sum of the parts cannot be greater than the total observed GHE. If the current estimates of CO2 forcing and climate sensitivity do not fit within the parameters of the total GHE effect, those estimates must be incorrect.
George E. Smith says: October 25, 2010 at 9:22 am
So regardless of what H2O does with LWIR (or irregardless, as the case may be); MORE H2O in the atmopshere in ANY and ALL phases ALWAYS reduces the total solar energy that is absorbed by this planet; just as a lower TSI would; and over time that must lead to a cooler planet.
So just where climatists get off claiming H2O and Clouds as a positive feedback warming mechanism; is beyond me.
I’m not a climatologist, but I don’t think this is quite right.
Looking just at water vapor (NOT droplets as in clouds), the water absorbs some IR radiation but very little visible light. (See this previous post here: http://wattsupwiththat.com/2008/06/21/a-window-on-water-vapor-and-planetary-temperature-part-2/ for a graph)
So the incoming solar radiation is indeed reduced — but only a tiny bit since only a tiny bit of the energy is IR. So instead of ~170 W/m^2 of sunlight absorbed at the surface, maybe it is 169 W/m^2 or 165 W/m^2. That by itself would indeed cool the surface.
But that is only part of the situation. The earth is trying to radiate that energy back into space in the form of IR. But now the H2O in the atmosphere blocks a great deal of the IR, leading to a warming of the H2O molecules and hence a warming of the air. The more H2O, the more IR gets blocked, and the more the atmosphere warms, and the more it can radiate IR back to the earth. This IR energy back outweighs the little bit of sunlight that is blocked from reaching the earth. (And of course, this is the whole idea of the greenhouse effect.)
So the net effect is indeed a positive feedback from the water vapor. (I agree that water droplets and clouds would indeed be a negative feedback. )
DesertYote says:
October 25, 2010 at 12:01 pm
richard telford says:
October 25, 2010 at 7:51 am
There was a similar post to this on WUWT a month or two back. Not surprisingly they share the same flaw.
The greenhouse effect of 30C is for a planet with an albedo of 0.3. The earth would not be cooler by more than 30C if the atmosphere was not radiatively active because the albedo would increase because of increased snow and ice cover.
#
What does a state change discontinuity at boundary have to do with the anything?
————————
@DesertYote: It’s the difference between walking on water and walking in water.
@Telford: I assume that he meant “all things being equal”, as in equal albedo, the earth would be 30C colder. Since it’s an analysis of formulas, that seems reasonable. Is this going to be a problem for you?
@ur momisugly Dave Springer:
October 25, 2010 at 12:20 pm
I agree with your point that any additional co2 being just a increased insurance against ice if it affects anything at all. It is cold we need to fear.
I am curious where you got the 4ºC average temperature for the oceans. If that is actual then by 29%x42ºC + 71%x4ºC = 15ºC it would take the land masses to have an average of some 42ºC to average out at 15ºC, way too high. I have always been a bit suspicious of some of these figures tossed about by IPCC and if the four degrees is correct then their fifteen degree average seems clearly wrong. Was it via ARGO?
John
I read your post once. Understood it well but on the assumption that George E Smith did not make. I respect George a great deal but in this instance I think he mis-interpreted your objectives for the post. I could be wrong of course. I think you were merely demonstrating the flaws in the AGW analyses current available. Telford always pipes up with a strawman and so I ignore George on the other hand is always detailed and cannot be ignored. Your post for me was meant to be simplistic and for that it works.
Tim F says:
October 25, 2010 at 12:55 pm
You may have missed the point. It is the 3 phases of H²o that are important. All 3.
I think the “interesting article on the Skeptical Science (SkS)” that you mentioned also suggests the problem with your analysis — feedback.
The climate sensitivity to CO2 is the affect on global temperatures due to a change in CO2 and the resulting feedback and changes in the earth.
You said “For example if increasing CO2 caused a forcing of 2 W/m2 and the observed temperature change was 5 °C, then the climate sensitivity would simply be 2.5 °C /(W/m2).” But your analysis then goes on to assume that ONLY CO2 plays a role.
The very article from SkS that you looked at has a big section titled “Water Vapour as a positive feedback”. In that section, they specifically state “How much does water vapour amplify CO2 warming? Without any feedbacks, a doubling of CO2 would warm the globe around 1°C. Taken on its own, water vapour feedback roughly doubles the amount of CO2 warming. When other feedbacks are included (eg – loss of albedo due to melting ice), the total warming from a doubling of CO2 is around 3°C (Held 2000).”
The finer points of the magnitudes of the feedback are certainly debatable, but for you analysis, you need to consider that feedback! CO2 is only ~1/3 as important as you suggest, which would suddenly throw all your calculations off and make everything much more reasonable.
Well John, you’ve just proved mathematically what a recent warmist paper concluded from GCM’s: water vapour is an insignificant GHG – it’s all down to CO2.
Interesting.
Something on this issue is evolving.
Until last week I had frequent headache. Global temperatures in 1850 are terrible.
At the moment everything is very simple. It’s on “agenda” … new beginning in 1959 for the future.
The mathematics of AGW is simple;
Delta (T) = {[a.ln C / Co] + k [0.35 PDO + 0.87 AAO + pi AMO -sin (Niño 3.4) + 1 / 3 AMO + e (SOI)^4]} * 0 + 2.5 ° C.
= 2,5ºC
I love this blog. I have deep respect for all.
Anyone who read http://www.surfacestations.org/ and add something with 0.2 º C for UHI … … .. Nothing happens to the planet…. (they want to save).
We have satellites.
Dr Roy (phd), sorry.
At launch,
http://www.spacestations.org .xxx
That real funny Vince, if you would have carefully read the article it mathematically proved the exact opposite to your comment, CO2 has little significance and it’s all about water. Guess that kind of washed out your point, sorry bout that.
Temperatures follow LOD (Length of the Day), LOD follows gravity acceleration, gravity acceleration follows electromagnetic environment.
http://www.scribd.com/doc/40075530/Unified-Field-Explained-1
http://www.scribd.com/doc/39961403/Eccentricity-Field
This has been a fascinating read – orignal posting and many of the comments.
I must say I remain troubled by the thought that anyone could assign a “Climate Sensitivity” to a single trace gas in a rather complex heat engine. It seems to me you would need to remove the effect of clouds, the effects of convection, and the impacts of all other overlapping GHGs (mainly water) and then you could determine a sensitivity to warming – but what good is it since it doesn’t describe the real system?
The real system pushes back no matter what curve you assign to CO2 – we know this because we are alive today, and we know there was much more CO2 in the atmosphere in the past ages. Had CO2 been the controlling influenece it would have cooked the Earth.
Also, why is the Earth warming? Until we know why and how natural warming occurs we cannot hope to know why and how unnatural warming occurs. AGW seems to want to ignore natual warming and assigns it as a constant, but it is anything but.
stephen richards says: October 25, 2010 at 1:27 pm
You may have missed the point. It is the 3 phases of H²o that are important. All 3.
No, I didn’t miss that.
The claim was “MORE H2O in the atmosphere in ANY and ALL phases … must lead to a cooler planet.” My point was that more H2O in the atmosphere in the specific phase of water vapor increases the net downward radiation — it blocks a tiny bit of solar radiation from reaching the earth, but it more than makes up for that by radiating IR downward. Thus, adding more H2O vapor must lead to a WARMER planet. As we know, H2O is the major greenhouse gas, so we know that H2O is the single most important gas in keeping the earth ~30 C warmer that it would be without any GHG’s.
I do agree that adding more LIQUID or SOLID H2O to the atmosphere (in the form of clouds) will lead to a cooler planet do to changes in albedo. In fact, I did mention this in my previous post (but I apologize for overlooking the 3rd phase — clouds can indeed contain solid water, not just liquid droplets). I don’t have the personal expertise to argue whether the warming or cooling is a greater affect — I’ll leave that question to others.
wayne says: October 25, 2010 at 1:01 pm
I am curious where you got the 4ºC average temperature for the oceans. If that is actual then by 29%x42ºC + 71%x4ºC = 15ºC it would take the land masses to have an average of some 42ºC to average out at 15ºC, way too high.
4 C would be the average temperature thru the whole depth of the ocean. The surface itself would still be around 15 C. And that 15 C surface temperature is all that matters for IR radiation to the atmosphere. (Kinda like rocks deeper down are much hotter, but that doesn’t affect the IR radiation either.)
“It seems that the choice of wording whether to call water vapor and clouds in the atmosphere forcing or feedback is dependent on what is wanted to be proven.”
Perhaps, but it would certainly explain why they did their calculations the way they did. What isn’t explained is why the troposphere isn’t warming at the modeled rate of 1.4 times that of the surface.
Remote Sensing 2010, 2, 2148-2169; What Do Observational Datasets Say about Modeled Tropospheric Temperature Trends since 1979 John R. Christy 1,*, Benjamin Herman 2, Roger Pielke, Sr. 3, Philip Klotzbach 4, Richard T. McNider 1, Justin J. Hnilo 1, Roy W. Spencer 1, Thomas Chase 3 and David Douglass
There is a problem in the argument here that should be pointed out. The forcing due to CO_2 cannot be exactly logarithmic, only approximately so in the region of concentrations not too different from now. In particular this relationship must break down for very low concentrations because otherwise as CO_2 concentration dropped to zero, the forcing would become negative and temperature would go towards negative infinity. You therefore can’t use the logarithmic model to calculate total forcing because that would involve using it in the low concentration region where it is invalid.
You indeed saw this when you discovered that using zero as your lower limit for CO_2 concentration would give nonsense. Your solution was to use 1ppm as your lower number for CO_2 concentration which gave you a total forcing of 31.9 W/m^2 which you stated gave you confidence because it was close to the 32 W/m^2 claimed in the literature for the total radiative forcing for CO_2.
But 1ppm is a completely arbitrary number. It happens to look nice in base 10. But the universe doesn’t see anything special about this concentration. If you had used 2ppm or 0.5ppm instead for your lower limit you would have calculated total forcings of 37.25 and 26.55 respectively.
You see how sensitive the figure is to the choice of this completely arbitrary lower limit. Remember that the only reason for that lower limit to be there at all is because you can’t use zero as it would give a nonsense result of infinity. Observe that the bulk of the effect is happening in this very low concentration region where the logarithmic model has broken down and where there is no reason for us to believe that any of the numbers it generates have any relationship to reality.
I can only hope that the 32 W/m^2 number for total CO_2 forcing you quote from the literature was NOT computed in this way and that the close agreement in number is purely a coincidence. Because if this is how total CO_2 forcing was actually computed in the literature then that is a scientific scandal as the calculation is a complete nonsense and should never have passed peer review.
wayne says:
October 25, 2010 at 1:45 pm
Wayne, I think Vince very firmly has his tongue in his cheek there.
“”” Tim Folkerts says:
October 25, 2010 at 1:53 pm
stephen richards says: October 25, 2010 at 1:27 pm
You may have missed the point. It is the 3 phases of H²o that are important. All 3.
No, I didn’t miss that.
The claim was “MORE H2O in the atmosphere in ANY and ALL phases … must lead to a cooler planet.” My point was that more H2O in the atmosphere in the specific phase of water vapor increases the net downward radiation — it blocks a tiny bit of solar radiation from reaching the earth, but it more than makes up for that by radiating IR downward. Thus, adding more H2O vapor must lead to a WARMER planet. As we know, H2O is the major greenhouse gas, so we know that H2O is the single most important gas in keeping the earth ~30 C warmer that it would be without any GHG’s. “””
Well Tim the polite response to that statement is that it is nonsense. The absorption of solar spectrum energy by H2O vapor in the atmosphere commences at about 750 nm wavelength in the red portion of the spectrum, and then therre are a number of H2O absorption bands that occur out to the 4.0 micron region. Teh solar spectrum contains about 45% of its total energy beyond 750 microns, and only 1% beyond 4 microns; so there is 44% of the total solar energy in that range; and water vapor bands might actually acount for about half of that. Which is why the extra-terrestrial TSI of 1366 W/m^2 gets attenuated to a clear sky air mass one level of about 1,000 W/m^2.
So your characterization of the H2O vapor “blockage” as being “tiny”; is simply not an accurate depiction; it is one of the largest solar spectrum modifications caused by the atmosphere. Solar spectrum energy mostly goes deep into the oceans which reflect only2-3% of sunlight; and the part of the earth which is mostly oceans is in the tropics where most of the solar energy arrives.
True; that absorption by the the H2O in the atmosphere does warm the atmosphere; in fact it is one of the major warming influences; and that results in long wave Ir radiation in an isotropic pattern so only half of that radiative LWIR energy comes down to the surface. The other half goes upwards to space; so there is a net energy loss to the surface of about 1/2 of the amount that H2O vapor absorbs from the solar input. Reducing the total amount of solar energy that reaches the earth surface ALWAYS results in it getting cooler.; that can be seen instantly in a partial eclipse of thes un; or standing in the shadow zone of a cloud. There is no H2O vapor, liquid or solid phase phenomenon anywhere in the atmopshere where an increase in water results in an increase in the ground level solar energy.
Earth to Tim ! This planet has almost no other external energy input besides solar spectrum electromagnetic radiation from the sun; sunlight. Any reduction in sunlight for time scales of climate significance must result in a cooler earth.
Now to your downwelling LWIR.
Apart from direct atmospheric heating from absorption of solar energy, you have conductive and convective heating directly from the surface; and you also have some LWIR thermal emission (radiation) from the warmed surface. That energy was already part of the soalr input energy that warmed the surface in the first place; so it is nOT a new source of energy; it is old energy that has been thermally degraded by shifting from the 0.5 micrn centered solar spectrum to the 10.1 micron centered earth emission spectrum corresponding to a 288 K mean surface Temperature, and though it was of the order of 1,000 W/m^2 (max) when it entered; it is now only 390 W/m^2 qaas it proceeds upards and some of it is captured by the various GHGs including H2O; and that too warms the ATMOSPHERE by collision thermalization. That warm atmospehre in turn radiates isotropically in a thermal spectrum commensuratew ith the atmospheric Temeprature; just as before with the solar heating; and once again, only halkf of that emission can return to the surface; and that too is energy that has already been accounted for as part of the incoming soalr energy.
To the extent that solar energy input is curtailed by H2O absorption or cloud albedo reflection plus absorption, the ground must cool, and the amount of outgoing LWIR radiation to heat the atmospehre must also decline; as will the amount of secondary LWIR emission from the atmospehre that reurns to the surface.
Downward radiation from the atmosphere is in the 5-80 micron spectral range (98% of it); rather than the 20 times shorter 0.5 to 4.0 micron range of the original solar spectrum energy. That spectral shift has a major consequence; instead of penetrating to the deep oceans (tens to hundreds of metres), as solar energy does, the LWIR makes it all the way through the top 50 microns of the water surface (2/1000ths of an inch); which is five times the 1/e attenuation depth of 10 microns and accounts for 99% of the enrgy absorbed.
That energy absorbed in just the surface layer; reults in very localised heating of the surface and prompt evaporation of H2O; whcih then transports massive amounts of latent heat of vaporization into the atmosphere which convects to the upper atmosphere where it is deposited by condensation; and possibly freezing; about 545 cal per gram plus another 80 if it freezes..
So very little of the downward LWIR energy remains in the oceans; most of it returns quickly to the atmospehre in a massive heat transport to higher altitudes (moist air is lighter than dry air.
How you make a total net warming if you have more H2O in any phases, let alone all three is quite beyond me.
There is no other significant energy input to the earth (from outside) besides SUNLIGHT. H2O in ANY form ANYWHERE in the atmospehre ALWAYS reduces the ground level sunlight; there are NO EXCEPTIONS TO THIS RULE.
Ultimately, it is the total solar energy that EARTH ABSORBS that determnines its Temperature over climate times scales.=; and H2O ALWAYS reduces that.
“”””” Tim F says:
October 25, 2010 at 12:55 pm
George E. Smith says: October 25, 2010 at 9:22 am
So regardless of what H2O does with LWIR (or irregardless, as the case may be); MORE H2O in the atmopshere in ANY and ALL phases ALWAYS reduces the total solar energy that is absorbed by this planet; just as a lower TSI would; and over time that must lead to a cooler planet.
So just where climatists get off claiming H2O and Clouds as a positive feedback warming mechanism; is beyond me.
I’m not a climatologist, but I don’t think this is quite right.
Looking just at water vapor (NOT droplets as in clouds), the water absorbs some IR radiation but very little visible light. (See this previous post here: http://wattsupwiththat.com/2008/06/21/a-window-on-water-vapor-and-planetary-temperature-part-2/ for a graph) “””””
Tim you need to aquaint yourself with any of the standard widely available graphs of the Solar Spectrum, outside of the earth’s atmospehre hwere it fairly closely approximates a Black body Radiation curve corresponding to about a 5800 K BB Temperature. It show that about 98% of that energy lies between about 250 nm in the UV and 4.0 microns; with the remaining as 1% left over at each end. Such graphs often have superimposed on them the actual ground level (air Mass once) spectrum; that shows the amounts of that energy taken out by primarily O2, O3, and H2O, in the case of H2O which absorbs in the visible and near IR perhaps 20% of the total solar energy is capture by water VAPOR (clear sky) clouds are an additionqal loss over and above that.
I can’td raw those graphs with my keyboard so go to wikipedia or some science source and find them.
ONE THING THAT ANTHONY COULD DO TO ASSIST HERE IS PUT THOSE SOLAR SPECTRUM GRAPHS ON THE SIDE WITH HIS OTHER CLIMATE GOODIES SO THAT EVERYBODY HAS THOSE CURVES ENGRAVED ON THEIR FOREHEAD.
You can’t talk sensibly about the physics of climate if you don’t ahve a mental picture of the solar spectrum in outer space, and at the earth surface in front of you at all times; then a 300 K (or 288 K) thermal BB spectrum corresponding to surface emission would help too.
It takes far too many words to describe the general characteristics of Black Body radiators and absorbers; and anybody who doesn’t think the earth is near black body over most of its surface (the deep oceans) just hasn’t thought about it. If it wasn’t for the blue scattering of sunlight in the atmospehre; the earth would look MOSTLY BLACK from outer space; the oceans are not green or blue; they are black (deep oceans) 97-98% goes in and never comes out; only 2% is reflected at normal incidence, and about 3% over the range of sun angles and wave tilts.
Ian,
The cited reference is where the 32 W/m2 came from which is based on empirical data. I played around with the lower numbers as you mentioned and got comparable results. I am assuming that the equation was calibrated to about 1 ppm which is why using it worked in the manner that it did.
As for various comments asking why the Earth is warming.. The Earth is always changing temperature. It generally has a long term (1,000 year+) trend, but in the short term (<200 years) it is highly variable.
All paleoclimate data shows that type of variation. Except perhaps tree ring data.
“Without the atmosphere the Earth would be around -15 °C and with the atmosphere it is currently about 15 °C. That 30 °C difference is caused by the insulative effect caused by the atmosphere.”
It would be helpful to me if you clarified what you mean by the Earth being 15 °C. I always figured that that number was just the earth’s surface *air* temperature (at sea level). Air temperature, of course, is the temperature that is most easily and commonly measured but wouldn’t the Earths true temperature (near the surface) be lower if you took ocean temperatures into consideration?
“”” jorgekafkazar says:
October 25, 2010 at 9:52 am
George E. Smith says: “…Try drawing a STRAIGHT LINE between the 315 and 390 ppm points on your two graphs; and now try to sell me that the scattered data better fits the log curves than it does the straight line linear curves…”
A straight line will approximate the curve for small increments of CO² concentration. This does not disprove the logarithmic nature of the overall correlation. “””
Perhaps I didn’t make myself clear.
The idea is to take John’s logarithmic curves; then add the the 315 to 390 ppm straight line segments I suggested; then superpose the actual 52 year observed Mauna Loa CO2 values, along with your favorite mean Global Temperature (anomaly) graph; either GISStemp, HADCrut, RSS or UAH values; and then propose an argument as to why the data supports the logartihmic cuves rather than the Linear curves. You will find the data supports neither the straight line nor the logarithmic models; not is there any other continuous mathematical function you could propose (with no more than 52 arbitreary parameters); which would fit the data in any cause and effect believable way; and I will allow you to propose any tiem offset between the CO2 values, and the Temeprature values (in either direction) in order to improve your fit to the data.
Have at it.
By the way; I AM NOT knocking John’s essay or analysis; I haven’t fully digested it yet. I’m just pointing out from an initial scan; that it assumes a result that is “not in evidence” as the lawyers would say; namely a logarithmic relationship between mean earth surface Temperature, and the log (base two) of the CO2 amount. As in:-
T2 -T1 = (cs) log2(CO2,2/CO2,1) or some facsimile of such an equation. if the notation of that equation is not self evident; then ask a friend to explain it to you.
And that unprovable logarithmic relationship is the central tenet of climate science; it is to climate science what the velocity of light or the rest mass of a proton is to ordinary Physics; and it appears to be known; according to the IPCC to the startling accuracy of =/- 50%, whcih gives a 3:1 range form 1.5 deg C to 4.5 deg C per doubling.
And Dr Judith Curry; in her recent Scientific American interview allows that it could be between 1 and 10, rather than 1.5 to 4.5.
Not my idea of settled science.
By the way, I wish people would stop assigning significant albedo contribution to snow and ice cover (mostly in te polar regions) rather than to cloud cover which averages about 61% on earth (cloud cover, not albedo)
There is a very good reason why there is snow and ice at the poles. THERE’S VERY LITTLE SOLAR IRRADIANCE THERE. So regardless of the reflectance of snow and ice; which isn’t all that great except for very fresh snow; not much solar energy is reflected from there because there isn’t much to begin with.
Yes some like to point out that in summer you get sun 24 hours a day; but it is spread out over a huge surface area because of the obliquity; so it is a small portion of earth’s albedo.
So if clouds were eliminated by removal of H2O from the atmosphere the albedo would most certainly go down drastically; it won’t go up. Yes if it got colder in mid latitudes you’d get more snow in wintertime, which would for a while have more albedo contribution; but the clouds that precipitate that snow would have a bigger albedo effect. Snow more than 72 hours old is not very reflective; because of surface melting, which makes it optically transparent (at solar spectrum wavelengths), and the sunlight once it getsinto the melted snow structure gets trapped in ther by optical Total Internal Reflection. You can wiki that for yourselves to get an explanation; I should not have to explain Total Internal Reflection to anyone with more than an 8th grade science education. (yes I DID learn it before the equivalent of 8th grade.) In those days; you were supposed to learn stuff in school; rather than just feel good about yourself. earth’s clouds are far and away the major source of its albedo; not snow and ice.
Tim Folkerts
“(Kinda like rocks deeper down are much hotter, but that doesn’t affect the IR radiation either.)”
It would be nice if you could expand on that sentence. I have things figured differently. The presence of heat in rocks deeper down and coming upward from internal heat sources makes the cold pool of the deep ocean more worthy of consideration. To me it seems that some of earths heat as it exists on the surface must be continually extracted from the depths by some ocean circulation process. Just guessing I would think polar oceans must be sinking cold water. If so I would say that the cold temperatures of the deep ocean do indeed come from the surface and therefore those temperatures would need to factor into average surface temperature calculation.
Couldn’t you derive a firm sensitivity figure from using the amount of forcing the Sun provides to a point on the day side of Earth, and comparing it to the lack of forcing on the night side of Earth? dT/dF? If you can do it this way, the figure is quite low. If not, can someone explain why not?
Hmm, not sure my point was clear. I mean take the average change in temperature, and divide that by the change in forcing from the sun from maximum exposure to the sun to minimum exposure to the sun. Still not sure I am being clear, I hope so.