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.
Another nail, and a rather large one at that, through the heart of the walking corpse of AGW.
I enjoyed Max H. humorous comment above.
How do we get the politicians or their aides to read so many posts that forensically destroy the theories and assumptions of the climate mainstream?
I have a problem with the formula for climate sensitivity. How can one simply divide the change in temperature by the change in forcing without including the element of time? When you put a pot of cold water on the stove, it doesn’t get warm immediately – you have to wait until it reaches equilibrium. Am I to understand that the warmers believe that adding CO2 to the atmosphere produces an instant increase in temperature? If not, what time constant do they assume?
Well John, Let’s take a look at your final graph(s); specifically the ones with 3 deg C per doubling, and the one for 1 deg C per doubling. Those hapen to be within the IPCC 3:1 fudge factor range.
Well their numbers would be 4.5 deg C per doubling and 1.5 deg C per doubling; but it makes no difference.
You have plotted your curves for (near) zero to 800 ppm. But we have actual real experimental credible values that go from 315 ppm to 390 ppm for the Mauna Loa Record.
That is a ratio of 1.238. The cube of that is 1.899; slightly less than 2.0 while the 4th power is 2.350, so one would guess that 1.238 is close to 30% of one doubling. (i’m too lazy to do the real log calculation).
So for all of the credible non proxy global record of CO2 concentration since 1957/8, the IGY year we have data suggesting 30% of one doubling has occurred.
So if I take your graph and imagine your numbers were for 4.5 and 1.5 deg rather than 3 and 1, and now I scatter a bunch of observed data points; at least 52 of them for the elapsed years, in between 315 and 390 ppm and maybe centered about the middle between your two graphs but extending out to them as plausible upper and lower probably values; so I have that space shot full of at least 52 holes in a “Scatter Plot”; and the characteristics of that scatter plot of real observed data are such that your upper curve (3 deg>ersatz 4.5) and your lower curve (1 deg > ersatz 1.5) are pausible fits to that scattered data.
So there is the real data posted on top of your (and the whole house of climatists) theory of “Climate Sensitivity”.
So my question is simple:- Where do you collectively get the gall to claim that despite such a scattered data picture (of 52 spots) you know that the best fit line to that data, is in fact a logarithmic curve.
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.
I put it to you that your graphical curves, and the known Mauna Loa data provide NO EVIDENCE whatsoever, that in fact Temperature is related to log of CO2 abundance.
As a follow up experiment; you could take the often reported Temperature and CO2 proxy data for 600 million years dating back to the preCambrian; and encompassing Temperatures from +12 deg C to + 22 deg C, and CO2 values ranging from aorund 7000 ppm down to around 200 or so, meaning about 5 inverse doublings; and now repeat the above data plot but now over five doublings instead of 0.3 of one doubling. Try to justify your log model with that set of data.
Well i’m sure that won’t work either; neither one of those data sets will convince anyone that the relationship is in fact logarithmic.
So let’s try the theoretical approach. Styarting from basic laws of Physics; maybe we can prove that the relationship is logarithmic.
Well we know that the physics of CO2 greenhouse effect starts with LWIR thermal black body like radiation from the surface of the earth (oceans and land), directed up into the atmosphere; and Trenberth gives that a value of 390 W/m^2 corresponding to a mean global Temperature of 288 Kelvins. (+15 deg C). That radiation is selectively absorbed by CO2 which we are told is well mixed in the atmosphere so it is the same all over the earth, so it should absorb the same amount of radiation all over the earth.
Well hang on a minute; there’s a bit of a problem. You see the whole of the earth surface is NOT at 288 K TEmperature. In the Antarctic highlands around Vostok station; there are places that can get down to just 183 K or -90 C, and Vostok itself has recorded within one deg C of that. That is just 63.54 % of the global mean of 288 K, and for such a Temperature, the surface radiation limit would be just 16.3% of 390 or 63.6 W/m^2 (max). It might be less than that based on spectral emissivity.
So we have a problem that some of the earth surface emits only 1/6th of that emitted at the global mean temperature so in those regions, the climate sensitivity due to CO2 must be very much less than 1.5 to 4.5 deg C per doubling; since you have only 1/6th of the driving energy.
At the other end, you have arid desert tropical regions, where actual surface Temepratures easily reach +60 deg C; and official weather station records have come within a few F degrees of that (for the air temperature). And on some paving surfaces Temperatures of +90 deg C have been measured (the egg cooking experiments); but we’ll just take the +60 which gives us 333 Kelvins; which is 15.6% above the global mean of 288 K. So the max BB surface emission could be 1.787 times the 390 W/m^2 Trenberth gives; or 697 W/m^2. Well that is eleven times the min value for the Vostok region; and because of the seasons; both of those extremes could occur simultaneously.
So from a physical theory point of view we cannot compute the CO2 energy interception amount, without knowing the Temperature of the surface which is emitting the driving energy.
But apart from the fact that we don’t even have a starting constant energy source driver; nothin in that Temperature range information yes insists that the surface Temperature (which controls the driving source) is then logarithmically related to The very temperature which is the start of the whole sequence.
So clearly “Climate Sensitivity” has a different value over a very wide range, depending on where you are on earth. Are you aware of any global network that constantly monitors the local value of climate sensitivity ; to compute a globalk average value ? I’m not !
It would seem that we don’t have any sampled data with which to establish a physical theory of climate sensitivity; that derives a mathematically logarithmic relationship between average global surface temepratures, and average global (well mixed) atmospheric CO2 abundance. The likelihood that a complex array of interractions between parameters some of which range over more than an order of magnitude should somehow come up with a theoretical logartihmic relationship for averaged data, is rather remote.
So far, I’ve seen neither credible experimentqally observed data, nor basic physics derived theoretical relationship, that supports a logarithmic connection as a better fit than say a linear fit; or any other mathematical relationship. The experimental data doesn’t fit ANY well behaved continuous function; sometimes the two variables increase together or decrease together and sometimes they go in opposite directions. There are well known time delays between some of the physical phenomena. For example there is a delay between ocean warming, and release to the atmospehre of extra CO2 since there is more CO2 at colder deeper levels, which has to propagate to the surface to enter the atmosphere; so that would require that there be some offset time between the CO2 and Temperature data sets, to arrive at properly related values; but no possible delay of either data set, can be shown to produce a logarithmic well behaved connection as more plausible than say a linear fit.
It seems that someone; apparently the late Dr Stephen Schneider I’m told, simply invented the logarithmic relationship out of whole cloth; and climatists don’t seem to find that a problem. Well whoever dreamed up cs; and my sincere apologies to the late Dr Schneider if in fact it wasn’t him; there’s no data or theory that supports such a relationship.
So trying to do ever more arcane statistical analysis on chaotic random data, to derive on some new grounds a “better” value for Climate Sensitivity, just seems to be a total waste of the taxpayer’s money in the form of government research grants or agency funding.
Other than that John Did your inclusion of the water vapor “forcing” include the simple and incontrovertible fact that water vapor (any water vapor) ALWAYS reduces the ground level solar insolation; so in that sense it would cause a negative forcing; not a positive one.
I don’t know John whether you have ever experienced a total eclipse of the sun; I never have but I have friends who chase them; like the Druids gathering at Stonehenge; but I have observd many partial eclipses; and in a partial solar eclipse; we get an instant demonstration of what would happen if the value of the TSI should drop. The instant effect for even a 30% partial eclipse is that the daytime temperature immediately plunges given an open cloudless sky.
So what if the TSI permanently dropped by 30%. It would get colder; but presumably you would get a lot of precipitation of rain/snow/sleet/hail/wtatever, and eventually some of that cloud would disappear; so more of the reduced sunlight could eventually rach the ground. So over some short time frame, the cloud level would adjust to the new lower TSI and we would have a lower total global cloud cover; but the net ground level solar insolation would be lower than before but not 30% lower; the cloud change would recover some of that.
But it is inescapable; that if you lower the value of TSI; then the earth must get colder; and conversely if you raise TSI, the earth would get warmer; but cloud adjustments would partially compensate for the TSI change (how much I don’t know).
Well just as a partial solar eclipse lowers earth temperatures; and a lower TSI would do so too, so too would any long term increse in global cloud cover reduce temepratures since clouds ALWAYS reduce ground level solar insolation as does water vapor.
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.
Now that doesn’t mean that H2O does not warm the earth or the atmosphere. We know from the arid high desert night temperature drop, that CO2 is not capable of holding up surface temepratures; but in the presence of H2O the cooling rate is much lower at night.
But it is the three phase presence of H2O that provides the regulation via the mechanism of cloud modulation. And as Gavin Schmidt has recently made very public; H2O it the ONLY condensible GHG in earth’s atmospehre; so it is the ONLY one that is capable of providing offsetting warming and cooling effects; and it can do all of that without any assisitance from CO2; either logarithmically or linearly.
Hmm.
Why 33 deg. C for the Earth’s Greenhouse Effect is Misleading
Needs work. (1) The calculations are not shown. and (2) the chain of thought goes fairly straight until suddenly, you whip out this statement without (as near as I can tell) reference or provenance or support:
“The normally discussed range of CO2 effect on the GHE is 9-26%.”
Where did this come from? If this statement is wrong, the entire argument from then on has no merit. Please fill in the missing train of thought. All of it.
Good post John,
I just became aware of your site today and will have to bookmark it. You’ve earned yourself another reader today.
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.
Doug Proctor says
Being “professional” doesn’t necessarily translate into being “correct”. An ivory tower is unscalable only where dissent is eliminated, as in Real Climate. So WUWT is not an “ivory tower” per se, but also is NOT a non-professional arena.
So contrary to your statement, distrust of places like Real Climate will live on; acrimony is not found there because dissent is not allowed there. Dissent at WUWT is encouraged, which fosters trust whereas acrimony is generally self-policing and fades away.
I wonder if you are lumping conduction into convection in this statement?
I will also offer this observation: If CO2 contributed 86% of the GHE (I prefer Atmospheric Effect) consider what would happen on a very clear night in contrast to a high humidity night. Say the temperature dropped 5 C. degrees with a high humidity night. With the same starting temperature but a clean and very low humidity atmosphere the temperature might drop 20 C. degrees. But the CO2 is still there with its purported 86% contribution. Thus, we’ve just gotten a 15 C. degree drop from removing just 14% of the contributing GHGs. If we could then remove all of the CO2 should not the temperature respond by a corresponding drop of about ~ 92 C? [ (86/14)*15 ] That seems unlikely.
OOPS! This statement:
. . . 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 . . .
Richard:
Please inform us as to how there would be snow cover without an atmsophere. That assumption wouled require that there was at least an atmosphere of only water vapor and that was precipitated out as snow leaving a dry vacuum. Pretty silly yes? If the iceans were never able to evaporate the ice would be a very dark color not white and would absorb heat probably better than land surface. Again this is impossible as the exposed water would indeed evaporate and create an all water vapor atmosphere how thick? I have no idea. But snow does require this and it would also require there would be a green house effect. Get rid of the water and you have the no atmosphere model.
Barry S.
I believe that GHE should be viewed as a resistance to the rate of energy lost to space, not a “force”. In the radiative equation W=kT^4, T^4 is the force and 1/k is resistance. GHE increases the resistance 1/k and reduces k. Using this approach in a statistical analysis of the Reanalysis data, I find that evaporation/condensation and freeze/thaw rates are the rate controlling processes. A possible CO2 effect of reducing k is not observed with statistical significance. http://www.kidswincom.net/CO2OLR.pdf.
bob says: at 8:59 am
After all, something has to provide the warmth to keep the water vapor in its gaseous state, and that something is CO2.
Sometimes it is cold and clear, sometimes cold and cloudy, sometimes warm and clear, and sometimes warm and cloudy. Sometimes there is CO2 in the atmosphere, and sometimes there . . . Oh, wait a minute!
steven says:
October 25, 2010 at 8:31 am
I believe the models would consider water vapor a feedback instead of a forcing.
As water vapor can evaporate all on its own without the presence of CO2 or warming and humid air is lighter than dry air, water vapor will cause convection and winds all on its own. If the convection or winds over landscape result in clouds then they raise albedo again independent of CO2. Given the effect of the Coriolis force, the sun’s insolation and the winds that result in the Hadley and Ferrel cells and the dropping cold dry air into the polar regions. All without CO2 …..
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. So if you believe that everything would sit in stasis without the presence of CO2 – then you call every change from stasis a feedback. Regardless of how wrong that is.
Sorry, I left the i out of the . Should be . Two mistakes in just a few minutes. I’ll go outside now and get some fresh air.
Your argument will be more difficult to argue against since you included the “total forcing from the surface to the atmosphere of 452 W/m2”. Thanks for that. — John M Reynolds
Do the radiation calculation and the real Greenhouse warming should be c. 60K. The fact that it’s c. 33K is because a lot of the heat is convected upwards by weather so lower atmosphere temperatures are reduced substantially. So that is one reason why the models used in Skeptikalscience article are wrong and you can’t trust that 32W/m^2!**
**It’s because the equation derived by Hansen and Lacis in 1974 to calculate cloud albedo from optical density, used off-set high predicted CO2-AGW by the cloud part of global dimming, is plain wrong, even though it came originally from Carl Sagan. It only considers internal diffuse optical scattering and there’s a second process which can dominate in thick clouds. Thus, the ‘cloud albedo effect’ cooling [0.7 W/m^2] is imaginary and if you put in the correct physics, you should get heating, possibly another form of AGW.
Thus there is very little you can trust except experiment, and that shows global warming apparently ceased in 2003!
You reference the Keihl, Trenberth document. FIG. 7. The earth’s annual global mean energy budget based on the present study. Units are W m-2. From that figure I would like to suggest that the 107 Wm-2 that is reflected is also out of play for the GHE and therefore 195 Wm-2 (342-107-40) would be the correct approximation for the amount of radiation subject to the GHE and yielding a sensitivity of ~.15 Deg C/W m-2.
Thanks for all interesting feedback.
As I stated at the beginning of the article I like to compare results and models. There are many valid points about the total GHE being larger than I used.
The main take away I get from this is that the more energy is involved in the total system, the less impact a change will have. There are many estimates that put the actual climate sensitivity in the range of 0.24-0.30 °C/(W/m2), myself included.
There is so much energy involved in the current steady state system that the small proposed “forcing” by CO2 is trivial. I used the 32 W/m2 for CO2 even though I strongly disagree with that value. That is why I had to search for the warmist value because they clearly need a large value to support their theory.
Thanks for the support.
John Kehr
The Inconvenient Skeptic
As DR notes above Roy Spencer and Lindzen’s published papers supports the assertion the feedback is negative rather than positive. (Planetary cloud cover increases or decreases to regulate planetary temperature.)
Spencer explained why previous analysis appear to support the assertion that the feedback was positive rather than negative, at a presentation made at the 2009 AGU fall meeting and in his published paper. (The problem in the past analysis was timing of the effect. Tail wagging the dog vs dog wagging tail.)
http://www.drroyspencer.com/2010/09/why-33-deg-c-for-the-earths-greenhouse-effect-is-misleading/
John Kehr, fine article.
Your simple approach IS proper science and don’t let anyone tell you otherwise. Those pieces have been rattling around in many minds and comments here but you had a fantastic way to put it all together and explain it, I’ll study your style!
When I said a couple or weeks ago that co2 had NO affect on Earth’s temperature I have kicked myself for stating it so absolutely, very un-scientifically-like. That shallow curve in graph two most very likely explains Mislolczi’s IR optical thickness all of the radiosondes have recorded, the differential is then shallow enough to not register and plot as a single point within tolerences. Once again, great, great article!
I have read your post twice & do not see any obvious flaws in logic. I would love see a warmist post on here an analysis of why this is not a correct analysis. If the warmist camp can’t refute this logic, then the analysis posted here is as strong as any why the alarmist position is invalid.
On a related note, it also explains why temp data has been shown again & again to track such things as ENSO, NAO, PDO, etc – if CO2 forcing is small, it will be hard to see in the observed signal.
I would also love to see Dr. Spenser’s take on this analysis. Do you think this is a solid /defendable analysis of sensativity & forcing?
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?
@Kehr in OP
“That 30 °C difference is caused by the insulative effect caused by the atmosphere.”
Variable albedo plays a potentially huge role. The earth and the moon would have substantially the same albedo absent ocean and atmosphere. The moon’s average temperature (as measured deep enough into the regolith so that there is no annual variation) is -35C. If the earth is 15C then that’s 45C to be accounted for by GHG insulation and albedo difference. I understand GCMs all use a static value for albedo and that value varies by some 70% between models. In other words it’s a fudge factor to be adjusted manually to make the model’s output look more like historical observations.
Observations of earth’s average albedo in real-time are all rather recent and show substantial variation.
Of course the actual average temperature of the earth is of course the average temperature of the ocean which is about 4C not 15C. The surface today is temporarily much warmer than “usual” if by “usual” we mean the last few million years. The difference between the usual temperature and today’s temperature is almost all due to change in average albedo. The only “tipping point” due to runaway positive feedback is snow and ice cover which, because changing reflectivity of clear sky land/ocean from single digits to close to 90% for snow and ice changes the amount of energy reaching the surface by tens to hundreds of watts/m^2 vs. less than 10 watts for doublings of CO2 from any base point above 200ppm.
The way I see it any marginal warming we get from any amount of CO2 humans can practically add to the atmosphere is in primary effect an increased margin of safety above the tipping point that ends interglacial periods. I’m an engineer too so we should both appreciate thinking about safety margins. The margin I’m concerned about is the one that keeps the earth covered with liquid water and green plants instead of ice and snow.
Lovely deductive reasoning, but I can’t help but feel there is a danger in considering just one factor (CO2) in isolation.
The atmosphere as a dynamic and complex mishmash of many forcings, feedbacks etc, so it is really impossible to look at the effect of one on its own.
If CO2 does have a huge 80C forcing, what negative forcings from methane, water vapour, ozone etc would it take to reduce the overall effect to observed levels?
And is that an alternate?
Andy
PS No I don’t believe Co2 has such impacts (if any) but how to deduce what is really at play – just nature taking its course perhaps?