Guest post by David Archibald
The greenhouse gasses keep the Earth 30° C warmer than it would otherwise be without them in the atmosphere, so instead of the average surface temperature being -15° C, it is 15° C. Carbon dioxide contributes 10% of the effect so that is 3° C. The pre-industrial level of carbon dioxide in the atmosphere was 280 ppm. So roughly, if the heating effect was a linear relationship, each 100 ppm contributes 1° C. With the atmospheric concentration rising by 2 ppm annually, it would go up by 100 ppm every 50 years and we would all fry as per the IPCC predictions.
But the relationship isn’t linear, it is logarithmic. In 2006, Willis Eschenbach posted this graph on Climate Audit showing the logarithmic heating effect of carbon dioxide relative to atmospheric concentration:
And this graphic of his shows carbon dioxide’s contribution to the whole greenhouse effect:
I recast Willis’ first graph as a bar chart to make the concept easier to understand to the layman:
Lo and behold, the first 20 ppm accounts for over half of the heating effect to the pre-industrial level of 280 ppm, by which time carbon dioxide is tuckered out as a greenhouse gas. One thing to bear in mind is that the atmospheric concentration of CO2 got down to 180 ppm during the glacial periods of the ice age the Earth is currently in (the Holocene is an interglacial in the ice age that started three million years ago).
Plant growth shuts down at 150 ppm, so the Earth was within 30 ppm of disaster. Terrestrial life came close to being wiped out by a lack of CO2 in the atmosphere. If plants were doing climate science instead of us humans, they would have a different opinion about what is a dangerous carbon dioxide level.
Some of the IPCC climate models predict that temperature will rise up to 6° C as a consequence of the doubling of the pre-industrial level of 280 ppm. So let’s add that to the graph above and see what it looks like:
The IPCC models water vapour-driven positive feedback as starting from the pre-industrial level. Somehow the carbon dioxide below the pre-industrial level does not cause this water vapour-driven positive feedback. If their water vapour feedback is a linear relationship with carbon dioxide, then we should have seen over 2° C of warming by now. We are told that the Earth warmed by 0.7° C over the 20th Century. Where I live – Perth, Western Australia – missed out on a lot of that warming.
Nothing happened up to the Great Pacific Climate Shift of 1976, which gave us a 0.4° warming, and it has been flat for the last four decades.
Let’s see what the IPCC model warming looks like when it is plotted as a cumulative bar graph:
The natural heating effect of carbon dioxide is the blue bars and the IPCC projected anthropogenic effect is the red bars. Each 20 ppm increment above 280 ppm provides about 0.03° C of naturally occurring warming and 0.43° C of anthropogenic warming. That is a multiplier effect of over thirteen times. This is the leap of faith required to believe in global warming.
The whole AGW belief system is based upon positive water vapour feedback starting from the pre-industrial level of 280 ppm and not before. To paraphrase George Orwell, anthropogenic carbon dioxide molecules are more equal than the naturally occurring ones. Much, much more equal.
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kuhnkat (18:21:42)
Mauna Loa is pretty active at the moment. I have no problem with the infilling. At this point, the monthly/annual cycle of carbon dioxide is well understood. CO2 is a “well-mixed” gas, so the day-to-day fluctuations are not that large.
George E. Smith (18:24:32)
I agree. The only way a greenhouse can get enough energy to heat the world and provide for all the losses is if it has two physically separated radiative areas. Here is my redo of Trenberth that shows how this would work.
Also please see my post called The Steel Greenhouse, which lays out the mechanics of the greenhouse effect.
Phil. (10:26:06) :
OK. I’m going to break my rule of silence–sort of. I was reviewing Phil’s (10:26:06) comment, and I’m pretty sure he’s wrong. I get the feeling Phil thinks the “average emissivity” of the Earth is an average over frequency. Specifically, Phil wrote:
“In order to determine the average absorptivity of the Earth you’d integrate over all frequencies:
∫A(ν)Isun(ν)dν/∫Isun(ν)dν
Similarly for the Earth’s emissivity:
∫ε(ν)Iearth(ν)dν/∫Iearth(ν)dν
Where Isun is the emission spectrum of the sun and Iearth is the emission spectrum of the earth so while A(ν)=ε(ν) at any ν the averages are not the same because the spectra aren’t the same.”
I strongly believe although Phil’s definition of average emissivity being the average over frequency is a valid operation, it does not apply to problem at hand. Phil treats each square meter of the earth as having the same property–that property being the emissivity (ratio of actual radiated power at frequency f …to… the radiated power at that frequency from a black body at the same temperature). Phil then computes the “average emissivity” by averaging this ratio over frequency. If this is the definition of average emissivity, then a square meter of the Earth’s surface does not emit total power that is proportional to T^4. This can be seen by inserting a frequency dependent term in Planck’s law and then performing the integration over frequency. The resulting total emitted power from the Earth’s surface will NOT be the “average emissivity” times the Earth surface area times the Stefan-Boltzmann constant times the Earth temperature to the fourth power.
Rather, when using an “average emissivity” in conjunction with the T^4 law, the emissivity is averaged over space, not frequency. That is, for each unit area of Earth surface, the emissivity is frequency independent; but from unit area to unit area, the value of the emissivity varies. The “average emissivity” is the weighted average (weighted by area) of the differential area emissivities. This definition of “average emissivity” is consistent with the T^4 total power radiation rule because the T^4 law applies for each differential area; and if we assume the Earth temperature is uniform over its surface (an inherent assumption when the area used in the formula is the total area of the Earth), then the T^4 term can be treated as a constant with respect to integration over the surface area of the Earth.
Bob Armstrong (18:51:49)
Bob, you misunderstand what is being done. Actually, the assumption is different. It is that in the thought experiment of no greenhouse gases, it is assumed that the amount of sunlight currently not being reflected by the albedo would be warming the thought experiment earth.
The albedo reflects about 30% of the sunlight, so it is not currently warming the earth.
Since we want to compare like with like, in our thought experiment we maintain the same amount of energy absorbed by the earth as is absorbed today. And as a result, in our thought experiment, the earth gets about 70% of the 345W/m2 of incident energy, or about 235W/m2.
Assuming for the thought experiment that the earth is a blackbody, the temperature corresponding to 235W/m2 is about -20°C, on the order of thirty degrees or so cooler than we are with the same albedo plus a greenhouse effect. You will get a slightly different number if you use the IR emissivity of the planet (generally taken to be on the order of 0.95 or so), but the basic principle is sound.
w.
Willis Essenbach wrote at 21:29:37, 9th March:
“The only way a greenhouse can get enough energy to heat the world and provide for all the losses is if it has two physically separated radiative areas.”
That’s pretty interesting, as there are two or three radiating to space areas, I reckon:
1. A water vapour area, somewhere around the cloud tops. this does most of the emitting to space, because it is hotter (around -10DegC), and because water vapour can emit across a wide range of frequencies.
2. A CO2 area, the bottom of which I make to be around the Tropopause, and extending right up through the Stratosphere. So much of it quite cold, around -55DegC, but with a neutral or positive temperature gradient.
3. An Ozone radiation zone in the lower stratosphere, ie somewhere near the top of the CO2 layer.
Spector (16:05:02) :
Spector, you can do this easily using the MODTRAN line-by-line online radiation calculator.
It is worth noting that MODTRAN gives a smaller number than the IPCC for a doubling of CO2. For a clear-sky doubling from 375 to 750, MODTRAN gives a surface warming of 1.3°C …
To get this figure, first run MODTRAN at 375 ppmv. Then write down the amount of radiation escaping the earth, “Iout”.
Then set the CO2 to 275 ppmv and run it again. You will notice that “Iout” is smaller (because more is absorbed).
But Iout must remain constant (the heat gained by the earth must be lost to stay in equilibrium.) So you need to input a “Ground T offset”, in effect warming the earth to increase Iout to its original number. For clear sky and relative humidity remaining constant, the offset is 1.3°C.
Play with it, it is fascinating.
w.
Reply to Willis Eschenbach regarding measuring CO2.
“It is immediately obvious when the air is contaminated with volcanic CO2, because as you might imagine the CO2 levels spike off the charts. These samples are not used for baseline CO2 measurements…”
If it was totally “either or”, that would be ok. If however, the atmosphere sometimes contains a little volcanic CO2, you can get whatever answer you want by adjusting the cut-off point.
Reed Coray (21:37:25) :
Phil. (10:26:06) :
OK. I’m going to break my rule of silence–sort of. I was reviewing Phil’s (10:26:06) comment, and I’m pretty sure he’s wrong. I get the feeling Phil thinks the “average emissivity” of the Earth is an average over frequency. Specifically, Phil wrote:
“In order to determine the average absorptivity of the Earth you’d integrate over all frequencies:
∫A(ν)Isun(ν)dν/∫Isun(ν)dν
Similarly for the Earth’s emissivity:
∫ε(ν)Iearth(ν)dν/∫Iearth(ν)dν
Where Isun is the emission spectrum of the sun and Iearth is the emission spectrum of the earth so while A(ν)=ε(ν) at any ν the averages are not the same because the spectra aren’t the same.”
I strongly believe although Phil’s definition of average emissivity being the average over frequency is a valid operation, it does not apply to problem at hand.
It certainly does (and any other one).
Phil treats each square meter of the earth as having the same property–that property being the emissivity (ratio of actual radiated power at frequency f …to… the radiated power at that frequency from a black body at the same temperature). Phil then computes the “average emissivity” by averaging this ratio over frequency.
And if you have an heterogeneous surface you integrate over the whole surface so you end up with a triple integral: over ν and two spatial dimensions.
>>
George E. Smith (18:24:32) :
I am not a supporter of Trenberth’s view of earth’s energy budget.
<<
Gee George, why not? Everyone else on the planet seems to believe in his figures.
Phil is right; the cloud cover is supposedly 62%. Trenberth combines three cloud layers (49%, 6%, & 20%) to get that figure. He calls it “random overlap,” but to me it looks like an application of the Inclusion-Exclusion principle. The application of the principle is rather cumbersome. I prefer the shorter version: taking the complement of the product of the complements or (1 – (1 – 0.49)*(1 – 0.06)*(1 – 0.20)) = 61.6%. His famous energy diagram should state: “62% cloud cover assumed,” but it doesn’t. After this calculation, the term “cloudy” is completely ambiguous throughout the rest of the paper. Every time you see “cloudy,” does Trenberth mean 100% cloudy, 62% cloudy, or something else? We really don’t know.
He computes latent heat flux from total global precipitation: 984 mm/yr. He gets 78 W/m^2, which implies the latent heat of vaporization of 2500.79 kJ/kg. That’s the energy required to convert water at 0 ºC to water vapor at 100 ºC. I’m not sure that’s a correct global average value, but I’m not a climate scientist.
He uses two methods to compute the sensible heat flux; however the bulk aerodynamic formula works for me. That number is 24 W/m^2.
My favorite computation is the value for the atmospheric window, and I quote:
This is really sloppy math. The term “cloudy” is again ambiguous. If Trenberth’s cloudy term means 62%, then the correct window value is 80 W/m^2. He can stop there (but he doesn’t). If he means 80 W/m^2 is 100% cloudy value then he should interpolate between 99 W.m^2 and 80 W.m^2 and get something like 87 W/m^2. Apparently the 80 W/m^2 cloudy value is thrown in as a detractor, because he interpolates between 99 W/m^2 and 0 W/m^2 and rounds up to 40 W/m^2. I guess the desired answer is 40 W/m^2. Apparently no one has ever read this paper and corrected the error. His 2009 update still uses the same 40 W/m^2 for the window–without further comment.
Jim
toyotawhizguy (07:15:59) :
@Derek (05:01:54) :
Why and how CO2 logarithmic effect is modelled, people / history / plus a few plots,
all in a free pdf.
(http://www.)
globalwarmingskeptics.info/forums/thread-309.html
————
Link doesn’t work. Try this:
http://www.globalwarmingskeptics.info/forums/thread-309.html
Thank you toyotawhizguy I was having problems posting and thought the full link might have been the problem, so just separated it off the start.
Carl Chapman (22:37:03) :
Reply to Willis Eschenbach regarding measuring CO2.
“It is immediately obvious when the air is contaminated with volcanic CO2, because as you might imagine the CO2 levels spike off the charts. These samples are not used for baseline CO2 measurements…”
If it was totally “either or”, that would be ok. If however, the atmosphere sometimes contains a little volcanic CO2, you can get whatever answer you want by adjusting the cut-off point.
.
Hear, hear, and what about the underwater volcanoes / volcanic activity just off the shores of Mauna Loa island, how are they dealt with?
Great frauds have been purpetrated by the omission of outliers.
AND the use of averages with no raw data comparison / check able to be done I’d add to the paraphased “old” quote above, of a Dr. Glassman comment, on the CO2 acquittal thread at the rocket scientists journal blog.
The four corners of deceit: media, government, science, and academia. Telling lies is more important to liberals than telling the truth, because by telling lies, the liberals can influence the narrative. They protested about the new media and the Internet because they recognized that they would not have as much power and influence. In their minds, only they are qualified to determine what is newsworthy. Their arrogance is only exceeded by their willingness to practice deliberate ignorance about certain stories and facts that do not fit the template. Lies and lying are corrosive and pathological. The liberals are the most dangerous and intolerant of all. Man made GW and man made CC are unproven hypotheses. Most reporters do not know what a hypothesis is. Reporters are innumerate and lack basic science knowledge. Their eyes glaze over when data is represented on a graph. They willingly brag about their inability to perform simple arithmatic. Do not drink the Kool-Aid. Do not believe the drive-by reporters.
(Reed, cba, George, …) A peripheral note about “Reif”:
It appears that most of us have suffered through this book during our education. I’ve never had a problem with Reif’s actual content, but his way of packaging the explanations leaves a lot to be desired. My own TD prof, way back then, bitched about it constantly, but for some reason continued to require the book for his courses. We came to the conclusion that he liked to have something that “bugged him” so that he would be inspired to teach us the “right” way.
On many later occasions, whenever I have referred to the book for some purpose, all of that has popped right to the surface of my mind, so perhaps it wasn’t such a bad strategy after all. I do, however, try not to inflict this approach on my own students. The pain/gain ratio doesn’t seem to be worth it.
/dr.bill
I agree with Jim Masterson (00:07:34) that you can’t take Trenberth’s diagram at face value.
For example, the reflectance of sunlight by clouds (76) versus the surface (29) are clearly off. It should be close to half each or the math on Albedo would never work.
The average Albedo of clouds themselves depends on their thickness, water content, height and type and these amounts have been over-estimated in Trenberth’s figures. About 15 to 20 W/m2 should be shifted between the two.
Gary Novak (21:12:24)
Thats the point about no more heat retention according to increase in c02. Beyond a certain point it doesn’t matter how much more c02 goes into the atmosphere. The net radiative result will be the same at 300ppm as at 600ppm. Fine analogy re: sheep and gates
Larry Barnes (04:08:37) :
I find the constant reference to the 30 degree greenhouse effect very puzzling. Based on the Stefan-Boltzmann law, the Earth as a black body should be about 278 Degrees and not the often quoted 258 degrees. Most climate scientists ingore the fact that the Earth is a system involving oceans and the atmosphere and both are contributing to the socalled greenhouse effect. You cannot just say the earth without the atmosphere would be a certain temperature because you have no scientifically valid basis for such an assessment. The albedo factor often used refers only to the visible light albedo. More than half of the sun’s radiation is outside the visible range and exhibits a much lower albedo. Further, the visible albedo which has been measured is a variable and seems to be controlled somehow by solar activity. Throw in the fact that the solar constant is not infact constant and you can see that any analysis based on the 30 degree warming factor is spurious. There are far too many variables and far too little understanding of the processes involved.
============
Well put. Somebody sometime should write an account of all the huge uncertainties that plague every single aspect of this supposedly settled science, starting with the carbon cycle itself and the bizarre assumption that the ocean-land-plant systems are incapable of dealing with such a small fraction of the total carbon transfers between them and the atmosphere.
The following letter by J. Marvin Herndon published in Current Science adds yet another important potential variable, seldom considered: Variations in heat reaching the surface from the Earth’s core.
CURRENT SCIENCE, VOL. 95, NO. 7, 10 OCTOBER 2008
Pages 815-816
Variables unaccounted for in global warming and climate change
models
by J. MARVIN HERNDON
[…]
Models of the earth, based upon the incorrect assumption that the earth in the main is like an ordinary chondrite meteorite, are widespread and have led to the assumption that the heat coming out of the earth is constant. The reason for assumed constancy is that such models are based upon the assumption that the heat exiting earth comes solely from the radioactive decay of long-lived radionu- clides, which, on a human timescale, would be essentially constant. But that model of the earth is wrong.
From fundamental considerations, I have shown that the earth in the main is not like an ordinary chondrite, but is in- stead like an enstatite chondrite7, which leads to the possibility of the earth hav- ing at its centre a nuclear fission reactor 8–10, called the georeactor, as the energy source and operant fluid for generating the geomagnetic field by dynamo action11. Unlike the natural decay of long-lived radionuclides, which change only gradually over time, the energy output of the georeactor can be variable12. I have also introduced the concept that the earth’s dynamics is powered by the energy of protoplanetary compression13 and suggested a process whereby such energy may be deposited at the base of the crust14. There is no reason to assume that the release of stored protoplanetary com- pression energy would be constant. Such potentially variable energy exiting the earth may contribute not only to variability in the overall heat budget of the earth, but in exiting undersea may affect change to sea-water circulation currents, which may potentially affect the global weather patterns. The degree and extent has not yet been measured15.
J. Marvin Herndon’s Nuclear Georeactor
http://nuclearplanet.com/Herndon%27s%20Nuclear%20Georeactor.html
1. Balaram, P., Curr. Sci., 2008, 95, 291–292.
2. Haxel, O., Jensen, J. H. D. and Suess, H.
E., Die Naturwissenschaften, 1948, 35,
376.
3. Revelle, R. and Suess, H. E., Tellus,
1957, 9, 18–27.
4. Box, G. E. P., Empirical Model-Building
and Response Surfaces, Wiley, New
York, 1987.
5. Suess, H. E., Radiocarbon, 1980, 20,
200.
6. Cini-Castagnoli, et al., Nuovo Cimento C
Geophys. Space Phys. C, 1998, 21, 237.
7. Herndon, J. M., Curr. Sci., 2005, 88,
1034–1037.
8. Herndon, J. M., J. Geomagn. Geoelectr.,
1993, 45, 423–437.
9. Herndon, J. M., Proc. R. Soc. London,
1994, A455, 453–461.
10. Herndon, J. M., Proc. Natl. Acad. Sci.
USA, 2003, 100, 3047–3050.
11. Herndon, J. M., Curr. Sci., 2007, 93,
1485–1487.
12. Rao, K. R., Curr. Sci., 2002. 82, 126–
127.
13. Herndon, J. M., Curr. Sci., 2005, 89,
1937–1941.
14. Herndon, J. M., Curr. Sci., 2006, 90,
1605–1606.
15. Herndon, J. M., Maverick’s Earth and
Universe, Trafford Publishing, Vancou-
ver, 2008.
“”
Bill Illis (05:08:23) :
I agree with Jim Masterson (00:07:34) that you can’t take Trenberth’s diagram at face value.
For example, the reflectance of sunlight by clouds (76) versus the surface (29) are clearly off. It should be close to half each or the math on Albedo would never work.
The average Albedo of clouds themselves depends on their thickness, water content, height and type and these amounts have been over-estimated in Trenberth’s figures. About 15 to 20 W/m2 should be shifted between the two.
“”
Bill I agree too that there are some problems with Trenberth’s early paper. I think though it is more honest than his later one.
I disagree about the surface vs the cloud / atmosphere albedo. If you back out the numbers, you’ll see he is close on that one. Most of the surface is ocean and for where it matters, the ocean albedo is under about 0.04 and that is the vast majority of surface a rea. Something like Mars or Moon indicate rock albedo at around 0.16 and typical measurements suggest vegetation around 0.1 to 0.2. Put in a reasonable estimate based on these sorts of things yields a surface albedo estimate around 0.08. Measurements indicate we’ve got right around 0.3 total albedo and around 0.62 fractional cloud cover. That leaves about 0.22 for clouds (and atmosphere) albedo. Voila, his rough numbers for albedo reflection. I’m sure it’s not perfect and I’m sure it changes substantially also, but it’s a fair first hack at numbers. It is also not a very good set of numbers for agw proponents. Trenberth’s later paper seems to try to ‘help’ the numbers along a bit in obviously biased fashion.
As for numbers not properly adding up in the cartoon, remember clouds are particles of liquid and solid h2o, not vapor, so they have a continuum emission rather than merely h2o emission lines. Clouds contain localized internal thermal convection and lower & upper T values which radiate at different rates. Cloud tops are also above almost all of the h2o vapor and a bunch of the co2 gas.
Colin Davidson (16:15:27) :
Phil (8Mar10, 20:24:16) said:
“Do the math, radiation is the dominant heat loss route from the surface…”
I will use the figure in FAQ 1.1, Chapter 1, WG1, IPCC AR4 (2007), which is from Kiehl & Trenberth (1997).
The energy fluxes from the surface are (all figures are in W/m^2):
Radiation: 390-324 (back radiation) = 66
Conduction: 24
Latent Heat (in water vapour): 78
So, having done the maths (in my country we do it in the plural), the dominant heat loss route from the surface is in fact water vapour.
Bad math(s) and physics, it isn’t only the radiant energy that can return to the surface, it all can! So more correct accounting is:
390+24+78= 492 out
324=66% back
So as far as the atmosphere is concerned, it gets its energy from the surface in the following proportions:
Latent Heat:
Three Fifths16%Conduction:
One Fifth5%Radiation:
One Fifth79%When the surface warms, the Radiation
proportion decreasesincreases as T^4 and the Latent Heatproportionincreases as e^(4900/T).I wish some of these scientific posts were “peer-reviewed” before being posted at wattsupwiththat so that the site can maintain its scientific reputation. This post would might benefit from some checking and revision.
1) Estimates of the earth’s temperature without a greenhouse effect depend on whether you include the full sunlight (no albedo) or non-reflected sunlight (with albedo). Clouds and ice, made from the GHG water vapor, play an important role in the earth’s albedo.
2) The absorptions of carbon dioxide, water vapor and other greenhouse gases overlap, making it misleading to say that carbon dioxide contributes only 10% of the greenhouse. As one goes up in altitude (and temperature drops), the relative importance of water vapor and carbon dioxide to the greenhouse effect changes dramatically. Since most heat is removed from the earth’s surface by evaporation (latent heat) and convection to the upper troposphere – NOT by direct radiative cooling to space. Only the upper troposphere cools mostly by radiation and there CO2 is the most important greenhouse gas. (See Lindzen’s 2007 article.)
3) The IPCC’s analysis also uses a logarithmic relationship between CO2 are radiative forcing. The accepted coefficient is 3.7 W/m^2 for 2XCO2 rather than the 2.94 from Eschenbach’s post (a minor difference). It isn’t clear what factor this post uses to convert a forcing in W/m^2 into a temperature increase in degC. Monkton’s APS article discusses several possible values, all of which are similar. A similar value can be obtained by differentiating Boltzmann’s Law (W = oT^4) to get dW/dT = 4oT^3, substituting W/oT for T^3 to get dW/dT = 4W/T and rearrange terms to dT/T = (1/4)*dW/W. A 1% increase in radiation (dT/T; from a hotter sun or radiative forcing by GHG’s) will cause an 0.25% increase in temperature (dT/T) in degK (not degC). Since the accepted radiative forcing from 2X CO2 is 3.7 W/m^2, one can calculate that the direct warming from 2X CO2 (without feedbacks) will be only 1 degC. This 1 degC is the only part of the AGW hypothesis that might be termed “settled science”, but the IPCC doesn’t want us to know that 2X CO2 without feedbacks produces non-catastrophic warming.
4) Your bar graph appears to be wrong. The log2 of zero is negative infinity, so you can’t calculate a temperature rise for the first 20 ppm of CO2. You appear to be calculating the temperature rise associated with a rise from 1 ppm to 20 ppm – a 20X increase or 4 doublings. Using the values in paragraph 3), that temperature rise should be about 4 degC (so you may be off by a factor of 2 somewhere).
5) Using the bar graph turns a simple calculation into something hard to understand (summing up the contribution of many little bars). From 180 ppm CO2 (LGM) to 280 ppm (pre-industrial), is a 1.55 fold increase and the log2 of 1.55 is 0.64. You can then calculate the increase in radiative forcing using Eschenbach’s (2.94) or the IPCC’s (3.7) factor for the radiative forcing associated with 2X CO2, before converting to degC. Or more simply, a little more than half a doubling is a little more than 0.5 degC without feedbacks.
6) Although cold water does hold more CO2 than warm, CO2 won’t get low enough to endanger plants because plants are the main consumers of CO2 not cold water. If you put plants in a sealed system, photosynthesis stops when CO2 level reaches 100 ppm. (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC439845/?report=abstract)
This happens because water escapes out the same openings that CO2 enters, making it wasteful to try to conduct photosynthesis when there is relatively little CO2 around. (Photosynthesis also shuts down every night when there aren’t enough photons around also.)
7) The IPCC’s models don’t assume that the water vapor feedback begins at 280 ppm. The use a figure of +2.0 W/m^2/degC for the water vapor feedback – whether the temperature was 4 degC lower and CO2 was 180 ppm during the last ice age or 4 degC and 500 ppm higher in 2100. You are completely correct calculating that the radiative forcing associated with anthropogenic increases in greenhouse gases (1.5X for CO2 along, 1.75X for all long-lived GHG’s) should have raised temperatures far more than observed if feedbacks amplify direct warming by CO2 from 1 degC/2XCO2 to 1.5-4.5 degC/2XCO2. Although the IPCC doesn’t like to publicize this discrepancy, they “fix” this problem by including cooling from aerosols (global dimming) – a phenomena that is currently assumed to negate 25-75% of the current warming due to increased GHG’s. With uncertainty this larg, no one can prove whether this hypothesis is correct – but the science is nevertheless “settled” and we are “>90% certain that the observed 0.7 degC warming is mostly due to man”.
Henry Pool (21:10:00) :
Henry, that’s where I come down, too.
The basic premise or presupposition that CO2 is a so-called “greenhouse” gas has failed to be demonstrated to a level of scientific certainty in my opinion.
(Without scientific certainty of the basic premise, no action should be taken.)
Water vapor and CO2 are not in the same ballpark either in terms of concentration in the atmosphere, and just as important, behavior in the atmosphere.
CO2 is a trace molecule that is dispersed evenly in rapid diffusion from point sources with no concentration at any height in the atmosphere or geographical area.
Of course, water vapor is both concentrated by geographical area (air masses above geographical areas, to wit, storm fronts, low pressure and high pressure systems) and atmosphereic height (from ground fog to stratospheric clouds). And, water vapor has reflective properties in cloud cover and heat retension in high humidity clear areas.
Again, CO2 has none of those physical properties in the Earth’s atmosphere.
There is a woeful lack of basic science that supports the “greenhouse” supposition.
And, unless or until the basic “greenhouse” premise of CO2 is demonstrated in controlled laboratory experiments that are analogous to Earth’s atmosphere (both concentration and behavior), hairsplitting at this ‘parts per million’ or that ‘parts per million’ below some upper limit is a waste of time.
Basic Science has been neglected in the rush to generate momentum for a (dubious) political agenda.
Let me say, and this might bring some brick-brats my way: Too many folks, here, on this website have accepted the basic premise of CO2 as a “greenhouse” gas and go on to argue splitting hairs.
In a sense, these folks have conceded more than half the battle (scientific argument) and are already arguing on AGW turf (the position of the deck chairs on the Titanic).
Maybe its fun to do that, but it’s not scientific or productive.
Frank:
Only the upper troposphere cools mostly by radiation and there CO2 is the most important greenhouse gas. (See Lindzen’s 2007 article.)
Henry@ur momisugly Frank
Sorry Frank, you lost me here. How do you people always seem to know absolutely for sure that CO2 is a greenhouise gas?
What testing can you refer to that confirms that CO2 is a greenhouse gas?
The trick they used (to convince us) is to put a light bulb on a vessel with 100% CO2.
But that is not the right kind of testing.
You must look at the spectral data. Then you will notice that CO2 has absorption in the 14-15 um range causing some warming (by re-radiating earthshine) but it also has a number of absorptions in the 0-5 um range causing cooling (by re-radiating sunshine). So how much cooling and how much warming is caused by the CO2? How was the experiment done to determine this and where are the test results? If it has not been done, why don’t we just sue the oil companies to do this research? (I am afraid that simple heat retention testing will not work here, we have to use real sunshine and real earthshine to determine the effect in W/m3 [0.04%]CO2/24hours)
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Frank (08:39:47) :
This happens because water escapes out the same openings that CO2 enters, making it wasteful to try to conduct photosynthesis when there is relatively little CO2 around. (Photosynthesis also shuts down every night when there aren’t enough photons around also.)
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It depends on what you mean by “photosynthesis.” There are a subset of C4 plants called CAM (includes many desert plants, ice plants, and Bromeliads such as the pineapple) where they keep their stomata closed during the day (ostensibly to conserve water) and perform CO2 processing at night.
Jim
Frank (08:39:47) :
I wish some of these scientific posts were “peer-reviewed” before being posted at wattsupwiththat so that the site can maintain its scientific reputation. This post would might benefit from some checking and revision.
As would yours!
6) Although cold water does hold more CO2 than warm, CO2 won’t get low enough to endanger plants because plants are the main consumers of CO2 not cold water.
Not true, the ocean is a larger sink for CO2 than plants.
“”” Phil. (20:38:52) :
George E. Smith (18:24:32) :
And I have to say I am quite suspicious of some of Trenberth’s numbers. Well for a start, I disagree totally with the phony construct of dividing the solar insolation by 4, since the relation between incoming flux, and surface temperature reached is non-linear, so that process under values the peak surface temperatures reached and so under-estimates the LWIR emission.
The division by 4 is necessary to determine the average incoming flux at the surface, if you wanted to calculate the local intensity you could scale by cos() but if you integrate over the whole surface you’d still end up with a factor of 4. “””
Phil, of course I know THAT it is traditional to divide the real TSI numbers by four on the theory that a circle has area pi.r^2, while a sphere has area 4.pi.r^2. I just don’t know why they would do that, since Gaia doesn’t do that.
I also know that at any moment somewhat more than half of the total earth surface, is sunlit; albeit under some cloud cover some places. Based on the
0.5 degree angular diameter of the sun, and the approximately one degree horizon refraction by the atmospere, I estimate it (stick in the sand wise) at somewhere in the 51 to 52% range.
I’m quite surprised by your 62% average cloud cover figure; 50% is the number I have seen most, but I admit I haven’t done a lot of digging; so I’m ambivalent about it. If it is indeed 62%, then that would give me an even more jaundiced view of the albedo importance of surface ice and snow.
But I reject the idea of quartering the TSI, simply because that might be the average for any single surface location over time.
If I put my hand in the freezer half the time, and in boiliong water half the time; on average the temperature might not be too bad. The problem is my thermal time constant, is short enough that I reach temperature equilibrium in either location, so I don’t get the benefit of that lower average.
Neither does the earth surface. The thermal effects and weather/climate effects that take place during a surface insolation of 1000 W/m^2 are quite different from what happens at 1/4 of that value; so the poroblem is a non linear one. Why not model a real planet that rotates under its sunlight, rather than a fictional one that is uniformly illuminated over 4pi space; even at the poles at midnight.
As to the atmosphere + clouds, the atmosphere treats incoming and outgoing (radiation) similarly (in an optical sense); allowing of course for the spectral differences. That’s not so for the clouds.
The sun is a near point source; 0.5 deg angular diameter, so clouds casta shadow, with a half degree penumbral edge. In that shadow zone, the surface is cooler, depending on the density of the cloud, the cloud attenuates the complete beam as seen in the shadow zone.
BUT the surface in that shadow zone is a diffuse radiator; at least Lambertian, in the case of an optically smooth surface such as calm water, and more likely near isotropic for other rough surfaces. So the same cloud that formed that shadow zone, can only intercept a small fraction of the outgoing diffuse LWIR from that very same shadow zone. The difference is most noticeable in the case of essentially total opacity of the cloud. No sunlight reaches the ground (in the shadow zone) yet almost all of the LWIR being emitted from that same spot, still escapes around the cloud.
Yes I know that there can be cloud layers larger than the cloud height, where my model only applies to the perimeter of the cloud rather than the total area; but that doesn’t change the fact that clouds are a lot more effective in blocking incoming sunlight than they are in blocking the diffuse outgoing LWIR. And yes I also do realize that the cloud will also intercept diffuse LWIR from outside the shadow zone.
If the cloud tops are hotter than the cloud bottoms (don’t dispute that), then they also will radiate more upwards, than the bottoms do downwards. I still say the exit path is favored over the earthly direction.
And Trenberth does label that 324 W/m^2 as BACK RADIATION; he does not mention any back conduction or convection; but he does show some rain; but surprisingly no snow. I haven’t given a lot of thought to the Latent heat consequences of precipitation. Too many balls in the air at one time for this old head.
James! I am puzzled how your answer ended up before my posting here, but I am glad that we seem to agree!
It appears that no testing has been done in the manner that we both would like to have seen it done.
In addition, I should tell you that they recently discovered that there is also absorption of CO2 in the UV region… I think this makes it even more complicated….so it also acts a bit like ozone….