Prev  1  2  3  4  5  6  7  Next

Comments 126 to 150 out of 173:

126. RW1 at 13:22 PM on 21 December, 2010
     scaddenp (RE: Post 124), The 3.7 W/m^2 is the correct amount of increase in radiative forcing from a doubling of CO2 in the context your describing, but it's assuming all of the absorbed 3.7 W/m^2 affects the surface - meaning all of it is re-radiated downward, instead of only half. In order for half to be 3.7 W/m^2, the total absorbed power would need to be 7.4 W/m^2, which it isn't. They've gotten away with this because technically all the absorbed 3.7 W/m^2 of power is "radiatively forced" - it's just that about half of it happens to be "forced" in the same in the same direction it was already going - up out to space. Also, if they assume all of the power affects the surface, they can get more warming.
127. Eric (skeptic) at 13:53 PM on 21 December, 2010
     RW1, you already answered my question in #5: "The average incident solar energy is about 340 W/m^2. If you subtract the effect of the earth’s albedo (about 30% or 0.3 = 102 W/m^2), you get a net incident solar energy of about 238 W/m^2 (340 – 102 = 238)." That matches the Trenberth diagram. Now I am ready to try to understand the meaning and ramifications of the "gain" of 1.6 (390 / 238). Unfortunately it is also bedtime, so I will look at that tomorrow
128. RW1 at 13:54 PM on 21 December, 2010
     Eric (RE: Post 125), I think Trenberth is just starting with an average surface temperature of 289K rather than my 288K. I was also using an average solar input of 340 W/m^2 - Trenberth using 341 W/m^2. My 238 W/m^2 is derived by subtracting out an albedo of 0.3, which equals 102 W/m^2 (340 x 0.3 = 102; 340 - 102 = 238 W/m^2). Trenberth is also showing 102 W/m^2 reflected (23 off the surface, the other 79 off the clouds). Many have said Trenberth's diagram is confusing because he doesn't separate out clear sky from cloudy sky, which behave quite differently from one another. Also, some of the incoming energy not reflected off of clouds is absorbed by the clouds and some makes it through to the surface. What exactly Trenberth is referring to with the 78 W/m^2 being absorbed by the atmosphere is unclear. I think a lot of his numbers are being determined ad hoc. This isn't hard to do because the the surface power is known from average surface temperature, and outgoing power is known from the effective temperature of the earth of about 255K as seen from space. With these two knowns, many theoretical energy flow models can be derived.
129. RW1 at 13:57 PM on 21 December, 2010
     Eric (RE: Post 127), Yeah, I tried to lay out everything as detailed as I could in post 5.
130. muoncounter at 14:44 PM on 21 December, 2010
     #126: "it's just that about half of it happens to be "forced" in the same in the same direction it was already going - up out to space." You have said a number of times that your calculations require cutting the radiative forcing in half because of this lost to space idea. I'm genuinely curious to know where that concept originated. Let's try a 'thought experiment'. Suppose a quantity of IR photons are on their way up from the warm ground. Some of these photons get absorbed by GHGs. Reradiation takes place and exactly 50% go downwards and 50% go upwards. In this thought-world, there are only either upgoing or downgoing, no 'tweeners'. Of the ones that go downwards, if your mechanism is correct, they return to the ground and are no longer part of this experiment. If your mechanism is correct, the remainder are gone. But let's look at the future of the photons that continue upwards upon re-radiation. Is it not possible for a 2nd absorption to occur, as these up-going photons meet other GHGs? If so, we repeat the partitioning into half down (and they are no longer part of this experiment), half up. These upgoers meet more GHGs and are again reabsorbed/reradiated. Why can this process not continue many, many times? Let's call the probability of any one photon being absorbed in a single stage of this cycle P. If N₀ photons start up, after the first 'stop', there are N₁ = (1 - P)N₀ + 0.5PN₀ still going up -- all of the ones that didn't get absorbed plus half of those that did. We can calculate the total number of ups left after a large number of iterations. For P=0.01, it takes just over 900 iterations to reduce the number of upgoing photons to 1% of the initial quantity. With P=0.001, it takes just over 9000 iterations. And in our thought-world, you're either going up or going down. So 99% of the original amount are returning to the ground. Now I have no idea what a reasonable value for P should be, nor do I know if there should be a max number of iterations, nor do I expect this 50/50 scenario to resemble reality. In addition, we should calculate the fate of the downgoing photons from each iteration using the same rules. But I'm not ready to do that until you agree that your single shot, 50% Lost-In-Space idea doesn't resemble reality either.
131. KR at 15:14 PM on 21 December, 2010
     RW1 - Your bookkeeping is off. 3.7W/m^2 is the forcing from doubling CO2 at TOA, not the surface effect. That TOA number already includes all internal re-radiation. You've been told this repeatedly - I don't know why you keep insisting on half that forcing not having an effect; you are consistently (and in an unsupportable fashion) underestimating the CO2 effect by half, and you are consistently incorrect. The '1.6 gain' for solar inputs is also you have mentioned is something I don't understand - the reaction to forcings is specifically describing equivalent inputs to the Earth energy balance, and there is no 1.6 factor anywhere I know of. Hence much of your #5 post here does not follow. As to Trenberth 2009 (you seem to be using numbers from an earlier version, but they aren't all that different), Trenberth puts quite a lot of effort into estimating the various components. If you feel he has not estimated one of the energy vectors correctly, please point out which one(s), with some evidence to back your claim(s). Preferably backed by some papers indicating why.
132. RW1 at 16:27 PM on 21 December, 2010
     muoncounter (RE: Post 130), Actually, the re-radiation from GHGs is in all directions (half goes more upward, half goes more downward, some goes more sideways). Only the downward going half can affect the surface. It may seem logical that multiple absorptions on the way up could cause more than half the power to affect the surface, but if this is true, it also would mean that multiple absorptions on the way down could cause half to be redirected back up out to space - equally offsetting any redirected back down. Whatever happens exactly, if you run some numbers, the net result shows that it's about half up and half down. For example at a temperature of 288K, the surface emits 390 W/m^2. With a gain of 1.6 at the surface, the amount power absorbed by the atmosphere and sent back toward the surface is 150 W/m^2 (238 W/m^2 from the Sun + 150 W/m^2 from atmosphere = 390 W/m^2 at the surface). To calculate the amount of power absorbed by the atmosphere and directed up out to space, we need to know how much of the surface power passes through the transparent window of the atmosphere totally unabsorbed. If we use Trenberth's 70 W/m^2, we get a total of 320 W/m^2 absorbed by the atmosphere (390 - 70 = 320 W/m^2). 320 W/m^2 total absorbed - 150 W/m^2 directed downward back toward the surface = 170 W/m^2 upward out to space, which using Trenberth's numbers at least, is actually about 53% up and 47% down.
133. RW1 at 16:39 PM on 21 December, 2010
     muoncounter (RE: Post 130), I'm sorry, it's actually about 152 W/m^2 absorbed and sent down to the surface - not 150 W/m^2 (238 + 152 = 390 W/m^2). So that makes it 152 W/m^2 down and 168 W/m^2 up or about 52.5% up and 47.5% down (using Trenberth's numbers at least).
134. archiesteel at 16:40 PM on 21 December, 2010
     @RW1: "I think VeryTallGuy can respond for himself." I'm not responding for VTG, I'm commenting on your poor appraisal of his knowledge - considering he actually understands the science, and you clearly don't. As others have said, the 4 W/m^2 already considers the omnidirectional emissions of CO2. You keep ignoring it, as well as the very strong rebuttals to your strange theories. When someone keeps repeating the same thing over and over again and ignoring rebuttals, it's a clear sign that they've lost the argument, and are only keeping at it to either save face or waste everyone's time. You've stated your opinion, many times. People have presented their counter-arguments. What do you say we let posterity decide who is right, and who is wrong? Anyway, it's not as if your approximate grasp of the matter is going to convince anyone here...
135. Tom Dayton at 16:46 PM on 21 December, 2010
     No, RW1, you are incorrect that "multiple absorptions on the way down could cause half to be redirected back up out to space - equally offsetting any redirected back down." That's because: (1) The source of the radiation being absorbed is below the absorbing GHGs (on the surface). So there are far more GHG molecules to intercept radiation on its way up, than radiation on its way down. (2) Energy absorbed as radiation by GHGs mostly is transformed into kinetic energy by conduction with other molecules, most of which don't radiate that acquired energy. So much of the intercepted radiation's energy is removed from the radiation-to-space pathway, instead contributing to temperature rise of the gases.
136. RW1 at 17:08 PM on 21 December, 2010
     In my example above, power in = power out. 168 W/m^2 absorbed and radiated upward out to space + 70 W/m^2 passing through the transparent window unabsorbed out to space = 238 W/m^2 leaving & 238 W/m^2 arriving.
137. VeryTallGuy at 17:32 PM on 21 December, 2010
     RW1 @119 I'm afraid my life is too short, but also the answer is too simple. I've pointed out on several posts (as have others eg KR@131) that 3.7 W/m2 is the top of the atmosphere number. You keep on trying to halve it by claiming that it is something else. It's not. 3.7 is the total increased heat absorbed by the earth's system for a doubling of CO2 - the net reduction in radiation to space. Absorption and re-emission through the atmosphere are inherent in the calculation which is done stepwise through the atmosphere. If you want to calculate the surface budget associated, feel free. Also, you asked for a response to your original question. I tried directly to do that @112 - even with the very conservative figures I put in there you can see that the energy change from CO2 is bigger than your figures for orbital eccentricity within 2 years. And you still haven't provided any reference for your numbers on orbital forcing, unless I missed them. Please do?
138. scaddenp at 20:53 PM on 21 December, 2010
     " but it's assuming all of the absorbed 3.7 W/m^2 affects the surface - meaning all of it is re-radiated downward, instead of only half. " As others have pointed out, this is not true. The calculation used to arrive at 3.7W/m2 assume nothing of the kind and physically the situation is different. The number cannot not be used in the way you describe. See the definition in 2nd IPCC report. Essentially the same set of equations are used to calculate the added energy flux at the surface due to increased but its different no. From memory its about 3.5W/m2 for current GHG emissions since pre-industrial but I dont know the figure for doubling.
139. Eric (skeptic) at 22:43 PM on 21 December, 2010
     RW1 (#132), thanks for explaining your numbers again. What doesn't seem to match Trenberth is the 80W/m^2 lost by evaporation (cooling) at the surface (plus another 17 for thermals). In your budget you only consider the energy radiated from the surface. Can you adjust your budget account for evaporation and thermals? Also like KR in 131 I am a little unclear on what you mean by "gain". You are saying that a certain amount of solar energy makes it to the atmosphere and surface (in Trenberth it is 341-79-23 which is about the same as your #'s) Then we measure the earth at 288K and calculate 390W emitted. You then define gain as the ratio of the solar energy caught in the earth/atmosphere (ok...) divided by surface radiation (doesn't make sense). Seems to me like you are comparing two fundamentally different numbers.
140. VeryTallGuy at 06:42 AM on 22 December, 2010
     From the invariably excellent Science of Doom the 3.7 W/m2 is defined:

     "The change in net (down minus up) irradiance (solar plus longwave; in W/m2) at the tropopause after allowing for stratospheric temperatures to readjust to radiative equilibrium, but with surface and tropospheric temperatures and state held fixed at the unperturbed values."

     Note

     "the stratospheric adjustment is minor"

     so it's essentially the same as a top of atmosphere calc. Interestingly as noted in their post, applying this to the surface temperature does NOT seem to result in the 1.2 degrees warming: From the Trenberth link above: 1) radiative flux at the surface = 396W/m2 - equates to 289.09K blackbody temperature 2) Add 3.7 to that raises temperature to 289.76, so 0.65 degC temperature rise. 3) In order to get a 1.2 degC rise at the surface you need a heat flux increase to 402.6W/m2, so 6.6W/m2 at the surface. I'm not exactly sure how that calc is done to translate 3.7W/m2 TOA to 6.6 at surface, although you'd expect it to be larger so it seems about right. I can't find a reference for this calc - can anyone help? Are my sums right?
141. Riccardo at 09:30 AM on 22 December, 2010
     VeryTallGuy when you increase emission at the surface by increasing surface temperature you won't get the same excess energy leaving the planet at TOA, part of it will be absorbed by the atmosphere. To balance a forcing at TOA you need a larger temperature increase then predicted by this simple calculations. Basically, this is the same mistake made by RW1 before.
142. RW1 at 09:55 AM on 22 December, 2010
     Eric (RE: Post 139), Trenberth is just listing evaporation and thermals for reference purposes - neither actually contributes to the radiative budget and/or balance. It's just one more confusing and ambiguous component of that diagram. BTW, if you don't believe me or want to check yourself, run all the numbers he lists - the 80 W/m^2 for evaporation and 17 W/m^2 aren't included in the total radiative flows to achieve power in = power out.
143. RW1 at 10:34 AM on 22 December, 2010
     VeryTallGuy (RE: Post 137), Let's take this step by step: 3.7 W/m^2 is the total absorbed or captured power for a doubling of CO2, correct? If not correct, then your saying the total absorbed power is 7.4 W/m^2? Some other amount? I've read much of the IPCC reports and I've been studying this issue for quite a while now - nowhere have I seen that the total captured power from a doubling of CO2 is 7.4 W/m^2 for a net 3.7 W/m^2 because only half of the absorbed power goes down. Where and in what way specifically does the IPCC, or any other climate research paper or document, say this? Also, what you are describing above regarding the 4 W/m^2 increase at the TOA is the total amount of increased radiation to space that will occur to achieve equilibrium, assuming there is 4 W/m^2 increase in power at the surface. However, that is only possible if all the absorbed 4 W/m^2 of power is directed toward the surface instead of only half. If it's only half, the "net change in power emitted at the top of the atmosphere" would only be 2 W/m^2. What I'm getting at is the question boils down to what the total absorbed power is. Again, you're saying the total absorbed is about 8 W/m^2 for net of 4 W/m^2 because only half can affect the surface, correct? My orbital forcing reference is from Wikipedia, which I checked against a few other sources. According to them the range is 1,413 – 1,321 W/m^2 perihelion-aphelion. Divide by 4 to get the average, which is a little over 20 W/m^2 (actually 23). Subtract the Earth's albedo of about 0.3 and it's a net increase of 14 W/m^2 at perihelion. Also, I didn't say or imply there was an average increase in radiative forcing from orbital eccentricity. As stated before, I'm well aware that the increase from CO2 is on top of the current average total.
144. Eric (skeptic) at 11:02 AM on 22 December, 2010
     RW1, thanks for the reply. Ignoring evaporational cooling for now, I think what you were trying to say in #61 is that a particular amount of solar energy absorbed in the atmosphere and on the surface (238 W/m^2) turns into 390 W/m^2 of surface radiation or a "gain" of 1.6 You then stated 1) that an increased radiative forcing in the system (atmosphere plus surface) would produce the same ratio of surface radiative increase (i.e. the gain again). And 2) the 3C rise in temperature postulated for the doubling of CO2 would produce a 12 W/m^2 increase in surface radiation by applying S-B to the delta T. And 3) 12 divided by 1.6 is too large for CO2 to produce. Statement (2) seems correct. But (1) means that the gain is always the same whether dealing with the full amount of solar forcing or a delta in solar forcing or a delta in CO2 forcing. I definitely agree that the "gain" should be the same whether for a delta in solar or a comparable delta in CO2. But gain is probably not a constant over the range of solar forcing. The "3C" proponents would have to show that gain is larger at the pre-industrial equilibrium than over the entirety of solar forcing, and I don't think it's hard to argue that gain is nonlinear with warming since water vapor is highly nonlinear. With a larger gain, they can argue that the relationship in (3) holds. In fact your analysis brings to mind a similar problem I have with the paleo sensitivity analysis. There is an assumption that the temperature to CO2 relationship in going from a frozen planet to unfrozen is the same as from unfrozen to slightly warmer unfrozen. Both your analysis and paleo one here detailed-look-at-climate-sensitivity.html seem to use the same basic but faulty assumption that forcing-to-temperature elationships over colder ranges of climate are applicable to warmer ones.
145. RW1 at 11:48 AM on 22 December, 2010
     Eric (RE: Post 144), The amount of power from the Sun that hits the surface and is re-radiated as LW infrared is about 238 W/m^2. However, the total power at the surface is 390 W/m^2 - not 238 W/m^2, because GHGs and/or clouds are absorbing and re-radiating some of that 238 W/m^2 back toward the surface, which in effect, is delaying or slowing down the release of the 238 W/m^2, causing the surface to be warmer than it would be; or causing the surface power flux to be 390 W/m^2 instead of 238 W/m^2. The gain represents the increase in surface power or increase in surface temperature as a result of there being GHGs and clouds in the atmosphere. In effect, the gain factor of 1.6 means that due to the greenhouse effect, it takes about 1.6 W/m^2 of power at the surface for each 1 W/m^2 of power to leave the system, offsetting each 1 W/m^2 entering the system from the Sun.
146. scaddenp at 12:03 PM on 22 December, 2010
     "3.7 W/m^2 is the total absorbed or captured power for a doubling of CO2, correct?" NO! It is not. 3.7W/m2 is the equivalent radiative forcing you would get from double CO2. eg. Doubling CO2 would give you the same impact say a solar forcing of 3.7W/m2. This confusion and insistence on halving it is getting in the way. All of the absorption, re-emission in all directions, re-absorption etc etc has to be done in the complex RTE codes. (eg you can find a MODTRAN calculator here). Net result is an intensity out which is used to calculate the radiative forcing. "power" is also a slightly confusing term to use - usually used in context of energy conversion. Here we are talking about an energy flux.
147. RW1 at 12:15 PM on 22 December, 2010
     Eric, @Eric 144: "You then stated 1) that an increased radiative forcing in the system (atmosphere plus surface) would produce the same ratio of surface radiative increase (i.e. the gain again). And 2) the 3C rise in temperature postulated for the doubling of CO2 would produce a 12 W/m^2 increase in surface radiation by applying S-B to the delta T. And 3) 12 divided by 1.6 is too large for CO2 to produce." No, not quite. I'm saying the 3 C rise requires an increase in surface power of 16 W/m^2 for a gain of 8 (8 x 2 W/m^2 = 16 W/m^2), which is 5 times the 3.2 W/m^2 increase in the surface power from each 2 W/m^2 coming in from the Sun. The AGW theory of a 3 C rise in temperature requires the system to respond to each 1 W/m^2 of power from increased CO2 5 times more powerfully than each 1 W/m^2 of power coming in from the Sun.
148. Eric (skeptic) at 12:43 PM on 22 December, 2010
     RW1, the sun, measured by TSI changes in the historical measurements and proxies, increased by about 0.5 W/m^2 from the depths of the Little Ice Age to about 1900, see fig. 1 in A-detailed-look-at-the-Little-Ice-Age.html The temperature increase, which also involved other factors, was at least 0.5C, maybe more like 1C. With no other factors considered the "gain" is something like 2.5 to 5W/m^2 divided by 0.5 which is 5 to 10, rather than 1.6 The problem, I believe, is you are calculating gain with full solar input (zero to current day) which will yield a much smaller result than a delta of solar input as I demonstrated, albeit crudely, using the LIA.
149. RW1 at 13:03 PM on 22 December, 2010
     Eric, Getting back to the perihelion point, here it is from a different angle: Let's say the total average incident solar power increases from 340 W/m^2 to 343 W/m^2 as a result of the earth's orbit moving closer to perihelion. This results in a new, higher net incident solar energy of 240 W/m^2 (343 x 0.3 albedo = 103, 343 -103 = 240), which is an increase in radiative forcing of 2 W/m^2 (240 W/m^2 - 238 W/m^2 = 2 W/m^2) - the same as from a doubling of CO2. If according to the AGW theory, the system's response will be to greatly amplify the additional 2 W/m^2 from CO2 to about 16 W/m^2 via large positive feedbacks, why doesn't the system do it with the same 2 W/m^2 increase in radiative forcing from from the Sun? The observed temperature changes are nothing anywhere near 3 degrees C for this additional 2 W/m^2 of solar power. Even better, let's take the last 3 W/m^2 increase that occurs at peak perihelion (347 W/m^2 to 350 W/m^2 for a net of 2 W/m^2 albedo adjusted). The system doesn't respond by amplifying that last 2 W/m^2 8 fold, but somehow it's all of the sudden going amplify the next 2 W/m^2 from C02 8 fold? Again, does it make physical and/or logical sense that the system is somehow all the sudden going to treat such a small increase radically differently than it does both the last 0.5 percent and the original 99+ percent?
150. RW1 at 13:21 PM on 22 December, 2010
     Eric, Check out this more detailed explanation and satellite analysis of these things by physicist/climatologist and originator George White: http://www.palisad.com/co2/eb/eb.html I've never seen the information and analysis he presents here refuted anywhere, and I've seen many try and fail totally. It's the single most damning piece of evidence against AGW that I've ever seen. I also don't think it's a coincidence that G. White's sensitivity estimate is about the same as what Lindzen and Choi are getting - albeit via somewhat different methodology.

Prev  1  2  3  4  5  6  7  Next

Post a Comment

Political, off-topic or ad hominem comments will be deleted. Comments Policy...

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.