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Post by itsthesunstupid on Oct 16, 2009 9:23:38 GMT
The 3.7wm-2 figure takes into account the radiative properties of water vapor. It's a comparison between two atmospheres A and B where: A) Is identical to our atmosphere B) Is identical to our atmosphere but for one difference - double the co2. Temperature is the same as A, cloud amount is the same as A, humidity is the same as A. But B has twice as much co2 in the atmosphere than A. One way of looking at it is that B is our atmosphere if co2 level was instantly doubled, before the surface temperature, clouds, etc can change in response. Calculating the difference in outgoing radiation between A and B only requires calculating the radiative changes caused by the presence of the extra co2. It doesn't require needing to knowing how the climate will respond - ie how clouds will change, how water vapor will change, ie feedbacks. This is why the 3.7wm-2 figure can be pinned down. How the climate responds to the 3.7wm-2 reduction in outgoing radiation determines the temperature change that will cause. But the 3.7wm-2 figure is a significant imbalance caused by doubling co2, therefore the climate response must be significant whether or not temperature increases much. Ok, so it is a theoretical value, verses an emperical value. And the theoretical value is done using a slab. I understand the reasoning behind unsing a slab to obtain the 3.7W, but it would appear in reality that the 3.7 will not hold up to scrutiny. So, that gets us to sensativity......right? And the best paper I have read on that to this point is Lindzen's paper......which indiates what... .3C? potential realisitically? In other words, it's another one of those meaningless threads upon which AGW theory is hanging and it too is easily snipped away. No wonder the AGW crowd mocks the idea of the USCofC trial on climate change. If this board is any indication of which side has the stronger argument, AGW would be sentenced to death. Even if it took the form of a civil trial where awards are based on the preponderance of evidence and then prorated, AGW would lose BIG TIME.
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Post by glc on Oct 16, 2009 11:23:59 GMT
In other words, it's another one of those meaningless threads upon which AGW theory is hanging and it too is easily snipped away.
No it's not a "meaningless thread".
The 3.7 w/m2 is the additional forcing due to doubling the concentration of CO2 in the atmosphere. The forcing is calculated using radiative transfer equations which are based on well established physics (i.e. Planck, Beer Lambert). The equations determine the transmission/absorption of IR energy through the atmosphere.
The reason that we can't easily show how the 3.7 w/m2 value is calculated is because there are literally tens of thousands of separate calculations involved and the only way this can be done is by using a computer program, e.g. MODTRAN. There is, however, a simple relationship (Myhre et al) which can be used, i.e.
Forcing = 5.35 x ln(C1/C0)
Where C0 is the initial CO2 concentration and C1 is the final concentration. For a doubling F = 5.35 x ln (2) =~3.7 w/m2
This result is relatively uncontroversial. Richard Lindzen, for example agrees with it. The question is, though, how much warming will the 3.7 w/m2 forcing produce.
It's fairly easy to show, by using a simple, single-layer energy balance model (I've done it on this blog), that temperatures would increase by ~1.2 deg. Again most climate scientists agree with this - again including Richard Lindzen. But this figure does not take into account possible feedbacks (positive or negative) and this is where the debate begins. This is the issue of Climate Sensitivity (CS). If there is no feedback then CS is ~0.3 deg per w/m2 (i.e. 1.2/3.7) and AGW is probably not going to be a problem. If there is a strong positive feedback then CS might be as much as 0.75 deg per w/m2 in which case we probably do have a problem.
As you can guess, most pro-AGW scientists believe that there will be a strong positive feedback. Their reasoning is that the initial CO2 warming will increase the rate of evaporation from the earth's surface which will in turn increase the concentration of water vapour (WV) in the atmosphere (note a warmer atmosphere can hold more moisture). As WV is also a ghg this is expected to add to the ~1.2 deg CO2 warming.
Other scientists, e.g. Richard lindzen, believe that any feedback will be low (or negative in the case of RL). If RL is correct then the actual warming will be less than the ~1.2 deg from CO2 alone.
Me? - I'm nearer to RL than the AGWers. I tend to think wv 'regulates' rather then warms or cools. Not very scientific but my guess is as good as anyone else's and I reckon we'll be about 1 deg warmer at 600 ppm than we were at 300 ppm.
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Post by jimcripwell on Oct 16, 2009 14:18:54 GMT
glc writes "No it's not a "meaningless thread". "
I disagree. I am still looking for a reference that proves that using radiative transfer models is a suitable way to estimate radiatve forcing. I agree that the calculations you describe have been accurately done according to the laws of physics. The question is whether these particular laws apply in this case, or whether they have, in fact, been misapplied.
This reminds me of the difference between astronomy and astrology. Both use the same sort of data from the stars and planets, and do all sorts of complex mathematics on them. The numbers derived from astronomical calculations have scientific meanings. I would suggest that those derived from astrological calculations are scientificly meaningless.
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Post by glc on Oct 16, 2009 15:37:51 GMT
I disagree. I am still looking for a reference that proves.....
Aaargh! Where did you suddenly spring from, Jim? Just when I thought it was safe to discuss radiative transfer equations again -up you pop. Do you have some sort of sixth sense?
I agree that the calculations you describe have been accurately done according to the laws of physics. The question is whether these particular laws apply in this case, or whether they have, in fact, been misapplied.
There is always the possibility that, for a variety of reasons, the laws have been "misapplied". It could be that increasing CO2 makes not one jot of difference to the earth's climate because of some yet to be understood mechanism which kicks in and offsets the CO2 effect. But how long do you wait to find out? We know CO2 absorbs IR radiation and with our current, if perhaps limited knowledge we can take a reasonable stab at the expected warming. If we were studying the effect on Mars or Venus we could take as long as we wished to form a conclusion but it's not. As it happens I don't think they'll be too much of a problem but I can understand the views of those who wish to adopt the precautionary approach.
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Post by jimcripwell on Oct 16, 2009 16:08:49 GMT
glc writes "There is always the possibility that, for a variety of reasons, the laws have been "misapplied"."
As always, you are avoiding the real issue. So far as I am concerned the proponents of AGW have an onus to show that their methodology is correct. It is not up to the skeptics to show that the methodology MAY not be correct. This is why I keep on asking for a reference to prove that radiative transfer models are suitable to estimate radiative forcing. And since this has not been done, and no reference is available, you and socold studiously avoid the issue. Where is my reference, or what is your logic as to why no reference is required?
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Post by steve on Oct 16, 2009 17:07:51 GMT
glc writes "No it's not a "meaningless thread". " I disagree. I am still looking for a reference that proves that using radiative transfer models is a suitable way to estimate radiatve forcing. I agree that the calculations you describe have been accurately done according to the laws of physics. The question is whether these particular laws apply in this case, or whether they have, in fact, been misapplied. This reminds me of the difference between astronomy and astrology. Both use the same sort of data from the stars and planets, and do all sorts of complex mathematics on them. The numbers derived from astronomical calculations have scientific meanings. I would suggest that those derived from astrological calculations are scientificly meaningless. The dependency of astronomy on radiative transfer theory makes that last paragraph rather ironic.
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Post by socold on Oct 16, 2009 17:58:33 GMT
The 3.7wm-2 figure takes into account the radiative properties of water vapor. It's a comparison between two atmospheres A and B where: A) Is identical to our atmosphere B) Is identical to our atmosphere but for one difference - double the co2. Temperature is the same as A, cloud amount is the same as A, humidity is the same as A. But B has twice as much co2 in the atmosphere than A. One way of looking at it is that B is our atmosphere if co2 level was instantly doubled, before the surface temperature, clouds, etc can change in response. Calculating the difference in outgoing radiation between A and B only requires calculating the radiative changes caused by the presence of the extra co2. It doesn't require needing to knowing how the climate will respond - ie how clouds will change, how water vapor will change, ie feedbacks. This is why the 3.7wm-2 figure can be pinned down. How the climate responds to the 3.7wm-2 reduction in outgoing radiation determines the temperature change that will cause. But the 3.7wm-2 figure is a significant imbalance caused by doubling co2, therefore the climate response must be significant whether or not temperature increases much. Ok, so it is a theoretical value, verses an emperical value. And the theoretical value is done using a slab. I understand the reasoning behind unsing a slab to obtain the 3.7W, but it would appear in reality that the 3.7 will not hold up to scrutiny. It does hold up to scrutiny. Radiative physics is advanced enough to give great precision on the question of how much outgoing radiation would be reduced by the moment after an instantaneous doubling of co2. Of course it cannot be reduced by 3.7wm-2 permanently, the planet will adjust to regain equilibrium. And therefore we come to the question of climate sensitivity. To get just 0.3C warming from a 3.7wm-2 reduction in energy loss, you need something else to change significantly instead - say clouds - in fact isn't that Lindzen's explanation? In any case something will significantly shift in the earth's climate if you double co2. It can't simply "stay the same" because staying the same means a 3.7wm-2 reduction in energy loss and such a thing cannot be maintained indefinitely for obvious reasons. Either cloud cover has to increase significantly to reduce absorbed energy, or temperature has to rise significantly to increase emitted energy. But the idea that doubling co2 has "little effect" on the climate is falsified by it's significant radiative forcing.
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Post by icefisher on Oct 16, 2009 21:34:39 GMT
In other words, it's another one of those meaningless threads upon which AGW theory is hanging and it too is easily snipped away.No it's not a "meaningless thread". The 3.7 w/m2 is the additional forcing due to doubling the concentration of CO2 in the atmosphere. The forcing is calculated using radiative transfer equations which are based on well established physics (i.e. Planck, Beer Lambert). The equations determine the transmission/absorption of IR energy through the atmosphere. I have raised the question of clouds on this and never received a response. Clouds are dynamic and with no cloud model I don't see how any modeling of radiative transfer could be even close to being correct. For example, if you merely assume 70% of the planet has cloud cover, this still ignores perhaps the most important dynamic element of clouds is how they form on convective fronts and how they move exposing cold land they initially shaded while moving over warm land down current from their formation area. Its almost as if clouds feed on the warmth in the atmosphere so how can any radiative transfer hope to come up with a correct forcing without modeling clouds. Convince me how and maybe I'll bite; but otherwise I think its a bit like being a fish eating it all hook, line, and sinker.
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Post by Pooh on Oct 17, 2009 4:28:51 GMT
icefisher: I think even an IPCC Working Group agrees with you: Cloud Modeling is a major shortcoming in the models. At risk of referring you to something already familiar, perhaps one of these may be useful: Lindzen, , Ph.D. , Richard, and Yong-Sang Choi. “On the determination of climate feedbacks from ERBE data.” Geophysical Research Letters Pending (July 14, 2009). www.leif.org/EOS/2009GL039628-pip.pdf. Lindzen, , Ph.D. , Richard, Anthony Watts, and Yong-Sang Choi. “New paper from Lindzen demonstrates low climate sensitivity with observational data .” Watts Up With That? wattsupwiththat.com/2009/07/23/new-paper-from-lindzen/. Lindzen, Richard S., Ming-Dah Chou, and Arthur Y. Hou. “Does the Earth Have an Adaptive Infrared Iris?.” Bulletin of the American Meteorological Society 82, no. 3 (March 1, 2001): 417-432 . dx.doi.org/10.1175%2F1520-0477%282001%29082%3C0417%3ADTEHAA%3E2.3.CO%3B2. Lindzen, Richard, PhD. “Lindzen on negative climate feedback (with updates).” Blog. Watts Up With That?, March 30, 2009. wattsupwiththat.com/2009/03/30/lindzen-on-negative-climate-feedback/“Svalgaard Solar Theory « Climate Audit.” www.climateaudit.org/?p=2470“Svalgaard #3 « Climate Audit.” www.climateaudit.org/?p=2679“Svalgaard #4 « Climate Audit.” www.climateaudit.org/?p=2868
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Post by glc on Oct 17, 2009 10:45:39 GMT
icefisher: I think even an IPCC Working Group agrees with you: Cloud Modeling is a major shortcoming in the models. At risk of referring you to something already familiar, perhaps one of these may be useful:
Everyone agrees about the cloud issue. There is uncertainty but that is not a reason for the whole AGW theory to be ignored or dismissed. Cloud variability is a given but a number of sceptics seem to be relying on the fact that clouds may come to the rescue. They might - but then again they might not. We have not yet got sufficient evidence to say either way. Cloud variability is tied up with wv feedback which some think will be positive others think negative.
There is nothing wrong with considering all possibilities. But, the fact is that, if all other factors remain the same, doubling the CO2 concentration is likely to warm the earth by about 1 deg. That shouldn't be a problem. But there's a strong possibility that all other factors will not remain the same. Other factors could act to
1. Enhance the warming 2. Reduce the warming
There's your "uncertainty". It's your call. But remember this is not an experiment on another planet.
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Post by jimcripwell on Oct 17, 2009 11:30:38 GMT
glc writes " But, the fact is that, if all other factors remain the same, doubling the CO2 concentration is likely to warm the earth by about 1 deg."
Once again we see this scientific nonsense. socold keeps on repeating it as well. Just because it is repeated over and over again, does not make it correct. The 1 C rise in temperature as well as the 3.7 wm-2 change in radiaitve forcing for a doubling CO2 are both hypothetical numbers which can never be measured. They are based on the output of non-validated computer programs.
There is absolutely no evidence that radiative transfer models are suitable to estimate radiative forcing. I keep asking for a reference that proves that the physics behind radiative transfer models is capable of estimating radiative forcing. All I get is silence. Presumably because trying to use radiaitve transfer models for this purpose is simply scientific garbage, and no such reference exists. The usual warmaholics smoke and mirrors.
glc, when will you address my query for this reference?
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Post by enough on Oct 17, 2009 12:03:04 GMT
The 4 watt forcing myth.
Reference:
Atmospheric Radiation, Theoretical Basis R M Goody
ISBN -019-510291-6
The source of the atmospheric IR plots that everyone uses.
Quote, page 220
"The comment is relevant to an implicit assumption in much of the current literature: that more and more detailed physics encoded into larger and larger computers will eventually yield accurate weather and climate predictions. This is more an article of faith than an demonstrable proposition. It is also possible that the numerical complexity hides or introduces it own sources of error, in addition to making it impossible to penetrate the algorithms of another investigator."
Time and again I see reference to this 4 watt myth with no reference. Even in so called reviewed articles.
I have tracked down some GCM papers. The older which everything seems to be based on are unreadable while later ones all basically say: we ran this model compared to all the rest. In these the usual story is "all models are with in some percent but this on is better. Just like Soloman's comment of models being fantastic.
Looking for a reference that at least breaks up this 4 watt forcing in to its various components so I can at least begin to evaluate the number.
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Post by jimcripwell on Oct 17, 2009 13:34:00 GMT
enough writes "The 4 watt forcing myth."
Precisely. I wonder when people like glc and socold will wake up and realise that never before, in the whole annals of scientific history, has anyone claimed to have actually proved anything in physics, where the key, fundamental, numbers have never been, and can never be, measured experimentally.
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Post by steve on Oct 17, 2009 14:20:00 GMT
Here's the reference for the 3.7W/m^2 number. New estimates of radiative forcing due to well mixed greenhouse gases Gunnar Myhre et al GRL 1998 www.climateaudit.org/pdf/others/myhre.1998.pdf(largish pdf linked from McIntyre's site.) To save Jim's time, Jim thinks it's all a load of unscientific nonsense, though in my view he can't seem to separate a relatively straightforward application of radiative transfer theory (on which the whole of astronomy and a lot of engineering depends) to an atmospheric profile, from the more vexed question of the effect of feedbacks.
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Post by sigurdur on Oct 17, 2009 14:21:55 GMT
The whole basis of the validity of a 3.7 warming is models. That is the best that we have at this time. Everyone seems to agree that the actual warming would be 1.C or significantly less. OK.....lets look at what that 1.0C warming would do. It would bring us close to temps experienced, relying on proxie data of course, during the early Halocene period. Was that period a bad period for mankind? No...it wasn't. Some consider it a Golden Age. Warmth within historical normals is NOT man's enemy, cold is. Consider the slight increase in warmth during even the past 30 years. Ag production has increased, the intensity of hurricanes has decreased, weather as a whole worldwide has had fewer flucuations which have resulted in a more dynamic economy. Can anyone tell me what is wrong with this? ? The current cold snap in the US is only a reminder of what cooling does. And I don't like it one bit. There have been traffic deaths related to the early snow, huge crop losses appear to be verified, more carbon being emmited as the heat load requied to live above freezing has come so early. It boils down to what your internal fear is. Mine is NOT warming, as historically warmth has been worldwide good. Mine IS cooling, as historically, cooling brings droughts, famine, death and pestilence. I guess it amounts to what your choice is. Current science shows us that the warming, even with a doubling of co2, is not out of the normal climate variations. This brings us to the obvious answer: The AGW believers are puppets of the actual monied powers who desire a carbon tax, and hence, a way to trade a life required gas, so that money can be made. All one has to do is follow the money trail. Government desires more tax revenue, funds studies to alarm people. Traders have figured out how to get part of that revenue stream so they fund studies to alarm people. It is all about alarm. I have not read a study recently that discusses what a colder outlook would provide. That.......would be reallllllllly alarming would it not?
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