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Post by poitsplace on May 30, 2009 10:47:19 GMT
For what it's worth I sort of agree with GLC in that I think it's perfectly reasonable to expect a TOTAL rise of about 1.2C (about .5 to .7C more ) by 2100. I make absolutely no claim that CO2 is the source of this warming...but it's been warming and the climate has been warmer before so *shrug* why not. I'm also pretty sure the feedbacks are at MOST very low and quite probably negative overall.
However, unlike most AGW proponents I think it's completely possible temperatures could drop at almost the same rate they rose...especially if this is indeed a grand minimum. Of course, I doubt the minimum would contribute more than .4C to the drop though. It could be more. It could be less but .2 to .4C seems like a safe guestimate when temperatures have been rising anyway.
and finally...I don't think the warming is going to be remotely damaging. Cooling on the other hand will remind us why we call warm periods "optimums".
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Post by icefisher on May 30, 2009 11:22:38 GMT
There you go. 4 separate opinions all different.There aren't 4 separate opinions - there are 2, i.e. Low feedback v High feedback. You are trying to suggest there is wild disagreement where there isn't. Not wild disagreement? ? You just read perhaps an opinion for every possibility. No feedback, negative feedback, low positive feedback, high positive feedback. What did you leave out? Disagreement would not often get wilder than that. The only thing not mentioned is a belief that the GHG is implausible, but it did not rule out cooling. Something plausible isn't necessarily something that actually works that way. Despite attempts by amatuer bloggers to fudge the issue, there is a clear recognition among scientists (sceptic and pro-AGW) that increasing CO2 will result in a warmer world. How much warmer depends on feedbacks. The question is not whether the presence CO2 causes warming. That's been answered - It does. Whoaaa!!!!! Hold on a minute. Are you saying the causes of the last ice age would be overriden by CO2 and its feedbacks? Getting a little hysterical there bud! What you have instantaneously concluded is that any warming from CO2 will override natural variation. CO2 gloom and doom advocates just love to ride roughshod over that without so much as getting anywhere near understanding it. This is as stupid and ignorant as the projections that shellfish are going to dissolve away when in fact many of the phyla of shellfish evolved with CO2 concentrations many times what it is today. Before getting your panties in a wad about what scientists are really saying about CO2 you should actually read it. What I think most scientists agree about is that the Greenhouse theory of some forcing towards warming arising out of increases in GHG is plausible. Thats hardly an agreement that it is going to get warmer regardless of your overly simplified playground ball analogy.
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Post by jimcripwell on May 30, 2009 11:24:04 GMT
glc. You are avoiding an issue, which to me is fundamental if we are acting as scientists. You state, "Similarly, we know that doubling CO2 will increase the earth's temperature by ~1 deg C." I ask you for a reference for this statement. I ask for as peer reviewed paper which proves that this statement that this is true. All you seem to do is obfuscate. Surely there are two possibilities. The reference exists, and what you have claimed is correct. Or the reference does not exist, and your statement has no basis in science. Which is it? Or is it only me that believes in "Nullius in verbia"?
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Post by glc on May 30, 2009 16:49:23 GMT
Whoaaa!!!!! Hold on a minute. Are you saying the causes of the last ice age would be overriden by CO2 and its feedbacks?
No I'm not saying that. I have no idea why you imagine I did say it. In fact, I went to great pains to point out that CO2 warming could easily be offset by natural variability over short to medium timescales. I think I also suggested an underlying CO2 warming trend of ~0.05 deg per decade.
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Post by glc on May 30, 2009 17:55:18 GMT
glc. You are avoiding an issue, which to me is fundamental if we are acting as scientists. You state, "Similarly, we know that doubling CO2 will increase the earth's temperature by ~1 deg C." I ask you for a reference for this statement. I ask for as peer reviewed paper which proves that this statement that this is true. Jim
CO2 forcing is a calculation. Why would there be a peer reviewed paper to show that doubling CO2 leads to a forcing of ~3.7 w/m2. Do you also need a peer reviewed paper for a tripling or quadrupling. What you really seem the be looking for is the method behind the line by line calculations. MODTRAN performs these calculations which are verified by lab experiments and direct observations. MODTRAN produces the exact same emission spectrum (for given conditions) that is produced by satellite observations.
Can you confirm that this is what you're asking, i.e. you are questioning the calculations used to determine atmospheric transmittance and radiance.
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Post by icefisher on May 30, 2009 18:05:00 GMT
Whoaaa!!!!! Hold on a minute. Are you saying the causes of the last ice age would be overriden by CO2 and its feedbacks?No I'm not saying that. I have no idea why you imagine I did say it. In fact, I went to great pains to point out that CO2 warming could easily be offset by natural variability over short to medium timescales. I think I also suggested an underlying CO2 warming trend of ~0.05 deg per decade. And why would it have to be limited to short or medium timescales GLC? And in what context are you calling something short or medium (eons, eras, years, months?) I don't see Spencer using that kind of terminology yet you are trying to use him for support for such a notion. Spencer says GHG theory is a rational theory and it is NOT controversial to say it might cause less than 1 degree C warming. But "Not controversial" is not anywhere near proven, it just means its not a ridiculous notion. And less than 1 degree C could include a whole lot less. I think Jim Cripwell has you pegged. You are still living pre-Royal Society when Doctors still bled sick people to rid them of Black Bile. That is almost proof of the adage that folks not willing to study their history are condemned to relive it. You seem perfectly willing to relive it based on nothing more than some name dropping and a plausible theory.
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Post by jimcripwell on May 30, 2009 18:42:07 GMT
glc writes " Why would there be a peer reviewed paper to show that doubling CO2 leads to a forcing of ~3.7 w/m2. "
First, the quote I queried was that a doubling of CO2 results in a temperature rise of ~1 C, not a radiative forcing of 3.7 w/m2. So you have not provided a reference to this. Where is it? Second, this is where we left the last discussion. The value of 3.7 is based on the output of radiative transfer models. Nowhere has anyone shown that radiative transfer models are suitable to estimate radiative forcing. Radiative forcing is an extremely complex issue, which involves all 4 ways in which energy is transimtted through the atmosphere. I can see no a priori reason why a model that assumes that the only way to transfer energy is by radiation, is suitable to estimate radiative forcing. Where is the proof that radiative transfer models can properly estimate radiative forcing?
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Post by glc on May 30, 2009 18:43:10 GMT
And why would it have to be limited to short or medium timescales GLC? And in what context are you calling something short or medium (eons, eras, years, months?)Depends on the "natural factor". La Nina may impact over 1-2 years; volcanos 2-3 years; ocean oscillations up to ~30 years. Ice Ages are a different kettle of fish. If (more likely when) we get another ice age then CO2 concentrations will probably be irrelevant. However, we can't simply ignore the short term just because we might get an ice age in a few thousand years I think Jim Cripwell has you peggedDo you? Can you tell me what Jim's asking then? I don't see Spencer using that kind of terminology yet you are trying to use him for support for such a notion.What terminology? To be honest I think you're struggling with this. You're not making a lot of sense. That is almost proof of the adage that folks not willing to study their history are condemned to relive it. You seem perfectly willing to relive it based on nothing more than some name dropping and a plausible theory. The theory is more than just plausible. 1. CO2 absorbs LW IR radiation in selective wavelengths - that is a fact. 2. Increasing CO2 in the atmosphere will result in emissions form (on average) a higher level in the atmsphere - that is a fact. 3. To maintain the incoming=outgoing balance the atmosphere will need to warm - that is a fact. If you doubt the impact CO2 has please look at this link www.barrettbellamyclimate.com/page15.htmThis shows the deep 'trough' in the CO2 absorption band where emissions are from the lower temperature (higher altitude). That is a fact. The theory is not just plausible it is highly probable. Now if you have some scientific reason why CO2 cannot affect temperatures on earth - let's have it. Your reason would probably need to falsify one of the 3 'facts' listed above. I'm sorry but it's no longer good enough to keep saying it's "not proven" or it's "only plausible" because there are uncertainties. Roy Spencer knows fine well that the basic greenhouse theory is rock solid as he makes quite clear in his blog article "in defense of the greenhouse effect". The final 2 paragraphs of which are as follows: THE GREENHOUSE EFFECT WORKS…FOR NOW The greenhouse effect is supported by laboratory measurements of the radiative absorption properties of different gases, which when put into a radiative transfer model that conserves energy, and combined with convective overturning of the atmosphere in response to solar heating, results in a vertical temperature profile that looks very much like the one we observe in nature.
So, until someone comes along with another quantitative model that uses different physics to get as good a simulation of the vertical temperature profile of the atmosphere, I consider objections to the existence of the ‘greenhouse effect’ to be little more than hand waving.
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Post by icefisher on May 30, 2009 21:11:31 GMT
The theory is more than just plausible. Not sure what stage you are referring to. I have thought of the process first being a plausible theory and the next step is a proven theory. Is there something in between? Seems to me the only stuff in between is the stuff Jim Cripwell was talking about. . . .words and opinions speculating about the plausibility of the theory. 1. CO2 absorbs LW IR radiation in selective wavelengths - that is a fact. 2. Increasing CO2 in the atmosphere will result in emissions form (on average) a higher level in the atmsphere - that is a fact. 3. To maintain the incoming=outgoing balance the atmosphere will need to warm - that is a fact. I agree. In fact my minimum of .05 degrees per quadrupling of CO2 was actually based upon that notion using a rough approximation of the increased height of the atmosphere. So I covered your entire argument to this point. If you doubt the impact CO2 has please look at this link www.barrettbellamyclimate.com/page15.htmThis shows the deep 'trough' in the CO2 absorption band where emissions are from the lower temperature (higher altitude). That is a fact. I have no disagreement with that either. The theory is not just plausible it is highly probable. Now if you have some scientific reason why CO2 cannot affect temperatures on earth - let's have it. Your reason would probably need to falsify one of the 3 'facts' listed above. I'm sorry but it's no longer good enough to keep saying it's "not proven" or it's "only plausible" because there are uncertainties. Roy Spencer knows fine well that the basic greenhouse theory is rock solid as he makes quite clear in his blog article "in defense of the greenhouse effect". The final 2 paragraphs of which are as follows: THE GREENHOUSE EFFECT WORKS…FOR NOW The greenhouse effect is supported by laboratory measurements of the radiative absorption properties of different gases, which when put into a radiative transfer model that conserves energy, and combined with convective overturning of the atmosphere in response to solar heating, results in a vertical temperature profile that looks very much like the one we observe in nature.
So, until someone comes along with another quantitative model that uses different physics to get as good a simulation of the vertical temperature profile of the atmosphere, I consider objections to the existence of the ‘greenhouse effect’ to be little more than hand waving. Well thats just three more paragraphs of words without a single relevant new fact. (isn't that the modern definition of hand waving GLC?) I covered all that in my approximate .05C (range approximately .03 to .l08C) per quadrupling of CO2 (for earth that is). Now note carefully I said my model described a minimum forcing, not an increase or decrease in actual temperatures and it does not rule out the effect could be greater. But I do believe you can go so far and say a minimum of .03C to .08C per quadrupling as a minimum is a proven portion of the theory and I agree it could not be less without factoring in negative feedback as it gives full share to additional CO2 for containing heat in the atmosphere which I see to be a given. Now if you can start from there and provide details of how it could be warmer, complete with support, I am perfectly willing to listen and comment. But don't just rehash some tired old truths and then extend it beyond their share until such time you have established that additional share as fact.
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Post by icefisher on May 30, 2009 21:56:00 GMT
You must be aware that it's not possible to simply write down caclulations on a side of A4 to solve most real life problems. If we could solve everything analytically with a bit of calculus, then 80% of the world's physicists and mathematicians would be out of work. However, there are some simple Energy Balance Models which are relatively easy to understand and which give a reasonable approximation to the true forcing. If I remember where I've seen them I'll post the links. I think you hit the nail on the head there GLC. Seems to me one can easily develop mathematical models that mimic anything, then tell us the effect of doubling any variable. But thats not evidence the model is right.
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Post by glc on May 31, 2009 7:43:23 GMT
I think you hit the nail on the head there GLC. Seems to me one can easily develop mathematical models that mimic anything, then tell us the effect of doubling any variable. But thats not evidence the model is right.
1. If the "model" results are consistently supported by laboratory measurements and direct observations then there's a pretty good chance the model is right.
2. You (and Jim) are confusing "models" which are essentially mathematical algorithms with GCMs which are more predictive and less certain. In Maths and Physics, numerical methods are often used to solve problems which can't be solved analytically. I've used/developed such models myself as I'm sure many others have. In many cases the model can be tested with known data. For example, if I've developed a program which performs numerical integration, I can test it with the values of known integrals. The model can then be run and produce results to whatever accuracy I specify.
Your estimate of 0.05 deg for a quadrupling does not seem reasonable since the calculated forcing for a doubling is ~3.7 w/m2. Observations and theorectical physics suggests that sensitivity is ~0.3 deg per w/m2 implying a temperature increase of ~1 deg C.
Your estimate suggests that the earth's climate only varies within a very narrow temperature band and that even quite large forcings are offset by feedbacks. This is not consistent with what we know about past and recent temperature fluctuations.
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Post by jimcripwell on May 31, 2009 10:53:45 GMT
glc writes "Do you? Can you tell me what Jim's asking then? "
I take the point, and I am not sure what I am asking,either. I use these sorts of blogs to try and develop my ideas, since I have no-one here with whom I can discuss the issues. Last night I went back and re-read the first part of Chapter 6 of the TAR, and the definition of rsadiative forcing (RF). This is
“The radiative forcing of the surface-troposphere system due to the perturbation in or the introduction of an agent (say, a change in greenhouse gas concentrations) is the change in net (down minus up) irradiance (solar plus long-wave; in Wm−2) 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”.
I am still not sure I understand it. However, I tried to imagine how someone like glc would go about calculating a value. First one needs to imagine a hypothetical situation where the amount of CO2 in the air is instantaneously doubled. Then one imagines that there is a process which allows the stratospheric temperature to come to radiative equilibrium; and some other processes which prevent the rest of the atmosphere from changing temperature. Precisley what these are I dont understand. Now glc assures me that there are an exact set of mathematical expressions which describe this situation completely, and allows one to calculate the RF. There is experimental data to show that this situation applies. Now we take this value, and use it in some way that I dont understand. The RF assumes that the temparature in the lower atrmosphere does not change, but we use the RF value to calculate how the temperature of the lower atmosphere would have changed, had it been allowed to do so. At this point, my funny internal feelings told me that I am completely over my head, and I had better not try to comment any more.
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Post by icefisher on May 31, 2009 15:30:11 GMT
I think you hit the nail on the head there GLC. Seems to me one can easily develop mathematical models that mimic anything, then tell us the effect of doubling any variable. But thats not evidence the model is right.1. If the "model" results are consistently supported by laboratory measurements and direct observations then there's a pretty good chance the model is right. 2. You (and Jim) are confusing "models" which are essentially mathematical algorithms with GCMs which are more predictive and less certain. In Maths and Physics, numerical methods are often used to solve problems which can't be solved analytically. I've used/developed such models myself as I'm sure many others have. In many cases the model can be tested with known data. For example, if I've developed a program which performs numerical integration, I can test it with the values of known integrals. The model can then be run and produce results to whatever accuracy I specify. Your estimate of 0.05 deg for a quadrupling does not seem reasonable since the calculated forcing for a doubling is ~3.7 w/m2. Observations and theorectical physics suggests that sensitivity is ~0.3 deg per w/m2 implying a temperature increase of ~1 deg C. Your estimate suggests that the earth's climate only varies within a very narrow temperature band and that even quite large forcings are offset by feedbacks. This is not consistent with what we know about past and recent temperature fluctuations. Wrong! First after I explained my .05 came from an actual estimate of increased average height of emissions from the atmosphere (your model by the way) you are just handwaving trying to throw different numbers in without supporting calculations. My formula for the .05 was roughly 385 times 4, divided by one million, times the 33 degree increase in our blackbody temperature increase attributed to our atmosphere. How did you arrive at your numbers? My calculation only estimates the climate forcing by adding a certain amount of gas to the atmosphere. Adding that gas affects the average height of emissions as you described in your description of the forcing model. Obviously to arrive at your numbers 3.7 w/m2 and .3C/w/m2 there needs to be a lot more stuff you have not yet even attempted to describe or disclose. Additionally your conclusion that my model suggests earth's climate only varies within a narrow range is a fundamental error in logic. Here is an example of that error. If it rains the sidewalk gets wet. The sidewalk is wet. So it must have rained. Thats wrong because the sidewalk could get wet by turning on the garden hose or any number of other sources. Not being able to navigate that simple example of logic explains a lot about your confusion with climate models GLC.
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Post by glc on Jun 5, 2009 19:14:20 GMT
I take the point, and I am not sure what I am asking,either. I use these sorts of blogs to try and develop my ideas, since I have no-one here with whom I can discuss the issues. Jim Have been otherwise engaged over the past few days but have just noticed your post. See if you find this link useful www.barrettbellamyclimate.com/page45.htmIf you have a reasonable grasp of integral calculus you should be able to follow the article which will hopefully provide a basic understanding of the radiative transfer equations used in the MODTRAN program.
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Post by jimcripwell on Jun 6, 2009 12:26:22 GMT
glc writes "If you have a reasonable grasp of integral calculus you should be able to follow the article which will hopefully provide a basic understanding of the radiative transfer equations used in the MODTRAN program."
We are talking at cross purposes. My problem with understanding is not how MODTRAN works. I am sure it does an excellent job of solving real problems. From my limited knowledge, estimating the radiative forcing of CO2 is not a real problem; it is a hypothetical problem. According to the definition of RF in the TAR Chapter 6, we find "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” This to me is a purely hypothetical situation, where high level temperatures are allowed to adjust, but low level temperatures stay constant. Do you agree that this is a hypothetical situation, and if not, why not? And if it is a hypothetical situation, how can MODTRAN, which is designed to solve real problems, solve a hypothetical one?
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