Wow, what a nice thoughtful response, Sig. Thank you so much. I am delighted that you have studied Electrical Engineering because that's going to allow me to ask your opinion about something later that is closely linked to the Hansen Hypothesis. Your background is ideal when it comes to communicating with you on this subject.
First let me give you a brief summary of my own training and experience. I earned my Ph.D. in Electrochemistry. I can trace my chemistry lineage through my mentor to the famous Chemist, I.M. Kolthoff , 1894-1993 (for whom I.M. Kolthoff Hall on the Univ. of Minnesota Campus is named.) I had a typical career participating in and directing both basic and contract research. I have worked directly for Ph.D. granting Academic institutions, for private corporations, and two national laboratories at various points in my career. I was a consultant to the NIH and to a specialty, Canadian owned, aluminum extruder, both for quite a few years (this latter business had nothing to do with my main research interests but was a consequence of my training in electrochemistry) I published 27 full papers in the peer reviewed, primary literature, and one book, and of course numerous other publications. I hold two basic patents on biosensors and did most of the other stuff that goes with a career that is rather normal and fairly undistinguished for someone with my training. If I were to list all the details I'm afraid it would mislead by sounding more impressive than it was. I bounced around a lot because I was interested in everything. It made for an interesting scientific life, but probably was not helpful in forging a distinguished career in any one area.
I got interested in what was then known as Anthropomorphic Global Warming (AGW) once it began to be a common topic of discussion, and I read a couple of Linzer's early papers which took the position that the AGW hypothesis was still just that. Linzer was one of the first to raise the issue of clouds and point out that no one knew whether clouds were net warming or cooling and certainly no one had a clue how to model them. He was rather negative . I also read one of the early Hansen papers. There was a seemingly strong correlation between the measured rise of CO2 and reported mean surface temperature using actual thermometer readings. the correlation seemed particularly good for the period fairly well covered in North America by weather stations from the late 1800s up to 1990 or so. Of course as a scientist I was aware the correlation does not prove cause and that almost any two variables can be made to appear well correlated graphically, depending on the scale chosen for the axes. I new the radiative argument behind CO2 well, or thought I did, having taught elementary physical photochemistry and having published a couple papers in photochemisty with a real photochemist colleague whom I learned from. At that point I lost interest, and just assumed that either Hansen or Linzer, or both, would eventually be shown to be right.
It wasn't until I retired in 2005 that I got interested in the topic again. It was reading some of the AGW threads in the Politics and Religion section of ET. In particular there was one fellow, jem, who kept questioning everything and turning up these interesting papers that I began to read. I wanted to see what they were really about. And that's what led me down a path I never would have expected to be led down. I had been convinced by trust in the media and popular believe that it was a settled issue, that unless we started drastically reducing our CO2 emissions we were going to warm up and wreck the planet. But the scientific papers I was reading were indicating that the picture was far more clouded than I had realized.
Among the first things I learned by reading more of Hansen's papers was that Hansen had never questioned or tested his assignment of temperature to the dependent variable. He knew CO2 was what we call a greenhouse gas and he just assumed that more of it would therefore raise the temperature. This was almost childish in its simplicity as I look back on it . So sure enough, when you plot CO2 content against temperature you get quite a nice correlation for at least the period from the late 1800s through what ever year it was when they first did this. But of course the first thing he needed to do was determine which was the independent variable. He didn't do that! This was the first fatal error. In his " Eureka I have found it" moment he apparently had forgot all about Henry's law; understandable as it had probably been 30 years since he studied Freshman Chemistry. But why didn't one of those young fellows in is lab pipe up and say to him,"but Dr. Hansen, what about Henry's law? A corollary of Henry's law is that gases like CO2 have quite a strong temperature dependence for solubility in water. The solubility of CO2 in water drops as the temperature rises. Even if you never set foot in a chemistry or physics class, you only had to open one Coke left in your car on a hot day to discover this corollary of Henry's law. Could it be that CO2 is rising with temperature because it's coming out of solution in the oceans as the temperature rises, and because the rate of bio-matter oxidation is increasing with temperature? Would that amount be large or small compared to the amount of anthro CO2 we dump and could it be that if we looked with greater precision we might be able to see one source of CO2 riding on another with different time dependencies and perhaps even identify seasonal variation in different parts of the atmosphere.
Now I know what you are thinking. It's the same thing I thought. Naw, a guy like Hansen would never miss this. He'd test to see which was the dependent variable. (Of course he might need some additional information other than what he had available at the time, but surely since CO2 and temperature increased together he wouldn't just assume CO2 was the independent variable with out actually testing this assumption! ) Well, It appears that's what is did. And it was, I think, all due to that "Eureka Moment", CO2 is a greenhouse gas! (See for example Murry Salby's beautiful Talk and nice proof in Hamburg Germany on YouTube. This is where Salby takes up phase shifts and its a technical talk. His later presentations are much easier for the non-expert to follow.) So, Salby's work has convinced me that that business of apparently getting the dependent and independent variables reversed is one great BIG problem. It alone, keeps me from accepting Hansen's hypothesis.
Now there is another problem. And it is this. CO2's effect is radiative. Its contribution to partial pressure can be ignored,* and of course it is non-condensing so we don't have heat of vaporization or heat of fusion to concern us. But CO2 is an extremely weak absorber. It does not absorb in the visible at all. (It's colorless!!!), and it has only one active IR absorption mode, an asymmetric stretch. (Its symmetric stretch is non-IR-active because there is no change in polarization with that stretch) So its both a very weak absorber, and at trace concentration . In other words, it is a very crappy greenhouse gas. Does it play role. Yah, at least a little according to radiative models.
But here is another problem. It is rather easy to estimate what the additional effect of adding still more CO2 is. You just have to simulate , and you can do it quite accurately, at what concentration and by what altitude for a given partial pressure, all of the radiated IR from the Earth's surface that CO2 can absorb will be absorbed. It's been done many times, and above about 600 ppm there will be practically no more radiative heating at the surface from rising CO2. In other words long before the present 400 ppm doubles there will be little significant further heating from CO2 rise. Ooops!!
Now, one more problem. Very early in the modeling process The Hansen devotees' discovered something very disturbing. CO2 was such a weak greenhouse gas that the concentration could climb way on up there and yet the temperature would hardly budge. (see above paragraph) But they had told everyone at those hearings that we were in danger of a runaway thermal excursion if we didn't reduce our CO2 emission . Could the feedback to the effect of a little CO2 rise cause even more warming?
So all models today assume some amount of positive feedback, otherwise the warming is too little to be concerning. Sure enough, those models incorporating positive feedback indicate we are all on the path to dante's inferno. Now Sig, here is my question for you, since you are an electrical engineer. Lets assume the transfer function for the CO2 model provides amplification. (We don't have to identify the specific mechanism but let's assume it has to do with increasing water vapor and cloud formation.) A little warming from CO2 will lead to a lot more warming. Now if the net feedback is positive, won't the entire system be unstable and be rather quickly, say in a few decades or centuries be driven to its positive limit? (I'm assuming the response time is many orders greater for a climate than for, say, an operational amplifier.) It seems to me that if the feedback is net positive our climate system should be unstable and none of us should be here. We should have burned up centuries ago. So I have concluded there must be enough net negative feedback to maintain some overall, long-term stability in our climate. Lots of both positive and negative feedback elements have been identified. For example circular, vertical convection is supposed to be net negative and possibly the single most important negative feedback mechanism. (Ignored in all the earliest models.) Rising humidity is probably net positive, but cloud formation is probably either positive or negative depending on altitude, aerosol size and density.
IPCC models get re-adjusted every 6 years, or so, so they can can never be too embarrassingly far off . (See Nir Shaviv's fine talk on You Tube.) Judging by our inability to predict future temperature from these models, How can they tell us what we want to know. We know we are all going to die. We don't need a model for that. But we want to know when! Supposedly the models' universal failure to predict future temperature is due to their inability to model clouds. But I think the failures must go way beyond that. It seems you'd first have to get the dependent and independent variable decided correctly. Up to know the modelers have dealt with these little problems by ignoring them. We can model fairly well the radiative effects, but what about everything else. And I haven't even mentioned many other factors that are of obvious importance, but are nevertheless being ignored by the modelers.
You hit the nail on the head when you pointed out that we do a great job of weather forecasting for the next 24 hours, and a pretty good job seven days out, but the further we go out the worse it gets. Forecasters know why.. Its the presence of turbulence and non-linearities that lead to chaos and strange attractors. Many of the forecastors are resigned to the futility of doing anything beyond say thirty days. Apparently the climate modelers are either unaware of this chaos induced restriction, or they just want to keep quiet and keep the checks coming.
Of course there are a million other problems, as I know you must be aware of. There are some great presentations available on YouTube by knowledgeable Ph.D. experts. Try to find the time to listen to a few. It's an eye opener. At least it was for me.
I have already decided that the Hansen Hypothesis is simply wrong. But I can't rule out the possibility that man may be affecting his climate via some other mechanism. (What about plain old thermal pollution? Though it seems the urban island effects of Mexico City or Tokyo must rather pale in comparison to a good sized volcano.) Our CO2 atmospheric content has been decreasing for 15,000 years now. I'm not worried about 100 years of rise riding on top of fifteen thousand years of decline.
You said, " I don’t see anyone actively working to show that there will be no impact from global warming gasses, only working to poke holes in the theory that there may be." With regard to CO2, Murry Salby's most recent presentation is addressed exactly to this point you correctly raise . He uses an elegant error bounds argument to show quite convincingly that there will be no significant impact from rising CO2 for the foreseeable future. Methane is a lot stronger greenhouse gas than CO2. I think with all the fracking we ought to at least take a look at what the impact of methane pollution from leaks might be. On the other hand methane is unstable in the upper atmosphere. Perhaps that would ameliorate . It is worth looking at in my opinion. The reason I favor staying active in the Paris accord is we can at least have an influence if we are present at the table. I strongly favor development of alternatives to fossil fuels. At the same time, I'm not blind to the problems created by very rapidly rising demand for energy in the developing world. We must do everything we can to assist developing countries raise their standard of living , because as they do, their birthrates will drop. And lower population is the key to our planet lasting longer. We can't expect them to just take the leap to advanced energy production at great cost compared to their GDPs. We must allow them some leeway when it comes to temporary use of fossil fuels, especially coal. There is no reason not to, because Hansen's hypothesis should be allowed to die a proper death. Then we can move on. We can't stop Entropy from increasing, but we sure can affect the rate at which it increases!
And finally to those who would say, "well the Hansen Hypothesis may be wrong, but shouldn't we be doing something?" I would say, "it's best to decide what to do before you start doing anything."
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*CO2 on Earth is a trace, but critically important, component of the atmosphere. The only variable across the solar system, however, that appears consistent with the different surface temperatures on the planets would seem to be vapor pressure. The sun does work on the atmosphere and the higher the pressure the greater the temperature achieved during the period when the surface is oriented toward the sun. This is perhaps an over simplification by it is at least consistent with thermodynamics, the gas law, statistical mechanics, and the observed temperatures on the planets.
