Thank you
Cesar

Thank you for both taking the time to read the comments and participate. I appreciate the honesty and integrity of your last post and the incentive you gave me to re-open the debate with Brian. Although I’m not sure he’ll reply given my time-delayed response: who knows, watch this space.

If my initial comments were not as friendly as they should have been, I apologise; it can be impossible sometimes to distinguish between honest mistake and intentional malice.

Of course, you haven’t actually said where you stand on this subject or why, only commented on your perceived view of my position… Don’t feel drawn if you don’t want to, I won’t be offended and I really should spend more time working at my day job.

Thanks again,

Azz

Observation and small participation in this conversation has been extremely informative. This topic is exhilarating to me and, believe me, I have found you a rare breed in that you can discuss the science as science from a skeptical viewpoint and this can remain predominantly civil…the blogosphere is not nearly as representative. The point in saying so, is that I have enjoyed this and give you due respect. But, I digress.

“I’m still not sure why you think that my admissions require that I accept others opinions as superior to my own however or indeed where you think I conceded to nearly every AGW theory, I most certainly have not and if you think that is so then you obviously do not understand the theory you are defending.”

In re-reading your posts, I have come across a major fallacy of my own. You said:

“I’ve summarised the evidence that I found presented there:

Paleo-climate
* There is a problem, 2nd Half 20th Century climate variation is unique:
- Last 50-yrs temperature increase unprecedented
- Coincides with increased ACO2 concentrations
- CO2 is a major GHG
- CO2 higher today than in last 650,000 years
- Surface temperatures higher today than in the last 1,000 possibly 2,000 years

Global Climate Models (GCMs)
* Identifying the cause:
- Modelling 20th Century climate variations (natural variation + internal and external climate forcing)
- Models suggest CO2 is the likely culprit
- Models predict C02 finger-print (observable)
- Models forecast future climate change scenarios (observable)

Current Observations
* Validation of GCM predictions by observation
- Modern day surface, troposphere and ocean temperature records
- CO2 finger-print

Would you agree in principal with this summary or would you add anything I’ve missed or refute anything I’ve said?”

The first time I read that, I read that as a concession of your own beliefs and not a recount of the argument as it stands. Therefore, I hope you can see how I could be harping on such points having misinterpreted the function of that passage. My apologies.

Once again, Brian, Azz, great discussion. I have nothing else to contribute.

Ok, you caught me being self-deprecating; it’s a common English failing, although maybe not as common as certain others!

The main point I’m trying to make in the comments you highlight is that as with most members of the public who try to take an interest in this subject I do not have access to the papers published in Nature or Science or anywhere else for that matter. It is not my ability to understand the underlying science, concepts or arguments that I call into question with these remarks but merely a recognition on my part that I rely heavily on others to honestly represent the science that these papers contain in the more public-friendly manner that I require to fully comprehend them and their significance. I also feel obliged to acknowledge where I have not read very widely on a particular topic, knowing full well that my position is therefore less solid.

I’m still not sure why you think that my admissions require that I accept others opinions as superior to my own however or indeed where you think I conceded to nearly every AGW theory, I most certainly have not and if you think that is so then you obviously do not understand the theory you are defending.

You then say:

“My issue is not your inherent position, you are free to choose, but the extraordinary amount of effort that Brian has put forth with little more than doubt returned on your behalf.”

I can only respond to facts that are pertinent to the underlying debate. Central to the issue is how do we know that the GCM assumptions of the cllimate sensitivity to increased amounts of atmospheric carbon dioxide is correct?

So I will try to respond to any evidence that Brian offers that is pertinent to his argument of cause and effect but I will not feel compelled to be driven down blind alleys by jetstreams.

Azz

I will try to focus my response on the main point of your argument as I see it. That is, that the argument in favour of the AGW hypothesis is based the confidence levels we can draw from the laboratory science and the output of the 21 or so GCMs.

The reasons why you personally share in this confidence is you say fundamentally because:

1.That we understand correctly the fundamental science involved; not just the laboratory science but how climate operates in the real world.

2.That GCMs are advanced enough to model the real-world climate sufficiently well to produce predictions within a high confidence.

This is further backed in your opinion that the model output can be measured favourably, within those confidence levels, to real world observations; you then kindly go on to list some (but not all you say) of those model predictions.

I hope I have not misrepresented you in anyway, it is not my intention to do so. Naturally I disagree with these points or I too would be with you on the AGW side. But let’s start on a positive; common ground where we do both agree:

“Models are useful tools and whilst not evidence themselves can generate a reasonable level of certainty about an outcome under expected operating conditions.”

Where I think we separate is only on the level of confidence that we have in the understanding of our climate knowledge and our ability to model it. Dr David Evans says it better than I could:

\\** “Computer Models Incorporate a Lot of Sound Empirical Science

Yes they do. The climate models contain some well-established science that has been verified by empirical observations. But they also contain a myriad of:

• implicit and explicit assumptions
• omissions
• guesses
• gross approximations.

A single mistake in any one of these can invalidate the climate models.

Typical engineering models that mimic reality closely contain no untested assumptions, material omissions, guesses, or gross approximations. They are the result of mature understanding of the reality being modelled, and have been tested ad nauseum in a wide range of circumstances. On the other hand, climate science is in its infancy, individual models routinely fail most tests, the climate models are riddled with untested assumptions and guesses, they approximate the atmosphere with cells a hundred kilometres square and hundreds of meters high, and they do not even attempt to model individual cloud formations or any feature smaller than the cell size. Don’t let the word “model” fool you into thinking climate models are better than they are.” **//

For a much more detailed discussion of a sceptical scientist’s view of the validity of using model output as the basis for policing making in climate science, take a look at Dr Roy Spencer’s explanation of how these models work and why he thinks they are flawed:

http://www.drroyspencer.com/

In order to hold your faith in the AGW hypothesis you must inherently believe that models are, on the balance of probability, more likely to be right than wrong. Given that it is possible for models to be right but for the wrong reasons, it is surely (as Einstein will testify) the one prediction that fails that has far more significance that the 100 that succeed.

Still, with that in mind, let’s look at some of the specific points you make:

“The models predicted that a warming world would push the jetstream toward the poles. This has been detected.”

It would be good to have a reference for this but my immediate question is this: are you suggesting that increased AC02 caused this move in the jetstream or are you suggesting that it was caused by the general warming of the climate, whatever the underlying cause of that warming? We already know that the models assume AC02 is causing the warming, the question is therefore would the models predict this whatever the cause and if so, as I suspect, this has no bearing on the argument for an anthropogenic cause.

“The models predicted that the tropopause would rise gradually in altitude as a result of warming. This has been detected, and the models require ACO2 for the modeled response to even remotely match reality (see Figure 9.14 in the IPCC AR4 WG1 Chapter 9, page 700).”

The IPCC also explain that the predicted increase in the height of the tropopause is they say caused by two factors; ozone induced stratospheric cooling and tropospheric warming due to increased GHGs (i.e. water vapour). That there has been a broad cooling of the stratosphere and warming of the troposphere is not in dispute. How much of the warming is caused by ACO2 is the key debate. Again, your argument for ACO2 as the cause is circular. However, what the models also universally predict is that the same warming in the troposphere, if caused by increased AC02, will create a hotspot above the tropics. This fingerprint has not been observed and, if using the scientific principles you espouse, you should acknowledge this as a significant and major flaw in your theory. I wonder if you will?

“The models predicted that outgoing shortwave radiation would change as a result of aerosols. This has been detected. See Figure 9.3 in the IPCC for the shortwave radiation effects as a result of Pinatubo and how the simulations that included Pinatubo correctly modelled the shortwave radiation effects as a result of aerosols.”

I assume by this you’re again trying to show how well the GCMs model our climate but this is still not relevant to the fundamental issue of the effect of increased levels of AC02 in the climate. However, there a couple of recent discussions on the accuracy of climate model feedbacks on the credibility of model assumptions and on ability of models to accurately model past known climate change on Anthony Watts’ blog that I think are pertinent to this debate and interesting:

Climate Sensitivity and models…
http://wattsupwiththat.com/2009/07/15/9373/#more-9373

Models can’t account for warming in the past:
http://wattsupwiththat.com/2009/07/14/there-appears-to-be-something-fundamentally-wrong-with-the-way-temperature-and-carbon-are-linked-in-climate-models/#more-9347

“The models have predicted an increase in ocean heat content as atmospheric heat is absorbed slowly by the oceans. Ocean heat content has been increasing as expected, and the models again require ACO2 for the modeled response to come close to reality (see Figure 9.15 in the IPCC AR4 WG1 Chapter 9, page 706).”

I’m not as well read on this subject as I would like but I know that Dr Craig Loehle has recently completed a study of the ocean heat content anomaly data compiled by Willis et al (2008b), his findings show that since the Argo array of profiling floats programme began taking accurate measurements in 2003, that the ocean has been cooling during the period 2003 – 2008.

These findings and other observations are discussed in detail here by William DiPuccio, in a guest blog on Roger Pielke Sr web site:

http://climatesci.org/2009/05/05/have-changes-in-ocean-heat-falsified-the-global-warming-hypothesis-a-guest-weblog-by-william-dipuccio/

“The models have become accurate enough that they’ve been used for regional predictions of atmospheric temperatures, and those predictions have all been shown to need ACO2 in order for the models to match reality (See Figure 9.12, IPCC AR4 WG1 Chapter 9, page 695).”

All this talk about ocean heat content and regional predictions of atmospheric temperatures and yet no mention of mean global surface temperature these days…

http://rankexploits.com/musings/2009/model-mean-trend-rejecting-since-2001-for-a-year/

“The models predicted that, as ACO2 built up in the troposphere and it warmed up, the stratosphere would cool off. This has been detected, and in all datasets (see Figure 3.17 in the IPCC AR4 WG1 Chapter 3, page 268). This last piece of evidence (that I’m choosing to focus on) cannot be reproduced by solar irradiance changes, since the only way that the stratosphere can cool is if the troposphere is keeping outgoing energy from reaching the stratosphere in the first place. If increased solar irradiance (which varies WAY too little to cause the observed changes anyway, but that’s a different issue) were the cause, then the stratosphere would have to warm, not cool, and that’s not happening. So something is keeping the energy in the troposphere.”

Aren’t you just repeating your second point about the expected rise in the height of the upper troposphere and explaining why you think it can’t be solar induced? I refer back to the point I made then, and ask you to please explain why the second bit of that prediction, the hotspot over the tropics, isn’t in fact there?

“At this point, there’s only a couple off things that could keep the energy in the troposphere – GHGs and clouds being the two main ones. The two most important GHGs are water vapor (which has been shown using independent empirical evidence to be a feedback, not a forcing due largely to its short residence time in the atmosphere) and CO2.”

I’m fine with most of that paragraph although I would contend that ACO2 does most of its irradiance absorption in the first 20ppm and then the effects tail off significantly, what is most important is not more ACO2 but the climate sensitivity to it and whether the feedbacks are then positive or negative…

“And clouds are probably the biggest unknown remaining in the models today – sometimes clouds warm the earth, sometimes they cool it, and modelling when each happens and how has proven to be difficult.”

Completely agree and I refer back to Dr Spencer’s excellent discussion explaining the impact of this uncertainty on model predictions and the AGW theory.

“Ultimately, though, I think you’re asking for a level of certainty that simply isn’t possible in reality, never mind any field of science. Science deals with probabilities, not certainties, and there’s always a small chance that what’s currently considered to be caused by X is actually caused by Y. “

I’m not looking for certainties at all. What I am looking for is scientific integrity on both sides and for an open and honest debate. There are many issues at stake here over and above the obvious human consequences involved whichever side is shown to be correct, not least of these it the credibility of the scientific community in the eyes of the public and the resulting damage that it could cause.

“That’s fundamental to the scientific method of “hypothesize, measure, compare measurements to hypothesis, update hypothesis, measure again” ad infinitum. There’s not even 100% unequivical proof that gravitation works the way we think it does, or that General Relitivity is correct. If your standard is 100% unequivical proof, then a) you’re not a skeptic, and b) you’re looking for answers in science that it can’t provide – try religion instead.”

Religion is a funny one! 0% evidence, 100% faith. For me, that’s much closer to where I feel that Hanson and Gore stand on this particular spectrum. I do agree with you on the general point but the problem with the AGW story is that this is not being conducted with the rigour or the integrity that we expect all science to be based on. Let’s talk about Mann, McIntyre and the hockey stick debacle, high-jacking of the IPCC for political gains – just don’t call me a conspiracy theorist!

“BTW, in the process of discussing the empirical evidence thus far, you’ve been breaking your own rules (which I agreed to, if you recall) by simply dismissing the evidence I’ve presented thus far. Simply saying that “there is no empirical evidence” or that the evidence presented thus far is “the flimsiest of circumstantial evidence” doesn’t make either so.”

Not really, I asked you to show me some empirical evidence and you showed me model output and probability statements. You admitted yourself that the models themselves are not evidence, and so far you have shown me nothing over and above that. The burden of evidence is with you on this one.

“Now, Azz, if ACO2 isn’t the cause, then can you hypothesize what is?”

No, and why should I? If I said that I think it’s a small part GHGs and a large part natural variation following the last mini Ice Age, you’d tell me that models show that this is an incorrect analysis, that natural variation alone cannot be the cause. So I’d ask you to explain the Medieval Warm Period or the lack of correlation between the earth’s temperature and CO2 levels going back over the last 650m years, and the circular argument would begin again.

You believe the cause of recent warming to be the increase in man made AC02 emissions, that’s fine, but if you want me to believe your theory too then show me the evidence, don’t show me your lack of an alternative explanation and call it evidence or berate me for not showing you evidence to the contrary.

Going back to your religious analogy, as an atheist, I feel no compulsion to disprove something that is not there.

Cheers,

Azz

“Let me up-front, I’m not a scientist and freely admit to often having difficulty understanding the technical detail contained in many of the climate science papers that underpin the debate”

“I will also freely admit to bringing my own prejudices and preconceptions with me to the table, along with a genuine regard for evidence and a willingness to change my mind based upon it.”

“I’m not entirely up to speed with all the topics in the non-exhaustive list you have given”

As well as:

“I would make one general comment and that is to say that contrary to what you appear to believe, I have a very good understanding of the AGW theory and I have read much on both sides of the debate.”

Which is it? Do you maintain that you “have difficulty understanding the technical detail” but “that does not make [your] understanding and grasp of the points that matter in this debate inferior?”
Interesting.

You say:

“It is for those that support the idea of AGW to describe the hypothesis in detail and to set out repeatable tests based on falsifiable empirical evidence before the hypothesis can become an accepted theory. It is not my responsibility to do that for them. My position is simply that despite what the NASA scientists and their herd of followers would have us believe, the AGW movement has failed thus far to move beyond the hypothesis stage and that the empirical evidence we do have has failed to provide the required support it needs and may even point in the opposite direction.”

Brian offers:

“Ultimately, though, I think you’re asking for a level of certainty that simply isn’t possible in reality, never mind any field of science. Science deals with probabilities, not certainties, and there’s always a small chance that what’s currently considered to be caused by X is actually caused by Y. That’s fundamental to the scientific method of “hypothesize, measure, compare measurements to hypothesis, update hypothesis, measure again” ad infinitum. There’s not even 100% unequivocal proof that gravitation works the way we think it does, or that General Relativity is correct. If your standard is 100% unequivocal proof, then a) you’re not a skeptic, and b) you’re looking for answers in science that it can’t provide – try religion instead.”

In empirical study there is ONLY hypothesis testing. We assume the null and based on evidence, accept (fail to reject) or reject (fail to accept) our hypothesis, the semantics demonstrate built in skepticism and the impossibility of proof of theory. Shall we begin debating whether or not the sun will rise tomorrow? Surely that is much more pressing issue…

My issue is not your inherent position, you are free to choose, but the extraordinary amount of effort that Brian has put forth with little more than doubt returned on your behalf. I would like to see Brian’s continued response, but, as you put it “further discourse with you on this topic would I’m sure prove to be an extremely unsatisfying distraction.”

However, in any event, I would be interested in reading your theory as to the meaning behind the amalgamation of data and events thus far presented on the topic.

Eric

Thanks for those kind words. Given the inclusivity of the message held within your opening quotation I will happily hold up a mirror so you can bathe in the reflection of its light and wisdom.

Don’t get carried away with my obvious good nature, I’m not flattering about the rest of your post. Indeed I was worked up enough, for about 2 minutes, to consider a full and comprehensive response to all the fatuous comments you make but to be honest after reading it through again, I realise that you have either not understood my arguments fully or have chosen wilfully to misrepresent me – hence further discourse with you on this topic would I’m sure prove to be an extremely unsatisfying distraction.

I would make one general comment and that is to say that contrary to what you appear to believe, I have a very good understanding of the AGW theory and I have read much on both sides of the debate. I concede only to not being a scientist but that does not make my understanding and grasp of the points that matter in this debate inferior to yours or anyone else’s, nor indeed does it make my position inherently wrong. It is for those that support the idea of AGW to describe the hypothesis in detail and to set out repeatable tests based on falsifiable empirical evidence before the hypothesis can become an accepted theory. It is not my responsibility to do that for them. My position is simply that despite what the NASA scientists and their herd of followers would have us believe, the AGW movement has failed thus far to move beyond the hypothesis stage and that the empirical evidence we do have has failed to provide the required support it needs and may even point in the opposite direction.

The one thing I do agree with you on is that after all the much appreciated effort that Brian went to on his last post, I do owe him a response. Thank you for the prompt I needed to set about doing just that.

Best regards,

Azz

“Every man takes the limits of his own field of vision for the limits of the world. ” – Arthur Shopenhauer

You consistently state that you have limited, basic or incomplete understanding of the AGW problem, yet are quite defiant to someone (amongst a vast community) with obviously superior knowledge. You have stated you are not a scientist. you have conceded to nearly every AGW theory, yet overly rely on the problem of induction to refrain from conceding the point.

If you were a leading thinker in physical sciences, had a series of published papers and presented compelling, repeatable evidence (as you demand, receive, yet still reject) your arguments might hold water. Do not confuse “doubt” and “cynicism” with “skepticism.” Skepticism is based on empirical rigor, as Brian has asserted and provided, you have not. As well, if you concede that the earth is warming, ACO2 is rising etc. and still can’t get behind the AGW theory, what then, as Brian also queries, is your solution (or cause of the effects). “I don’t know”, “we haven’t found it yet”, “we need to reopen the debate” or “we need 10 years of consistent study” (the mantra of GWB, stated at a time which the IPCC had been in formation for 9 years…) is insufficient and merely returns back to the reliance on the problem of induction or, even less noble, a simple cop-out.

I would love to hear a reply, or, simply a reply to the last post of Brian’s.

Eric

…being able to retro-fit a model when you already have the answer is not compelling science and can never be considered empirical evidence.

While I agree that it’s not evidence, model results can be compelling nonetheless, especially when modeling is the only way to run multiple experiments on a system like the Earth’s climate. We can’t create lots of Earths and run controlled experiments on the real thing, so we have to create those Earth’s in a computer. Ultimately, as I discuss in Myth #19 above, the purpose of predictive models is not to provide independent data, but to generate a reasonable level of certainty about an outcome under the expected operating conditions. Just because you don’t like models in genral doesn’t mean that they’re not supremely useful tools.

The way you prove out a model is by using it to generate a hypothesis or multiple hypotheses that can be tested and verified with measured data. Then you compare the model’s predictions with real data and make adjustments to the model accordingly. The existing GCMs have gone through this iterative process, improving each iteration, at least six times over the last 20 years or so. The “general observational evidence” that you agree shows the Earth is warming up have largely been predicted by the models. This supports the hypothesis that the GCMs are mostly accurate in a statistically rigorous sense (as defined by Monte Carlo analyses of how the multiple models respond to multiple variations to input parameters).

Furthermore, once a model has been proven out, the proven model can be, and usually is, used to determine what is likely to happen if some initial condition or internal variable changes. In electronics, this would be like replacing a resistor with a totally different value or a different component entirely (a capacitor, say), or injecting noise into the design that was previously noiseless. Ultimately, this is done becaus it’s easier and cheaper to run a hundred iterations of model than it is to build a hundred different pieces of hardware. In the case of GCMs, the models are run with ACO2 (or water vapor, or what have you) removed. And the results show – in nearly every case – that the predicted climate response without ACO2 is radically different from reality.

So, let’s examine some of the evidence that the models are correct a little more closely (but in no particular order).

The models predicted that a warming world would push the jetstream toward the poles. This has been detected.

The models predicted that the tropopause would rise gradually in altitude as a result of warming. This has been detected, and the models require ACO2 for the modeled response to even remotely match reality (see Figure 9.14 in the IPCC AR4 WG1 Chapter 9, page 700).

The models predicted that outgoing shortwave radiation would change as a result of aerosols. This has been detected. See Figure 9.3 in the IPCC for the shortwave radiation effects as a result of Pinatubo and how the simulations that included Pinatubo correctly modeled the shortwave radiation effects as a result of aerosols.

The models have predicted an increase in ocean heat content as atmospheric heat is absorbed slowly by the oceans. Ocean heat content has been increasing as expected, and the models again require ACO2 for the modeled response to come close to reality (see Figure 9.15 in the IPCC AR4 WG1 Chapter 9, page 706).

The models have become accurate enough that they’ve been used for regional predictions of atmospheric temperatures, and those predictions have all been shown to need ACO2 in order for the models to match reality (See Figure 9.12, IPCC AR4 WG1 Chapter 9, page 695).

The models predicted that, as ACO2 built up in the troposphere and it warmed up, the stratosphere would cool off. This has been detected, and in all datasets (see Figure 3.17 in the IPCC AR4 WG1 Chapter 3, page 268). This last piece of evidence (that I’m choosing to focus on) cannot be reproduced by solar irradiance changes, since the only way that the stratosphere can cool is if the troposphere is keeping outgoing energy from reaching the stratosphere in the first place. If increased solar irradiance (which varies WAY too little to cause the observed changes anyway, but that’s a different issue) were the cause, then the stratosphere would have to warm, not cool, and that’s not happening. So something is keeping the energy in the troposphere.

At this point, there’s only a couple off things that could keep the energy in the troposphere – GHGs and clouds being the two main ones. The two most important GHGs are water vapor (which has been shown using independent empirical evidence to be a feedback, not a forcing due largely to its short residence time in the atmosphere) and CO2. And clouds are probably the biggest unknown remaining in the models today – sometimes clouds warm the earth, sometimes they cool it, and modeling when each happens and how has proven to be difficult.

Ultimately, though, I think you’re asking for a level of certainty that simply isn’t possible in reality, never mind any field of science. Science deals with probabilities, not certainties, and there’s always a small chance that what’s currently considered to be caused by X is actually caused by Y. That’s fundamental to the scientific method of “hypothesize, measure, compare measurements to hypothesis, update hypothesis, measure again” ad infinitum. There’s not even 100% unequivical proof that gravitation works the way we think it does, or that General Relitivity is correct. If your standard is 100% unequivical proof, then a) you’re not a skeptic, and b) you’re looking for answers in science that it can’t provide – try religion instead.

BTW, in the process of discussing the empirical evidence thus far, you’ve been breaking your own rules (which I agreed to, if you recall) by simply dismissing the evidence I’ve presented thus far. Simply saying that “there is no empirical evidence” or that the evidence presented thus far is “the flimsiest of circumstantial evidence” doesn’t make either so.

Now, Azz, if ACO2 isn’t the cause, then can you hypothesize what is?

I’m not entirely up to speed with all the topics in the non-exhaustive list you have given as further proof of GCM efficacy, so maybe you could point out just one or two of them could *only* be explained by increased ACO2 so we could discuss them further? Cause and effect is highly relevant as you point out and I will come back to.

On GCMs:

I have read your Myth #13 and the paper you pointed me too and I remain totally under-whelmed. Even the paper spends a large amount of it’s time acknowledging the issues it sees with GCMs; the top 3 for me being:

1. Non-independent data set
2. Laboratory science versus real world complexities of the climate system
3. Large areas of uncertainties & assumptions made by models

I do not deny your point that we know much more today about our climate and the basic underlying science than we used to but that misses the point. A model is not evidence in itself, it’s just a set of rules and inputs made by humans with a growing but still limited knowledge of the subject matter. To describe that level of knowledge as high in order to give the impression that we pretty much know it all and therefore we can have high levels of confidence in output of GCMs is either intentionally misleading or a little dishonest.

The bottom line for me then is this… being able to retro-fit a model when you already have the answer is not compelling science and can never be considered empirical evidence. Further, adding general observational evidence of the earth warming and the effects of that warming does not give any more weight to the theory you’re trying to prove.

So when addressing the issue that started this discussion off, i.e. your claims of over-whelming evidence for AGW, I will continue to focus on the 2 points central to most skeptics postion:

1. Cause and effect
2. Empirical evidence

Pointing out number 1 when you make a spurious statement about sea level rise (for example) does not weaken my position it only questions why you raised the point in the first place…

If you had number 2, you wouldn’t be talking to me about GCMs.

Cheers, Azz

However, even if that were true, there is a long list of climate predictions that GCMs have made that have been verified. In no particular order, they include:

Stratospheric cooling as a result of more energy absorption in the troposphere.
Sea level rise.
Increasing ocean heat content.
The increased elevation of the tropopause.
The poleward migration of the jet stream.
A measured reduction in the amount of outgoing longwave (IR) radiation.
More dramatically increasing temperature in the Arctic than the global average.

This is hardly an exhaustive list, but each of these things has been measured empirically and was a predicted result of CO2-driven climate disruption by GCMs. This strongly suggests that the GCMs, as imperfect as they are, more-or-less accurately represent the physics of the Earth’s climate.

Now, you’ll probably argue that these predictions could all be accurate in a warming world even if the cause isn’t CO2, and that’s partly accurate. Again I refer you to the fact that the models have been able to reproduce the measured temperature data since the late 1800s. Remove the additional GHGs from human activity and the models no longer accurately reproduce the measured data (I refer you to Myth #13 above for an image that shows this).

It helps that researchers have analyzed the latest versions of climate models (those used for the IPCC) and found their reconstructions are as accurate as reanalyses of the actual measured data itself.

The lack of a “smoking gun” in the tropical troposphere does nothing to negate the overwhelming evidence that third generation GCMs are largely correct, even as they’re being updated and upgraded to better account for clouds, aerosols, black carbon, and so on.

I’d like to apologise if any of my previous comments have caused you offence, it was entirely unintentional on my part.

A quick response to your comment #68.

Thank you for confirming my understanding of the AGW case; i.e. that there is no empirical evidence in support of the theory that there is a high level of climate sensitivity to increased C02 concentrations in the atmosphere. The theory itself is supported only by GCMs, which in turn is dependent soley on our growing but still very limited understanding of the science and our ability to model it.

To me, what you have described is the flimsiest of circumstantial evidence, not enough to convict and certainly not over-whelming.

Cheers, Azz

Your issues with Slammy and his with you are your own to work out, or not, as you are so inclined. They don’t involve me except in the most peripheral sense, and I’ve chosen to stay out of the way. My silence to date has been neither approval nor disapproval. Sometimes silence simply means that I’m waiting for something that affects me directly.

I don’t know if you’ve done this or not at this point, but for the future, you might want to click the “notify me if there are responses” button. That way you’ll get an email when someone posts a followup and you won’t have to come back every few days to manually check if any new comments have been posted. If you tire of the emails, then you can disable the email notifications just as easily.