Is Stratospheric Cooling Proof of CO2-Induced Global Warming?

[Gokul43201]

Is there evidence of a trend showing growing strength in Artcic winds over the last few decades? This is, after all, not about a single year.

 

[Gokul43201]

Yes, the general trend, subtracting the extremes, has been a steady gentle warming since the last glacial, but that is the pattern of all interglacials. Most of the warming of our present interglacial is believed to have happened in the first third of the period with resultant sea level rise and general warming. As interglacials are understood this is the norm.

Surely, you know this is not about the 10^-2K/decade warming out of a glacial, but the 10^-1K/decade warming of the last century or so.

The point is that dispite the studies of Mann, Hansen, and others, unless we are totally wrong in our evaluation of paleo-climates, greenhouse gases have only a small part to play on the stage of climate.

Who are "we", how small is "small" and how about some references?

Granted the effect of greenhouse gas is a necessary part of our livable world, but the effect of negative feedback have strong constraining effects on control and argue against a tipping point or runaway warming.

Without any reference to the gain or time constants of an effective negative feedback mechanism, this is a pointless "point". Interglacial swings are of the order of 10K, with periods on the order of 10⁵ years. A negative feedback mechanism with a time constant in the several thousands of years could be quite extraordinarily useless over timescales of 10² years.

Adressing the CO2 agrument in terms of AGW must include the facts that CO2 does not care where it comes from, and acts in the same way no matter its source. It must also take into account that we have very good evidence that CO2 has been much higher in other times...far higher than all the fossile fuel known reserves could achieve even if we were to release it all at once.
This alone should give pause to anyone reading or hearing that we only have a few years to correct what will become a catastrophe.

How many technologically advanced civilizations were around during these higher CO2 periods?

Nothing unusual has happened in the last century that hasn't happened many times before without human aid. Just as we havn't caused anything unusual, we can not create anything unusual.

All good reasons to overturn the Montreal Protocol and start producing and emitting CFCs as well.

 

[Andre]

Is there evidence of a trend showing growing strength in Artcic winds over the last few decades? This is, after all, not about a single year.

Please do check out the links, I'm merely showing the message. It's what the researchers say.

http://www.nasa.gov/vision/earth/lookingatearth/quikscat-20071001.html
http://www.sciencemag.org/cgi/content/summary/sci;322/5898/33

You can follow the daily development of the ice here.

http://ocean.dmi.dk/arctic/plots/icecover/icecover_2008.png

 

[Gokul43201]

Both seem to talk about the effect of winds on ice extent over the last few years. It seems to me like it may be possible that there is some wind related effect that is the dominant reason for the last three decades of trend, but right now there isn't enough data to support such a hypothesis.

 

[Andre]

Both seem to talk about the effect of winds on ice extent over the last few years. It seems to me like it may be possible that there is some wind related effect that is the dominant reason for the last three decades of trend, but right now there isn't enough data to support such a hypothesis.

As far as I recall, the full article of Richard Kerr in Science talks about a gradual process in the last century. I'm not at home and I can't see it from here to quote it, I'm afraid. Will get back to it later.

 

[Gokul43201]

As far as I recall, the full article of Richard Kerr in Science talks about a gradual process in the last century. I'm not at home and I can't see it from here to quote it, I'm afraid. Will get back to it later.

Me neither. Will have to look at it later.

Edit: I just read it now. It says that in the Greenland shelf, there was a lot of ice loss from an influx of warm water in 1997. That seems to be directly connected to the NAO. Similar loss of ice from shifting wind and water patterns is expected from modeling of the equivalent effect in the Antarctic. What doesn't seem to be well known is if, and to what extent, the changes in the winds are affected by changes in air temperature.

 

[heldervelez]

To those of us that are especially concerned with details:

The Netherlands’s people have a lot to loose with the rising sea.
Most probably they will loose ALL their land, assuming GW.
I've no notice of alarmism between them. This is a gross detail.
My oldest son bought a house there, this year. This a fine detail.

In physics a detail data mismatch becomes important if we have a model that is generally aligned with data, but in some points the model fails.
It was the case with the finding of planet Uranus, for instance. And physics has a lot of such good examples.
In this case of GW we lack the knowledge, the expertise to model with success.
Do we have a consensual model that agrees with past data?
I suppose that we have several models that doesn’t coincide in previsions.
Do we agree how data is collected, worked, massaged and interpreted? No.

I think that Phil Jones is monitoring the thermometric values used by IPCC and I have reasons to believe that he said that he will not make public neither the algorithm nor the database that he is using.
That’s ok I’m not indicating the source. Enlighten me if I’m wrong and someone considers it relevant.
Does someone finds and write here the previsions on sea level in the successive IPCC reports? It could be helpful.
Those last two paragraphs to me are non important at all because they are just peculiarities. I wrote them only to say that those kind of ‘facts’ are unimportant to the clime evolution. At most are important to understand why we are distracted from main facts.

 

[heldervelez]

But what cannot be considered a detail is the fact, which is not denied even by AGW believers, that ice cores indicate that temperature rise lead by (+-) 800ys the CO2 rise.

and it means:

1. Time t0 : Temperature start to raise
2. ​
   T0 + 800ys : CO2 start to raise
3. ​
   T0 + 5000ys : Temperature lowers (and CO2 still high)
4. ​
   T0 + 5000yrs+ xxx CO2 lowers

Physically the cause-effect relation cannot be inverted.

An explanation on this site of AGW believers (climate science from climate scientists):
http://www.realclimate.org/index.php/archives/2004/12/co2-in-ice-cores/

My understanding of this page is :

CO2 does not start, but ..maybe maybe not amplifies the temperature rise, and the explanation ..maybe maybe not is…

---- in the page contents I made a few translations such as:

… could in fact have been… translates …maybe maybe not…
… CO2 could have caused… translates …maybe maybe not…
…the probable sequence of events… translates …maybe maybe not…
… Some (currently unknown) process causes…translates …unknown…
… But it may give us a… translates …maybe maybe not…
… So CO2 might be stored… translates …maybe maybe not…

Well apart from all that maybe maybe not a pertinent question is in my mind is:
After 4200 yrs of amplifying cause, the CO2 gets tired of its amplifying role. CO2 is not in the mood.

Again can someone make a comment to this updated content?
http://www.realclimate.org/index.php/archives/2007/04/the-lag-between-temp-and-co2/

-----------------
In this site some points againts AGW of "Atmospheric CO2 Levels Follow Temperature, Data Clearly Shows..." Nov/2007

http://petesplace-peter.blogspot.com/2007/11/atmospheric-co2-levels-follow.html

Craig James is a Michigan meteorologist and here he explains his reasoning as to why atmospheric carbon dioxide does not drive, or control global warming.
...
...
Also, never once mentioned in the mainstream media is the fact that the southern hemisphere sea ice extent was at a record MAXIMUM this year
-----

 

[Gokul43201]

I had left this part for later, because I wasn't sure what exactly to make of it.

In my opinion the climate is a self balancing system, always attempting, but never succeeding, to achieve an energy balance.

I have no idea what you mean by this. Is it a scientific statement that you are writing metaphorically, or is the statement itself based on some philosophy other than empiricism.

This indicates a self correcting process of negative and positive feedbacks of less than 1.

I don't understand why that is so, but I also don't understand whether that is the feedback ratio, or the open loop gain, or the product of the two, or the closed loop gain. Which is it (I'm guessing it is the third, but need to be sure)?

Also, why would you expect this gain to be frequency (or timescale) independent? If not, do you imagine the system has the same gain at a timescale of 10⁶ or more years as it has on a timescale of 10² years?

 

[Andre]

But what cannot be considered a detail is the fact, which is not denied even by AGW believers, that ice cores indicate that temperature rise lead by (+-) 800ys the CO2 rise.

...
Again can someone make a comment to this updated content?
http://www.realclimate.org/index.php/archives/2007/04/the-lag-between-temp-and-co2/

You are linking to a blog, which is not peer reviewed and which would make some mentors frown here.

Anyway, positive feedback is considered here as a rock solid theory whilst it is only a idea/hypothesis, rougly like: first something is causing warming which causes the oceans to release more CO2 as it's capacity to store CO2 decreases with temperature. The extra CO2 in the atmosphere causes more warming, which causes more CO2 to be released, positive feedback.

But, if you diagose feedback, you have to play it by the physical rules of feedback with a lot of complications and up until now I have not found any paper testing that hypothesis by mimmicking/modelling the "temperature"/CO2 graphs of the Pleistocene ice ages with positive feedback. Actually when you attempt that, the result is failure, refutal, like this:

Complete documentation in this thread.

We are looking at the combined graph of the isotopes (considered paleothermometer) and CO2 concentrations as measured in the newest EPICA Dome C ice core during the last Glacial Transition between 20,000 and 10,000 years ago. The lack of persistency demonstrates that positive feedback cannot be discerned. It seems that we're merely looking at open loop master - slave behavior.

 

[heldervelez]

Mr. Andre tanks for the link to your post on the subject
"The positive feedback factor of CO2"
https://www.physicsforums.com/showthread.php?t=162192
I congratulate you for your work on the "lead or lag problem".
I stay with "Temperature leads and CO2 lags without any amplification factor".
Any doubts must be addressed in that thread.

About the issue raised on post #39 we can be enlightened reading on the 2nd page post #21 of that thread where Mr Vanesch details on feedback math, with some more words of Mr mheslep on 1st page post #15, and I do not see the need to bring that discussion to this thread.

I was not prepared to discuss the AGW in detail, and so, I’m sorry not to address information based on proper papers. I ask anyone to correct me if I say something that is incorrect. I like to address issues based on information and reasoning.
I was surprised by the position of NOAA on that web page.

Any idea on the why NOAA has that content?
Hypothesis 1: the CO2 cause of temperature rising is untenable.
Hypothesis 2: the page was ‘pirated’ from inside or outside NOAA
Hypothesis 3: ?

Unless better information I bet on the first hypotesis.

 

[Gokul43201]

Physically the cause-effect relation cannot be inverted.

When you have systems of coupled differential equations, all the variables involved become "cause" as well as "effect". Which is the cause and which is the effect, in a predator-prey system?

CO2 does not start, but ..maybe maybe not amplifies the temperature rise, and the explanation ..maybe maybe not is…

---- in the page contents I made a few translations

Those translations are good. There is always some uncertainty in the understanding. At the early stages of development of any new science, these uncertainties are always large.

When Quantum Electrodynamics was invented in the 20s, it made some terribly nonsensical predictions: infinite energies and masses, vanishing charge ... all kinds of nonsense. It took a couple decades to fix all the problems, and then quickly become one of the most accurate physical theories around.

But speaking of translation, let me try one, for fun. Here's an earlier post of yours:

I am not a climatologist. Instead of talking about data records with problems I’d like to hear about new models.
Look for the SUN factor, the long past record climate data (dinosaurs era, for ex.).
Look for the geological evidence on the past hot Earth against the theoretical model of ‘Frozen Earth’.

My translation: I am not an expert in the field, but as a lay person, I believe I can still tell the experts how to go about their research.

I recently saw some news about a large number of deaths in a nearby hospital. It was just after some big accident or something like that, but that's not important. What's important is that the surgeons in that hospital are obviously incompetent. I think I should just go there and teach those lousy surgeons how to do their job. Of course, I didn't take Biology beyond High School, but at least I have never had a dozen dead people in my house.



This is not to say that one shouldn't question the work done by professionals, but to point out that one ought to recognize the limitations of being not an expert in the field. One of those limitations is that one probably does not have the understanding or knowledge of the field necessary in order to tell the experts how they should be doing things.

 

[Gokul43201]

Actually when you attempt that, the result is failure, refutal, like this:

Let me make sure I'm not misunderstanding this. Are you saying you have proved that there can not be any positive feedback mechanism from CO2 (i.e., you have refuted the hypothesis of positive feedback from CO2)? And this proof involves eyeballing turning points, and not noticing an acceleration in T when CO2 is rising?

 

[Andre]

Let me make sure I'm not misunderstanding this. Are you saying you have proved that there can not be any positive feedback mechanism from CO2 (i.e., you have refuted the hypothesis of positive feedback from CO2)? And this proof involves eyeballing turning points, and not noticing an acceleration in T when CO2 is rising?

Not exactly Gokul, all that I said was that the lack of typical characteristics of positive feedback (persistency) do not support (refute) the positive feedback claim here. Actually there could be a slight positive feedback, but it's not detectable and it cannot account for the bi-stable seesaw as assumed like this:

http://www.realclimate.org/epica.jpg

since a bistable system (flip flop) by positive feedback requires a total gain >=1 in the loop and you will find it rather hard to model a momentary reversal halfway in such an oversteered positive feedback loop.

Actually, should you test both the IPCC radiation hypothesis for the atmosphere with 2-4 degrees warming for doubling and the Chilingar et al 2008 convection hypothesis, you would probably conclude that the latter is much better explaining the isotope temperature versus CO2 relationship.

But all is on the presumption that the graph indeed accurately depict temperature and CO2 concentration. There is a lot more to say about that.

 

[Gokul43201]

Not exactly Gokul, all that I said was that the lack of typical characteristics of positive feedback (persistency) do not support (refute) the positive feedback claim here.

There is a huge difference between an observation that does not support a hypothesis and an observation that refutes it. I hope you note the difference.

Actually there could be a slight positive feedback, but it's not detectable and it cannot account for the bi-stable seesaw as assumed like this:

http://www.realclimate.org/epica.jpg

First[/URL] of all, your first figure is over a timescale that is 2 orders of magnitude smaller than that of the second figure. There is no reason I've seen from your posts, that one should assume that the loop gain is frequency independent, and it looks to me like you are trying to extract a signal from a region that is so small, that it is dominated by noise. Moreover, if the closed loop gain is indeed large, there may be good reason to believe that it comes with a pretty small bandwidth. Third, why should it be necessary that the system can be modeled using a single feedback loop? There may very well be dozens of different feedback mechanisms, some negative others positive, with different gains, different bandwidths, poles all over the place, all kinds of non-linearity, and who knows what. And finally, there is the question of noise, which I shall come to in the next paragraph.

since a bistable system (flip flop) by positive feedback requires a total gain >=1 in the loop and you will find it rather hard to model a momentary reversal halfway in such an oversteered positive feedback loop.

I don't know what an "oversteered" positive feedback loop is. I can easily imagine halfway reversals if indeed there is more than one feedback mechanism (and they are all not positive). And even in a single feedback loop, I can very easily imagine such reversals, if you have significant noise in the system. And guess what: your figure shows that the noise amplitude is on the order of 10% of the rail-to-rail difference - that's huge. Why should it be impossible for noise - what looks like "noise" within a single feedback model may just turn out to be the result of a much different feedback mechanism operating at a much smaller time scale; you might not know until you analyze the noise spectrum - and I imagine people have done such things - to trigger turnarounds in the signal, especially when it is this big?

Actually, should you test both the IPCC radiation hypothesis for the atmosphere with 2-4 degrees warming for doubling and the Chilingar et al 2008 convection hypothesis, you would probably conclude that the latter is much better explaining the isotope temperature versus CO2 relationship.

Actually, I doubt I'm likely to conclude anything, unless I see obvious mistakes in one or the other that I am capable of judging from within my areas of relative expertise.

Moreover, to my knowledge, op-amp circuits with positive feedback are bistable (usually not even that - if the noise level is sufficiently low, they just hit one of the two rails and stay there) only because they are limited by the supply voltage (that itself should be treated as a negative feedback mechanism). In the absence of such limits^*, the output signal should just diverge, shouldn't it? I guess if you are at a pole, then you have an unstable system, but that will probably produce an oscillatory output (rather than the bistable signature in your figure). If you do have an oscillator with severe clipping (again, I believe that is itself a consequence of strong negative feedbacks), it could possibly look like a bistable system, but a different kind of one, if you can picture what I mean.

In any case, I know next to nothing about control systems and only the tiniest bit about feedback circuits. If there exists a Thevenin/Norton kind of theorem that let's you find a single loop equivalent for a jumble of different loops (I would be very surprised, but) I am not the person that would know about it. You should take my post as one one that is expressing a lot of questions and doubts about your conclusions. It would be best if someone more versed in these matters gives an opinion.

One more thing: your "refutation" seems to be an attempt at refuting a claim from a blog, not from a peer-reviewed paper. Even if your refutation is perfectly good, you will only have achieved a refutation of a claim in a blog. I think it would be better, if we want to show that the science is badly done, to go after the source, rather than the layman popularization of it.

 

[Eric_meyers]

I have a question about the realclimate blog posting: if CO2 lags temperatures by 800 years is explained by the fact that the CO2 is the mechanism that continues the warming from that point forward, then how come the temperature goes down while the CO2 remains high for xxx years after the cooling? If the CO2 is acting as an amplifier, then shouldn't the temperature at that point be locked with CO2 levels and not permitted to drastically reduce until AFTER CO2 levels drop?

 

[Andre]

There is a huge difference between an observation that does not support a hypothesis and an observation that refutes it. I hope you note the difference.

Let's see, positive feedback processes are persistant, the graphs don't show persistancy, hence the processes do not show a predominance of positive feedback. Olavi Kärner uses the term: http://www.aai.ee/~olavi/2001JD002024u.pdf in a such a case.

One more thing: your "refutation" seems to be an attempt at refuting a claim from a blog, not from a peer-reviewed paper. Even if your refutation is perfectly good, you will only have achieved a refutation of a claim in a blog. I think it would be better, if we want to show that the science is badly done, to go after the source, rather than the layman popularization of it.

That's the essence, there is no peer reviewed paper that I know of, which presents model results that demonstrates that the isotope signal could be caused by a positive feedback effect of CO2. There are just several studies, which show that CO2 lags "temperature" and speculate that this must be positive feedback, no math, no models, just a sentence or two of suppositions. This hypothesis simply has never been tested. The http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter6.pdf is built on this speculation. Note that there is no reference to any study that explicitely demonstrates that the ice core reflect the system response characteristics for positive feedback.

But I fully agree, the link to realclimate was tongue in cheek and I fully agree that we should never look there and link again (which is also )

Anyway, another thing to do is trying to reproduce data with other sources. So what would happen if we compare Antarctica with Greenland?

So if we would picture that sudden reversal to "cold" around ~14,500, as this has opposed the alleged warming feedback of the ever increasing CO2 concentration then that cold should show up somewhere. However this is the Greenland compilation of Ulf Erlingsson 2008

So no cooling at all around 14.500 calendar years ago, instead we see the Bolling warming and an complete different picture overall. No trace of a cooling input to force the Antarctic temperature reconstruction down against the feedback, on the contrary.

Hence I keep saying, we are on the wrong way and we should start from scratch instead of building global warming theories on blatantly conflicting reconstructions.

 

[Gokul43201]

Let's see, positive feedback processes are persistant, the graphs don't show persistancy, hence the processes do not show a predominance of positive feedback.

Do you believe you have shown that your demonstration of "no persistance" is rigorous? It looks to me like it could be completely meaningless - you are trying to eyeball a signal buried in noise and you are looking at the response in the wrong frequency window. Moreover, I think the thing you are searching for may itself be a strawman of kinds: there could be positive feedback in the system away from saturation, but not near it.

Olavi Kärner uses the term: http://www.aai.ee/~olavi/2001JD002024u.pdf in a such a case.

Olavi Kärner makes a case for a lack of persistence (in the short term temperature record) based on spectral analysis, all kinds of clever statistical examination and some sophisticated math tricks for dealing with non-linear systems with fractal structure. I know nothing of these methods, but they don't look very much like your visual estimate analysis.

That's the essence, there is no peer reviewed paper that I know of, which presents model results that demonstrates that the isotope signal could be caused by a positive feedback effect of CO2. There are just several studies, which show that CO2 lags "temperature" and speculate that this must be positive feedback, no math, no models, just a sentence or two of suppositions. This hypothesis simply has never been tested.

So basically, all this comes down to is your experience that there are no good mathematical models in place that produce the right feedback necessary to reproduce the paleoclimate record. I think we could have left things at that without trying to perform a refutation based on eyeball analysis. These systems are incredibly complex, and very hard to analyze. Don't you think we should leave such things to folks like Olavi Kärner, who seem to have the expertise necessary to do a serious analysis of the temperature records and various forcing mechanisms? Or else I recommend you send your refutation to J. Geophys. Res., and have some real experts look at it, rather than us laypeople who can't tell a banana from a hockey-stick.

The http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter6.pdf is built on this speculation. Note that there is no reference to any study that explicitely demonstrates that the ice core reflect the system response characteristics for positive feedback.

I don't care much for IPCC reports as a scientific source - they are not peer-reviewed, and some parts that I have read use some terribly unscientific language that I can only describe as "Business School talk". So let me tell you that I'm not keen to read any part of that chapter to see what they are saying there.

But I fully agree, the link to realclimate was tongue in cheek and I fully agree that we should never look there and link again (which is also )

I'm sure this gives you indescribable joy!

That's all I've got time for now.

 

[Gokul43201]

I have a question about the realclimate blog posting: if CO2 lags temperatures by 800 years is explained by the fact that the CO2 is the mechanism that continues the warming from that point forward, then how come the temperature goes down while the CO2 remains high for xxx years after the cooling? If the CO2 is acting as an amplifier, then shouldn't the temperature at that point be locked with CO2 levels and not permitted to drastically reduce until AFTER CO2 levels drop?

No, what triggers the start of the rise and fall is likely to be something other than CO2 (maybe the Milankovitch cycles, or maybe something else). Typically, it takes some kind of perturbation or noise to take an amplifier out of saturation, and this noise can be entirely independent of the feedback mechanism.

 

[vanesch]

Gokul, I agree with everything you write here. The data point to a more complicated dynamics than just the "well, and then the CO2 rises, and this gives then positive feedback which enhances the heating". That can be part of it, but there must be other things. I think that what Andre is pointing at is that it cannot be a simple, direct positive feedback and that's it.

Now, the problem is that this verbal statement is all I've ever read as a support for the core claim of the paleo indications of positive feedback mechanisms, which by itself is one of the basic supports for the higher temperature increases in the IPCC predictions. Let's not forget that the essence of the "dramatic" AGW resides in the existence, or not, of these strong positive feedback mechanisms (and not in the basic greenhouse effect of CO2 itself).

So my question is: is there some paper, where a model is described (essentially a set of dynamical equations with or without free parameters) which can successfully retrodict these paleo data, with the features Andre points out, and if so, what are the dynamical equations used, and what free parameters have been fitted ?

 

[Gokul43201]

I think that what Andre is pointing at is that it cannot be a simple, direct positive feedback and that's it.

Vanesch: I can't even say I understand how that is done. If the signal was cleaner, and we were looking at the correct time scales, then I might understand at least some of that. But, in what we have, the RMS noise level seems to be at least comparable to changes in the signal during the estimated lag or lead times. I just don't understand why there shouldn't be that level of "conflict in trend" (no matter what the transfer function is) in such a noisy signal. The size of this "conflict" seems to be what I would expect from this noise level.

But that's also just some naive intuition on my part. Is this wrong?

 

[vanesch]

Vanesch: I can't even say I understand how that is done. If the signal was cleaner, and we were looking at the correct time scales, then I might understand at least some of that. But, in what we have, the RMS noise level seems to be at least comparable to changes in the signal during the estimated lag or lead times. I just don't understand why there shouldn't be that level of "conflict in trend" (no matter what the transfer function is) in such a noisy signal. The size of this "conflict" seems to be what I would expect from this noise level.

But that's also just some naive intuition on my part. Is this wrong?

I see what you mean. I also just do some eyeballing! The main RMS noise level seems to be rather high-frequency, and I would guess that if one does some linear regression on the 3 parts (the "horizontal" part before the rise, the "rising slope", and then the part in the "conflicting region", that one would find a slight decrease. To do this seriously would require to put up a model and to do a statistical test on the compatibility between the model and the data, and more importantly to have a reliable model of the noise on these data (white noise, red noise, ... ). Now, you said at a certain point that in "saturation" of course the positive feedback is gone now, that's true. However, it cannot be "gone now", and work again at full power for the next rise (unless the model has changed in between). So we have to assume that the positive feedback is working fully in the region between 14 000 and 12000 years, in which case a negative slope is somehow problematic.

Of course, the question is of where the burden of proof resides. If Andre says "I've explicitly demonstrated that no positive feedback mechanism is possible" then that is a strong claim (a kind of no-go theorem), which will need much more proof than just this plot, I agree. It would imply the rejection of the whole family of dynamical models containing a positive feedback, and furthermore an explicit specification of that exact family.

However, it if it is "I emit some doubts about these data to be compatible with a given feedback mechanism as is verbally described on < fill in your preferred AGW blog > ", then I'd say, this is just a request of "show me that famous model of yours that reproduces these data" and which *demonstrates* the existence of that famous positive feedback.

 

[Gokul43201]

Of course, the question is of where the burden of proof resides. If Andre says "I've explicitly demonstrated that no positive feedback mechanism is possible" then that is a strong claim (a kind of no-go theorem), which will need much more proof than just this plot, I agree. It would imply the rejection of the whole family of dynamical models containing a positive feedback, and furthermore an explicit specification of that exact family.

However, it if it is "I emit some doubts about these data to be compatible with a given feedback mechanism as is verbally described on < fill in your preferred AGW blog > ", then I'd say, this is just a request of "show me that famous model of yours that reproduces these data" and which *demonstrates* the existence of that famous positive feedback.

Here's what has been said (in the other thread that he linked):

So I used this high resolution graph of Antarctica's EPICA Dome C ice cores during the last glacial temination between 20,000 and 10,000 years ago, to demonstrate that there is no positive feedback because the typical behavior of positive feedback is not seen.

(emphasis mine)

Maybe it would be a good idea to acknowledge the limitations of that demonstration?

 

[vanesch]

Maybe it would be a good idea to acknowledge the limitations of that demonstration?

It's what I did, no ?

Now, maybe we can make this more explicit, and try to write a kind of toy model that could eventually be refuted by these data, just for the fun of it, like (guessing right here on the spot):

Two state variables, T (temperature) and C (CO2 concentration) ;

dT/dt = A C + B + f(t)

C = U T(t-t0) + V + g(t)

where T(t-t0) indicates a delay, and f and g are external driver functions.

A, B, U and V being the system constants to be estimated. We take it to be a linear model (we could introduce some non-linearities, but then extrapolating this model to other regions of operation is even more tricky).

If it were possible to demonstrate that there exist no 4 numbers A, B, U, and V which make statistically compatible predictions with the data, then we have falsified this toy class of models.

This is a trivial toy model of course. We could start here. It corresponds to the bare bones implementation of the verbal statement about the feedback in its most trivial and simple form.

edit: note that this toy model reduces to something much simpler:
dT/dt = alpha T(t-t0) + beta + gamma(t)

with alpha and beta constants, and gamma(t) a driving function.

 

[Skyhunter]

Vanesch,

Concerning the lower stratospheric cooling, this is usually seen as a proof for CO₂-induced global warming. The simple explanation is that as more IR radiation is withhelt by the lower troposphere, less of it reaches the stratosphere so this one cools.

That is not quite correct. The dominant CO₂ absorption band, 15µm is saturated in the lower atmospheric levels meaning that fewer photons that can be absorbed by CO₂ reach the stratosphere. Carbon dioxide having a zero dipole tends to spontaneously radiate. Hence stratospheric CO₂ radiates away more energy than it absorbs.

http://www.atmosphere.mpg.de/enid/2__Ozone/-_Cooling_nd.html"