Understanding Growth Response Modeling

As we have continued to argue on the last thread about whether it makes sense to sort trees by ‘sensitivity’ to temperature (it doesn’t), we left off one of the most important critiques of dendroclimatology.   This has been discussed here before in the context of Dr. Craig Loehle’s publication on non-linear tree growth, but it is important that we not forget how critical this issue is in the context of linear regressions.    I am glad to have experts around to keep us on track – Jeff Id

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Guest Post by John F. Pittman.

Below is a response from a temperature sensitive species that has been well documented. Different authors were able to control the nutrition, conductivity, spacing, etc, because these are unicellular plants.  Actually it is two genera and multiple species. The curve represents an idealized single organism. This particular organism has a peak about 91% of maximum growth response and a peak response at about 28 C. So, now we can discuss the errors and incorrect modeling.

 

 

The first constraint of a correct statistically correct biological model is to consider what happens as more individuals are added. The first part we will look at is the area from 5C to 10C. As one adds more and more specimens, the curve will flatten towards the 0% line. The next area is the area above 80% that between 25C and 33C will tend to flatten towards the 80% line. The last is that as one adds more and more specimens the curve tends to go asymptotic to 40C. The reasons have to do with the temperature response of proteins and enzymes, and adaptation of the species wrt time, and acclimation of an individual wrt time, and of course, measurement variance.

 

Now, we can discuss what has been missed, by some, in JeffID’s “Sometimes They Forget” post.  First there is no linear response. Second, any growth measurement has two answers. This was one of the points of Dr. Loehle’s paper. Also, those not familiar with the creation of a skewed bell curve for biological study; the range of temperature can be larger or much smaller. Examples of this are fish that live in extremely hot trapped water systems in deserts, and fish that live in special niches in the arctic.

 

We are going to assume that the sorting that went on and goes on is close to being correct. One can assume the 6 sigma response of certain trees to be correct, but if you understand the model, it means it is worse than what we will discuss for being close to correct. The first point is JeffID’s comments about the de-amplification or amplification of the signal.  In his red noise examples it can be either. In the biological case it can only be one direction, de-amplification when a positive linear assumption is made. The linear model will not detect the temperature going down, since it will be below the threshold of the method’s detection limits at the low end. It will not be able to the temperature change at the top of the bell for the same reason. Finally, by not using the correct curve, there will be the higher temperatures, that will be read as lower temperatures further compacting the response. This is why the handle of the “Hockey Stick” is broken. The red noise series of JeffID and Steve McIntyre will not have the compaction of the series if these trees really are temperature sensitive. Also, where as Steve and Jeff’s results are a probability, using the linear assumption is a guarantee of compaction of the signal in the handle.

 

The proof lies in believe it or not, in the first email of the original Climategate. In this email, Hantemirov, IIRC, stated that sub fossil trees indicated that the tree line was some distance away and was some thousands of years ago, generally known to be warmer that the current warm period. This tells us that the area of interest is somewhere, in our example, in the 0C to 15C region. The other part of the proof is the disbelief by one of the responders in Climategate II, questioning the use of the linear assumption. This indicates that the authors knew or should have known that linear assumption should not be used. Finally, the sad or joyful part is that the divergence actually could be proof that one can use trees as a decent temperature proxy. There will still be de-amplification problems. However, a good decompression routine could be used to great effect on the initial results to obtain a more realistic temperature change profile. Finally, if you want to really understand why it matters and scientists should be skeptical of attribution, you need to read and understand the posts I wrote for JeffID when the first Climategate occurred.

 

John F. Pittman

Sometimes they forget

So I left a comment at RC today bolded below.   The boys are stinging again because they are as good at PR as most engineers I know.

You know the lack of disclosure of data not used, is nearly equivalent to the regression methods which automatically reject data not preferred. The mere fact that the reconstruction with ALL of the data wasn’t published is not enough to counter the obvious possibility of pre-selection.

[Response: In any statistical analysis there is always a possibility of pre-selection to get a signal, or the possibility of trying different combinations until the signal disappears depending on what the conscious or unconscious bias might be. Yet the scientific literature is not full of people saying that other authors are deceptive or guilty of misconduct because they got a different result. No one can ever prove that they didn’t do a calculation, and ever more insistent demands that they must, are pointless. McIntyre is dead wrong here – both in his conclusions and his conduct. – gavin]

The sophistry here is that we have a history of post-hoc selection of methods (hide the decline), brow-beating of those with different results (the Trenberth travesty), and blocking of papers which refute results (many references).  Now we find that many more Yamal region proxy series were available than stated and a reconstruction from such a strong hockey stick temperature region (usually a 3 month project) has taken years to reach the public eye.    Unsurprisingly, now that a basic estimate was published by Steve McIntyre, the data doesn’t seem to support the six sigma Yamal trend. So, in context, the request is hardly unreasonable.

In addition, the problem here is that Gavin understands full well the regressomatic techniques of paleoclimate.  I flatly don’t believe he is too stupid to miss how the auto-enzyte algorithms work.  To sum up: The likelihood of Gavin’s misunderstanding of the probability of a paleoclimate regression (post-selection) to get a signal (hockey stick), is inverse to the probability of actually finding said signal.   IOW, he knows damned well how this works.

Of course even Steve’s obviously non-temperature result will work fine in a RegEM, TTLS, TLS, etc……   regression.  When doing multivariate regression, noise works fine for creating unprecedented temperatures.

Some Unsolicited Advice to Heartland

It looks like I missed quite a bit over the last couple of weeks. Not only have I not been writing, I haven’t done any reading!   Very unusual  for me.   I had to check if global warming was still happening, whether the sea still had ice and whether climategate 3.0 had broken out.

It turned out pretty much as before except for the Heartland institute exhibiting Gleick-like reasoning skill.   WTF?!  Hell, every time I turn around someone does something so rock bottom stupid that it is difficult to get your head around.   Then I see people withdrawing from a conference over this and wonder why.

Here is how I see it.   Heartland is a  group, not an individual.   A group will always have individuals which make mistakes.   These things are correctable.   Apologies and terminations/reassignments are in order but to chuck the message out over this stupidity, and it was spectacularly stupid, is silly.   When I can make a better PR judgment than your hired PR professional, you need to hire a new professional. They took the dumb add down and issued an apology but I haven’t heard of any terminations yet.  It is painfully obvious that whomever approved the ad. is completely out of touch with those who understand physics and still don’t see climate doom in our future. It is also obvious that they are unaware of the progress being made within the science.

Reality trumps all arguments.

My advice to Heartland is to first, improve the apology.  Making mistakes will not hurt you when you admit them.  Second, find new advisors who can detect something so blatantly extreme.  Extremism is the shelter of the slow witted, and that was really slow! Third, recognize that your organizational message will only generate a specific amount of attention.   If you are looking to grow your organizational cash beyond that limit by efforts other than content, it will absolutely fail in the scientific arena on which all sides of AGW are rooted.  Keep the message reasonable in all cases no matter what the goals are and you will maximize your results.

Of course, I don’t run a non-profit but I did warn another one.

Ironically, I run a blog which is premised on venting.  The difference is that this is for fun and I am not looking for a maximized result.

Steve McIntyre – FOI Granted

Long time readers will be familiar with the Yamal saga.   Yamal is the name of a region which allegedly demonstrated proof of extreme recent warming in tree ring data.  Recently, after years,  Steve McIntyre was granted access to the total dataset site list.

Unsurprisingly for paleoclimatology, the results using all of the data are a little different.