Reconstructions can use proxy data (i.e., tree-rings, ice cores, eetc.); however, they are not used as proxy data to build reconstructions/
For there to be a precipitation signal in the Hockey Stick, they would have had to calibrate the proxy data against the historic precipitation record.
Show me where that was done.
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>>Some of the proxies used to make it were precipitation proxies. Some were actual precipitation records.<<
No - neither - none. No proxy precipitation data - no real precipitation data - at all.
>>Reconstruction use proxy data but not as proxy data? <<
Proxy data are natural archives of climate variables; for example, tree-ring, ice core, varve, and pollen data.
Reconstructions are mathematically generated models that are derived from the analysis of proxy data and actual climate data.
They may be "proxies" (as in "something that represents the value of another thing in a calculation) of temperature in some general sense, but they are never used as proxy data (because the are not proxy data) in building reconstructions.
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>>Well tree rings can be used as proxies for both temperature and precipitation. Logic follows then that precipitation can be used as a proxy for temperature and vice versa.<<
It does not follow at all. Just because it is possible to decompose multiple signals from a larger signal does not mean that every component signal can be used as a proxy for every other component signal.
In tree-ring series, joint precipitation and temperature signals are usually derived by calibrating the tree-ring data with drought indices like the Palmer Drought Severity Index (PDSI) - which is an empirically calculated nonlinear combination of lagged precip, temp, soils, etc. - that is completely independent of the tree-ring data.
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Could you provide some information with your references? That is just a list of file names.
In any case, it is possible – in fact, it is a reality – that tree-ring data contain both temperature and precipitation signals (because those two variables can both influence growth every year).
Think of it like a cord made of many difference pieces of rope intertwined together (and say that some of the ropes are red and some of the ropes are blue). If you want to make a temperature reconstruction, you unwind the cord and take all of the red pieces of rope – and twist them into a red length of cord. If you want to build a precipitation reconstruction, you unwind the cord and take all of the blue pieces of string – and twist all of the blue ropes into one piece of blue cord.
Now, you have two separate things that are completely different even though you got them from the same place.
In the real world, you never have the same number of blue and red pieces of rope in the same cord, so different cords (i.e., trees) have more of one than the other. Mixing them (as some liar has been telling you) only weakens them. And – most importantly - if Mann did that (he did not, but if he did), the precipitation data (pieces of blue rope) would have grouped together as one or two PCs in the PCA – that would not have entered the equation with the actual temperature data and, therefore, they would not have been included – at all – in Mann’s temperature reconstruction.
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Let’s try this another way.
Proxy data are physical things (like tree-rings) that you can hold in your hand and measure.
Reconstructions are not physical things – you cannot hold them and you cannot measure them.
Gary F,
From what I am seeing, tell me if this is fairly accurate. The biggest determining factor in the thickness of the tree ring is the amont of precipitation.
Wetter= more growth, dryer=less growth.
The second largest determining factor is temperature.
Warmer=more growth, colder = less growth.
You then use the precipitation levels from other proxies or reconstructions to factor out the precipitation effect in the thickness of the tree rings, in order to determine the temperature effect.
That about right?
If so, then please note that you are inherently saying that warmer, wetter environments are better for plant growth. You are further saying that AGW will lead to warming AND place more water into the atmosphere. Right?
Then wouldn't it makes sense to say that overall the effect of AGW will be helpful to plant life and thus crop production?
Note that I am NOT saying AGW is good. Possible flooding of coastal regions could be extremely costly. My point is simple. If you want to be believed, you cannot be saying two opposing statements at the same time.
Well tree rings can be used as proxies for both temperature and precipitation. Logic follows then that precipitation can be used as a proxy for temperature and vice versa.
Unless, of course, the first statement is incorrect. And then, as you alluded to, the use would have to be shown to be appropriate. And that seems to be a trump card in many reconstructions and is the focal point for criticism (e.g. Steve McIntyre).
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yes
MBH98 hockey stick paper uses precipitation reconstructions and instrumental precipitation records as proxies for temperature in its regression algorithm. Is this appropriate?
