"The data are
attached to this e-mail. They go from 1402 to 1995, although we usually
stop the series in 1960 because of the recent non-temperature signal that
is superimposed on the tree-ring data that we use. "
So who of the discussing people is well versed enough in tree-ring data to have an informed opinion on this? It sounds as if in recent times tree-ring data has to be read differently (which seems possible, other factors could affect growth, don't know).
Donald Keiller a plant physiologist at the University of Anglia wrote Briffa this October:
"1) The appropriateness of the statistical analyses employed
2) The reliance on the same small datasets in these multiple studies
3) The concept of "teleconnection" by which certain trees respond to the "Global Temperature Field", rather than local climate
4) The assumption that tree ring width and density are related to temperature in a linear manner.
Whilst I would not describe myself as an expert statistician, I do use inferential statistics routinely for both research and teaching and find difficulty in understanding the statistical rationale in these papers. As a plant physiologist I can say without hesitation that points 3 and 4 do not agree with the accepted science."
"I really wish I could be more positive about the Kyrgyzstan material,
but I swear I pulled every trick out of my sleeve trying to milk
something out of that. It was pretty funny though - I told Malcolm
what you said about my possibly being too Graybill-like in evaluating
the response functions - he laughed and said that's what he thought
at first also. The data's tempting but there's too much variation
even within stands. I don't think it'd be productive to try and juggle
the chronology statistics any more than I already have - they just
are what they are (that does sound Graybillian). I think I'll have
to look for an option where I can let this little story go as it is.
Not having seen the sites I can only speculate, but I'd be
optimistic if someone could get back there and spend more time
collecting samples, particularly at the upper elevations.
Yeah, I doubt I'll be over your way anytime soon. Too bad, I'd like
to get together with you and Ed for a beer or two. Probably
someday though.
Cheers, Gary
Gary Funkhouser
Lab. of Tree-Ring Research
The University of Arizona"
Doesn't that message support the reading "drat, I can't filter out enough noise to make it statistically significant, so I don't have anything to publish"? (Genuine question.)
Publish or perish. This all sounds very normal to me. I don't see references to making data fit, rather it sounds as if he is looking for a ways to extract some useful information from it.
Anyway, you know what: people believe what they want to believe. This discussion is completely pointless.
I am not well-versed in dendroclimatology, but I believe this issue is described here and is uncontroversial:
Briffa, K.R., Schweingruber, F.H., Jones, P.D., Osborn, T.J., Shiyatov, S.G. and Vaganov, E.A., 1998
"Reduced sensitivity of recent tree growth to temperature at high northern latitudes."
Nature 391, 678-682 (R)
Basically, since tree-ring density is influenced by temperature, you can use it to reconstruct temperatures. I believe the data set in question uses maximum latewood density (MXD), which accorded well with instrumental temperature readings until 1960, at which point they begin to show a decline in temperature while thermometers show an increase. The proposed solution is simply: Don't use the reconstructed temperatures after 1960, since they're wrong.
We're being asked to believe that starting around 1960 tree rings "suddenly" no longer reflected local temperatures, so we shouldn't rely on them after 1960.
Doesn't this also imply that looking backward tree rings might be untrustworthy any earlier than some starting date? That in fact tree rings might work for a while, then vary for a while, then work again? How can anybody honestly claim that SOME tree ring evidence is usable and SOME is not -- and they know exactly which is which?
My bet would be the thermometers are wrong and the tree rings right. See, e.g.,
I would assume that if thermometer data is available, it is being used.
As for trusting tree ring data, this is an entirely different issue from this "Climate Gate" affair. That was, btw., an internal email, so nobody was supposed to trust anything. It was scientists exchanging some data. Surely it is allowed to LOOK at tree ring data.
I agree. We need an explanation _why_ tree ring data suddenly becomes unreliable in 1960, exactly when tree rings stopped showing global warming.
These scientists are asking us to trust their thermometer readings alone, starting at exactly the date when tree rings began disagree with their hypothesis. We need a very very good explanation for this incredible coincidence.
Here's your explanation: because tree rings represent an indirect measurement requiring a set of assumptions, while temperature measurements are direct measurements and require none. In the event of a conflict, trust the direct measurement over the indirect one.
"The data are attached to this e-mail. They go from 1402 to 1995, although we usually stop the series in 1960 because of the recent non-temperature signal that is superimposed on the tree-ring data that we use. "
So who of the discussing people is well versed enough in tree-ring data to have an informed opinion on this? It sounds as if in recent times tree-ring data has to be read differently (which seems possible, other factors could affect growth, don't know).