A 2021 study appearing in Nature Communications by Buentgen et al reports on the results of a double-blind experiment of 15 different groups that yielded 15 different Northern Hemisphere summer temperature reconstructions. Each group used the same network of regional tree-ring width datasets.
Hat-tip: Klimaschau 108
What’s fascinating is that ll groups, though using the same data network, came up with a different result. When it comes to deriving temperatures from tree-rings, it has much to do with individual approach and interpretation. Sure we can follow the science, but whose results?
The 15 groups (referred to as R1–R15) were challenged with the same task of developing the most reliable NH summer temperature reconstruction for the Common Era from nine high-elevation/high-latitude TRW datasets (Fig. 1):
Cropped from Figure 1, Buentgen et al
The 15 groups who contributed independently to this experiment all had experience in developing tree ring-based climate reconstructions. But as the study describes, each group employed a distinct reconstruction approach. In summary, the results ranged by as much as 1°C.
How could the groups come up with different results?
The paper’s abstract summarizes: “Differing in their mean, variance, amplitude, sensitivity, and persistence, the ensemble members demonstrate the influence of subjectivity in the reconstruction process. We therefore recommend the routine use of ensemble reconstruction approaches to provide a more consensual picture of past climate variability.”
Why just look at subjectivity? There is systematic time of measurement bias as well.
The fundamental problem with tree ring studies is that they only look at the growing season and for many reconstructions at high elevation or in the arctic, that means a 3-4 month view of the annual temperature record. And then where you have recent data that includes both instrumental and tree ring data, the instrumental part in the arctic shows little temperature change in the growing season and a big rise in the cold dormant season. It’s not wonder Michael Mann had to snip off nearly 40 years of data in his infamous “nature trick”, the full year instrument data did not correlate at all with the tree ring data. Given what I’ve read, the instrumental data from the growing season only might have correlated much better.
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Consensual picture of science!!!
That’s the stuff that made the earth flat for centuries/millenia.
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Tree ring reconstructions are, therefore, as much art as science –so much for following the science.
And they are all right!
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[…] by Buentgen et al reports on the results of a double-blind experiment of 15 different groups that yielded 15 different Northern Hemisphere summer temperature reconstructions. Each group used the same network of regional tree-ring width […]
[…] Follow the Science: But Which Results? Using Same Tree Ring Dataset, 15 Groups Come Up With 15 Diffe… […]