Bummer: New Study Finds Tree Ring Proxies “Seriously Compromised”

by William Teach | August 20, 2013 9:59 am

Usually I focus on the politics of “climate change”, throwing in a few facts and scientific data. Here’s a bit of true science I noticed while going through the feedreader

(The Hockey Schtick[1]) More bad news for Michael Mann[2]: A new paper published in Climate of the Past finds that ‘modern sample bias’ has “seriously compromised” tree-ring temperature reconstructions, producing an “artificial positive signal [e.g. ‘hockey stick’] in the final chronology.” Needless to say, Mann’s hockey sticks are also seriously compromised by statistical techniques that produce hockey sticks from random numbers[3], use of upside-down data[4], the trick to hide the decline[5], the most important tree in the world[6], use of bristlecone pines which were condemned by the NAS for use as temperature proxies[7], and a complete lack of validation skill[8].

(From paper excerpt) Dendrochronologists observed that the older a tree was, the slower it tended to grow, even after controlling for age- and time-driven effects. The result is an artificial downward signal in the regional curve (as the older ages are only represented by the slower growing trees) and a similar artificial positive signal in the final chronology (as earlier years are only represented by the slow growing trees), an effect termed modern sample bias. When this biased chronology is used in climate reconstruction it then implies a relatively unsuitable historic climate. Obviously, the detection of long term 15 trends in tree growth, as might be caused by a changing climate or carbon fertilization, is also seriously compromised (Brienen et al., 2012b). More generally, modern sample bias can be viewed as a form of “differing-contemporaneous-growth-rate bias”, where changes in the magnitude of growth of the tree ring series included in the chronology over time (or age, in the case of the regional curve) skew the final curve, especially 20 near the ends of the chronology where series are rapidly added and removed (Briffa and Melvin, 2011).


Analyzing 1200 randomly selected published chronologies, we find that regional curve standardization is improved by adding an effect for individual tree productivity in 99% of cases, reflecting widespread differing-contemporaneous-growth rate bias. Furthermore, modern sample bias produced a significant negative bias in estimated tree growth by time in 70.5% of chronologies and a significant positive bias in 29.5% of chronologies. This effect is largely concentrated in the last 300 yr of growth data, posing serious questions about the homogeneity of modern and ancient chronologies using traditional standardization techniques.

This shouldn’t be anything unexpected: so much of the Warmists so-called science has serious issues, if not outright fraud. It is based on opinions and political biases. The Hockey Schtick also points towards another paper[9] that finds climate models “substantially erroneous” because the models assume the world is flat.

  1. The Hockey Schtick: http://hockeyschtick.blogspot.com/2013/08/new-paper-finds-tree-ring-proxy.html
  2. bad news for Michael Mann: http://hockeyschtick.blogspot.com/2013/08/michael-manns-hockey-stick-graph-is.html
  3. hockey sticks from random numbers: http://hockeyschtick.blogspot.com/2013/08/michael-manns-hockey-stick-graph-is.html
  4. upside-down data: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&cad=rja&ved=0CEkQFjAE&url=http%3A%2F%2Fwattsupwiththat.com%2F2009%2F11%2F27%2Ftold-ya-so-more-upside-down-mann-in-his-latest-paper%2F&ei=twwNUrr3OvGFyQH0y4GADw&usg=AFQjCNEugbZSOlA7zCZyzBIsmdUN7WgABg&sig2=sO8dPLNHvpgEwkabUZGcnA&bvm=bv.50768961,d.aWc
  5. the trick to hide the decline: http://hockeyschtick.blogspot.com/2011/11/climategate-20.html
  6. most important tree in the world: http://hockeyschtick.blogspot.com/2009/12/climategate-reveals-most-influential.html
  7. condemned by the NAS for use as temperature proxies: http://hockeyschtick.blogspot.com/2011/03/there-he-goes-again-mann-claims-his.html
  8. complete lack of validation skill: http://hockeyschtick.blogspot.com/2011/03/there-he-goes-again-mann-claims-his.html
  9. another paper: http://hockeyschtick.blogspot.com/2013/08/new-paper-finds-climate-model-results.html

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