Home > AGW, Climate Change, Data, Global Warming, Omniclimate, Science, Skepticism > Two Graphs To Dismiss Mann

Two Graphs To Dismiss Mann

From The Air Vent’s Online Experiment With the Latest Hockey Stick:

Data used by Mann for extrapolation

Data used by Mann for extrapolation

Data used vs not used for extrapolation by Mann

Data used vs not used for extrapolation by Mann

Mann used a select few data sets to paste an up slope on the end of 90% of the data in his latest paper. The series used to make the pink line above could have been used in the process but were conveniently eliminated from the paper without mention. […] It [is] my guess that these series would have a reduced up slope compared to the data selected in the last 50 years […]

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  1. 2008/10/18 at 20:49

    Geoff,

    I try to make my Air Vent blog a bridge to the general public. Still the actual information is pretty complex.

    What is pasted on the end is more proxy data, pre-selected by an unexplained process. A fancy technique called RegEM with math that creates discussion among statisticians pastes the data from 55 selected proxies to 1083 existing proxy series. To me it seems deliberately designed to confuse the issue.

    The link above is a plot of the data used for pasting vs the data rejected for unknown reasons. It turns out that the rejected data didn’t have the nice upslope at the end.

    The bottom line is, a hockey stick was pasted on the end of 90percent of the individual data series and a statistically invalid process was used to make it stand out.

    Thanks for carrying my post.

  2. geoff chambers
    2008/10/17 at 22:27

    The discussion at Climate Audit and Air Vent is highly technical and therefore limited to professional statisticians. Perhaps you could enlighten me on two questions from a non-scientist:
    1) What is being tacked on to the handle of the hockey stick? Is it real temperatures, or more proxies (tree ring widths, etc)? What exactly is supposed to be going up?
    2) From discussion at Climate Audit, it seems much dendrochronology is conducted at the treeline, the furthest point north (in the northern hemisphere) or upwards (on a mountain) that a particular tree can grow. Why is this? If a cold period should ensue at this point (a mini ice age) wouldn’t that kill off most of the relevant species and so destroy the evidence for this particular climactic event? In other words, isn’t sampling at the (current) treeline automatically begging the question as to whether there were significant climactic variations in the past (which might have killed off relevant samples?).
    grazie e buon coraggio

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