the Air Vent

Because the world needs another opinion

Hockey Stick Sorting Rejected High Frequency Data

Posted by Jeff Id on September 9, 2008

Something else I saw.  Look at the 3 graphs of the cherry pick the Mann analysis did.

There is a lot more high frequency noise in the rejected dataset.  Statisticians go crazy over in curve fitting analysis. We would expect the faulty correlation algorithm to reject data containing a high frequency signal and it sure did.

Another thing to notice is in the second graph there is a sharp drop in temperature.  Mann makes the claim that this section when heavily smoothed represents the little ice age.  The curve though starts before 1600 AD.  I copied this from Wikipedia –It is generally agreed that there were three minima, beginning about 1650, about 1770, and 1850, each separated by slight warming intervals.[1].

So the proxy data reacted with a sharp downward slope in 1580 more than 70 years before the ice age happened.  Perhaps the tree rings and mollusk shells were the cause of the little ice age!  (I just couldn’t resist that)

A sharp drop in temperature from 600 to 900 years is also evident in the accepted data, where it is flat in the rejected data.  I think this is due to the particular data sets being selected over others.  I need to do an analysis of that also.

Just found it interesting.

4 Responses to “Hockey Stick Sorting Rejected High Frequency Data”

  1. LeeW said

    Personally…I wouldn’t put too much faith in Wiki when it comes to climate information. Wm. Connolley is notorious for editing everything to provide a very historical slant that backs the IPCC view.

    Prior to AGW being a ‘consensus’ view the LIA was widely accepted to have occurred from about the mid 14th century to the mid 19th century. Temperatures were actually colder than Wiki describes based on historical and archeological records (think 1-2C below the mean). (Some info taken from the 2000 edition of the Oxford Comapanion To The Earth)

    This is what makes the LIA stand out in my mind…that they have reduced the LIA to such a ‘minor’ incident. Similar to what happened in the past with reducing the strength and effect of the MWP (going so far as to rename it the Medieval Climatic Anomaly).

    I guess this is why I was curious about regionalizing the proxies to see if there are strong correlations or if certain regions, due to the number of proxies, could be drowning out other regions.

    Sometimes being in charge really sucks…too much time on my hands to contemplate other things!! 🙂

  2. Jeff Id said

    Darn, I was starting to think the shells were doing something.

    The data are sorted according to latitude and longitude. Is there some area you would like to see first? The number of proxies would be limited according to their location, but it would only take 15 minutes or so.

  3. LeeW said

    This could be kind of fun…

    How about 20DN to 50DN and 70DW to 120DW (pretty much N. America)

    and also 35DN to 65DN and 8DW to 50DE (Europe)

  4. Jeff Id said

    Check my home page Lee. Thanks for the suggestion.

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