11 September 2008

Revival of the "Hockey Stick"

Surely everyone interested in the climate change debate is well aware of the "hockey stick controversy". There is a new twist to the story: Michael Mann and colleagues just published a new temperature reconstruction in PNAS, confirming that the recent warmth is anomalous for the past 1300 years in the northern hemisphere.
The important point: This holds even if tree rings are not used as climate proxies. One of the more serious concerns about the old hockey stick was that tree rings may not correctly reflect long-term trends but dominated the combined record. The new reconstruction indeed more clearly shows the medieval warm period, but it does not come out as warm as today.
I look forward to a storm in the climate skeptics scene!


  1. Tis then pity that on the September 9 another major statistician Ian Jolliffe who is an expert on the specific techniques used to make the hockey stick refuted the modified statistical method. He refuted the very statistic techniques that skeptics like McIntyre have been saying are flawed, demonstrating the flaws, providing calculations and endless examples of the flaws, now really are independently confirmed to be actually,…. truly FLAWED!!

    ht http://noconsensus.wordpress.com/2008/09/12/global-warming-takes-a-shot-in-the-globes/

  2. Can you explain the "flaw" in your own words, Chris?


  3. I can help you there Bi. Mann centred his proxy series using the mean of the 1902-1980 calibration period rather than the mean of the full series. This meant that the outputs weren't actually principal components at all.

  4. Why do I need to do it in my words? One of the joys of the internet is cut and paste.