Sunday, December 6, 2009

Mann-Made Warming

I read the Wegman Report last night, and I think I now understand how Michael Mann's statistical methods produce the Hockey Stick from random input data. I have described the process here. In brief: his method assumes the accuracy of the global surface trend (CRU trend) and calibrates all other series with respect to the rising temperatures of the 20th century. If a series shows a rise in the 20th Century, it is added to the result with greater weight. If a series shows a decline in the 20th century, the decline is flipped around so that it becomes a rise. Data with no trend in the 20th century is added last and with less weight. The result is a hockey stick almost all the time when you combine ten random (red nose) series with the CRU trend.


  1. I added the following to the Hockey Stick Wikipedia entry.

    "The report found that the MBH method creates a hockey-stick shape even when supplied with random input data (Figure 4.4). The MBH method uses weather station data from 1902 to 1995 as a basis for calibrating other input data. "It is not clear that Dr. Mann and his associates even realized that their methodology was faulty at the time of writing the MBH paper. The net effect of the decentering is to preferentially choose the so-called hockey stick shapes." (Section 4)"

    Within five hours, it was gone. I re-entered it. Someone is watching the page to make sure that the central conclusion of the Wegman report does not appear there.

  2. Another two hours later, my Wikipedia entry is gone again. Someone is being vigilant about keeping the most important conclusion of the Wegman report out of the Wikipedia entry describing the Wegman report.

  3. I changed "found" to "claimed" and added "they argued" elsewhere, posted on Sunday night, and the addition is still present mid-day Monday.

  4. Now there is a full-blown debate going on in the Discussion section of the Hockey Stick controversy page, and I am happy to say I have allies.

  5. Wow, Kevan, the only thing you're missing is the fuzzy pictures of black helicopters.

    Really, I suggest you pull back and learn more basic and moderate level statistics from a textbook or a class, before continuing your excursions into territory that you really don't understand. You remind me of students who come to class full of preconceptions and who always challenge instead of ask.

    Maybe Tamino is right about you not wanting to learn. Too bad.

  6. Well, there's a black helicopter feeling going around these days. It's Climategate. CRU fabricated a tree-ring graph by substituting temperature data, and NASA did the same thing. They admit it freely. Gavin Schmidt admitted it to me personally, in writing, and said that this year they did better: they simply cut off the inconvenient data. So, these guys are fiddling their data in a way that I, fool that I may be, would not tolerate from one of my students or colleagues. Therefore, I have been curious to find out how deep the fiddling goes. There is a time an a place to suspect a group of scientists of deception and fraud. This one of those times, and climate scientists are the group.