Tamino v Montford on the Gaspé series

Have just finished reading A.W. Montford’s (alias Bishop Hill) The Hockey Stick Illusion. Although I thought it excellent, and agree with the reviews (e.g. Air Vent), I thought I would look for contrary opinions, to allow me to compare and contrast the different sides. It just so happens that Tamino has posted a critical review at Real Climate blog on July 22nd. Bishop Hill has responded.

In the spirit of allowing you to make up your own mind, let me present one aspect, which does not need a scientific background to evaluate.

Tamino claims that McIntyre rejects Gaspé because

 “This particular series doesn’t extend all the way back to the year 1400, it doesn’t start until 1404, so MBH98 had extended the series back four years by persistence — taking the earliest value and repeating it for the preceding four years. This is not at all an unusual practice, and — let’s face facts folks — extending 4 years out of a nearly 600-year record on one out of 22 proxies isn’t going to change things much.”

 

I would agree with Tamino, if that was the only problem with Gaspé. But other problems Montford recounts.

  1. It had the biggest hockey stick of any of the 112 series. 1975 was 3.05 standard deviations from the series mean. Only 12 others had any sort of hockey stick shape. (p.75)
  2. It was included twice in the proxies – once as part of the North American PC series and once on its own. (p.140).
  3. It did start in 1404, but until 1421 relied on a single tree, and two up to 1447. The original authors “had not used the early portion of the series at all in their own reconstruction”, but Mann had. (p165.)
  4. Mann’s own claim for its’ inclusion was that the study represented the northern treeline. But Gaspé was well south of the treeline. As a sensitivity analysis, McIntyre replaced Gaspé with the Sheenjek River Series in Mid-Alaska. It was further north and had more trees. When this was replaced, the medieval warm period re-appeared. (p.166).*
  5. McIntyre showed “that you could only get rid of the Medieval Warm Period by using the Gaspé series twice and by including the unreliable early portion, and by extending this highly dubious data back to the start of the fifteenth century.”
  6. An updated study was done taking the data to 1991, instead of 1982. There was nothing like the same growth spurt in recent times. The data went unpublished, and the author claiming to have lost the location. So the results could not be independently replicated. (p.174).
  7. Montford says in reply to Tamino

“The observation that “McIntyre argued that the entire Gaspe series should be eliminated because it didn’t extend all the way back to 1400” is wrong. MBH had its steps starting at 50-year intervals. Gaspe should therefore have been in the 1450 step not the 1400 one.”

 

From my simple view, the criticism of the Gaspé proxy series is multilayered. It was used inappropriately; there was a better proxy available (or an update); it was clearly an outlier; and was used twice.

Finally, Steve McIntyre has already criticised Tamino on Gaspé here. McIntyre makes the additional point

“The Gaspé series is a cedar chronology. There is no botanical evidence that cedars respond linearly to warmer temperatures. World experts on cedar are located at the University of Guelph, Ross McKitrick’s university. Ross and I had lengthy discussions with these cedar experts about this chronology – they said that cedars like cool and moist climate.”

 

* Gaspé is around 49o North (same as Paris), Sheenjek River 65o North. (same as Iceland).