Category Archives: Mann PC1

The Hockey Stick and the Milankovitch Theory

The 20th century warming counters a millennial-scale cooling trend which is consistent with long-term astronomical forcing. MBH99 According to the UMass researchers, the 1,000-year reconstruction reveals that temperatures dropped an average of 0.02 degrees Celsius per century prior to the 20th century. This trend is consistent with the “astronomical theory” of climate change, which considers […]

The Sheep Mountain Update

This post contains an important calculation, which will affect the many multiproxy studies in which Graybill bristlecone chronologies impact results either directly or via Mann’s PC1. Hans Erren has digitized the data from the Ababneh Thesis. In Figure 1 below, I’ve shown the difference between the updated Sheep Mountain chronology and the Graybill chronology. The […]

Bürger Comment on Osborn and Briffa 2006

Gerd Bürger published an interesting comment in Science 2006 on cherry-picking in Osborn and Briffa 2006. A few CA readers have noticed the exchange and brought it to my attention. Eduardo Zorita (who I was glad to hear from after our little dust-up at the Nature blog) sent me the info as did Geoff Smith. […]

Wegman's replies to Stupak

I know this is well after the event, but Dr Wegman’s extensive and detailed responses to Rep Stupak‘s written questions are interesting reading. I’m not aware that Steve linked to this document before. Beware though: the file is 10MB in size, so I’d recommend a right click followed by “Save Target as” – otherwise your […]

Hegerl Proxies: #1 – Mann PC1

The Hegerl et al 2006 climate reconstruction is finally online here . I’m going to go through the proxies individually before talking about method. Obviously the first one to look for is Mann’s North American PC1. Although they say that they’ve “moved on”, Mann’s PC1 was used in Osborn and Briffa 2006 and was one […]


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