With all the wild accusations flying around over the illegally obtained email correspondence from the University of East Anglia Climate Research Unit, I thought I would ask one of the scientists in the middle of the issue to provide some context.
Penn State University climate scientist, Dr. Michael Mann, whose name appears in some of the stolen emails, provided me with a run-down of the emails that involve him. His responses provide some much needed context and give you an idea of just how wildly some people have blown this story out of proportion.
What follows is quotes taken directly from the stolen emails, followed by Dr. Mann's response:
1. "I've just completed Mike's Nature trick of adding in the real temps to each series for the last 20 years (i. e. from 1981 onwards) and from 1961 for Keith's to hide the decline." (from Phil Jones).
Phil Jones has publicly gone on record indicating that he was using the term "trick" in the sense often used by people, as in "bag of tricks", or "a trick to solving this problem ...", or “trick of the trade”.
In referring to our 1998 Nature article, he was pointing out simply the following: our proxy record ended in 1980 (when the proxy data set we were using terminates) so, it didn't include the warming of the past two decades.
In our Nature-article we therefore also showed the post-1980 instrumental data that was then available through 1995, so that the reconstruction could be viewed in the context of recent instrumental temperatures. The separate curves for the reconstructed temperature series and for the instrumental data were clearly labeled.
The reference to "hide the decline" is referring to work that I am not directly associated with, but instead work by Keith Briffa and colleagues.
The “decline” refers to a well-known decline in the response of only a certain type of tree-ring data (high-latitude tree-ring density measurements collected by Briffa and colleagues) to temperatures after about 1960.
In their original article in Nature in 1998, Briffa and colleagues are very clear that the post-1960 data in their tree-ring dataset should not be used in reconstructing temperatures due to a problem known as the "divergence problem" where their tree-ring data decline in their response to warming temperatures after about 1960.
“Hide” was therefore a poor word choice, since the existence of this decline, and the reason not to use the post 1960 data because of it, was not only known, but was indeed the point emphasized in the original Briffa et al Nature article. There is a summary of that article available on this NOAA site.
