Sunday 29 November 2009

Excerpts from Climategate

"So, at this stage I would argue that the Medieval Warm Period was probably a global extra-tropical event, at the very least, with warmth that was persistent and probably comparable to much of what we have experienced in the 20th century. However, I would not claim (and nor would Jan) that it exceeded the warmth of the late 20th century. We simply do not have the precision or the proxy replication to say that yet. This being said, I do find the dismissal of the Medieval Warm Period as a meaningful global event to be grossly premature and probably wrong. Kind of like Mark Twain's commment that accounts of his death were greatly exaggerated. "

Later that day...

"I am not saying that Tom's results are wrong. And, I am certainly not saying that Broecker is right. I merely described the results of a new analysis of a somewhat new set of long tree-ring records from the extra-tropics. My statement that the MWP appeared to be comparable to the 20th century does not imply, nor was it meant to imply, that somehow the 20th century temperature is not truly anomalous and being driven by greenhouse gases. To quote from my email, "I would not claim (and nor would Jan) that it exceeded the warmth of the late 20th century. We simply do not have the precision or the proxy replication to say that yet." Note the use of the word "precision". This clearly relates to the issue of error variance and confidence intervals, a point that you clearly emphasize in describing your series. Also note the emphasis on "late 20th century". I think that most researchers in global change research would agree that the emergence of a clear greenhouse forcing signal has really only occurred since after 1970. I am not debating this point, although I do think that there still exists a signficant uncertainty as to the relative contributions of natural and greenhouse forcing to warming during the past 20-30 years at least. "

Dr. Edward R. Cook, Doherty Senior Scholar, Tree-Ring Laboratory, Lamont-Doherty Earth Observatory, from 2nd May, 2001

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