The Hockey Stick is Bad Science

I will take the first part of this response to rebut his last points and then summarize my contention. Firstly: there is nothing about the hockeystick that makes cold weather in the Little Ice Age an “impossibility”. It is equally incorrect to say that the hockey stick shows “no climate change” for thousands of years. In my original proposal I explicitly stated that the discussion was about the hockey stick as originally developed and further expanded. As an example of the “change” available in the hockey stick reconstructions throughout its history I provide the following illustration from Mann et al, 2003 [1] There appears to be quite a bit of change in the climate. The problem Pro has with the hockey stick is that it doesn’t show his preferred issues as “large” as he would like them to be. Unfortunately GOOD science is done without preconceived notions. The data fall where they fall. Unless Roy can point to a significant and obvious error in treatment of the data then the data shows what the data shows. Now, mysteriously, Pro wishes to bring up some nefarious hidden actions by Mann and associates and intimates that they are setting out to make software that heavily weights certain data, preventing critics from being published and ultimately resorts to the “climategate e-mails” (which have been examined by numerous panels and none so far have found evidence of fraudulent science). This sounds very much like an accusation of dishonesty. Yet in Round 2 Roy explicitly agreed that the hockey stick was likely honestly undertaken. Here is his exact phrasing: “I won't contest that the derivation of the Hockey Stick was honestly undertaken. The errors were in selcting invalid proxies, not estalishing that the proxies had a physical tie to what was being measured, and using the poxies outside of the range for which they were validated…” It seems that Pro wishes now to recapture a conceded point here. And since none of these issues are related to Pro’s original I cannot allow this. Pro fails to substantively discuss the details of the principal component analysis which underlays the primary critique of McKitrick and McIntyre against Mann. I showed how McKitrick and McIntyre failed and how Mann et al explicitly followed standard statistical procedure (whereas McKitrick and McIntyre explicitly FAILED to follow standard procedure). In order for Pro to make a valid critique of this as “bad science” he must show how the proper application of accepted statistical analyses was in error for Mann and how misapplication (incorrect truncation of the number of PC’s) was somehow ‘correct’ for McKitrick and McIntyre. Wegman’s testimony is very interesting. It would be great if Wegman would take his work to the statistics community via regular publication rather than just testimony before Congress. Perhaps this would open it up to peer review? (Note I am not questioning Dr. Wegman’s statistics at all! Quite the contrary. If I am to believe Roy’s point in the last post if this is a good, legitimate critique it would be best put to the broader statistical community and not just a Congressional Committee). It appears that Wegman spent an inordinate amount of time explaining “social networks” FIRST before launching into a critique of Mann et al. ’s actual statistics. But it is also interesting that Wegman took a swipe at Wahl and Amman’s 2006 paper. Interestingly enough if Wegman wished to question the use of real statisticians it appears that Wahl and Amman actually consulted the National Center for Atmospheric Research’s Geophysical Statistics group head. But again, back on statistics, Wegman appears to have focused on the first PC (Pg 9 of the Testimony) and the impact on centering which was really not controversial to begin with. Wegman was by no means the only statistician in attendance. Hans Von Storch (coauthor of one of the leading books on statistics in climatology) also testified [2], and his testimony found that decentering had only a minor effect on the final outcome after all the PC’s were added into the reconstruction. Interestingly von Storch himself found things he disagreed with in MBH and found the ensuing canonization of the hockey stick should have been moderated. This is par for the course in any scientific publication. This even happens to “good” science! I addressed the regional effects of the choice of the Bristlecone and foxtail pine proxies by reference to the eigenvector-based CFR Technique as discussed in Wahl (2007) and how those were factored in. In addition I noted that Wahl removed that data and still found a single-bladed hockey stick shape to the data. This indicates that it is not clearly just “bad” form for MBH to utilize these techniques. There may be disagreements but is not dispositive for “bad science”. Pro’s repeated reliance on some small circle of Mann’s associates seems somewhat strange since easily more than half of the publications I cited do not include Mann. One is from LDEO, one is from NCAR, one is the IPCC. I feel I have shown a variety of independent sources. Pro also appears to want to expand the debate to the Holocene Optimum and other points in the earth’s history. Indeed the earth has had very warm periods in it. However, these say nothing about the possibility of anthropogenic warming today. The debate here was limited to the proposition of the hockey stick as "bad science". I must say that Pro’s continual reliance on non-peer reviewed citations, congressional testimony, Wikipedia and the Telegraph newspaper in critique of science is somewhat of a mystery to me. SUMMARY In order for science to bad it must be either: Undertaken dishonestly Reliant on such misapplication of standard scientific or analytical techniques as to make it patently obvious to a majority it was flawed In this debate Pro initially agreed that it was not #1 when he stated he felt it was honestly undertaken. And as to the application of standard scientific or analytical techniques I substantively responded to those points and even noted that the primary critiques of McKitrick and McIntyre relied on inappropriate truncation of the principal components. In order for science to be “good” it must be: Honestly undertaken Rely on standard scientific and analytical techniques (or failing that to provide ample explanation of why different techniques were considered Show robust findings Be reproducible I have shown these things to be true of the hockey stick. We both agreed it was honestly undertaken (even if Roy seemed to attempt to backpedal on this point in the recent round), while some may disagree with the techniques chosen, it is not exclusive to MBH. I further provided evidence of the robustness of the analysis by reference to Wahl and Amman (2007). I provided evidence of the reproducibility of the hockey stick in a number of ways relying not just on alternate proxies, but also without reliance on the PCA technique! This does not mean the hockey stick is “perfect”. No science ever is. It cannot be. But it is “good” science in that there is little reason to doubt the results since external groups have analyzed the results, found them acceptable, and even were able to reproduce the hockey stick without reliance on the statistical techniques. Mere disagreement over the outcomes (or rather what some would prefer the outcomes to be) does not equate to science being “bad”. SOURCES Mann, M. E. , Ammann, C. M. , Bradley, R. S. , Briffa, K. R. , Crowley, T. J. , Hughes, M. K. , Jones, P. D. , Oppenheimer, M. , Osborn, T. J. , Overpeck, J. T. , Rutherford, S. , Trenberth, K. E. , Wigley, T. M. L. , On Past Temperatures and Anomalous Late 20th Century Warmth, Eos, 84, 256-258, 2003 House Hearing, 109th Congress - QUESTIONS SURROUNDING THE 'HOCKEY STICK' TEMPERATURE STUDIES: IMPLICATIONS FOR CLIMATE CHANGE ASSESSMENTS (. http://tinyurl.com...)