Jean S writes (transferred from a comment with the addition of a few headings):

A question for the experts: is it known who wrote and who were used as experts in the EPA documents? If not, is that information considered public (i.e., obtainable under FOIA or similar)?

The reason I ask is that I get very, very eerily feeling when reading certain parts of the EPA decision, especially . For instance, I think there are very, very few people in this world from whom the following paragraphs could originate (considering style, content and astonishing familiarity with Mann’s work):



Response 1-2

Loehle (2009) is a more theoretical study examining the implications for reconstructions if the reason for “divergence” results from a non-linear response of trees to warming. He shows that if the trees respond quadratically to warming rather than linearly, then it is possible that reconstructions using these trees would not reproduce some historical warm periods. However, these questions are not new: the possibility of such non-linear response was addressed in a qualitative form by the NRC (2006). Additionally, some reconstructions have examined the effect of not including any tree rings whatsoever and still find that modern warming is slightly larger than other events in the past millenium (Mann et al., 2008).

Response 1-16

The petitioners presented a reconstruction from Loehle and McCulloch (2008) that claimed that without using tree rings they could show that the average of the warmest three decades of the MWP was a little warmer (though not in a statistically significant sense) than the three decades ending in 2006. The paper uses the straight average of 18 proxies, apparently with no attempt to weight the proxies to take into account the geographic distribution of the sites or the strength of their ability to detect temperature changes. In contrast, Mann et al. (2008) presented reconstructions both with and without tree rings, using geographic and other weighting corrections, and unlike Loehle (2008), they found that “Recent warmth appears anomalous for at least the past 1,300 years whether or not tree-ring data are used.”



Response 1-9

We also note that there have been a number of peer-reviewed critiques and discussions of the McIntyre and McKitrick analyses (e.g., Rutherford et al. 2005, Juckes et al. 2007, von Storch and Zorita 2005, Huybers 2005, Wahl and Amman 2007). These papers question the validity of some aspects of the McIntyre and McKitrick critiques and find that correcting for other valid aspects of the critiques have “no significant effects on the reconstruction itself” (Wahl and Amman, 2007).

Response 1-70

EPA stated in Response 1-70

As background, Soon et al. critiqued the application of the smoothing algorithm used by Mann and Jones (2003) at the very end of the time period that was analyzed. The algorithm is a 20-year average, and a decision must be made about what temperature to use for the last 10 years. For example, one could choose to reflect the end of the temperature record (making the years after the end of the record a mirror image of the years before the end of the record), or assume that all years after the last year of the record are equal in temperature to the last year, or assume that the subsequent years continue the trend of the previous years in the record. Soon et al. felt that application of this “data padding” (though they were not able to exactly duplicate Mann and Jones) led to unjustifiably high temperatures at the end of the smoothed temperature record. A subsequent peer-reviewed rebuttal of Soon et al.’s critique was published by Mann (2004). Mann (2004) states that “Comparisons that are uninformed (e.g., Soon et al., 2004) by objective evaluation criteria (e.g., MSE [Mean Square Error]), are unlikely to provide useful insights into the relative merits of alternative boundary constraints.” Mann’s contention is that there needs to be an objective way to evaluate which smoothing routine to use. While he does not claim that MSE is necessarily the best function, he notes that Soon et al. do not use any objective criteria at all. His analysis also suggests that his approach will choose methods that reflect the underlying trends in the data, whereas smoothing that does not use the MSE criteria can generate spurious trends.

The claim that Mann (2004) is a “rebuttal of Soon et al.’s [2004] critique [of Mann & Jones (2003)]” was new to me. And I think I know Mann’s work pretty well. After some research, I found out that the claim had been made at least once before, in by mike and gavin:

Next, we consider the paper by Soon et al (2004) published in GRL which criticized the way temperature data series had been smoothed in the IPCC report and elsewhere. True to form, contrarians immediately sold the results as ‘invalidating’ the conclusions of the IPCC, with the lead author Willie Soon himself writing an opinion piece to this effect. Once again, a few short months later, a followup article was published by one of us (Mann, 2004) that invalidated the Soon et al (2004) conclusions, demonstrating (with links to supporting Matlab source codes and data) how (a) the authors had, in an undisclosed manner, inappropriately compared trends calculated over differing time intervals and (b) had not used standard, objective statistical criteria to determine how data series should be treated near the beginning and end of the data. It is unfortunate that a followup paper even had to be published, as the flaws in the original study were so severe as to have rendered the study of essentially no scientific value.

In the light of the last statement it is interesting to notice the dates in the papers (additionally it is “unfortunate” that mike even had to revisit the topic in 2008).

Soon et al:

Received 24 November 2003; revised 17 December 2003; accepted 24 December 2003; published 14 February 2004

Mann:

Received 23 January 2004; revised 10 March 2004; accepted 18 March 2004; published 15 April 2004

Update: Jean S has directly asked Mann and Schmidt whether they were involved in writing the EPA documents:

@ClimateOfGavin @MichaelEMann Were you involved in writing of EPA’s Denial of Petitions? http://www.epa.gov/climatechange/endangerment/petitions.html …



