Penn State University has announced that it has begun an investigation of the work of Michael Mann, the director of its Earth System Science Center, following revelations contained in the Climategate documents that have emerged from East Anglia University in the UK.How far will this investigation go? To answer, let's consider the last time that Mann got himself in trouble. I mentioned above that he created the famous "hockey-stick" temperature plot in 1999. In 2004, it was exposed that Mann's analysis was riddled with mathematical errors. As a consequence, Congress asked the National Academy of Sciences (NAS) to review the subject of the Earth's temperatures over the past 2,000 years. While the NAS report (PDF) covered a lot of territory, I want to highlight just one illustrative point. The hockey stick plot relied, in part, on temperatures inferred from tree rings, a speciality of another scientist made famous by ClimateGate: Dr. Keith Briffa of the University of East Anglia. There are two issues with tree rings: (a) do they really reflect temperature, as opposed to, say, rainfall, and (b) have we examined tree rings on enough trees that it is a statistically significant reflection of global temperature. Here is how the National Acedemies summarized their answer to the second question:
To prevent the risk that a single tree ring chronology could reflect the influence of localized nonclimatic influences (Fritts 1976, Trotter et al. 2002), dendroclimatic reconstructions often rely on networks of site chronologies. Regional tree ring networks typically have strong intersite correlations (e.g., Hughes et al. 1984, Figure 2), and continental-to-hemispheric-scale networks are able to reproduce synoptic-scale climatological patterns (Fritts 1991, Briffa et al. 2002).In other words, they accepted Briffa's word that he had included enough trees. However, subesequent research showed that (1) the number of trees used by Briffa was indeed very small, and (2) Briffa's entire "global warming" effect is the result of the inclusion of a single tree, designated YAD061.
Why didn't the NAS investigation undercover such a huge flaw? There are two reasons: (i) it would have been an ungentlemanly insult to ask a colleague to produce his raw data and code, and (ii) even if they did ask, it is likely that no one on the NAS committee had the either the time or the interest to pursue it to the level required to expose the fraud/error. So it will likely be with the Penn State investigation of Mann: it will likely be gentlemanly and superficial and nothing interesting will be found.
The NAS was aware of the problem of irreproducible climate results and did, in their gentlemanly way, ask that data and code be released:
Peers should have access to the information needed to reproduce published results, so that increased confidence in the outcome of the study can be generated inside and outside the scientific community. Other committees and organizations have produced an extensive body of literature on the importance of open access to scientific data and on the related guidelines for data archiving and data access (e.g., NRC 1995). Paleoclimate research would benefit if individual researchers, professional societies, journal editors, and funding agencies continued to improve their efforts to ensure that these existing open-access practices are followed.Seemingly because they were aware that their data did not support their conclusion, the Mann, Briffa, and other global warmists refused to follow the NAS suggestion, appearing going so far as to stonewall legal freedom-of-information act requests. Only because of ClimateGate has the University of East Anglia reversed course and offered to do as the NAS asked (but only after claiming to have "lost" key data).