For background reading, here is a recap of major studies in the debate concerning whether proxies for temperatures - tree rings, glaciers, etc. - are sufficient to accurately detect climate change. For those of you who follow the news, you'll probably have a hazy recollection of media reports that correspond to these studies - Mann 1999 (MBH1999), based on proxies like tree rings used in the absence of long-term historical temperature records, suggested that the recent rising levels of atmospheric CO2 were associated with rising global temperatures, with the proviso that "we focus not just on the reconstructions, but on the uncertainties therein, and important caveats." In 2004, Mann (MBH2004) published data corrections. Mann was most quoted in the media regarding the claim that the 1990s were the hottest decade in the last 1000 years. von Storch (2004) concluded that the prior assumptions about the relationship between temperature proxies and past temperatures was flawed and may be off by a factor of two. McIntyre (2005) pointed out that if randomn noise is entered in the model that Mann used, a hockey puck pattern is always produced. See Kerr (2005) for a science news summary of the dispute. Several reports have addressed the ongoing expert disagreement on whether proxies are sufficient to detect climate change and to distinguish bewteen human induced and natural variations. IDAG (2004) reviewed their prior findings in light of recent criticisms on whether proxies are sufficiently accurate to detect climate change and concluded that: "These observed climate changes are very unlikely to be due only to natural internal climate variability, and they are consistent with the responses to anthropogenic and natural external forcing of the climate system that are simulated with climate models. The evidence indicates that natural drivers such as solar variability and volcanic activity are at most partially responsible for the large-scale temperature changes observed over the past century, and that a large fraction of the warming over the last 50 years can be attributed to greenhouse gas increases." Id. (Abstract). and that - "Additional uncertainties, such as the effect of differences in model fingerprints and simulations have meanwhile been addressed. It has been demonstrated that averaging fingerprints from multiple models increases our confidence in detecting anthropogenic climate change and that different implementations of the optimal detection method show consistent results. New detection studies show that anthropogenic climate change is detectable in the surface temperature records of individual continents and that it can be distinguished from climate change due to natural forcing." Id. at 24. The U.S. House Committee on Energy and Commerce and the House Subcommittee on Oversight and Investigations requested a scientific ad hoc committee of statisticians to review "whether or not the criticisms of Mann et al. are valid and if so, what are the implications. To this end, Committee staff asked for advice as to the validity of the complaints of McIntyre and McKitrick [MM] and related implications." Ad Hoc Committee Report on the "Hockey Stick" Global Climate Reconstruction, a.k.a. the Wegman Report (2005). Wegman (2005) validated MyIntyre's criticisms that Mann's methods were statistically flawed as to claims that the 1990s was the hottest decade in the last 1000 years: "Our committee believes that the assessments that the decade of the 1990s was the hottest decade in a millennium and that 1998 was the hottest year in a millennium cannot be supported by the MBH98/99 analysis." Id. at 49. "In general, we find the criticisms by MM03, MM05a and MM05b [McIntyre and McKitrick] to be valid and their arguments to be compelling." Id. at 48. The Ad Hoc Committee went further and described Mann and others as politically motivated: "Based on the literature we have reviewed, there is no overarching consensus on MBH98/99. As analyzed in our social network, there is a tightly knit group ofindividuals who passionately believe in their thesis. However, our perception is that this group has a self-reinforcing feedback mechanism and, moreover, the work has been sufficiently politicized that they can hardly reassess their public positions without losing credibility." Id. at 65. However critical the statisticans in the Ad Hoc Committee Report were of Mann, both professionally and personally, in Appendix "B" to the Wegman Report, Committee went on to emphasize that global warming, in their opinion, a fact. The Ad Hoc Committee answered various questions posed by the House, and stated that: "There is strong evidence from the instrumented temperature record that temperatures are rising since 1850 and that global warming is a fact. How accurate the reconstructions over the past millennium are is a matter of debate and we do not believe there is a consensus on this issue." Id. at 65. "Our perception is that principal components (statistical) analysis was used incorrectly and, based on this, unsupportable inferences were drawn about the current magnitude of global warming relative to the historical past. We hasten to repeat that the Earth is getting warmer. What does not appear to be true is that the process mechanism is as well understood as some scholars would have us believe." Id. at 66. "In a real sense the paleoclimate results of MBH98/99 are essentially irrelevant to the consensus on climate change. The instrumented temperature record since 1850 clearly indicates an increase in temperature. Whethe this is unprecedented in the last millennium seems less clear and to what extent the natural planetary processes can mitigate the excess green-house gas release is unknown." Id. at 66. National Research Council of the National Academy of Sciences (2006) undertook a study of the debate pursuant to a request by Committee on Science, U.S. House of Representatives. The NRC was asked "asked to describe and assess the state of scientific efforts to reconstruct surface temperature records for the Earth over approximately the last 2,000 years." The NRC's conclusions were: 1) The instrumentally measured warming of about 0.6 deg C during the 20th century is also reflected in numerous proxies like glaciers and can be simulated with climate models. 2) Large-scale surface temperature reconstructions yield a generally consistent picture of temperature trends during the preceding 1000 years. 3) "It can be said with a high level of confidence that global mean surface temperature was higher during the last few decades of the 20th century than during any comparable period during the preceding four centuries." 4) "Less confidence can be placed in large-scale surface temperature reconstructions for the period from A.D. 900 to 1600. Presently available proxy evidence indicates that temperatures at many, but not all, individual locations were higher during the past 25 years than during any period of comparable length since A.D. 900." 5) "Very little confidence can be assigned to statements concerning the hemispheric mean or global mean surface temperature prior to about A.D. 900 because of sparse data coverage and because the uncertainties associated with proxy data and the methods used to analyze and combine them are larger than during more recent time periods." The Stern Report (2006) starts from the point that the hockey puck is largely settled or at least irrelevant in light of the temperature record since 1850. The Stern Report asks what are the likely economic, social and human misery effects from various warming scenarios. A summary of the above can be found in the Wikipedia entry on "Temperature record for the last 100 years" and in Box 1.1 of the Stern Report. http://en.wikipedia.org/wiki/Temperature_record_of_the_past_1000_years - Kurt International Ad Hoc Detection group (IDAG). 2005. Detecting and attributing external influences on the climate system: a review of recent advances, Journal of Climate 18: 1291-1314 http://www.cccma.bc.ec.gc.ca/papers/fzwiers/idag_2004.pdf Kerr, R.A. Feb. 11, 2005. Global Warming: Millennium's Hottest Decade Retains Its Title, for Now. Science 307(5711):828-829 http://www.geo.utexas.edu/courses/387h/PAPERS/Kerr.pdf Mann, M.E., Bradley, R.S. and Hughes, M.K. 1999. 'Northern hemisphere temperatures during the past millennium: inferences, uncertainties, and limitations', Geophysical Research Letters, 26, 759-762 Mann, M.E., Bradley, R.S. and Hughes, M.K. 2004. Corrigendum: Global-scale temperature patterns and climate forcing over the past six centuries. Nature 430, 105 http://www.nature.com/nature/journal/v430/n6995/suppinfo/nature02478.html McIntyre, S. & McKitrick, R. 2005. Hockey sticks, principal components, and spurious significance. Geophysical Research Letters 32:L03710 http://www.climate2003.com/pdfs/2004GL012750.pdf National Research Council. 2006. Surface temperature reconstructions for the past 2,000 years http://www.nap.edu/catalog/11676.html (The report can be downloaded for free, but you have to create a user account.) Stern, N. (H.M. Treasury). Oct. 30, 2006. Stern Review on the Economics of Climate Change. http://www.hm-treasury.gov.uk/independent_reviews/stern_review_economics_cli... von Storch, H., Zorita, E, Jones, J.M. et al. 2004. Reconstructing past climate from noisy data, Science 306: 679-682 http://stephenschneider.stanford.edu/Publications/PDF_Papers/vonStorchEtAl20... Wegman, E.J. et al. 2005. Ad Hoc Committee Report on the "Hockey Stick" Global Climate Reconstruction. http://energycommerce.house.gov/108/home/07142006_Wegman_Report.pdf ____________________________________________________________________________________ Want to start your own business? Learn how on Yahoo! Small Business. http://smallbusiness.yahoo.com/r-index