Hockey sticks, principal components, and spurious significance

McIntyre, Stephen; McKitrick, Ross

doi:10.1029/2004gl021750

Cited by 91 publications

(126 citation statements)

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“…Nevertheless, quantitative agreement has been so far elusive and thus a matter of considerable debate in the last few years (e.g. von Mann et al, 2005;Bürger and Cubasch, 2005;Bürger et al, 2006;Moberg et al, 2005;McIntyre and McKitrick, 2005;Wahl et al, 2006;Mann et al, 2007aMann et al, ,b, 2008Smerdon and Kaplan, 2007;Wahl and Ammann, 2007;Ammann and Wahl, 2007;Lee et al, 2008) …”

Section: Paleoclimate Contextmentioning

confidence: 99%

Borehole climatology: a discussion based on contributions from climate modeling

et al. 2009

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Abstract. Progress in understanding climate variability through the last millennium leans on simulation and reconstruction efforts. Exercises blending both approaches present a great potential for answering questions relevant both for the simulation and reconstruction of past climate, and depend on the specific peculiarities of proxies and methods involved in climate reconstructions, as well as on the realism and limitations of model simulations. This paper explores research specifically related to paleoclimate modeling and borehole climatology as a branch of climate reconstruction that has contributed significantly to our knowledge of the low frequency climate evolution during the last five centuries.The text flows around three main issues that group most of the interaction between model and geothermal efforts: the use of models as a validation tool for borehole climate reconstructions; comparison of geothermal information and model simulations as a means of either model validation or inference about past climate; and implications of the degree of realism on simulating subsurface climate on estimations of future climate change.The use of multi-centennial simulations as a surrogate reality for past climate suggests that within the simplified reality of climate models, methods and assumptions in borehole reconstructions deliver a consistent picture of past climate evolution at long time scales. Comparison of model simulations and borehole profiles indicate that borehole temperatures are responding to past external forcing and that more realism in the development of the soil model components in climate models is desirable. Such an improved degree of Correspondence to: J. F. González-Rouco (fidelgr@fis.ucm.es) realism is important for the simulation of subsurface climate and air-ground interaction; results indicate it could also be crucial for simulating the adequate energy balance within climate change scenario experiments.

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Section: Paleoclimate Contextmentioning

confidence: 99%

Borehole climatology: a discussion based on contributions from climate modeling

et al. 2009

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“…Huybers (2005), commenting on McIntyre and McKitrick (2005a), points out that normalization also affects results, a point that is reinforced by McIntyre and McKitrick (2005b) in their response to Huybers. Principal component calculations are often carried out on a correlation matrix obtained by normalizing each variable by its sample standard deviation.…”

Section: Mcintyre and Mckitrickmentioning

confidence: 99%

Surface Temperature Reconstructions for the Last 2,000 Years

North¹

2006

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Our understanding of climate and how it has varied over time is advancing rapidly as new data are acquired and new investigative instruments and methods are employed. Thus in 2005, I suggested to the U.S. Congress that the National Research Council (NRC) could help answer questions about the data and methods that have been used in constructing records of Earth's surface temperatures from times when there were no scientific instruments, using proxy indicators. How has temperature varied over the last 2,000 years? How certain is the answer to this question? Subsequently, this study was requested by Representative Sherwood Boehlert, chairman of the Committee on Science, U.S. House of Representatives. Chairman Boehlert asked for a clear and concise report in a relatively short period of time, and the NRC agreed to undertake the study quickly. An ad hoc committee was formed, with the group carefully composed to include the breadth and depth of expertise and perspectives needed to analyze all aspects of how surface temperatures are estimated and interpreted and to comment generally on climate science. The NRC asked the committee to summarize current scientific information on the temperature record for the past two millennia, describe the main areas of uncertainty and how significant they are, describe the principal methodologies used and any problems with these approaches, and explain how central is the debate over the paleoclimate temperature record to the state of scientific knowledge on global climate change.The committee has prepared a report that, in my view, provides policy makers and the scientific community with a critical view of surface temperature reconstructions and how they are evolving over time, as well as a good sense of how important our understanding of the paleoclimate temperature record is within the overall state of scientific knowledge on global climate change. The report does not make policy recommendations.I thank the members of the committee, who worked intensely to produce this careful report in a short period of time and contributed much personal time, insight, and energy. ForewordCopyright © National Academy of Sciences. All rights reserved.Surface Temperature Reconstructions for the Last 2,000 Years http://www.nap.edu/catalog/11676.htmlThe NRC staff and all those who contributed papers, data, graphics, and other information, as well as the independent experts who participated in the rigorous review process, were essential participants. Surface Temperature Reconstructions for the Last 2,000 Years http://www.nap.edu/catalog/11676.html ix This committee was 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 full Statement of Task appears in Appendix A.) Normally, a technical issue such as surface temperature reconstructions might not generate widespread attention, but this case brings interesting lessons about how science works and how science, especially climate science, is commun...

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“…They reached this conclusion by using an incorrect version of the proxy data set used in MBH98 (Rutherford et al 2005(Rutherford et al , p. 2312. In a subsequent article, they argued that the hockey stick is an artifact of the statistical conventions chosen in MBH98 (McIntyre and McKitrick 2005). Their argument in this paper targeted MBH's use of principle component analysis (PCA), which is a statistical procedure that can be used to represent large data sets in terms of a smaller number of patterns.…”

Section: The Attacks On Mann Bradley and Hughesmentioning

confidence: 99%

“…MBH used this procedure to deal with the problem of diverse proxy data, which included large sets of tree ring data and smaller sets of data from other sources (MBH98; Mann 2012). McIntyre and McKitrick (2005) argued that the hockey stick pattern is an artifact of the choice of a convention for centering tree ring data; more specifically, they argued that if one centers tree ring data at the twentieth 2 http://www.grida.no/publications/other/ipcc_tar/?src=/climate/ipcc_tar/wg1/005.htm. Accessed 19 April 2014. century, the hockey stick pattern appears, but that if one centers it around a long term average (from 1400-1980), then the pattern does not appear.…”

Section: The Attacks On Mann Bradley and Hughesmentioning

confidence: 99%