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Michael E. Mann

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Michael Mann

Michael Mann is a well-known climatologist, author of more than 80 peer-reviewed journal publications. He has attained public prominence as lead author of a number of articles on paleoclimate which feature a graph of temperature trends dubbed the "hockey stick graph" for the shape of the trend line. In August 2005 he was appointed Associate Professor at Pennsylvania State University, in the Department of Meteorology and Earth and Environmental Systems Institute, and Director of the university's interdepartmental Earth System Science Center. He previously taught at the University of Virginia, in the Department of Environmental Sciences (1999 - 2005).

Career

He was a Lead Author on the “Observed Climate Variability and Change” chapter of the Intergovernmental Panel on Climate Change (IPCC) Third Scientific Assessment Report (2001). He has been organizing committee chair for the National Academy of Sciences ‘Frontiers of Science’ and has served as a committee member or advisor for other National Academy of Sciences panels. He served as editor for the Journal of Climate and has been a member of numerous international and U.S. scientific advisory panels and steering groups. Dr. Mann has been the recipient of several fellowships and prizes, including selection as one of the 50 leading visionaries in Science and Technology by Scientific American, the outstanding scientific publication award of the National Oceanic and Atmospheric Administration (NOAA), and recognition by the Institute for Scientific Information (ISI) for notable citation of his refereed scientific research.

He is best known for his paleoclimate 'hockey stick' reconstructions of the past several millennia from tree ring, ice core, coral and other data. See temperature record of the past 1000 years for more details and dispute. Mann's recent work has been on modelling El Niño, and he has warned that "we are already committed to 50 to 100 years of global warming and several centuries of sea level rise" and that reduction in fossil fuel emissions is required to slow the process down to a level that can be coped with.

Hockey stick

Reconstructions of the temperature history of the last 1000 years. The MBH '99 version is in blue

Scientific American magazine described him as the "Man behind the Hockey Stick", referring to his reconstruction of temperatures, originally published in 1998. He has been personally involved in the debate over climate change. In testimony before the US Senate in 2003, he stated:

It is the consensus of the climate research community that the anomalous warmth of the late 20th century cannot be explained by natural factors, but instead indicates significant anthropogenic, that is human influences... More than a dozen independent research groups have now reconstructed the average temperature of the northern hemisphere in past centuries... The proxy reconstructions, taking into account these uncertainties, indicate that the warming of the northern hemisphere during the late 20th century... is unprecedented over at least the past millennium and it now appears based on peer-reviewed research, probably the past two millennia.

The battle over his work has been unusually personal, with Senator James Inhofe (R-OK) saying his work was "a hoax", while Mann has replied that the attacks were "intellectually pathetic" and "deceptive". More recently, Representative Joe Barton (R-TX-06) has requested information from Mann and co-authors about his work ; this has been widely seen as "a search for some basis on which to discredit these particular scientists and findings, rather than a search for understanding" . It was later discovered that the whole controversy was based upon the research of Stephen McIntyre. McIntyre claims that many statistical methods used to generate Mann's hockey stick were applied incorrectly and that Mann used data known to be faulty. McIntyre created his own plot of past temperatures which shows a smaller temperature rise in the 20th century than in the 14th century.

More recently, the National Research Council considered the matter. On June 22, 2006, the Council released a pre-publication version of its report Report-Surface Temperature Reconstructions for the Last 2,000 Years. This publication reported mixed results.

RealClimate has posted that the panel has found reason to support the key mainstream findings of past research, including points that we have highlighted previously. According to Roger A. Pielke (Jr) this produced a near-complete vindication for the work of Mann et al. ; Nature reported it as Academy affirms hockey-stick graph .

According to Von Storch, Zorita and Gonzalez-Rouco, "With respect to methods, the (National Research Council’s Report-Surface Temperature Reconstructions for the Last 2,000 Years (2006)) is showing reservations concerning the methodology of Mann et al. The committee notes explicitly on pages 91 and 111 that the method has no validation (CE) skill significantly different from zero. In the past, however, it has always been claimed that the method has a significant nonzero validation skill. Methods without a validation skill are usually considered useless." .

However, CE is not the only measure of skill; Mann et al (1998) used the more traditional "RE" score, which, unlike CE, accounts for the fact that time series change their mean value over time. The statistically significant reconstruction skill in the Mann et al. reconstruction is independently supported in the peer-reviewed literature by Huybers (2005) and Wahl and Ammann (2006) .

New hearing have been held by the U.S. House of Representatives Subcommittee on Oversight and Investigations (July 19, 2006) to examine Mann's "Hockey Stick" analysis and conclusions . The Wegman report (July 19, 2006) by statistical experts done for the Committee on Energy and Commerce of the U.S. Congress largely repeats the criticisms of M&M according to Mann (although by a different group of statistical experts); Mann has also said that the report uncritically parrots claims by two Canadians (an economist and an oil industry consultant) that have already been refuted by several papers in the peer-reviewed literature inexplicably neglected by Barton’s “panel”. These claims were specifically dismissed by the National Academy in their report just weeks ago . However, the Wegman report points out that peer review in the paleoclimatology community may not be completely trustworthy:

In our further exploration of the social network of authorships in temperature reconstruction, we found that at least 43 authors have direct ties to Dr. Mann by virtue of coauthored papers with him. Our findings from this analysis suggest that authors in the area of paleoclimate studies are closely connected and thus ‘independent studies’ may not be as independent as they might appear on the surface.

Selected publications

  • Mann, M.E., Cane, M.A., Zebiak, S.E., Clement, A., Volcanic and Solar Forcing of the Tropical Pacific Over the Past 1000 Years, Journal of Climate, 18, 447-456, 2005.
  • Schmidt, G.A., Shindell, D.T., Miller, R.L., Mann, M.E., Rind, D., General Circulation Modeling of Holocene climate variability, Quaternary Science Reviews, 23, 2167-2181, 2004.
  • Andronova, N.G., Schlesinger, M.E., Mann, M.E., Are Reconstructed Pre-Instrumental Hemispheric Temperatures Consistent With Instrumental Hemispheric Temperatures?, Geophysical Research Letters, 31, L12202, doi: 10.1029/2004GL019658, 2004.
  • Jones, P.D., Mann, M.E., Climate Over Past Millennia, Reviews of Geophysics, 42, RG2002, doi: 10.1029/2003RG000143, 2004.
  • Mann, M.E., On Smoothing Potentially Non-Stationary Climate Time Series, Geophysical Research Letters, 31, L07214, doi: 10.1029/2004GL019569, 2004.
  • Shindell, D.T., Schmidt, G.A., Mann, M.E., Faluvegi, G., Dynamic winter climate response to large tropical volcanic eruptions since 1600, Journal of Geophysical Research, 109, D05104, doi: 10.1029/2003JD004151, 2004.
  • Mann, M.E., Jones, P.D., Global surface temperature over the past two millennia, Geophysical Research Letters, 30 (15), 1820, doi: 10.1029/2003GL017814, 2003.
  • 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.
  • Mann, M.E., Schmidt, G.A., Ground vs. Surface Air Temperature Trends: Implications for Borehole Surface Temperature Reconstructions,Geophysical Research Letters, 30 (12), 1607, doi: 10.1029/2003GL017170, 2003.
  • Mann, M.E., Rutherford, S., Bradley, R.S., Hughes, M.K., Keimig, F.T., Optimal Surface Temperature Reconstructions using Terrestrial Borehole Data, Journal of Geophysical Research, 108 (D7), 4203, doi: 10.1029/2002JD002532, 2003.
  • Rutherford, S., Mann, M.E., Delworth, T.L., Stouffer, R., Climate Field Reconstruction Under Stationary and Nonstationary Forcing, Journal of Climate, 16, 462-479, 2003.
  • Mann, M.E. , The Value of Multiple Proxies, Science, 297, 1481-1482, 2002.
  • Mann, M.E., Rutherford, S., Climate Reconstruction Using 'Pseudoproxies', Geophysical Research Letters, 29 (10), 1501, doi: 10.1029/2001GL014554, 2002.
  • Mann, M.E., Hughes, M.K., Tree-Ring Chronologies and Climate Variability, Science, 296, 848, 2002.
  • Mann, M.E., Bradley, R.S., Briffa, K.R., Cole, J., Hughes, M.K., Jones, J.M., Overpeck, J.T., von Storch, H., Wanner, H., Weber, S.L., Widmann, M., Reconstructing the Climate of the Late Holocene, Eos, 82, 553, 2001.
  • Bradley, R.S., Briffa, K.R., Crowley, T.J., Hughes, M.K., Jones, P.D., Mann, M.E.,Mann, M.E. Medieval Climatic Optimum, Encyclopedia of Global Environmental Change,John Wiley and Sons Ltd, London, UK, pp. 514-516, 2001.
  • Mann, M.E. "Little Ice Age", Encylopedia of Global Environmental Change, John Wiley and Sons Ltd, London, UK, pp. 504-509, 2001.
  • Shindell, D.T., Schmidt, G.A., Mann, M.E., Rind, D., Waple, A., Solar forcing of regional climate change during the Maunder Minimum, Science, 7, 2149-2152, 2001.
  • Bradley, R.S., Briffa, K.R., Crowley, T.J., Hughes, M.K., Jones, P.D., Mann, M.E., Scope of Medieval Warming, Science, 292, 2011-2012, 2001.
  • Folland, C.K., Karl, T.R., Christy, J.R., Clarke, R. A., Gruza, G.V., Jouzel, J., Mann, M.E., Oerlemans, J., Salinger, M.J., Wang, S.-W., Observed Climate Variability and Change, in 2001 Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds), Cambridge Univ. Press, Cambridge, 99-181, 2001.

External links

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