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Controversy Surrounding the ‘Hockey Stick

Controversy Surrounding the ‘Hockey Stick. Elizabeth Fitzgerald June 2, 2006. Most criticisms to climate change focus on Mann et al.’s ‘Hockey Stick’ diagram Critique climate reconstruction Smooth ‘shaft’ Skeptics’ arguments often based on misinterpretations, misuse of data

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Controversy Surrounding the ‘Hockey Stick

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  1. Controversy Surrounding the ‘Hockey Stick Elizabeth Fitzgerald June 2, 2006

  2. Most criticisms to climate change focus on Mann et al.’s ‘Hockey Stick’ diagram • Critique climate reconstruction • Smooth ‘shaft’ • Skeptics’ arguments often based on misinterpretations, misuse of data • Many other models/reconstructions have validated the late 20th century warmth • 20th century data based largely on instrumental measurements

  3. Large Uncertainties Since Mann et al.’s original paper in 1998, numerous other reconstructions and models have reached the same conclusion

  4. The 20th Century is the Warmest on Record • (dark blue 1000-1991): P.D. Jones, K.R. Briffa, T.P. Barnett, and S.F.B. Tett (1998). The Holocene 8: 455-471. • (blue 1000-1980): M.E. Mann, R.S. Bradley, and M.K. Hughes (1999). Geophysical Research Letters 26 (6): 759-762. • (light blue 1000-1965): Crowley and Lowery (2000). "Northern Hemisphere Temperature Reconstruction". Ambio 29: 51-54. Modified as published in Crowley (2000). Science 289: 270-277. • (lightest blue 1402-1960): K.R. Briffa, T.J. Osborn, F.H. Schweingruber, I.C. Harris, P.D. Jones, S.G. Shiyatov, S.G. and E.A. Vaganov (2001). J. Geophys. Res. 106: 2929-2941. • (light green 831-1992): J. Esper, E.R. Cook, and F.H. Schweingruber (2002). Science 295 (5563): 2250-2253. • (yellow 200-1980): M.E. Mann and P.D. Jones (2003). Geophysical Research Letters 30 (15): 1820. • (orange 200-1995): P.D. Jones and M.E. Mann (2004). Reviews of Geophysics 42: RG2002. • (red-orange 1500-1980): S. Huang (2004). Geophys. Res Lett. 31: L13205. • (red 1-1979): A. Moberg, D.M. Sonechkin, K. Holmgren, N.M. Datsenko and W. Karlén (2005). Nature 443: 613-617. • (dark red 1600-1990): J.H. Oerlemans (2005). Science 308: 675-677. The last few decades of the 20th century show the most warmth and warming of any comparable-length period

  5. Warmth vs. Warming 20th century warming is unprecedented http://en.wikipedia.org/wiki/Image:1000_Year_Temperature_Comparison.png

  6. Hockey Stick Does Not Reproduce Known Climate Variations Only uses annual records (Tree Ring and Ice Cores) manipulated using "Climate Field Reconstruction"--Mann et al., 1999 Uses annual and longer records (sediment and others) and better statistics--Moberg et al., 2005

  7. Statistics • Lack of consistent proxy record requires infilling • Different treatments of proxies may yield different results • Results are the same if done correctly

  8. Statistics Continued Von Storch et al., 2004 McIntyre and McKitrick, 2005

  9. What to Tell the Guy Next to You on the Airplane • Climate change is a consequence of the laws of physics • CO2 absorbs IR radiation • Humans are increasing [CO2] • Instrumental data show warmer temperatures in the late 20th century • Essentially all models agree on anomalous 20th century warming • Past warmth does not disprove anthropogenic climate change

  10. What are we up against? • Who Pays the Climate Skeptics

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