Medieval Warm Period Strikes Back!

Two new papers confirm MWP and knock down resurrected ‘Hockey Stick’

By —— Bio and Archives--September 13, 2008

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[Note: Craig Loehle also authored a November 2007 study published in Energy & Environment which found the Medieval Warm Period “0.3C warmer than 20th century” The study was d “A 2000-year global temperature reconstruction based on non-treering proxies.” (LINK) & (LINK) ]

Study: A mathematical analysis of the divergence problem in dendroclimatology

– By Craig Loehle, Published in Journal Climate Change, September 10, 2008 (Full paper requires subscription)

Excerpts: Abstract Tree rings provide a primary data source for reconstructing past climates, particularly over the past 1,000 years. However, divergence has been observed in twentieth century reconstructions. Divergence occurs when trees show a positive response to warming in the calibration period but a lesser or even negative response in recent decades. The mathematical implications of divergence for reconstructing climate are explored in this study. Divergence results either because of some unique environmental factor in recent decades, because trees reach an asymptotic maximum growth rate at some temperature, or because higher temperatures reduce tree growth. If trees show a nonlinear growth response, the result is to potentially truncate any historical temperatures higher than those in the calibration period, as well as to reduce the mean and range of reconstructed values compared to actual. This produces the divergence effect. This creates a cold bias in the reconstructed record and makes it impossible to make any statements about how warm recent decades are compared to historical periods. Some suggestions are made to overcome these problems. […] 

CONCLUSION: In conclusion, the nonlinear response of trees to temperature explains the divergence problem, including cases where divergence was not found. The analysis here also shows why non-tree ring proxies often show the Medieval Warm Period but treering-based reconstructions more often do not. While Fritts (1976) notes the parabolic tree growth response to temperature, recent discussions of the divergence problem have not focused on this mechanism and climate reconstructions continue to be done using a linear response model. When the divergence problem clearly indicates that the linearity assumption is questionable, it is not good practice to carry on as if linearity is an established fact.

Hockey Stick? What Hockey Stick? - How alarmist “scientists” falsely abolished the Mediaeval Warm Period

By Lord Christopher Monckton, September 12, 2008  

Excerpt: An extraordinary series of postings at http://www.climateaudit.org, the deservedly well trafficked website of the courageous and tenacious Canadian statistician Steve McIntyre, is a remarkable indictment of the corruption and cynicism that is rife among the alarmist climate scientists favored by the UN’s discredited climate panel, the IPCC. In laymen’s language, the present paper respectfully summarizes Dr. McIntyre’s account of the systematically dishonest manner in which the “hockey-stick” graph falsely showing that today’s temperatures are warmer than those that prevailed during the medieval climate optimum was fabricated in 1998/9, adopted as the poster-child of climate panic by the IPCC in its 2001 climate assessment, and then retained in its 2007 assessment report despite having been demolished in the scientific literature. It is a long tale, but well worth following. No one who reads it will ever again trust the IPCC or the “scientists” and environmental extremists who author its climate assessments. […] 

The continuing affair of the “hockey-stick” graph is a microcosm of the profound collapse of the rigor, objectivity, and honesty that were once hallmarks of the scientific community. The need to look to the State for very nearly all science funding has inflicted upon the scientific community a dull, dishonest uniformity, so that the deliberate falsification of results to support the current official orthodoxy has become commonplace, particularly where the climate question is concerned. It was bad enough that one of those behind the “hockey stick” affair should have told a fellow researcher, “We need to get rid of the medieval warm period.” It was worse that the authors of the bogus graph attempted to do just that, by ignoring, undervaluing or even suppressing proxies for northern-hemisphere temperature that did not suit the result they wanted; by falsely stating that they had used data they had in fact replaced with “estimates” of their own that gave them a less inconvenient answer; by overvaluing by many orders of magnitude the contribution of datasets that suited the result they wanted. It was worse still that the IPCC, several leading journals and numerous former co-authors of the three fabricators of the hockey stick should have continued to cling to it as though it were Gospel even though it has been justifiably and utterly discredited in the scientific literature, and should have gone through an elaborate pantomime of rewriting and publishing previously-rejected papers with the connivance of a dishonest journal editor, so that an entirely fictitious scientific support for the false graph could be falsely claimed by the IPCC in its current Fourth Assessment Report.

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