A rather simple looking graph represents the historical distortion of the decade by Dr. Michael Mann, one of the leading authors of the the United Nations' Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report (TAR) of 2001.
The graph (Fig. 1 on the left) depicts averaged Northern Hemisphere temperatures over the last thousand years. More than that, in global climate reports particularly it's used as proof that mankind's industrial revolution has over the last hundred years started dangerously pushing up global temperatures, thus justifying restrictions on emissions of human produced greenhouse gasses. In this graph the historically documented temperature variations of the last millennium were flattened to a straight line due to statistical errors and improper calibration of the data right through to the 19 Century. Thermometer readings were not available for almost 850 of the 1,000 years.
Source:
Man M.E. et al, "Northern Hemisphere Temperatures During the Past Millennium: Inferences, Uncertainties, and Limitations", AGU GRL, v.3.1, 1999
Muller remarked that: "A phoney hockey stick is more dangerous than a broken one -- if we know it is broken. It is our responsibility as scientists to look at the data in an unbiased way, and draw whatever conclusions follow. When we discover a mistake, we admit it, learn from it, and perhaps discover once again the value of caution."
The IPCC "hockey stick curve" was originally produced in 1998 for the period 1400-1980 and then, with no major progress in the science or database, was quickly expanded to the full 1000-1980 interval in 1999. The paper surely managed at the time, that alarm bells began to ring in the brains of many people, and can claim the dubious reputation to have made KYOTO possible and to have a major impact on global politics. Mann's comments were at the time: "The 1990s are likely to have been the warmest decade of the millennium, and 1998 is likely to have been the warmest year." That was exactly what the global warming fanatics wanted to hear.
A more recent research paper published in the journal Science by Professor Hans von Storch and colleagues identifies these significant problems with the "hockey stick curve". Von Storch, the leader of the research team at the Institute of Coastal Research at Geesthacht, Germany, calls the hockey stick "junk" or "rubbish."
In short, the new paper in Science by Von Storch and colleagues confirms what several other climate researchers have long stipulated. The hockey stick curve -- which is a mathematical construct, as opposed to actual temperature information recorded at individual locations -- is problematic because it yields air temperature changes on timescales of a few decades to a century that are simply too muted to fit the phenomena of the Medieval Warm Period (ca. 800-1300) and Little Ice Age (ca. 1300-1900), which are well recorded in historical documents and recognised in indirect climate data from growths of tree-rings and corals or isotopic content in ice cores and stalagmites collected around the world.
This is traditional science, with results from one group tested by others. What makes this case important, though, was explained by Von Storch in the German magazine "Der Spiegel":
Therefore Mann et al. used tree-growth rings, coral and ice core records from about 105 sites across the globe. To verify the accuracy of the temperature data derived from those proxies, the methodology of the studies tested more recent proxy data to see if it fit the available geographical patterns of temperature observed by available thermometer measurements for the last 80-150 years or so. Those proxies that did not fit the pattern were essentially ignored. For those that did, it was assumed that the same geographical pattern of change seen in the very short period with thermometer records would hold true for the full 1,000 years into the past. In order to demonstrate the consequences of the"statistical errors" involved, the true historical temperature trend development is shown above (Fig.2 below the artefact).
Mann's claims have been convincingly refuted, both by historical traditional data (Climate History of Central Europe: http://www.hgg-ev.de/klimageschichte-mitteleuropa.html) as well as scientific studies of Soon, W. and Baliunas, S. 2003rd Proxy climatic and environmental changes of the past 1000 years. Climate Research 23: 89-110. http://www.co2science.org/. In a popular article in MIT's Technology Review, Professor Richard Muller, through the careful re-assessment and checking by the two independent Canadian researchers, Stephen McIntyre and Ross McKitrick, highlighted another very serious methodological problem in the IPCC rendition of the 1,000-year hockey stick temperature history -- adopting the hockey stick methodology, the hockey stick shape of the temperature history curve can be automatically generated by using random data series (i.e., in contrast to data series from actual climate proxies or computer model outputs) from each locations.
"The Mann graph [i.e., the hockey stick of IPCC TAR] indicates that it was never warmer during the last ten thousand years than it is today. ... In recent years it [the hockey stick] has been elevated to the status of truth by the UN appointed science body, the Intergovernmental Panel on Climate Change (IPCC). This handicapped all that research which strives to make a realistic distinction between human influences and natural variability of the climate."
Catastrophe Denied - A Critique of Catastrophic AGW Theory
Presentation by Warren Meyer of Climate-Skeptic.com reporting on the science of the skeptic's position. Lecture given on November 10, 2009 in Phoenix, Arizona.
The very cold god of physics is there with the red pen to make sure we all get it right in the end ...
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