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'We have to get rid of the Medieval Warm Period'

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  • 'We have to get rid of the Medieval Warm Period'

    From somewhere in my 8 decades of memory, I recall accounts of a climate phenomenon termed 'the Medieval Warm Period (MWP)'. However, since I have taken an interest in the AGW/Climate Change controversy, I repeatedly see AGW arguments that evidences of the MWP are limited to local phenomena, and/or that whatever warming there may have been during the MWP was less than the warming that has occurred during the 20th century.

    Now I read in A. W. Montford's The Hockey Stick Illusion: Climategate and the Corruption of Science ― a voluminous, well documented, history consisting of 496 pages of smallish print ― (Stacy International: London, 2010) an account of the First Assessment Report (FAR), in which the IPCC commented:
    We conclude that despite great limitations in the quantity and quality of the available historical temperature data, the evidence points consistently to a real but irregular warming over the last century. A global warming of larger size has almost certainly occurred at least once since the end of the last glaciation without any appreciable increase in greenhouse gases. Because we do not understand the reason for these warming events, it is not yet possible to attribute a specific proportion of the recent, smaller [emphasis added] warming to an increase of greenhouse gases.*
    *Houghton J., Jenkins G., Ephraums J. Climate change: The IPCC scientific assessment (Contributions of Working Group I to the first assessment report the Intergovernmental Panel on Climate Change). Cambridge: Cambridge University Press; 1990.

    Montford presents on page 23 (op. cit.) a graph/figure published by the IPCC showing the Medieval Warm Period lasting from the eleventh to the fifteenth centuries, with the section of the graph representing the MWP being several times higher (i.e., warmer) than the modern warm period. The caption below the graph is: Figure 1.1: The Medieval Warm Period as shown in the IPCC First Assessment Report in 1990.

    Montford reports the work of two tree-ring researchers, Malcolm Hughes and Henry Diaz, who co-authored a journal review from which, if right, it would be possible to conclude that the MWP was, at most, a series of regional warnings. Hughes and Diaz concluded that 'temperatures had been higher in some parts of the world ― they singled out Scandinavia, China, the Sierra Nevada in California, the Canadian Rockies and Tasmania.' .... 'Still, this single review did not overturn the well-established MWP paradigm'.

    Then came 'The Deming Affair'. David Deming was a geoscientist from the University of Oklahoma, whose expertise was in boreholes, from which is was possible to extract a profile of the temperatures within the rocks on the way down. Deming's work seemed to provide evidence compatible with AGW theory, so he was able to get an article published in Science, after which he published an article in which he wrote:
    With the publication of the article in Science, I gained significant credibility in the community of scientists working on climate change. They thought I was one of them, someone who would pervert science in the service of social and political causes. So one of them let his guard down. A major person working in the area of climate change and global warming sent me an astonishing email that said 'We have to get rid of the Medieval Warm Period.'

    Montford comments on historical facts related to that quote and then concludes that 'the aim was to erase [the MWP] from the climatological record in its entirety. Although Deming himself did not identify the email's author, Richard Lindzen of MIT has confirmed internet rumors that the email was written by Jonathan Overpeck of the university of Arizona.' Montford provided documentation via an email link that is now, four years after publication of his book, no longer available.

    Montford says that a major problem with the case for the MWP having been an insignificant regional phenomenon was the paucity of hard data to support the case. Critics could rightly say that conclusions drawn from the available data were speculative at best. 'Climate science wanted big funding and big political action and that was going to require definitive evidence. In order to strengthen the arguments for the recent warming being unprecedented, there was going to have to be a major study, presenting unimpeachable evidence that the Medieval Warm Period was a chimera.'

    Enter the Hockey Stick.

    We will see more on that as the Mann vs. Steyn et al. threads follow the litigation in the three court cases.
    Last edited by John Reece; 08-20-2014, 09:57 PM.

  • #2
    Reminds me...

    This OP reminds me of this OP.

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