On Thu, 7 Feb 2013 13:40:52 -0800 (PST), "
erschro...@gmail.com"
<
erschro...@gmail.com> wrote:
> On Feb 7, 3:49�pm, Paul Aubrin <
chu8i...@free.fr> wrote:
> > On Thu, 07 Feb 2013 01:06:27 -0600, josephus wrote:
> > >> Your permanent use of abusive statement gives a very negative image of
> > >> you. Why can't you reply correctly, you know that abuse is the last
> > >> resort of a looser in a debate.
> > > quoting �mathematics with out numbers is �in this case �stupid. �there
> > > no context for the �math. �the assertions are UNSUPPORTED
> > MBH98 is based on an inappropriate use of the Principal Component
> > statistical analysis. This has been verified by the American Statistical
The ASA said the opposite:
http://www.amstat-online.org/sections/envr/ssenews/ENVR_9_1.pdf
> "The test in science is whether findings can be replicated using
> different data and methods. More than two dozen scientific papers,
> using various statistical methods and combinations of proxy records,
> have produced reconstructions supporting the broad consensus shown in
> the original 1998 hockey-stick graph, with variations in how flat the
> pre-20th century "shaft" appears. The 2007 IPCC Fourth Assessment
> Report cited 14 reconstructions, 10 of which covered 1,000 years or
> longer, to support its strengthened conclusion that it was likely that
> Northern Hemisphere temperatures during the 20th century were the
> highest in at least the past 1,300 years. Ten or more subsequent
> reconstructions, including Mann et al. 2008, have supported these
> general conclusions."
Yes; there are now over 19 independent reconstructions (that I am
aware of), using independent data, and they all show a "hockey stick."
> "At the end of April Science published a reconstruction by J.
> Oerlemans based on glacier length records from different parts of the
> world, and found consistent independent evidence for the period from
> 1600 to 1990 supporting other reconstructions regarding magnitude and
> timing of global warming.[154] In May the University Corporation for
> Atmospheric Research advised media about a detailed analysis by Eugene
> Wahl and Caspar Ammann, first presented at the American Geophysical
> Union�s December 2004 meeting in San Francisco, which used their own
> code to replicate the MBH results, and found the MBH method to be
> robust even with modifications. Their work contradicted the claims by
> McIntyre and McKitrick about high 15th century global temperatures and
> allegations of methodological bias towards a hockey stick outcomes,
> and they concluded that the criticisms of the hockey stick graph were
> groundless"
>
> "Various criticisms of the MBH statistical methods were discussed in
> the context of more recent research which explored ways of addressing
> these problems, and showed greater amplitude of temperature variations
> over 1000 to 2000 years. Recent papers cited included Wahl & Ammann
> 2006 (in press). On McIntyre and McKitrick's criticism of principal
> component analysis as tending to bias the shape of the
> reconstructions, it found that "In practice, this method, though not
> recommended, does not appear to unduly influence reconstructions of
> hemispheric mean temperature", and reconstructions using other methods
> were qualitatively similar. Some of the criticisms of validation
> techniques were more valid than others, these issues and the effect on
> robustness of the choice of proxies contributed to the committee's
> view of increased uncertainties. They called for further research into
> methods and a search for more proxies for earlier periods.
>
> At the press conference the three NRC panellists said they found no
> evidence supporting the allegations of inappropriate behaviour such as
> data manipulation, or "anything other than an honest attempt to
> construct a data analysis procedure". Bloomfield as a statistician
> considered all the choices of data processing and methods to have been
> "quite reasonable" in a "first of its kind study". He said "I would
> not have been embarrassed by that work at the time if I'd been
> involved in it". In response to a question from Edward Wegman on the
> MBH use of principal components analysis, Bloomfield said this had
> been reviewed by the committee along with other statistical issues,
> and "while the issues are real, they had a very minimal effect, not a
> material effect on the final reconstruction."