[LMB] Effects of "Global Warming"

Greg Hennessy greg.hennessy at cox.net
Tue Sep 13 01:08:17 BST 2011


 > At this time, the "hockey stick graph" is pretty much discredited
 > due to cherry picking the data sources. It removed Roman warm
 > period, the mediaeval warm period, and the little ice age. The
 > dramatic increase it showed came from eliminating most of the
 > sources used for earlier periods.

No. the hocket stick graph is only discredited among science skeptics
and deniers.  Among scientists, it is not. The claim that Mann removed
the Roman Warm period is simply not credible, since the 1998 and 1998
papers by Mann didn't go back that far. While the statistics may not
have been done exactly correctly in his early papers, the basic result
is sound.

http://www.cgd.ucar.edu/ccr/ammann/millennium/refs/Wahl_ClimChange2007.pdf

The National Academy of Sciences said in their report on Mann:

"The basic conclusion of Mann et al. (1998, 1999) was that the late
20th century warmth in the Northern Hemisphere was unprecedented
during at least the last 1,000 years. This conclusion has subsequently
been supported by an array of evidence that includes both additional
large-scale surface temperature reconstructions and pronounced changes
in a variety of local proxy indicators, such as melting on ice caps
and the retreat of glaciers around the world, which in many cases
appear to be unprecedented during at least the last 2,000 years. Not
all individual proxy records indicate that the recent warmth is
unprecedented, although a larger fraction of geographically diverse
sites experienced exceptional warmth during the late 20th century than
during any other extended period from A.D. 900 onward."



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