[asa] The Hockey Stick Holds Up

From: Rich Blinne <rich.blinne@gmail.com>
Date: Wed Sep 10 2008 - 13:45:08 EDT

From today's Nature. Climate change: 'Hockey stick' holds up

*Proc. Natl Acad. Sci. USA* *105*, 1325213257

A fresh analysis of climate indicators shows that the Northern Hemisphere is
warmer now than it has been in at least 1,300 years.

Previous analyses of climatic history by Michael Mann of Pennsylvania State
University in University Park and his colleagues produced a distinctive
'hockey stick' shape; but some of this analysis, and the tree-ring data it
used, came under attack.

The latest work by Mann and his co-workers involves various climate proxies,
including corals, ice cores, historical records and marine sediments. The
authors show that current warming is anomalous even if all tree-ring data
are eschewed.

The URL to the study is here: http://www.pnas.org/content/105/36/13252.full

Note: that when statements such as "in at least 1,300 years" are used it
ONLY means that the data is reliable through that period and not that it was
warmer 1,300 years ago. If the tree ring data is included that number goes
back 1700 years (and there is still nothing warming than the current period
as far back as the data sees). The data noted here also includes the
so-called Medieval Warm Period. The current study gives a slightly warmer
reading but it is WAY cooler than present.
The graph in the study can be found here:

EIV stands for error in variables and is the new technique that increases
the accuracy of the analysis versus CPS (composite plus scale) because it
deals with errors both in the predictor and predictand.

Rich Blinne
Member ASA

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Received on Wed, 10 Sep 2008 11:45:08 -0600

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