Tuesday, December 27, 2011

For Michael Mann, oh, what a tangled web: In a 2003 ClimateGate email, he claims that "the proxy reconstructions show the post-1980 warming"

2003 ClimateGate email

2) We haven't in the past extended the proxy reconstruction beyond 1980 because many of the proxy data drop out. However, the repeated claim by the contrarians that post-1980 proxy data don't show the warming evident in the instrumental record has finally prompted me to go ahead and perform an additional analysis in which the proxy-reconstruction is extended forward as recently as at all possible (to 1995, for which 3 out of 8 of the NH records are available, and 1 of the 5 SH records are available). The SH and GLB reconstructions are thus obviously tenuous at best, but they do address, to the extent at all possible, the issue as to whether or not the proxy reconstructions show the post-1980 warming--and they do.  [Michael Mann]

Archived-Articles: Understanding Climategate's Hidden Decline

[2009]And I hope that those investigating the fraud will carefully consider this explanation of the WMO cheating given last week by Jones:
One of the three temperature reconstructions was based entirely on a particular set of tree-ring data that shows a strong correlation with temperature from the 19th century through to the mid-20th century, but does not show a realistic trend of temperature after 1960. This is well known and is called the ‘decline’ or ‘divergence’. The use of the term ‘hiding the decline’ was in an email written in haste. CRU has not sought to hide the decline. Indeed, CRU has published a number of articles that both illustrate, and discuss the implications of, this recent tree-ring decline, including the article that is listed in the legend of the WMO Statement figure. It is because of this trend in these tree-ring data that we know does not represent temperature change that I only show this series up to 1960 in the WMO Statement. [My emphasis.]

Hide-the-Decline Plus « Climate Audit

At the time, no one knew about “hide the decline”. Mann et al do not mention anything about deleting adverse data. The Briffa reconstruction labeled in the legend as “Briffa et al scaled 1856-1980″, giving no clue to readers of hide-the-decline. Let’s now look at a magnified version of this graphic, blown up so that we can see how they handled the Briffa (orange) reconstruction. As sharp-eyed CA readers FergalR and haroldw observed, if you squint closely, you can see that the Briffa reconstruction was chopped off before its end.

Indeed, they did not simply “hide the decline”, their “hide the decline” was worse than we thought. Mann et al did not merely delete data after 1960, they deleted data from 1940 on, You can see the last point of the Briffa reconstruction (located at ~1940) peeking from behind the spaghetti in the graphic below

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