In any case, the graph has no objective basis whatsoever; it is purely a "visual guess" at what
happened, like something we might sketch on a napkin at a party for some overly persistent
inquisitor.....[Ray Bradley] I believe this graph originated in a (literally) grey piece of literature that Jack Eddy used to publish called "Earth Quest".
[tom crowley] we still don't have an adequat explanation as to how Jack "cooked up" that figure
I think that this story could possible catch on and make headlines, so I
agree that we should be careful... There are sometimes a few rotten apples in a good batch,
unfortunately. But the important part is that we don't accept rotten
apples and that we sort it out! Forthcoming and up-front.
I also see your problem: what we are finding out now makes the IPCC
process look somewhat unsophisticated back in 1990, so it is a
diplomatic conundrum how to be completely truthful in reporting this, as
we need to be as scientists, without providing the skeptics undue fodder
for attacking IPCC.
So I think that we have a solution to the provenance of IPCC 1990 Figure 7c. It is derived from the rounded CET from Lamb 1965 Figure 3 top panel, with portion after 1400 smoothed somewhat. It has been converted to anomaly deg C (using the average of the entire period) and extended to include the average CET for the period 1950-1984.