The latter part of Briffa’s trees was deleted, because it didn’t match GISS temperatures.
As ugly as this was, it is worse than it seems. Briffa’s trees did match Hansen, 1981. The next graph overlays Briffa on Hansen, 1981 northern latitude temperatures. The match was almost perfect.
In order to create the hockey stick cheat, they had to do the GISS data tampering cheat first. The entire basis of the hockey stick is junk science.
The destruction of this data was done in a calculated fashion, by the world’s top climate scientists.
They did exactly what Wigley was suggesting, removing more than 0.15 C from 1940’s global temperatures. This tampering is what made the hockey stick possible. Graph below is normalized to 1978.
Another way of looking at this data is to normalize it to 1940. In this view you can see that they wiped out the post 1940’s cooling, and turned it into warming.
* Disclaimer : Mosher says that GISS temperatures are first rate science.