Of course the temperature information would vary by elevation.
The Russians didn't mix the data but Mann did.
What you have is a picture of Mann with tree rings ~ the implication is that those particular tree rings tell the story ~ which, no doubt, they do ~ but the reality is different than the story.
The reality is he was prepared to PROVE HIS CASE with his tree rings. On the other hand, the tree rings didn't all come from the same place, nor did they cover the same periods of time, nor were they representative of the same sampling universe.
It is noteworthy that the local climate along the Lena river in Yakutia has been such that about 1850 ALL THE TREES in the highlands were killed and blown into the valleys. In fact, the weather was so bad for the next 159 years in the highlands that trees have not yet been able to re-establish themselves.
The trees in the valley survived the climate. However, I suspect even they show a decline in local temperatures from 1850 to the date of sampling in 1998 ~ which would require Mann to "cheat" once again by cherry picking the older upland samples as well as the newer valley samples.
BTW, subsequent to the earlier work along the Lena the researchers in Russia were able to extend the period of samples back 2000 years.
In the 70’s and 80’s I was a (minor) player in a scientific endeavor that went against the prevailing thought at the time. In this case we were EAGER to provide data, ALL the data, to the skeptics. We welcomed debate with the skeptics, since we knew that we could convince open minded people with the facts that we had. This attitude is totally lacking in the CRU/GISS/Mann community. It is truly Mann made goobal warming.