Fire and Ice

Michael Mann discovered that the thermometer measurements of recent decades diverged from the tree ring proxies for the same times, so he dropped the tree ring data from the tail end of his chart and replaced it with thermometer data.  This was to "hide the decline" showed by the tree ring data.  But what it showed was that tree rings are not good proxies for temperature.  And if not now, then not in the past.

So what happens when you leave tree rings out of the pictures. 

h/t j.pourmelle