No wonder they had to “hide the decline”. It appears that trees are a proxy for just about everything, except ancient temperatures. Rings from a particular tree are more likely to tell you whether:
- it was wetter there;
- there was more CO2 in the atmosphere;
- the local bear population decided to use it as a shithouse.
And now it appears that trees actually grow less in warmer temperatures:
They found that a 2C (3.6F) increase resulted in the average maximum height of trees shrinking by 11%, while a 2C decrease in the nation’s average temperature saw a 13% increase in the predicted maximum height of trees. (source)
So I think we can consign tree rings and the whole dodgy discipline of dendrochronology to the dustbin of climatological history.