There is only one goddess Gaia and Al Gore is her only prophet...

[kandrathe]

That indeed seems a weird thing to do. I am no expert in tree rings, but it doesn't sound very scientific to me.

Careful... lest you get the label of "Denier" by doubting the veracity of Dendrochronology. I believe you can determine which were good years for trees, but there are many factors other than temperature which would influence that. Tree rings can give insight into the micro climate around that tree, and in aggregate you can capture data going back hundreds, or in some places thousands of years. It is made stronger when it is accurately linked to ice core data, lake sediments, and some other naturally occurring processes. It's weakness however is that there are only a few places where tree ring data extends beyond a few hundred years, and most places where no data exists at all.