tree ring data is interesting. there are natural cycles and superimposed with nonlinear feedbacks man made ones too. any data that helps understand either will increase understanding of the other.

Mike---- is my memory correct on the below:

it's been 30+ years but i think i read that in the earth's axis is not the same now as in roman times due to axis wobble like a top's. so comparing tree ring data would have to account for the base climate of he region.

I'd guess that the nature article accounts for this effect. [concerning nature, i have heard some reports from friends who went thru their reviewing process recently. it's definitely an outlet that gets highly cited but it also seems to look for trendy papers rather then good ones- according to their sour grapes.]

data is important, even tree ring data,
Bill