A deep-rooted concept in the dendrosciences is to infer climate or ecosystem variability from statistical relationships established between tree-ring and instrumental data. By extent, these relationships can then be extrapolated into past or future time frames, for example, to anticipate the impacts of anthropogenic climate change on forest ecosystems. Problematically, evidence is mounting that matters are not so simple and that the uncertainties associated with temporal and spatial scaling of tree-ring data are substantial.