The best studies tend to test the robustness of their conclusions by dropping
various subsets of data or by excluding whole classes of data (such as tree - rings) in order to see what difference they make so you won't generally find that too much rides on any one proxy record (despite what you might read elsewhere).
As similar results were obtained with
various subsets of the data (first and second halves of the time series; data for Northern and Southern Hemispheres, Figure 6) and for the de-seasonalized monthly data, Figure 7, this estimate of the time constant would appear to be robust.
Not exact matches
When many groups
of people treating
various subsets of adjusted and raw
data using a variety
of statistical approaches all come up with almost exactly the same trend, the evidence is strong is that such reconstructions are robust.