People often have a hard time grasping how dificult it is to statistically distinguish between the vaunted multiproxy studies and red noise. Here are a few interesting images from the Jones et al  proxy roster, which I’ve been working on.
Figure 1. Scatterplot of Jones proxies (grey)all scaled to 1901-1950 interval as in Jones et al  . Cyan – annual average of proxies. Red- smoothed graph. Blue – level required for the mean to be "significantly" different from 0 using critical t-statistic of 1.96 (this is too low given autocorrelation, but is the OLS value). Bottom panel – standard deviations by year.
The most remarkable impression is surely the tremendous lack of consistency of proxies in any given year. You see this used to argue that the MWP was regional or occurred in different places at different times, but surely it is just as remarkable to see the lack of consistency in 20th century proxies, especially since they have already undergone a cherrypicking process even to be in the table. There are very few years in which the average of the proxies can be said to be inconsistent with a mean of 0. The blue lines show a 95% confidence interval. There are 990 years here -so there are actually fewer cyan values outside the confidence intervals than one would expect from random numbers with a mean of 0 – this is without even bringing autocorrelation into the equation.
The lower panel shows standard deviations by year. The standard deviation for all the proxies is 1.15 (a little higher than one since 1901-1950 standardization is used.) If an annual "signal" were being captured, one would assume that the standard deviation by year would be much reduced from the overall variability, as proxies presumably swung to one side or the other of the baseline. The average of the annual standard deviations is 1.09, so that there is negligible reduction of variance. I suspect that a little red noise in the benchmark would do the same.
Since this graphic could be a bit confusing if there were high interannual correlations, next is a version in which the grey shows the range of proxy values in any given year. I’ve also shown a blow-up for the 20th century. The series levels off after 1935. Interestingly, the maximum value of the red curve is in 1396 – compare this to Crowley’s imprecations against the inconceivability of a reconstruction with a warm early 15th century (not that we advocate this.)
Figure 2. As above. Vertical line is in 1935.
As a test of signal, I’ve applied the method which I presented in my analysis of Esper – a studentized glauch…". This shows that there is virtually no "signal" in this set of proxies (compare to chart in my Esper post). Again, it’s hard to see the non-signal in the MWP is any worse than the non-signal in the 20th century (this chart includes the Polar Urals series in the 11th century which is almost surely incorrectly dated.
Is this all due to regional variability or is it due to lousy proxies?