Hockey stick authors: Did we mention that the last century of our hockey stick isn't statistically robust?

Fresh Thoughts from Authors of a Paper on 11,300 Years of Global Climate Changes - NYTimes.com

the 20th century portion of our paleotemperature stack is not statistically robust, cannot be considered representative of global temperature changes, and therefore is not the basis of any of our conclusions.

If 20th century isn't statistically robust, how do we know that the 12th century is statistically robust?