These records did not meet the minimal replication requirement of at least 8 independent contributing tree cores. (wattsupwiththat.com)
But a new study of centuries - old tree core samples indicates an abrupt turn of the weather around the first decade of the 13th century. (scientificamerican.com)
I expect tree cores will only be useful to stir the mix but why not give it a shot? (climateaudit.org)