“Was there a Medieval Warm Period somewhere in the world in addition to the area surrounding the North Atlantic Ocean, where its occurrence is uncontested? This question is of utmost importance to the ongoing global warming debate, for if the Medieval Warm Period is found to have been a global climatic phenomenon, and if the locations where it occurred were as warm in medieval times as they are currently, there is no need to consider the temperature increase of the past century as anything other than the natural progression of the persistent millennial-scale oscillation of climate that regularly brings the earth several-hundred-year periods of modestly higher and lower temperatures that are totally independent of variations in atmospheric CO2 concentration.”
Proving that the Medieval Warm Period was widespread is useful in the climate debate because it demonstrates that recent warming, if it happened, was consistent with previous events. Same is true for the Roman Optimum.
But failing to prove the MWP was widespread does not validate the CAGW position. That position is invalidated by the failure of their own measures to increase when CO2 production is increasing. As their own team member said, “We can’t account for the lack of warming and it’s a travesty.”