Well first I would say, "7 centuries? It's only 572 years!" Then I would point out that it's actually only 332 years since a chunk of 240 years of the Japanes

Well first I would say, "7 centuries? It's only 572 years!" Then I would point out that it's actually only 332 years since a chunk of 240 years of the Japanese freeze data (ending at 1922-23) are considered invalid and therefore not used in the analysis. Then you can just fall back on not denying climate change but denying the man-made aspect of it, or pointing out what a tiny sample this is in relation to human existence.