The Little Ice Age following the Medieval Warm Period ended because of an increase in solar output coupled with changes in thermohaline circulation, and a global decrease in volcanic activity. The solar increase has since reversed, and global temperature and solar activity are now going in opposite directions. And there has been (as yet) no major change in the ocean conveyor or global volcanism. So the Medieval Warm/Little Ice Age graph really does not "explain" anything about the current warming. It is just obfuscation.
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