Those are strange things to compare to global warming. Most sources give the Medieval warm period as applying to Europe, the North Atlantic, or maybe northern hemisphere, but as far as I can tell the global temperature is supposed not to have been warmer than now. That’s certainly what Skeptical Science gives with some discussion of how well the sun explains current climate changes.
I don’t think anybody disputes that major climate changes can be driven by planetary cycles; that’s the usual story for the ice ages. But that doesn’t preclude atmospheric changes causing others, which is what for instance what I’ve seen suggested for the existence of ice ages in the Carboniferous, and by nearly all accounts is a much better explanation for the present peak.
