Unfortunately, I'm not a specialist in the subject -- I have an interest in it, but also an interest in everything from artificial intelligence to Indo-European linguistics -- so I will reluctantly say that I'm out of my league here; but I advise that you look into the field more widely, and not confine yourself to RealClimate.org -- which has long struck me as on the same level of sincere inquiry as the kinds of people who deny the reality of the Sun Streak project or the plausibility of plasma cosmology. (Make of that what you will, of course; you may be proud to be a member of that group...)

Edit: One thing I can say is that the Medieval Warm Period and the Little Ice Age did occur world-wide; following Fernand Braudel's _The Structures of Everyday Life_ and the _Annales Histoire_ school of economic historians in general, the same climate phenomena were encountered in both Europe and China, which are by no means part of the same sub-planetary climate spheres.