Experts disagree about whether the earlier 1300s start should be included in The Little Ice Age :

Armstrong blogged recently the theory that it might be reduced cosmic radiation that forms the causal correlation to increased volcanic and tectonic activity. Increasing volcanic soot emissions can exacerbate global cooling, e.g. the Year Without a Summer.

Presumably solar activity peaked in the 11th or 12th century?

P.S. the huge rise “hockey stick” at the right edge of the chart above is a lie constructed from manipulated temperature data.