Maunder Minimum
A more modern theory attributes tree growth during a time of global low temperatures during the Little Ice Age associated with unusually low solar activity of the Maunder Minimum, circa 1645 to 1750, during which cooler temperatures throughout Europe are believed to have caused stunted and slowed tree growth, resulting in unusually dense wood. Further evidence for this "Little Ice Age theory" comes from a simple examination of the dense growth rings in the wood used in Stradivari's instruments. Two researchers – University of Tennessee tree-ring scientist Henri Grissino-Mayer and Lloyd Burckle, a Columbia University climatologist – published their conclusions supporting the theory on increased wood density in the journal "Dendrochronologia".