The population of Iceland fell by half, but that may have been caused by skeletal fluorosis after the eruption of Laki in 1783.
Several causes have been proposed: cyclical lows in solar radiation, heightened volcanic activity, changes in the ocean circulation, an inherent variability in global climate, or decreases in the human population.
Evidence from mountain glaciers does suggest increased glaciation in a number of widely spread regions outside Europe prior to the twentieth century, including Alaska, New Zealand and Patagonia.
Greenland was largely cut off by ice from 1410 to the 1720s.
Many springs and summers were cold and wet but with great variability between years and groups of years.
Freezing of the Golden Horn and the southern section of the Bosphorus took place in 1622.