... among other things, the report says that a continued ebb of the sun’s field could lead to a “mini ice age,” of the sort that last happened in the 17th century. According to a 2002 study by Michael Mann, then of the University of Virginia, the Little Ice Age appears to have been a 400-year period between the 16th and 19th centuries in which the Earth cooled 0.6 of a degree Celsius, and is concurrent with the last drop in solar wind.