In the period between 1645 and 1715, very few sunspots were observed (almost none). This is in sharp contrast to the periods before and after. This epoch of low sunspot activity is called the Maunder minimum, after solar astronomer E. W. Maunder.

The Maunder minimum coincides with a period of unusually cold winters, known as the Little Ice Age, though the causal relationship, if even present, is not understood.

Source: http://www.hao.ucar.edu/public/education/sp/great_moments.2.html