Perhaps the most distinctive feature of sunspots is that their number increases and decreases in a regular fashion over about a decade. The most famous of these is known as the Maunder minimum, from 1645 to 1715. The variation in the number of sunspots over a decade or so suggests than they also contribute to solar climate . In conjunction with the sunspot cycle, the magnetic poles of the Sun reverse their polarity on the same time scale, which influences the interaction with the Earth's magnetic field. As we will see, sunspots and the features that accompany them on the solar surface are an important component of variations in the radiation from the Sun.
Sunspots directly contribute to the reduction of the solar irradiance.