DOES THE SUN VARY?
Compared to some stars, which can vary in apparent brightness by factors of a hundred or more, the Sun seems like constancy itself. On the other hand, there are those 11-year sunspot cycles. Furthermore, astronomical history shows that sunspots can virtually disappear for decades on end, with notable climatic consequences.
For example, the British amateur astronomer E. Walter Maunder drew attention to the fact that from 1645 until 1715 sunspots virtually disappeared for reasons still unknown. Astronomers label this period the Maunder Minimum, and note that it coincides with a period that climatologists now call the Little Ice Age, when winters were more severe than normal, and summers were shorter and cooler.
Scientists are only starting to explore the connections between activity on the Sun and the weather on Earth. Our climate system is highly complex, and there is little established theory to explain just how the Sun might affect it, but it is already clear that there is a definite link.