In our All About Climate we talk about the solar cycle (soon to be updated in a paper to be published by the Fraser Institute) and using empirical methods to predict the solar and the likely results. We recently featured numerous papers that addressed this issue including this and this. 

The current solar cycle is the longest since the early part of the 20th century.  Solar minimum has yet to be reached, indeed there have been no signs yet of the start of cycle 24. In this paper in 2006 in the GRL, Clilverd et al. used a model for sunspot number using low-frequency solar oscillations, with periods 22, 53, 88, 106, 213, and 420 years modulating the 11-year Schwabe cycle, to predict the peak sunspot number of cycle 24 and for future cycles, including the period around 2100 A.D.  The good hindcasting results suggest this methodology has promise and that weaker and colder solar cycles are in our future the next few decades. They expect cycles 24 and 25 will have peak sunspot levels between 40 and 50 (cycle 23 which peaked in 2000, had a peak of 120, cycles 21 and 22 peaked near 160).  Low sunspot cycles of long length tend to bring about widespread global cooling.