5.6 The Suess cycle
One periodicity that arises in many radiocarbon studies of solar activity has a well defined period of
about 210 years. This is often referred to as the Suess or de Vries Cycle (Suess, 1980). Although the
variations in the calculated production rates of 14C and 10Be are well correlated with each other (Vonmoos
et al., 2006) and with the 400-year sunspot record (Berggren et al., 2009), there is little evidence of the
Suess Cycle in the sunspot record itself.