Evidence for large century time-scale changes in solar activity in the past 32 Kyr, based on in-situ cosmogenic 14C in ice at Summit, Greenland

We discuss the proxy evidence from tree ring and sediment based records of atmospheric 14C/12C ratios during the three epochs. These records have been used as a measure of changes in cosmic ray flux, and solar activity in the past. However, since they are also appreciably affected by climatic changes, a comparison of the two records is potentially valuable for delineating the nature of past changes in solar activity, and large-scale ocean circulation and air-sea exchange.