Pleistocene climate: deterministic or stochastic?

Application of a simple linear model to the earth's ice volume record of the past 730,000 years indicates that although forcing by variations in the earth's orbital parameters of tilt and precession is real, it is small (less than 25 percent of the variance in the record). No relationship with the eccentricity is observed. This indicates that the Pleistocene glacial variations are largely stochastic in nature.