Evidence of past climate variations are stored in ice and indicate
glacial-interglacial cycles characterized by three dominant time periods of
20kyr, 40kyr, and 100kyr. We study the scaling properties of temperature proxy
records of four ice cores from Antarctica and Greenland. These series are
long-range correlated in the time scales of 1-100kyr. We show that these series
are nonlinear as expressed by volatility correlations and a broad multifractal
spectrum. We present a stochastic model that captures the scaling and the
nonlinear properties observed in the data.Comment: 4 revtex pages, 4 figures, 1 tabl