Nonlinearity and multifractality of climate change in the past 420,000 years

Evidence of past climate variations are stored in polar ice caps and indicate glacial‐interglacial cycles of ∼100 kyr. Using advanced scaling techniques we study the long‐range correlation properties of temperature proxy records of four ice cores from Antarctica and Greenland. These series are long‐range correlated in the time scales of 1–100 kyr. We show that these time series are nonlinear for time scales of 1–100 kyr as expressed by temporal long‐range correlations of magnitudes of temperature increments and by a broad multifractal spectrum. Our results suggest that temperature increments appear in clusters of big and small increments—a big (positive or negative) climate change is most likely followed by a big (positive or negative) climate change and a small climate change is most likely followed by a small climate change.