Interpretation of climate dynamics from phase space portraits: Is the climate system strange or just different?

Abstract

Traditional concepts of spectral analysis are inadequate to characterize the behavior of paleoclimatic data sets because the power spectrum of a nonlinear system is not invariant. Reconstructed phase space portraits of global ice volume proxy data over the past 2100 kyr show that variations in global ice volume during the Pleistocene have resulted from a complex interplay of internal dynamics and insolation forcing. The evolution of global ice volume over this period can be characterized as a series of stepwise transitions between at least five “states” representing stable distributions of ice masses on the globe. Similar stepwise transitions are observed in an ice core temperature record extending over the past 240 kyr. The number of states and their location in phase space are governed by several factors, including continental configurations, distribution of mountain ranges, the number of stable oceanographic circulation configurations, and atmospheric composition. In contrast, phase space portraits of calculated values of Northern Hemisphere insolation and an ice core dust flux record demonstrate chaotic behavior.