On the statistical nature of distinct cycles in global warming variables
Cycle times found in many oceanic time series have been explained with references to external mechanisms that act on the systems. Here we show that when we extract cycle times from 100 sets of paired random series, we find six distinct clusters of common cycle times ranging from about 3 years to about 32 years. Cycle times, CT, get shorter when one series in a pair is an increasingly stronger leading series, measured as LL-strength, to the other, CT ≈ - (minus) LL-strength. This may explain the frequent finding that many global warming time series, e.g., the Southern oscillation index and the Pacific decadal oscillation, show distinct cycle times (Power spectral analysis: 3-5, 7-8, 13-15, 22-24, and 29-30 years). An important implication of these findings is that processes that strengthen the impact of one ocean variable on another may cause more frequent adverse climate conditions.
Seip, Knut Lehre