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Abstract

Multimillennial-scale climate events are well-documented in ice-core records from both Greenland and Antarctica, yet the role of orbital and solar input oscillations in shaping these events remains unresolved. In this study, we analyze two high-resolution oxygen isotope records from Greenland and Antarctica to assess the influence of orbital cycles on global climate variability. Using two techniques, synchrosqueezing transform (SST) and Bayesian statistical analysis (BSA), we identify prominent climatic periodicities at ∼11, ∼5.5, and ∼2.75 kyr. The duration and amplitude of these oscillations correspond to bi-hemispherical (BHI) and equatorial insolation (EI) cycles and their harmonic emphasizing their role in shaping climate transitions during glacial and interglacial periods. We suggest that the shorter ∼2.75 kyr cycle may match the Hallstatt cycle, which is currently interpreted as a hypothetical solar cycle but could appear to be an EI harmonic. Further comparison with high-resolution BHI and EI records from other geographic zones confirms the presence of these cycles across multiple regions. The use of both SST and BSA techniques increases the robustness of our analysis by ensuring that potential signal artifacts are minimized and that weaker ∼5.5 and ∼2.75 kyr cycles are accurately detected. This study provides new insights into the drivers of major climate variability over the past 150,000 years, demonstrating the significant influence of BHI and EI cycles on Earth's climate system in the past and offering new perspectives on how these orbital cycles may continue to impact Earth's climate in the future.