Estimating breakpoints in the Cenozoic Era: an econometric approach

Abstract. This study presents a statistical time-domain approach for identifying transitions between climate states, referred to as breakpoints, using well-established econometric tools. Our approach offers the advantage of constructing time-domain confidence intervals for the breakpoints, and it includes procedures to determine how many breakpoints are present in the time series. We apply these tools to a 67.1 million-year-long compilation of benthic foraminiferal oxygen isotopes (δ18O), which signify global temperature and ice volume throughout the Cenozoic. This foundational dataset is presented in Westerhold et al. (2020), where the authors use recurrence analysis to identify five breakpoints that define six climate states. Fixing the number of breakpoints to five, our procedure results in breakpoint estimates that closely align with those identified by Westerhold et al. (2020). By allowing the number of breakpoints to vary, we provide statistical justification for more than five breakpoints in the time series. Our method adds to our understanding of Cenozoic climate history in terms of the timing and rate of transitions between climate states and provides a tool for robustly assessing breakpoints in many other paleoclimate time series.