Abstract. Here we revisit reported alkenone δ¹³C (δ¹³C_C37) based CO₂ records during the Plio-Pleistocene and apply a refined approach to better constrain the dynamic range of CO₂ during the time. Specifically, we consider ways to correct for regional differences in physical oceanographic factors. As a result of our relatively simple approach we find that offsets of ~150 ppm between reported δ¹³C_C37 CO₂ records from different sites can be significantly reduced. This confirms that better constraints on environmental variables, including physical oceanographic controls on depth and season of production are key aspects for improving δ¹³C_C37 based CO₂ estimates. The revised δ¹³C_C37 CO₂ datasets suggest that Plio-Pleistocene CO₂ levels are 180–350 ppm, which is consistent with the most of reported CO₂ reconstructions, though their upper end of Pliocene CO₂ levels are lower than that of some CO₂ estimates.

中文翻译：

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上新世-更新世期间基于烯烃 δ ¹³ C 的修订版CO ₂估计值

摘要。在这里，我们重新审视了上新世-更新世期间报告的基于烯烃 δ ¹³ C (δ ¹³ C _C37 ) 的 CO ₂记录，并应用改进的方法来更好地限制 CO ₂在此期间的动态范围。具体来说，我们考虑纠正物理海洋学因素区域差异的方法。由于我们采用相对简单的方法，我们发现报告的 δ ¹³ C _C37 CO ₂之间的偏移约为 150 ppm来自不同站点的记录可以显着减少。这证实了对环境变量的更好约束，包括对生产深度和季节的物理海洋学控制，是改进基于δ ¹³ C _C37的 CO ₂估计的关键方面。修订后的 δ ¹³ C _C37 CO ₂数据集表明上新世 CO ₂水平为 180-350 ppm，这与大多数报道的 CO ₂重建一致，尽管它们的上新世 CO ₂水平上限低于一些CO ₂估计。