The response of Earth’s climate system to orbital forcing has been highly state dependent over the past 66 million years. The states of past climate Deep-sea benthic foraminifera preserve an essential record of Earth's past climate in their oxygen- and carbon-isotope compositions. However, this record lacks sufficient temporal resolution and/or age control in some places to determine which climate forcing and feedback mechanisms were most important. Westerhold et al. present a highly resolved and well-dated record of benthic carbon and oxygen isotopes for the past 66 million years. Their reconstruction and analysis show that Earth's climate can be grouped into discrete states separated by transitions related to changing greenhouse gas levels and the growth of polar ice sheets. Each climate state is paced by orbital cycles but responds to variations in radiative forcing in a state-dependent manner. Science, this issue p. 1383 Much of our understanding of Earth’s past climate comes from the measurement of oxygen and carbon isotope variations in deep-sea benthic foraminifera. Yet, long intervals in existing records lack the temporal resolution and age control needed to thoroughly categorize climate states of the Cenozoic era and to study their dynamics. Here, we present a new, highly resolved, astronomically dated, continuous composite of benthic foraminifer isotope records developed in our laboratories. Four climate states—Hothouse, Warmhouse, Coolhouse, Icehouse—are identified on the basis of their distinctive response to astronomical forcing depending on greenhouse gas concentrations and polar ice sheet volume. Statistical analysis of the nonlinear behavior encoded in our record reveals the key role that polar ice volume plays in the predictability of Cenozoic climate dynamics.

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过去 6600 万年地球气候及其可预测性的天文记录

在过去的 6600 万年中，地球气候系统对轨道强迫的响应高度依赖于状态。过去气候状态 深海底栖有孔虫保存了地球过去气候的氧和碳同位素组成的重要记录。然而，该记录在某些地方缺乏足够的时间分辨率和/或年龄控制来确定哪些气候强迫和反馈机制最重要。韦斯特霍尔德等人。提供了过去 6600 万年的高解析度和年代久远的底栖碳和氧同位素记录。他们的重建和分析表明，地球的气候可以分为由与温室气体水平变化和极地冰盖增长相关的转变分隔的离散状态。每个气候状态都受轨道周期的影响，但以依赖于状态的方式响应辐射强迫的变化。科学，这个问题 p。1383 我们对地球过去气候的大部分了解来自对深海底栖有孔虫中氧和碳同位素变化的测量。然而，现有记录中的长间隔缺乏对新生代气候状态进行彻底分类并研究其动态所需的时间分辨率和年龄​​控制。在这里，我们展示了我们实验室开发的一种新的、高分辨率的、天文年代的、连续的底栖有孔虫同位素记录复合材料。根据温室气体浓度和极地冰盖体积对天文强迫的独特反应，确定了四种气候状态——温室、暖房、冷藏室、冰库。