Abstract Current understanding of the long-term carbon cycle posits that Earth's climate is stabilized by a negative feedback involving CO2 consumption by chemical weathering of silicate minerals. This theory holds that silicate weathering responds to climate: when atmospheric pCO2 and surface temperatures rise, chemical weathering accelerates, consuming more atmospheric CO2 and cooling global climate; when pCO2 falls, weathering fluxes decrease, permitting buildup of CO2 and consequent warming. However, the functional dependence of global weathering rates on atmospheric pCO2 (Earth's “weathering curve”) remains highly uncertain, with a variety of mathematical formulations proposed in the literature. We explore the factors influencing this relationship, and how they may have changed over Earth history. We then revisit classic carbon cycle model experiments to demonstrate how the choice of weathering curve has dramatic consequences for the response of the Earth system to several types of climatic and carbon-cycle perturbations. First, the slope of the weathering curve determines the timescale of recovery and the “long tail” of elevated pCO2 following carbon release events. Second, the nature of Earth's weathering curve determines the response of pCO2 to changing volcanic CO2 degassing, which has varied significantly over geologic timescales. Finally, we demonstrate how changes to Earth's weathering curve over time driven by, for example, tectonic or evolutionary processes, can act as a forcing, in addition to a feedback, in the carbon cycle and climate. These examples highlight the importance of constraining Earth's weathering curve, both for improving our understanding of past carbon cycle perturbations and predicting the future impact of anthropogenic carbon release on long timescales.

中文翻译：

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硅酸盐风化作为地球气候和碳循环的反馈和强迫

摘要 目前对长期碳循环的理解假定地球气候通过负反馈稳定，包括硅酸盐矿物的化学风化导致的 CO2 消耗。该理论认为，硅酸盐风化对气候有反应：当大气pCO2和地表温度升高时，化学风化加速，消耗更多大气CO2，使全球气候降温；当 pCO2 下降时，风化通量会减少，从而导致 CO2 积聚和随之而来的变暖。然而，全球风化率对大气 pCO2（地球的“风化曲线”）的函数依赖性仍然高度不确定，文献中提出了各种数学公式。我们探讨了影响这种关系的因素，以及它们在地球历史上可能发生的变化。然后，我们重新审视经典的碳循环模型实验，以证明风化曲线的选择如何对地球系统对几种类型的气候和碳循环扰动的响应产生重大影响。首先，风化曲线的斜率决定了恢复的时间尺度和碳释放事件后 pCO2 升高的“长尾”。其次，地球风化曲线的性质决定了 pCO2 对不断变化的火山 CO2 脱气的响应，这在地质时间尺度上变化很大。最后，我们展示了地球风化曲线随时间的变化，例如，由构造或进化过程驱动的变化如何在碳循环和气候中起到强制作用和反馈作用。这些例子强调了限制地球风化曲线的重要性，