[论文解读] Understanding the Earth as a whole system: From the Gaia Hypothesis to Thermodynamic Optimality and Human Societies

Axel Kleidon|arXiv (Cornell University)|May 19, 2020

Earth Systems and Cosmic Evolution参考文献 28被引用 8

一句话总结

本文提出，地球系统作为一个接近热力学极限的热力学系统运行，太阳能辐射的能量转换为功，驱动着物理、生物和人类系统的复杂过程。通过将地球视为一个受热力学最优性支配的整体系统，该研究将涌现行为与盖亚假说联系起来，并通过能量流约束提供了一个统一且简化的框架，以理解可持续性与人类影响。

ABSTRACT

The notion that the whole is more than the sum of its parts has a long tradition in science. This, of course, also applies to the Earth system. With its myriad of processes, spanning from purely physical to life and human activity, the Earth is a vastly complex system. It may thus seem that there is nothing simple and general to say because of this overwhelming complexity. What I want to show here is that by formulating the Earth as a thermodynamic system, one can identify general directions and infer simple functioning because thermodynamics imposes fundamental limits on the dynamics. At the center of this description are energy conversions and states of disequilibrium, which are at the core of the dynamics of Earth system processes, from convection cells to living organisms and human societies. They are linked to each other and interact by their exchanges of energy and mass, and ultimately affect how much of the input of low entropy solar radiation from the Sun is converted into free energy, energy able to perform work, before the energy gets re-emitted by the Earth as high entropy terrestrial radiation. The emergent thermodynamic behavior of the Earth then becomes simple because the dynamics evolve to and operate at thermodynamic limits. Such behavior of Earth system processes operating at the edge of their limit can then be linked to previously described holistic theories, such as the Gaia hypothesis, with similarities in the described emergent behavior. Such a thermodynamic view, however, can go further, as it can also be used to understand the role of human societies in the Earth system and the potential pathways to a sustainable future. Thermodynamics taken together with the energy conversions and interactions within the Earth system can thus provide a basis to understand why the whole Earth system is more, and simpler, than the sum of its spheres.

研究动机与目标

• 探究热力学原理是否能够统一地球物理、生物和人类系统的运行行为。
• 通过识别支配其动力学的一般性、简单定律，解决地球系统科学中的复杂性挑战。
• 探讨热力学最优性如何解释盖亚假说中观察到的涌现行为。
• 通过热力学约束评估人类社会在地球系统中的作用。
• 通过能源系统分析，为可持续发展路径提供基础。

提出的方法

• 将地球形式化为一个由太阳辐射输入驱动、以地球辐射形式耗散能量的热力学系统。
• 将最大熵产生原理（MEP）作为地球系统过程中热力学最优性的代理。
• 将大气对流、生物圈生产力和人类能源使用中的能量转换视为自由能转化的表现。
• 利用能量和熵平衡来量化从低熵太阳输入到高熵输出的能量转换效率。
• 将观测到的地球系统行为与理论热力学极限进行比较，以推断最优运行状态。
• 通过将人类社会的能源使用建模为地球能量流网络的一部分，将其整合进热力学框架。

实验结果

研究问题

• RQ1 热力学原理如何解释地球系统在物理、生物和人类领域中的自组织行为？
• RQ2 观测到的地球系统动力学在多大程度上与热力学最优性（如最大熵产生）一致？
• RQ3 能量转换效率的概念如何与人类社会在地球系统中的可持续性相关联？
• RQ4 盖亚假说在多大程度上能通过热力学约束和能量流优化得到支持？
• RQ5 热力学极限对未来行星可持续发展路径有何影响？

主要发现

• 地球系统在接近热力学极限的条件下运行，能量转换驱动着大气、海洋、生物圈和人类过程的动力学。
• 热力学最优性，特别是最大熵产生，为地球系统多样行为提供了统一原则。
• 地球系统的涌现行为——如气候调节和生物圈生产力——可被理解为在约束条件下能量流最大化的结果。
• 人类社会并非外部扰动，而是地球能量流系统不可或缺的组成部分，其能源使用对整体熵产生有贡献。
• 该框架支持可持续发展与热力学原理一致的观点，即高效能源利用和最小能量耗散是关键。
• 将人类系统整合进热力学框架揭示，长期可持续性要求与行星尺度能量流极限保持一致。