This special issue aims to bring together contributions from different disciplines of the Earth system to describe and demonstrate the importance of thermodynamics and related thermodynamic optimality principles (such as maximum entropy production, maximum power/dissipation, and minimum energy expenditure) in understanding and predicting the behavior, organization, and evolution of thermodynamic Earth systems. Contributions may include manuscripts of more theoretical nature that describe the general relationship of thermodynamics and optimality to the complexity and evolution of Earth systems, and manuscripts that describe applications of thermodynamic approaches to atmospheric and hydrologic sciences as well as human impacts and habitable environments.