Oxidizing ExoCAM: Introducing the Radiative Effects of Oxygen and Ozone into the ExoCAM General Circulation Model

Abstract Oxygen and ozone are two of the most important gases in Earth’s atmosphere. These arose as a result of photosynthesis and appeared prominently around 2.3–2.4 billion yr ago. For exoplanets, these species have been proposed both as remote biosignatures and antibiosignatures, depending on the abundances and astrophysical context. ExoCAM, an extension of the Community Earth System Model for deep paleoclimate and exoplanets, has previously been limited to anoxic atmospheres. This work presents a substantial update to the radiative transfer in ExoCAM to include the effects of oxygen and ozone. We describe the implementation of line lists, empirical cross sections, Rayleigh scattering, and collision-induced absorption and test the resulting framework in 1D and 3D for the modern Earth atmosphere. We quantify the changes in flux, temperatures, and circulation due to the two gases.