Abstract. A new Earth system model of intermediate complexity – CANOPS-GRB v1.0 – is presented for use in quantitatively assessing the dynamics and stability of atmospheric and oceanic chemistry on Earth and Earth-like planets over geologic timescales. The new release is designed to represent the coupled major element cycles of C, N, P, O, and S, as well as the global redox budget (GRB) in Earth's exogenic (ocean–atmosphere–crust) system, using a process-based approach. This framework provides

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... mechanistic model of the evolution of atmospheric and oceanic O2 levels on geologic timescales and enables comparison with a wide variety of geological records to further constrain the processes driving Earth's oxygenation. A complete detailed description of the resulting Earth system model and its new features are provided. The performance of CANOPS-GRB is then evaluated by comparing a steady-state simulation under present-day conditions with a comprehensive set of oceanic data and existing global estimates of bio-element cycling. The dynamic response of the model is also examined by varying phosphorus availability in the exogenic system. CANOPS-GRB reliably simulates the short- and long-term evolution of the coupled C–N–P–O2–S biogeochemical cycles and is generally applicable across most period of Earth's history given suitable modifications to boundary conditions and forcing regime. The simple and adaptable design of the model also makes it useful to interrogate a wide range of problems related to Earth's oxygenation history and Earth-like exoplanets more broadly. The model source code is available on GitHub and represents a unique community tool for investigating the dynamics and stability of atmospheric and oceanic chemistry on long timescales.