User-friendly carbon-cycle modelling and aspects of Phanerozoic climate change

Carbon-cycle modelling is essential for testing the main carbon sources and sinks as climate forcings, and we introduce and describe GEOCARBNET, a graphical user interface for the geologic carbon and sulfur cycle model GEOCARBSULFvolc. The software system is menu-driven, user-friendly, and the user is never far removed from the basic input parameters from which atmospheric CO2 and O2 concentrations can be derived. GEOCARBNET is supplied with several published models and the user can easily test and refine these models with different parametrizations. GEOCARBNET also contains libraries of models and proxy data, which easily can be compared with each other. Our examples focus on how to use GEOCARBNET in the context of Phanerozoic climate change and highlights how certain key input parameters can seriously affect reconstructed CO2 levels.