This result is the open-source beta release of MAGICC (Model for the Assessment of Greenhouse Gas Induced Climate Change), a well-established reduced-complexity Earth system model widely used in climate research and assessments, including IPCC reports. MAGICC simulates global-mean climate responses to greenhouse gas and short-lived climate forcer emissions and is commonly applied in probabilistic mode to explore uncertainty ranges. Structurally, MAGICC represents the Earth using a four-box framework (land and ocean in each hemisphere), with an upwelling–diffusion ocean model, an energy-balance atmosphere, and parameterisations of the carbon cycle, methane cycle, aerosols and sea-level rise. It is also used as the climate module in several Integrated Assessment Models (IAMs).

The new open-source beta version, released within ESM2025, makes the MAGICC codebase transparent, inspectable and extensible for the research community. It enables reproducible workflows, closer integration with ESM and IAM research, and community-driven development, while clearly signalling its beta status for active testing, validation and further refinement.