The CM2Mc is a foundational Earth system model, representing a coarse-resolution (3-degree) version of the Geophysical Fluid Dynamics Laboratory (GFDL) coupled model. It is specifically designed for comprehensive Earth system dynamics simulations, serving as an invaluable tool for climate modeling and investigating both past climate states and future climate change scenarios. Researchers utilize CM2Mc to explore the intricate mechanisms within the climate system and their complex interactions with global biogeochemistry, providing a robust platform for understanding Earth's climate processes. Technically, CM2Mc integrates several sophisticated components. It employs the GFDL Modular Ocean Model (MOM) version 5, configured with a nominal 3° × 3° lateral grid and 28 vertical levels, where the meridional resolution dynamically increases to 0.6° at the Equator to capture finer details of equatorial currents. The atmospheric component is the GFDL Atmospheric Model version 2.1 (AM2), featuring a latitudinal resolution of 3°, a longitudinal resolution of 3.75°, and 24 vertical levels. A key feature is the inclusion of the BLING (Biogeochemistry with Light, Iron, Nutrients and Gases) biogeochemical module, available in both its published v0 and a more advanced developmental version (including BLINGv1.5 and BLINGv2). All model components are seamlessly connected via the GFDL Flexible Modeling System (FMS). While sharing code with CM2.1, CM2Mc incorporates slight parameter adjustments for its coarser grid, resulting in approximately 10 times faster computation compared to CM2.1, albeit with some larger biases. The model's source code, written in Fortran90, is provided as a 67MB tar archive, and it has been updated to the GFDL Siena release. Successful compilation and execution require specific computer configurations and ancillary files. CM2Mc finds extensive application across various research domains, including climate change research, oceanography, carbon cycle studies, and paleoclimate investigations. It has been instrumental in conducting long-term equilibrium simulations, spanning thousands of years, under a wide range of external forcings such as atmospheric carbon dioxide concentrations, orbital parameters, and ice sheet configurations. Specific research applications include detailed studies of ocean carbon storage, global heat transport, overturning circulation, and the analysis of millennial-scale climate variability like Dansgaard-Oeschger events. The model's coarse resolution is a significant advantage, offering high computational efficiency that enables researchers to perform numerous model realizations and thoroughly explore complex Earth system processes. The availability of its simulation output and source code significantly benefits the scientific community, facilitating new discoveries and supporting a wide array of scientific publications. The CM2Mc Simulation Library offers comprehensive simulation output in NetCDF format, providing both timeseries (annual averages of each variable) and climatologies (monthly averages of each variable). Additionally, runscripts—shell scripts essential for defining runtime parameters and input files—are made available. As part of the public GFDL distribution, the model's source code and compile scripts are freely accessible, promoting transparency and collaborative research. CM2Mc has demonstrated versatility through its integration with other advanced models, such as LPJmL5, for biophysical coupling of dynamic vegetation, further expanding its utility in Earth system science. The development and ongoing availability of CM2Mc have been significantly supported by computational resources from leading institutions including Scinet (University of Toronto), the Canadian Foundation for Innovation, Compute Canada, and McGill University.