CESM

The Community Earth System Model (CESM) is a comprehensive, open-source global climate model designed to simulate the physical and biogeochemical components of the Earth’s climate system. It integrates the atmosphere, ocean, land surface, sea ice, and optional components into a single framework and is used for climate variability studies, historical reconstructions, and future projections. CESM is developed and maintained by the National Center for Atmospheric Research (NCAR) with contributions from a wide international community of universities and national laboratories, and is supported by a collaborative governance structure and release cycle.

CESM is modular and built on the Earth System Modeling Framework, with core components including the Community Atmosphere Model (CAM), the Community Land Model (CLM), and the ocean and sea-ice components (e.g., POP or MOM and CICE, respectively). These components are connected by the CESM coupler (CPL) to exchange energy, momentum, moisture, and tracers on multiple grids. The model supports various resolutions and configurations and runs on high-performance computing platforms.

Historically, CESM evolved from the Community Climate System Model (CCSM) and began releasing major versions in the early 2010s, with CESM2 and subsequent updates delivering improved physics, biogeochemistry, and performance. The model is widely used for historical simulations, climate change projections, and specialized experiments such as large-ensemble studies that explore internal climate variability.

CESM outputs are typically stored in NetCDF format and used by researchers, policymakers, and educators. The project maintains extensive documentation and community support, including workshops and tutorials, to foster broad participation in climate science.