CGD extends beyond atmospheric physics to atmospheric chemistry, biogeochemical cycles, hydrology and ecosystems. In so doing, CGD developed the Community Earth System Model (CESM), and this modeling enterprise is the hub of CGD’s activities. Vital elements for CESM’s development include modern parameterizations, software engineering and observational datasets. A critical level of effort is maintained in all areas through extensive collaborations with the greater CESM community. Through the open and inclusive CESM research and development procedures, CGD realizes its vision as a source and integrator of fundamental insights into the governing processes, numerical modeling and overall behavior of the Earth’s climate system.