Book excerpt: This report describes Phase I of a two-phase study proposed and organized by the NOAA Climate Program Office (CPO) in early 2014 for the development of a NOAA Holistic Climate and Earth System Modeling Strategy. Defining NOAA's strategy for global climate and earth system modeling for research and operations allows NOAA's investments in this area to be optimally targeted and leveraged, facilitates linkages with broader environmental modeling efforts within NOAA and outside of NOAA, and enhances NOAA's participation in the interagency Earth System Prediction Capability initiative. A strategy also helps to identify gaps and opportunities to advance NOAA's global climate and earth system models and identify resources and synergies needed to maximize the return on those investments. In addition, the 2012 National Research Council report on "A National Strategy for Advancing Climate Modeling" prompts a careful reconsideration of NOAA's strategy in this area. Phase I defines the current state of, and plans for, NOAA's global climate and earth system models, developed at the Geophysical Fluid Dynamics Laboratory, the Earth System Research Laboratory, and the National Centers for Environmental Prediction Environmental Modeling Center. This report lays the necessary groundwork for the planned second phase of the CPO proposed study whose ultimate goal is to present potential future model development pathways contributing to the definition of a holistic strategy to advance NOAA global climate and earth system models for research and operations. doi:10.7289/V5DB7ZRC (http://dx.doi.org/10.7289/V5Z31WKK)