The Climate Data Guide provides concise and reliable information on the strengths and limitations of the key observational data sets, tools and methods used to evaluate Earth system models and to understand the climate system. Citable expert commentaries are authored by experienced data users and developers, enabling scientists to multiply the impacts of their work and the diverse user community to access and understand the essential data. The Climate Data Guide was named an exemplary community resource by the 2012 U.S. National Academies' report, A National Strategy for Advancing Climate Modeling, and is an element of the strategic plan for NCAR's Climate and Global Dynamics Laboratory. NCAR, the National Center for Atmospheric Research, is located in Boulder, Colorado and is widely respected as a leading institution in the atmospheric and related sciences.