This book offers valuable climate policy and climate assessment lessons, depicting what it takes to build a sustained climate assessment process. It explores the third U.S. National Climate Assessment (NCA3) report as compared with previous US national climate assessments, from both a process and content perspective. The U.S. Global Change Research Program is required by law to produce a National Climate Assessment report every four years, and these reports provide a comprehensive evaluation of climate science as well as observed and projected climate impacts on a variety of sectors.   As the book describes, a key contribution of the NCA3 approach is a far more deliberate interdisciplinary process, as well as an engagement strategy that brought hundreds of public and private sector stakeholders into the assessment community. Among its most important conceptual contributions was an explicit focus on building the infrastructure to conduct better assessments over time and an experimental approach to analysis of the impacts of climate on cross-sectoral systems and inter-locking and cascading effects across sectors.  Readers may explore innovations such as the development of regional climatologies and projections for every region of the US, as well as the development of the Global Change Information System. The book also highlights the need for decision-makers to be part of the assessment process, in order for assessment findings to be truly useful from a decision-makers perspective. Many lessons have been learned by the NCA3 authors that can be useful in future assessments and adaptation processes, both within the US and internationally. This book passes on such lessons and includes an evaluation of the role of state climate assessments in ongoing national assessment processes.