Summarizes the science of climate change and impacts on the United States, for the public and policymakers.

Climate change poses many challenges that affect society and the natural world. With these challenges, however, come opportunities to respond. By taking steps to adapt to and mitigate climate change, the risks to society and the impacts of continued climate change can be lessened. The National Climate Assessment, coordinated by the U.S. Global Change Research Program, is a mandated report intended to inform response decisions. Required to be developed every four years, these reports provide the most comprehensive and up-to-date evaluation of climate change impacts available for the United States, making them a unique and important climate change document. The draft Fourth National Climate Assessment (NCA4) report reviewed here addresses a wide range of topics of high importance to the United States and society more broadly, extending from human health and community well-being, to the built environment, to businesses and economies, to ecosystems and natural resources. This report evaluates the draft NCA4 to determine if it meets the requirements of the federal mandate, whether it provides accurate information grounded in the scientific literature, and whether it effectively communicates climate science, impacts, and responses for general audiences including the public, decision makers, and other stakeholders.

The Pacific Northwest Case Study is a multi-agency analysis of atmospheric/climatic change impacts on the Pacific Northwest (which includes Washington, Oregon, Idaho, and portions of the Columbia River Basin in Western Montana). The purpose of the case study, which began in fiscal year 1991, was to develop and test analytical tools, as well as to develop an assessment of the effects of climate change on climate-sensitive natural resources of the Pacific Northwest and economic sectors dependent on them. The overall study, jointly funded by the US Department of Energy (DOE) and the US Environmental Protection Agency, was a broad-based, reconnaissance-level study to identify potential climate impacts on agriculture, coastal resources, forest resources, and irrigation in the Pacific Northwest. DOE participated in the reconnaissance study, with responsibility for hydroelectric and water supply issues. While this report briefly discusses a broader array of water issues, attention is mainly focused on three aspects of the water study: (1) the effects of the region's higher temperatures on the demand for electric power (which in turn puts additional demand on hydroelectric resources of the region); (2) the effects of higher temperatures and changes, both in precipitation amounts and seasonality, on river flows and hydroelectric supply; and (3) the effect of higher temperatures and changed precipitation amounts and seasonality on salmonid resources -- particularly the rearing conditions in tributaries of the Columbia River Basin. Because the meaning of regional climate forecasts is still quite uncertain, most of the preliminary findings are based on sensitivity analyses and historical analog climate scenarios.

Climate Change in the Northwest: Implications for Our Landscapes, Waters, and Communities is aimed at assessing the state of knowledge about key climate impacts and consequences to various sectors and communities in the northwest United States. It draws on a wealth of peer-reviewed literature, earlier state-level assessment reports conducted for Washington (2009) and Oregon (2010), as well as a risk-framing workshop. As an assessment, it aims to be representative (though not exhaustive) of the key climate change issues as reflected in the growing body of Northwest climate change science, impacts, and adaptation literature now available. This report will serve as an updated resource for scientists, stakeholders, decision makers, students, and community members interested in understanding and preparing for climate change impacts on Oregon, Washington, and Idaho. This more detailed, foundational report is intended to support the key findings presented in the Northwest chapter of the Third National Climate Assessment.