In 2017, the US government released the first volume of its Fourth National Climate Assessment (NCA4), which was "designed to be an authoritative assessment of the science of climate change, with a focus on the United States." Based on an extensive body of peer-reviewed scientific research and datasets, this report concluded that "it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming [and other global climate changes] since the mid-20th century." Here, readers can download the report's 36-page executive summary, which is written for broad audiences, or the 477-page full report as PDFs. Individual PDFs of the report's 15 chapters are also available, as are PDFs of its public comments and peer reviews. Each chapter focuses on a particular topic and includes key findings, regional analyses, and traceable accounts of supporting evidence, along with an assessment of the state of the science regarding that topic. With the National Oceanic and Atmospheric Administration leading thirteen federal agencies in its preparation, NCA4 was produced by Congressional mandate under the Global Change Research Act of 1990.