Reports of rising global temperatures have raised questions about responses to climate change, including efforts to (1) reduce carbon dioxide (CO2) emissions, (2) adapt to climate change, and (3) design and develop climate engineering technologies for deliberate, large-scale intervention in Earth's climate. Reporting earlier that the nation lacks a coordinated climate-change strategy that includes climate engineering, GAO now assesses climate engineering technologies, focusing on their technical status, future directions for research on them, and potential responses. To perform this technology assessment, GAO reviewed the peer-reviewed scientific literature and government reports, consulted experts with a wide variety of backgrounds and viewpoints, and surveyed 1,006 adults across the United States. Experts convened with the assistance of the National Academy of Sciences advised GAO, and several reviewed a draft of this report. GAO incorporated their technical and other comments in the final report as appropriate.