Scientists often bring issues to the policy agenda, translating scientific questions into everyday language and political terms. When Roger Revelle characterized Earth as a spaceship in testimony to Congress in 1957, his evocative language framed the issue of our planet's climate vulnerability in a way that technical discourse could not. In this book, Ann Campbell Keller examines the influence of scientists on environmental policymaking and makes the novel argument that scientists' adherence to the role of neutral advisor varies over the course of the policymaking process. Keller divides the policy process into three stages--agenda setting, legislation, and implementation--and compares scientists' influence on acid rain and climate change policy at these different stages over the course of several decades. She finds that scientists face more pressure to uphold the ideal of objectivity as policy-making processes advance and become more formalized, and thus are more likely to engage in advocacy and persuasion in the earlier, less formal, agenda-setting stage of the process. In the later, more structured legislative and implementation phases, scientists--working hard to give the appearance of neutral expertise--cede the role of persuader to others.Keller draws on theoretical work in political science and science studies and on empirical evidence from scientific reports, news coverage, congressional hearings, and interviews. Focusing on comparable cases and considering scientists' participation in them over time, she offers unique insights into how the context of decision making affects scientists' policy influence and emphasizes the multiple pathways by which scientific meaning is constructed in public settings. The hardcover edition does not include a dust jacket.