The head of a Cambridge nonprofit organization advocating for restoring the role of science in United States policy-making decisions will be speaking in Arlington High School’s media center at 7:30 p.m. Thursday. The presentation by Kevin Knobloch, president of the Union of Concerned Scientists, is being hosted by the League of Women Voters of Arlington and Arlington Community Education. Knobloch will discuss his organization’s new initiative, the Center for Science and Democracy, which aims to combat what it says is an excessively partisan political climate and a cluttered media landscape that combine to drown out science-based findings with misinformation or information manipulated by private interests. David Whitford, an editor at large for Fortune magazine, will moderate the event. Admission is $5, and tickets will be available at the door.