Siena Cicarelli is a Fellow at the Center for Climate and Security (CCS), an institute of the Council on Strategic Risks (CSR), and Program Director at the Nexus25 project, a joint CCS-Istituto Affari Internazionali (IAI) initiative focused on sustainable multilateralism supported by Stiftung Mercator in Germany. Prior to joining CCS, she led Women, Peace, and Security (WPS), international humanitarian law, atrocity prevention, and global partnerships as an analyst for the U.S. Department of Defense. She has previously worked on transatlantic relations and human security issues for Eurasia Group, the Center for American Progress, and the National Democratic Institute. Siena holds an MSc from the London School of Economics and Political Science and a BA in International Studies from American University.