Paul Costello is a Berlin-based senior program manager for GMF Cities. He leads the team’s City Directors of International Affairs (CDIA) Network and contributes to GMF Cities’ democracy, disinformation, migration, and Ukraine projects.

Costello has a background in public policy and prior work experience in sustainability and public diplomacy programs.  He holds a master’s degree in public policy from the Hertie School of Governance in Berlin and a bachelor’s degree in political science from McGill University in Montreal.

Steven Bosacker is Senior Vice President for Innovation and directs the GMF Cities program, which supports local-level policymakers and practitioners in North America and Europe by facilitating the transatlantic exchange of knowledge for building inclusive, sustainable, and globally engaged cities. 

Before joining GMF, Steven was the principal for public sector and partnerships at Living Cities, where he focused on finding and furthering promising practices in large city governments to improve life for low-income residents. The public-sector innovation portfolio included projects such as City Accelerator, Civic Tech and Data Collaborative, and Racial Equity Here, an initiative devoted to implementing racial equity in city government operations.  

Adrienne Goldstein is a Senior Program Coordinator with GMF Technology, focusing on disinformation and social media platforms. She graduated magna cum laude with a B.A. in History from Middlebury College, where she was a member of the Media Portrayals of Minorities Project lab.  

Annika Vollmer is a Brussels-based senior program coordinator for GMF’s Leadership Programs. She oversees the EU-US Young Leaders Seminar, and designs and implements other programs, including the Marshall Memorial Fellowships, the Transatlantic Inclusion Leaders Network, and the Schuman Challenge. All the programs foster skills development, critical thinking, and cross-cultural understanding among next-generation leaders.

Fluent in German and English, Vollmer holds a master’s in international relations with a specialization in security studies from Leiden University and a bachelor’s degree in European studies from Maastricht University.

Gesine Weber is a fellow on GMF’s Geostrategy team, where she works on European security and defense issues. Based in Paris, she focuses on EU defense initiatives, security and defense policy of the E3 (France, Germany, and the United Kingdom), and Europe's role in the global order. 

During a 2024 fellowship at the Arnold A. Saltzman Institute for War and Peace Studies at Columbia University, Weber led a research project on European balancing in the Indo-Pacific in the context of US-China competition. 

Prior to joining GMF, she worked as a defense policy adviser at the German parliament and as a consultant for the Friedrich-Ebert-Foundation in Shanghai. Weber is pursuing a PhD in defense studies at King’s College London, where she is part of the European Foreign Policy Research Group and contributes to the work of the Centre for Grand Strategy. She is an associate researcher for the European Council on Foreign Relations and a nonresident Hans J. Morgenthau Fellow at the Notre Dame Center for International Security.

Weber holds a master’s degree in European affairs from Sciences Po in Paris and another master’s degree in political science from the Freie Universität Berlin. She studied Mandarin at the Beijing Foreign Studies University. Her writing and commentary appears regularly in English, French, and German in European and other international media, including the BBC, the Neue Züercher Zeitung, Politico, and France 24.