In this 20th issue, the Foreign Minister of Iraq, Hoshyar Zebari, reports on the steps taken by the Iraqi parliament towards ratification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) and the importance Iraq attaches to promoting the Treaty’s entry into force. Ambassador Thomas Pickering, who helped the Kennedy administration draft the Partial Test Ban Treaty, describes why the case for ratification of the CTBT by the United States is stronger than ever. Zia Mian from Princeton University focuses on the role of civil society in South Asia in advocating nuclear disarmament. Columbia University’s Paul Richards explains the seismic findings of the nuclear test announced by North Korea on 12 February; we also elaborate on the radionuclide findings almost two months later. Astronomer Margaret Campbell-Brown from the University of Western Ontario explains how CTBTO data have helped us understand the characteristics of the meteor over the Ural mountains on 15 February. Anders Ringbom and Anders Axelsson of the Swedish Defense Research Agency describe the key role played by noble gas detection systems in responding to the Fukushima nuclear accident in March 2011 and some of the lessons learned. This issue also features an interview with CTBTO Executive Secretary Tibor Tóth in which he discusses a range of issues related to nuclear non-proliferation, including the main challenges and achievements during his eight years as head of the organization. Finally, the paintings by Elin O’Hara Slavick from the University of North Carolina at Chapel Hill on the cover and inside Spectrum 20 illustrate the power of art in educating and communicating political messages.