Banning Nuclear Tests

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Science  21 May 2010:
Vol. 328, Issue 5981, pp. 953
DOI: 10.1126/science.1190789

Throughout May 2010, a review of the treaty on the non-proliferation of Nuclear Weapons (NPT) is taking place at the United Nations, where its nearly 200 parties are considering the treaty's “state of health” and ways to eliminate nuclear weapons. This follows intense activity last month, in which the United States took important steps toward this goal. So it's crucial that the next important step not be missed: fully implementing the Comprehensive Nuclear-Test-Ban Treaty (CTBT). This requires U.S. ratification.

In his Prague speech a year ago, President Obama affirmed the U.S. commitment to a world free of nuclear weapons. Last month, he outlined a path for achieving this goal in the Nuclear Posture Review, sending a strong message that the role of nuclear weapons in the country's defense strategy would be reduced. This was bolstered by signature of the U.S.-Russian New Strategic Arms Reduction Treaty, in which both countries agree to lower limits on the numbers of nuclear warheads and delivery systems. And at the April Nuclear Security Summit, the United States stressed the need to address nuclear terrorism around the globe. There is now new momentum toward global nuclear disarmament, driven by an administration that takes it seriously.


Yet the ban on nuclear tests—the next such step toward this goal—has still not been ratified by the United States. Originally proposed a half-century ago, the CTBT was eventually opened for signature in 1996, building on decades of scientific, technical, and diplomatic efforts. As of 2009, 151 nations, including all U.S. NATO allies and Australia, Japan, and South Korea, have ratified the treaty. Unfortunately, the U.S. Senate declined to approve it when it was hastily brought up for a vote in 1999. The main concerns were the treaty's value for arms control and nonproliferation, confidence in U.S. nuclear weapons in the absence of testing, and effective verification of the ban.

The Senate has good reasons to change its mind now, especially given developments since 1999. Under the CTBT, nuclear-armed states cannot advance their nuclear weapon technologies, and states seeking nuclear weapons cannot progress beyond primitive untested devices. The ban's function as a qualitative constraint is viewed by NPT parties as essential for the continued viability of the nonproliferation regime. The Stockpile Stewardship Program has ensured that U.S. nuclear weapons have been maintained in good condition over the 18 years since the U.S. testing moratorium began. But moratoriums (other nuclear-armed states have also declared them) are weak reeds, lacking the stability of a legally binding agreement. New independent assessments show that confidence in the reliability of the stockpile will be maintained so long as adequate funding and scientific talent are devoted to the task. As for verification, the United States monitors for nuclear tests with seismometers, satellites, and other technologies. Such means are better now than in 1999. The Vienna-based commission preparing for CTBT implementation is provisionally operating an international monitoring system of seismic, radionuclide, hydroacoustic, and infrasound sensors. International studies released in 2009 show that this system performs better than expected and that the ability to conduct on-site inspections is within reach. With today's verification capabilities, there is a real probability of detecting a cheating attempt at any yield.

It would be seriously destabilizing if any nuclear-armed state were to resume testing, a risk that entry into force of the CTBT, and thus its full implementation, would mitigate. The treaty cannot enter into force without the United States, and many of the nations who must approve it by terms of the agreement, but who have not yet ratified it—China, Egypt, India, Indonesia, Iran, Israel, North Korea, and Pakistan—are unlikely to act before the United States does. U.S. leadership on the CTBT is essential, and it needs to be exercised now to achieve a lasting end to nuclear tests.

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