Abstract
Cynics said it was Monica's fault. Others pointed to the near-visceral loathing of some Republican senators for anything emerging from the Clinton White House. The academically inclined argued that the ascendancy of unilateralism in Congress was blocking everything from the payment of U.N. dues to the ratification of the Kyoto Protocol on climate change. But two contentious arms control questions also influenced the Senate's vote against ratifying the Comprehensive Nuclear Test Ban Treaty (CTBT) last October.
The first was whether the U.S. nuclear arsenal could be maintained under a test ban; the second, whether a test ban could be verified–in other words, to what extent could any surreptitious nuclear explosion, no matter where or when, be detected?
Very little time was devoted to the complexities of either of these questions, but many senators zeroed in on the alleged shortcomings of the partially completed Vienna-based, treaty-mandated verification system. Little was done to rebut inaccurate–and sometimes deliberately misleading–claims about verification. And just days before the vote, intelligence reports were leaked suggesting that the Russians might be conducting small nuclear tests that had not been detected.
In response, in August we at the London-based Verification Research, Training and Information Centre (VERTIC) decided to convene the “Independent Commission on the Verifi-ability of the CTBT.” We drew together 14 scientists and experts in verification techniques and technologies from a variety of government agencies, academia, non-governmental organizations, and the future CTBT organization. (The commission members, who met in London on October 26 and 27 to finalize their report, acted in their personal capacities.)
“We asked the group to assess the verifiability of the CTBT both now, as the treaty verification system is being completed, and in the future, as more capabilities are added.
Commissioners were not asked to consider U.S. national security requirements, or the military significance of a small, clandestine nuclear test or series of tests. They were asked to consider only the issue of verifiability. They were also asked to examine the totality of available verification capabilities, not just those envisioned by the treaty.
The commissioners' conclusions, while scientifically rigorous, are presented in a clear and simple manner in a report that can be found on the Web (www.CTBTcommission.org).
Their consensus report, released in London on October 30, concludes that any event that might possibly be considered a nuclear test is highly likely to be detected, located, and identified. The report does not claim that the treaty is 100 percent verifiable–an impossible demand to make of any verification system–but it finds that the test ban is verifiable with “high probability.”
First, the “International Monitoring System” (ims) being established by the Provisional CTBT Organization in Vienna will employ four technologies–seismic, hydroacoustic, infra-sound, and radionuclide detection–that can readily detect explosions as small as 1 kiloton at any point on the globe. The ims system will include 321 sites around the world which will be linked via a dedicated global communications infrastructure to the International Data Center in Vienna. Once the system is completed, both raw and processed data will be available promptly to all treaty parties. A technically advanced signatory like the United States, for instance, is already receiving ims data–which it uses in its own independent analyses.
The commissioners strongly rejected that view. They noted that, while the 1-kiloton level was the minimum capability that scientists had used when conservatively estimating the system's capabilities, the system's developers nonetheless expected its actual capabilities to go far beyond that. Even the partially completed ims, said the commissioners, had detected explosions below 1 kiloton in some regions, particularly in Central Eurasia.
The international, independent commission concluded that any nuclear test is highly likely to be detected, located, and identified.
THE COMMISSIONERS
Even more dramatic was the evidence for infrasound technology, which has detected the sound of space shuttle launches in Florida from as far away as Canada, and that of the now-halted Concorde flights over the Atlantic from a station in Germany (both craft produce high-frequency waves similar to those emitted by a nuclear explosion).
Three types of so-called wave-form data, and measures of radioactive particles and gases released by atmospheric nuclear explosions or underground explosions that vent into the atmosphere, are used synergistically to detect, locate, and identify explosions as nuclear. Because some ra-dionuclides are produced only by nuclear explosions, radionuclide detection technology is the “smoking gun” of non-compliance.
Radionuclide detection is also the critical tool in on-site inspections, which the treaty calls for when, on the basis of information from the ims and/or a treaty member's “national technical means” of verification, treaty parties conclude that an illicit nuclear explosion may have taken place. Commission members felt that a well-prepared on-site inspection regime will serve as a powerful deterrent because of the high probability that clandestine testing will be discovered.
They noted that many countries have sizable national capabilities, both classified and unclassified. The international verification organization and member states can use data from these systems to provide themselves with additional reassurance. The United States, for example, has very sophisticated equipment–including optical, infrared, visible, gamma ray, and X-ray satellite sensors and an extensive seismic system, the Atomic Energy Detection System–and it is believed to have additional, classified means. Other countries, including Russia, France, and Britain, also have relevant technologies.
Unlike the Senate in its discussion, the commission noted the valuable contribution to verification of the thousands of openly accessible scientific and environmental monitoring stations that can detect evidence of a clandestine nuclear explosion. By the end of the next decade, open sources are expected to include as many as 10,000 non-government digital seismic stations linked in a global network entirely separate from the treaty monitoring system. In some cases this network is and will be more powerful than the treaty monitoring system.
Cheap commercial satellite imagery with global coverage is also becoming increasingly available. The communications revolution is making these information sources accessible in real-time, and to everyone on the globe.
Like the Senate, the commission considered the ways a cheater might try to hide a clandestine nuclear test from the verification system through some elaborate evasion scenario.
Three methods were considered–decoupling, hiding the event in another event, and conducting an explosion in an area and environment where attribution would be problematic. The latter two scenarios were dismissed on the grounds that no credible examples of how they might work could be identified.
So-called decoupling, in which an attempt is made to attenuate the seismic signals of a nuclear explosion by detonating it in an underground cavity (either in an existing cavern or one specially constructed for the purpose), was also regarded as incredible.
The possibility of obtaining a decoupling factor of 70 (so that a 70-kiloton explosion could be made to look like a 1-kiloton explosion)–an assertion that went unchallenged during the Senate debate–was regarded as implausible by the commissioners. They concluded that such an undertaking faced severe technical, financial, and organizational hurdles. Even the most sophisticated nuclear weapon states would have difficulty trying to fool all the elements of the verification regime simultaneously.
Taken together, the treaty-mandated system and additional verification means available to the international community will be a powerful deterrent to any state contemplating an illicit nuclear test.
A map and graphs of the Kursk explosions, from www.geo.arizona.edu/geophysics/faculty/wallace/RUSSIANSUB/.
By looking at all means of detection–not just the treaty-mandated monitoring system–the commission was able to draw a much truer picture of verifiability than that painted for the U.S. Senate. Viewed from the perspective of a potential violator, a constantly evolving, technologically advanced, and multi-layered CTBT verification gauntlet will present a nightmare of uncertainty to any would-be treaty violator.