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Boom or bust? Reducing nuclear arsenals below a certain level gets tricky.

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Nuclear Disarmament Science: How to Be Dumb Enough to Be Smart

SAN DIEGO, CALIFORNIA—As underscored by today’s announcement by Vice President Joe Biden, the Obama Administration has undertaken a historic effort to cut its nuclear arsenal. The science to do it safely and credibly is ready to go, says a new study presented here today at the annual meeting of the American Association for the Advancement of Science (which publishes ScienceNOW). But the surprising political and diplomatic conundrums involved with shrinking the U.S. and Russian stockpiles are numerous and formidable.

The secret of cutting the U.S. and Russian arsenals—roughly 7200 and 6000 weapons, respectively—is doing it in a way that both sides can trust that the other is actually reducing its nukes but without revealing too much information. An American Physical Society panel comprised of physicists and policy experts and led by former weapons inspector Jay Davis found no scientific showstoppers to doing so. Scientists have techniques in hand, for example, to work with explosive materials, confirm that weapons are destroyed, and scan a weapon without dismantling it to measure its destructive power. And one of the report’s key recommendations—more science in these areas—is already coming to fruition, as President Barack Obama has requested a 10% increase in the National Nuclear Security Administration’s research budget for this work, up to roughly $350 million.

What’s lacking are the more stringent agreements that would allow scientists on the Russian and U.S. sides to use the tools they have.

The key irony in the arsenal-cutting endgame is that as arsenals get smaller, the job gets tougher, not easier. That’s because the numbers matter more. In a smaller arsenal, knowing the exact number of the other side’s nukes can be the difference between nuclear parity and superiority.

Right now, each side uses so-called counting rules to extrapolate from their adversary’s delivery systems—missiles or bombers—to the number of actual nukes (e.g., that missile means this number of warheads). As the numbers drop from the thousands into the hundreds, the United States, Russia, and other members of the nuclear club will want to actually confirm for the first time how many warheads each system carries. That will require delicately worded treaties that balance top-notch physics with strategic ambiguity. “We have to be smart enough to detect the weapon but dumb enough so that the verification test doesn’t divulge valuable secrets,” says Davis. Scientists and policymakers “have to find a way to do it and not learn information the other side wants to protect.”