As a contentious new round of high-stakes nuclear talks between Iran and world powers wraps up in Baghdad, it is important to think critically about how much of a threat Iran poses to the United States. According to former senator Rick Santorum, for example, a nuclear Iran would have "carte blanche to spread a reign of terror around not just the Middle East, but here in America ... [and] across Western civilization." Republican presidential candidate Mitt Romney has argued that "if the Iranians are permitted to get the bomb, the consequences will be as uncontrollable as they are horrendous." Several leading U.S. senators penned an op-ed in March stating that "the prospect of a nuclear-armed Iran is a threat to the entire world, including particularly the U.S."
It is not just politicians who hold these views. A recent CNN poll revealed that more than three-quarters of the American public sees Iran and North Korea as "serious" threats while only 44 percent feels the same way about Russia. Indeed, fear of the Iranian threat in the United States is more widespread today than fear of the Soviet threat was in 1985, even though at that time the Soviet Union possessed the largest nuclear arsenal in the world and today Iran doesn't have a single nuclear weapon.
Which raises an obvious question: Does the dominant perception of the Iranian threat actually square with reality? To answer that question, we designed the Nuclear Annihilation Threat (NAT) Index -- a way of systematically and empirically assessing the existential threat that nuclear-weapon states (NWSs), and potential nuclear-weapon states, pose to one another. What we found is striking: Although Israel is right to see Iran as an existential danger, the United States has blown the Iranian threat to itself all out of proportion -- and Iran is unlikely to find existential security in a nuclear weapon. In addition, both Israel and the United States should be focusing much more aggressively on the threat posed by Pakistan.
Unlike any other weapon, nuclear weapons can jeopardize a nation's very existence. We use the term "existential threat" to denote the capability of one state to completely annihilate another. In concrete terms, a nuclear attack on one U.S. city would be catastrophic, but it would not destroy the United States. A similar nuclear attack on Tel Aviv, on the other hand, would potentially kill 42 percent of the Israeli population and most likely spell the end of the Jewish state. By focusing exclusively on existential dangers, we seek to understand how nuclear weapons affect the core survival motivations that drive states' behavior. While this may be a narrow perspective, we think that isolating this unique characteristic of nuclear weapons yields important insights.
Our NAT Index is a relational metric that draws on four factors in determining the existential threats that nuclear-armed countries pose to one another: 1) the potential damage a country's nuclear arsenal could cause to a target's population; 2) the ability of a country to strike a target with ballistic missiles; 3) the presence of a strategic rivalry between the two countries; and 4) the risk of state failure in the country that is hypothetically attacking a target. The NAT Index can also be used to identify which nuclear-armed countries pose the greatest existential threats overall and which are the most vulnerable.
Pakistan's nuclear arsenal, for example, is capable of inflicting higher levels of proportional damage to a country the size of Israel than a country the size of China because of geographic and demographic differences. Countries that are rivals of North Korea and are within range of its ballistic missiles face a greater existential threat from Pyongyang than those that are not. We factor in the risk of state failure because an unstable country's leaders and governmental policies can change on a dime and destabilized regimes can lose command and control of their nuclear weapons, exposing the arms to theft or unauthorized use.
While our index accounts for the heightened existential risks created by rivalries, we do not assume that nuclear-armed allies pose no risks to one another. From a realist perspective, the military power of other states can never be safely ignored -- especially with respect to weapons that possess such uniquely destructive power. Beyond realism's admonishment that today's allies could become tomorrow's rivals, the risks of nuclear weapons accidents and misuse exist between both rivals and allies. While it may appear odd to consider Britain as a potential nuclear threat to the United States, remember that Pakistan is also a U.S. ally. In accounting for the threats that even allies' nuclear weapons pose, our analysis reflects the view that all nuclear weapons -- no matter who possesses them -- present a grave international security threat.