At a conference on the future of al Qaeda sponsored by Los Alamos 
National Laboratory last month, I posed a dark question to 60 or so nuclear 
weapons scientists and specialists on terrorism and radical Islam: How many of 
them believed that the probability of a nuclear fission bomb attack on U.S. soil 
during the next several decades was negligible -- say, less than 5 
percent?
At issue was the Big One -- a Hiroshima-or-larger explosion that could 
claim hundreds of thousands of American lives, as opposed to an easier-to-mount 
but less lethal radiological attack. Amid somber silence, three or four meek, 
iconoclastic hands went up. (More later on the minority optimists. They, too, 
deserve a hearing.)
This grim view, echoed in other quarters of the national security 
bureaucracy in recent months, can't be dismissed as Bush administration 
scaremongering. "There has been increasing interest by terrorists in acquiring 
nuclear weapons," Mohamed ElBaradei, the Egyptian director general of the 
International Atomic Energy Agency, the world's chief nuclear watchdog, said in 
a recent interview, excerpts of which were published in Outlook last Sunday. "I 
cannot say 100 percent that it hasn't happened" already, he added, almost as an 
afterthought.
Worried yet? Then you might agree that there is too little specific, 
rigorous, apolitical discussion of this threat available to the public. In an 
era when Americans know they have reason to be afraid -- yet seem at times to 
know more fear than reason -- even the unthinkable requires transparent debate. 
Here's a provocation, in service of the cause of inspiring such debate: In 
focusing all-out on nuclear aspirants such as Iran and North Korea, the United 
States may be distracting itself from an even graver problem.
A time machine traveler tuning in to the American discussion about 
nuclear proliferation early in 2005 might think the dial had been set to 1965 by 
mistake. Then as now, American arms control debate focused heavily on the fear 
that too many governments would go nuclear. The Bush administration recognizes 
that catastrophic terrorism has changed the context in which states own or seek 
to acquire nuclear weapons. Yet traditional nonproliferation thinking, focused 
on governments, still dominates U.S. policy. When President Bush mentioned 
nuclear dangers in his State of the Union address last week, he referred only to 
the problem of governments seeking weapons. That challenge remains urgent, but 
it does not explain the gloom at Los Alamos.
A startling number of U.S. nuclear and terrorism specialists I have 
talked with during the last year believe that the threat of a jihadi nuclear 
attack in the medium term is very serious. They recognize that as a technical 
and scientific matter, such an attack can be very difficult for private groups 
to pull off. They fear it anyway. They may have professional incentives to 
conjure the worst case, but I believe this to be their honest assessment.
At the center of their pessimism stands the unique figure of Osama bin 
Laden, still at large, still espousing his ideology of mass-casualty attacks 
against Americans, with a special emphasis on nuclear weapons -- an ideology 
that seems destined to outlive him.
Some of these analysts, confronting uncertainty, may lean toward 
pessimism because, with the stakes so high, they would rather be wrong than fail 
to anticipate a preventable attack.
Back in 1998, when he was still an obscure White House aide, Richard 
Clarke was accused of scaremongering about a little-known terrorist named Osama 
bin Laden in order to win budgetary funds from Congress. 
"I would be delighted three or four years from now to say we've wasted 
money," he replied. "I'd much rather have that happen than have to explain to 
the Congress and the American people why we weren't ready, and why we let so 
many Americans die."
September 11 taught us that Chicken Little sometimes gets it right. But 
the failures to correctly assess Saddam Hussein's weapons of mass destruction 
showed that he sometimes gets it wrong.
Once again, the stakes are very high and once again, the adversary is 
hidden and dynamic. Among other difficulties, the al Qaeda near the heart of the 
current nuclear threat is not the same al Qaeda feared by Clarke seven years 
ago.
At its birth in 1988, al Qaeda was a poorly equipped summer camp for 
volunteer soldiers near Khost, Afghanistan. By the summer of 2001, it had a 
formal headquarters, management committees, a dozen or more training facilities, 
global recruiting centers, a few thousand sworn members and thousands of other 
followers.
Today al Qaeda is no longer much of an organization, if 
it can be called one at all. Its headquarters have been destroyed, its 
leadership is scattered or dead or in jail. Osama bin Laden remains the chairman 
of the board, increasingly a Donald Trump-like figure -- highly visible, very 
talkative, preoccupied by multiple wives, but not very effective at running 
things day-to-day.