The Fermi Paradox and Nuclear Terrorism: Where are the Mushroom Clouds?

29 September marked the birthday of Enrico Fermi, one of the 20th centuries more noted physicists. It was Fermi that posed the famous paradox, since named after him, on the probability of extraterrestrial intelligence. To mark the occasion I reproduce an article on the Fermi paradox with respect to nuclear terrorism that I wrote a few years back, and which I have come to learn was cited in a book on Pakistan’s nuclear programme. Nice 🙂 I think the article’s central conclusions hold up well despite the passage of time.

Fermi’s Paradox and the Risk of Nuclear Terrorism.

Those who have even a passing acquaintance with matters nuclear need no introduction to “the Pope”, Enrico Fermi. He has left us with a deep intellectual imprint. One of his more curious contributions, known as “Fermi’s Paradox”, concerns itself with the existence of extra-terrestrial intelligence.

Enrico Fermi was dubious about the intuitively high probability that people make for the existence of extra-terrestrial intelligence. His paradox is often used to question high probability estimates for ET. Fermi simply, in effect, asked; “if the probability is so high then why aren’t they here?”

Some probabilistic risk assessments for nuclear terrorism are also relatively high.

Matthew Bunn has it at 29% over 10 years, the same level as the median risk reached in a poll of international security experts. Bunn reaches his conclusion based on a mathematical model, but the numbers put into it are largely subjective. So we may well have here subjective risk disguised through the use of equations, an artifice practised on Wall Street in ways that are now all too painfully familiar to us.

Graham Allison cites, at a minimum, a 51% probability over the decade (he states that the chances are “more likely than not”) and Richard Garwin had it 20% year on year. There is no reason to suppose why these estimates could not have been made in the early 1990s following the collapse of the Soviet Union.

Other estimates are low. Henry Sokolski, according to Brian Jenkins, had the odds at one in ten million prior to 9/11 and now has it at one in a million. A Sandia National Laboratory Report on al-Qaeda, written in 1998, essentially had that probability at zero for improvised nuclear devices.

The Obama administration, echoing the sentiments of every major US Presidential candidate since 9/11, asserts that the risk of nuclear and biological terrorism is the leading security threat faced by the United States. Moreover, administration officials have also asserted that the risk is both high and increasing. Despite this declaration the Obama White House proposes to take funding away from nuclear non proliferation efforts, which include programmes to tackle the threat of nuclear terrorism, and channel it to programmes designed to modernise US nuclear warheads.

Why, if the risk of nuclear terror be so high and be increasing over time? I can think of two major reasons. One might be that the risk is high, but nonetheless the administration has higher policy priorities. The other is that despite all the rhetoric the administration understands that the risk of nuclear terrorism is very low.

The same considerations apply in the case of biological terrorism. Early on in his term Obama shifted funds away from counter biological terrorism programmes towards scientific projects directed at meeting the challenge posed by the prospect of global flu pandemics.

The latter move was much condemned, but it was probably the most sensible thing the administration has done. Many biologists and pathologists have warned that the risk of a nasty global outbreak of virulent forms of influenza virus is higher than a truly catastrophic act of biological terrorism.

We might invoke Fermi’s Paradox to evaluate these two different schools of thought on the risk of nuclear terrorism, but always bearing in mind that the reasoning is readily applicable to the biological case. If nuclear terrorism has been such a serious threat, since the early 1990s, why hasn’t there been a terrorist detonation, or an attempted detonation, already? The question is a useful one to ask for it invites us to consider the underlying arguments that are made in the high probability cases.

There are three pillars underpinning much of the current literature on nuclear terrorism, which is biased towards the high risk end of the spectrum. Namely, (1) a bomb isn’t that hard to make if sufficient nuclear materials are at hand (2) nuclear materials have not been adequately secured and more work is needed (3) terrorism itself has evolved such that previous limits to violence no longer apply.

The high risk approach may be summarised as the “supply-side approach.” This is because, upon this view, the main constraint that terrorists face is access to the necessary nuclear materials. Because these could be guarded and accounted for better it follows that militarily skillful terrorist groups have a relatively good chance of finding themselves in the position of gaining access to the material needed to fuel a bomb, should they make a determined effort to do so.

The second pillar lies at the core of the supply side approach. This pillar focuses on the security of Russian nuclear materials and highly enriched uranium in research reactors, especially in unstable parts of the undeveloped world. In the 1990s such concerns prompted the Nunn-Lugar Cooperative Threat Reduction Program and have subsequently led to global efforts to lock down nuclear materials and convert research reactors to low enriched uranium.

To be sure high risk arguments depend upon the second pillar, but it is the first and second that gives this pillar weight. Terrorists are both capable and determined.

The position was recently neatly encapsulated by Kenneth Brill, who heads the US National Counterproliferation Center, who stated; “The knowledge is out there. The drive – seen most clearly in states like North Korea and terrorist groups like al-Qaeda – is out there, and the materials can be found.”

Therefore, “the WMD proliferation challenge in the 21st century is keeping states and nonstate actors from doing what they can do if they choose to do so”.

The first pillar relies on the alleged ease of manufacture of a gun-assembled bomb, such as the type used against Hiroshima. During the first wave of concern about nuclear terrorism, in the 1970s, the focus was on the expansion of nuclear power and the future of plutonium reprocessing. The current literature is more focused on highly enriched uranium.

Three empirical examples are often cited in support of the first pillar. Firstly, it is argued that the Hiroshima gun-assembly bomb was so easy to make, certainly relative to the implosion based plutonium bomb, that it did not even require testing. Secondly, in a way similar to the Manhattan Project case, the Nth country experiment demonstrates the ease of gun-assembly because the students involved rejected this route on account of its simplicity. Thirdly, the South African bomb program was based on gun-assembled weapons and proved to be relatively inexpensive with the overall enterprise creating a small footprint easy to conceal. This is in reference to the design and manufacture of the bomb, not the enrichment of uranium.

In 1977 an imminent panel of experts, many of whom worked on the Manhattan Project itself, stated that there is no appreciable asymmetry in difficulty between gun-assembly and implosion in so far as terrorism is concerned. They pointed out that the difficulties involved with gun-assembly manufacture are by no means trivial.

Given the source this advice ought not simply be dismissed or glossed over. Of course, Luis Alvarez famously stated that a terrorist need only drop a metal hemisphere of highly enriched uranium metal on another from a favorable height, but this claim has been widely dismissed. Although Thomas Cochran and Matthew McKinzie have repeated this calculation assuming the more highly pure uranium metal typical of today. They report its feasibility but this has not been independently assessed and nor are the calculations publicly available.

The argument actually compounds the Fermi Paradox.

The Hiroshima bomb design was extensively cold tested. Implosion was something both novel and challenging, indeed even the study of explosives and ordnance was not a firm science prior to the Manhattan Project. That was an important reason behind John von Neumann becomig a part of the Project at Los Alamos. The implosion device was tested because it had a higher probability of pre-detonation. That is not necessarily an indicator of difficulty in manufacture and design.

A plutonium based gun-assembly bomb has a much higher, in fact an altogether too high, probability of pre-detonation but that doesn’t mean that it is harder to construct than an implosion bomb. It means that it won’t work if built.

Besides even if we take implosion to be a tougher nut to crack than gun-assembly that should not imply that gun-assembly is so easy that all it takes is access to the necessary nuclear materials. It would just mean that implosion is harder than gun-assembly. An argument based on the relative hardness of implosion manufacture should not be used to make absolute conclusions about gun-assembly.

The Nth country experiment, in which physics postdocs were tasked with designing a feasible weapon, has been widely misunderstood, as Michael Levi persuasively argues. Levi points out that nuclear weapons manufacture requires both theoretical and experimental work. Terrorists without access to nuclear weapon scientists would have to not just design or even build a bomb they would have to invent it.

The South African example is based on an obvious logical fallacy. It might well be the case that the South African bomb design and manufacturing effort was inexpensive and had a low footprint, but the fact remains that the effort was made by South Africa’s best scientists and engineers. Terrorists did not build the South African bomb.

The third pillar focuses on terrorism itself. Historically there have been many terrorist groups ranging from across the political spectrum, but one common feature has been that these groups have tended to be revolutionary or nationalist groups with clear political goals. The limited and concrete nature of their objectives has, in turn, had the affect of limiting their violence. Terrorist groups were capable of much greater levels of mayhem. This was neatly captured by Brian Jenkins’ well known refrain that “terrorists want a lot of people watching not dead.”

However, the 1990s saw the rise of terrorist groups, often motivated by religious or millenarian views that transcended such self limiting objectives. The 1993 bombing of the World Trade Centre, the Oklahoma City bombing, the Tokyo sub way nerve gas attack and the 9/11 plot all empirically demonstrate this, it is argued. If the operational goal of some terrorists are now more expansive then mass casualty terrorism becomes more likely.

In the case of al-Qaeda and similar Salafi jihadist groups the argument rests on the nature of jihadi ideology, which by combining the religious with the political suggests the existence of transcendental goals of the type suited for catastrophic terrorism. Others see al-Qaeda actions as stemming from an aggressive jihadi ideology designed to create Islamic states in the Muslim world and thereupon expand the reach of Islam globally through aggressive war. Such a war could be prosecuted, at the very least, under an umbrella of power provided by nuclear weapons. In this case nuclear terrorism would take the familiar form that we associate with nuclear deterrence, otherwise known as that “sturdy child of terror”. Robin Frost, by contrast, has argued that al-Qaeda has mostly political objectives that preclude acts of catastrophic terrorism just as it did with more traditional politically based terrorist groups.

It would seem, certainly in the case of Osama bin Laden’s key associate Ayman al-Zawahiri, that the attack upon the United States arose out of strategic considerations rather than ideological ones. The use of strategic studies in academic surveys of al-Qaeda has thus far been largely neglected, given the reluctance to ascribe rationality and strategic choice to al-Qaeda operational objectives. In so far as catastrophic terrorism is concerned it is precisely irrational and millenarian groups that are most to be feared, according to the literature, so ascribing rationality to al-Qaeda actually serves to undermine the argument.

Ascribing a strategic rationale for the attack upon the US should not be seen as a reason for optimism. Al-Qaeda seeks to drive the US out of the Middle East. However, the Middle East is a vital region for the US under the prevailing foreign policy construct. If al-Qaeda wants to use force to achieve this objective then it will have to escalate the conflict, which leaves open the prospect of catastrophic terrorism arising not from some irrational ideology but from the rational application of strategic choice.

The spectacular nature of 9/11 surely had something to do with America’s status as the world’s unipolar power during that era of international relations that we may call “the unipolar moment.” There is more to be said here, but I leave that aside. These matters will be further discussed in my book on the topic.

It is argued that al-Qaeda and Aum Shinrikyo had WMD programs, even nuclear ones and so we must, thereby, inscribe intention to al-Qaeda. In the 1990s al-Qaeda had a measure of sanctuary in Taliban ruled Afghanistan and was determined to mount a spectacular assault on the US homeland. Aum Shinrikyo had a vast $1 Billion budget and dabbled in all three forms of WMD. In the end Aum botched an improvised, not truly weaponised, nerve gas attack even though it had scientific expertise.

So if all three pillars in the high risk case are true, to return to Enrico Fermi, why hasn’t there been a nuclear terrorist attack or a series attempt at one? Why did al-Qaeda instead embark on the 9/11 plot, precisely at the time in history when access to fissile materials were most accessible to terrorists?

The Fermi Paradox applied to nuclear terrorism could be viewed as a reductio argument against the standard high probability paradigm. One or more of the three pillars might not be correct. What I will call in a forthcoming book on nuclear terrorism as the epistemic approach suggests that, at least, the first pillar of the standard argument is false. The construction of a nuclear weapon, even a gun-assembled bomb, is not as easy as it has been made out to be. That might be why we did not see nor have we seen a nuclear 9/11. There are no terrorist groups currently in existence with the required knowledge and expertise needed to mount an act of nuclear terrorism.

If that is so then even pillar three might need revision. An instrumentally rational terrorist group, faced with a high epistemic barrier, might give up on a nuclear terror plot. It would appear that is what happened in both the al-Qaeda and Aum Shinrikyo cases. That is, a terrorist group can be pre-disposed towards catastrophic terrorism but nonetheless be self-deterred by the enormity of the nuclear task.

Perhaps also, to argue even more strongly, al-Qaeda does not have the intention often ascribed to it. The study of nuclear terrorism is dominated by scholars of nuclear non proliferation, who display a peculiar brand of apolitical politics. In the literature fascinating discussions exist on the wonders of plutonium metal but little of the terrorists themselves. There is a good reason for this. Intention is simply ascribed.

To be sure a lot of the concern now seems to focus on extremist Islamist groups inheriting Pakistani nuclear weapons should the establishment lose control of the state.

But if realist international relations thinkers are right then even in this case there exists reason to downgrade our perception of risk. This is because pillar three need not necessarily apply. Upon inheriting the state, realists contend, revolutionary groups are more interested in consolidating their power and would become more circumscribed irrespective of ideology. This is because revolutionary states become socialised towards realpolitik out of concern for state security and survival. Pakistani nuclear weapons in this case would either be used to deter foreign intervention or to act as a shield to deter such intervention whilst providing conventional forms of assistance to fraternal groups.

Besides the Taliban is not al-Qaeda. The Taliban is concerned with its own region primarily rather than global jihad.

For Marc Sageman the globally based threat now consists of small highly decentralised cells for the most part disconnected from al-Qaeda central. Post 9/11 attacks tend to empirically support this view. These groups are amateurish. Many botch the manufacture of simple conventional bombs even though they have access to online cookbooks. Although this should not necessarily be cause for complacency.

It means that we must be more mindful of the issue of knowledge when discussing policy options and perceptions of risk. For example, the expansion of nuclear power will require the development of more nuclear science and engineering training programs that will increase the global pool of nuclear expertise. This includes mooted nuclear power programs in the Middle East, including Saudi Arabia.

Saudi Arabia might not construct enrichment or plutonium reprocessing plants, although the prospect is very much a live one. However, a Saudi nuclear power program will require much greater investment in the education of domestic nuclear scientists.

Perhaps the expansion of nuclear power will need to be managed carefully from an epistemic viewpoint. Of course, it need not necessarily be a bad thing from an epistemic perspective. Employment prospects for nuclear engineers appear promising, especially for Russian ones that previously have been of concern, although engineers do appear disproportionately as an occupation group within terrorist ranks.

The problem, of course, is that if a truly capable group were to emerge and if such a group acquired high grade nuclear materials then any terrorist nuclear attack might well reach a nominal yield. We should not thereby look at the epistemic or supply side approaches as being mutually exclusive.

Without the required knowledge nuclear materials cannot be fashioned into a nuclear device. This of course applies in reverse. Without the the Hanford plutonium production reactor or the uranium enrichment facilities the wizards of Los Alamos would not have manufactured an atomic bomb.

There are lots of things that we should be worried about. Nuclear terrorism ought not be one of them.