Editorial Note: I first had the following article published nearly a decade ago in a specialist, safety-engineering journal. It has been reproduced here since it provides a useful technical background for my recent post, The Games People Play. It may be read as an addendum, or as an article in its own right. Either way, it serves to place the scale of risk posed by climate change in its proper context. Let us now take a look at what a real existential risk looks like:


On the Safest Way to Kill

 “The fascination of shooting as a sport depends almost wholly on whether you are at the right or wrong end of the gun.”

P.G. Wodehouse, The Adventures of Sally

I like to think that business is very much like hunting. Basically, people hotly pursue their goals, and there are those who will benefit from the pursuit and others who will… well, maybe not so much. To capture this idea, organisations like to talk of differing stakeholders, which is just a lofty way of saying that not everyone shares the same goals and concerns.

Stakeholding can make the construction of a safety case very interesting (if not to say contentious) since one person’s safety can often set the scene for another’s downfall. Nowhere is this contrast as stark as it is for nuclear weaponry. When nuclear weapons work safely, people are still allowed to die in their millions. Yet an unsafe weapon might only kill a handful of people, albeit an unintended handful – for example, a maintenance team could be killed by faulty detonators. Worse still, your warhead may fail to go off altogether, thereby allowing the enemy a greater opportunity to kill millions. And, of course, we are talking about the wrong millions here.

Military analysts refer to the concept of Always/Never, which means that a weapon must always fire when required but never fire when not required. Consequently, if safety devices are to be applied, they cannot be allowed to compromise the mission – the weapon bearer’s stakeholding must be protected under all circumstances. This uneasy balance between the demands of both mission and safety is central to the development of the world’s nuclear arsenal, and it is a good reason why you shouldn’t sleep too easily tonight.

How Safe do Nuclear Weapons Have to be?

Before I question too deeply the logic of developing a safety case that permits mass destruction, I need to consider the level of risk that can be tolerated on behalf of the population you claim to be protecting.

The first attempt to answer this question was made by the United States Army in 1955. They calculated how many fatalities had resulted from floods, earthquakes and other natural disasters in the preceding fifty years and used this as the target mortality rate for nuclear accidents. From this they calculated that the acceptable odds for an atomic (fission) weapon to explode accidentally on U.S. soil should be 1 in 250 during the course of a year. The same target equated to a 1 in 100,000 chance for thermonuclear weapons. Remember, we are talking about accidental American deaths here. Determining the acceptable number of communist deaths required quite a different calculation.

In 1957 an organisation known as the Armed Forces Special Weapons Project revisited the question and concluded that there should be no more than a one in five chance of an accidental thermonuclear detonation within a given decade. The same organisation condoned the virtual certainty of a fission weapon accidentally detonating within the same timescale. This was the military viewpoint. One can imagine that civilians would come up with a different answer.

Since those early days, nuclear weaponry has seen many changes. Furthermore, the social and political backdrops have evolved. Consequently, the safety standards required for nuclear weapons have undergone significant reassessment. The latest statement on the subject (chapter 2 of US Defense Standard DoD 31 50.2-M, 1996) states that the probability that a nuclear warhead might accidentally detonate, whilst in normal storage and operational conditions, shall not exceed one in a billion per warhead lifetime. However, this target drops to one in a million for abnormal environments such as those resulting from fires. Keep in mind that this limit is per warhead, so a goodly stockpile will increase the risk significantly. It seems, even now, no one expects nuclear weapons to be entirely safe, and many expert authorities fear that an accidental or unauthorised detonation is still only a matter of time.

So How Safe Are They?

Or more to the point, should one really expect a straight answer to this question? For example, when it was proposed that Strategic Air Command bombers should carry live nuclear bombs as part of a permanent airborne readiness, President Eisenhower was advised that the chances that any aviation accident could result in a nuclear explosion were, “essentially zero”. In truth, zero was the only probability that could be confidently ruled out. And given that B52 bombers were, at that time, crashing once in about every 20,000 flying hours, the real prospects of avoiding a very bad day at the Oval Office were not nearly as good as Mr President thought.

So, I won’t insult your intelligence by plying you with ‘official’ facts and figures. Nevertheless, a survey of things that might go wrong can still be illuminating.1 Firstly, I’ll address questions of physical vulnerability, then I will take a quick look at failures of command and control. As I do so, I will discuss safeguards and the ever-present conflict between the pursuit of both safety and mission objectives.

Wooden Bombs

In the earliest days of atomic weapons, the risk that a bomb might accidentally detonate was minimised by delaying final assembly until the point of deployment.2 Prior to that point, the fissile component would be stored separately from the high explosive components used to detonate it. Whilst this arrangement improved the safety margins in storage, it was bad news as far as operational readiness was concerned. Furthermore, the weapons were difficult to maintain and very bulky and heavy. Weapons development therefore focused upon creating relatively lightweight3, preassembled bombs that could be safely stored at dispersed sites and then loaded and primed within minutes – so-called “wooden bombs”, sat inertly on the shelf awaiting use. Since such weapons would have their fissile core confined within a solid metal casing, they were said to have a sealed pit.

One Point Safety

The resulting weapons were smaller and more powerful but had the disadvantage of being ready to bang if subjected to physical trauma, as in a bullet strike or a fire. Consequently, they were required to be “one point safe”. This decreed that detonation at a single point within a bomb’s high explosive system (used to implode the fissile core) shall not result in a nuclear explosion.4 Furthermore, any non-nuclear explosion’s yield should not exceed the equivalent of four pounds of TNT (in consideration of the damage that a non-nuclear explosion can still cause on a ship). Notwithstanding these arrangements, the behaviour of high explosives under abnormal conditions, such as in a fuel fire, is sufficiently uncertain as to warrant extreme caution when dealing with such conditions. Each make of bomb had a “time factor”, typically only a few minutes, after which every firefighter and their dog was advised to run to the hills.

More Things to Worry About

Irrespective of one point safety, two serious concerns remained to preoccupy the safety conscious combatant:

Firstly, a non-nuclear explosion may still result in the dispersal of highly radioactive material. And if this happens to be plutonium, you are dealing with a very serious risk indeed, since plutonium contaminated dust can be easily inhaled to deadly effect. Worse still, plutonium has a half-life of about 24,000 years, so any contamination is likely to outstay its welcome.

Secondly, early sealed pit weapons ran the risk of accidental detonation caused by a rogue firing-signal. This could result from a maintenance accident, a lightning strike or a fire. To counter this risk, a trajectory sensing switch was developed, whereby the firing mechanism would only become operational following weapons launch or release. Prior to that point, it should be physically impossible for current to flow to the detonators. But Mother Nature is ingenious, so no mechanism is guaranteed to carry zero risk.5 And the harder you try to reduce the risk of accidental fusing, the more likely you are to end up with a dud when you press the button. The military have good reason to worry about this. A safety device added to Polaris missiles was later found to be subject to corrosion, rendering the missile dud. In fact, a 1963 routine maintenance check discovered that at least 75% of the Polaris fleet’s missiles were destined to disappoint.

If in Doubt, Build More Bombs

Perversely, the early development of safety mechanisms was to make the world less safe. Concerned that a good many of their weapons might now be of the “Never/Never” persuasion, the military compensated by increasing the nuclear stockpile, with the intention of hitting any given target with many and varied warheads. This clearly increases the risk that a full-scale nuclear conflict might be instigated in error, making that of a single, accidental detonation appear quite attractive in comparison. So this is probably a good time to discuss how a nuclear contretemps could happen and how it may be avoided.

The Importance of Self-control

First and foremost, protection6 from nuclear attack requires that one possesses an early warning system that is both effective and trustworthy. Consequently, any indication of an incoming attack must be properly evaluated before a response may be decided. However, the checks and balances required to avoid responding to a false alarm inevitably take up valuable time, and the “use it or lose it” principle is bound to influence deliberations. Clearly, therefore, the risk of hastily responding to a false alarm has to be suitably balanced with that of failing to respond in a timely fashion. The good news is that the military are able to practise their response using computer-simulated attack and so, presumably, have tested their procedures to remove any inefficiencies. The not so good news is that in 1979 someone in the North American Aerospace Defense Command loaded a training tape onto a computer without anyone realising and, in so doing, very nearly precipitated World War Three. Catastrophe was averted only because surveillance satellites failed to provide corroborating evidence of an attack. Other close calls have resulted from mistaking a scientific rocket for an ICBM, a faulty computer chip, sunlight reflected from high-altitude clouds, and mistaking the moon for an incoming salvo of ICBMs.

As a further concern, one of your nuclear weapons may fall into the wrong hands, and there is always the chance that one of your own personnel may not be on message. Consequently, controls and arrangements that help avoid an unauthorised launch7 are essential. These include: Permissive Action Links (PALs), i.e. devices that require a coded input to enable a device’s firing mechanism; centrally-controlled code management; dual key arrangements, with mutual monitoring of potentially rogue behaviour; secure and reliable communications for authorisation and confirmatory dialogues; effective security protection for arsenals and armed delivery systems; and appropriate psychological profiling and selection of personnel. I could go on, but I doubt if I could convince you that the arrangements amount to a fool-proof system. As long as battle readiness remains a priority, the Devil will always find a way.8

From Stakeholder Management to Holocaust

The development of nuclear weaponry provides a prime example of the efforts required to meet the Always/Never challenge. However, war is what happens when stakeholder management gets out of hand, so it is no surprise that, in the battlefield, Always/Never makes sense only when seen from the appropriate stakeholder perspective. Not only are safety and mission efficiency arrangements often at odds with each other, a successful balance between them is likely to maximise the death toll, once the slaughter of all stakeholders has been taken into account. Safety arguments can look very odd when reliability equates to lethality, since the concepts of the right people to kill and the right circumstances in which to kill have a very shaky ethical foundation.

Finally, it’s not as if stakeholder conflict is unique to military systems. Even in civilian applications, your stakeholder management obligations may lead you to make some morally dubious decisions. For example, what price public safety if it requires that the lives of the emergency services be placed at risk? The bottom line is that if you ever find yourself constructing a safety argument and asking yourself, “What would Jesus do?”, you might want to consider getting another job.


[1] In this article I do not attempt a quantitative assessment of the safety risk. However, those who are interested may wish to consult On the Risk of an Accidental or Unauthorised Nuclear Detonation – RM-2251 U.S. Air Force Project Rand (1958), in which Bayesian techniques are used to assess probabilities based upon “accident opportunities” and their incident rates.

[2] So, for example, an airborne weapon’s nuclear core would only be inserted after take-off. To further reduce the risk, nuclear missions were not to be flown from U.S. bases. Instead, expendable airfields such as those in Norfolk, England were to be used. As far as the U.S. government was concerned, the good people of Norwich were the wrong kind of stakeholders.

[3] The weight and size reduction was principally achieved by using solid electrolytes to provide the power to activate the warhead, rather than relatively heavy, liquid electrolytes. In addition, a tritium and deuterium gas was used to boost the weapon’s yield, whilst enabling the reduction of fissile material. Note that the fission boost is provided by extra neutrons produced following fusion of the lithium and deuterium. However, the energy released by the fusion does not itself significantly contribute directly to the yield, so the weapons are still basically fission devices.

[4] One way to ensure this is to design the bomb’s core so that, notwithstanding its implosion, reaching criticality still requires the boost neutrons that are released following fusion of the surrounding lithium and deuterium gas. The mechanism that activates this fusion is independent of that which detonates the high explosives. Consequently, an accidental activation of the high explosive implosion system will always be insufficient, on its own, to instigate a nuclear reaction.

[5] For example, short circuits can result from melted solder, charred plastic or from arcing between newly proximate wiring. Errant currents might then energise the firing mechanism. Such risks are minimised by isolating the firing mechanism within a physical barrier and then using so-called ‘strong links’ to connect to external components. ‘Weak links’ within the isolated section are then designed to predictably fail ‘open’ in abnormal environmental conditions, long before the strong links have chance to fail in a potentially unpredictable fashion.

[6] By ‘protection’, I mean ensuring that your nation’s imminent destruction shall not go unnoticed.

[7] The U.S. terminology for nuclear mishaps is provided by DoD Directive 5230.16. Apparently, an unauthorised launch of an ICBM, resulting in detonation, is an example of a so-called ‘NUCFLASH’.  I wonder how long it took them to come up with that one.

[8] It has been alleged that, to expedite launch procedures, the security code required to activate the Minuteman missile was set to ‘00000000’ in all silos.

Further Reading:

Command and Control’, E. Schlosser (ISBN 978 0 141 03791 2).

Atomic Accidents – A History of Nuclear Meltdowns and Accidents’, J. Mahaffey (ISBN 978-1 60598-68-7).

Analysing and Reducing the Risks of Inadvertent Nuclear War Between the United States and Russia’, A. M. Barrett et al, 2013.


  1. For the benefit of those very few of you who will be interested enough in the technicalities of nuclear weapon safety to have read the above article, I think I should point out that footnote 2 misrepresents the facts. Since writing it, I have come to realise that the real reason for basing the nuclear bombers in the UK had nothing at all to do with risk reduction and everything to do with limited range.

    Liked by 1 person

  2. That’s probably one of the most enjoyable articles ever written about accidental nuclear holocausts. More, please. (Not necessarily about nuclear holocausts. Do you have anything about, say, antibiotic resistance?)


    Veering very sharply sideways from ‘What would Jesus do?’…

    In July 2008 a Christian group in Newcastle, NSW, met to answer the question ‘Would Jesus Burn Coal?’

    A PDF-ed flyer:


    Newcastle’s economy is built on coal. Indeed that’s why it’s called Newcastle.

    So what did the 2008 meeting decide? I strongly suspect that the answer was ‘No’ but haven’t been able to find anything about what was said. This…


    …alludes to the meeting (the writer and John the BaptistJono were its main speakers) but doesn’t give any details.

    I’d love to know more.


    Liked by 1 person

  3. Thanks Vinny. I’m pleased that at least one person liked it. I was acutely aware that this article is little more than a lengthy footnote to the previous one, and not everyone reads footnotes. If it had been available online, I could have just provided a link. As a post, it is a bit off topic.

    Antibiotic resistance would be another off topic, but a fascinating one. So I might very well take you up on your challenge.

    Liked by 1 person

  4. Here’s a thought.

    Is it possible to quantify the risk of nuclear conflagration? Leaving aside the masses and masses of daily propaganda, is it actually possible to quantify the risk of “catastrophic climate change”? If so, which is more likely, and how many people would be adversely affected by each?

    I’m sticking my neck out here, but I’m fairly satisfied that nuclear annihilation is a greater risk to humanity than climate change (whatever George Monbiot may think). I wonder how many school hours are dedicated to the risks of nuclear annihilation -v- the risks of climate change?

    I suspect we know the answer, and that the answer doesn’t make a lot of sense.

    I can’t remember the last time any of the mainstream media had an article or programme worrying about nuclear war. I can remember the last time they had something worrying to say about climate change – dozens of pieces every day, including today. Why the lack of logic here, I wonder? We can’t realistically do anything about either threat, after all.

    Liked by 2 people

  5. There was an article I think in the Observer, I think about a decade or two ago, about a fire at an RAF base in Norfolk back in the sixties. (All US nuclear bomber bases in Britain have “Royal Air Force” written over the entrance, and a chap in a British uniform with a twirly moustache standing at the gate.) An eyewitness was quoted who’d been driving towards the base, and was met by a huge convoy of trucks and cars coming the other way. One stopped and the witness asked the driver where they were going. “Anywhere,” was the answer “As far as possible.” The fire was presumably successfully put out and no harm done. No-one told the people of Norfolk of course.

    Liked by 2 people

  6. US nuclear submarines are still based at Faslane near Glasgow, I believe. Elements of the Scottish Nationalist Party around ex-leader Alex Salmond would like to chuck them out and lift the threat of nuclear annihilation from the citizens of Glasgow. When Salmond attempted a political comeback, elements of the SNP around the current leadership tried to send him to prison on false charges of rape and sexual assault. When Craig Murray, https://www.craigmurray.org.uk ex-ambassador sacked for objecting to the use of torture, reported Salmond’s defence case in detail, he was charged and found guilty of complicated contempt of court offences, and is currently facing a jail sentence. It’s one of the problems of nuclear deterrerence that it’s very difficult to defend, in more senses than one.

    When my daughter was demonstrating outside Faslane, one of her colleagues said to her: “See that tent? I was born in that tent.” Wouldn’t it be nice if in twenty years time, someone said of us: “See that blog? I was born on that blog.”


  7. John. I complement you on your ability to sprinkle your most worrying text with goblets of humour. Was this an attempt of your rational mind to contemplate the irrational? Was all this analysis that you outline completely novel or had it precursors- gas attacks during the First World War perhaps?


  8. “I was born on that blog”

    Yes, Geoff, and if the viewing figures for this post are anything to go by, I am dying on it as well 🙂

    Liked by 1 person

  9. Alan,

    A lot of my information came from the Mahaffey book listed under References. It is also from that author that I stole the style. His book is full of dry wit and gallows humour. I thought it was very effective and so committed to trying it for myself.


    I am not ignoring you. It’s just that my answer will require far too much mental effort for a Sunday morning. I will get back to you, however.

    Liked by 1 person

  10. Oh, and since you mention First World War gas attacks, Alan, that certainly was a weapon that posed a particularly difficult stakeholder management challenge.

    Liked by 1 person

  11. JOHN
    Viewing figures look ok for a Sunday morning, particularly as people have other things to think about on this, the Day of Days. If you like I’ll put a link up at ARRSE, the Army discussion forum. They were very into us at one time.

    My sole regret is that we lose valued commenters like Tiny CO2 when we drift off-topic and try to survey the bigger picture. On the other hand, we manage to discuss civilly matters of high import, despite often having diametrically opposed political opinions, which makes us unique among blogs. And being unique sometimes means standing alone.

    Liked by 2 people

  12. Mark,

    To answer your question:

    Firstly, it is very difficult to make quantitative comparisons between the relative risks because each risk is difficult to quantify and one would not be comparing like with like. In the case of nuclear war, one is dealing with well-defined events and the probability of their occurrence (e.g. nuclear accidents, deliberate acts, etc.). With climate change one is dealing with a range of ill-defined future scenarios, and no one wants to even admit to calling them predictions. In fact, half of the time, the fact that the climate risks cannot be quantified seems to be the clarion call for action (as in Lewandowsky’s ‘actionable uncertainty’). However, one thing can be said: No one, other than the vast majority of activists, is claiming that climate change is destined to wipe out all human life. An argument for hardship and loss may be made, but adaptation and mitigation should ensure that the risks are bounded. The same cannot be said for nuclear conflagration. If risk is a function of probability and impact, and the probabilities are considered equally unquantifiable, then the nuclear war risk wins hands down.

    That said, the future probabilities and impacts of extreme weather events are now the subject of serious efforts to quantify, as in D&A. These calculations are subject, of course, to the systemic uncertainties within the computer models upon which they are based.

    Efforts have also been made to quantify nuclear risk, although one should expect the vast majority to be subject to military censorship. The first effort, performed by RAND in the 1950s took a Bayesian approach. It took 40 years to be made public, albeit still in a highly redacted form. It’s results are well out of date now. Another attempt is cited in my article (Barrett 2013) and a more recent effort can be found here:


    You will note that all such efforts are hampered by one brute fact: You can’t just count the number of nuclear wars that have happened in the past and divide by the time period. The remarkable thing is that we have not had a nuclear conflagration yet. We seem to be truly pushing our luck.

    Liked by 3 people

  13. Very interesting piece. You’re on fire these days 🙂

    Until relatively recently, and indeed still not quite there yet in all respects, Western military aviation was exempt from Flight Cert rules for the manufacture / maintenance / operation of all their aircraft. This reduced costs enormously, and tended to be justified by pretty loose arguments that war is dangerous anyhow and military personnel (pilots) are more expendable (albeit not put so bluntly). However, military flights share civilian airspace and indeed fly over civilians all the time, whether or not the airspace has commercial flights in it too. Hence the public has always been exposed to increased risk from aircraft aligned to much less robust standards, and it had occurred to me a long while back that this included aircraft carrying nuclear bombs (I presume that’s an obsolete delivery method now). Maybe why the B52s crashed so often. This is actually true also of all missiles, whatever the warhead, and there’s been much proliferation of these as a main weapon in most theatres in recent times (though most are short-range). While Western militaries have been dragged reluctantly into the Cert domain (not only because of much more crowded air-space and higher density / more civilian populations, but via the provision of commercial-off-the-shelf flight-certified components that reduce costs, which I was involved with), the majority of equipment still likely to be in the air now stems from older times before the standards were accepted. Sizeable drones, e.g. carrying bombs or other serious arms, being a much newer thing, do tend to be flight-certified.

    Liked by 2 people

  14. John: “No one, other than the vast majority of activists, is claiming that climate change is destined to wipe out all human life.”

    This is the nub of everything that’s happening. In practice, it is far more than just ‘activists’; most authorities the world over (with the notable exception of Trump as was) have been emotively captured by, and propagate, this narrative in various forms. As do large swathes of national publics (the % depends upon which nation) across the globe who nevertheless can’t be described as activists. And despite that the great majority of them (again, the fraction depends on nation) would no way stand behind this narrative when it comes to a clash with other realities, other important issues. The great bulk of them are not lying when they propagate, they’re simply *believing*. But this still comes across as a legitimate ‘claim’, especially from authority (e.g. presidents, prime ministers, high ministers, church leaders, UN leadership, economists, influencers, celebs, local politicians, businesses, royalty, the academy, etc.) Of course the claim is completely unfounded in mainstream (and sceptical) science, but this is no impediment to its public dominance.

    Liked by 2 people

  15. Andy,

    To be fair, I wrote this piece many years ago for a very different audience, and I repeated here only because it seemed an appropriate footnote to my last Cliscep offering. Besides which, in that last post I boasted that I had looked into nuclear arms safety, and I thought it might be a good idea to back that claim up. At the end of the day, this is all vanity really. 🙂

    To take up your point regarding aviation certification, I might add that nuclear weaponry is now subject to far more stringent quality control and safety regulations than it used to be. Thanks to the design innovations of people like Bob Peurifoy, modern weaponry is substantially safer than it was in the early days of the Cold War – thank God!

    Liked by 2 people

  16. A 3-part drama about antibiotic resistance starts on Radio 4 Extra tonight:


    It’s by Val McDermid. I’m not a big McDermid fan but that one might be worth a listen. At 1.5 speed, anyway. Or perhaps 2.0.


  17. Casting around on the internet, there is no shortage of people opining that climate change poses a greater threat than nuclear war. There is a lot of arm waving and apocalyptic rhetoric, but no one seems to be prepared to perform a quantified risk assessment to back up the claim with data. Here are just three examples:




    I’ll grant you that you will also find plenty of articles reminding of the threat of nuclear war, but most do so only to bolster the claim for climate activism, since climate change is deemed to be the most likely cause of future nuclear conflict.


  18. I’ve found this interesting piece, demonstrating that not everyone is heralding climate change as the new kid on the block to usurp the risk of nuclear war.


    After opening with the obligatory statement of fealty to the lords of climate fear, the article quickly reveals its true intent:

    “The world faces two existential threats: climate change, and nuclear Armageddon. Action on both is required urgently. Tackling the first will impose significant economic costs and lifestyle adjustments, while tackling the second will bring economic benefits without any lifestyle implications. Those who reject the first are derided as denialists; those dismissive of the second are praised as realists…The uncomfortable reality is that nuclear peace has been upheld, owing as much to good luck as to sound stewardship. Because we have learned to live with nuclear weapons for 66 years, we have become desensitized to the gravity and immediacy of the threat.”

    Liked by 3 people

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