Nov 14, 2011

How many nuclear bombs would it take to destroy the Earth?

Let's start with pinup model Sabina Kelley.



The Helsinki International Film Festival was showing a movie about Grant Morrison, and the Finnish-language blurb mentions that Morrison "grew up in Scotland, near an army base holding enough nuclear missiles to destroy the world 50 times over".

I haven't seen the movie, and from the blurb I can't tell what "army base" they're talking about. Given that (as near as I can tell) neither V-bombers, British ballistic nuclear missiles nor US SAC aircraft were based in Scotland at the time, the most reasonable guess would be Faslane, a Royal Navy nuclear submarine basd.

In the late '60s, Faslane became home to the Royal Navy's four Resolution class ballistic missile submarines. They each carried 16 Polaris A3 missiles, each with three 200kt independently-targeted warheads. So, 48 warheads at 200 kilotons each makes 9.6 megatons per submarine, and 38.4 megatons of total destructive power.

In other words, the total nuclear destructive power housed in a single Resolute class submarine was less than the 50-megaton yield of the Tsar Bomba, or less than two SS-18 Mod 2 warheads. The four submarines combined carried 192 200kt warheads; hardly enough to destroy the entire world even once. In fact, I'd be surprised if they were even enough to destroy the entire surface of Scotland.

Scotland has a total land area of 78,772 km2; according to a quick back-of-the-envelope calculation, it would take approximately 250 one-megaton nuclear warheads to destroy it. So late 60's Faslane didn't even hold enough nuclear weapons to destroy Scotland completely, let alone the world.

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The notion that we have enough nuclear weapons to destroy the world several times over gets thrown around constantly, even at fairly high levels of government; last year, US Secretary of State Hillary Clinton said of the US and Russia that "We have more than enough nuclear weapons to destroy the world many times over".

Do they?

There's a beautiful series of infographics over at Information is Beautiful titled How I Learnt To Stop Worrying And Love The Bomb (Kinda), that nicely illustrate the answer. In a word, no. The total explosive yield of all the world's nuclear weapons isn't nearly enough to destroy the whole inhabited surface of the world, let alone the world, let alone several times over.

This isn't to say that a global nuclear war wouldn't have unimaginably disastrous consequences. A full-scale nuclear exchange between the US and the USSR at the height of the Cold War would have been an unparalleled planetary disaster, resulting not only in the direct deaths of millions, but in widespread radioactive fallout and, in all probability, a nuclear winter.

In my mind, the recent studies that suggest even a small-scale nuclear exchange could cause a global environmental catastrophe are suspect. The Second World War saw massive bombing campaigns that killed hundreds of thousands and incinerated huge swaths of urban areas, but caused no notable climate effects. A similar instance was the predicted disastrous consequences of the oil well fires in Kuwait following the first Gulf War, which also seemed to ignore the experience of the Second World War. I'm not at all convinced that a small-scale nuclear exchange would have decisively more catastrophic effects. It would still, at the very least, be a horrible disaster for the populations involved.

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To understand why nuclear weapons can't actually destroy the world, it's absolutely vital to understand several things about them. In my experience, it's these misconceptions that usually lead to a hugely inflated notion of their destructive capabilities.

Firstly, nuclear weapons effects do not increase geometrically with yield. For example, the atomic bomb dropped on Hiroshima had a yield of 13-18 kt. It destroyed buildings in a 1.6 kilometer radius. From this, it's often erroneously assumed that a 100kt weapon would have 5-10 times that effect, and a 1Mt weapon would have 50-100 times the area of effect. This is far from true; a 1Mt weapon would cause severe fire damage out to a radius of approximately 10km, and complete destruction of urban areas to a radius of 2.4km. That's a big bang, but far from 50-100 times the actual destruction caused by the Hiroshima bomb.

After the several megaton range, effects decrease even more sharply relative to the yield. The 50Mt Tsar Bomba caused total destruction out to a 35km radius, not the 500km that a simple calculation from one-megaton explosions would suggest.

This, by the way, is why it annoys me when nuclear bomb yields are described in "Hiroshimas", as in a bomb having so-and-so many times the force of the bomb dropped on Hiroshima. It gives a totally misleading picture of the effects of the bomb in question.

Secondly, for nuclear weapons to destroy the world, they'd have to be targeted at the whole world. In other words, to get the most destructive area out of our nuclear weapons, we'd have to target them in order to maximize the damaged area. But in a real nuclear war, the targeting priorities would be completely different. It's assumed that some missiles won't make it, so all important targets will be targeted by several missiles. If all the warheads make it, overkill will result, meaning that some of the warheads won't even detonate at all. So for starters, a whole bunch of destructive power will be lost to a variety of causes like mechanical malfunctions and overkill.

This targeting also means that the nuclear weapon effects will be concentrated in a fairly small list of targets. In a Soviet-US nuclear exchange, missile bases, airbases and other military facilities, as well as cities, would have received far more than their "share" of nuclear destruction. So calculating the total area of the world our nuclear weapons could potentially damage is a totally theoretical number, since there is no plausible scenario in which nuclear weapons would be used for maximum area effect. That would require targeting a nation's nuclear arsenal all over the world, which, even in the context of full-scale nuclear war, would be completely insane. Nuclear warfighting plans have detailed, thought-out strategies for using nuclear weapons; they don't just say "press button - destroy world".

Even if we tried, we couldn't even destroy the total inhabited surface area of the world; and we're not even trying.

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The idea that we have enough nuclear weapons to destroy the world several times over is totally false. We don't. It's remotely possible that if we put our minds to it, i.e. combined the total nuclear arsenals of the world and made a concerted effort to use them to destroy human life, we might be able to kill everyone. Then again, if we persuaded everyone to walk off a cliff, that would do it as well.

Nuclear weapons are dangerous and frightening in their own right; there's no need to concoct these ridiculous "enough nukes to destroy the world 50 times over" myths to prove it.

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