Doomsday debated

Eliot Gelwan in his blog Follow Me Here posted a piece, entitled “They're just lying, I'm sorry to say,” which links to Impearls' depleted uranium article (permalink), calling it “A pretty damning indictment of concerns from the left over depleted uranium weapons, if you can believe the science cited here, well-documented and footnoted.”

In that same posting, however, Gelwan goes on to link to and criticize Impearls' subsequent piece on Doomsday (permalink), writing:

McNeil […] scoffs at the idea that a nuclear holocaust would mean doomsday for the human race, with a much more selective appraisal of the evidence [than in the depleted-uranium article], clearly in the service of his ideological biases.

I initially posted a reply as a comment on Eliot's blog, to wit:

Speaking as the person targeted by these comments, no doubt I do have ideological biases; however, I do not believe the idea that nuclear arsenals as they existed during the cold war and today were/are insufficient to trigger human extinction is very controversial.  Notice that renowned physicist Freeman Dyson in his reply had no criticism to my comments in this regard.

Moreover, I have no doubt, as I clearly expressed in that piece, that human extinction could be caused by means such as “gigaton mines” or similar, relatively cheap device — a Doomsday Machine — deliberately designed to accomplish that goal.  It could do this perhaps by, among other things, shattering the earth's crust and releasing huge volcanic eruptions, surpassing even the geologic “Deccan trap“ occurring around the time of the demise of the dinosaurs.

Soon after, Gelwan replied again, in his comments, which I'll quote in full:

I have concerns about your confidence.  The human track record for anticipating the full range of cascading, immensely complex sequelae from our acts of violence against the ecosphere is not very good.  Inherently, one can easily underestimate but it is difficult to overestimate, since we continually demonstrate we know so little about the consequences of our actions.

And, for every esteemed Freeman Dyson (to whom, I might add, the question does not appear to have been put directly; you infer his assent from the fact that he had no criticism) there have been perhaps fifty scientists who have actually worked on nuclear weapons development and related fields who disagree.  This is what, for example, the Union of Concerned Scientists were concerned about.  This is what the Bulletin of the Atomic Scientists issues bulletins about.  Should I anticipate your dismissing all their concerns because they are leftists?

One way to do risk assessment is to weigh possible outcomes by, roughly, the product of likelihood × severity.  Likelihood alone is not a sufficient basis for planning to meet risks.  Even if I agreed with your low likelihood estimation (and I do not), in and of itself it is not a sufficient basis to reassure thoughtful people about the doomsday risks.

I don't want to get into a flame war with you; this is a little like arguing about religion.  We'll have to agree to disagree on most things.  If the contemptible Bush administration has its way in reversing the progress the world has made toward abolishing the risks of nuclear annihilation, you're right, I probably won't see you On the Beach, but I probably will in Nuclear Winter.  Thoughtful people should be questioning questionable assumptions and pat reassurances on this issue, especially when they arise from a partisan ideological agenda, as if their life depended on it.  It does.

Eliot says he has “concerns about your confidence.”  My “confidence,” as he calls it, my “scoff[ing] at the idea” as he characterized it in his earlier posting, consisted of my saying I considered it “unlikely” present or cold war-level nuclear arsenals would instigate human extinction — I then went on to discuss potential ways the arms race might have proceeded which could, had things developed differently, have triggered Doomsday.  This is hardly scoffing at the very idea or danger of Doomsday, as he implies, quite the contrary.  Moreover, my piece describes the extreme effects even a non human-extinctifying (to coin a term) cold war-era nuclear exchange would certainly have had for the participant nations, going on to quote Freeman Dyson that “nuclear war means death” and “it is a truth which we must never forget.”  Getting from there to the conclusion that I'm minimizing the risks from nuclear war is a monumental non sequitur, in my opinion, and Gelwan's comments display a sizable “ideological bias” (to pick up a deprecating term he tosses around) of his own — not to speak of that exhibited in the last paragraph!

Gelwan proceeds with this breathtaking prose:  “The human track record for anticipating […] is not very good.  Inherently, one can easily underestimate but it is difficult to overestimate […].”  On the contrary, it is environmentalist disaster predictions which have failed miserably (fortunately for us all) over the last several decades in living up to their expectations.  While I agree in principle with the first part of Eliot's statement, the converse is also true: environmentalists' records in anticipating, e.g., the manifold, interlocking strengths of the ecosystem, or the technological dynamic in the search for mineral resources (finding new sources even as known reserves are depleted), etc., etc., are also quite poor.  Given the disposition among environmental activists to keep the rubes ignorant (as Gelwan baldly says, “in and of itself it [truth] is not a sufficient basis to reassure thoughtful people about the doomsday risks”), as well as environmentalists' inclination to listen only to each other's (given the previous point, what ends up being) spin, in my view guarantees overestimating the risks.

Eliot wonders what Freeman Dyson's views are with regard to the extinctifying potential of present or cold war nuclear arsenals.  In his book Weapons and Hope (1984), Dyson wrote:  “I am unable to imagine any chain of events by which our existing nuclear weapons could destroy mankind and leave no remnant population of surviviors.”  Gelwan imagines that fifty times as many physical scientists would agree with him as Dyson in this regard.  In my view that's a ridiculous assertion; I believe the actual ratio for physicists would be well in the reverse direction, but that's neither here nor there — being a nuclear scientist doesn't give one special expertise or aptitude for predicting most environmental “sequelae,” as Gelwan terms them, to nuclear war.  As for Gelwan's attempted put-down of Dyson, implying he never “actually worked on nuclear weapons development and related fields,” on the contrary Freeman Dyson was one of the principal actors in the Orion spaceship project.  Eliot might recall what was to propel Orion: mini-atomic bombs.

Getting back to Doomsday, the real danger, I think — and Dyson agrees, or rather I agree with him in this regard (see Weapons and Hope, pp. 22-23) — is not that a nuclear exchange say between Pakistan and India, or even between Russia (or the old Soviet Union) and the United States, would trigger subsequent human extinction.  The danger, Dyson writes, is that we would survive an initial nuclear exchange; but decide, more or less, hey that's not so bad, we can take this… then go on to fight more nuclear wars, exchange after exchange, waged upon an ever increasingly poisoned and dessicated earth — until ultimately human extinction would follow.

That's why it is so important that even a limited nuclear exchange (such as possible between India and Pakistan, clearly short of Doomsday) must not be undertaken in the first place.  Trying, as Gelwan seeks to and “atomic scientists” at Bulletin of the Atomic Scientists do, to scare thoughtful people by suggesting that Doomsday is plausible in such a scenario will simply shred further the already much-tattered reputation of environmentalist “doomsday-mongers.”

As for how reasonable it is to suppose even a cold war-level nuclear arsenal would be capable of instigating human extinction, let's do a little sanity check.  The total size of the nuclear arsenal as it existed during the cold war may be estimated at about a gigaton; that's close enough, a factor of a couple either way wouldn't make any difference to the discussion.  The explosive power of a ton of TNT is equivalent to 4.184 × 10⁹ Joules of energy.  A gigaton of TNT therefore contains 4 × 10¹⁸ Joules.  According to this 1997 article in the journal Nature (requires subscription or pay-per-view), the impact which created the Chicxulub crater on the northern tip of the Yucatan peninsula of Mexico 65 million years ago (exterminating the dinosaurs along with three quarters of all species alive, land and sea, killing all creatures larger than about 10 kg or 22 lbs. body weight, which included all the dinosaurs) had an energy of 5 × 10²³ Joules.  Thus the Chicxulub impact — triggering the only known “nuclear winter” during the last more than hundred million years on earth — had an energy over 100,000 times greater than the cold war nuclear arsenal.  How likely is it then a “mere” gigaton (comparable to a magnitude 8 earthquake, which occurs every few years) could accomplish it?

No, I suggest the real danger lies as laid out above: that nuclear war might “catch on” as both nationally survivable (at least when taken in moderation, like fugu) and politically advantageous.