Nuclear Winter

In Let’s End the Peril of a Nuclear Winter, Alan Robock and Owen Toon argue that America should unilaterally reduce its nuclear arsenal from around 7,000 weapons to 1,000. Their argument, however well-intentioned, has serious weaknesses. One fundamental problem is that they fail to show how it follows from the desirability of greatly reducing the number nuclear weapons on the planet that unilateral reduction is wise.

They write that

These weapons have not been a deterrent to war or aggression. But even if you think they can be, how many would you have to use? The answer is, probably one.

That nuclear weapons have not deterred war should not be taken for granted. In Evaluating the Nuclear Peace Hypothesis, Robert Rauchhause wrote:

From the early days of the nuclear revolution, proponents of nuclear deterrence have argued that atomic weapons have the capacity to reduce the probability of conventional war (Brodie 1946; 1947). Reflecting on the Cold War, some scholars argue that this is indeed what happened: despite dozens of crises and several proxy wars, the United States and USSR avoided a direct military conflict because each feared that matters might escalate to nuclear war (Gaddis 1986, 1987; Waltz 1990, 1993, 2000). Unlike conventional deterrence in previous eras, nuclear deterrence is extremely robust because even irrational or unintelligent leaders are likely to recognize the exceedingly high cost of nuclear war. Thus, proponents of nuclear deterrence claim with a high degree of confidence that “the probability of major war among states having nuclear weapons approaches zero” (Waltz 1990, 740).
- Robert Rauchhause, Evaluating the Nuclear Peace Hypothesis: A Quantitative Approach, The Journal of Conflict Resolution, April 2009 vol. 53 no. 2 258-277

One conclusion of Rauchhause's study was that

when there is symmetry and both states possess nuclear weapons, then the odds of war precipitously drop.
- Rachhause, ibid. (from the abstract)

So not only does it seem intuitively reasonable that the threat of mutually assured destruction might deter war between the superpowers, there appears to be empirical evidence of such deterrence.

Having claimed that nuclear weapons have not been a deterrent to war, Robock and Toon proceed to assert that if they were a deterrent, one would suffice for deterrence. If you think the thousands on hand now do not deter, why assume that if they do in fact deter, a single nuclear weapon would deter as well? Again, no justification is offered, a serious lack given that on the face of it, if America had just one nuclear weapon against the Russian arsenal of thousands, that one might not provide a credible deterrent. How would it prevent the Russians from threatening to attack, and if America did not give in, actually attacking (perhaps after evacuating Moscow and Leningrad)?

Robock and Toon describe the possibility of nuclear winter as follows:

... the research into the destructive potential of a war involving nuclear weapons has continued.
Even with the reduced nuclear arsenals that the United States and Russia agreed to in 2010, we have the ability not only to set off instantaneous destruction, but also to push global temperatures below freezing, even in summer. Crops would die and starvation could kill most of humanity.

But it is not just the superpowers that threaten the planet.

A nuclear war between any two countries using 100 Hiroshima-size atom bombs, less than half of the combined arsenals of India and Pakistan, could produce climate change unseen in recorded human history. ...

More modern and advanced climate modeling has confirmed the initial findings and shown that the effects would last for more than a decade. The reason is that smoke from nuclear conflagrations would rise as high as 25 miles into the atmosphere, where it would be protected from rain and take at least 10 years to dissipate.

In more recent research, we looked at the potential impact of a nuclear war between India and Pakistan, with each country detonating 50 Hiroshima-size bombs. These explosions would produce so much smoke that temperatures would plunge, shortening growing seasons and threatening the global food supply.
Our calculations, based on how crops grow in different weather, showed that wheat, rice, corn and soybean production could be reduced by 10 percent to 40 percent overall for five years.
- Alan Robock and Owen Toon, Let’s End the Peril of a Nuclear Winter", NYT, Feb. 11, 2016

Robock and Toon ignore the possibility that such consequences of using nuclear weapons, however horrible, might offer the best hope for avoiding far more disastrous effects of unchecked global warming. The human race shows little sign of being sufficiently wise and mature to make the extreme changes needed to control escalating climate change. Though almost no one wants to face up to it, the fact is that if we prove incapable of radically reducing greenhouse gas emissions, the most effective means we know of to put a stop to catastrophic warming is a relatively mild nuclear winter such as might result from nuclear war between India and Pakistan. Not only would such a war result in significant cooling, resulting crop failures and starvation would likely bring about a substantial reduction in the planet's population (the incessant growth of which is another problem we have failed to control). The result might be a sustainable population, with greenhouse gas emissions reduced to an acceptable level. Obviously this would not be the ideal way to stop global warming, but if no other solution can be achieved, it might be better than the alternative.

Clyde Haberman's Global Warming Gives Science Behind Nuclear Winter a New Purpose (NYT, April 3, 2016) and the accompanying video provide an introduction to the history of thinking about nuclear winter and a brief discussion of the possibility that nuclear winter (or related geo-engineering) might counteract global warming.

For a 2007 analysis of nuclear winter effects, see Robock, Oman, and Stenchikov, Nuclear winter revisited with a modern climate model and currentnuclear arsenals: Still catastrophic consequences, Journal of Geophysical Research, Vol. 112, 2007

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