But nuclear explosions are also extremely likely to ignite fires over a large area, which coalesce and inject large volumes of soot and debris into the stratosphere. In the India-Pakistan scenario, up to 6.5m tonnes of soot could be thrown up into the upper atmosphere, blocking out the sun and causing a significant drop in average surface temperature and precipitation across the globe, with effects that could last for more than a decade.
This ecological disruption would, in turn, badly affect global food production. According to one study, maize production in the US (the world’s largest producer) would decline by an average by 12% over ten years in our given scenario. In China, middle season rice would fall by 17% over a decade, maize by 16%, and winter wheat by 31%. With total world grain reserves amounting to less than 100 days of global consumption, such effects would place an estimated 2 billion people at risk of famine.
It gets worse
A large-scale nuclear war between the US and Russia would be far worse. Most Russian and US weapons are 10 to 50 times stronger than the bombs that destroyed Hiroshima. In a war involving the use of the two nations’ strategic nuclear weapons (those intended to be used away from battlefield, aimed at infrastructure or cities), some 150m tonnes of soot could be lofted into the upper atmosphere. This would reduce global temperatures by 8°C – the “nuclear winter” scenario. Under these conditions, food production would stop and the vast majority of the human race is likely to starve.
Eken suggests that both the scenarios of a limited regional nuclear conflict and an all-out war between US and Russia are unlikely. He may be right. However, both scenarios are possible, even if we can’t reliably quantify the risk. Continued adversarial rhetoric from both Donald Trump and Kim Jong-un about the use of nuclear weapons is not making this possibility any smaller.
What we can say, is that the doctrine of nuclear deterrence represents a high-risk gamble. Nuclear weapons do not keep us safe from acts of terrorism, nor can they be used to fight sea level rise, extreme weather, ocean acidification, biodiversity loss or antimicrobial resistance.
This is why so many medical and public health organizations have been campaigning to make nuclear weapons illegal. Regardless of how many need to be exploded to cause a catastrophe or produce an existential threat to humanity, and regardless of the risk of this happening, the adage that “prevention is the best cure” remains the case when it comes to these abhorrent and dangerous weapons.
Research papers and discussions on the public health and environmental effects of nuclear weapons will be part of the Health Through Peace 2017 conference at the University of York in September.