The United States has a population of about 329 million people, is protected by two oceans, and grows food that feeds hundreds of millions around the world. We have a powerful military, peaceful borders with our neighbors, and a network of alliances. We would seem well-positioned to defend ourselves from the dangers of foreign war. Our fate surely thus rests in our own hands; the only question is whether we will be wise enough and lucky enough to chart a safe national course.

Who knew? It turns out that this sense of control is illusory. 

Consider a hypothetical regional nuclear war between India and Pakistan. This event does not involve a single US soldier or weapon. The entire war takes place 7,000 miles from North America. It uses less than one-twentieth of all nuclear weapons in the world. Yet, as a result of those far-off developments, more than 200 million Americans—200 million!—would end up dead from hunger over the next two years.

So finds a landmark study published in Nature Food this week. An international team led by scientists at Rutgers University modeled what happens to crop production worldwide after a minor or regional nuclear war. 

It would not bring about the dreaded “nuclear winter” that would follow a major nuclear war between Russia and the United States. But a regional or “limited” nuclear war would still bring “nuclear famine”—several years of abrupt global cooling and agricultural collapse.

“In a nuclear war, bombs targeted on cities and industrial areas would start firestorms, injecting large amounts of soot into the upper atmosphere, which would spread globally and rapidly cool the planet,” the researchers report. “Famine could result for a third of Earth…even from a war between India and Pakistan using less than 3% of the global nuclear arsenal.”

Lili Xia of Rutgers and her colleagues looked at how much sun-blocking soot would be generated by cities incinerated under various regional nuclear war scenarios. They considered how far global temperatures would fall as a result, what would happen to crop production, and, finally, how many would starve. 

Their findings: As horrific as the war zone itself might be, with India and Pakistan devastated and with tens of millions of immediate fatalities—more deaths in a few days or weeks than in all of the years of World War II—that historic tragedy would be dwarfed in the coming years by starvation from global crop failures. 

In fact, the researchers found, more than 2 billion people around the world could die of hunger after an India-Pakistan war. Again, this is a scenario that assumes the vast majority of nuclear weapons are never used. It’s a regional nuclear war. No one asks our permission or seeks our input. We just find out it happened somewhere from the news. And then the skies get dark, and the temperatures drop. For years.

The Rutgers-led team’s findings are the latest in a flurry of new studies modeling regional nuclear wars. International Physicians for the Prevention of Nuclear War released a report this week (by me) summarizing some of the latest data—much of which has been building behind the scenes of the Covid-19 pandemic, and only now being appreciated . 

For example, a paper in 2020 led by Jonas Jägermeyr, a scientist at NASA’s Goddard Institute for Space Studies, looked at the same scenario of an India-Pakistan nuclear war, and found that it would cause abrupt global cooling of 1.8 degrees Celsius, five years of bad harvests, and “adverse consequences for global food security unmatched in modern history.”

A paper led by Brian Toon of the University of Colorado’s Laboratory for Atmospheric and Space Physics and published in September 2019—right before the coronavirus vacuumed up all media and public attention—examined escalating scenarios of regional India-Pakistan wars. Toon and colleagues found the larger scenarios—again, “large” is oh-so-relative, since it would still involve less than one twentieth of world arsenals—would bring abrupt global cooling of 5.5–6.5 degrees Celsius.

For comparison, the last Ice Age, when our ancestors contended with wooly mammoths and saber tooth tigers, was about 6 degrees Celsius cooler than today.

The scenarios considered in recent studies often involve a hypothetical nuclear conflict between India and Pakistan—two nations who have fought recent wars, continue to have border skirmishes, and deploy nuclear weapons prominently in their military planning. But it does not necessarily matter where such a war happens. Whether cities and industrial areas are incinerated in the Middle East, on the Indian subcontinent, or in Central Europe, the soot rises into the same sky.

Societies around the world would take desperate measures to adapt to a darker, cooler planet. For example, livestock could be killed off en masse, both to feed humans in the first year and also to divert animal feed to human consumption; household food waste (around 20 percent on global average) could be reduced; unpalatable fish species could enter the diet; and international trade might be shut down, as hungry nations seek to prevent food from being exported. 

The Rutgers-led team behind the Nature Food study crunched the numbers for many of these mitigation measures as well. But once the food available in the world drops by one-fourth or half, people starve no matter how wisely they order their affairs. What’s more, the researchers are only modeling crop failures due to sun-blocking soot and the associated global cooling. Significantly, they do not consider the effects on available food or human health of radioactive fallout from the nuclear war; or of increased UV radiation from likely ozone damage; or of economic disruptions from any possible breakdown of supply chains or public order. So the model in Nature Food—which shows up to 200 million Americans starving to death in some regional India-Pakistan war scenarios—if anything may underestimate the devastation.

Russia and the United States control more than 90 percent of all nuclear weapons. But seven other nations are nuclear-armed: France, Great Britain, Israel, India, Pakistan, China and North Korea. 

Our national discussions of this situation often complacently assume the United States is safe because, with our massive arsenals, no one would dare attack us. But based on this new data, that asks the wrong question: Now it turns out the United States can be devastated if any two other nations attack each other, leaving us entirely out of it!

Pakistan or France may seem mere regional powers—but each is capable of starting their own local nuclear war, only to have it spill over across America’s skies, from sea to shining sea. For that matter, the power to destroy modern civilization is in the hands not just of nine national governments, but also of many lower-level individuals throughout military hierarchies. Consider that every commander of a US Ohio-class or a Russian Borei-class submarine has at his disposal firepower comparable to that of an entire nation such as Pakistan or France—and that there are 14 Ohio class subs and five Borei-class subs in service. 

There is one good thing for the United States. We are the nation that pioneered the nuclear weapon and the (deeply flawed) theory of nuclear war fighting; we hold the most powerful arsenal and the world’s mightiest military. There is no other nation better poised to captain fate—our own, and the world’s—because no one else could more effectively lead a rapid, verifiable, global stand-down and abolition of nuclear weapons. The only question is whether we will be wise enough, and lucky enough, to chart that safe course.