A nuclear war would wipe out millions but the lingering effects on climate would kill billions more through starvation, says a US scientist who has spent decades raising the alarm.
In the 1970s, a British physicist emigrated to New Zealand to escape the potential ripple effects of a nuclear war as the United States and the Soviet Union continued the nuclear-arms race of the Cold War. On five acres on the outskirts of Whanganui, my father, helped by my mother and us four children, created a largely self-sufficient property with its own orchard, vegetable garden, cows for meat, chickens for eggs, septic tank and creek. We had small forests for firewood and, as I later discovered, to separate us from neighbours who Dad believed may come begging (or worse) for food, should there be a nuclear winter. The property was also created to hopefully withstand any similar Armageddon-like event.
As a child, I thought the arms race was a sort of show-off competition – kind of like the Space Race – so I wasn’t too worried. I heard my father mention a nuclear winter, but thought it was just that winters might become a little cooler, so we’d need more firewood.
Dad once mentioned a scientist called Robock, a name I remembered because it sounded like “robot”. But I only recently realised who it was. Distinguished professor of climatology in the department of environmental sciences at Rutgers University in New Jersey, Alan Robock has published more than 500 articles about his research on climate change. One area of expertise is climate intervention (also called geoengineering) but his primary focus is the climatic effects of nuclear war.
There may be accidents, mistakes, panicked reactions. Anything built and operated by humans can fail.
Earlier this year, Robock visited New Zealand with his wife for a holiday, and to see a scientist friend. While here, he gave a small public lecture hosted by Te Herenga Waka Victoria University of Wellington about nuclear war and global famine.
Blunt and obliging, he spoke to the Listener after his lecture to alert New Zealanders to the danger of a nuclear winter.
But what is it, exactly? The climatic effects of a nuclear war remain a theory, he points out, because scientists can’t exactly drop nuclear weapons on populated areas as experiments. But the physics behind the theory has been reaffirmed many times. Analogs – comparisons between structurally similar things – support the theory, says Robock, a trained meteorologist. They include the seasonal cycle, the diurnal cycle (driven by Earth’s rotation), forest fires, volcanic eruptions and dust storms on Mars.
In a nuclear war, many people in the radius of the blast will suffer from horrific direct effects – immediate death, acute radiation syndrome, haemorrhaging and burns. But these direct effects actually won’t be the deadliest thing, because a nuclear winter would ensue, says Robock.
“If cities and industrial areas are attacked with nuclear weapons, they’d burn, producing lots of smoke.” This black, sooty smoke would get into the stratosphere – where rain can’t wash it out – and spread around the globe. In a PowerPoint presentation at his lecture, Robock displayed an image of Earth clad in a cloak of thick black smoke that blocks out much of the sunlight. Temperatures would drop below freezing even in summer.
The resulting cold, dark, dry conditions would cause global crop failure. In a study, Robock and collaborators modelled the effect of nuclear war on global food production (assuming that exports and imports have ended). They projected that livestock and aquatic food wouldn’t compensate for reduced crop output in almost all countries.
A nuclear winter could cut a person’s available calories by as much as 90%. As many as 10 times more people would die from starvation as from the direct effects of nuclear blasts, Robock says. “A nuclear winter could kill most of humanity.”
It might last five to 10 years (maybe more), and severe ozone depletion would expose survivors to damaging ultraviolet light.
Assuming any nuclear war was confined to the Northern Hemisphere, New Zealand would fare better than most countries, given we’d keep the meat and dairy products we’re currently exporting and we’d have kai moana. But we’d no longer be importing crops, and our diets would change a lot as the nuclear winter took hold. Vegans, beware. “There would still be enough food for everybody in New Zealand if it was distributed evenly and people co-operated,” Robock says. Just enough, that is. But because we import fuel, we couldn’t transport much food.
Could we be literally fighting each other for food? “Yes. And you’d have flotillas of hungry people flocking to your shores.” And they may not be polite about it.
Any is too many
Robock, 75, has researched this field for more than 40 years. “In the 1980s, when we scientists worked on nuclear winter, it was very influential. Ronald Reagan and Mikhail Gorbachev agreed to end the arms race and I felt empowered.” In 1987, the Intermediate-Range Nuclear Forces Treaty was signed by the US and the Soviet Union (it henceforth applied to the Russian Federation). The Cold War was over.
“Since then, the number of nuclear weapons dropped, so people seem to have forgotten about a possible nuclear winter.” But it remains a grave threat. There are currently about 12,500 nuclear weapons globally, a quarter of the 1985 arsenal but way more than enough to cause a nuclear winter. Russia and the US own about 90% of these weapons, with pretty evenly matched arsenals. The UK, France, China, North Korea, India, Pakistan and Israel have up to a few hundred weapons each.
Concerningly, the numbers have been increasing a little. Israel says its strikes against Iran were aimed at halting what it alleges is Tehran’s rapid progress in developing nuclear weapons. But some experts warn that if indeed Iran is building nuclear capability, this will only increase its determination.
China is believed to have the fastest-growing nuclear arsenal among the nine nuclear-armed states – about 500 nuclear warheads – while North Korean leader Kim Jong Un has vowed to expand his nuclear arsenal “exponentially”.
“The question is, why have all but nine countries decided against having nuclear weapons?” Robock asks. “And why do seven of them have so few?” The short answer is that they could lead to billions of deaths.
So why do nine countries have them? The short answer is deterrence: nuclear nations claim they maintain nuclear arsenals not to use them but to dissuade attacks on them.
“However, nuclear weapons don’t deter attacks by terrorists or cyberwarfare, nor attacks on nuclear nations by conventional weapons – so nuclear weapons aren’t a perfect deterrent. Also, will deterrence last forever? Because it has to be perfect.”
World War II remains the only time nuclear weapons have been used in armed conflict. “But to say, ‘It’s lucky we’ve had no nuclear war in 80 years,’ isn’t a great approach.”
Who might break that ‘lucky streak’? “For a while, we thought Pakistan and India were the likeliest to have a nuclear war.” Robock and collaborators calculated that if there were a nuclear conflict between Pakistan and India, using just 1% of the world’s nuclear weapons, 27 million people would die of the direct effects.
“There wouldn’t be what we call nuclear winter – that is, temperatures wouldn’t get below freezing in the summertime – but there would be enough climate change that one to two billion people could die from famine." The two countries traded missile and mortar strikes in early May.
“Perhaps the publication of our science then, with multiple articles in Pakistani and Indian newspapers [after the recent clashes], has prevented a nuclear war there, including producing pressure from other countries on them to have a truce.” That said, he thinks a nuclear conflict between them is unlikely.
What if the US and Russia had a nuclear war? “Up to 6 billion of the 8 billion people on the planet could die. Ten times as many would die from famine as from the direct effects.”
Greed and vested interests are at play. Some countries want nuclear arsenals for political reasons.
As it stands, if anyone attacks a member of Nato, the military alliance with 30 member states in Europe plus Canada and the US (though Donald Trump has repeatedly threatened to withdraw), the other members, including the nuclear states of France, the UK and US, must support them.
However, Robock thinks nuclear war between Nato and Russia is unlikely. “If there is one, I think it’ll be unintentional.”
What’s the risk of nuclear war happening? “Human behaviour isn’t my area of expertise,” Robock says, “so I can’t predict whether somebody would use nuclear weapons on purpose, but I don’t think they will. Because that’s mutually assured destruction.
“However, we must eliminate all nuclear weapons, because the unintentional is the most likely cause of nuclear war.” Think human or systems error. There may be accidents, mistakes, miscommunications, panicked reactions, a faulty computer or satellite.
“Maybe someone misreads satellite images, maybe there’s an accidental launch, maybe there’s a false warning of a launch. Anything built and operated by humans can fail.”
Close calls with nuclear weapons have been narrowly averted before, he says. “How many other incidents were kept secret?”
Robock says the threat of a nuclear winter is often ignored or downplayed – painted as scaremongering, as irrelevant, even disproven. Greed and vested interests are at play, he says. Some countries want nuclear arsenals for political reasons. “The nuclear-winter theory is also an existential threat to the nuclear-weapon industry. You can make lots of money building new nuclear weapons and submarines.”
Cassandra calling
For decades, Robock has warned that nuclear winter is “a real and present danger”. For his perseverance, he was the inaugural winner of the Cassandra Award, set up in 2018 by former US intelligence and counterterrorism official Richard A Clarke and former US National Security Council director RP Eddy, authors of Warnings: Finding Cassandras to Stop Catastrophes. Named after the Trojan princess of legend, Cassandra, whose prophecies were unheeded but came to pass, the awards aim to “convince decision-makers that they should take this person (and threat) more seriously”.
How does Robock feel about his warnings being somewhat unheeded? It frustrates but doesn’t demoralise him.
“People ask how I can work on something so depressing. I say ‘to prevent it happening’.” He quotes Nobel-winning climate scientist Sherwood Rowland, who asked in 1986: “What’s the use of having developed a science well enough to make predictions if, in the end, all we’re willing to do is stand around and wait for them to come true?”
Says Robock: “All I can do is do what I can. I do research, write journal articles, post on social media and give talks. I’ve been particularly trying to do something when it comes to treaties to limit nuclear weapons.”
In 2011, he gave a talk in Cuba. Fidel Castro attended, and they met afterwards. “It was very surreal,” Robock says. His recorded talk was broadcast on Cuba’s prime-time TV the next day. “Then Castro wrote a blog, saying we must get rid of nuclear weapons to save the world.” Cuba was among the first countries to sign the UN Treaty On The Prohibition of Nuclear Weapons.
“I was involved in efforts to educate nations about the impacts of nuclear war, which resulted in that treaty,” Robock says. Taking force in 2021, signed by 94 nation states, it’s the first legally binding international agreement to prohibit and ultimately eliminate all nuclear weapons. The nine nuclear nations didn’t sign it.
I don’t like Trump for many, many reasons, but I don’t think he’s pro-war. And nuclear war would ruin his golf courses.
Where are the US and Russia at, treaty-wise? The New Strategic Arms Reduction Treaty, which limits the number of nuclear warheads both countries can deploy, was signed by then Russian president Dmitry Medvedev and his US counterpart Barack Obama in 2010. Joe Biden extended it. In February, Russian Deputy Foreign Minister Sergei Ryabkov stated, “On Feb 5, 2026, the pact expires and after this it will not exist.”
Trump has said he wants to restart nuclear-arms-control talks with Russia and China (motivated in part, it seems, by wanting to cut defence spending). But the president is also unpredictable. During his first term, Trump withdrew the US from the Cold War-ending Intermediate-Range Nuclear Forces Treaty with Russia.
Robock penned an open letter to Trump at the start of both his terms. “I wrote, ‘You have a chance to reduce the danger of nuclear weapons. The first thing is to take land-based missiles off hair-trigger alert.’” (These can be airborne in 10 minutes.) “I said, ‘Doing that will get you a Nobel Prize, and it’s gold and beautiful.’” Despite the impressive personalised appeal, Robock did not get a reply.
Should we worry that Trump will use the nuclear codes, given he’s extremely volatile and no one else needs to approve this step?
“I don’t like Trump for many, many reasons, but I don’t think he’s pro-war. And nuclear war would ruin his golf courses. But if he was told, ‘Mr President, we’re under attack and we have 10 minutes to launch nuclear missiles,’ would he think, ‘I don’t care, let’s do it,’ or ‘Why kill people when deterrence hasn’t worked?’ Because you’re all still going to die from starvation.”
Dinosaur lesson
Robock is always keen to push his message, which is why he agreed to give the lecture at Victoria while on holiday. He urged his audience to be familiar with organisations including the Physicists Coalition For Nuclear Threat Reduction, Students For Nuclear Disarmament or the International Campaign To Abolish Nuclear Weapons (Ican). In 2017, Ican was awarded the Nobel Peace Prize for efforts based partly on Robock’s work.
“My work is an appeal to intellect and there also needs to be an appeal to emotions. Does anyone want to make a feature film?”
Robock has often collaborated on research with Owen Brian Toon, a University of Colorado professor of atmospheric and oceanic sciences, whose TEDx talk – about how an asteroid killed the dinosaurs – has had nine million views. The pair have co-written a book, which has just been released, Earth in Flames: How an Asteroid Killed the Dinosaurs And How We Can Avoid A Similar Fate From Nuclear Winter. Robock is writing a version for kids, simplifying the science and emphasising that, “for them to have a future, they have to get the adults to rid the world of nuclear weapons”.
Will we? Robock doesn’t know. “But there are tipping points in human behaviour. When I was young, we couldn’t imagine gay marriage, legalising marijuana or a black president. Things can change just like that,” he says, snapping his fingers. “So there could be a tipping point in this, too.”
Sarah Lang is a Wellington-based writer.