The mushroom cloud from the “Ivy Mike” nuclear test over Enewetak Atoll in the Marshall Islands on November 1, 1952. Image : Los Alamos National Laborator

In addition to killing as many as 125 million people, a nuclear exchange between India and Pakistan would unleash mass starvation around the world due to the ensuing climate impacts, according to a disturbing new study.


As if we need to be reminded of the horrors of nuclear war, new research published today in Science Advances presents evidence showing that a nuclear exchange between two minor powers, specifically India and Pakistan, would inflict both a regional and global catastrophe.

The new research, which involved researchers from the University of Colorado, Boulder, Rutgers University-New Brunswick, the U.S. National Center for Atmospheric Research, among other institutions, offered some alarming estimates, showing that a war between the two nations would cause between 50 million and 125 million deaths in the hours and days following a nuclear exchange.


What the research also shows, however, is how the ensuing climate impacts, produced primarily by smoke from fires, would cause devastating crop failures and the collapse of vital ecosystems. This nuclear winter would go on to cause worldwide starvation, leading to “collateral fatalities,” in the words of the researchers.



No estimate was offered for how many people would be affected or killed by starvation, but it would likely be significant, given that the ensuing nuclear winter would last for at least a decade.

The new paper shows that a nuclear war, even one involving the smaller nuclear powers, would result in global consequences. The new paper is reminiscent of research done in 2017 showing that even “limited” nuclear strikes would cause climate chaos and a 2018 study seeking to determine the “best- case scenario” for nuclear war, that is, the fewest nukes required to maintain deterrence.


Alan Robock, a co-author of the new paper and researcher at the Department of Environmental Sciences at Rutgers University–New Brunswick, along with his colleagues, came to these results by simulating a scenario in which nuclear war erupted in 2025 between India and Pakistan. These nations are currently embroiled in a bitter dispute over the Kashmir territory.

“We evaluated the potential climate impacts of a war between India and Pakistan in the near future, with larger numbers of weapons, larger weapons, and larger targets, as compared to our analysis a decade ago,” wrote Robock in an email to Gizmodo. Indeed, the new paper is an update to similar research conducted in 2010 by Robock and Owen Toon, a professor in the Department of Atmospheric and Oceanic Sciences at the University of Colorado at Boulder —research that largely reached the same conclusions.


In the imagined scenario, the researchers considered the use of between 400 to 500 nuclear weapons, which is the predicted arsenal for India and Pakistan in about six years. The nuclear weapons used in the simulation ranged from Hiroshima-sized bombs (15 kilotons of TNT) through to modern weapons capable of unleashing a few hundred kilotons of explosive power. The scenario saw India deploy 100 nuclear warheads while Pakistan deployed 150.

“A war between two new, ‘smaller’ nuclear powers on the other side of the world now has the potential to plunge Earth into an ice age climate. It would be instant climate change.”


A “regional catastrophe would occur if India and Pakistan were to engage in a full-scale nuclear war with their expanding arsenals,” wrote the authors in the study. The simulated nuclear exchange would result in any where from 50 million to 125 million deaths, which would occur almost instantly from the immediate, direct effects of the bombs. As the researchers noted in the study:

India would suffer two to three times more fatalities and casualties than Pakistan because, in our scenario, Pakistan uses more weapons than India and because India has a much larger population and more densely populated cities. However, as a percentage of the urban population, Pakistan’s losses would be about twice those of India. In general...the fatalities and casualties increase rapidly even up to the 250th explosion due to the high population in India, whereas the rate of increase for Pakistan is much lower even for the 50th explosion.


For Robock, the biggest surprise of these findings was in how a “war between two new, ‘smaller’ nuclear powers on the other side of the world now has the potential to plunge Earth into an ice age climate,” he told Gizmodo. “It would be instant climate change.”

The U.S. and Russia currently account for around 93 percent of the planet’s estimated 13,900 nuclear weapons, according to the paper.


Fires caused by the nuclear exchange would deliver somewhere between 16 million and 36 million tons of soot—otherwise known as black carbon—into the Earth’s upper atmosphere. Within weeks, this soot would proliferate around the world. According to the researchers’ estimates, sunlight would diminish by a factor of 20 to 35 percent, which would in turn cool the ground by 2 to 3 degrees Celsius (3.6 to 9 degrees Fahrenheit) and reduce precipitation by 15 to 30 percent, depending on the region.

“Threatening to use nuclear weapons to deter is threatening to be a suicide bomber.”


This would be very bad for the world’s vegetation, whether terrestrial or aquatic . Plant life would decline by 15 to 30 percent on land and 5 to 15 percent in the oceans. This nuclear winter would last for at least 10 years, according to the researchers. The paper summarizes as follows:

[S]evere short-term climate perturbations, with temperatures declining to values not seen on Earth since the middle of the last Ice Age, would be triggered by smoke from burning cities, a global disaster threatening food production worldwide and mass starvation, as well as severe disruption to natural ecosystems. Compounding the devastation brought upon their own countries, decisions by Indian and Pakistani military leaders and politicians to use nuclear weapons could severely affect every other nation on Earth.


As an interesting and relevant aside, the 2017 Nobel Peace Prize was awarded to the International Campaign to Abolish Nuclear Weapons (ICAN). As Robock explained to Gizmodo, ICAN “was enacted partly based on our previous results.” His hope is that the world’s nine nuclear nations will “sign and ratify the 2017 UN Treaty on the Prohibition of Nuclear Weapons.”



The results of the new study “reinforce the need to abolish nuclear weapons,” said Robock. “They are instruments of mass genocide. And the myth of deterrence persists. But if nuclear weapons were used they would have a huge impact, through climate change, on the nation using them,” he said.


“Threatening to use nuclear weapons to deter is threatening to be a suicide bomber,” he added.