Nuclear war would cause a global famine and kill billions

More than 5 billion people would die of hunger following a full-scale nuclear war between the U.S. and Russia, according to a global study led by Rutgers climate scientists that estimates post-conflict crop production.

"The data tell us one thing: We must prevent a nuclear war from ever happening," said Alan Robock, a Distinguished Professor of climate science in the Department of Environmental Sciences at Rutgers Universityand co-author of the study. Lili Xia, an assistant research professor in the Department of Environmental Sciences at Rutgers,is lead author of the study published in the journal Nature Food.

Building on past research, Xia, Robock and their colleagues worked to calculate how much Sun-blocking soot would enter the atmosphere from firestorms that would be ignited by the detonation of nuclear weapons. Researchers calculated soot dispersal from six war scenarios -- five smaller India-Pakistan wars and a large U.S.-Russia war -- based on the size of each country's nuclear arsenal.

These data then were entered into the Community Earth System Model, a climate forecasting tool supported by the National Center for Atmospheric Research (NCAR). The NCAR Community Land Model made it possible to estimate productivity of major crops (maize, rice, spring wheat and soybean) on a country-by-country basis. The researchers also examined projected changes to livestock pasture and in global marine fisheries.

Under even the smallest nuclear scenario, a localized war between India and Pakistan, global average caloric production decreased 7 percent within five years of the conflict. In the largest war scenario tested -- a full-scale U.S.-Russia nuclear conflict -- global average caloric production decreased by about 90 percent three to four years after the fighting.

Crop declines would be the most severe in the mid-high latitude nations, including major exporting countries such as Russia and the U.S., which could trigger export restrictions and cause severe disruptions in import-dependent countries in Africa and the Middle East.

These changes would induce a catastrophic disruption of global food markets, the researchers conclude. Even a 7 percent global decline in crop yield would exceed the largest anomaly ever recorded since the beginning of Food and Agricultural Organization observational records in 1961. Under the largest war scenario, more than 75 percent of the planet would be starving within two years.

Researchers considered whether using crops fed to livestock as human food or reducing food waste could offset caloric losses in a war's immediate aftermath, but the savings were minimal under the large injection scenarios.

"Future work will bring even more granularity to the crop models," Xia said.

"For instance, the ozone layer would be destroyed by the heating of the stratosphere, producing more ultraviolet radiation at the surface, and we need to understand that impact on food supplies," she said.

Climate scientists at the University of Colorado, which partnered with Rutgers on the study, are also creating detailed soot models for specific cities, such as Washington, D.C., with inventories of every building to get a more accurate picture of how much smoke would be produced.

Robock said researchers already have more than enough information to know that a nuclear war of any size would obliterate global food systems, killing billions of people in the process.

"If nuclear weapons exist, they can be used, and the world has come close to nuclear war several times," Robock said. "Banning nuclear weapons is the only long-term solution. The five-year-old UN Treaty on the Prohibition of Nuclear Weapons has been ratified by 66 nations, but none of the nine nuclear states. Our work makes clear that it is time for those nine states to listen to science and the rest of the world and sign this treaty."

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Even a limited India-Pakistan nuclear war would bring global famine, says study

Illustration of nuclear bomb explosion.

The concept of nuclear winter -- a years-long planetary freeze brought on by airborne soot generated by nuclear bombs -- has been around for decades. But such speculations have been based largely on back-of-the-envelope calculations involving a total war between Russia and the United States. Now, a new multinational study incorporating the latest models of global climate, crop production and trade examines the possible effects of a less gargantuan but perhaps more likely exchange between two longtime nuclear-armed enemies: India and Pakistan. It suggests that even a limited war between the two would cause unprecedented planet-wide food shortages and probable starvation lasting more than a decade. The study appears this week in the journal Proceedings of the National Academy of Sciences.

Of an estimated 14,000 nuclear warheads worldwide, close to 95 percent belong to the United States and Russia. India and Pakistan are thought to have about 150 each. The study examines the potential effects if they were to each set off 50 Hiroshima-size bombs -- less than 1 percent of the estimated world arsenal.

In addition to direct death and destruction, the authors say that firestorms following the bombings would launch some 5 million tons of soot toward the stratosphere. There, it would spread globally and remain, absorbing sunlight and lowering global mean temperatures by about 1.8 degrees C (3.25 F) for at least five years. The scientists project that this would in turn cause production of the world's four main cereal crops -- maize, wheat, soybeans and rice -- to plummet an average 11 percent over that period, with tapering effects lasting another five to 10 years.

"Even this regional, limited war would have devastating indirect implications worldwide," said Jonas Jägermeyr, a postdoctoral scientist at the NASA Goddard Institute for Space Studies who led the study. "It would exceed the largest famine in documented history."

According to the study, crops would be hardest hit in the northerly breadbasket regions of the United States, Canada, Europe, Russia and China. But paradoxically, southerly regions would suffer much more hunger. That is because many developed nations in the north produce huge surpluses, which are largely exported to nations in the Global South that are barely able to feed themselves. If these surpluses were to dry up, the effects would ripple out through the global trade system. The authors estimate that some 70 largely poor countries with a cumulative population of 1.3 billion people would then see food supplies drop more than 20 percent.

Some adverse effects on crops would come from shifts in precipitation and solar radiation, but the great majority would stem from drops in temperature, according to the study. Crops would suffer most in countries north of 30 degrees simply because temperatures there are lower and growing seasons shorter to begin with. Even modest declines in growing-season warmth could leave crops struggling to mature, and susceptible to deadly cold snaps. As a result, harvests of maize, the world's main cereal crop, could drop by nearly 20 percent in the United States, and an astonishing 50 percent in Russia. Wheat and soybeans, the second and third most important cereals, would also see steep declines. In southerly latitudes, rice might not suffer as badly, and cooler temperatures might even increase maize harvests in parts of South America and Africa. But this would do little to offset the much larger declines in other regions, according to the study.

Since many developed countries produce surpluses for export, their excess production and reserves might tide them over for at least a few years before shortages set in. But this would come at the expense of countries in the Global South. Developed nations almost certainly would impose export bans in order to protect their own populations, and by year four or five, many nations that today already struggle with malnutrition would see catastrophic drops in food availability. Among those the authors list as the hardest hit: Somalia, Niger, Rwanda, Honduras, Syria, Yemen and Bangladesh.

If nuclear weapons continue to exist, "they can be used with tragic consequences for the world," said study coauthor Alan Robock, a climatologist at Rutgers University who has long studied the potential effects of nuclear war. "As horrible as the direct effects of nuclear weapons would be, more people could die outside the target areas due to famine."

Previously, Jägermeyr has studied the potential effects of global warming on agriculture, which most scientists agree will suffer badly. But, he said, a sudden nuclear-caused cooling would hit food systems far worse. And, looking backward, the the effects on food availability would be four times worse than any previously recorded global agriculture upsets caused by droughts, floods, or volcanic eruptions, he said.

The study might be erring on the conservative side. For one, India and Pakistan may well have bombs far bigger than the ones the scientists use in their assumptions. For another, the study leaves India and Pakistan themselves out of the crop analyses, in order to avoid mixing up the direct effects of a war with the indirect ones. That aside, Jägermeyr said that one could reasonably assume that food production in the remnants of the two countries would drop essentially to zero. The scientists also did not factor in the possible effects of radioactive fallout, nor the probability that floating soot would cause the stratosphere to heat up at the same time the surface was cooling. This would in turn cause stratospheric ozone to dissipate, and similar to the effects of now-banned refrigerants, this would admit more ultraviolet rays to the Earth's surface, damaging humans and agriculture even more.

Much attention has been focused recently on North Korea's nuclear program, and the potential for Iran or other countries to start up their own arsenals. But many experts have long regarded Pakistan and India as the most dangerous players, because of their history of near-continuous conflict over territory and other issues. India tested its first nuclear weapon in 1974, and when Pakistan followed in 1998, the stakes grew. The two countries have already had four full-scale conventional wars, in 1947, 1965, 1971 and 1999, along with many substantial skirmishes in between. Recently, tensions over the disputed region of Kashmir have flared again.

"We're not saying a nuclear conflict is around the corner. But it is important to understand what could happen," said Jägermeyr.

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