A limited nuclear war between India and Pakistan may lead to the worst global food losses in modern history, according to a first-of-its-kind study.
The study, published in the journal PNAS, found that sudden global cooling from a war using less than 1 per cent of nuclear weapons worldwide, along with less precipitation and sunlight, could disrupt food production and trade worldwide for about a decade.
This would be more than the impact from man-made climate change by late 21st century, according to the researchers from Rutgers University-New Brunswick in the US.
While the impacts of global warming on agricultural productivity have been studied extensively, the implications of sudden cooling for global crop growth are little understood, they said.
"Our results add to the reasons that nuclear weapons must be eliminated because if they exist, they can be used with tragic consequences for the world," said study study co-author Alan Robock, a professor at Rutgers University.
"As horrible as the direct effects of nuclear weapons would be, more people could die outside the target areas due to famine," he said.
Robock co-authored a recent study published in the journal Science Advances estimating that over 100 million people could die immediately if India and Pakistan wage a nuclear war, followed by global mass starvation.
For the latest study, scientists used a scenario of 5 million tonnes of black smoke from massive fires injected into the upper atmosphere that could result from using only 100 nuclear weapons.
That would cool the Earth by 1.8 degrees Celsius, and lead to 8 per cent lower precipitation and less sunlight for at least five years.
Scientists included those climate change scenarios in computer simulations for four major crops that account for 90 per cent of global cereal production in terms of calories.
The scientists found that corn calorie production would fall by 13 per cent, wheat by 11 per cent, rice by 3 per cent and soybeans by 17 per cent over five years.
Total first-year losses of 12 per cent would be four times larger than any food shortage in history, such as those caused by historic droughts and volcanic eruptions, the researchers said.
Analyses of food trade networks show that domestic reserves and global trade can largely buffer the loss of food production in the first year, they said.
However, the researchers noted that multi-year losses would reduce domestic food availability, especially in food-insecure countries.
By year five, corn and wheat availability would decrease by 13 per cent globally and by more than 20 per cent in 71 countries with a total of 1.3 billion people, the study found.
Corn production in the US and Canada -- representing more than 40 per cent of global production -- would drop by 17.5 per cent. Robock said the scenario with 5 million tonnes of smoke was developed more than a decade ago.
Scientists now think that 16 million tonness of smoke could arise from a nuclear war between India and Pakistan since they now have more and bigger weapons and their potential targets are larger.
This means the impacts could be three-fold larger, according to the researchers.