A nuclear war between India and Pakistan would not only have catastrophic affects in these two countries or their neighbours, but it could cause one billion people to starve to death across the world.
Hundreds of millions of more would die from disease and conflicts over food in the aftermath of any such war.
US medical expert Ira Helfand will today present this horrifying scenario in London during a conference at the Royal Society of Medicine.
"A limited nuclear war taking place far away poses a threat that should concern everyone on the planet," the New Scientist magazine quoted Helfand as saying.
"It is appropriate, given the data, to be frightened," said Helfand, who is an emergency-room doctor in Northampton, Massachusetts, US, and a co-founder of the US anti-nuclear group, Physicians for Social Responsibility.
Helfand has tried to map out the global consequences of India and Pakistan exploding 100 Hiroshima-sized nuclear warheads.
Referring to earlier studies that have suggested that in such a conflict, the annual growing season in the world's most important grain-producing areas would shrink by between 10 and 20 days, he said that the world is ill-prepared to cope with such a disaster.
"Global grain stocks stand at 49 days, lower than at any point in the past five decades," he said, adding: "These stocks would not provide any significant reserve in the event of a sharp decline in production. We would see hoarding on a global scale."