Mutually assured destruction — the threat from the last days of the Cold war between US and Russia — is rearing its head again, with the US and North Korea threatening action against each other.

A similar threat seems to be brewing between India and China, with Chinese media issuing warning after warning of a possible "military action" against India if it does not pull out its troops from Doklam in Bhutan, which China has all of a sudden claimed as its own.

The bigger threat here is that all four countries have nuclear weapons, and even limited use of them can mean nothing short of cataclysm for the whole world, and kill as many as 1 billion people!

Nuclear autumn

The threat of nuclear winter — the cooling of Earth due to carbon particles released into the air stopping the Sun's radiation from percolating down to the ground — had been an omnipresent one in the closing days of the Cold War.

That threat has now been replaced with one of nuclear autumn, and it's no less devastating! And if one goes by Stephen Hawking, nuclear war could very well wipe out mankind in the "foreseeable future"!

Now, according to a report in the journal Environment by Adam J Liska, Tyler R White, Eric R Holley and Robert J Oglesby, a nuclear autumn will result in "great reductions in agricultural productivity, stratospheric ozone loss, and spread of hazardous radioactive fallout."

The scenario

The study anticipates "limited use of nuclear weapons" — effectively from one to 20 nuclear warheads being detonated. It then goes on to explain the effects of 100 nuclear explosions, each of which has the yield of 15 kilotons of TNT — or the equivalent of Little Boy, the nuclear bomb the US dropped on Hiroshima.

"The resulting oxidation of carbonaceous materials (eg, soils, biomass, fossil fuels, asphalt, plastics) was estimated to disperse more than 5 million metric tons (5 Tg C) of black carbon smoke particles into the stratosphere," it says.

And then comes the scary part, where a drop in temperature and climate changes will have a domino effect on the human species.

Apocalypse now?

Detailing some of the possible fallout, the report says: "Agricultural growing seasons could be reduced by 10-40 days per year for at least five years; global temperatures could be below normal for as long as 25 years; and immediate short-term temperatures could be colder than have occurred in the last 1,000 years."

India could have it much worse, with the prediction saying: "Precipitation could decrease by as much as 20-80 percent in the Asian monsoon region." Others would not be spared as well: "Large reductions in rainfall would occur in South America and southern Africa, and the American Southwest and Western Australia could be 20-60 percent drier."

The low precipitation would cause famines that could "kill up to a billion people from starvation, which would probably most affect those communities that are already in food-insecure environments in the developing world, particularly in Sub-Saharan Africa, South Asia, and the Middle East," says the report.