A nuclear war between two countries would be enough to plunge the world into a “Little Ice Age”, scientists have warned.
Researchers found that even nations not involved in the dispute would suffer crop failures and plummeting temperatures, as the soot and smoke from nuclear firestorms thousands of miles away would block out the sun.
In the first month following nuclear detonation, average global temperatures would plunge by about 13F - a larger temperature change than in the last Ice Age, warned experts from Louisiana State and Rutgers universities.
As the planet became colder, sea ice would expand by more than six million square miles and 6ft deep in some basins, blocking major ports including Beijing’s Port of Tianjin, Copenhagen and St Petersburg.
The sea ice would spread into normally ice-free coastal regions, blocking shipping across the Northern Hemisphere - making it difficult to get food and supplies into some cities.
The sudden drop in light and ocean temperatures, especially from the Arctic to the North Atlantic and North Pacific oceans, would kill the marine algae which form the foundation marine food web - creating a famine in the ocean, effectively bringing the fishing industry to a halt.
'We must do everything we can to avoid nuclear war'
“It doesn’t matter who is bombing whom, it can be India and Pakistan or Nato and Russia,” said Prof Cheryl Harrison, lead author from Louisiana State University’s Department of Oceanography and Coastal Sciences.
“Once the smoke is released into the upper atmosphere, it spreads globally and affects everyone.
“We must do everything we can to avoid nuclear war. The effects are too likely to be globally catastrophic.”
The study is the first to gauge the impact of today’s nuclear weapons and simulated the impact of a war between the US and Russia, where 4,400 100 kiloton weapons might be expected. It also looked at the effect of a war between Indian and Pakistan, where around 10 times fewer missiles would be expected.
Researchers estimated that even the smaller war would see between 11 billion and 103 billion pounds of smoke and soot ejected into the upper atmosphere, blocking out the light from the sun. A war between superpowers could see three times that level.
Ocean recovery would likely take decades at the surface and hundreds of years at depth, while changes to Arctic sea ice will likely last thousands of years and effectively be a “Nuclear Little Ice Age”.
'The world simply cannot go down that path'
“Nuclear warfare results in dire consequences for everyone,” added Alan Robock, co-author and distinguished professor in the Department of Environmental Sciences at Rutgers University.
“World leaders have used our studies previously as an impetus to end the nuclear arms race in the 1980s, and five years ago to pass a treaty in the United Nations to ban nuclear weapons. We hope that this new study will encourage more nations to ratify the ban treaty.
“A nuclear war would be a significant planetary tipping point. With Russia at war in Ukraine and President Vladimir Putin threatening to use nuclear weapons, these findings are a strong warning that the world simply cannot go down that path.”
The research was published in the journal AGU Advances.