For starters, it would be a very, very bad day for mankind.
Sometimes it’s best not to think about just how many nukes are out there.
Nuclear weapons are enormously destructive devices capable of leveling entire cities and, in the case of an all-out nuclear exchange, ending human civilization. But what would happen if all the world’s nukes were launched at once? The YouTube channel Kurzgesagt followed this thought experiment to its apocalyptic conclusion. It’s not pretty.
The explosive yield of a nuclear weapon is typically measured in kilotons, or thousand tons of TNT. The bomb dropped on Hiroshima is typically calculated at 16 kilotons, or 16,000 tons of TNT. The W-87 warhead carried by the Minuteman III intercontinental ballistic missile has a yield of 300 kilotons. The B83 nuclear freefall bomb, carried by the B-2 Spirit stealth bomber, has a yield of up to 1.2 megatons, or 1,200 kilotons.
Beside the huge Cold War arsenals in the United States and Russia, nukes are owned by China, the United Kingdom, France, Israel, Pakistan, India, and North Korea. Altogether, there are an estimated 15,000 nuclear weapons worldwide.
Individually, each of these weapons could do incredible damage. Kurzgesagt estimates that if the world’s supply of nukes were used evenly on its large cities, the global arsenal would be enough to kill three billion people with 1,500 nukes left over. Packed inside a single, sprawling warehouse in the South American jungle, as Kurzgesagt imagines, they collectively have the power of up to 15 Krakatoa-style volcanic eruptions.
The detonation of this super-warehouse would create a fireball 31 miles across, flattening 1,864 square miles surround it. A mushroom cloud 30 miles high would follow. The nuclear firestorm would expand in all directions across South America (ironic and a bit unfair, considering South America is one of the few continents without nuclear weapons). It would also be followed by a nuclear winter scenario, in which particles of dust and ash sent skyward would enter the upper atmosphere, blocking sunlight and lowering temperatures globally for several years.
Kurzgesagt doesn’t stop there.
What if humanity mined every bit of uranium from Earth—approximately 35 million tons? Well, that’s enough to build ten billion Hiroshima bombs. Detonating all of these bombs would be an extinction-level event on par with the asteroid that ended the Age of the Dinosaurs. Except this time, it would be the end of the Age of the Humans.
Not even the crew of the International Space Station would be safe from that explosion.