thaluikhain said:
It should be pointed out that the US does not have a nuclear arsenal capable of destroying even our species, let alone all life on Earth. Even the combined nuclear arsenals of the entire world aren't enough to wipe everyone out, humanity would survive. Fallout is extremely nasty, but it's not planet killing (at least not the amount humanity is currently able to produce). An interesting thing I read in a US nuclear survival thing, the amount of cancer caused by a nuclear exchange between the US and USSR in the 80s would be less than the amount of cancer prevented if wearing hats outdoors became a worldwide fashion.
Now, the death toll would be appalling, you'd fuck civilisation right up for a few centuries and all. That's what they mean by "end of the world", it really needs "as we know it" unless you are being pedantic.
In my experience, the effects of nuclear war are exagerated, possibly to change people's attitudes against it...presumably there are those who don't find massive death tolls, loss of infrastructure and governmental collapse to be scary enough.
On the other hand, the common or garden problems are overlooked, they don't seem exciting an nuclear enough. Lots of people will be horribly maimed by flying glass, and the medical facilities left intact will be swamped. You'll lose power and running water, you've got cities full of decaying corpses, your transport system is wrecked etc.
That's .... extremely debatable. he reality is, that we don't know exactly what would happen if nuclear war came about. We have no practical real world example - only two nukes were ever detonated in anger and those were child's toys compared to the tonnage of modern nukes.
So you're left with theories. What I can say is that the majority of academics and scientists would disagree with you and say that the effects of deploying the nuclear arsenals of the world would be enough to do irreparable damage to the planet surface and the atmosphere. Fallout would be damaging, but nuclear winter and other climatic effects are your biggest problem - crops would fail, temperatures would drop, weather patterns would experience catastrophic change. The chain effect would result in enough species on Earth being killed off to count as a mass extinction event. Whether or not it would kill all species, there's less consensus. But the majority of theorists would say that at the very least, civilization would collapse and human population would mostly be wiped out from famine, disease, and the war itself.
But on the other hand, this majority isn't overwhelming. There are significant numbers of theorists who say that human civilization could survive a nuclear war. At the extreme, they believe nuclear war will have minimal impact on the globe overall. It's all a big debate among strategists that won't be resolved until someone actually goes and tries it.
The complication is that any nuclear discourse carries major political overtones. It's not exactly that they're trying to scare the public. But the fundamental basis of nuclear deterrence and mutually assured destruction, the primary strategic doctrines of the Cold War, requires that nuclear use will always lead to escalation, which will always lead to humanity's destruction. If nuclear war would not lead to complete mutual annihilation, then deterrence can't possibly work.
And if deterrence doesn't work, and nukes don't result in armaggedon, then there is no incentive to not use them.
The strategists of the Cold War that proposed that nuclear weapons wouldn't destroy the world also tended to be the ones that wanted to use them. And yeah, there were a lot of them. There were many voices in the military and strategic community that wanted the US and USSR to incorporate nukes into regular war strategy. And quite a few legitimately supported a preemptive nuclear assault against the other country. There are recordings taken in the Oval Office during the Cuban Missile Crisis - Kennedy had stepped out for the moment, leaving the generals, who began congratulating each other into scaring Kennedy enough to finally give the order.
If that seems crazy, think about it this way: if deterrence doesn't work and you can survive a nuclear war, then obviously, whoever fires their nukes first will have the advantage. Meaning if you wanted to win a nuclear war, you needed to be that first shooter. Which is why saying nukes won't destroy humanity is a pretty controversial statement - not just because of the veracity of that statement, which is debated, but also because of implications of that geopolitically.
Anyway, TL

R - roundabout way of saying "Nobody knows for certain" if nukes will or will not kill off civilization, humanity, and/or all life on planet Earth.
We do know that we can't literally "destroy the world." People tend to underestimate just how massive this planet is - the entire surface of the planet, where all human life exists, is just of a tiny fraction of the planet's mass. We don't have anywhere close to the nuclear material required to even crack its shell. Life on Earth would be wiped out in any catastrophe long before this planet ever broke apart.