Command and Control by Eric Schlosser covers many close call nuclear incidents that the US military has had since WWII. The incident which has been seared into my memory is one where an aircraft carrying a nuclear bomb flying over the east coast of the US had a critical engine failure which resulted in the crew bailing out. After the crew bailed out, an object in the cockpit inadvertently armed and dropped the bomb as the aircraft disintegrated. The only thing that prevented the eastern seaboard of the US (including Washington DC and New York City) from being irradiated with fallout was a failsafe switch which prevented a circuit from being completed in the bomb.
It is a wonder that we (still) haven't blown ourselves up yet.
I completely agree that it is amazing we have not blown ourselves up yet. Unfortunately, the risk of a nuclear exchange is only rising...
stress of climate change + 7 billion people + human nature == war (very possibly nuclear)
Nuclear weapons have proliferated from just the US having access, then to only a few super powers, to now 8 or 9 countries. That list will only go up over time, not down. The weaponization of nuclear technology is the first time our species created something that is outright able to kill us all (or most of us).
In the short period of time we have had access to nuclear weapons, we have come very close to nuclear war between superpowers:
* Cuban Missile Crisis - Vasili Arkhipov prevents launching of nuclear torpedo while his Soviet submarine flotilla is being bombarded by depth charges (happened to be signaling depth charges). Turns out the US warships above them just wanted the submarines to surface so they could communicate the end of hostilities. https://en.wikipedia.org/wiki/Vasili_Arkhipov
* Computer Malfunction - Stanislav Petrov holds off alerting officials of multiple incoming nuclear ICBMs because he "suspected" they were a glitch, preventing a likely nuclear counter-attack. https://en.wikipedia.org/wiki/Stanislav_Petrov
* Science experiment looks like nuclear attack - Boris Yeltsin correctly decides to wait launching a counter-attack based on an incoming rocket. All the while sitting in front of an activated nuclear briefcase and being pressured by aids to launch within the 12 minute response window. The rocket was meant for atmospheric testing. https://en.wikipedia.org/wiki/Norwegian_rocket_incident
* Many, many more... (your example just being one)
Now throw in the ramifications of climate change like political instability, infrastructure strain, resource scarcity, and refugee migrations into the mix.
The more horrifying truth from that book is that time and again, for decades, the military actively blocked the implementation of safety measures. They were concerned about the small increase in chance that a bomb would fail to detonate when intended.
It depends on what the circumstances are. If communications are disrupted, nuclear forces on alert could mistake it for an attack and launch in retaliation. Daniel Ellsburg's new book details how launch authority, as a practical matter, was delegated to commanders in the field. If they thought that a war had started and they had no communications with their superiors, they would have had authority to launch on their own.
The problem is that one bomb going of could rapidly lead to 100's - who is to say it's an accident and not a strike? Wouldn't the enemy pretend it was an accident? Why are they moving forces now? (because they realise that a bomb just went off...)
It is a wonder that we (still) haven't blown ourselves up yet.