A full-scale thermonuclear war would have had lots of unintended consequences. We are not in a good position to decide whether everybody would be killed. To help us decide that we have a sample of size zero.
Predicting complex systems, very often we are wrong. In as simple a question as whether an airliner accident would cause WTC to collapse, everybody who tried to predict it got it wrong.
I would guess that a sheepherder in paraguay who has never seen many effects from the industrial revolution ought to be minimally affected. He shouldn't get much radiation unless somebody intentionally uses cobalt bombs or such. He should be able to live just fine without new steel knives and such. I guess there would be no subtle interactions that would kill him, and I have no basis for that guess except my lack of imagination.
We could certainly design a nuclear war to kill everybody. It's called a doomsday device, and it would be possible to make one that was fairly certain to be effective. The question of just how small a full-scale thermonuclear war would have to be to not kill everybody, is not something we can estimate with any degree of certainty without repeating the experiment enough times to get a decent sample size.
Why would we think we know the answer to this question? If we could reasonably predict whether a full-scale nuclear war would kill everybody, why can't we design a warplane from scratch and build it from untested plans and have it fly correctly the first time?
I would guess that a sheepherder in paraguay who has never seen many effects from the industrial revolution ought to be minimally affected. He shouldn't get much radiation unless somebody intentionally uses cobalt bombs or such. He should be able to live just fine without new steel knives and such. I guess there would be no subtle interactions that would kill him, and I have no basis for that guess except my lack of imagination.
Unless he's part of a subsistence community (and even in underdeveloped countries most agrarian workers are not,) he's still economically tied to industrialized civilization. He's still directly or indirectly dependent on a consumer market that's now gone.
Today is September 26th, Petrov Day, celebrated to honor the deed of Stanislav Yevgrafovich Petrov on September 26th, 1983. Wherever you are, whatever you're doing, take a minute to not destroy the world.
The story begins on September 1st, 1983, when Soviet jet interceptors shot down a Korean Air Lines civilian airliner after the aircraft crossed into Soviet airspace and then, for reasons still unknown, failed to respond to radio hails. 269 passengers and crew died, including US Congressman Lawrence McDonald. Ronald Reagan called it "barbarism", "inhuman brutality", "a crime against humanity that must never be forgotten". Note that this was already a very, very poor time for US/USSR relations. Andropov, the ailing Soviet leader, was half-convinced the US was planning a first strike. The KGB sent a flash message to its operatives warning them to prepare for possible nuclear war.
On September 26th, 1983, Lieutenant Colonel Stanislav Yevgrafovich Petrov was the officer on duty when the warning system reported a US missile launch. Petrov kept calm, suspecting a computer error.
Then the system reported another US missile launch.
And another, and another, and another.
What had actually happened, investigators later determined, was sunlight on high-altitude clouds aligning with the satellite view on a US missile base.
In the command post there were beeping signals, flashing lights, and officers screaming at people to remain calm. According to several accounts I've read, there was a large flashing screen from the automated computer system saying simply "START" (presumably in Russian). Afterward, when investigators asked Petrov why he hadn't written everything down in the logbook, Petrov replied,"Because I had a phone in one hand and the intercom in the other, and I don't have a third hand."
The policy of the Soviet Union called for launch on warning. The Soviet Union's land radar could not detect missiles over the horizon, and waiting for positive identification would limit the response time to minutes. Petrov's report would be relayed to his military superiors, who would decide whether to start a nuclear war.
Petrov decided that, all else being equal, he would prefer not to destroy the world. He sent messages declaring the launch detection a false alarm, based solely on his personal belief that the US did not seem likely to start an attack using only five missiles.
Petrov was first congratulated, then extensively interrogated, then reprimanded for failing to follow procedure. He resigned in poor health from the military several months later. According to Wikipedia, he is spending his retirement in relative poverty in the town of Fryazino, on a pension of $200/month. In 2004, the Association of World Citizens gave Petrov a trophy and $1000. There is also a movie scheduled for release in 2008, entitled The Red Button and the Man Who Saved the World.
Maybe someday, the names of people who decide not to start nuclear wars will be as well known as the name of Britney Spears. Looking forward to such a time, when humankind has grown a little wiser, let us celebrate, in this moment, Petrov Day.