I was in the middle of answering this newly asked question when it was deleted by the author. It had been up for 30 minutes.
I can't read the OP's mind, but I suspect the question was closed because challenges were being made to the back story. To wit, the OP's premise of using current or near-future nuclear weaponry would not result in 90% deaths.
The problem, of course, is that such an observation is fundamentally irrelevant. The OP's question was how long it would take for the world to recover to some specified conditions after the event?
It's something of a tradition on Worldbuilding.SE to challenge the back story to a question. So much so that I've occasionally recommended that an OP remove the back story completely so that people would stop challenging it and focus on the question the OP actually asked. That, unfortunately, results in people complaining that the back story wasn't provided, as if the back story was more important than the question.
In most cases, I think, the challenges are provided in a way that's beneficial to the OP. Something along the lines of "as you work through this issue, you might want to consider the following weakness in your back story." But I don't believe that happened in the referenced case. And it's unreasonable to believe the brand-spanking new user (literally!) could possibly understand the culture and rules of the site.
Result? The OP deleted the question. I voted to undelete it.
What should be our site's policy for handling issues involving the back story to a question?
Should we flag comments that fail to remind the OP that the observation is just that, an observation, and not an issue for the question itself and not at all a reason to edit or delete the question?
Should we judge the back story equally with the OP's actual question? In other words, if we believe the back story can't support the question, is it permissible to ignore the question and vote/comment based only on the back story?
Is there an in-between compromise I'm not seeing?
I've been frustrated over the years by users who believe the back story is equally important with the question. Frankly (and simplistically for the purposes of this presentation), "How long would it take for Earth civilizations to recover to [this end condition] given [this starting condition]" shouldn't have any discussion based on the backstory used to establish [this starting condition] at all. Who cares if the nuclear arsenal available to us today is insufficient for achieving a 90% mortality rate?
Honestly, how many of us have grown up with the concept of "the world's nuclear arsenal can destroy the world X times over!" I don't know the OP's age and expecting them to realize that no arsenal would be used to evenly blanket the Earth might be a massive presumption.
I consider this issue an extension of the site's unwritten and too-often-used culture of assuming that whatever science we know today is the heaven-written truth, ineffable and immutable, and that there will never be more science or better science in the future. (I'm on a bit of a rant, but I know too many people who boisterously proclaim their atheism and disdain for religion — all the while treating science with the same blind faith they accuse the followers of religion of having.) The OP tried to make it clear that his proposal was for the near future (2070-2080).
Considering that 99.9% of the world's technology was invented in the last 150 years and that 99.9% of the worlds nuclear technology was invented in the last 100 years — the assumption that a nuclear arsenal 50–60 years from now couldn't kill 90% of the inhabitants is hubris bordering on rampant arrogance.
Consequently, my opinion is that I have little patience for driving away a new user for something as inane as a theoretical weakness in the back story.
<Rant mode: off><grateful for patience mode: on>
Comments made about this answer led me to what I believe is a really great way to help people know when it's appropriate to challenge the backstory.
- Remember to address the question, not the backstory. Unless you're sure the reason for the question will change the answer, focus only on the question and enjoy the creativity of the backstory.
An example of a backstory that shouldn't be challenged (except, perhaps, in comments)
Q: On my world the atmosphere is tainted such that it appears bright magenta during the day. My question is this: how would seafarers navigate during the day?
A Frame Challenge suggesting that what makes the sky magenta affects the answer would be specious in that it's true the OP hadn't defined what caused the atmosphere to be magenta, but it's actually irrelevant to the question. The color of the sky does not affect sea navigation.
An example of a backstory that could be challenged
Q: On my world the atmosphere is tainted such that it appears bright magenta during the day. My question is this: what color would the horizon be with the setting sun?
A Frame Challenge would be appropriate for this second example because what causes the sky to appear magenta during the day could affect the color of the sky when the sun sets. (It should be noted that it would be more appropriate to ask in comments for additional details including what makes the sky magenta... but an appropriate Frame Challenge could suggest that it's impossible to have an inhabitable world with a magenta sky, so asking the question is irrelevant.)