The tag whose name I hate, event-based-effects is the tag for these. We can have an opinion on just how short term or widespread these effects need to be, I suppose. I would like to close these questions as obsolete when they are over, but I don't believe we have that as a reason at the moment.
There are only 19 questions with that tag right now. I think worries about leaky nuclear reactors, revolutions, invasions, and Ebola are legitimate questions to ask here and tag with that. They cover entire countries (in the mind of the asker; often the answer is of the form "that only matters if you're in this area of this city") and the risks involved are serious, including dying. Worries about delay because of a one-day strike are less legitimate, in my opinion. We don't have a good "too localized - not useful to anyone else" reason to trot out for these.
Our three custom close reasons are
- price-shopping for specific goods or services
- constructing travel and tour itineraries
I would really like to add these two (even though I actually want the system as a whole to have them.) See https://travel.meta.stackexchange.com/a/1401/46. If we drop immigration because the site now exists, so we can use "belongs on another site in the network", we could add Obsolete. In a pinch, we could close some event-based-effects questions as obsolete the moment they were asked - our wording could be something like "new answers are no longer possible or no longer useful to new readers".