It's weird to see these two accidents grouped like that, given how they differed in severity.

Those are the only two Level 7 nuclear events (the highest severity) to occur in history so I think it makes sense to group them together.

I should have been clear that I was describing perception, not reality. :)

Global warming, however, can.

I'm pessimistic but the only way that can end the world is if we really want to. It would be very similar to a nuclear war. At some point you have caused so much damage there is no point in further fighting. The only reason why the world would end at that point is that the remaining people want it to end at all costs.