There are other possible extiction level events. A nearby supernovae could send a wave of lethal radiation towards us, stripping the protective ozone layer from our planet, indeed it has been suggested that this may have happened before. Closer to home, the eruption of a Supervolcano might make all our worrying about mankind's effect on the climate totally irrelevant.
|Part of a massive tabular iceberg adrift in the Weddell Sea off the Antarctic peninsula. In Antarctica, the recent break-up of ice shelves has precipitated increased streaming of ice from much farther inland, which potentially represents the initiation of a phase of much more serious ice-sheet collapse.|
We can do little about the most of the external threats to the continuation of our species, at least for now. Maybe in a few hundred years, if we get lucky enough to make it that far, then we will have the technology to address at least some of them. But Jan Zalasiewicz's recent article in The Guardian suggests we might not have those few hundred years.
I'd recommend people read it, it scared me badly, and like geologists, astronomers don't scare easily. We're used to thinking about the world coming to an end, and maybe you should be thinking about it as well.