IMO, if an asteroid is to take out the Earth, it has yet to be discovered and will almost literally come from nowhere. Scientific calculations today on known asteroids can pretty accurately determine orbit etc.
It could be discovered tomorrow, or conversely, not for 1000 years.
All we have to do is buy carbon credits from manbearpig and he’ll make it all go away.
Didn't they (astronomers) discover one just last summer only days before it passed in-between the Earth and the Moon?
I don't think is was an extinction-sized asteroid, but more of a city-killer, like the Russian asteroid from the turn of last century.