[jacquesm]

Yes, it is the difference between a sterilization level event and one that is probably survivable. But it would still be the most significant impact in all of recorded history and to get to a larger one you'd have to go back a long, long time.

[throwbadubadu]

Even a 400m land hit sounds pretty survivable for whole humanity, significant climate impact is expected beyond the 1km range?

[jacquesm]

Yes, it would be survivable for humanity. But depending on where it would happen, how dense the impactor is and at what speed it is traveling the effects would nevertheless be quite serious. Imagine NYC or SF taken out like this (of course the chances of that happening are really small given their area relative to the total of the planetary surface):

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/201...