I am writing a theory for a game that is in an apocalypse. An asteroid is heading for earth and will crash into the earth regardless in this theory. It is 1km in size but due to the YORP effect it has broken apart (it has a fragile composition because it's carrying something dangerous within it). It is now a group of rocks with the largest being 300m in diameter.
I've read that as a meteor reaches earth and either hits or burns up, it releases a lot of energy. This obviously means that it gives off heat into earth's atmosphere. If a 1km asteroid that has broken up into pieces were to hit earths surface, they would probably release a lot of heat too.
Considering that an asteroid of 300m size has never been recorded to hit earth in our time, it could be assumed that a lot of heat is released by its impact. It may also trigger events like volcanic eruptions and a kick up of lots of dirt to block out the sun in the area that it hits.
Oh yeah, I forgot to add that the velocity of this asteroid is supposed to be 31 km/s. Super fast to punch through atmosphere.
Would an impact of an asteroid of 1km (that breaks up) be enough to change the normal temperature of earth when taking into consideration all the side effects that the asteroid would cause?