Hes psychic though remember his crystal ball?Idk.. A lot of shinobi can sense immense amount of Chakra..
but u r right.. Kakashi realized there was something odd going on, and the more aware Hiruzen must've known it before Obito summoned the Kyuubi.
Didn't he also sniff out the First and Second Hokage when he was fighting them in that darkness genjutsu?
Hes psychic though remember his crystal ball?
Lmao, I'd think not. There was a disturbance in the force...xd
So Kakashi is a sensor because he felt in a chill in the air?
Nope.