What is this device on the nose of a Bombardier Global 6000?
That is the sensor for the aircraft's Enhanced Vision System (EVS) - a combination of a visible low light and infra red video cameras which are combined together via computer into a composite image for display on either the PFDs or HUD in the cockpit.  It provides better situational awareness in poor visibility and during night operations for the crew.  See demonstration video here, and a video for how it can light up high terrain here (frame below):