Well, according to the calculator, nothing major happens on a global scale. The collision would be survivable by many in a city.
This is accounting for a 1,000 ft IRON meteor coming in at 50 degrees (most likely is 45) hitting ANY area.
Why are we worried now?
bump to myself. This is a classic FReeper thread if I ever saw one. Of course, we'll all be dead of Avian Flu or Marburg before any asteroids cleanse the planet.