980 meters mean it will be a regional disaster, not a global one. Not big enough. It would kick up enough dust globally to rival some pretty massive volcanic explosions, but nothing serious in that effect.
There's still the matter of asteroid 2004 MN4 to deal with in 2036.
Beg to differ. Comets are moving faster (in general) than asteroids, and have much more energy. Also,
980 meter = 0.6089438 mile
This would indeed cause a major and worldwide disaster; the Chicxulub impactor was in the area of 10 km (10 kilometer = 6.2137119 mile), something more than 1000 times the size (assuming more or less spherical, 10 ^ 3) of this comet (as far as is known; exact dimensions of this "new" comet are not yet known, but it doesn't seem very likely to increase tenfold, either), moving 10 to 20 km a second. The eleven largest nuclei of SL-9 (the shattered comet which struck Jupiter in 1994) were each between 2 and 4 km in diameter.
http://www.onlineconversion.com/length_common.htm