The consequences?? well, the people at ground zero are vaporized. Like what happned to the vast majority of people who perished on 9/11.

Nuclear explosions produce both immediate and delayed destructive effects. Immediate effects (blast, thermal radiation, prompt ionizing radiation) are produced and cause significant destruction within seconds or minutes of a nuclear detonation. The delayed effects (radioactive fallout and other possible environmental effects) inflict damage over an extended period ranging from hours to centuries, and can cause adverse effects in locations very distant from the site of the detonation. These two classes of effects are treated in separate subsections.

The distribution of energy released in the first minute after detonation among the three damage causing effects is:

Low Yield (<100 kt) High Yield (>1 Mt)
Thermal Radiation 35% 45%
Blast Wave 60% 50%
Ionizing Radiation 5% 5%
(80% gamma, 20% neutrons)

The radioactive decay of fallout releases an additional 5-10% over time.

Source

There was a time, when we Americans thought a Nuclear Exchange was a survivable thing. but then the tonnage was much less than now

have another source of information regarding the end of the world. Yep. dubya actually has the Nuclear Option on the Table for Iran. and our top Military leaders are threatening to resign if it remains.

Even the WaPo is covering this story

I am not even going to ask my dad what he thinks about this. I already know.