From this report:
No one has found a giant crater in the Earth that could attest to such a cataclysmic impact 13,000 years ago, but the research team offers evidence of a comet, two and a half to three miles in diameter, that detonated 30 to 60 miles above the earth, triggering a massive shockwave, firestorms and a subsequent drastic cooling effect across most of North America and northern Europe....
The magnitude of the detonations would have been huge.
“A hydrogen bomb is the equivalent of about 100 to 1,000 megatons,” Bunch said. “The detonations we’re talking about would be about 10 million megatons. That’s larger than the simultaneous detonation of all the world’s nuclear bombs past and present.”
That's a lot of energy.
But let's not spend a paltry million dollars a year to help track down dangerous space objects heading our way, hey Peter McGauran. Just keep looking after the horsies with a $110 million plus assistance package.
I still think the horses are faking it for a rest. Go get a real job, horse people.** Readers are advised that this blog has an official policy of encouraging irrational dislike of horses.