Another way to influence climate: comet impact

In addition to (pay attention now) melting enormous glaciers and starting continent-wide fires, a comet impact 12,900 years ago brought about a cold spell that wiped out the North American megafauna and began a new cooler climatic period. This is The Day After Tomorrow syndrome. Funny they would leave the comet out of the movie. And the fires. And the melting.

Did a comet wipe out prehistoric Americans?

The Clovis people of North America, flourishing some 13,000 years ago, had a mastery of stone weaponry that stood them in good stead against the constant threat of large carnivores, such as American lions and giant short-faced bears. It's unlikely, however, that they thought death would come from the sky.

According to results presented by a team of 25 researchers this week at the American Geophysical Union meeting in Acapulco, Mexico, that's where the Clovis people's doom came from. Citing several lines of evidence, the team suggests that a wayward comet hurtled into Earth's atmosphere around 12,900 years ago, fractured into pieces and exploded in giant fireballs. Debris seems to have settled as far afield as Europe.

Jim Kennett, an oceanographer at the University of California, Santa Barbara, and one of the team's three principal investigators, claims immense wildfires scorched North America in the aftermath, killing large populations of mammals and bringing an abrupt end to the Clovis culture. "The entire continent was on fire," he says.

The fires and general chaos would help to explain why it's so hard to find the ruins of Hyborea and Tep's Town.