It is common to assume the comet strike kicked off the Younger Dryas cold spell, but it could still have been a coincidence. There were other cold spells like i

It is common to assume the comet strike kicked off the Younger Dryas cold spell, but it could still have been a coincidence. There were other cold spells like it in previous interglacials, and we don't know what caused those. Those might also have been caused by comet strikes; it took us long enough to identify this one. What happens that takes a thousand years to clear up is another mystery on the pile. We know with certainty there was a comet strike, about the right time, that caused serious havoc, but evidence that it changed the climate is harder to establish. Firm evidence of sharply falling global temperature before the strike would settle the question. If the strike really did precede the cold spell, it may be hard to prove causation. It seems like the way to bet. Another mystery is how the conflagration spared (just) bison, moose, deer, elk, pronghorn, and grizzly and brown bears.