the cataclysm touched off by an asteroid

That smudge corresponds with a meteoric rise in the amount of carbon dioxide in the air,now beyond 400 parts per million,or higher than any other Homo sapiens has ever breathed.Similar soot can still be found in ancient rocks from volcanic fires of 66 million years ago,a record of the cataclysm touched off by an asteroid at the end of the late Cretaceous epoch.