If it happened in the last 100,000 years, it might be
possible someday to extract traces of its effects from deep within the
polar ice
caps.
Now, if you have all this very cold, nearly freezing water surrounding these ice
caps, sucking up carbon dioxide out of the
polar atmosphere, at nearly the highest
possible rate, 30 times faster than oxygen, and 70 times faster than nitrogen, doesn't it stand to reason that the air that remains might just have a lot less carbon dioxide in it than the atmosphere across the rest of the planet?