Reducing atmospheric pressure on Snowball Earth

• A Snowball Earth is a global condition (which may have occurred many times) in which the temperature everywhere on the surface was, for extended periods (up to tens of millions of years), below the freezing point of water.

• It occurred both before and after photosynthesis radically transformed the primordial atmosphere to the nitrogen, oxygen, carbon dioxide balance we know today. On the occasions after, the oxygen production was diminished due to reduced plant activity in the cold spells.

The starting point is that the at-sea-level pressure is (about) three times that of Earth. There is unicellular life in reach of light, some multicellular by ocean vents.

Enough background.

_{After the oxygen generation occurred}

What event (be it astronomical, solar, geological, biological or specified "other") could result in the atmospheric pressure at sea level dropping by half in less than 20 years? (The faster the better.)

Caveats: Without destroying all life on the planet. The best answer should be closest to banal and everyday by way of explanation. Aliens harvesting the atmosphere, or Gods replenishing their pet planet in the next system over would be least likely to be approved of. Heating of the planet would be fine as long as the mean temperature after 20 years doesn't exceed the boiling point of water.

_{I assume that the tags as chosen are not mutually exclusive, if they are, please edit as appropriate.}

posted almost 6 years ago

Mr Bumble‭

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