Savannah is the answer you are looking for here.
If there was a sudden drop in temperature after the evolution of the
first living cells, the rate of fermentation would drop due to the
temperature. My prediction would have to include the data, which is on
the graph. The question does not include a temperature to base my
hypothesis on so I would have to conclude that if the temperature
suddenly dropped to 35ºC to -20ºC, that the initial cells would die, and
that the atmosphere and the evolution of cyanobacteria would change
drastically.
