Two and a half billion years ago, before the Earth's atmosphere contained appreciable oxygen, photosynthetic bacteria gave off oxygen that first likely oxygenated the surface of the ocean, and only later the atmosphere.

"The sulfur isotope change we recorded coincided with the first known anomaly in the carbon cycle. This may have resulted from the diversification of photosynthetic life that produced the oxygen that changed the atmosphere," Kaufman said.

Once oxygen made it into the atmosphere, the scientists suggest that it reacted with methane, a powerful greenhouse gas, to form carbon dioxide, which is 62 times less effective at warming the surface of the planet. "With less warming potential, surface temperatures may have plummeted, resulting in globe-encompassing glaciers and sea ice" said Kaufman.