The natural evolution of the Sun made it gradually more luminous during the Archaean and Proterozoic eons. The Sun's luminosity increases 6% every billion years. As a result, the Earth began to receive more heat from the Sun in the Proterozoic eon. However, the Earth did not get warmer. Instead, the geological record seems to suggest it cooled dramatically during the early Proterozoic. Glacial deposits found on all cratons show that about 2.3 Ga, the Earth underwent its first big ice age (the Makganyene ice age). Some scientists suggest this and following Proterozoic ice ages were so severe that the planet was totally frozen over from the poles to the equator, a hypothesis called Snowball Earth. Not all geologists agree with this scenario and older, Archaean ice ages have been postulated, but the ice age 2.3 Ga is the first such event for which the evidence is universally accepted. 

The ice age around 2.3 Ga could have been directly caused by the increased oxygen concentration in the atmosphere, which caused the decrease of methane (CH) in the atmosphere. Methane is a strong greenhouse gas, but with oxygen it reacts to form CO, a less effective greenhouse gas. When free oxygen became available in the atmosphere, the concentration of methane could have decreased dramatically, enough to counter the effect of the increasing heat flow from the Sun.

Proterozoic eon
हिमाच्छादित पृथ्वी आणि ओझोन आवरणाची उत्पत्ती
हेडिअन आणि आरकीअन
सजीवसृष्टीची सुरुवात