The ice age !!

It is said that the last ice age was a result of sudden growth of oxygen in the earths amosphere!!

The lack of greenhouse gasses due to trees and plants, the earths atmosphere chilled at high rate producing huge ice sheets from the poles of the planet.

"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.

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 first formed oxygen reacted with iron in the oceans, creating iron oxides that settled to the ocean floor in sediments called banded iron-formations - layered deposits of red-brown rock that accumulated in ocean basins worldwide.

Later, once the iron was used up, oxygen escaped from the oceans and started filling up the atmosphere.

The evolution of organic photosynthesis ca.2.5 billion years ago would have had a profound effect on Earth's surface environments, and potentially on aerobic respiration by eukaryotes.

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.

If you think you dont believe in ice age, well , evidences for ice ages are there too.

There are three main types of evidence for ice ages: geological, chemical, and paleontological.

Geological evidence for ice ages comes in various forms, including rock scouring and scratching,glacial moraines,drumlins, valley cutting, and the deposition of till or tillites and glacial erratics. Successive glaciations tend to distort and erase the geological evidence, making it difficult to interpret. Furthermore, this evidence was difficult to date exactly; early theories assumed that the glacials were short compared to the long interglacials. The advent of sediment and ice cores revealed the true situation: glacials are long, interglacials short. It took some time for the current theory to be worked out.

The chemical evidence mainly consists of variations in the ratios of isotopes in fossils present in sediments and sedimentary rocks and ocean sediment cores. For the most recent glacial periods ice cores provide climate proxies from their ice, and atmospheric samples from included bubbles of air. Because water containing heavier isotopes has a higher heat of evaporation, its proportion decreases with colder conditions. This allows a temperature record to be constructed. However, this evidence can be confounded by other factors recorded by isotope ratios.

The paleontological evidence consists of changes in the geographical distribution of fossils. During a glacial period cold-adapted organisms spread into lower latitudes, and organisms that prefer warmer conditions become extinct or are squeezed into lower latitudes. This evidence is also difficult to interpret because it requires

(1) sequences of sediments covering a long period of time, over a wide range of latitudes and which are easily correlated;

(2) ancient organisms which survive for several million years without change and whose temperature preferences are easily diagnosed; and

(3) the finding of the relevant fossils, which requires a lot of luck.

Maybe if all the resources of earth get dimnished and the green house gasses will occupy very less percent of atmosphere leaving the remaining to oxygen, will ice age as predicted by geologists begin ?