Australia: The Land Where Time Began

A biography of the Australian continent 

Pliocene Climate

In the Pliocene Epoch, the second of the 2 epochs making up the Neogene Period of the Cenozoic Era the cooling trend continued, though at a reduced rate. According to the author¹ the climate was still warmer than that of the present, and it reversed direction during the Middle Pliocene about 4 Ma with global average temperatures again increasing. The temperatures of the Pliocene peaked a bit more then 3 Ma during the Mid-Pliocene Warm Period (MPWP), that lasted for 300,000 years, the global temperatures reaching 2-3° C above the temperatures of the present. Much of the tundra that had become established during the earlier, cooler times was replaced by conifer forests during the MPWP, even in northern Greenland. There was no sea ice cover in the Arctic in the summer and the ice shelves of the Antarctic were much reduced. The author¹ suggests there are many possible causes for the MPWP, atmospheric CO2 levels close to those of the present are widely believed to be either the major, or at least one of the major drivers of the high temperatures. The MPWP is widely believed to be an equilibrium climate response to carbon dioxide levels similar to those of the present, suggesting that if the current levels of carbon dioxide are maintained for a long period the climate would eventually match the climate that prevailed during the MPWP. The author¹ suggests this would probably not mean that global average temperatures would be as high as during the MMCO, the global average temperature at least 2 C dangerous climate-change 'guardrail'. The evidence from the warmest parts of the Pliocene is suggesting the same as the climate models, that there will be less polar ice and higher sea levels. The volumes of ice at high latitudes and height of sea levels varied widely over the entire duration of the MPWP, the sea levels being 30 m above present levels at the height of the warming. This sea level would submerge all coastal cities in the world.

Cooling rapidly set in after the close of the MPWP, carbon dioxide levels and temperatures dropping. Carbon dioxide levels were down to 200 ppm or lower by the end of the Pliocene Epoch and Greenland was covered with ice and the glaciers of the Northern Hemisphere were expanding towards mid latitudes. Ice had spread across much of the European and Asian Arctic, Alaska and northeastern North America, and in only a few hundred thousand years. The global cooling trend that had begun almost 50 Ma in the Eocene had finally reached a point where a true ice age was triggered for the first time since glaciers first expanded out of the polar regions almost 250 Ma during the Carboniferous Period. Geologically speaking, the transition from a temperate world to an ice world took place rapidly, but the elements necessary to trigger an ice age had been accumulating for a prolonged time before, and when all the criteria were met there was sufficient accumulation of ice for the glaciers to expand out from the poles.

Sources & Further reading

  1. McGuire, Prof. Bill, 2012, Waking the Giant: How a changing climate triggers earthquakes, tsunamis, and volcanoes, Oxford University Press.


Author: M. H. Monroe
Last updated 25/08/2012

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