What It Takes to Melt Antarctica

Posted on December 4, 2011

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At the end of the Eocene Epoch, 34 million years ago, something caused the atmospheric carbon to fall by 40%, nobody really knows what.  When the concentration of CO2 dropped below 600 parts per million, ice sheets began to form in Antarctica.  Until that time mammals, and even some reptiles and amphibians, had lived at the earth’s poles.

The figure of 600 parts per million was arrived at by scientists from Yale and Purdue Universities after careful study of ancient algae found in deep-sea core samples.  The present study corrects inaccuracies and conflicting results from previous studies by focusing on continuous data from a stable area of the ocean.  Previous inaccuracies had crept in because samples from different areas didn’t sufficiently account for variations in local conditions.

The study incidentally affirms for the umpteenth time—for those who still need such an affirmation—the clear connection between CO2 and climate change.

Today our climate is heading in the opposite direction, warming not cooling, with carbon dioxide at 390 parts per million and rising.  If present trends continue, CO2 levels will likely reach somewhere between 550 and 1000 parts per million by 2100.

The 6oo ppm figure is suggestive only at this point.  The threshold for melting of the Antarctic ice sheets might not be the same as the threshold for their formation since the processes involved aren’t necessarily symmetrical going both ways.

However, it’s looking increasingly likely that somewhere in this century, with temperatures rising drastically in response to atmospheric carbon, the Antarctic ice sheets will start a serious melt.  And past a certain point we won’t be able to stop it.

A study earlier this year concluded that the collapse of the Greenland ice sheets will occur somewhere between 400 and 560 ppm.  We’re only a whisker away from the bottom end of that range already.

The melting of the vast polar ice sheets would ultimately contribute 200 feet of sea level rise from Antarctica, 20 feet from Greenland.  This would take centuries to happen, however hot it becomes, but even one or two percent of these sea level rises in the next century would be disastrous, and once the melting is underway it is difficult to see what could be done to stop it.

Unless we want to adapt to a severely shrunken world changed beyond recognition, the only solution is preventative.  Our civilizaion simply can’t afford to keep on tossing its carbon into the atmosphere as if the laws of physics didn’t apply to us.

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See 

Drop in Carbon Dioxide Levels Led to Polar Ice Sheet, Study Finds – Science Daily

Drop in CO2 Levels Led to Antarctic Ice Sheet, Study Finds – Climate Progress

Antarctic Journal of the US, Jan. 1998