"We stand today at a crossroads: One path leads to despair and utter hopelessness. The other leads to total extinction. Let us hope we have the wisdom to make the right choice."
~ Woody Allen
Posted: 09 Apr 2012 03:42 PM PDT
The last time carbon dioxide levels were apparently as high as they are today — and were sustained at those levels — global temperatures were 3 to 6 degrees Celsius higher than they are today, the sea level was approximately 25 to 40 metres higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland.
One impact is ocean acidification (increasing atmospheric carbon dioxide is well-mixed with the ocean, to form carbonic acid and thus increasing water acidity) and rising ocean temperatures. Given that carbon dioxide emissions over the next two decades are being determined (more than we would wish!) by existing energy infrastructure, we are not far from disaster:
So the big question is how far we are from triggering large-scale permafrost release.
The take-home message is that current levels of atmospheric carbon dioxide are probably sufficient to trigger large-scale permafrost carbon feedbacks and global warming that human effort would be unable to contain.
And now comes a new study which shows a sudden and extreme global warming events 55 million years ago known as the Palaeocene–Eocene Thermal Maximum (PETM) is characterized by a massive input of Antarctic permafrost carbon, ocean acidification and an increase in global temperature of about 2 degrees Celsius within a few thousand years. The study's author, Rob DeConto, says the implications of the study appear dire for the long-term future as polar permafrost carbon deposits have begun to thaw due to burning fossil-fuels:
Similar dynamics are at play today. Global warming is degrading permafrost in the north polar regions, thawing frozen organic matter, which will decay to release CO2 and methane into the atmosphere. This will only exacerbate future warming in a positive feedback loop.