In 2009 they were considered to be at the tipping point where the methane releases caused warming which caused more releases, without added AGW. One person in the article says it has never happened before, but it has, 1/10th as fast, and with less total CH4 than now, and caused a 30% extinction and 16*F temperature rise, with 150-180,000 years to resequester the CH4 and 2 million years to return the number of species that there were before it happened.http://www.wunderground.com/climate/PETM.asp
The bubble may be wondrous to look at and fun to light, but the giant ones indicated are not a good thing to have releasing. The polar ice cap shrinking is also causing the ocean to warm, and along with the tundra and shallow arctic lake methane warms the ocean(from atmospheric warming) to depths of huge methane hydrate deposits which release. Deeper and deeper, until it is all released or turned over.
It is estimated from all I have read to be so much faster and worse than PETM to cause up to a 29*F temperature rise and 87% extinction level within 1500 years and possibly as little as 300 years. The time to resequester will be much longer (200K yrs.+)and species lost back to previous levels also much longer(3 million yrs.+).
The difference in "AETM" and PETM is that the event 55 million years ago was after thousands of years of increased vulcanism with seismic mechanical oceanic releases of CH4. The event starting is all from human causes of mainly fossil fuel burning.
The last time one species caused an ELE was when cyanobacteria waste produced our oxygen atmosphere and it killed most of them off like yeast getting killed by their own alcohol in fermentation. It was a good thing then, because it lead to animal life and us.
Crossing the methane hydrates self release tipping point of positive feedback is not a good thing and once established can not be stopped. Hansen said in 2006 that we had 10 years to reduce fossil fuel burning 90%. Others have reported a 50% chance of stopping it with an 80% reduction in HGHGs by 2020. It must be noted that increasing HGHGs are proportional to overpopulation and increasing standards of living/consumption. 30% of HGHGs are from slash and burn agriculture with 3% from agricultural animal produced methane. Some add that much of the fossil fuel burning is for mechanized agriculture, processing and distribution, to the point of agriculture to feed the overpopulation contributing 50% of the HGHGs.
It is unfortunate that the inevitable population crash from a group of increasing factors, will hit a peak around the late 2040s and not before 2020. It is very doubtful people will reduce their emissions enough in time to prevent the completion of this positive feedback loop which then can not be stopped and will result in ecocide.
In the end, so called intelligent humans are no smarter than yeast in a bottle of sugar water. On average, of course.
Even climate scientists don't want to look at it;http://www.skepticalscience.com/climate ... -esld.html
From the article:
"Permafrost Melt and Carbon Feedback
The Copenhagen Diagnosis notes that the global warming amplification (feedback) from carbon released as a result of permafrost melting has not been accounted for in any of the IPCC projections. A recent UN Environment Programme report warned that failing to account for this feedback will result in an underestimate of future warming."
More on that;http://www.ipsnews.net/2013/02/thawing- ... l-warming/