Methane feedbacks Subcap Methane Seeps Jan 2013 provides good coverage.

The trouble with Arctic feedbacks is that they are positive (bad), increasing the global warming that causes them, there are many of them, they are all potentially extremely large, and they lead to catastrophic runaway global heating.

David Wasdell covers the situation in Arctic Dynamics.

The risk from Arctic methane is enormous as determined in the 2011 paper Strong atmospheric chemistry feedback to climate warming from Arctic methane emissions. Indirect warming from methane results in a 250% increase in the methane emissions direct warming for a 2.5 fold increase in atmospheric methane. Methane inthe atmosphere is oxidized to other GHGs and methane has its own internal feedback whereby the higher its atmospheric concnetration the lohegr it lasts i the atmisogeer as methane.

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Dr. Mark Serreze, Director of the National Snow & Ice Data Center, describes the Arctic as our early warning system because of runaway feedbacks (video).

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"These (Arctic) positive physical and biogeochemical feedbacks can, with high probability, cause a change in state over a period of 20 to 30 years in terrestrial ecosystems climate forcing that is potentially 2–3 times greater than is the change in radiative forcing from fossil fuel burning." (Boreal/Arctic-Climate Positive Feedback and Abrupt Climate Change, US IMPACT Project)

Intergovernmental Panel on Climate Change (IPCC), 2007:

"Methane is stored in the soils in areas of permafrost, and warming increases the likelihood of a positive feedback in the climate system via permafrost melting and the release of trapped methane into the atmosphere.

"Both forms of methane [permafrost and methane hydrate] release represent a potential threshold in the climate system. As the climate warms, the likelihood of the system crossing a threshold for a sudden release increases. Since these changes produce changes in the radiative forcing through changes in the greenhouse gas concentrations, the climatic impacts of such a release are the same as an increase in the rate of change in the radiative forcing."

What is a Positive Feedback? 

National Snow and Ice Data Center (NSIDC):

"In the climate system, a positive 'feedback loop' refers to a pattern of interacting processes where a change in one variable, through interaction with other variables in the system, reinforces the original process (positive feedback)."

The executive summary of the 2009 WWF report, Arctic Climate Feedbacks: Global Implications, lists and covers the essentials of all these feedbacks. (Link to pdf below.)

As this 2009 Nature article reports, over the past few years it has become clear that "as the planet warms, vast stores of methane — a potent greenhouse gas — could be released from frozen deposits on land and under the ocean, making Arctic methane feedbacks a ticking time bomb."

No region compares to the Arctic for the degree of total potential feedback. Global warming is causing the Arctic to warm faster than anywhere else on the planet. This induces several Arctic changes, which then increase regional and global warming. In the Arctic, these changes make for multiple, inter-reinforcing (cascading, synergistic) feedback effects. These effects could, and we must assume would, lead to runaway global warming.

Arctic Positive Climate Feedbacks

There are two types of positive climate feedbacks in the Arctic: sea ice loss and carbon feedbacks.

1. Loss of Arctic albedo
a) Summer sea ice extent / loss of reflective (cooling) albedo:
The Arctic summer sea ice loss has passed its tipping point. This is a very large feedback, described by James Hansen et al in 2007 as an "albedo flip" that can unleash a planetary "cataclysm."
b) Replacement of (lighter) tundra with (darker) forests
c) Black carbon (soot) pollution on snow

2. Carbon CO2 feedbacks
a) Increased CO2 emissions from dry tundra soils
b) Increased tundra and forest fires

3. Carbon methane feedback loops (72 x the power of CO2 over 20 years)
The Arctic holds far more carbon that is vulnerable to global warming than any other region. Over the past few years, new research has found that the amount of Arctic carbon is double past estimates and that far more carbon emissions will be released this century than predicted (mostly as methane) — up to five times more. This carbon is coming from several Arctic sources:

a) Wetlands - warming (methane)
b) Permafrost - thawing (mainly methane, some CO2)
c) Sea floor methane hydrate - destabilization by warming (methane)

4. Nitrous oxide (289 x the power of CO2 over 20 years)
Warming peatlands and thawing permafrost are emitting N20

All of these carbon stores are vulnerable to global warming, meaning they will emit carbon as they are warmed by a positive feedback process, further increasing the rate of global warming.

The feedback process in each of these cases is now operant. The Arctic changes have the climate system primed for a runaway scenario.
 
"The potential for runaway greenhouse warming is real and has never been more clear."
— UNEP Year Book, 2009

A 2009 study by ecologists estimated that Arctic lands and oceans are responsible for up to 25 percent of the global net sink of atmospheric carbon dioxide. Under current predictions of global warming, this Arctic carbon sink could be reversed, making it a net source of carbon and accelerating predicted rates of climate change.

NASA images (right) show that the Siberian land permafrost region and the East Siberian Sea surface temperature are warming more rapidly than anywhere.

Multiple cascading Arctic feedbacks will increasingly drive more global warming, which will drive greater feedback ... driving more global warming ... leading to ever increasing, totally unstoppable so-called "runaway" global warming. This is the greatest global warming danger to the survival of life on Earth.

ARCTIC FEEDBACK

PLANETARY CLIMATE 'RUNAWAY'

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In a 2010 publication (Possible role of wetlands, permafrost, and methane hydrates in the methane cycle under future climate change: A review, Reviews of Geophysics) the authors (O'Connor et al) conclude, based on a comprehensive review of recent literature, that "significant increases in methane emissions are likely, and catastrophic emissions cannot be ruled out'.

"The feedback loop can be described in simple terms as follows: rising CH4 emissions from wetlands, thawing permafrost, and destabilizing marine hydrates increase atmospheric CH4 concentrations; this increase in CH4 concentration, amplified by the effect of CH4 on its own chemical lifetime, results in a greater radiative forcing on climate and terrestrial ecosystems. The ecosystems, given our current understanding, respond to the warmer, more humid conditions by an increase in BVOCs, which further augments the chemical lifetime of CH4 Finally, the resulting additional radiative forcing could lead to more or faster thawing of permafrost, further destabilization of marine hydrates, and potentially even larger wetland CH4 emissions."

(BVOCs are biogenic volatile organic compounds)
In a 2010 publication (Possible role of wetlands, permafrost, and methane hydrates in the methane cycle under future climate change: A review, Reviews of Geophysics) the authors (O'Connor et al) conclude, based on a comprehensive review of recent literature, that "significant increases in methane emissions are likely, and catastrophic emissions cannot be ruled out.

"The feedback loop can be described in simple terms as follows: rising CH4 emissions from wetlands, thawing permafrost, and destabilizing marine hydrates increase atmospheric CH4 concentrations; this increase in CH4 concentration, amplified by the effect of CH4 on its own chemical lifetime, results in a greater radiative forcing on climate and terrestrial ecosystems. The ecosystems, given our current understanding, respond to the warmer, more humid conditions by an increase in BVOCs, which further augments the chemical lifetime of CH4 Finally, the resulting additional radiative forcing could lead to more or faster thawing of permafrost, further destabilization of marine hydrates, and potentially even larger wetland CH4 emissions."

(BVOCs are biogenic volatile organic compounds)

Methane Catastrophe