Myths

Myth 1.: Little or no methane is venting in the Arctic, so there's nothing to worry about. 

Reality 1.: Methane is venting in the Arctic, but it can be hard to detect how much and where this takes place. Some satellites circle around Earth above the equator, making that they watch the Arctic through a thicker layer of atmosphere, which can mask detection of methane in the Arctic. Furthermore, since methane can quickly rise in the atmosphere and move with the wind, releases could be missed by flask and in situ measurements at surface levels unless measurements happen to be taken in close proximity to the point of release. Too little measuring is taking place and more should be done to monitor this.

The big worry is what will happen as temperatures rise even further. Warming due to higher concentrations of greenhouse gases in the atmosphere is occurring much more vigorously in the Arctic than elsewhere on Earth. Waiting for further proof that methane is increasingly venting in the Arctic carries the risk that it will be too late to do much to reverse the process by the time such research is completed.

Moreover, there is a wealth of evidence from scientists such as Semiletov and Shakhova who have repeatedly done research in the East Siberian Arctic Shelf, complete with first-hand reports that methane plumes have been detected, some over one kilometer wide.

"We've found continuous, powerful and impressive seeping structures more than 1,000 metres in diameter. In a very small area, less than 10,000 square miles, we have counted more than 100 fountains, or torch-like structures, bubbling through the water column and injected directly into the atmosphere from the seabed," Dr Semiletov said, "We carried out checks at about 115 stationary points and discovered methane fields of a fantastic scale - I think on a scale not seen before. Some of the plumes were a kilometre or more wide and the emissions went directly into the atmosphere - the concentration was a hundred times higher than normal."  -  Vast methane 'plumes' seen in Arctic ocean as sea ice retreats, Independent, Dec 13, 2011.

Myth 2.: Hydrates cannot exist in water as shallow as in the East Siberian Arctic Shelf; therefore, no methane could be venting there.

Reality 2.: Waters in the Arctic are (still) cold, compared to elsewhere, making that hydrates can exist in shallow waters. Methane hydrates in the East Siberian Arctic Shelf can occur at depths as shallow as 20 m. Moreover, hydrates are present in the sediment underneath the seabed.
http://www.skepticalscience.com/arctic-methane-outgassing-e-siberian-shelf-part2.html

Myth 3.: Global warming heats up the water in the Arctic from above, where there are no hydrates. It will take hundreds of years for this heat to reach the bottom of the sea.

Reality 3.: While the sun does heat up the waters in the East Siberian Arctic Shelf (ESAS) from above, the waters are quite shallow. Additionally, warmer water enters the Arctic from the Atlantic and Pacific Oceans, and from rivers in Siberia. As the sea ice disappears, more open water allows more storms to develop that mix the waters, while tidal pressure differences will also be more pronounced.

At a presentation on November 30, 2010, Natalia Shakhova warned that the ESAS is now 5°C warmer, while additional factors enhance permafrost destabalization in the ESAS:

1. Decreasing sea ice extent;
2. Change in hydrological pattern:
- increasing frequency of high speed winds;
- increasing frequency of deep convection events (mixing to the bottom) during summer;
3. Warming of bottom water (up to 3°C during the last three decades)

Another study observed that more summertime open water in the Laptev Sea in 2007 caused more vertical mixing of the water column during storms in late 2007 -- bottom water temperatures on the mid-shelf increased by more than 3 degrees Celsius compared to the long-term mean.
http://www.polarresearch.net/index.php/polar/article/view/6425/html_150

Myth 4.: Even if heat did reach the seabed, it would take hundreds of years for the heat to penetrate the sediment.

Reality 4.: It can indeed take a long time for heat to propagate down the sediment. But it can also occur very rapidly, when heat is transferred down fluids in cracks and openings in the rock and sediment, called pingos, which were formed by local accumulation of hydrate (ice) below the sediment surface in the past, and by methane migrating upwards through conduits. Pingos and similar structures can link to deep-rooted plumbing systems that allow thermogenic fluid migration from several-kilometers-deep sedimentary basins.

Paull et al. describe pingo-like-features on the Beaufort Sea Shelf, adding that a thermal pulse of more than 10 degrees Celsius is still propagating down into the submerged sediment and may be decomposing gas hydrate as well as permafrost.
http://arctic-news.blogspot.com.au/p/potential-for-methane-release.html

Myth 5.: Even if methane did escape from the seabed, most of it would be oxidized in the water - like in the Deepwater Horizon event - before reaching the atmosphere.

Reality 5.: Methane won't get broken down easily in the Arctic, as this requires oxygen, which isn't quickly replenished in the Arctic, once depleted. Depletion of oxygen in the waters of the Arctic could make it hard for oxidation to take place of methane that rises in the waters there.

http://methane-hydrates.blogspot.com/2012/03/large-areas-of-open-ocean-starved-of.html

Furthermore, low temperatures mean there are less bacteria in the Arctic that need more time to break down the methane. In other places, currents may bring bacteria back to the location of the methane plume repeatedly. In the Arctic, currents are long, so once bacteria flow away from the location of the plume, it may take a long time for them to return, too long to survive in Arctic waters which are cold and often receive  little or no sunshine.

In the Arctic, the danger is much larger that methane releases will overwhelm the capacity of bacteria to break it down in the water. In case of large abrupt releases, the danger is that much of the methane will reach the atmosphere unaffected.

Myth 6.: Methane has a short lifetime in the atmosphere. It will be broken down in a few years, so we don't have to worry about it. 

Reality 6.: According to the IPCC, the perturbation lifetime for methane is 12 years. 

http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-10-2.html#table-2-14

The IPCC figure of 12 years does take into account the fact that methane extends its own lifetime by depleting hydroxyl. However, this is an average figure. Large abrupt releases will overwhelm the system, especially in the Arctic where there is already very little hydroxyl present.
http://www.mpg.de/5050963/atmosphere_self-cleaning

Large emissions extend the lifetime of all the methane that is present in the atmosphere. Methane can remain active in the Arctic for decades at a very high warming potential, while the resulting summer warming (when the sun doesn't set) is likely to keep triggering further methane releases in the Arctic.
http://methane-hydrates.blogspot.com/p/faq.html

Myth 7.: Methane is only 20 or 21 times as potent as carbon dioxide. 

Reality 7.: Methane's Global Warming Potential (GWP) for a 100-year horizon has been steadily upgraded by the IPCC, from 21 [FAR and SAR], to 23 [TAR], and to 25 [AR4, in 2007].

http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-10-2.html#table-2-14

For a 20-year time horizon, the IPCC in 2007 gave methane a GWP of 72. The upgrade reflected stronger indirect effects, such as that methane increases its own lifetime through OH depletion, increases tropospheric ozone (a potent greenhouse gas) and enhances stratospheric water vapor (5% in TAR to 15% in AR4). The figure does not reflect oxidation of methane to carbon dioxide, which contributes to the CO2 burden.
http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter2.pdf

Since that time, Shindell and others have improved methane's GWP by including direct and indirect effects, increasing the GWP of methane to 105 over 20 years.
http://www.sciencemag.org/content/326/5953/716.full (Shindell, 2009)
http://unfccc.int/files/meetings/ad_hoc_working_groups/kp/application/pdf/sb28_ipcc_ramaswamy.pdf
Over shorter periods, methane's GWP is even higher. Unlike CO2, methane's GWP does rise as more of it is released. Responses by ecosystems could increase methane's warming potential even further, especially in the Arctic where methane releases could accelerate the decline of snow and ice cover and trigger further methane releases, as described at The potential impact of large abrupt release of methane in the Arctic.