[ancientworldnow]

The latest IPCC report does not account for Arctic methane release. There were too many variables and they decided to omit it and avoid being alarmist. This is discussed on page 28 of WG1 AR5 SPM (the final 2013 IPCC policy maker report).

[mark-r]

But this report is about CO2, not Methane. Methane is yet another reason to be worried.

[fencepost]

I believe the article is primarily talking about carbon release as a result of microbial action, I don't think it focuses on a particular form.