Here is another unintended effect of our greenhouse gas emissions. (See the January 4, 2013 post for feedback loop 2.)
Both of the global warming feedback loops shown below involve the potential release of hundreds of millions of tons of methane, currently frozen in tundra soils and shallow ocean sediments.
On a molecule-for-molecule basis, methane is 30 to 70 times more effective than carbon dioxide at trapping heat in the atmosphere.
In an exhibit of chemical irony, after about 12 years in the atmosphere, the methane molecules degrade (oxidize) into carbon dioxide and water vapor-- both important greenhouse gases.
Climate feedback loops 2, 3, & 4 are all positive feedbacks (or runaway feedbacks) and tend to amplify (rather than counteract) the effects of human greenhouse emissions.