[stcredzero]

What has been released after the previous "methane gun" events?

[mirimir]

The Paleocene–Eocene Thermal Maximum[0] and the Permian–Triassic extinction[1] may have involved "methane gun" events.

0) http://www.pnas.org/content/113/28/7739.full.pdf

1) http://www.bbc.co.uk/science/horizon/2002/dayearthdied.shtml