The fear is that the change will be so fast and so drastic that the short lifetime won't save us. It's thought that runaway methane release could result in 6+ degrees (celsius) of warming within just a few decades as massive amounts of methane are released. The influence of methane would end relatively quickly too, but the damage would be incredible.

Nobody is really sure if this would actually happen, though.

Methane does break down much faster than CO2, but over the time scales being discussed here it's MUCH more powerful. From memory so probably somewhat off it's >80x more potent a greenhouse gas over a decade, dropping to only 20x more potent when measured over a century.

The big problem is tipping points. There are a lot of things where an initial big hit can be something you don't recover from, no matter how light the impact might seem when measured over years.

Methane is a very potent greenhouse gas, and the release would be absolutely huge. The momentary spike would well cause a lot of CO2 to be released.

On a positive note, while it may not suffice to save human civilization, CO2 likely won't get baked out of rocks. Or at least, it hasn't after previous "methane gun" events.

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

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

"While CO2 persists in the atmosphere for centuries, or even millennia, methane warms the planet on steroids for a decade or two before decaying to CO2.

In those short decades, methane warms the planet by 86 times as much as CO2, according to the Intergovernmental Panel on Climate Change."

Source: https://www.scientificamerican.com/article/how-bad-of-a-gree...