Re: Methane release and global warming.
Lucio (is that your name?),
Welcome to the Forums!
To answer your question: The greenhouse gas methane is only a trace element in the atmosphere, nowadays it is 1.75 ppmv and pre-industrial it was 0.7 ppmv, so already a raise of hundred percent. It’s Global warming Potential (GWP) is 20 to 30 times higher than CO2.
The largest amount of methane is captured in gas hydrates. These hydrates are molecules of gas trapped by water molecules. They crystallize into ice and form so called clathrates, so the gas molecules are caged by the water. In this structure the cages are arranged in body-centered packing; the unit cell contains 46 molecules of water and up to eight molecules of methane (CH4). Not all cages are occupied. If all cages would be occupied by methane, one cubic meter of solid hydrate could contain 170.7 m^3 of methane gas at sea level. In nature, one cubic meter of gas hydrate contains up to 164 m^3 of methane.
These clathrates are trapped mainly in the permafrost and ocean beds. Here the temperatures are low enough and the pressure is high enough, to keep the clathrates intact. So with a temperature rise the permafrost will melt releasing the Methane. In contrast, with a temperature drop the sea levels will drop and the methane will also be released from the ocean floor. Any mayor global temperature disturbance will probably cause Methane to be released.
Currently there is 3.5Gton C as Methane in the atmosphere, but a rapid release of methane (10 Gton) will kick the concentration to 6ppm. Methane only has a lifetime of 10 years after which it is converted to CO2, so probably with the release of 10 Gtons of methane the climate will change and temperatures will rise (how much, I do not know!). But only for a short time; or the release of methane has to stay constantly high. The CH4 is 20 to 30 times stronger than CO2 but with this short lifetime the effect will be mayor but probably of a short term.
