http://www.sciencenews.org/view/generic ... or_methane
Certainly coming much sooner that expected............from the article:
"While it’s no ice-nine, a frozen form of methane trapped in ocean sediments could be cause for concern. Warm Gulf Stream waters off the east coast of North America are converting large amounts of the substance into methane gas, which could lead to underwater landslides and influence global climate.
A good portion of the biological carbon on Earth is stored in the seafloor as methane hydrate, a frozen mixture of methane and water formed at high pressure and low temperature. Changes in the temperature or direction of the Gulf Stream, which carries warm water north from the Gulf of Mexico, have heated sediments in a strip along the North Atlantic seafloor by 8 degrees Celsius, unlocking 2.5 billion metric tons of methane from deep-sea caches, scientists report in the Oct. 25 Nature."
It must also be noted that these methane hydrate deposits at lower levels and colder are still subject to rapid releases from landslides above. It takes only a few pounds of mechanical pressure to cause it to fizz out. All it takes in temperature is an increase of 1*C to fizz out.
Also, doing the math on the warming effect of these releases, at 25 times the warming effects of CO2 that is like 25 times 2.5 gigatons or 62.5 GT equivalent of CO2. Last year humans released 26.4 GT of CO2. In 15 years the methane breaks down into water vapor and CO2.