That. Every time the Earth goes through it's cycles trapped Methane gets released.
And those cycles would be?
Here is one theory. The cycles are well known. Their causes are not...
"The Primary Forcing Mechanism (PFM) for climate change is the combination of the elliptical paths of the moon and earth, changes in solar radiation and changes in the gravitational pulses and electromagnetic pulses. The PFM cycles control the Earth's "Natural Climate Pulse", and it is this Natural Pulse that controls weather and climate cycles here on earth.
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The earth's climate is very complex and very cyclical due to the PFM Natural Climate Pulse interacting with the oceans, atmosphere and inner/outer cores of earth. The high and low tides of the oceans alternate approximately every 6 hours, and ocean tides and some currents change with the PFM cycles. Above the surface of the Earth is the atmosphere which is made up of nitrogen, oxygen, water vapor and other gases which move fluidly around the planet. The flow of these atmospheric gases are caused by the rotation of the earth, heating of the atmosphere and ground by the sun, proximity of mountain ranges and water bodies such as oceans, and forcing mechanisms such as gravitational tides caused by the PFM cycles
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Earth's temperature changes seasonally due to the seasonal tilt of the earth, with longer term cycles due to the PFM Natural Pulse cycles every
10-years, 230 years and 130 thousand years. Carbon dioxide concentrations are a naturally occurring cycle connected to the short-term global warming cycles that occur approximately every 230 years, and the longer term 130 thousand year glacial and inter-glacial cycles. The eBook written by Mr. Dilley of GWO (avalable on the Natural Pulse Page) illustrates that earth's current temperatueres and carbon dioxide levels are perfectly normal for global warming cycle that was occurring up to the year 2012 (now beginning to slip into global cooling for the next 150 years)."
2014 Accurate Hurricane -Typhoon Predictions 4 Years into the Future