During much of the upper Cenozoic, the accumulation of organic matter in Polar Regions, as well as in bogs in tropical and subtropical zones, has created large reservoirs of methane, the most potent common greenhouse gas, vulnerable to release upon a rise in temperature. Global warming, driving a mean rise of 3 to 8 °C in the Arctic early during 2015- 2018, is leading toward the release of billions of tons of methane into the atmosphere, from permafrost, lakes, shallow seas and sediments.
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