Enlarge / Craters and mounds on the floor of the Barents Sea. (credit: K.

Andreassen/CAGE)
It’s not that hard to understand the changes that have controlled the levels of carbon dioxide in the atmosphere during past climate changes.

But methane (a potent greenhouse gas itself) does some mysterious things.

A lot of it is secreted away in seafloor mud in the form of an odd substance called “methane hydrate”—methane gas in molecular cages of water ice that only survive at low temperature and high pressure.
The thawing of these methane hydrates would release the gas into the ocean and atmosphere.

For several rapid climate change events in Earth’s history, this has been proposed as a possible source for sudden increase in greenhouse gasses.
Many questions remain unanswered about methane hydrates, including a rather big one: could our current climate change thaw some hydrates, contributing to further warming in the near future? After all, there are places where plumes of methane bubbles can be seen rising from the seafloor today.
Some of those plumes have been active for thousands of years, and (counterintuitively) they might even have the net effect of removing greenhouse gases.

But other areas have inspired concern about the risk of accelerated warming.
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