image from wikipedia

A Methane clathrate, also called methane hydrate or methane ice, is a form of water ice that encloses a large amount of trapped methane gas within its crystal structure.

In contrast to usual water ice the methane ice can burn (see image).

Large deposits of methane ice have been found hidden under sediments of Earth. Moreover below the zone of solid methane ice, large volumes of methane may occur as bubbles of free gas in the sediments.

The discharge of methane (coming from the ice) is under suspect to have furthered the Paleocene-Eocene Thermal Maximum (PETM) a sudden global climate change, which upset oceanic and atmospheric circulation and led to the largest known mass extinction.
image from wikipedia.
This suspect or hypothesis is called the Clathrate gun hypothesis and was e.g. summarized in the BBC2 ‘Horizon’ documentary, ‘The Day the Earth Nearly Died. The basic idea is that a global warming due to e.g. a giant volcano outbreak let to the discharge of big methane gas clouds which were stored in the methan ice (i.e. massive gas clouds were suddenly released due to the warming). These methane clouds in the turn enforced the greenhouse effect und thus produced even more global warming (a runaway greenhouse effect). This happened too fast for organisms to adapt and thus leading to a mass extinction of 95% of the species on the earth (for more read the BBC link).

Well this is a hypothesis and the current computed climate change is not yet in the dangerous temperature region, but we are getting closer rather fast if we go on like that.

Hopefully the current global warming won’t end up in such a terrifying scenario. However it is clear that the discharge of further greenhouse gases and Deforestation* must be dramatically reduced. In particular it should again be emphasized that it is mainly the speed which kills and it kills already now (see e.g. here).

But unfortunately there are not only plans to burn the resources hidden under the melting polar ice but also to exploit the methane in the clathrates, like e.g. these japanese or US project. Burning methane produces again, like other fossil fuels, the greenhouse gas carbon dioxide.

Which means: there may be plenty to burn. One shouldn’t. **

comment added 11.1.2019:
*Regarding deforestation:
With respect to the earth temperature there are meanwhile indications that deforestation might have a more or less significant
cooling effect due to the related change in brightness (forests look darker than grasslands and thus absorb more heat). This is as of now under investigation
Jamie Wilson from unitedbankofcarbon writes here.

By gaining a clearer picture of the changes in some of the lesser known interactions, the overall climatic impact of deforestation can be better understood, enabling both more informed policy decisions around land-use to tackle climate change and better understanding as to how such decisions will impact the climate.

**Regarding the burning of clathrates:
In opposition to what I wrote above I meanwhile do think that it might eventually be necessary to get the methane out of the clathrates, which might include
burning. That is it seems the impact of methane as a climate change driver might have been underestimated and thus gas discharges from clathrates and permafrost
might be so destructive that it would be better to burn them (which produces less potent CO2). But of course in terms of CO2 reduction it would be better not to just burn, how it has mostly been done until now, but to burn the methane in
a controlled way which retains the CO2 like in a socalled CCS power plant, so that the CO2 could be used somewhere else.

comment march 5, 2019: A research group of TU Vienna has shown that it is possible to burn methane while keeping the CO2 onsite, as reported in Natural gas facilities with no CO2 emissions.

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