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Much ado has been made by a few petroleum engineers and global-warming alarmist about all of the methane gas trapped in frozen form, mostly on the ocean floors.

The "What-if" scenario begins to play out in 2080 or so, when a few petroleum engineers claim that the skies will start to turn a brownish color, making the earth even hotter.

These comments are buried deep in old magazine articles and by now these engineers are probably working for another employer. Even Al Gore did not say much at all about natural frozen methane gas being set free in massive quantities. But a few geologist and alarmist say it will happen as expected.

Even if it comes true, questions abound about what year it maybe dense enough to make the Earth like Venus. Will it mean that as it builds up it will move closer to the ground and begin to poison us directly? Birds will drop out of the sky by the millions. Animals will move down from tall mountains. 90% of the human race could die off, but some would die from ignorance, like in hurricane Katrina.

Would this be the toxic gas that could "Shroud the world" within the next 100 years? Someone please prove this is wrong, or at least there are "workarounds" for the problem.

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    $\begingroup$ What an epitaph for humanity... "The planet farted, then we all died.". Guess its better than... "mostly harmless." $\endgroup$ – Henry Taylor Aug 6 '16 at 5:59
  • $\begingroup$ For a real-world analysis and discussion, try Earth Science instead! Maybe this can be migrated since it already has answers? $\endgroup$ – JDługosz Aug 6 '16 at 14:35
  • $\begingroup$ @JDługosz. I do not want to edit the question, so I have pasted a copy into the "Earth Science" site as suggested in the above comments. Since it is on hold here, it is not doing anyone any good in terms of answers. $\endgroup$ – user25006 Aug 6 '16 at 20:22
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Extinction event, yes. "Shroud the world", no. At least not as you think.

Methane sources are largely of two types: permafrost and oceanic. Permafrost methane, estimated at ~400 GTc, is obviously susceptible to a short-term catastrophic feedback cycle. Oceanic reserves are larger (500 to 2500 GTc) but the thermal inertia of the oceans/rock strata is obviously much greater, so any really widespread methane release would be much slower.

Permafrost methane is nearly 50% of the total atmospheric carbon (800 GTc) and since it has a much greater warming effect, ~ 80 to 100 times that of CO2 for decade timespans, releasing it all in a short time would be very, very bad. However, the density of methane is about 0.4 that of CO2, so such a release would have a maximum concentration of 0.1% (2.5 x 400 ppm). Flammable concentrations of methane are in the 5 to 15% range, so global explosions are not an issue, and methane becomes a breathing issue at even higher concentrations (~25%), when it would drop the oxygen content to below about 16%. For breathing considerations, methane can be considered inert, and does not affect respiration the way CO2 does.

Runaway permafrost emission is a tricky business, since ice has a very high specific heat, which makes it difficult to heat the entire several hundred meters of permafrost depth quickly. Counteracting this methane release is the fact that methane does degrade to CO2 over a time span of a decade or so, so a release on a longer time scale will produce a cap on peak methane levels (and the greenhouse warming which it would produce).

The long-term effect of releasing permafrost methane is an increase of CO2 levels by 50%, to 600 ppmv. However, during the interim, greenhouse warming would presumably greatly increase the water vapor levels, and THAT is the bad news. Water vapor is a much more powerful greenhouse gas than methane, although it also can precipitate easily, which tends to regulate the amount in the atmosphere. So the gas which would shroud the world would be water vapor.

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  • $\begingroup$ Worth noting that massive permafrost melting is believed to have happened several times since the current series of ice ages and interglacial periods started. Yes, the resulting extreme climate swings have contributed to many species going extinct. Life as a whole was not threatened. Also note that the commonest state of the Earth during the last 600M years is far hotter than in our era, humid and ice-free. The current climate is unusually cool, and very unstable. $\endgroup$ – nigel222 Aug 6 '16 at 10:47
  • $\begingroup$ @Sparky256 - My pleasure. Wait a day or so, and then be suuuure to select. Unless you've changed your mind, of course. $\endgroup$ – WhatRoughBeast Aug 6 '16 at 16:28
  • $\begingroup$ @Sparky256 - Thanks for the selection, but you should be aware that it's best to wait at least a day, as I suggested. You never know but someone will provide a better answer, or establish that what seems like a good answer has the drawback that it's wrong. I'm not objecting to the selection, mind you, or suggesting that I might (even in principle) be mistaken (certainly not! I thought I was wrong once, but I was mistaken), just pointing out that it's generally best to wait a bit. $\endgroup$ – WhatRoughBeast Aug 6 '16 at 16:38
  • $\begingroup$ You stated the crucial answers with just enough math to be convincing. The result is that water vapor will change the Earth the most, until the next ice-age kicks in. Someone else may answer with charts and more math, but your answer gets to the crux of the issue, and that was all I wanted. $\endgroup$ – user25006 Aug 6 '16 at 16:44
  • $\begingroup$ @Sparky256 - Dude. If you are persuaded by "just enough math to be convincing", I sincerely suggest you stay off the Internet. "Figures don't lie, but liars sure do figure." Particularly stay away from conspiracy sites. Convincing math sometimes is wrong. $\endgroup$ – WhatRoughBeast Aug 6 '16 at 16:48