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Adult Homework: Atmospheric methane effects on planet


maxae
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Hello. I'm a writer working on the second draft of my novel, and need to bounce some of the science off people who are more science-minded than I. The basic plot device that I need to develop/debunk in my story is that atmospheric methane is at flammable levels (i.e. just over 5%). To keep this open-ended, what effects do you predict this would have near the planet's surface, and consequently, what consequences would there be for life on the planet? Of course there would be increased temperatures and the like, but I need a more well-rounded view of what would happen so I can measure the plausibility of this plot device.

 

Thanks in advance.

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Sounds like a story....

 

Maybe I can help more if you get beyond the dynamics of maintaining that mixture on a global scale.

 

If you have enough methane to burn, then it will burn until the levels fall below that required to support combustion. Alternatively if you keep replacing the methane, then you eventually run out of enough oxygen to support combustion--at about 12% oxygen (today = 21%)--but that's a lot of methane to keep replacing. And speaking of keeping that level up at 5%, what about photo-oxidation of methane into CO2?

 

...and what of oxidation/reduction (redox) reactions?

Early Earth's atmosphere was a "reducing" atmosphere and could maintain lots of methane; but now that we have an "oxidizing" atmosphere, a chemically reduced compound such as methane won't survive for very long.

 

What time frame are you looking at for this scenario to develop, and for it to play out? Does life survive? Do you know of the Lake Nyos example? Lake Nyos and similar cases are not about methane (that rises in air and disperses), but they are about CO2 that sinks in the air to form invisible streams, ponds, rivers, and lakes described as "death pockets" in low-lying areas; but it's an example of an altered atmosphere.

~

 

 

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You could try looking up an event called the Palaeocene-Eocene Thermal Maximum which is a global warming event that happened some time ago on Earth. One theory is that large amounts of methane were released.

 

As Essay said however, methane doesn't last very long in the atmosphere (about 12 years) so you need a VERY large source if you want to sustain large amounts for any period of time (it does convert to CO2 however, which would sustain elevated global temperatures).

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Thanks for an awesome response. (I'll apologize now, as I'm on the go and responding from my phone--I'll try to make this as readable as possible, but there are bound to be mistakes.)

 

Definitely doesn't need to be on a global scale, it only needs to fill a few important roles. Essentially, the idea is to make exiting the Earth's atmosphere difficult, and entering again soon afterward almost impossible. The premise is that an asteroid is on a collision course with Earth, but the climatic conditions make it more worthwhile to evacuate than to develop a deflection mission.

 

Of course, the methane won't keep them out for long. It only takes about 8 years, from what I've read, for the methane too do its thing and go away, and of course it will be at less than flammable levels long before that. They only need to be stopped for the immediate future, since they are indeed given a reason to return.

 

The timeframe can be manipulated, so the only concern is plausibility.

 

I do need life to survive these conditions for the story to work. But, the people already spend most of their time indoors to avoid the harsh conditions, and I have toyed with the idea of augmenting their bodies with technology just to make the environment survivable (assist breathing, filtering out toxins, etc.)

 

The proposed source for this large influx of methane is lab grown meat. Increased global population with increased meat consumption, all in the face of disappearing farmland (to support more residential space), causes these labs to pop up everywhere.

 

So, can we have have pockets of methane, perhaps, that would make entering and exiting the atmosphere with any immediacy nearly impossible (or is there something else which could take the place of methane here)?

 

And then, could the presumed source plausibly create that much methane, and for how long (given current levels of oxygen, etc.)?

 

Lake Nyos is super intriguing. Don't think it's going to help me out here, but I'm definitely going to read up on the phenomenon.

 

Thanks for all the help you've been so far. You've given me a lot to think about.

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