Can runaway methane gas emissions be an extinction level event?

Question

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.

Answer 1

IF, and it's a very big IF, all the methane hydrate were to be released rapidly, then the planetary climate would be stuffed. But it won't happen.

How much methane hydrate will be released due to global warming? Run 30 different atmospheric-ocean-coupled global climatic models, and you will get 30 different answers - all of them based upon arguable assumptions. The scaremongering doomsayers love to fanfare the worst case. In which case, some of your dire forebodings may come about. But first, take a balanced view of the physical reality. The vast majority of all the world's methane hydrate is sufficiently deep, on or in the sea floor, that it will be millennia, if ever, before they melt, thereby contributing to global warming. The deep ocean floor is everywhere only a few degrees above freezing, whereas almost all of the oceanic warming is in the uppermost few hundred metres. Check out the diagram in http://worldoceanreview.com/en/wor-1/ocean-chemistry/climate-change-and-methane-hydrates/ and you will see that the pressure-temperature control is such that most of the methane hydrate will always be stable.

The current consensus is that some methane is already being emitted from the thawing tundra, mainly in Siberia, Canada and Alaska, and some more will be released from shallow seas as and when they warm up. But this won't dominate the global warming process. In fact methane release is just one of at least two dozen feedback processes, some negative but mostly positive, which will influence the rate of global warming for the next few centuries.

Making the world 'toxic', or 'like Venus' or the 'atmosphere turning brown', or 'poisoned birds dropping out of the sky' are all absurd, but that's no reason for complacency. The rise in global atmospheric methane amounts to about 6 parts per billion per year since 2006, or slightly more than 6 ppb in polar regions; significant, but not at all catastrophic. I am far more worried about the accumulating global CO2, which still shows no sign of slowing down despite a dirge of conference resolutions, ineffective carbon taxes, and empty political rhetoric.

As for an 'extinction event', the extreme rapidity of global warming, habitat loss, sea level rise, and ocean acidification, all adds up to the fact that we are already in an extinction event - not for humans, most of whom will be able to engineer their way through a 3 to 4 degree C global temperature rise, but for the rest of the biosphere - with, or without, extra methane.

Notwithstanding the scientific facts, maybe we can all relax, because Donald Trump assures us that climate change is just a fictitious Chinese conspiracy.

Answer 2

2 good answers to this already (one here, one in world building).

To put some very rough estimates to it, CH₄ or Methane has increased significantly over the last 250 years from about 0.72 parts per billion (ppb) to about 1.83 ppb. Source. This accounts for about 20% of the current man made warming, which might be estimated at 2 degrees C by 2100 (very rough estimate). If CH₄ is .4 degrees C of that warming by 2100, that's not nothing, but it's still a significantly smaller problem than CO₂.

What's more, CH₄'s half life in the atmosphere is shorter than CO₂'s, 12.4 years vs over 100 (same source).

If all the Tundra on Earth was to thaw at once (very unlikely), we'd see a big spike in CH₄ and perhaps an uptick in yearly warming, but within 12 years, half of that extra CH₄ might be out of the atmosphere. If the Tundra warms and thaws more gradually, which is more likely, we'd see an increase in CH₄, but over time, the increase would level off. It's not like CO₂ which continues to build because the earth's systems can't take out out of the atmosphere nearly as fast as we put it in.

So in and of itself, CH₄ from melting Tundra isn't a big concern and turning the sky brown or poisoning birds, as others have said, that's very unlikely. Perhaps it will turn our sunrises and sun sets slightly redder. (perhaps), I'm not even sure on that point.

The CO₂, as Gordan points out, is the bigger problem and precisely how world breaking a problem that is, or how soon it is till things get obviously problematic because of CO₂ remains to be seen. It's enormously difficult to predict with any accuracy, but it's possible that CO₂ is a real problem that deserves our concern and effort and I say that without trying to sound like a fear monger. It's simply the truth.

Thawing Tundra will give a little push to already existing climate change, that's commonly called a feedback mechanism and such mechanisms are already included in the climate models by the IPCC and others. The thawing tundra is part of the by 2100 IPPC estimates. It's not something to worry about on top of what's already being estimated.

Now, on "extinction level events" or extinction events. In a very real sense, the increase in human population and our taking over more and more of the earth is already an extinction event and has been for the last 2 centuries or so. Extinction events are relatively common, at least, geologically speaking, even the formation and recession of an ice age can cause a significant rise in extinction and what could be called a minor extinction event.

Now if you're talking Major Extinction Event, the last once of those was 66 million years ago when that Mt. Everest sized asteroid crashed into the earth and was the primary cause in killing off the dinosaurs.

So, part of the answer to your question is a problem of definition. I think the thawing Tundra, by itself isn't much to worry about, (unless you have a house built on frozen land that turns to slush under your foundation) - and yes, that happens fairly often) . . . but on a planetary scale, The thawing tundra in addition to the CO₂ and warming planet is maybe 10% or 20% max added to an already existing problem, so the larger worry is the combination, not the Tundra in and of itself.

There are some methods already in use to help keep Tundra frozen, like thermosiphons

Source.

Brown skies and toxic air are statistically quite unlikely and certainly wouldn't be driven just by thawing tundra. It would take a lot more than just that. The ocean current stopping might cause such a problem, but trying to work a prediction around that beyond saying it's unlikely, is very difficult, even with everything we've learned so far.