jfc lys.
Ok so let's try to break this down. I don't have time top sit here and write the full thing at once, so you'll get it in parts.
Let's start with the sensationalized apocalyptic scenario. It can happen, and in fact it caused the single greatest extinction event in earth's history so we should consider it a really big gun held to humanity head, but at the moment we're a long ways off from it being an issue.
So CO2 isn't the strongest greenhouse gas. Of the "common" atmospheric gases, methane is about the worst of them, we just produce so much less of it than CO2 that it's a minor issue (and the release of it into the atmosphere of it has leveled off since the late 90's anyways). However the earth has a massive amount (somewhere in the neighbourhood of a Tera Tonne trapped in metastable reservoirs in deep ocean ice. tl;dr version, methane and water can combine to produce methane hydrate, which can freeze. As methane hydrate cycles through the ocean, some of it gets into the ocean sediments and freezes there, where it remains trapped. If you had the cool chemistry teacher in high school, you might have got to light some methane ice on fire as a demonstration. Same Stuff.
The key issue here is that this stuff is *frozen*. Which of course carries the implication of "can melt". As the oceans warm, this stuff can melt, causing the methane to be released. IF this happens on a large scale it is a run away event, with the release of that much methane providing significant positive feedback to the warming effect. We're pretty sure this has happened at least twice in the earth's history and damn sure of one of those.
This is bad in it's own right since it significantly accelerates the warming of the earth, however if the runaway goes on long enough, it also comes with a couple major side effects for the ocean, namely significant increase in ocean acidity and a significant decrease in available oxygen in the ocean. I don't know if you've kept fish, but you may have noticed they're temperamental little bastards who need a fairly narrow range of environmental conditions. A severe case can and will result in the extinction of upwards of 90% of marine life. And if fish don't like those conditions anaerobic bacteria do, most relevant to us are sulfate-reducing and methanogenic bacteria. The former releases hydrogen sulfide into the atmosphere (which is pretty bad for terrestrial life) and the later release more methane. This itself kicks off another feedback loop, as marine life dies off, their corpses sink into the deep ocean waters, where decomposition pulls more oxygen out of the water, leading to greater anoxia. In the worst case scenario those anaerobic bacteria begin to dominate the chemistry of the oceans and the oceans begin emitting massive amounts of poisonous gas.
At this point, we've probably already started to see a feedback effect between the atmosphere and the biosphere. North America in particular is vulnerable to this, the 1930s and the dust bowl provided a fairly minor example. The american and canadian prairies were, not that long ago a littreal desert. If this hasn't happened already, that release of hydrogen sulfide will be more than enough to start choking life out on the continents. It's possible enough gas is released to bascily fumigate the continents. More likely it just starts to kill off plant life, which reduces biomass available as food to herbivores and insects, and the food chain collapses in on itself.
This is not hypothetical. This has happened, and it resulted in the single greatest mass extinction in the earth's history, and even life that was effectively immune to past extinction events (namely plants and insects) or more weakly effected (sea life) was massively reduced. At the Permian–Triassic transition, what is now Siberia saw the single largest volcanic event we know of thus far. By the time it ended area only slightly smaller than the contiguous united states (or about the size of australia if you prefer) covered with volcanic rock averaging about half a kilometer deep. This would have been rough enough, but unfortunately for life Siberia has of the richest and most easily accessible coal and gas fields in the world, and 250 million years ago they were vastly richer still. Were, because this volcanic activity was more than sufficient to light those coal and gas fields on fire. By time they burned themselves out somewhere between 10000 and 100000 billion tons of CO2 was released into the atmosphere, kicking off a cycle of global warming and climate change leading to the P–T)extinction event, or more colloquially The Great Dying. Upwards of 90% of all species went extinct. 97% of all ocean life died. 70% of terrestrial life, including insects died. It ended the synapsid and the other proto mammals and lead to the dominance of Archosaurs (ie dinosaurs and a few other things) for the next 200 million years. Plant life died off to such an extent that there are no coal beds worth talking about dating to the early triassic period. The extinction event that did in the dinosaurs 200 million years later despite itself being one of the worst in history was minor in comparison.
Fortunately, this at least is not an immediate concern. While exactly what level of CO2 release was needed to set the earth on that course, the general consensus is that humanity is a good couple orders of magnitude of having released that much. This isn't to say that we're not capable of it, our release of CO2 into the atmosphere has thus far followed an exponential growth pattern, and if we don't check that then over the next couple centuries it will become a much more prominent threat. If we do reach that tipping point, we'll no more be able to avoid the consequences than if you put a gun to your head and pulled the trigger. It's a threat to be taken seriously, and we don't solve the issue humanity goes the way of the dinosaurs. But we have time to disarm that particular time bomb and if it does go off we'll have absolutely earned it.
Of more disastrous consequences will be much lower levels of warming leading to the melting of the antarctic ice sheets and that mentioned atmosphere-biosphere feedback effect leading to megadroughts in North America. But this is quite enough typing for now.
Sign In
Create Account
Back to top
