The closest life ever came to complete annihilation, was around 251 million years ago, when only 5% of the species survived. This mass extinction episode is distinctively linked to an intensive increase in methane (CH4) concentrations in the atmosphere and in the oceans, as a consequence of methane release from methane hydrates.
Although CO2 is a much more well-known greenhouse gas, Methane is at least as significant as CO2.
The reasons why CO2 draws most of the attention is that its emissions are currently much higher than Methane (however the methane concentrations since the industrial revolution increased by 150% compared with 40% increase of CO2) and since CO2 stays longer in the atmosphere and so in the long run has a greater greenhouse effect.
Another reason, as always with humans, is political.
The main source of the atmospheric methane is rice fields and cows and sheep burps (the farts are no more than a tittering anecdote). Obviously humans will not do the moral thing and give up meat altogether not even when they risk their own species and not even when they are being told that they might even hurt their offspring or their offspring’s offspring. As you know the meat industry is also a great contributor of CO2 emissions (mainly through deforestation and land clearing for pasture and fodder growing and transporting live and murdered animals all over the world) but since there are more who are liable for CO2 emissions, it is easier to conceal meat as a major factor.
In a sense CO2 is more easily handled since big industries could be blamed and cap and trade campaigns can be initiated so personal level actions can be summed up with light bulb changing.
The climate change debate is mostly political and slightly scientific. As hard as it is to believe from a rational perspective, but totally self-evident from a human perspective, CO2 emissions are highly partisan. Currently Methane isn’t and if there is no political fortune to gain or monetary fortune (cap and trade) why bother arguing?
So while humanity still argues whether CO2 emissions are the cause of climate change, it appears that another greenhouse gas, with more than twice the amount of global reserves of all conventional gas, oil and coal deposits combined, is ticking underneath its feet.
You would usually read that Methane has a warming potential 25 times greater than CO2, but that’s true for 100 years scale. In a 20 years scale, it is 72 times greater. And not only that Methane is much more potent than CO2, as it gradually breaks down in the atmosphere (slowly oxidizing), each Methane molecule converts to a CO2 molecule and 2 water molecules, meaning that even after being oxidized, it still affects the climate, acting as an important source of water vapors (which are a potent greenhouse gas) to the stratosphere (the second major layer of the Earth’s atmosphere, just above the troposphere) and of CO2.
So if CO2 is the chronic problem then Methane is the acute one. And our interest is in acute solutions.
The only advantage of CO2 over Methane as greenhouse gas is that it stays much longer in the atmosphere, so what is needed for it to be a possible solution is finding a huge source of it so that an acute discharge would be both uncontrollable and globally fatal. Fortunately there is such a source in the form of hydrates.
What is Methane Hydrate?
Methane hydrates, also known as methane clathrate or methane ice, are crystalline solids consisting of methane gas molecules, each molecule is surrounded by a type of 'cage' of water molecules. There is no chemical bond between the gas molecule and the enclosing water molecules so the methane gas is actually caged within an ice lattice.
The density of methane hydrate is much higher than that of standard methane gas because the water molecules (connected to each other by hydrogen bonding) pack methane molecules close together. In the most common structure one unit volume of methane hydrate includes about 168 unit volume of methane gas at standard conditions. So a release of a small volume of methane hydrates would release high amounts of methane.
Where and how do Methane Hydrates form?
The Methane hydrates forming process is actually a common by-product of biological activity beneath the seafloor. A group of microorganisms known as the Methanogenic Archaea, discharge methane as they feed off of dead plankton and other organic matter that have sank and accumulated over millions of years hundreds of meters below the sea floor, the methane they discharge combines with the water into hydrates. That’s why most deposits are found along continental margins where high burial rates of organic matter drive considerable production of methane.
For methane hydrate to form, conditions of high pressure and low temperatures are needed. In terrestrial systems these conditions can be found in permafrost (permanently frozen ground) typically from depth of around 200m. And in marine systems, below 300-600m of water depth (200 meters in the Arctic since it’s colder and even much less for subsea permafrost sediments) and usually no deeper than 2000m. Since methane hydrates float (like ice) they don’t accumulate in water. But when they form in the seafloor sediment they stay where they are formed, and can extend there for hundreds of meters below the sea floor.
In the seabed sediment, methane gas (which is less dense than water thus lighter) tends to quickly float towards the seafloor surface. As the molecules slowly migrate upwards through the sediments, at some point they reach an area with conditions of temperature and pressure under which hydrates are stable called - the gas hydrate stability zone (GHSZ). There they combine with water found in the sediment to form the methane hydrates.
Those methane hydrates are kept locked in place and tend to cement sediments together, creating an impermeable layer.
Beneath, more methane gas keeps on getting produced by the Methanogenic Archaea and seeps upwards towards the surface, until it hits these cemented sediments, which it cannot penetrate. So instead the gas continues to pile up, forming a layer of bubbles beneath the hundreds of meters of sediments that are cemented together by still-frozen methane hydrates .
How much Methane Hydrate is there?
There is an enormous amount of methane hydrate all over the planet. There are different estimations from 2,500 to 63,000 Gigaton but the "consensus" value, the most widely quoted, is 10,000 Gigaton, found within the seabed of the ocean. In addition, it is estimated that more or less the same amount of methane is found in a gas form in the sediment around the hydrate layer.
Also a substantial amount, of 400 Gigaton, is found in terrestrial permafrost soils.
For comparison, the total carbon amount in the atmosphere (as carbon dioxide) is about 800 Gigaton, which is usually presented as 395 ppm (2 Gigaton carbon are about 1 ppm in the atmosphere), and the estimated amount of carbon emissions from fossil fuel combustion since the industrial revolution is about 400 Gigaton (emitted over a period of about 200 years). That’s about 50 times less than the amount stored as methane hydrate as aforesaid a much more potent greenhouse gas.
Why Methane Hydrates?
If the overlying sediments are disrupted, the pressurized methane can escape at a burst. Released "clouds" of bubbles of methane gas (168 times its previous volume) are able to rise hundreds of meters up .
More efficient but less common under natural conditions, are rising chunks of methane ice called Dissociated Hydrate (chunks that are no longer bound to the seabed) which float in water just like regular ice does, carrying methane to the atmosphere much more efficiently than the bubbles. As they reach the water surface they rapidly melt, releasing the methane directly into the atmosphere.
Increase in temperature largely affects the methane hydrates stability. Climatologists refer to the matter as "a ticking time bomb". They warn that incremental oceanic warming above a few degrees Celsius could initiate a chain reaction that would raise the water temperatures in the intermediate depths and affect the hydrates. Then a positive feedback mechanism takes over as the methane hydrate decomposes, releasing the methane into the atmosphere leading to increased warming leading to more methane release from other areas of methane deposits elsewhere in the world. This warming will set in motion other positive feedbacks as well (Carbon Sinks and Albedo).
Actually there's already leakage of methane from hydrates into the atmosphere, from thawing permafrost soils, found in the arctic region.
As mentioned before, there are deposits of 400 Gigaton in terrestrial permafrost soils but there is even a higher amount in subsea permafrost sediments. There are estimates of 2,500 Gigaton in methane hydrates in subsea permafrost sediment in the arctic area. These permafrost sediments are much less stable than the terrestrial ones (which have also began thawing) since they are covered with water with a temperature close to 0˚C since the end of the last glacial period and so are in a thawing process ever since, releasing methane to the overlaying water.
Estimates based on measurements in the East Siberian shelf (30% of the arctic shelf seas) show a release of 8 million tons carbon a year from that continental shelf only. Since most of this continental shelf is extremely shallow (75% of the area shallower than 40m deep) most of the released methane does not oxidize and so reaches the atmosphere as methane and not CO2, a stronger greenhouse gas.
We mentioned the extinction event about 251 million years ago, called the Permian-Triassic extinction event, in which according to common scientific belief global warming caused by greenhouse gases ejected by a massive volcanic activity led to the disruption of the submerged methane hydrates reservoirs - causing massive volumes of methane to rise to the surface of the ocean in huge bubbles. Vast amount of methane was released into the atmosphere which caused more warming, and thus melting further hydrate reservoirs .
How to set them free so they can set everyone free?
Melting of that kind occurred several times and had acute effects at each event, yet as severe as past events were, the methane hydrates' full potential was not yet revealed. Mainly because so far the methane release was a slow process. By natural conditions it takes decades to centuries to warm up the water hundreds of meters down in the ocean and centuries to diffuse that heat down into the sediment where the base of the hydrates' stability zone is (the Arctic Ocean may be a special case, because of the shallower freezing zone and because warming is more intense there). Also, if the heating process is stretched and gradual - large amount of the methane molecules get dissolved in the ocean's water and reach the atmosphere moderately, only decades to centuries later, some never escape the ocean at all. However, an abrupt, wide-spread release of methane into the atmosphere has never occurred and this is where our hope lies.
Temperature rise is not the only force able to set off methane discharge, it can also take place at a more local level by earthquakes and landslides, as far as it goes for natural causes. We have to find a way to cause critical mass methane release that would dramatically change the living conditions on this planet.
A bizarre but interesting lead comes from the energy industry. Since the energy locked up in methane hydrate deposits is more than twice the global reserves of all conventional gas, oil and coal deposits combined, the oil industry has been showing great interest in this substance. Ignoring repeated warnings by geologists regarding the unstable nature of the hydrates and the far reaching global affect they may drive, and despite there have already been incidents of oil drilling inadvertently triggering large releases of methane from hydrate deposits, the oil corporations keep exploring ways of utilizing the hydrate's energy for human consumption.
Not until long ago the earth's climate was considered as something that will change gradually, as CO2 and global temperatures continue to rise. But nowadays there is a growing consensus among climate scientists that positive feedback mechanisms are likely to abruptly amp
Thanks to humans' greed this research field and the hydrates themselves are relatively highly accessible.
The whole climate change issue is very typical of humanity, focusing on ‘the self’ now and not giving a dam about the rest later. We mustn’t give a dam about ‘the them’ now and focus on the rest in the future.
Most of the ones who are willing to deal with climate change ignore the ticking bomb underneath their feet. We shouldn’t. We should examine and use whatever means available, possible and necessary to end all of the suffering.
The melting of methane hydrates have led to severe environmental impacts at numerous events in the past and contributed to several extinction events. Using Earth’s detained mighty forces in the benefit of its inhabitants could be the only one solution.