Page 7 of 24

Re: The Methane Thread pt. 2

Unread postPosted: Wed 23 Aug 2017, 19:25:23
by dohboi
On the other hand: https://phys.org/news/2017-08-methane-t ... didnt.html

Methane from tundra, ocean floor didn't spike during previous natural warming period

It seems...odd... that they seem to take this as some kind of comfort, even though it's warmer today than then, and is about go get much much warmer.

Re: When will the mass dieoff begin? Pt. 3

Unread postPosted: Fri 08 Sep 2017, 04:29:15
by M_B_S

Re: The Methane Thread pt. 2

Unread postPosted: Tue 03 Oct 2017, 07:37:18
by Tanada
M_B_S wrote:=> CH4 Thread?
https://cbmjournal.springeropen.com/art ... 017-0084-y

Revised methane emissions factors and spatially distributed annual carbon fluxes for global livestock
Julie WolfEmail authorView ORCID ID profile, Ghassem R. Asrar and Tristram O. West
Carbon Balance and Management201712:16
https://doi.org/10.1186/s13021-017-0084-y© The Author(s) 2017
Received: 30 May 2017Accepted: 16 August 2017Published: 29 September 2017

Re: The Methane Thread pt. 2

Unread postPosted: Tue 03 Oct 2017, 20:07:42
by dissident
The fixation on the ppmv value of CO2 is rendered nonsensical by the CH4 concentrations. Carbon dioxide could have been around 400 ppmv back 4 million years ago but CH4 was not near 1.9 ppmv. Natural CH4 values are under 0.7 ppmv. CH4 is 74 times more potent than CO2 as an IR absorber. The figure of 25 I often see which is supposedly some 100 year mean ratio is irrelevant. As long as 1.9 ppmv of CH4 is maintained by emissions, the actual 74 ratio value holds. Thus the CO2 equivalent burden today is 403 + 1.9 x 74 = 509 ppmv.

Re: The Methane Thread pt. 2

Unread postPosted: Wed 04 Oct 2017, 02:58:51
by Cid_Yama
ty

Re: The Methane Thread pt. 2

Unread postPosted: Wed 04 Oct 2017, 19:19:01
by dissident
I should have mentioned that the CH4 impact varies spatially. CH4 has a north-south gradient and a height gradient so its relative contribution to CO2 in the troposphere (where IR is trapped) is less than 1.9 ppmv x 74. But additional emissions of CH4 which are in the pipeline are going to fill up the troposphere with high concentrations of CH4 (e.g. 5 ppmv and higher). So we are looking at major spikes in warming coming our way. These spikes will further push the system into a high CO2 regime (warm oceans and induced CO2 emissions).

Re: The Methane Thread pt. 2

Unread postPosted: Fri 06 Oct 2017, 16:48:05
by onlooker
To Dissident or anyone else who feels they can answer. Can any natural element or factor arrest or stop the continuous additional release of CH4? Or will this methane release process now only stop with the exhaustion of the vulnerable methane stores.?

Re: The Methane Thread pt. 2

Unread postPosted: Fri 06 Oct 2017, 16:58:16
by Sys1
To Dissident or anyone else who feels they can answer. Can any natural element or factor arrest or stop the continuous additional release of CH4? Or will this methane release process now only stop with the exhaustion of the vulnerable methane stores.?


I remember having read something like CH4 life in the atmosphere is "short" (10-20 years at most) while CO2 one is much longer (hundred years). When CH4 "decays", it degrades to CO2 (and water, I guess).

Re: The Methane Thread pt. 2

Unread postPosted: Fri 06 Oct 2017, 17:04:00
by onlooker
Yes, Sys, but in the meantime with its potent GHG qualities it will raise temps which then will release more methane and raise temps more. So, this is a most dangerous feedback.

Re: The Methane Thread pt. 2

Unread postPosted: Fri 06 Oct 2017, 17:19:58
by dohboi
onlooker, which CH4 sources do you want to know about. In theory, if slr accelerates rapidly, that could more pressure on much of the seafloor methane/clathrate and so keep it in place for a while even if seafloor temps increase somewhat, as I understand it.

(Not to say this is likely, by the way, and the required amount and rate of slr would be absolutely catastrophic to low and not-so-low lying coastal cities and other sea side properties and biomes. )

But there are many other sources and potential sources and I expect each would have it's own potential negative/damping feedbacks.

Re: The Methane Thread pt. 2

Unread postPosted: Fri 06 Oct 2017, 20:56:09
by Cid_Yama
22420_original.jpg


The pressure at depth on the Siberian Shelf is around 1 Megapascal. The temperature of the clathrates per Semilitov in 2008 was at 272 Kelvins.

As can be seen by the chart, we would need to raise sea level 200 meters to restore stability pressure wise. Obviously, we can rule that out. Since the only other option would be to lower temperatures more than 20 K(also not possible), it's all over.

When the shelf was above water prior to the Holocene, it was kept stable by cold air temperatures. When it became submerged, it began to warm and destabilize. The weight of the ice cap lent sufficient pressure to slow the process, but it appears we were doomed to a release from the start of the Holocene with the rising seas. The loss of the Arctic ice cap has relieved pressure and sped the destabilization along with the warming of the arctic currents.

We are trapped within a process that cannot be stopped or reversed.

Re: The Methane Thread pt. 2

Unread postPosted: Fri 06 Oct 2017, 21:42:15
by asg70
Cid_Yama wrote:We are trapped within a process that cannot be stopped or reversed.


That will come as a relief to Plant, as he can now fly around the world guilt-free (not that he's felt much guilt about it anyway).

Re: The Methane Thread pt. 2

Unread postPosted: Sat 07 Oct 2017, 11:27:23
by dissident
onlooker wrote:To Dissident or anyone else who feels they can answer. Can any natural element or factor arrest or stop the continuous additional release of CH4? Or will this methane release process now only stop with the exhaustion of the vulnerable methane stores.?


Others have raided relevant points already, but the bottom line is the destabilization of CH4 (or carbon) reservoirs and CH4 emissions. Not the CH4 atmospheric lifetime. CH4 is oxidized in the troposphere by OH and destroyed by UV in the upper stratosphere and mesosphere. These breakdown processes will not accelerate to offset CH4 emissions increases. The other detail of importance is that the emissions will not come as a one time spike but will be progressively increasing and ongoing. Geologically this will look like a spike, but for humans this will be literally the end of the world.

Geoengineering and terraforming our way out of this are sci-fi BS. People simply have no grasp of the scale of the processes here. Sending up a few aircraft to disperse some reagent will not solve the problem.

Re: The Methane Thread pt. 2

Unread postPosted: Sat 07 Oct 2017, 13:01:28
by onlooker
there you go it does not get much more scientifically straight forward than this process or more catastrophic. Dissident is a scientist who is not holding anything back and Cid has done extensive research citing credible expert sources. This is not something most people even would concede perhaps not even some scientists. I think we are on this site because we are curious and feel we can handle the truth. Well, the truth is we have triggered a Mass Extinction Event. and my question pertained to the possibility of it being halted and the answer was convincingly it will NOT be

Re: The Methane Thread pt. 2

Unread postPosted: Sat 07 Oct 2017, 14:58:16
by dohboi
Cid, many good points. But I'm pretty sure the ice cap in the last glaciation did not extend into that area, at least not the eastern-most regions. And aren't most of the clathrates below well below the surface of the ocean floor.

But yeah, looking for negative/damping feedbacks to save our sorry butts is really grasping at straws in this and in so many other cases. We're at the point that we are depending on 'unknown unknown' to pop out of the sky Deus Ex Machina like...basically, praying for a miracle, or worse, betting on a miracle to save us and most of the life on the planet.

Dis wrote: "These breakdown processes will not accelerate to offset CH4 emissions increases"

In fact, just the opposite, as I understand it. High levels of methane overwhelm the OH supply and so enhance the methanes global warming potential.

Re: The Methane Thread pt. 2

Unread postPosted: Sun 08 Oct 2017, 23:36:29
by Cid_Yama
OH depletion extends the half-life of methane.

Re: The Methane Thread pt. 2

Unread postPosted: Mon 09 Oct 2017, 08:49:07
by onlooker
Talk about a dastardly reinforcing loop. Methane accumulation and Oxygen Depletion

Re: The Methane Thread pt. 2

Unread postPosted: Tue 10 Oct 2017, 00:01:29
by dissident
onlooker wrote:Talk about a dastardly reinforcing loop. Methane accumulation and Oxygen Depletion


Not O2, but OH. In the troposphere OH is formed thanks to attack on H2O by O3 (ozone). Ozone in the troposphere is formed via so-called pollution chemistry. So NOx contributes to O3 formation. In the stratosphere there is a different chemical regime where NOx actually acts to destroy O3 (the primary mode of formation is UV breakdown of O2 and subsequent reaction of atomic oxygen with O2). One could envision more H2O contributing to more OH, but that is not really the case. There is already enough H2O and increasing it can change the balances of dozens of reactions. Only a chemical model can give an idea of what the extra H2O would do. For all the model haters: there are no parameterizations involved, and the original chemical ODEs are coded up with laboratory determined rates (which are functions of temperature and sometimes pressure). The current chemistry climate models do not indicate any surge of OH formation that serves to cover up our mess.

Re: The Methane Thread pt. 2

Unread postPosted: Wed 11 Oct 2017, 23:54:22
by Cid_Yama
It was thought that the significant sources of methane emissions were known, including natural wetlands, rice agriculture lands, ruminant animals, and energy production. Recently, however, there have been studies indicating that there is an unrecognized source of methane that has been unaccounted for. This concept was initiated by Frankenberg and his colleagues when they determined higher than expected methane concentrations above tropical regions during the dry season. In their findings, they used a space-borne global methane detector, SCIAMACHY (scanning imaging absorption spectrometer for atmospheric chartography) for their CH4 readings. They noted a strong relationship between areas of unusually higher methane concentrations and the presence of evergreen forests (Frankenberg, 2005). It was previously thought that methanogenesis was a strictly anaerobic, bacterial process. In January 2006, Frank Keppler and his colleagues at the Max-Planck Institute for Nuclear Physics in Heidelberg, Germany published evidence of aerobic methanogenesis by certain plants, including leaves of ash (Fraxinus excelsior), leaves of beech (Fagus sylvatica), sweet vernal grass (Anthoxanthum odoratum), maize (Zea mays), and wheat (Triticum aestivum) (Keppler, 2006). It is not yet known if all plants are capable of aerobic methanogenesis.

Factors such as sunlight and increased temperature were shown to affect the amount of methane released from the plants in Keppler’s experiments.

Estimated emissions for terrestrial plants may constitute 10-30% of the annual total of methane released in the atmosphere (Lowe, 2006).

While I am in favor of rebuilding our forests, it may now be evident that reforestation would only enhance the greenhouse effect. Therefore, the only practical solution seems to be to reduce anthropogenic greenhouse gas emissions.

link

Re: The Methane Thread pt. 2

Unread postPosted: Mon 06 Nov 2017, 16:45:50
by dohboi
Thanks to aslr at asif for this:

2012 article entitled: "Locked greenhouse gas in Arctic sea may be 'climate canary'";

Nature, doi:10.1038/nature.2012.11988; discusses methane hydrates observed in the Canadian Beaufort Seafloor in as little as 290m of water depth:

http://www.nature.com/news/locked-green ... ry-1.11988

See also the associated article ) entitled: "Expedition to study methane gas bubbling out of the Arctic seafloor"

http://www.mbari.org/expedition-to-stud ... -seafloor/

Extract: "Paull’s work in the Arctic started in 2003, with an investigation into the enigmatic underwater hills called “pingo-like features” (PLFs) that rise out of the continental shelf of the Beaufort Sea. (Pingos are isolated conical hills found on land in some parts of the Arctic and subarctic.)
Over time, the focus of the team’s research has moved farther offshore, into deeper water. Their second expedition in 2010 looked at diffuse gas venting along the seaward edge of the continental shelf. The 2012 expedition will focus on three large gas-venting structures on the continental slope, at depths of 290 to 790 meters (950 to 2,600 feet)."

images illustrates how a hypothetical submarine landslide on the continental slope could release sufficient methane gas to reach the surface. Probably the shallow water methane hydrates in the ESAS is of more concern, but the Clathrate Gun Hypothesis cannot be ignored in the broader Arctic Basin.