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salbers

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Re: Toward Improved Discussions of Methane & Climate
« Reply #50 on: May 06, 2017, 10:53:35 PM »
The issue is not whether landmasses move from the rotational adis, they don't (except by tectonic movements which is totally different).  the rotational axis itself shifts, tilting or wobbling its position relative to the sun.  this is a historical cycle that normally does affect the cycle of glacial and interglacial periods.  however, climate change is progressing far more rapidly than any recent period, so i don't think any major earth changes that happen over a thousand years from now are particularly relevant today.  i DO think it's important to understand this in the context of paleoclimate data.
Indeed the Milankovitch cycles are important in the paleoclimate context. More specifically there are changes in the Earth axis tilt. Precession will also change which hemisphere is closest to the sun during a particular season. For example presently Antarctica has its summer when the Earth is near perihelion, so there is more reflection by the ice sheet. The lowers the Earth's overall temperature. A third cycle is changes in the eccentricity, so this would modulate the precession effect.

VaughnAn

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Re: Toward Improved Discussions of Methane & Climate
« Reply #51 on: May 10, 2019, 06:44:21 AM »
Paul Beckwith recently posted a video where he describes the short term effects of methane being about 150 times that of carbon dioxide.  With methane concentrations being about 1.8ppm if we multiply 1.8 X 150 we get a short term co2e of 270ppm.  The standard conversion is about 25 times over a 100 year time span which gives us a CO2e of 45ppm CO2e over a 100 year time span.  However since we are dumping so much methane into the atmosphere it seems we should be using the 270 CO2e number when discussing the very short term effects of methane; such as the next 3 years.  Along with Nitrous oxide being at about 0.33 ppm with a multiplier of 296 we get a nitrous oxide CO2e of about 97ppmCO2e  If we add the short term CO2e of these 2 gasses to the 411ppm of CO2 we get a total short term CO2e of 778 CO2e. 
This number seems more compatible with what is happening in the atmosphere concerning climate change right now or are these numbers giving me a false sense of alarm?
Paul Beckwith talks about these 2 gasses in his video and the is a part 2 to this linked video:

https://paulbeckwith.net/2019/04/21/arctic-emissions-of-nitrous-oxide-worse-than-expected-radio-ecoshock-mention-on-counterpunch/

Laurent

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Re: Toward Improved Discussions of Methane & Climate
« Reply #52 on: May 16, 2019, 09:45:09 AM »
Only the instantaneous global warming potential is consistent with honest and responsible greenhouse gas accounting

https://www.earth-syst-dynam-discuss.net/esd-2018-22/esd-2018-22.pdf

...

oren

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Re: Toward Improved Discussions of Methane & Climate
« Reply #53 on: May 16, 2019, 10:14:07 AM »
I agree. As atmospheric methane is constantly replenished and its level is in fact even going up, it makes absolutely no sense to assume it will follow its 100 year removal curve. Current forcing sees current methane. When (IF) all anthropogenic methane emissions stop, then we can talk about the rate of atmospheric removal of methane, adjusted by the rate of natural/feedback methane emissions that will continue.

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Re: Toward Improved Discussions of Methane & Climate
« Reply #54 on: May 16, 2019, 10:15:04 AM »
If we add the short term CO2e of these 2 gasses to the 411ppm of CO2 we get a total short term CO2e of 778 CO2e. 


I think you need to go through the same exercise at the beginning of the industrial revolution for an apples to apples comparison.

782 ppm CO2 equivalent seems reasonable. What was the number 200 years ago. Methane and nitrous oxide existed back then as well.

Tor Bejnar

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Re: Toward Improved Discussions of Methane & Climate
« Reply #55 on: May 16, 2019, 03:09:17 PM »
Laurent and Oren, I'm so glad to see your posts.  It matches my sense from a year or so ago, but I doubt I wrote anything, figuring that I must be missing something.

A similar 'argument' can be made for H2O forcing.  Even as increasing atmospheric H2O is a consequence of global warming and any H2O molecule has a short stay in the air, its "instantaneous global warming potential" is what matters, not the half-life of the airborne-ness of a molecule.
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VaughnAn

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Re: Toward Improved Discussions of Methane & Climate
« Reply #56 on: May 17, 2019, 05:59:15 AM »
Thanks for your input Lauren, Oren, and Tor.  That confirms my thinking.  So, we are really facing a much worse mess based on this reasoning.  This also helps explain why other climate scientists are claiming that the rate of change in the climate system is happening "much faster than expected."  I think my cause for alarm is more than justified.  we really should be using the "immediate" methane CO2e of 150x instead of the 100 year methane CO2e of about 28x.

Yes, this is on the back or more water vapor as well.  Time to get out the waders. 

sidd

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Re: Toward Improved Discussions of Methane & Climate
« Reply #57 on: May 17, 2019, 09:33:56 AM »
Climate models already do use the "immediate" impact of methane and everything else. They use the modtran codes and derivatives to calculate instantaneous radiative imbalance. Then they integrate over time to get the long term results. And thats the right way to do it.

sidd

Tor Bejnar

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Re: Toward Improved Discussions of Methane & Climate
« Reply #58 on: May 17, 2019, 07:16:10 PM »
I'm sure Sidd is correct.  For laypersons like me, the formula to predict/forecast how much methane will be contributing to CO2e goes something like: Current-methane - Decayed-into-CO2 methane + New-methane.  I'll leave it to the atmospheric chemists to discern if the removal rate (or half life) is 22 years or 88 years or whatever, and a more accurate representation of the formula (to boot)!  [For CO2, the formula is something like:  Current-CO2 + New-CO2 - CO2-taken-up-by-nature-quickly [oceans, plants] - CO2-taken-up-by-geological-processes [not a humankind-friendly component in the formula]].

The 'thing' that has bothered me has been how frequently 'the press' talks about the removal rate of a methane molecule, which I consider to be a side issue until the day we seriously (I mean really do it) reduce methane emissions. 
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VaughnAn

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Re: Toward Improved Discussions of Methane & Climate
« Reply #59 on: May 18, 2019, 05:16:16 AM »
According to what I am understanding about the numbers I am seeing used for the Paris Agreement and IPCC Protocol a 28x number to determine CO2e is being used.  This is a far cry from the immediate 150x for methane being discussed.  Maybe the models sidd is referring to use the 150x multiplier but it appears that the IPCC discussions must use the 28x multiplier per the agreement.  This would underestimate immediate effects thusly:
Current concentration of methane = 1.88ppm.
1.88ppm methane x 28CO2e/methane = 53ppmCO2e
1.88ppm methane x 150CO2e/methane = 282ppmCO2e
This is a difference of 229CO2e which should have an immediate effect from methane greater than 50% of current CO2 concentration.  This would seem to have a significant effect on calculations of the immediate effects of methane.


https://www.ghgprotocol.org/sites/default/files/ghgp/Global-Warming-Potential-Values%20%28Feb%2016%202016%29_1.pdf

sidd

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Re: Toward Improved Discussions of Methane & Climate
« Reply #60 on: May 18, 2019, 06:17:43 AM »
Re: " Maybe the models sidd is referring to use the 150x multiplier "

Grr, I have not made myself clear. Models have no concept of "multipliers." They use a representative concentration pathway (RCP, CMIP5) or a shared socioecoconomic pathway (SSP, CMIP6) and use the concentration at a given time to calculate the instantaneous radiative forcing using the MODTRAN/successor codes. Then they integrate this calculation in time for the cumulative heating. This implicitly includes everything that is simplistically called a "multiplier." They also have the atmospheric chemistry modules that calculate decay of methane and other unstable greenhouse gases, and they have fluxes for water vapour, and CO2 and CH4 and many other fluxes in/out of the atmosphere/ocean/land.

The Paris agreement for 2.0C was done using RCPs and CMIP5. That used a straight scaling of RCP2.5 .  I dont know what the hell the 1.5 C target uses.

"Multipliers" are a hopelessly simplistic concept to use for the incredibly varied gamut of radiative forcing by greenhouse gases. Use the models instead.

sidd

oren

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Re: Toward Improved Discussions of Methane & Climate
« Reply #61 on: May 18, 2019, 06:49:08 PM »
While the models use the correct fomulas as explained by sidd, multipliers and CO2eq are used in simplified communications about the issue, and are important as well when trying to educate the masses. I think the CO2eq numbers communicated should be higher.

Steven

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Re: Toward Improved Discussions of Methane & Climate
« Reply #62 on: May 18, 2019, 08:34:29 PM »
Current concentration of methane = 1.88ppm.
1.88ppm methane x 28CO2e/methane = 53ppmCO2e
1.88ppm methane x 150CO2e/methane = 282ppmCO2e
This is a difference of 229CO2e which should have an immediate effect from methane greater than 50% of current CO2 concentration.

That calculation is nonsense.

You are using global warming potential (GWP), which is defined for emissions rather than concentrations.  It makes no sense to multiply those numbers by the atmospheric methane concentration. 

Moreover, GWP is defined in terms of mass rather than volume.  You are using parts per million volume, but you didn't take into account that a CO2 molecule is almost 3 times heavier than a methane molecule.

I think it's more instructive to look directly at radiative forcing rather than GWP.  Radiative forcing is about 3 times higher for carbon dioxide than for methane (since preindustrial), and in the past few years it is rising almost 10 times faster for carbon dioxide than for methane:


https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2016GL071930

See also this thread: https://forum.arctic-sea-ice.net/index.php/topic,2383.0.html

Tom_Mazanec

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Re: Toward Improved Discussions of Methane & Climate
« Reply #63 on: May 29, 2019, 09:42:40 PM »
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Re: Toward Improved Discussions of Methane & Climate
« Reply #64 on: May 29, 2019, 10:05:27 PM »
 .. well Frack me .. b.c.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

Susan Anderson

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Re: Toward Improved Discussions of Methane & Climate
« Reply #65 on: June 13, 2019, 09:10:07 AM »
Unexpected surge in methane levels:
https://climatenexus.org/climate-change-news/methane-surge/

"Freedom gas" "molecules of freedom" - ugh!!!

bligh8

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Re: Toward Improved Discussions of Methane & Climate
« Reply #66 on: June 18, 2019, 06:08:43 PM »
Rising methane may thwart efforts to avoid catastrophic climate change

"If the world were on track to meet the Paris Agreement goal of less than 2 degrees Celsius of global warming, methane levels in the atmosphere would theoretically be dropping. Instead, they have been rising since 2007, and shooting up even faster since 2014. A perspective published in the journal Science discusses the potential causes and consequences of our planet's out-of-control methane.

"Methane decays in the atmosphere faster than carbon dioxide does, but it is a far more powerful greenhouse gas. According to the U.S. Environmental Protection Agency, a molecule of methane will cause 28-36 times more warming than a molecule of carbon dioxide over a 100-year period. Recent data shows that methane concentrations in the atmosphere have risen from about 1,775 parts per billion in 2006 to 1,850 parts per billion in 2017."

https://phys.org/news/2019-06-methane-thwart-efforts-catastrophic-climate.html

vox_mundi

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Re: Toward Improved Discussions of Methane & Climate
« Reply #67 on: June 18, 2019, 06:14:59 PM »
Good post bligh8 - I was in the process of posting the same thing - further info on the subject

Rising Methane May Thwart Efforts to Avoid Catastrophic Climate Change
https://phys.org/news/2019-06-methane-thwart-efforts-catastrophic-climate.html

... Scientists aren't sure why methane levels are rising. A 2017 study attributes about half of the increase to cows and other ruminant livestock, which burp methane as they digest food. Another contributing factor could be that people are releasing more fossil fuel emissions while burning less wood and other biomass.

In Mikaloff Fletcher's view, the most alarming possibilities are the ones we have little control over. Rising temperatures could be triggering wetlands to release more methane, and changes in atmospheric chemistry could be slowing the rate at which methane breaks down.



Open Access: Sara E. Mikaloff Fletcher et al. Rising methane: A new climate challenge, Science (2019)

----------------------------

Seaweed Feed Additive Cuts Livestock Methane; Questions Remain
https://phys.org/news/2019-06-seaweed-additive-livestock-methane-poses.html

.. If seaweed feed supplement is a viable option to make a difference globally, the scale of production would have to be immense, Hristov noted. With nearly 1.5 billion head of cattle in the world, harvesting enough wild seaweed to add to their feed would be impossible. Even to provide it as a supplement to most of the United States' 94 million cattle is unrealistic.

"To be used as a feed additive on a large scale, the seaweed would have to be cultivated in aquaculture operations," he said. "Harvesting wild seaweed is not an option because soon we would deplete the oceans and cause an ecological problem."

"We know that it is effective in the short term; we don't know if it's effective in the long term," Hristov explained. "The microbes in cows' rumens can adapt to a lot of things. There is a long history of feed additives that the microbes adapt to and effectiveness disappears. Whether it is with beef or dairy cows, long-term studies are needed to see if compounds in the seaweed continue to disrupt the microbes' ability to make methane."

There are also questions about the stability over time of the active ingredients—bromoforms—in the seaweed. These compounds are sensitive to heat and sunlight and may lose their methane-mitigating activity with processing and storage, Hristov warned.

Palatability is another question. It appears cows do not like the taste of seaweed—when Asparagopsis was included at 0.75 percent of the diet, researchers observed a drop in the feed intake by the animals.

... "But methane from animal agriculture is just 5 percent of the total greenhouse gases produced in the United States—much, much more comes from the energy and transportation sectors," Hristov said.
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Tor Bejnar

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Re: Toward Improved Discussions of Methane & Climate
« Reply #68 on: June 18, 2019, 06:48:54 PM »
Quote
Palatability is another question. It appears cows do not like the taste of seaweed—when Asparagopsis was included at 0.75 percent of the diet, researchers observed a drop in the feed intake by the animals.
When doing field geology on the coast of New Zealand, there were 'always' cows eating seaweed at low tide, walking among the slippery boulders to get to their food-of-choice. (stock picture attached)

For decades there were cows who at lakeweed in the St. Marks River - again, this was these cows preferred diet.  (The cows were evicted due to cow rear-end 'water pollution'.)

(reference)
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vox_mundi

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Re: Toward Improved Discussions of Methane & Climate
« Reply #69 on: June 18, 2019, 07:50:55 PM »
Quote
Palatability is another question. It appears cows do not like the taste of seaweed—when Asparagopsis was included at 0.75 percent of the diet, researchers observed a drop in the feed intake by the animals.
When doing field geology on the coast of New Zealand, there were 'always' cows eating seaweed at low tide, walking among the slippery boulders to get to their food-of-choice. (stock picture attached)

For decades there were cows who at lakeweed in the St. Marks River - again, this was these cows preferred diet.  (The cows were evicted due to cow rear-end 'water pollution'.)
...

Comparing the taste of the two is like comparing a barrel cactus and watermelon..

The Bull Kelp the cows appear to be eating is in the Ochrophyta phylum; the methane suppressing seaweed, Asparagopsis, is in the Rhodophyta phylum. Also, it doesn't share the relevant enzymes. Though, it appears to taste better.

Edit: My bad; cactus and watermelon are in the same phylum, (Magnoliophyta- flowering plants ). A better comparison would be cactus and club moss
« Last Edit: June 18, 2019, 09:15:11 PM by vox_mundi »
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

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Tor Bejnar

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Re: Toward Improved Discussions of Methane & Climate
« Reply #70 on: June 18, 2019, 08:03:12 PM »
Bummer!  :'(
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Ken Feldman

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Re: Toward Improved Discussions of Methane & Climate
« Reply #71 on: July 17, 2019, 01:49:38 AM »
This linked study from April 2019 finds that shale gas (from fracking), is lighter in 13C than traditional natural gas and that fracked natural gas may be the cause of the increasing methane levels in the past decade.

https://www.biogeosciences-discuss.net/bg-2019-131/bg-2019-131.pdf

Quote
Is Shale Gas a Major Driver of Recent Increase in Global Atmospheric Methane?

Robert W. Howarth

Abstract. Methane has been rising rapidly in the atmosphere over the past decade, contributing to global climate change. Unlike the late 20th  Century when the rise in atmospheric methane was accompanied by an enrichment in the heavier carbon stable isotope (13C) of methane, methane in recent years has become more depleted in 13C.  This depletion has been widely interpreted to indicate a primarily biogenic source for the increased methane.  Here we show that the change may instead be associated with emissions from shale gas and shale oil development.  While methane in conventional natural gas is enriched in 13C relative to the atmospheric mean, shale gas is depleted in 13C relative to this atmospheric level.   Correcting for this difference, we conclude that emissions from shale gas production in North America over the past decade may well be the leading cause of the increased flux of methane to the atmosphere.   Increased fluxes from biogenic sources such as animal agriculture and wetlands are far less important than indicated by some other recent papers using 13C data.

Quote
3. What is shale gas?

Shale gas is a form of unconventional natural gas (mostly methane) held tightly in shale rock formations.  Conventional natural gas, the dominant form of natural gas produced during the 20th Century, is composed largely of methane that migrated upward from the underlying sources such as shale rock over geological time, becoming trapped under a 10 geological seal (Fig. 2-A). Until this century, shale gas was not commercially developable. The use of a new combination of technologies in the 21st century – high precision directional drilling, high-volume hydraulic fracturing, and clustered multiwall drilling pads -- has changed this. In recent years, global shale gas production has exploded 14-fold, from 31 billion m3 per year in 2005 to 435 billion m3 per year in 2015 (Fig. 2-B), with 89% of this production in the United States and 10% in Canada (EIA 2016). Shale gas accounted for 63% of the total increase in natural gas production globally over the past decade 15 (EIA 2016, IEA 2017). The US Department of Energy predicts rapid further growth in shale gas production globally, reaching 1,500 billion m3 per year by 2040 (EIA 2016; Fig. 2-B).

Several studies have shown that theδ13C signal of methane from shale gas is often lighter (more depleted in 13C) than that from conventional natural gas (Golding et al. 2013; Botner et al. 2018). Here, we use the data from Figure 1 in the review 20 by Golding et al. (2013) that were explicitly identified as shale gas. The samples are from the New Albany shale (Martini et al. 1998), the Antrim shale (McIntosh et al. 2002), and an organic-rich shale in the northern Appalachian basin (Osborn and McIntosh 2010). Note that these studies appear to be the only ones included in theδ13C methane data repository published by Sherwood et al. (2017), which is the data set underlying the analysis by Schwietzke et al.(2016). Out of 61 data points for shale gas in the Golding et al. (2013) figure, only 5 had δ13C values similar to those for conventional natural gas, while many 25 samples more closely resembled the signal for biogenic gas. From the 61 values, we calculate a mean value δ13C for shale gas of -51.4 o/oo , with a 95% confidence limit of ± 1.2 o/oo. Thus, emissions of methane from shale gas are on average depleted in 13C relative to atmospheric methane, while methane from conventional natural gas is more 13C-enriched than atmospheric methane.

It should perhaps not be surprising that the δ 13C of methane from shale gas tends to be lighter than for conventional natural gas. In the case of conventional gas, the methane has migrated over geological time frames from the shale and other source rocks through permeable rocks until trapped below a seal (Fig. 2-A). During this migration, some of the methane is likely oxidized by bacteria, perhaps using iron (III) or sulfate as the source of the oxidizing power (Whelan et al. 1986; Rooze et al. 2016). Partial consumption of methane by bacteria would fractionate the methane by preferentially consuming the lighter 12C isotope and so, gradually enriching the remaining methane in 13C (Baldassare et al. 2014), resulting in a δ13C signal that is
less negative. The methane in shales, on the other hand, is tightly held in the rock formation and therefore less likely to have been subject to bacterial oxidation and the resulting fractionation. The expectation, therefore, is that methane in conventional natural gas should be heavier and less depleted in 13C than is the methane in shale gas.

vox_mundi

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Re: Toward Improved Discussions of Methane & Climate
« Reply #72 on: August 15, 2019, 05:53:17 PM »
Offshore Oil and Gas Rigs Leak More Greenhouse Gas Than Expected
https://phys.org/news/2019-08-offshore-oil-gas-rigs-leak.html

Using a laser-based instrument mounted on small fishing boats, the researchers estimated methane emissions from eight North Sea production platforms off the coasts of England and Scotland. Contrary to current expectations, they found that all the sampled offshore installations leaked even when they were not conducting operations expected to cause methane emissions. On average, methane leakage occurring during normal operations more than doubles each installations' reported emissions to the U.K."s National Atmospheric Emission Inventory.

In an article published Aug. 2 in the journal Atmospheric Chemistry and Physics, the researchers noted that previously reported leakage from operating oil and gas platforms appear low: 0.13 percent of production by U.K. government estimates. However, the researchers found that an additional 0.19 percent occurred during normal operation. For the U.K., this additional 0.19 percent corresponds to an additional 330,000 cars on the road (an increase of 1 percent in registered U.K. vehicles), the researchers said. ...  Riddick said the .19 percent was a conservative estimate and the actual leakage could be greater.

... The researchers said the most recent findings raise concern that policymakers might not be receiving accurate estimates for methane leakage from off-shore oil and gas rigs. (... ya think)

Open Access: Stuart N. Riddick et al. Methane emissions from oil and gas platforms in the North Sea, Atmospheric Chemistry and Physics (2019)
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Tom_Mazanec

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Re: Toward Improved Discussions of Methane & Climate
« Reply #73 on: September 01, 2019, 12:45:51 AM »
The Trump Administration Just Loosened Methane Emissions Rules. Here's What To Know
https://time.com/5664449/epa-methane-emissions-rule/
Quote
Mann says the rollback is just a part of “a total full-frontal attack on environmental regulation under the current Administration.” He points to the EPA’s loosening of limits on carbon emissions, and the Administration’s desire to provide subsidies to the coal industry.

Other environmental experts and advocates also worry about the consequences of Thursday’s announcement.

“Today’s actions will create a tremendous amount of additional pollution we didn’t need to have, both from existing wells and new wells,” Siegel tells TIME.

“You cannot curb the climate change problem, you cannot avoid catastrophic warming, if you don’t curb methane along with carbon dioxide and other greenhouse gases,” says NRDC’s Doniger.

“This is an unnecessary leap backwards,” adds Rob Jackson, an environmental scientist at Stanford. “Very few people in the public or the industry want this rollback.”
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Tom_Mazanec

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Re: Toward Improved Discussions of Methane & Climate
« Reply #74 on: September 04, 2019, 07:01:54 PM »
Will Antarctic Ice Doom Us All?
https://www.sierraclub.org/sierra/will-antarctic-ice-doom-us-all-methane
Quote
For years, scientists have struggled to figure out exactly how much methane is trapped under the ice at the north and south poles and what it would mean for global temperatures if climate change melted enough ice to release that methane into the atmosphere. A new study published in Nature Communications provides the most comprehensive estimate to date: a staggering 80 to 480 gigatons. That’s a wide range, but even at the low end, it’s astonishing. For context, all the cattle and other domestic animals around the world produce an estimated .08 gigatons of methane annually. Eighty gigatons is 1,000 times that amount.
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Ken Feldman

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Re: Toward Improved Discussions of Methane & Climate
« Reply #75 on: September 04, 2019, 09:32:41 PM »
Methane emissions from the Permian oil field (in Texas, USA) have tripled in the past few years.

https://www.chron.com/business/energy/article/Permian-methane-emissions-back-on-the-rise-after-14412700.php

Quote
Methane emissions and pollution in the booming Permian Basin likely hit a new record high in the second quarter after taking a small, but surprising, dip early this year, according to a new study.

The report estimates that the volumes of methane from natural gas burned off or vented into the atmosphere averaged of 663 million cubic feet per day in the second quarter, which is more than triple the amount of pollution and waste from just two years ago, according to the Norwegian research firm Rystad Energy.

The Permian has undergone a massive increase in natural gas flaring and venting in recent years, driven by higher activity and a lack of gas pipelines near the oil wells. Companies mostly only drill for the more valuable crude oil in the Permian, but associated gas comes out of the wells. Many companies opt to simply burn much of the gas away at the wellhead rather than possibly lose money transporting and selling the cheap gas.

Tom_Mazanec

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Re: Toward Improved Discussions of Methane & Climate
« Reply #76 on: September 18, 2019, 08:30:43 PM »
Pa. environmental board will vet proposed rules restricting potent greenhouse gas emissions
https://www.penncapital-star.com/blog/pa-environmental-board-will-vet-proposed-rules-restricting-potent-greenhouse-gas-emissions/
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Three years after they were first announced, new regulations restricting methane emissions from existing natural gas wells will get a hearing before a statewide rulemaking body this year, Gov. Tom Wolf’s office said Tuesday.

The move comes as Republican President Donald Trump rolls back restrictions on the potent greenhouse gas.
SHARKS (CROSSED OUT) MONGEESE (SIC) WITH FRICKIN LASER BEAMS ATTACHED TO THEIR HEADS

Ken Feldman

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Re: Toward Improved Discussions of Methane & Climate
« Reply #77 on: October 02, 2019, 12:06:17 AM »
The linked paper is an open-access pre-print for discuss survey of global methane emissions for the decade ending in 2017.

https://climatehomes.unibe.ch/~joos/papers/saunois19essddis.pdf

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The Global Methane Budget 2000-2017 Marielle Saunois, et.al 2019

Abstract. Understanding and quantifying the global methane (CH4) budget is important for assessing realistic pathways to mitigate climate change. Atmospheric emissions and concentrations of CH4 are continuing to increase, making CH4 the second most important human-influenced greenhouse gas in terms of climate forcing, after carbon dioxide (CO2). Assessing the relative importance of CH4 in comparison to CO2 is complicated by its shorter atmospheric lifetime, stronger warming potential, and atmospheric growth rate variations over the past decade, the causes of which are still debated. Two major difficulties in reducing uncertainties arise from the variety of geographically overlapping CH4 sources and from the destruction of CH4 by short-lived hydroxyl radicals (OH). To address these difficulties, we have established a consortium of multi-disciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate new research aimed at improving and regularly updating the global methane budget. Following Saunois et al. (2016), we present here the second version of the living review paper dedicated to the decadal methane budget, integrating results of top-down studies (atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up estimates (including process-based models for estimating land surface emissions and atmospheric chemistry, inventories of anthropogenic emissions, and data-driven extrapolations).  For the 2008-2017 decade, global methane emissions are estimated by atmospheric inversions (top-down approach) to be 572 Tg CH4 yr-1 (range 538-593, corresponding to the minimum and maximum estimates of the ensemble), of which 357 Tg CH4 yr-1 or ~60% are attributed to anthropogenic sources (range 50-65%). This total emission is 27 Tg CH4 yr-1 larger than the value estimated for the period 2000-2009 and 24 Tg CH4 yr-1 larger than the one reported in the previous budget for the period 2003-2012 (Saunois et al. 2016). Since 2012, global CH4 emissions have been tracking the carbon intensive scenarios developed by the Intergovernmental Panel on Climate Change (Gidden et al., 2019). Bottom-up methods suggest larger global emissions (737 Tg CH4 yr-1, range 583-880) than top-down inversion methods, mostly because of larger estimated natural emissions from sources such as natural wetlands, other inland water systems, and geological sources. However the strength of the atmospheric constraints on the top-down budget, suggest that these bottom-up emissions are overestimated. The latitudinal distribution of atmospheric-based emissions indicates a predominance of tropical emissions (~65% of the global budget, <30°N) compared to mid (~30%, 30°N-60°N) and high northern latitudes (~4%, 60°N-90°N). Our analyses suggest that uncertainties associated with estimates of anthropogenic emissions are smaller than those of natural sources, with top-down inversions yielding larger uncertainties than bottom-up inventories and models. The most important source of uncertainty in the methane budget is attributable to natural emissions, especially those from wetlands and other inland waters. Some global source estimates are smaller compared to the previously published budgets (Saunois et al. 2016; Kirschke et al. 2013), particularly for vegetated wetland emissions that are lower by about 35 Tg CH4 yr-1 due to efforts to partition vegetated wetlands and inland waters. Emissions from geological sources are also found to be smaller by 7 Tg CH4 yr-1, and wild animals by 8 Tg CH4 yr-1. However the overall discrepancy between bottom-up and top-down estimates has been reduced by only 5% compared to Saunois et al. (2016), due to a higher estimate of freshwater emissions resulting from recent research and the integration of emissions from estuaries. Priorities for improving the methane budget include: i) a global, high-resolution map of water-saturated soils and inundated areas emitting methane based on a robust classification of different types of emitting habitats; ii) further development of process-based models for inland-water emissions; iii) intensification of methane observations at local scales (e.g., FLUXNET-CH4 measurements and urban monitoring to constrain bottom-up land surface models, and at regional scales (surface networks and satellites) to constrain atmospheric inversions; iv) improvements of transport models and the representation of photochemical sinks in top-down inversions, and v) development of a 3D variational inversion system using isotopic and/or co-emitted species such as ethane.

wili

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Re: Toward Improved Discussions of Methane & Climate
« Reply #78 on: October 02, 2019, 12:18:43 AM »
Thanks, Ken. Are there any specific findings in there that particularly stand out to you?
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

Ken Feldman

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Re: Toward Improved Discussions of Methane & Climate
« Reply #79 on: October 02, 2019, 12:41:30 AM »
The findings that stand out to me are that the increases are mostly from anthropogenic sources.  With all the hype that's given to "the permafrost is melting" or "methane craters are exploding in Siberia", that seems surprising.  However, if you follow what's been happening with fracking for natural gas and increased coal mining in China, it's not surprising.

Here's the summary on anthropogenic sources.

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Based on the ensemble of databases detailed above, total anthropogenic emissions were 366 [348-392] Tg CH4 yr-1 for the decade 2008-2017 (Table 3, including biomass and biofuel burning) and 334 [325-357] Tg CH4 yr-1 for the preceding decade 2000-2009.

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Global emissions of methane from fossil fuels, other industries and transport are estimated from four global inventories yielding 127 [111-154] Tg CH4 yr-1 for the 2008-2017 decade (Table 3), but with large differences in the rate of change during this period across inventories. The sector accounts on average for 35% (range 30-42%) of the total global anthropogenic emissions.

An average increase of 32 Tg methane emissions per year this decade compared to the previous decade.

By contrast, estimates of emissions from the ESAS have gone down.

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For geological emissions, the most used value has long been 20 Tg CH4 yr-1, relying on expert knowledge and literature synthesis proposed in a workshop reported in Kvenvolden et al. (2001), the author of this study recognising that this was a first estimation and needs revision. Since then, oceanographic campaigns have been organized, especially to sample bubbling areas of active seafloor gas seep bubbling. For instance, Shakhova et al. (2010; 2014) infer 8-17 Tg CH4 yr-1 emissions just for the Eastern Siberian Arctic Shelf (ESAS), based on the extrapolation of numerous but local measurements, and possibly related to thawing subseabed permafrost (Shakhova et al., 2015). Because of the highly heterogeneous distribution of dissolved CH4 in coastal regions, where bubbles can most easily reach the atmosphere, extrapolation of in situ local measurements to the global scale can be hazardous and lead to biased global estimates. Indeed, using very precise and accurate continuous land shore-based atmospheric methane observations in the Arctic region, Berchet et al. (2016) found a range of emissions for ESAS of ~2.5 Tg CH4 yr-1 (range [0-5]), 4-8 times lower than Shakhova’s estimates. Such a reduction in ESAS emission estimate has also been inferred from oceanic observations by Thornton et al. (2016a) with a maximum sea-air CH4 flux of 2.9 Tg CH4 yr-1 for this region.
...
Therefore, as discussed in Section 3.2.2, we report here a reduced range of 5-10 Tg CH4 yr-1 for marine geological emissions compared to the previous budget, with a mean value of 7 Tg CH4 yr-1.

Thawing permafrost on land also gets a lot of attention.  Here's how it contributes the current global methane budget.

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The thawing permafrost can generate direct and indirect methane emissions. Direct methane emissions rely on the release of methane contained in the thawing permafrost. This flux to the atmosphere is small and estimated to be at maximum 1 Tg CH4 yr-1 at present (USEPA, 2010a). Indirect methane emissions are probably more important. They rely on: 1) methanogenesis induced when the organic matter contained in thawing permafrost is released; 2) the associated changes in land surface hydrology possibly enhancing methane production (McCalley et al., 2014); and 3) the formation of more thermokarst lakes from erosion and soil collapsing. Such methane production is probably already significant today and could be more important in the future associated with a strong positive feedback to climate change (Schuur et al., 2015). However, indirect methane emissions from permafrost thawing are difficult to estimate at present, with very few data to refer to, and in any case largely overlap with wetland and freshwater emissions occurring above or around thawing areas. For instance, based on lake and soil measurements (Walter Anthony et al., 2016) found that methane emissions (~4 Tg CH4 yr-1) from thermokarst areas of lakes that have expanded over the past 60 years were directly proportional to the mass of soil carbon inputs to the lakes from the erosion of thawing permafrost. Here, we choose to report only the direct emission range of 0-1 Tg CH4 yr-1, keeping in mind that current wetland, thermokarst lakes and other freshwater methane emissions already likely include a significant indirect contribution originating from thawing permafrost. For the next century, it is estimated that 5-15% of the terrestrial permafrost carbon pool is vulnerable to release in the form of greenhouse gases, corresponding to 130-160 Pg C (Koven et al., 2015). The likely progressive release in the atmosphere of such an amount of carbon as carbon dioxide and methane may have a significant impact on climate change trajectory (Schuur et al., 2015). The underlying methane hydrates represent a substantial reservoir of methane, estimated up to 530 000 Tg of CH4 (Ciais et al., 2013). Although local to regional studies are conducted (e.g. Kuhn et al., 2018; Kohnert et al., 2017), present and future emissions related to this reservoir are difficult to assess for all the Arctic at the moment and still require more work.

So if we can decrease the use of fossil fuels, we can greatly reduce the methane concentrations in the atmosphere.