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Date: December 16, 2020 at 06:51:29
From: Akira, [DNS_Address]
Subject: Methane emissions from fossil fuels ‘severely underestimated’ |
URL: https://www.carbonbrief.org/methane-emissions-from-fossil-fuels-severely-underestimated |
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19.02.2020
Methane emissions from fossil fuels ‘severely underestimated’
"Human-caused emissions of methane from the extraction and use of fossil
fuels may have been “severely underestimated”, a new study suggests.
The research indicates that “natural” emissions of fossil methane, that seep
out of deeply-held reserves, make up a much smaller fraction of total
methane emissions than previously thought.
This means that the levels of fossil methane in the atmosphere are likely
being driven by the methane escaping as coal, oil and natural gas are mined,
drilled and transported.
The implication is that methane emissions from fossil fuels are 25-40%
higher than earlier estimates suggest, the lead researcher tells Carbon Brief.
The findings indicate that “the fossil-fuel industry is likely responsible for an
even larger proportion of recent climate change than we previously
thought”, a scientist not involved in the study tells Carbon Brief. However,
there is also “greater opportunity” to cut emissions, she says, through
“fixing leaks in natural gas extraction and distribution networks”.
Fossil methane
Methane is a potent greenhouse gas and is second only to CO2 in terms of
how much it contributes to global warming.
Although more short-lived in the atmosphere than CO2, methane packs
more of a warming punch – it is around 28-34 times (pdf) more powerful
over a 100-year period (though there are other ways to compare methane’s
warming impact with CO2).
There are two main types of methane: “biogenic”, produced from plants and
animals, and “fossil”, which has been locked up underground for millions of
years.
The new study, published in Nature, focuses on emissions of fossil methane.
These are most commonly associated with the extraction and transport of
fossil fuels – such as leaks from coal mining and flaring from oil and gas
drilling – but they have “natural” sources as well.
There are four main ways that fossil methane escapes into the atmosphere
naturally. These include onshore seeps (including oil and gas seeps, mud
volcanoes and gas-bearing springs), submarine (offshore) seeps, “diffuse
microseepage” from oil and gas-bearing sedimentary rocks, and geothermal
and volcanic formations.
The new study suggests that the amount of methane being emitted in these
natural ways has been overestimated.
Fingerprints
Scientists can analyse the precise makeup of methane molecules to
determine their likely origin. Key to this is the “fingerprint” of carbon-14
(14C) – a naturally-occurring isotope of carbon, explains lead author Dr
Benjamin Hmiel, a postdoctoral associate at the University of Rochester in
New York state. He tells Carbon Brief:
“Fossil sources have been isolated from the atmosphere for a very long time
– millions of years. Thus, all of the 14C has undergone natural radioactive
decay and there are no 14C molecules left. Alternatively, biologic sources –
such as wetlands, rice agriculture, cow burps – readily exchange their
carbon with the atmosphere and contain a quantity of 14C similar to that of
atmospheric CO2 at the time of emission.”
So, in short, scientists know when methane originated in deeply-held fossil
sources because it has no carbon-14. This is known as “14C-free methane”
For their study, the researchers collected samples of air from ice cores
drilled out of Greenland and Antarctic ice sheets. The ice traps tiny bubbles
of air, built up in layers with new snowfall year after year. By cutting out a
cylinder of ice down through the sheet, scientists can reconstruct a timeline
of the makeup of the atmosphere going back thousands of years.
The new record spans around 1750-2013, which “captures the evolution of
atmospheric 14CH4 [carbon-14 held in methane] since the pre-industrial
era”, the paper says. By quantifying the ratio of fossil to biogenic methane in
the air samples, the researchers reconstructed the signature of 14CH4 for
more than 250 years.
The charts below show what is revealed by their new record. The upper
chart shows the global concentration of methane in the atmosphere from
mid-18th century, while the lower chart shows the reconstruction of 14CH4
(green line) in the atmosphere since 1850. The individual dots show the 14C
measurements taken from ice cores at different sites.
Upper chart shows global CH4 mole fraction in parts per billion (ppb),
reconstructed from ice core data. Lower chart shows a reconstructed
history of atmospheric 14CH4 from the new study (green line). Dotted green
line shows two standard deviation uncertainty range. Blue line shows 14CH4
signature from biogenic sources. Individual dots show measurements from
specific ice cores. Source: Hmiel et al. (2020)
The lower chart shows how the 14C signature of methane emissions
changed as the industrial revolution got underway. The concentration of
atmospheric 14C declined as more 14C-free methane was emitted into the
atmosphere.
This is “coincident with the timing of significant growth in the use of fossil
fuels”, says Hmiel.
In contrast, the new record suggests that before 1870, “the quantity of
natural fossil methane seepage is very small – no more than 1% of the total
methane source today”, notes Hmiel.
Previous estimates put natural fossil methane emissions at around 40-60m
tonnes of methane per year, the paper says. The new study finds they are
more likely to be of the order of 1.6m tonnes per year, with a maximum of
5.4m tonnes per year. This suggests that natural emissions are “10 times
smaller than previously thought”, says Hmiel.
Going nuclear
The chart above takes a dramatic turn around the middle of the 20th
century. This is because of a complicating factor: nuclear technology.
There are two ways that the nuclear industry has affected the amount of
14C in the atmosphere. The first was nuclear-bomb testing above ground,
which began in 1945 and added a substantial quantity of 14C into the air,
explains Hmeil:
“This is known as the bomb pulse, which although the testing was outlawed
via international treaties in 1963,…caused a major perturbation of the
amount of 14C in the atmosphere, which complicates the simple
segregation of ‘fossil’ and ‘biologic’ methane due to how quickly natural 14C
levels changed in the atmosphere.”
This effect can be seen in the blue line in the earlier chart, which shows a
huge spike in biogenic 14CH4 in the mid-20th century.
The BADGER, a 23 kiloton nuclear bomb tested on April 18, 1953, at the
Nevada Test Site. Credit: Everett Collection Historical / Alamy Stock Photo
The BADGER, a 23 kiloton nuclear bomb tested on April 18, 1953, at the
Nevada Test Site. Credit: Everett Collection Historical / Alamy Stock Photo
The second influence was from nuclear power plants, says Hmiel. Beginning
in the 1970s, nuclear power added “a very small, yet globally quantifiable,
amount of 14CH4”, he notes:
“This perturbation alters the 14CH4 signature we measure in the
atmosphere today without significantly affecting the total quantity of
methane that is part of our calculation in quantifying the fossil component of
the source.”
The upshot of the nuclear influences is that the new 14C record is less
reliable for assessing fossil methane after the middle of the 20th century,
the researchers say.
However, because the level of natural seepage only changes on very long
timescales – many thousands of years or more – says Hmiel, it “is not
expected to have changed over the last 250 years”.
‘Severely underestimating’
The findings indicate that “almost all fossil methane in the atmosphere
today is from anthropogenic emissions originating from the extraction and
use of fossil fuels”, Hmiel says.
This suggests that previous “bottom-up” inventories – which estimate
methane figures by multiplying the number of sources (such as livestock,
natural gas operations and landfills) by their likely emissions – “are severely
underestimating” emissions from fossil fuels, says Hmiel.
Human-caused fossil methane emissions are likely to have been
underestimated by 38-58m tonnes per year, the paper concludes –
equivalent to about 25-40% of recent estimates.
Other research has also suggested that bottom-up methane inventories are
not fully taking into account methane emissions from oil-and-gas
infrastructure. Yet, ironically, the short-lived plateau in rising atmospheric
methane concentrations between the late 1990s and early 2000s (see
earlier chart) has been linked to oil and gas industries in developed
countries reducing “fugitive” emissions of escaping methane.
There is a positive side to this finding, says Hmiel:
“Simply put, if the emissions from anthropogenic sources are larger than we
thought, then that puts more of the emissions under our domain and
agency. Whereas humanity has little control over ‘natural’ emissions as they
were going to occur anyway.”
For example, he adds, if “the emissions are coming from oil-and-gas
production, then by enacting regulations to force the industry to institute at
least improved reporting of them – or better yet, reducing them – then we
can limit the emissions of methane to the atmosphere and the warming they
cause”.
‘Unique and exceptional’
“This paper is important,” says Prof Rob Jackson, professor of Earth system
science at Stanford University and chair of the Global Carbon Project.
Jackson, who was not involved in the study, tells Carbon Brief:
“It’s possible we’ve overestimated methane emissions from natural geologic
seeps. If so, fossil-fuel activities are even worse for climate and the
environment than we thought.”
However, there are still “many things” that need to be checked, he adds:
“We need more measurements at natural geologic seeps right now. We
need to check the modelling and isotopic assumptions behind the paper’s
conclusions, too. Both should happen quickly.”
Methane bubbles rising above a cold seep site. Methane bubbles flow in a
small stream out of the sediment on an area of seafloor offshore Virginia
north of Washington Canyon. Quill worms, anemones, patches of bacterial
mat, pandalid shrimp, and a large red crab (Chaceon quinquedens) can be
seen in and along the periphery of the seepage area. Credit: NOAA
OKEANOS Explorer Program , 2013 ROV Shakedown and Field Trials
Methane bubbles rising above a cold seep site. Methane bubbles flow in a
small stream out of the sediment on an area of seafloor offshore Virginia
north of Washington Canyon. Quill worms, anemones, patches of bacterial
mat, pandalid shrimp, and a large red crab (Chaceon quinquedens) can be
seen in and along the periphery of the seepage area. Credit: NOAA
OKEANOS Explorer Program , 2013 ROV Shakedown and Field Trials
Dr Célia Sapart, a researcher at the Université Libre de Bruxelles who has
previously published research on analysing natural and human-caused
methane sources, says the new dataset is of “unique and of exceptional
quality”.
However, mirroring the comments of Prof Jackson, she tells Carbon Brief
that “partitioning between anthropogenic and natural – geological – fossil
emissions remains extremely difficult” and so “denser and longer datasets”
going back before 1850 would “be helpful to consolidate the quantitative
conclusions of this paper in the future”.
Dr Heather Graven, a senior lecturer on the global carbon cycle at Imperial
College London, says the findings indicate that “the fossil-fuel industry is
likely responsible for an even larger proportion of recent climate change
than we previously thought”. This means there is a “greater opportunity” to
cut these emissions, she tells Carbon Brief:
“It’s critical that more effort is put into methane emissions mitigation, such
as fixing leaks in natural gas extraction and distribution networks. And we
need to monitor these mitigation efforts using atmospheric measurements,
including measurements of radiocarbon in atmospheric methane like those
made in this study.”"
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Responses:
[17410] [17411] [17412] [17413] [17414] |
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17410 |
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Date: December 16, 2020 at 07:51:23
From: JTRIV, [DNS_Address]
Subject: Re: good rebuttal to the methane doom scenario! |
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Hi Akira,
Well that seems to be a very good rebuttal to the
methane doom scenario.
"The research indicates that “natural” emissions
of fossil methane, that seep out of deeply-held
reserves, make up a much smaller fraction of total
methane emissions than previously thought.
This means that the levels of fossil methane in the
atmosphere are likely being driven by the methane
escaping as coal, oil and natural gas are mined,
drilled and transported."
So apparently instead of showing signs of explosive
growth the fossil methane releases have been
overestimated.
As I've been saying science simply doesn't support
the stupid methane hydrate catastrophe that the
doomsters cherish so much.
Cheers
Jim
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Responses:
[17411] [17412] [17413] [17414] |
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17411 |
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Date: December 16, 2020 at 08:52:20
From: Akira, [DNS_Address]
Subject: keep spinning |
URL: https://royalsocietypublishing.org/doi/10.1098/rspb.2020.1134 |
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"So apparently instead of showing signs of explosive
growth the fossil methane releases have been
overestimated. "
Wish all you will but the study actually says:
"The implication is that methane emissions from fossil fuels are 25-40%
higher than earlier estimates suggest, the lead researcher tells Carbon Brief.
The findings indicate that “the fossil-fuel industry is likely responsible for an
even larger proportion of recent climate change than we previously
thought”, a scientist not involved in the study tells Carbon Brief. However,
there is also “greater opportunity” to cut emissions, she says, through
“fixing leaks in natural gas extraction and distribution networks”.
If you're so certain of your conclusions, you should contact these scientists.
I'm sure they'd appreciate your input. You could save them years of
research! Tell them I sent you. :)
excerpts from
Riddles in the cold: Antarctic endemism and microbial succession impact
methane cycling in the Southern Ocean
July 2020
Abstract
Antarctica is estimated to contain as much as a quarter of earth's marine
methane, however we have not discovered an active Antarctic methane
seep limiting our understanding of the methane cycle. In 2011, an expansive
(70 m × 1 m) microbial mat formed at 10 m water depth in the Ross Sea,
Antarctica which we identify here to be a high latitude hydrogen sulfide and
methane seep. Through 16S rRNA gene analysis on samples collected 1 year
and 5 years after the methane seep formed, we identify the taxa involved in
the Antarctic methane cycle and quantify the response rate of the microbial
community to a novel input of methane. One year after the seep formed,
ANaerobic MEthane oxidizing archaea (ANME), the dominant sink of
methane globally, were absent. Five years later, ANME were found to make
up to 4% of the microbial community, however the dominant member of this
group observed (ANME-1) were unexpected considering the cold
temperature (−1.8°C) and high sulfate concentrations (greater than 24 mM)
present at this site. Additionally, the microbial community had not yet
formed a sufficient filter to mitigate the release of methane from the
sediment; methane flux from the sediment was still significant at 3.1 mmol
CH4 m−2 d−1. We hypothesize that this 5 year time point represents an
early successional stage of the microbiota in response to methane input.
This study provides the first report of the evolution of a seep system from a
non-seep environment, and reveals that the rate of microbial succession
may have an unrealized impact on greenhouse gas emission from marine
methane reservoirs....
(d) Summary
Here, we describe the formation and development of a novel methane seep
in the High Antarctic and quantify the evolution of the microbial community
over a 5 year time period. We found that it took up to 5 years for
microorganisms capable of forming a methane ‘sediment filter’ to develop.
In this time period we observed a sequential shift in the microbial
community to a group of taxa that were unexpected based on the
temperature, biogeochemical environment, and location. We also observed
a continued release of methane out of the sediment surface after this time
period. While the ultimate source of this methane remains unknown, the
ability of the CCS to inform our understanding of microbial succession and
to predict the magnitude of methane release from our oceans in response to
warming and ice shelf retreat are significant. Although we focus on one
particular area, the Ross Sea is an exciting area of methane research with
observed bottom simulating reflectors indicative of methane hydrates
present just north of our study site [51]. Our results suggest that the
accuracy of future global climate models may be improved by considering
the time it will take for microbial communities to respond to novel methane
input.
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Responses:
[17412] [17413] [17414] |
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17412 |
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Date: December 16, 2020 at 09:10:36
From: JTRIV, [DNS_Address]
Subject: Re: no spin here |
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Hi Akira,
Sorry, no spin here. This article talks about the
dangers of methane released from fossil fuels and
their conclusion is that methane emissions from
fossil fuels have been underestimated and that less
methane is being released from deep ocean hydrates
and permafrost.
Here again is the quote, no spin:
"The research indicates that “natural” emissions of
fossil methane, that seep out of deeply-held
reserves, make up a much smaller fraction of total
methane emissions than previously thought."
Are you not realizing this study, while expressing
concern over methane from fossil fuels also says
that there is less coming from the sources of ryan's
fear porn? Why the smart ass/dumbass comments about
me publishing? I'm just pointing out that the
science paper YOU shared says there is less methane
seeping from these natural sources which backs up
what I've been saying.
Are you also emotionally invested in the methane
doom like ryan or are you just stubbornly determined
to prove I'm wrong?
Cheers
Jim
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Responses:
[17413] [17414] |
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17413 |
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Date: December 16, 2020 at 09:55:25
From: Akira, [DNS_Address]
Subject: Re: no spin here |
URL: Riddles in the cold: Antarctic endemism and microbial succession impact methane cycling in the Southern Ocean |
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Nowhere did it suggest that deep underwater methane seepage doesn't
pose a potentially high risk of reaching the atmosphere. Which is why I
posted the intro & summary of another recent research paper, (linked again)
And I wasn't trying to be a smartass/dumbass. I was just trying to lighten
things up, but sounds like I hit a nerve instead.
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Responses:
[17414] |
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17414 |
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Date: December 16, 2020 at 10:19:01
From: JTRIV, [DNS_Address]
Subject: Re: no spin here |
URL: Glacial/interglacial wetland, biomass burning, and geologic methane emissions constrained by dual stable isotopic CH4 ice core records |
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Hi Akira,
You wrote:
> Nowhere did it suggest that deep underwater
methane
> seepage doesn't pose a potentially high risk of
> reaching the atmosphere.
But the paper you posted said:
"The research indicates that “natural” emissions of
fossil methane, that seep out of deeply-held
reserves, make up a much smaller fraction of total
methane emissions than previously thought."
So the paper you referenced says that the amount of
this deep methane that is seeping into the
atmosphere is less than expected. With huge amounts
of carbon locked in these hydrates there is always a
risk... but the folks measuring it and studying it
say that this methane is not increasing an the
scientists don't support the methane doom scenario
that certain media outlets like to promote.
Now the most recent paper you posted talks about how
methane is not seeping from Antarctica except for
one very small area that these scientists studied.
Sounds like more confirmation that this deep methane
isn't being released in quantities.
And again you should consider what happened 425,000
years ago during MIS 11. The world was much warmer
than today with sea levels 60 feet higher than today
and drastically reduced ice cover on Greenland and
West Antarctica.... yet no significant methane
release from deep ocean or permafrost locked methane
hydrates. I've linked a paper that analyzed this.
Cheers
Jim
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Responses:
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