When we see records being broken and unprecedented events such as this, the onus is on those who deny any connection to climate change to prove their case. Global warming has fundamentally altered the background conditions that give rise to all weather. In the strictest sense, all weather is now connected to climate change. Kevin Trenberth
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Institute of Natural Resources, National Tomsk Research Polytechnic University, 30 Prospect Lenina, Tomsk 634050, Russia
2
International Arctic Research Center, University Alaska Fairbanks, Akasofu Building, Fairbanks, AK 99775-7320, USA
3
Pacific Oceanological Institute, Russian Academy of Science, 41 Baltiiskaya Street, Vladivostok 690022, Russia
4
Moscow Institute of Physics and Technology, 9 Institutskiy per., Dolgoprudny, Moscow Region 141701, Russia
5
Science and Education Center, Northern (Arctic) Federal University, Naberezhnaya Severnoy Dvini, 17, Arkhangelsk 163002, Russia
6
Skolkovo Institute of Science and Technology (Skoltech), 3, Nobel st., Innovation Center Skolkovo, Moscow 121205, Russia
*
Author to whom correspondence should be addressed.
Received 4 April 2019; accepted 3 June 2019; published 5 June 2019.
Abstract
This paper summarizes current understanding of the processes that determine the dynamics of the subsea permafrost–hydrate system existing in the largest, shallowest shelf in the Arctic Ocean; the East Siberian Arctic Shelf (ESAS). We review key environmental factors and mechanisms that determine formation, current dynamics, and thermal state of subsea permafrost, mechanisms of its destabilization, and rates of its thawing; a full section of this paper is devoted to this topic. Another important question regards the possible existence of permafrost-related hydrates at shallow ground depth and in the shallow shelf environment. We review the history of and earlier insights about the topic followed by an extensive review of experimental work to establish the physics of shallow Arctic hydrates. We also provide a principal (simplified) scheme explaining the normal and altered dynamics of the permafrost–hydrate system as glacial–interglacial climate epochs alternate. We also review specific features of methane releases determined by the current state of the subsea-permafrost system and possible future dynamics. This review presents methane results obtained in the ESAS during two periods: 1994–2000 and 2003–2017. A final section is devoted to discussing future work that is required to achieve an improved understanding of the subject.Open access: https://www.mdpi.com/2076-3263/9/6/251/htm
The sea surface above the East Siberian continental shelf of the Arctic Ocean is made up of broken ice and methane bubbling to the surface. Credit: Courtesy of Igor Semiletov, University of Alaska Fairbanks.
There are millions of tons of the powerful greenhouse gas methane trapped underwater in the continental shelf of the Arctic Ocean.
This methane had been held in place for thousands of years by a cap of frozen soil on the seabed. But now research at the University of Alaska in Fairbanks has found this methane is escaping into the atmosphere at faster and faster rates, adding to global warming in a feedback loop that accelerates the warming.
The study concentrated on the East Siberian Arctic Shelf. Natalia Shakhova, lead author on the study, says this particular area makes up about 25% of the Arctic shelf.
"Because the permafrost was thought to be stable and reliably preventing this methane escaping from the seabed deposits, this area has never been considered a source of methane to the atmosphere, never until very recently when we started investigating this area 10 years ago," she says.
Roughly 17 million tons of methane are released into the environment annually from this shelf.
"Arctic tundra is thought to be the major source of methane, natural methane, in the northern hemisphere, so it’s kind of comparable to terrestrial sources," Shakhova says. "For hundreds of thousands of years ... the permafrost on top of the sediment has been serving as a cap, as a seal, preventing the escape."
As the permafrost thaws, a phenomenon happening on land and under the sea, it becomes less efficient at containing greenhouse gases, like methane. And methane is a particularly nasty greenhouse gas, with one ton of methane packing the climate changing potential of at least 20 tons of carbon dioxide, Shakhova adds.
"The concentration of methane in the atmosphere is increasing much faster than that of carbon dioxide," she says. "The last 200 years, the concentration of methane in the atmosphere increased about three times."
Methane has a relatively short lifespan, 10 to 30 years, but it is converted to carbon dioxide — so still dangerous to the atmosphere.
One of the biggest concerns is this Arctic methane will create a dangerous loop, with the methane raising the temperatures, melting more of the permafrost and releasing more methane.
But, it's still possible this situation could be stemmed, or at least slowed.
"We better believe in science and in ourselves because I’m sure that we will be able to come up with ideas how to solve this problem, how to fix it, how to mitigate, how to maybe recover this methane," Shakhova says.
Is conventional modelling out of pace with speed and abruptness of global warming?
Greenpeace icebreaking ship, Arctic Sunrise, among broken floes of Arctic sea ice, photographed from the air. This image was taken in the Fram Strait, in the month that the sea ice coverage receded to the second lowest extent since records began. Photograph: Nick Cobbing
by Nafeez Ahmed, The Guardian, December 9, 2013
An ongoing US Department of Energy-backed research project led by a US Navy scientist predicts that the Arctic could lose its summer sea ice cover as early as 2016 – 84 years ahead of conventional model projections.
The project, based out of the US Naval Postgraduate School's Department of Oceanography, uses complex modelling techniques that make its projections more accurate than others.
A paper by principal investigator Professor Wieslaw Maslowski in the Annual Review of Earth and Planetary Sciences sets out some of the findings so far of the research project:
"Given the estimated trend and the volume estimate for October–November of 2007 at less than 9,000 km3, one can project that at this rate it would take only 9 more years or until 2016 ± 3 years to reach a nearly ice-free Arctic Ocean in summer. Regardless of high uncertainty associated with such an estimate, it does provide a lower bound of the time range for projections of seasonal sea ice cover."
The paper is highly critical of global climate models (GCM) and even the majority of regional models, noting that "many Arctic climatic processes that are omitted from, or poorly represented in, most current-generation GCMs" which "do not account for important feedbacks among various system components." There is therefore "a great need for improved understanding and model representation of physical processes and interactions specific to polar regions that currently might not be fully accounted for or are missing in GCMs."
According to the US Department of Energy describing the project's development of the Regional Arctic System Model (RASM):
"Given that the Arctic is warming faster than the rest of the globe, understanding the processes and feedbacks of this polar amplification is a top priority. In addition, Arctic glaciers and the Greenland Ice Sheet are expected to change significantly and contribute to sea level rise in the coming decades."
Such Arctic changes "could have significant ramifications for global sea level, the ocean thermohaline circulation and heat budget, ecosystems, native communities, natural resource exploration, and commercial transportation."
The regional focus of RASM permits "significantly higher spatial resolution" to represent and evaluate the interaction of "important fine-scale Arctic processes and feedbacks," such as:
"... sea ice deformation, ocean eddies, and associated ice–ocean boundary layer mixing, multiphase clouds as well as land–atmosphere–ice–ocean interactions."
The role of the Department of Energy in backing the research is not surprising considering that President Obama's national Arctic strategy launched in May is focused on protecting commercial and corporate opportunities related to control of the region's vast untapped oil, gas and mineral resources.
The model coheres with the predictions of several other Arctic specialists – namely ProfPeter Wadhams, head of polar ocean physics at Cambridge University and ProfCarlos Duarte, director of the Ocean Institute at the University of Western Australia – who see the disappearance of the Arctic sea ice in the summer of 2015 as likely.
Prof Wadhams is co-author of the controversial Nature paper which calculated the potential economic costs of climate change based on a scenario of 50 Gigatonnes (Gt) of methane being released this century from melting permafrost at the East Siberia Arctic Shelf (ESAS), a vast region of shallow-water covered continental crust. The scenario was first postulated by Natalia Shakhova and Igor Semiletov of the International Arctic Research Centre at the University of Alaska, Fairbanks.
In 2010, Shakhova's team published results showing that 7 teragrammes of methane was bubbling to the surface annually in the ESAS. Last month, she released a new paper in Nature Geoscience updating these findings on the basis of more rigorous measurements using an unmanned underwater vehicle with advanced sonar capability. She found that annual bottom water temperatures have increased over the last 14 years, correlating with a release of about 17 teragrammes of methane a year, accentuated by storms. This conservative estimate is more than double the earlier assessment.
However, the source of these methane emissions remains a matter of dispute, as other scientists investigating the phenomenon point out that while large deposits of methane hydrates could be breaking up, the other possibility is a slow leak of methane that has already gone on for hundreds of years. Christian Berndt, of the GEOMAR/Helmholz Centre for Ocean Research, has speculated that both phenomena could be going on at once, but he admits, "We have no proof."
Despite their latest study uncovering higher levels of methane than previously recognised, Shakhova has also distanced herself from the 'methane bomb' scenario she had once previously posited, noting a lack of direct evidence for the scenario.
"Ship-based observations show that methane concentrations in the air above the East Siberian Sea Shelf are nearly twice as high as the global average... Layers of sediment below the permafrost slowly emit methane gas, and this gas has been trapped for millennia beneath the permafrost. As sea levels rose at the end of the ice age, the shelf was once again covered by relatively warm ocean water, thawing the permafrost and releasing the trapped methane... In the short-term... methane has a global warming potential 86 times that of carbon dioxide."
Most scientists agree that more research is needed to determine the source and nature of these methane emissions.
But scientists also largely agree that an ice free Arctic in the summer could have serious consequences for the global climate. Some research has pointed out a link between the warming Arctic and changes in the jet stream, contributing to unprecedented weather extremes over the last few years. These extreme events in turn have dramatically impacted crop production in key food basket regions.
A landmark new study in Nature Climate Change finds the melting of the sea ice over the last 30 years at a rate of 8% per decade is directly linked to extreme summer weather in the US and elsewhere in the form of droughts and heatwaves. Lead study author Quihang Tang at the Institute of Geographic Sciences and Natural Resources Research in Beijing said:
"As the high latitudes warm faster than the mid-latitudes because of amplifying effects of melting ice, the west-to-east jet-stream wind is weakened. Consequently, the atmospheric circulation change tends to favour more persistent weather systems and a higher likelihood of summer weather extremes."
The new study supplements earlier research published in Geophysical Research Letters demonstrating a link between Arctic sea ice loss and extreme weather particularly in both the summer and winter, including prolongation of "drought, flooding, cold spells, and heat waves."
Last year Prof Duarte was lead author of a paper in the Royal Swedish Academy of Science's journal AMBIO warning that the Arctic was at risk of passing critical "tipping points" that could lead to a cascading "domino effect once the summer sea ice is lost." Prof Duarte said at the time:
"If set in motion, they can generate profound climate change which places the Arctic not at the periphery but at the core of the Earth system. There is evidence that these forces are starting to be set in motion. This has major consequences for the future of human kind as climate change progresses."
Methane burns as it escapes through a hole in the ice in a lagoon above the East Siberian Arctic Shelf. (Credit: Photo courtesy of Natalia Shakhova)
Check it out at methanetracker.org !!! Nov. 25, 2013 — The seafloor off the coast of Northern Siberia is releasing more than twice the amount of methane as previously estimated, according to new research results published in the Nov. 24, 2013, edition of the journal Nature Geoscience. The East Siberian Arctic Shelf is venting at least 17 teragrams of the methane into the atmosphere each year. A teragram is equal to 1 million tons. "It is now on par with the methane being released from the Arctic tundra, which is considered to be one of the major sources of methane in the Northern Hemisphere," said Natalia Shakhova, one of the paper's lead authors and a scientist at the University of Alaska Fairbanks. "Increased methane releases in this area are a possible new climate-change-driven factor that will strengthen over time."
Methane is a greenhouse gas more than 30 times more potent than carbon dioxide. On land, methane is released when previously frozen organic material decomposes. In the seabed, methane can be stored as a pre-formed gas or asmethane hydrates. As long as the subsea permafrost remains frozen, it forms a cap, effectively trapping the methane beneath. However, as the permafrost thaws, it develops holes, which allow the methane to escape. These releases can be larger and more abrupt than those that result from decomposition.
The findings are the latest in an ongoing international research project led by Shakhova and Igor Semiletov, both researchers at the UAF International Arctic Research Center. Their twice-yearly Arctic expeditions have revealed that the subsea permafrost in the area has thawed much more extensively than previously thought, in part due to warming water near the bottom of the ocean. The warming has created conditions that allow the subsea methane to escape in much greater amounts than their earlier models estimated. Frequent storms in the area hasten its release into the atmosphere, much in the same way stirring a soda releases the carbonation more quickly.
"Results of this study represent a big step forward toward improving our understanding of methane emissions from the East Siberian Arctic Shelf," said Shakhova. She noted that while the ESAS is unusual in its expansive and shallow nature, the team's findings there speak to the need for further exploration of the subsea Arctic. "I believe that all other Arctic shelf areas are significantly underestimated and should be paid very careful attention to." [Quite true, lots coming from shelves around Greenland.]
The East Siberian Arctic Shelf is a methane-rich area that encompasses more than 2 million square kilometers of seafloor in the Arctic Ocean. It is more than three times as large as the nearby Siberian wetlands, which have been considered the primary Northern Hemisphere source of atmospheric methane. Previous estimates performed for the ESAS suggested that the area was releasing 8 teragrams of methane into the atmosphere yearly.
During field expeditions, the research team used a variety of techniques -- including sonar and visual images of methane bubbles in the water, air and water sampling, seafloor drilling and temperature readings -- to determine the conditions of the water and permafrost, as well as the amount of methane being released.
Methane is an important factor in global climate change, because it so effectively traps heat. As conditions warm, global research has indicated that more methane is released, which then stands to further warm the planet. Scientists call this phenomenon a positive feedback loop.
"We believe that the release of methane from the Arctic, and in particular this part of the Arctic, could impact the entire globe," Shakhova said. "We are trying to understand the actual contribution of the ESAS to the global methane budget and how that will change over time."
Much of this debate kicked off because the said Nature paper
advances a hypothetical scenario for an abrupt Arctic methane release
over either a decade or several decades of about 50 gigatonnes (Gt), and
argues specifically that such a scenario is "likely." My own attempt to
understand the literature convinced me that the scenario should be
viewed as a serious possibility.
Tobis on the other hand is the
latest amongst several scientists offering scathing criticisms of that
scenario, which in his own words is "as close to impossible as anything
in earth science; actual geophysics refutes it." He begins with my first point, 1.
The 50 Gigatonne decadal methane pulse scenario was posited by four
Arctic specialists, and is considered plausible by Met Office scientists.
"Arctic
thawing may release in excess of 50 GT of C [Carbon], a very serious
matter... But Ahmed refers to the paper in support of a very different
assertion, that 50 GT of methane would be released... But the paper to
which he points says nothing of the sort. I conclude that he doesn't
really know what he is talking about. Specifically he has already shown
that he is confused about the distinction between methane releases and
CO2 releases."
However, the carbon release scenarios
from permafrost explored by the paper include both methane and carbon.
Here's what the paper says:
"The most important
determinant of whether release of frozen carbon happens as CO2 or CH4
[methane] is whether decomposition proceeds aerobically or
anaerobically... In anaerobic conditions, a greater proportion of soil
organic carbon decomposition is released as CH4, although not all of it
necessarily reaches the atmosphere."
Following this
paragraph, the paper cites several scenarios for large-scale releases
from permafrost carbon, including the 50-100 Gt carbon release I
mentioned.
Further down, the paper continues:
"Thawing
of the terrestrial permafrost will result in CO2 and CH4 emissions on
time scales of a few decades to several centuries."
So
Tobis is wrong in assuming that the carbon release scenarios the paper
is discussing are only CO2 - that isn't specified, so I'd assumed the
paper was open on whether the 50-100 Gt emissions were methane or
carbon.
This was a mistake, however. The paper makes clear that
although the scenarios are not clear on the precise quantification of
carbon dioxide compared to methane releases from permafrost thawing,
methane releases would be only be a small percentage of the overall
carbon release scenarios explored. So Tobis is ultimately correct - the
paper does not back up the specific scenario endorsed as likely by the Nature paper. I stand corrected on that.
Therefore,
the plausibility of the specific 50 Gt scenario rises and falls on the
credibility of the four Arctic specialists, including Dr. Natalia
Shakhova, who came up with the scenario in the first place. That leaves
point 1 only half intact, so we're left with:
1. The 50 Gigatonne decadal methane pulse scenario was posited by four Arctic specialists Tobis unfortunately addresses this with only an ad hominem attack on the expertise of these Arctic specialists:
"Whether we should be acknowledging the 'Arctic specialists' as actually expert is, frankly, the question at hand."
Tobis
goes through my other citations of the literature arguing that I am
confusing quantities and making unwarranted extrapolations. However, my
citations of this literature is simply to clarify that the literature
does not rule out potentially dangerous releases of Arctic methane. Does
Tobis manage to refute point 2. Arctic methane hydrates are
becoming increasingly unstable in the context of anthropogenic climate
change and it's impact on diminishing sea ice? No. Arctic methane hydrates are becoming increasingly unstable. I said nothing more, or less, than exactly that.
What about fact 3.
Multiple scientific reviews, including one by over 20 Arctic
specialists, confirm decadal catastrophic Arctic methane release is
plausible?
Tobis concedes "A couple of reviews do give
some support to this, but are vague about time scales." He then links to
what he describes as a "DOE report." Instead, the link goes through to a
Geophysical Research Letters
study, which, however, he completely ignores, instead quoting from the
original Review of Geophysics paper as follows:
"The risk of a rapid
increase in [methane] emissions is real but remains largely
unquantified..."
And he calls me confused!
He then argues
that there is "plenty of room for acceleration without hitting the
cataclysmic level. Further evidence doesn't support the immediacy of
that scenario at all."
But the Review of Geophysics paper does NOT
say that there is "plenty of room for acceleration without hitting the
cataclysmic level" - it says that:
"... significant increases in methane emissions are likely, and catastrophic emissions cannot be ruled out."
The
paper does NOT say available evidence "doesn't support the immediacy"
of a catastrophic scenario, but rather that "uncertainties are large,
and it is difficult to be conclusive about the time scales and
magnitudes of methane feedbacks."
"...
while many deep hydrate deposits are indeed stable under the influence
of rapid seafloor temperature variations, shallow deposits, such as
those found in arctic regions or in the Gulf of Mexico, can undergo
rapid dissociation and produce significant carbon fluxes over a period
of decades."
I think my fundamental contention - that
the scientific literature recognises the possibility of some sort of
catastrophic methane scenario - remains valid. Tobis is right, however,
to emphasise that there is very little evidence available on quantifying
that possibility.
In response to fact 4. Current methane levels are unprecedented,
Tobis says yes, but they are "not climbing rapidly", and therefore this
is mere "hype." My intention here was not to suggest that current
Arctic methane levels are definitive evidence of a catastrophe already
underway, but simply to note that it is wrong to say methane levels are
NOT rising. They are, and once again, Arctic specialists are concerned.
"The
CARVE science team is busy analyzing data from its first full year of
science flights. What they're finding, Miller said, is both amazing and
potentially troubling.
'Some of the methane and carbon dioxide
concentrations we've measured have been large, and we're seeing very
different patterns from what models suggest," Miller said. "We saw
large, regional-scale episodic bursts of higher-than-normal carbon
dioxide and methane in interior Alaska and across the North Slope during
the spring thaw, and they lasted until after the fall refreeze. To cite
another example, in July 2012 we saw methane levels over swamps in the
Innoko Wilderness that were 650 parts per billion higher than normal
background levels. That's similar to what you might find in a large
city.'
"Ultimately, the scientists hope their observations will
indicate whether an irreversible permafrost tipping point may be near at
hand. While scientists don't yet believe the Arctic has reached that
tipping point, no one knows for sure. 'We hope CARVE may be able to find
that "smoking gun," if one exists,' Miller said."
So
while NASA Arctic specialists say Arctic methane levels are "amazing"
and "potentially troubling," outside the range of most model
predictions, and possibly indicative that "an irreversible permafrost
tipping point" is near - a matter which "no one knows for sure" - Tobis
wants to interpret all the evidence as "refuting" any need for concern.
The
other problem is that Arctic monitoring is still poor, and might be
missing significant methane emissions. As Shakhova and her co-author
Igor Semiletov told the New York Times' Andy Revkin:
"It
is no surprise to us that others monitoring global methane have not
found a signal from the Siberian Arctic or increase in global
emissions... The number of stations monitoring atmospheric methane
concentrations worldwide is very few. In the Arctic there are only three
such stations - Barrow, Alert, Zeppelin - and all are far away from the
Siberian Arctic. We are doing our multi-year observations, including
year-round monitoring, in proximity to the source. In addition to
measuring the amount of methane emitted from the area, we are trying to
find out whether there is anything specific about those emissions that
could distinguish them from other sources. It is incorrect to say that
anyone is able to trace that signal yet."
Most Arctic
specialists recognise that there's simply not enough research to
justify dismissing the possibility of a catastrophe. That sword cuts
both ways, of course - equally, there's not enough research justifying
conclusions that we are definitely on the brink of a catastrophe.
On 5. The tipping point for continuous Siberian permafrost thaw could be as low as 1.5 C,
Tobis concedes this "is on the table," but that "it has nothing to do
with undersea methane." Um, I never said it had anything to do with
undersea methane.
On 6. Arctic conditions during the
Eemian interglacial lasting from 130,000 to 115,000 years ago are a
terrible analogy for today's Arctic, he writes: "as a response
to Chris Colose" this is a "terrible" response, "because Colose is not
relying on the Eemian but on the early Holocene as the analogous
period." Yes, Colose does refer to the early Holocene, but he also
repeatedly refers to the Eemian, the "Last Interglacial period between
130,000 to 120,000 years ago." In a previous article,
I'd already mentioned that in the early Holocene, the East Siberia
Arctic Shelf (ESAS) was "not an underwater shelf but a frozen landmass"
as reason to be sceptical that paleoclimate data provide a ready
analogue for the present.
Tobis then launches an ad hominem attack
on climate scientist Paul Beckwith, whom I quoted for this article, and
whom Tobis refers to as:
"'Prof' Paul Beckwith, the 'Professor Beckwith' who is a grad student at Ottawa U."
For
the record, earlier this year, Beckwith formally passed his PhD
examination on abrupt Arctic climate change at the Laboratory for
Paleoclimatology and Climatology, University of Ottawa, where he is
currently a part-time professor in climatology. Rather than addressing
Prof Beckwith's argument, Tobis wants to demean his reputation and
ignore his argument (which he fails to refute). Beckwith's full response
to Colose is here. Among Beckwith's points, he argues that neither the early Holocene nor Eemian offer good analogues for the present Arctic:
"Earth
tilt was larger, so Winter Northern Hemispheric solar radiation was
about 40 W/m2 lower than today at 60 degrees North. Thus, the ice formed
much more quickly and much thicker in the winter back then. Also, at
night much more heat was radiated out to space in the lower GHG world
then as compared to our 400 ppm levels today... the summertime Arctic is
not believed to be seasonally ice free during these periods. The last
time this happened was likely 2 or 3 million years ago... Colder winters
in the early Holocene and Last Interglacial and much colder nights (in
summers and winters then) meant much thicker and extensive ice formation
in winters, and slower melting at night, respectively."
If
I was to take Tobis' approach, I could have noted that Chris Colose is a
"grad student" at the University of Albany. I didn't, because it's
irrelevant.
Finally, Tobis takes on fact 7. Paleoclimate records will not necessarily capture a large, abrupt methane pulse with the following obfuscation:
"Now, we swing back to saying that it HAS occurred in the recent
geological past, indeed at the time which Colose says is the better
analogy."
This is incorrect. Here, I merely point to a paper in
Science by Nisbet which argues specifically that the cold Younger Dryas
was ended due to methane emissions which came mostly from wetlands, but
for which the initial trigger could have been Arctic methane clathrates:
"A possible explanation for the sudden end of
the Younger Dryas is that, at a time of high Arctic insolation, an
initial outburst of methane - perhaps from a geological source such as
methane clathrates - triggered global warming, initiating both strong
wetland emission in the tropics and north (8), and further hydrate
responses as the thermal shock penetrated the permafrost (9, 10),
freeing methane from decomposing clathrate hydrates and releasing gas
pools trapped beneath them."
The evidence for this, however, is inconclusive, so the paper concludes: "The jury thus remains out on the initial trigger..."
On
the issue of whether paleoclimate records will actually capture a
large, abrupt methane pulse such as the scenario proposed by Shakhova
et al., as this paper in Earth and Planetary Science Letters
observes, "rapid methane perturbations in the atmosphere are strongly
smoothed in ice core records" due to "the relatively short atmospheric
lifetime of methane." So it is quite possible that an abrupt,
catastrophic methane release of the sort Shakhova proposes has happened,
but is undetected in ice cores.
Tobis then declares a "scientific consensus has been reached" that Shakhova's scenario is "implausible in the extreme."
But the scientific consensus amongst ESAS experts is quite different, as I'd already noted. A peer-reviewed study by 20 Arctic specialists of ESAS data from 1995-2011, drawing of course also on Shakhova's work, specifically recognises:
"The
emission of methane in several areas of the [ESAS] is massive to the
extent that growth in the methane concentrations in the atmosphere to
values capable of causing a considerable and even catastrophic warning
on the Earth is possible."
It seems clear to me that
the scientific literature on the danger of an Arctic methane catastrophe
recognises the possibility unequivocally, but highlights huge
uncertainty in our knowledge of the processes at work. Most of the
literature I've been able to find on this subject shows great humility -
and while acknowledging the possibility of worst-case scenarios, makes
quite clear that the likelihood of those scenarios is very difficult to
gauge.
The Nature paper by Whiteman et al. went too far in stating
the Shakhova et al. scenario as "likely." But on the other end of the
spectrum, in the comments to his own blog, Tobis hints that Shakhova et
al. are involved in "junk science" - despite the fact that their papers
have been published in peer-reviewed journals (their 50 Gt scenario is
discussed in this paper originally published in the Proceedings of the Russian Academy of Sciences), and that their general thesis is taken seriously by the US National Science Foundation.
Tobis also refers to a response
to the Whiteman paper submitted to Nature (though not yet published) by
Nisbet et al., which argues that Shakhova's scenario is "improbably
large" as there is no evidence for such events during past
"glacial/postglacial transitions."
This is certainly a notable
contribution to the debate, but if past paleoclimate conditions are not a
good analogue for present Arctic conditions - a matter which remains a
matter of scientific debate - and if ice cores would not record such a
rapid scenario, then the central argument of this paper may be
questionable.
"...
the rarity of palaeoclimate evidence for hydrate-induced climate
changes argues that this is a fairly unlikely candidate for near-term
sudden climate change. Unlike the others, however, anthropogenic climate
change may alter the probability of hydrate release when compared with
the past, making the overall probability of near-term release extremely
difficult to estimate... Massive methane release by hydrates or
from peats also seems to have been extremely rare in the past, but could
become more probable in the future world under the influence of
anthropogenic forcing. However, at present, it is not possible to judge
the probability for such changes reliably."
Shindell's
argument offers a warning that lack of past evidence is not a reason
for present complacency where anthropogenic forces are changing the
climate in ways not necessarily captured by paleoclimate evidence. So
where does this leave us with regard to the risk of abrupt,
catastrophic methane releases? As far as I can discern, the literature
is largely agnostic about it, emphasises that specific scenarios are
difficult to quantify, and calls for further research. The Review of
Geophysics paper, for instance, far from asserting that a catastrophic
methane release is refuted by geophysical evidence - as Tobis says -
concludes:
"A significant increase in CH4 emissions
and atmospheric concentrations due to climate change is therefore a
possible scenario for the next century. However, uncertainties are very
large, and as discussed above, it is difficult to be very conclusive
regarding the magnitude of CH4 feedbacks and their time scales."
What
about Shakhova et al.'s specific scenario of a potential 50 Gt methane
release at any time (the basic contours of her argument are outlined here,
no paywall)? Shakhova et al. say simply that the scenario should be
taken seriously as a possibility underscoring the importance of further
ESAS research. The fact that Nature co-author Prof Peter Wadhams, who
heads up polar ocean physics at Cambridge, also takes it seriously, is
significant. Is Prof Wadhams' expertise also to be attacked? Ultimately,
in my view, Tobis fails to show either that this scenario specifically,
or abrupt methane catastrophe more generally, are unlikely.
In
particular, his claim that there is a scientific consensus demonstrating
near impossibility of a risk of a catastrophic methane event strikes me
as unsupportable. Disagreement among scientists over the Arctic methane
question is real, and it seems clear that Arctic specialists - Shakhova
included - largely agree that while catastrophe is possible, more
research is needed to discern how likely or unlikely it might be.
While
other scientists, many reputable, argue importantly that such scenarios
are beyond the pale, to my mind Tobis' egregious ad hominems against
Arctic scientists whom he disagrees with have no place in scientific
debate.
The simple purpose of my articles on the Arctic methane
question have been to investigate whether the scientific literature
bears out the possibility of a catastrophe. Apart from the fact this
issue is obviously of interest to anyone, my own particular interest in
the issue is related to how such an event would impact our societies,
economies and geopolitics.
Of course, I'm not an expert on this
issue. Anyone can see that from my bio. Should that prevent me from
trying to understand and engage with it? It's mistaken to think
that I am disrespecting the scientist bloggers who think Shakhova's
scenario specifically and an abrupt methane catastrophe scenario
generally have negligible probability. While these scientist bloggers
have articulated their views very well, the reality is that there are
lots of other scientists - their views being expressed in the literature
- who argue that we cannot rule out such scenarios, and that we cannot
even know for sure how likely or unlikely they are. Now Semiletov
and Shakova are clearly at the forefront of research on the East
Siberian Arctic Shelf (ESAS), and are the main people arguing that the
ESAS harbours a unique danger of abrupt climate change due to conditions
not found anywhere else on the planet. 20 Arctic specialists agree with
them. Perhaps they are wrong, and the scientist bloggers
critiquing them are right. But I don't know that, and looking at the
peer-reviewed literature, I cannot see any arguments which support the
idea that Shakhova is talking complete nonsense. Yes, there have been
several of blog posts by scientists and science students suggesting this
- but all the peer-reviewed analyses of the question of Arctic methane
risks by leading scientists in the field show that there is a possible
danger here which cannot be quantified. Now Tobis is openly
arguing, effectively, that Shakhova and her colleagues are non-experts,
and that they offer no evidence for their claims. So who is
disrespecting scientists, really? As a mere journo trying to get to the
bottom of this, as a mere HUMAN trying to get to the bottom of this, I'm
genuinely trying to understand how Tobis and others can insist Shakhova
et al. offer ZERO evidence at all. How can they be permitted to deliver
papers at scientific conferences, how can they be publishing in
peer-reviewed journals (and I note that their 50 Gt abrupt methane
release scenario was also peer-reviewed too) if all they are doing is
junk science? Shakhova is repeatedly arguing that significant portions
of the ESAS is underlain by methane gas hydrates which are relatively
shallow and vulnerable to destabilisation, based on direct observation
and sampling. Is she lying? Is she deluded? And are the Arctic
specialists reviewing her and others' ESAS research who think there is
something to their findings also deluded and/or liars?
I just
find this really difficult to believe. It doesn't seem credible to me
that Shakhova et al. and the Arctic scientists who support them/consider
them credible - many of them leading experts in the field too - are
just talking nonsense and junk science combined with unwarranted
speculation. If that's the case, how the hell are they getting published
in leading science journals? And why do so many Arctic specialists
agree with them? Prof Peter Wadhams from Cambridge told me that there is
a relative consensus on the possibility of danger amongst ESAS experts.
Is he just lying too? Or deluded?
If that IS happening, then
there is a fundamental problem with the scientific process here,
Shakhova et al. need to be put in their place, and we should all be
worried about how a large number of Arctic specialists can be taken in
by complete speculative nonsense.
From my perspective, I see two
sets of experts - most Arctic specialists themselves, who will not rule
out the possibility that Shakhova might be right and who respect her
work - and a lot of non-Arctic experts who, however, may well have
expertise in methane hydrates generally or climate modelling, who find
Shakhova's arguments far-fetched and evidence-thin.
It's in this
context of disagreement that I've tried to see what the peer-reviewed
literature itself says, and I've tried to let the lit speak for itself
as much as is possible here. I don't see any lit which proves any
scientific consensus demolishing Shakhova et al.
Readers are
encouraged to do their own research and make up their own minds, and yes
of course, to read up on my links (please don't tell me you like
reading blogs hoping for gospel truth - the links are there to be read
and checked as supporting evidence!) and if you disagree with my
conclusions, the key thing that would help me is to see how and why
Shakhova et. al are not actually providing compelling evidence for their
arguments.
I won't be able to respond further for a while as I'm away, but will read constructive comments with interest.
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