Arguments
Toward Improved Discussions of Methane & Climate
Posted on 1 August 2013 by Chris Colose
Update- See Correction of an error at bottom
Here at Skeptical Science, there is an ongoing effort to combat disinformation from those who maintain that climate change is a non-issue or non-reality. From time to time, however, individuals or groups overhype the impacts of climate change beyond the realm of plausibility. Some of this is well-intentioned but misguided. For those who advocate climate literacy or for scientists who engage with the public, it is necessary to call out this stuff in the same manner as one would call out a scientist who doesn’t think that the modern CO2 rise is due to human activities.
Many overblown scenarios or catastrophes seem to involve methane in the Arctic in some way. There are even groups out there declaring a planet-wide emergency because of catastrophic, runaway feedbacks, involving the interplay between high latitude methane sources and sea ice.
About a week ago, a Nature article by Gail Whiteman, Chris Hope, and Peter Wadhams came out analyzing the "Vast Costs of Arctic Change." The Whiteman article is an honest and thoughtful commentary about the economic impacts of a changing Arctic climate. I will not comment on their economic modeling here, but rather on a key scenario assumption that they use which calls for vast increases in Arctic-sourced methane to the atmosphere. In this case, they have in mind a very rapid pulse of 50 Gigatons of methane emanating from the East Siberian Shelf (see image, including Laptev and East Siberian sea). Note: 1 GtCH4= 1 Gigaton of methane = 1 billion tons of methane. Whiteman et al. essentially assume that this "extra methane" will be put in the atmosphere on timescales of years or a couple decades. This article has been widely publicized because it calls for an average of 60 trillion dollars on top of all other climate change costs. Since this was discussed in a prediction context rather than as a thought experiment, it demands analysis of evidence.
In this article, I will argue that there is no compelling evidence for any looming methane spike. Other scientists have spoken out against this scenario as well, and I will encompass some of their arguments into this piece. In summary, the reason a huge feedback is unlikely is because of the long timescale required for global warming to reach some of the largest methane hydrate reservoirs (defined later), and because no evidence exists for such an extreme methane concentration sensitivity to climate in the past record. Permafrost feedbacks are of concern, but there is no basis for assuming a dramatic "tipping point" in the atmospheric methane concentration.
The Methane Tour
Methane (CH4) is a greenhouse gas. It absorbs thermal energy that the Earth is trying to shed into outer space, and can thus warm the surface of the planet. Its concentration in the modern atmosphere is a little bit shy of 2 parts per million by volume (ppm), compared to roughly 0.72 ppm in 1750 or 0.38 ppm in typical glacial conditions. Like CO2, methane has not risen to modern day concentrations during the entirety of the now ~800,000 year long ice core record.
So what about Whiteman's scenario?
For perspective on how big 50 GtCH4 is, I've used data from David Archer's online methane model to see how atmospheric methane concentrations would change in response to such a big carbon injection. You can do this as a back-of-envelope calculation by noting that 1 ppm is about 2.8 GtCH4 if it all stays as methane and isn't removed, but this model lets you see the decay timescale too. For methane, the decay back to original concentrations occurs within decades, whereas for CO2 it takes millennia (CH4 is rapidly oxidized by the hydroxyl radical in the atmosphere). Therefore, CO2 dominates the long-term climate change picture but the methane spike can induce very large transitory effects.
I've run two scenarios in which the 50 GtCH4 injection takes 1 year and 10 years to complete (red and blue lines, respectively). The model starts with pre-industrial CH4 concentrations in years -10 through zero. The modern concentration of methane is shown as a horizontal orange line.
Everything having to do methane in the ice core record resides below the orange line in Figure 1 (at least within the resolution of the cores). So we're potentially talking about a very big change, which the Whiteman article contends is likely to be emitted fairly soon and should have implications for Arctic policy.
For many, the primary concern about “big” abrupt changes in atmospheric CH4 stems from the large quantity of CH4 stored as methane hydrate or in permafrost in the Arctic region. These terms are defined below. It should be noted that globally, wetlands are the largest single methane source to the modern atmosphere. Most of that contribution is from the tropics and not from high latitudes (even if the Arctic was to start pumping harder). The Denman et al., 2007 carbon cycle chapter in the last IPCC report is a useful reference.
Nonetheless, the Arctic is a region that is quite dynamic and is changing rapidly. The high latitudes are currently a CO2 sink and CH4 source in the modern atmosphere, and it’s not implausible that the effectiveness of the sink could diminish (or reverse) or that the methane source could enhance in the future, since we expect a transition to a warmer, wetter climate with an extended thawing season. This makes the carbon budget in the Arctic a “hot” place for research.
In these discussions, it is important to clarify what sort of methane source we're talking about.
Methane hydrate is a solid substance that forms at low temperatures / high pressures in the presence of sufficient methane. It is an ice-like substance of frozen carbon, occurring in deep permafrost soils, marine continental margins, and also in deeper ocean bottom sediments. It's also very concentrated (a cubic foot of methane hydrate contains well over 100 times the same volume of methane gas).
On the decade-to-century timescale, the liberation of methane from the marine hydrate reservoir (or the deep hydrates on land) should be well insulated from anthropogenic climate change. Deep ocean responses by methane are a very slow response (many centuries to millennia, Archer et al., 2009). Methane released in deep water also needs to evacuate the water column and get to the atmosphere in order to have a climate impact, although much of it should get eaten up by micro-organisms before it gets the chance. These issues are discussed in a review paper by O’Connor et al., 2010.
There’s also carbon in near-surface permafrost, which is the more vulnerable carbon pool during this century. Permafrost is frozen soil (perennial sub-0°C ground), and can also encompass the sub-sea permafrost on the shelves of the Arctic Ocean. This includes the eastern Siberian shelf, a very shallow shelf region (only ~10-20 m deep, and very broad, extending a distance of 400– 800 km from the shoreline). This is a bit of a special case. These subsea deposits formed during glacial times, when sea levels were lower and the modern-day seafloor was instead exposed to the cold atmosphere. The ground then became submerged as sea levels rose (going into the warmer Holocene). The rising seas have been warming the deposits for thousands of years. Because of their exposure during the Last Glacial Maximum, the shelves may be almost entirely underlain by permafrost from the coastline all the way down to a water depth of tens or even a hundred meters (e.g., Rachold et al., 2007 and this USGS page).
There's actually no good evidence of shallow hydrate on the Siberian shelves, even though there are substantial quantities of subsea permafrost. Hydrate may exist deeper down however, more than 50 meters below the seafloor. The stability of these hydrates is sustained by the existence of permafrost, and it's not quite clear to what extent hydrate can also be stored within the permafrost layer.
The estimates of the amount of methane in these various Arctic reservoirs are very uncertain. Ballpark numbers are a couple thousand gigatons of carbon (GtC) stored in hydrates in global marine sediments (e.g., Archer et al., 2009) of which a couple hundred gigatons of carbon are in the Arctic Ocean basin, and between 1000-2000 GtC in permafrost soil carbon stocks (e.g., Tarnocai et al., 2009) after you include the deeper deposits. For comparison, there is a bit over 800 GtC in the atmosphere, of which about 5 Gt is in the form of methane, and estimated ~5000 GtC in the remaining fossil fuel reserve. These numbers seem big compared to the atmosphere, but for methane direct comparison isn't too relevant unless you put it in rapidly, since it has such a short lifetime in the atmosphere. Large amounts of CO2, in contrast, last much longer.
A couple years ago, Shakhova et al. (2010a) reported extensive methane venting in the eastern Siberian shelf and suggested that the subsea permafrost could become unstable in a future warmer Arctic. Shakhova et al (2010b) cite ~1400 Gt in the East Siberian Arctic Shelf, which comprises ~25% of the Arctic continental shelf and most of the subsea permafrost. Shakhova et al (2010c) ran through a few different pathways in which they argued for 50 GtCH4 release to the atmosphere either in a 1-5 year belch or over a 50-yr smooth emission growth, which they suggest, “significantly increases the probability of a climate catastrophe.” This assessment was the foundation for the concern in the recent Whiteman Nature article, linked at the top.
The physical mechanism outlined by some of these authors is related to the rapid reduction in Arctic summer sea ice observed over the last few decades, which allows for greater amounts of solar radiation to penetrate the waters around the Arctic shelf. Warming water propagates down in the well-mixed layers tens of meters to the seabed, and might melt frozen sediments underneath. Because the shelf in this region is shallow (compared to other regions), one doesn't need to wait a long time for the seafloor to feel the atmosphere-surface forcing, and methane leakage might have an easier escape path to the atmosphere. Allegedly, this has been leading to an acceleration of methane flux.
Responses from Scientists
As a response to the first paper from Shakhova on enhanced methane fluxes, Petrenko et al (2010) criticized the authors for misunderstanding several of their references and primarily for the logical implications of their conclusions. For example,
“A newly discovered CH4 source is not necessarily a changing source, much less a source that is changing in response to Arctic warming. Shakhova et al. do acknowledge these distinctions, but in these times of enhanced scrutiny of climate change science, it is important to communicate all evidence to the scientific community and the public clearly and accurately”
Another paper, Dmitrenko et al (2011) reinforced this statement and came to the conclusion that there is currently no evidence that Arctic shelf hydrate emissions have increased due to global warming. This is also discussed in the review article by O'Connor et al (2010, linked above).
The work done by the Dmitrenko paper shows that although the changing Arctic atmosphere has led to warmer temperatures throughout the water column (over the eastern Siberian shelf coastal zone), it takes a very long time for the permafrost feedback at the bed to respond to this signal. They noted that the deepening of the permafrost table should only have been on the order of 1 meter over the last several decades, which does not permit a rapid destabilization of methane hydrate.
It is important to emphasize that simple point source emission estimates are not often suitable for determining changed sources and sinks over the last few decades, and thus don't tell you how that translates into atmospheric concentration. This should be kept in mind when seeing dramatic videos of methane venting from a shelf or exploding lake, which might not actually have much to do with global warming.
In 2008, there was a comprehensive report on Abrupt Climate Change from the U.S. Climate Change Science Program, which is a bit dated but nonetheless makes a statement reflecting most of current scientific thinking. Quoting Ch. 5 Brook et al (2008):
"Destabilization of hydrates in permafrost by global warming is unlikely over the next few centuries (Harvey and Huang, 1995). No mechanisms have been proposed for the abrupt release of significant quantities of methane from terrestrial hydrates (Archer, 2007). Slow and perhaps sustained release from permafrost regions may occur over decades to centuries from mining extraction of methane from terrestrial hydrates in the Arctic (Boswell, 2007), over decades to centuries from continued erosion of coastal permafrost in Eurasia (Shakova [sic] et al., 2005), and over centuries to millennia from the propagation of any warming 100 to 1,000 meters down into permafrost hydrates (Harvey and Huang, 1995)"
Paleo-Analogs
One of the primary reasons we don't think there's as much methane sensitivity to warming as has been proposed by Shakhova, and argued for in the Whiteman Nature article, is because there's no evidence for it in the paleoclimate record. This has been a point made by Gavin Schmidt on Twitter (a compilation of his many tweets on the topic here) but the objections to the Nature assumptions have been further echoed in recent days by other scientists working on the Arctic methane issue (e.g., here, here).
One can argue from a process-based and observations-based approach that we don't understand everything about Arctic methane feedback dynamics, which is fair. Nonetheless, the methane changes on the scale being argued by Whiteman et al. should have been seen in the early Holocene (when Summer Northern Hemispheric solar radiation was about 40 W/m2 higher than today at 60 degrees North, 7000-9000 years ago). Even larger anomalies occurred during the Last Interglacial period between 130,000 to 120,000 years ago, though with complicated regional evolution (Bakker et al., 2013).
Both of these times were marked by warmer Arctic regions in summer without a methane spike. It's also known pretty well (see here) that summertime Arctic sea ice was probably reduced in extent or seasonally free compared to the modern during the early Holocene, offering a suitable test case for the hypothesis of rapid, looming methane release.
It should be noted that Peter Wadhams did offer a response recently to the criticisms of the Whitehead Nature piece (Wadham is a co-author) but did not address why this idea has not been borne out paleoclimatically.
Yesterday, an objection to the paleoclimate comparison cropped up in the Guardian suggesting that the early Holocene or Last Interglacial analogs are not suitable pieces of evidence against rapid methane release. They aren't perfect analogs, but the argument does not seem compelling. The Northeast Siberian shelf regions have been exposed many times to the atmosphere during the Pleistocene when sea levels were lower (and not covered by an ice sheet since at least the Late Saalian, before 130,000 years ago, e.g., here). As mentioned before, when areas such as the Laptev shelf and adjacent lowlands were exposed, ice-rich permafrost sediments were deposited. The deposits become degraded after they are submerged (when sea levels increase again), resulting in local flooding and seabed temperature changes an order of magnitude greater than what is currently happening. Moreover, the permafrost responses have a lag time and are still responding to early Holocene forcing (some overviews in e.g., Romanovskii and Hubberten, 2001; Romanovskii et al., 2004; Nicolsky et al., 2012). A book chapter by Overduin et al., 2007 overviews the history of this region since the Last Glacial Maximum. These texts also suggest that large amounts of submarine permafrost may have existed going back at least 400,000 years. It therefore does not seem likely that the seafloor deposits will be exposed to anything in the coming decades that they haven't seen before.
What about other times in the past? Fairly fast methane changes did occur during the abrupt climate change events embedded within the last deglaciation (e.g., Younger Dryas), just before the Holocene when the climate was still fluctuating around a state colder than today. These CH4 changes were slower than the abrupt climate changes themselves, and have been largely attributed to tropical and boreal wetland responses rather than high latitude hydrate anomalies. Marine hydrate destabilization as a major driver of glacial-interglacial CH4 variations has also been ruled out through the inter-hemispheric gradient in methane and hydrogen isotopes (e.g., Sowers, 2006)
To be fair, we don't have good atmospheric methane estimates during warmer climates that prevailed beyond the ice core record, going back tens of millions of years. Methane is brought up a lot in the context of the Paleocene-Eocene Thermal Maximum (PETM, 55 million years ago). During this time, proxy records show global warming at the PETM (similar to what modern models would give for a quadrupling of CO2), extending to the deep ocean and lasting for thousands of years. In addition, there were substantial amounts of carbon released. It may very well be that isotopically light carbon came from a release of some 3,000 GtC of land-based organic carbon, rather than a destabilization of methane hydrates, although this is a topic of debate and ongoing research (see e.g., Zeebe et al., 2009; Dickens et al., 2011).
It's also important to emphasize that any destabilization of oceanic methane hydrates at the PETM, or any other time period, would imply that the carbon release is a feedback to some ocean warming that occurred first- perhaps on the order of 1000 years beforehand. Furthermore, once methane was in the atmosphere, it would oxidize to CO2 on timescales significantly shorter than the PETM itself (decades.) Unfortunately, there is no bullet-proof answer right now for what caused the PETM, but rather several hypotheses that are consistent with proxy interpretation. However, methane cannot be the only story.
The Role of Methane in Climate (Change)
To be clear, CH4 is important as we go forward, and is already a key climate forcing agent behind CO2 (coming in at ~0.5 W/m2 radiative forcing since pre-industrial times). Additionally, methane is quite reactive in the atmosphere, and the effect of other things like tropospheric ozone, aerosols, or stratospheric water vapor are partly slaved to whatever is happening to methane (Shindell et al., 2009). This means methane emitted has a bigger collective impact on climate than if you just do the radiative forcing calculation by comparing methane concentration changes to what it was in 1750.
Permafrost thawing is also going to be important in the coming century (this is a good paper), and the uncertainties pretty much go one way on this. There's not much wiggle room to argue that permafrost will reduce CH4/CO2 concentrations in the future. This is also likely to be a sustained release rather than one big catastrophic event. For example, permafrost was not included in Lenton (2008) as a "tipping point" for precisely the reason that there's no evidence for any "switch" of rapid behavior change. Much of the carbon is also likely to be in the form of CO2 to the atmosphere, and even implausible thought experiments of catastrophic methane release (see David Archer's post at RealClimate) give you comparable results in the short-term as to what CO2 is going to do for a long time.
Conclusion
The observed methane venting from the East Siberian shelf sea-floor to the atmosphere is probably not a new component of the Arctic methane budget. Furthermore, warming of the Arctic waters and sea ice decline will likely impact subsea permafrost on longer timescales, rather than the short term.
Methane feedbacks in the Arctic are going to be important for future climate change, just like the direct emissions from humans. This includes substantial regions of shallow permafrost in the Arctic, which is already going appreciable change. Much larger changes involving hydrate may be important longer-term. Nonetheless, these feedbacks need to be kept in context and should be thought of as one of the many other carbon cycle feedbacks, and dynamic responses, that supplement the increasing anthropogenic CO2 burden to the atmosphere. There is no evidence that methane will run out of control and initiate any sudden, catastrophic effects. There's certainly no runaway greenhouse. Instead, chronic methane releases will supplement the primary role of CO2. Eventually some of this methane oxidizes into CO2, so if the injection is large enough, it can add extra CO2 forcing onto the very long term evolution of global climate, over hundreds to thousands of years.
Errata Update: Gavin Schmidt let me know that in the first version of this post, I used gigatons of carbon instead of gigatons of methane. I mistakingly read the Shakhova paper as an injection of carbon. Since the molecular weight of carbon is 12 g/mol, and CH4 is 16 g/mol, then 1 GtC=1.33 GtCH4. The figure in the post has been revised accordingly and doesn't impact the argument here.
Correction for spelling- That's the sea of Okhotsk, in the last paragraph.
One of their papers shows a severe anoxic region in the northern Pacific, extending down the Alaskan and Canadian west coast.
I live in California, near the ocean.
Are my wife and I going to have to worry about clouds of toxic hydrogen sulfide gas drifting in from the Pacific, if this anoxic region extends as far south as northern California?
Apparently, according to the IMPACTS group modeling, the sea of Okhotsk may be very important to the U.S. Their modeling shows a severe anoxic region in the northern Pacific, originating in the sea of Okhotsk, after 30 years of methane hydrate release, according to their conservative modeling. The figures in their Powerpoint slide show illustrate this anoxic region extending across to Alaska, down the west coast of Canada, and all the way down the California coast to around Baja California, wandering out into the Pacific near the equator, then continuing in diluted form along the west coast of South America.
Will there be hydrogen sulfide clouds rolling in from the Pacific into northern California within my lifetime?
A lot of that probably depends on the global methane hydrate inventory, and whether hydrate dissociation will be a top down, orderly process.
Is the real global hydrate inventory 80,000 (or more) cubic kilometers of hydrate or around 4000 cubic kilometers?
Whatever the methane hydrate inventory is, Dickens says that under projected warming conditions, the methane hydrate stability zone will shrink by about 50 percent. So, whatever is down there, maybe half of it is likely coming out, over the next decades or centuries.
Does the IMPACTS modeling take into account gas driven pumping of sea water through the hydrate deposits, for example? Wouldn't gas release into methane chimneys make the seawater in that chimney less dense, pumping upward flow? Would warm water flow down an adjacent channel, to fill that chimney? Could a sort of chaotic or oscillating flow driven by gas pumping and alternating chilling of water in adjacent channels result?
How sure are we that gas pumping will not lead to pumping of sea water through the hydrate deposits, when gas releases by the hydrate deposits increase by tens or hundreds of times?
Here's a paper that talks about very slow flow, driven by gas pumping, tidal pumping and various other forces through a normal hydrate deposit, not yet much affected by global warming:
Fluid and chemical £ux in and out of sediments hosting methane hydrate deposits on Hydrate Ridge, OR, II:Hydrological processes
How much will gas driven pumping increase when methane gas emission from shallow hydrate deposits increases by tens or hundreds of times?
All of this would seem to make the slab models used by the IMPACTS team at least questionable, and possibly actively misleading.
If scientific conservatism is helping to kill the biosphere, maybe it's time to try something else.
There is a rebuttal of the Whiteman et al paper by Nisbet et al here:
Response of methane sources to rapid Arctic warming.
Michael Tobis rebuts Nafeez Ahmed:
Climatifact: Seven Points in Support of Shakhova? Or not?
Methane is 23 times stronger as a greenhouse gas than Carbon Dioxide in the short run and 72 times stronger in the long run. I have noted variations of that statement hundreds of times by credible scientific sources. This article seems to state something on the order of the opposite?
For brevity, singling out just one other minor point the article makes on methane, where hydroxyl radicals counter CH4...
First on the highly ephemeral hydroxyl molecules: they are produced when ultraviolet radiation bombards common gases such as ozone and water vapor. The resultant OH molecules typically have a lifetime of less than one second because they immediately react with various gases (not just methane).
Secondly, the shrinking ozone hole contributes to producing extra hydroxyl radicals. As the ozone hole recedes -- and an ever thicker greenhouse shield blocks more ultraviolet radiation -- so to does the production of hydroxyl molecules recede.
Thirdly, as pollution, smog, and brown haze increase, a feedback threshold may eventually be crossed such that the hydroxyl oxidation process goes into sharp decline, ceasing to be a significant offsetting factor.
I could go on and on, as their are other sources of the methane bomb unmentioned in the article, but this is just a "comment" and my brief point has been made.
So, in abbreviated conclusion, I am perplexed... Is it even remotely possible the author is downplaying the methane gorilla in the greenhouse for some reason?
[DB] "Is it even remotely possible the author is downplaying the methane gorilla in the greenhouse for some reason?"
Speculation to motive contravenes the Comments Policy in this venue. Please focus on the evidence.
Substantiating my earlier contention that methane should not be summarily dismissed...
Methane is 20 times more potent as a greenhouse gas than carbon dioxide. This recent lecture by James Hansen of NASA notes methane regulation has more short-term potential to slow climate change than does carbon regulation.http://www.columbia.edu/~jeh1/2009/Copenhagen_20090311.pdf
Given that methane is about 25 times stronger as a greenhouse gas per metric ton of emissions than carbon dioxide...
http://www.nasa.gov/home/hqnews/2008/oct/HQ_08-276_Methane_levels.html
Methane, with a warming potential 72 times that of carbon dioxide over a 20 year time frame, having a half-life of only 7 years.
http://www.dailykos.com/story/2013/06/19/1217235/-MIT-Climate-Fast-Solution-to-Climate-Change-Is-On-Your-Plate#
Pound for pound, the comparative impact of CH4 on climate change is over 20 times greater than CO2 over a 100-year period.
http://www.epa.gov/climatechange/ghgemissions/gases/ch4.html
Over 100 years, a ton of methane would heat the globe 23 times more than a ton of carbon dioxide.
http://oceana.org/en/our-work/climate-energy/climate-change/learn-act/greenhouse-gases
Methanes Lifetime Global warming potential over CO2
20-yr 12 times 100-yr 72 times 500-yr 7.6 times
https://en.wikipedia.org/wiki/Greenhouse_gas#Greenhouse_gases
My personal thoughts on this article. Okay, I realize we all go off on excessive tangents on occasion, myself included, and maybe my retort is yet another example of that, but...
But this article begs that I protest. Because the world is in great peril from global warming. From the feedback loops of global warming. From the ireversible tipping point thresholds of the feedback loops of global warming. From the abrupt "climate change" [sic] that will result...
Yes, many of the feedback loops are methane related, but there are many more KNOWN major feedback loops which this article ignores. Add to the known feedback loops the new UNKNOWN feedback loops, which are constantly being discovered...
The planet is in exponentially imminent danger of a failing to support its increasingly overpopulated hoards.
Dirty energy and its charlatan shills are much too effectively dumbing down voters to continue having their dirty way with destroying the planet.
So, someone overstates -- debatably, somewhat -- that the planet is collapsing. So what? Why go to such extensive extremes to refute it? Seems voters need some counter-bullshitorama to push them into voting out climate deniers rather than downplaying and lowballing the reality of what we are truly faced with.
This article brings new meaning to "wrong headed", if not, as previously noted, just plain wrong in at least a couple of aspects, but frankly, many more that I did not (yet?) take the time to expose...
IBM in the 60's used to have the simple motto of "Think". Consider that in your future endeavors to protect the human habitat from those mindless morons that destroy it in the name of greed. Voters need to wake up, not be lulled into complacency by articles like this. Shame on you...
Northbeacher, rather than continuing on in your variant of your arguments from personal incredulity, note that the OP is written by a climate scientist and repeatedly references the primary literature, so asserting your own personal opinions to the contrary carry little weight here.
Given the vast differences in amounts being injected back into the carbon cycle, CO2 has a much greater Radiative Forcing than does methane. And that's the most important consideration, not the Global Warming Potential of the various gases.
FYI, for the Arctic, the OH radical found there is primarily produced in the tropics and then transported poleward (source).
[Source]
It appears that some methane hydrate deposits are associated with high salt brine deposits- and those hydrates may be much, much less stable than the majority of hydrate deposits.
When methane hydrate crystals form, these crystals exclude salt and other impurities from their crystal structure, in the well known "purification by crystalization" process.
This apparently leads to high salt concentrations in some deposits, which allows those deposits to be at the triple point of the system- in which liquid, methane gas, and solid hydrate co-exist.
For these deposits, methane gas is much more mobile, and can apparently migrate upward through the hydrate deposit as a gas, according to authors including Peter Flemmings and his student Xiaoli Liu :
DYNAMICS OF SHALLOW MARINE GAS HYDRATE AND FREE GAS SYSTEMS
Such high salt methane deposits may be fairly common, according to authors including Maria Torres and Miriam Kastner:
OCCURRENCE OF HIGH SALINITY FLUIDS ASSOCIATED WITH MASSIVE NEAR-SEAFLOOR GAS HYDRATE DEPOSITS
The existence of these deposits may be the answer to the disconnect between the geological evidence of past methane catastrophes and our current lack of understanding of how these mass extinction events occurred.
These high salt deposits could provide a bridge between orbital or anthropogenic forcing and massive methane release from the oceanic methane hydrates. Along with permafrost decay and shallow permafrost bound hydrates, these high salt hydrates could be the answer to how massive methane releases could occasionally be triggered by relatively minor triggering events.
Global methane hydrate inventories are probably very high, due to a series of recent ice ages. We are providing an exceptionally rapid and systematic triggering event by our global greenhouse emissions. The situation seems ideal, to me, for the generation of a methane catastrophe- perhaps the biggest one ever.
Why hasn't a biosphere ending methane catastrophe occurred before? The End Permian was a close call, perhaps, with upwards of 90 percent of species exterminated. And the sun is hotter now, by a couple of percent, than it was during the End Permian.
Maybe a biosphere ending runaway greenhouse hasn't happened before, just by luck.
If a low level or greater runaway had happened before, we would not be around to discuss it.
This is the last thing Shakhova says in the video:
"strictly speaking, we do not like what we see there. Absolutely do not like."
==============
This thread should be at least a partial relief to her, as it is to me, since it was obvious that she was deeply and personally concerned about the issue. Besides, she's really pretty.
So at least we have a possibility of having a Planet for more than another 25 years or so.
Whew!
Hi davidnewell-
The siren song of reassurance is tempting, I'll admit.
But we need to remember that the total cumulative greenhouse heating from buring a ton of fossil fuel is on the order of 100,000 times the useful heat of combustion, according to numerous modelers including Ken Caldeira of Stanford.
If we destabililize the methane hydrates, the cumulative greenhouse heating from buring a ton of fossil fuel could be millions of times the useful heat of combustion. So the greenhouse side effects of fossil fuel use are much, much greater than the benefit.
This is not a sustainable system, when we are talking about burning trillions of tons of methane from the hydrates, or worse yet, releasing it without buring it.
Arguments that we know precisely how fast the methane hydrates will destabilize, and therefore we should bet the future of the planet on our present incomplete state of knowledge are very, very weak arguments, in my opinion.
According to numerous sources including the Union of Concerned Scientists, the fossil fuel industry is waging a war of disinformation about this subject, as well. One of the key goals of that disinformation campaign is to inject confusion into the debate.
In such an environment, with tens of trillions of dollars at stake, we should not be tempted by arguments that tell us what we really want to hear, I think.
We all really want to hear that things will be all right, I think.
But the carbon isotope signatures of multiple past apparent methane catastrophes cannot be prudently ignored, in my opinion. We may not know precisely how past methane catastrophes occurred.
But, the simplest explanation, the best theory, is that past methane catastrophes did in fact occur. The methane gun hypothesis is in fact the only consistent hypothesis put forth to this date to explain a whole series of mass extinction events, I think.
These carbon isotope excursions correspond very well with the injection of several trillion tons of methane into the atmosphere from the methane hydrates- not just once, but several times in sufficient quantity to cause mass extinction events.
The carbon isotope excursions associated with past mass extinction events are hard scientific evidence, which cannot be safely ignored, in my opinion.
@Andy Skuce #54:
Nafeez Ahmed reponds to Michael Tobis in a lengthy article, Why the jury's still out on the risk of Arctic methane catastrophe, posted Sep 5 on his Guardian blog, Earth Insight.
Here's the lead paragraph of Ahmed's post.
The following figure is from Benton and Twichett's paper:
How to kill (almost) all life: the end-Permian extinction event
Notice the carbon isotope excursions illustrated at the left side of the figure- parallel carbon isotope excursions from both carbonate and organic carbon sources. Notice the extinction of numerous fossil species on the right- in fact roughly 60% of all families and 80% of all genera became extinct, during the End Permian. The timescale of the extinction, according to other sources, was about 80 thousand years- but the initial apparent release was much quicker- less than two thousand years, according to many sources.
As the authors point out:
There are other carbon isotope excursions associated with mass extinction events, including the End Triassic, a couple of oceanic anoxic events in the Jurassic, and the Paleocene-Eocene Thermal Maximum. All of these correspond very well to the injection of several trillion tons of methane from the oceanic hydrates into the atmosphere. There are very large numbers of sudden isotope excursions, of course, corresponding to smaller methane releases, and smaller hyperthermal events- some of which appear to be timed to orbital cycles, and so to orbitally driven global warming.
This is hard scientific isotope evidence, coming from the rocks of many, many sites around the world, duplicated numerous times by numerous scientists.
This carbon isotope evidence of past apparent methane catastrophes cannot safely be ignored, in my opinion.
Here's another apparent mass methane injection event- the End Triassic. The authors of this paper claim that this event is best explained by the injection of 12 trillion tons of carbon (16 trillion tons of methane) into the atmosphere by a release of methane from the oceanic methane hydrates:
Atmospheric Carbon Injection Linked to End-Triassic Mass Extinction
Notice again the large carbon isotope excursion on the left, and the disappearance or loss of diversity of fossil groups on the right.
The authors conclude:
Notice that the apparent amount of carbon injected, 12 trillion tons, is right in line with Dickens' estimate of worldwide methane hydrate inventory of 5 to 20 trillion tons of carbon- it makes Dicken's group estimates seem a little low, in fact.
Notice that the amount of carbon injected is several times that of Archer's estimate of roughly 0.7-1.2 trillion tons of carbon in the modern methane hydrates. So, Archer's estimates seem low, as do those of Milkov. By the way, Milkov worked for British Petroleum at the time he made his estimates - his original scientific paper acknowledges this.
But the End Triassic did not totally deplete the methane hydrates, very likely. Some modern hydrate deposits are very deep, and are not in high salt sediments. So, to me, this suggests that Klauda and Sandler's estimates of 74.4 trillion tons of carbon are likely closer to correct. Our recent series of ice ages have lowered ocean temperatures and expanded the methane hydrate stability zone.
From Gerald Dickens:
Down the Rabbit Hole: toward appropriate discussion of methane release from gas hydrate systems during the Paleocene-Eocene thermal maximum and other past hyperthermal events
We don't know how much methane is in the hydrates. The higher estimates are favored, in my opinion.
We don't know how rapidly methane will be released from the hydrates. But methane hydrates are a form of water ice- and ice melts when heated.
We know that some high salt deposits probably capable of releasing methane rapidly in response to temperature changes exist.
We know that a series of mass extinction events appear to be tied to massive methane releases, according to the carbon isotope ratio excursions.
We know that fossil fuel use generates greenhouse side effects that generate on the order of 100,000 times as much greenhouse heating as is received in useful heat of combustion.
These carbon isotope ratio excursions associated with several past mass extinctions are hard scientific evidence of past probable methane catastrophes, and cannot be safely ignored, in my opinion.
Here's another carbon isotope excursion, corresponding to the release of several trillion tons of carbon from the methane hydrates, from still another mass extinction hyperthermal event- the Paleocene Eocene Thermal Maximum (PETM):
Warming the fuel for the fire: Evidence for the thermal dissociation of methane hydrate during the Paleocene-Eocene thermal maximum
This one charts the C13/C12 isotope ratios in individual foraminifera, across the PETM event, and simultaneously charts the O18/O16 ratios, reflecting changes in ocean temperature.
The authors say the event was "geologically instantaneous". Other high resolution geological strata from Chinese formations calculate the duration of this first large probable methane release at less than 200 years.
Geologically instantaneous and "less than 200 years" set an upper bound for the duration of the event, but no lower bound. From this evidence, it is impossible to set a lower bound for the duration of the event. From this evidence, the event could have taken place in one year, or 200- nobody knows.
These are similar carbon isotope signatures of probable methane releases, from several large mass extinction events. The End Permian was about 250 million years ago. The End Triassic was about 200 million years ago. The PETM was about 50 million years ago. Each one corresponds to the release of several trillion tons of carbon from the hydrates.
The hard scientific evidence of past carbon isotope excursions and associated mass extinctions cannot be safely ignored.
Two other probable massive methane releases from the oceanic methane hydrates- the Toarcian and Aptian oceanic anoxic events, of 180 and 120 million years ago:
ON THE NATURE OF METHANE GAS-HYDRATE DISSOCIATION DURING THE TOARCIAN AND APTIAN OCEANIC ANOXIC EVENTS
Massive methane release can casuse both ocean acidification and oceanic anoxia, according to numerous authors.
This hard scientific isotope ratio evidence of past probable methane releases from the hydrates cannot be safely ignored.
Sorry, I see that saileshrao has posted a link to the Beckwith reponse, but I didn't see a response here.
This has got to be the most confusing article I (a layperson) have ever read on SkepticalScience.
Having carefully read Chris Colose's critique of Natures article "Vast Costs of Arctic Change", and the many informative comments that follow, it appears that there are many countering views.
Can the interpretation of such a wealth of data be so indecisive on the likelihood of catastrophic methane emmision from the Arctis's thawing permafrost and warming oceans?
I have followed the excellent articles presented on Arctic News for some time, and have always found their graphics and data to be most informative, objective and (apparently?) of the highest quality.
Paul Beckwith has responded to SkepticalScience (dated 9 Aug 2013) here, in which he appears to raise many valid points of dispute.
He opens with this para:
Paul Beckwith: The above two paragraphs set the tone of this discourse. AMEG (Arctic Methane Emergency Group) is unjustly framed in this introduction as a fringe group using such terms as “overhype”, “beyond realm of plausibility”, “overblown scenarios or catastrophes”, “planet-wide emergency”. This is the complete opposite of the truth...
Could SkepticalScience revisit this ussue please, to clarify what appears to me to be many valid points of interpretive disagreement.
Sorry to go back to such an old issue, but it the seriousness of methane forcing still conduses me a bit.
Both of the CH modes of methane (T2 and E) in the spectral region of Earth's emission are completely overwhelmed by the HOH bending mode of water. This seems to imply that the only region of the atmosphere where methane could have a distinct effect would be at the top of the troposphere and the in stratosphere where water concentrations drop to a few ppm.
Do models bear out that concentrations of methane well above the current 1.8 ppm (1) could have a large warming effect and that (2) this effect would overwhelmingly take place in the upper troposphere and stratosphere?
I do hope that Skeptical Science will revisit this issue. Flood basalt erruptions and release of methane from the methane hydrates seems to be intimately connected, according to the carbon isotope excursions that coincide with a long list of extinction events. This list of flood basalt erruptions, many with coincident carbon isotope excursions corresponding to trillions of tons of methane hydrate dissociation, is from the authors' reply to a more recent article Rapid climate change more deadly in Earth's past than asteroid impacts, study shows. Note that ma= millions of years ago.
User Doug_C asks:
Please read the OP of this post and the comments above this one in full. Here's some updated material:
Gao et al 2013 - Permafrost degradation and methane: low risk of biogeochemical climate-warming feedback
And, as the Gao et al paper I linked to notes, CH4 from permafrost will drive an expected temperature increase by 2100 of about 0.1 C. Schaefer et al 2014 now calculates a total temperature rise contribution from ALL permafrost carbon stocks (CO2 AND CH4) by 2100 of about 0.29 ± 0.21 (0.08-0.5 C).
Per Berndt et al 2014 - Temporal Constraints on Hydrate-Controlled Methane Seepage off Svalbard
Per Schuur et al 2015, an abrupt permafrost climate feedback is unlikely, according to the experts, but the bad news is that the already difficult task of keeping warming under 2°C becomes much harder once we face up to the consequences of Arctic permafrost feedbacks.
SkS Post on Schuur
This just in, per Myhre et al 2016: METHANE NOT ESCAPING INTO THE ATMOSPHERE FROM ARCTIC OCEAN
Shocker.
And there ensued much gnashing of teeth and hissing in frustration from AMEG, Arctic-News (dot) blogspot, the Scribbler-of-fiction, Paul Beckwith and Guy McPherson.
Per Sweeney et al 2016:
And
Also on that paper
And even more on it
Per James et al 2016 - Effects of climate change on methane emissions from seafloor sediments in the Arctic Ocean_A review
And
And
Per Ruppel and Kessler 2017:
And
More on that paper, here.
Daniel Bailey
Thanks for responding.
I wasn't really thinking in terms of a massive pulse of Arctic methane from destalization in the next few years or decades. I was thinking in terms of the next century or longer and how records from past rapid warming events as a result of quickly increasing atmospheric CO2 levels indicate there were pulses of methane that kicked warming from CO2 into a much more powerful forcing.
In recent geological time the conditions have favoured the creation of more methane hydrates as the planet has in general been cooler with ice ages and the gradual drawdown of CO2 levels. This would seem to pose an even greater possibility of methane release on shorter time scales than earlier events when the base "stable" state was from a much warmer planet with little or no permanent ice cover.
I also seriously question trying to project anything this complex and poorly understood decades into the future. As we saw with something that should have been relatively simple to project in the Larsen B iceshelf breakdown, dynamic forces quickly turned a massive sheet of very thick ice into a highly unstable formation that broke apart.
One paper from Hansen et. al. from a number of years ago - sorry I can't find it now - seemed to indicate that as a Earth warmed, deep water submergence transitioned from the polar regions to much lower latitudes, smething of that nature would completely reorder how heat is distributed and could possibly introduce much warmer water into the deep ocean.
It's the scale of this we should always consider and the potential for feedback and impacts that are going to be next to impossible to fully predict or model because we simply don't have the information.
And I realize that being in an environment where much of what I've called home for over 50 years is on fire and some of my family are now short term climate change refugees makes this a much more immediate issue for me.
The methane is there, the conditions are chaotic to say the least and the deep geological record says beware.
At a time when this country - Canada - is still fully committed to burning billions of tons of the least sustainable fossil fuel for decades.
As I said, thanks for the response and I'll dig deeper into this, but I am viewing climate change and our certainty of how it is going to unfold with less and less confidence all the time. At a time when the impacts are becoming the most serious most of society will be in emergency mode just as this entire province is at the moment meaning even monitoring changes effectively could be compromised.
Forget any hope of mitigation at that point.
Responding to this comment. The article above contains a lot of very valuable information. However, you seem to have some misconceptions about clathrates. Firstly, these are not millions of years of accumulations like oil, but instead they can only form in a quite narrow temperature/pressure range mostly from biogenic methane. As temperature changes as it has done in past, then region of stability moves, and yes, if it warms you get melt on top, and the stability region moves deeper. The rate of methane release from clathrates is directly related to rate of temperature increase. Current warming rate is much faster than in past hence the concern. However, as the article above says, there is a lot of fear-mongering that is not substantiated by the science.
I just have to say that I am a little amazed at the gentle tenor of this dialogue considering what is actually going on. I go over and look at the NOAA MetOp-1 date LINK1
and also CAMS
LINK2
and I see LARGE releases of methane constantly coming from undeveloped areas. Methane is skyrocketing and people use GPW100 to express CO2e. Just crazy.Can someone please give me an honest answer?
[DB] Shortened and hyperlinked URLs breaking page formatting.
According to Michael Mann.
“02:13 . . . scientists who have studied this
02:15 problem say yeah there's a certain
02:16 amount of methane that we it could be
02:19 mobilized and it will add to the warming
02:21 but it's a small contribution compared
02:25 to the warming we are causing by the
F02:26 burning of fossil fuels . . . “
https://www.youtube.com/watch?v=LifcMZyCYmc
Hello,
I would be very grateful for any feedback from the as to whether the latest paper from Mrs. Shakova (Understanding the Permafrost–Hydrate System and Associated Methane Releases in the East Siberian Arctic Shelf, Shakova et al, 2019).
I'm just trying to understand whether this paper (and others issued since this article was originally published) has provided any more scientific clarity to the plausability of the abrupt methane release and its potential consequences to the climate and humans.
Sorry for such a question I'm just an ordinary person trying to comprehend all the information which I cannot always properly follow or challenge in any way....
[DB] Thornton et al 2019 had some things to say about some gross errors in Shakhova et al 2019:
"The recent paper in Geosciences, “Understanding the Permafrost–Hydrate System and Associated Methane Releases in the East Siberian Arctic Shelf” by Shakhova, Semiletov, and Chuvilin, (henceforth “S2019”), contains a number of false statements about our 2016 paper, “Methane fluxes from the sea to the atmosphere across the Siberian shelf seas”, (henceforth “T2016”). S2019 use three paragraphs of section 5 of their paper to claim methodological errors and issues in T2016. Notably they claim that in T2016, we systematically removed data outliers including data with high methane concentrations; this claim is false. While we appreciate that flawed methodologies can be a problem in any area of science, in this case, the claims made in S2019 are simply false. In this comment, we detail the incorrect claims made in S2019 regarding T2016, and then discuss some additional problematic aspects of S2019."