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Comments 43051 to 43100:

43051. Leland Palmer at 07:58 AM on 5 August 2013
       Toward Improved Discussions of Methane & Climate
       

       About the graph of the single large release in the original article-

       Nice graph. It's somewhat reassuring, actually, visually.

       But how does it correspond to reality?

       What if that single large release of methane sets off additional releases, of various magnitudes, via increased greenhouse forcing and stimulation of both chronic and large scale individual releases?

       What if that large release severely degrades the hydroxyl radical oxidation mechanism, and causes additional greenhouse forcing and a slower return to chronic methane release behavior?

       What if those atmospheric chemistry effects leading to increased forcing, as postulated by Isaksen's modeling, set off additional methane releases?

       Why should we limit ourselves to a single large release event scenario, when each large release could both amplify chronic releases and possibly stimulate additional large releases, via positive feedback?

       What if increases in both CO2 and methane concentrations lead to higher temperatures, increasing water vapor concentrations, amplifying the combined effects of all the greenhouse gases on radiative forcing? This postive correlation between CO2 concentration and water vapor concentration is well accepted by most climate scientists.

       The methane concentration graph that results could look like a jagged series of peaks, climbing up, and up, and up...

       And not come down...for maybe a hundred thousand years, as apparently happened during other possible methane catastrophes, such as the End Permian.

       Life could regain its former diversity...in several tens of millions of years.

       Except that the sun is hotter now, than it was during the End Permian, by maybe two or thee percent- an effect that James Hansen says is equivalent in forcing to around a thousand ppm of CO2.

       Apparently James Hansen has a new paper coming out, which I have not yet been able to gain access to on the web. The Guardian reports (July of this year):

       
       The world is currently on course to exploit all its remaining fossil fuel resources, a prospect that would produce a "different, practically uninhabitable planet" by triggering a "low-end runaway greenhouse effect." This is the conclusion of a new scientific paper by Prof James Hansen, the former head of NASA's Goddard Institute for Space Studies and the world's best known climate scientist.

       
       The paper due to be published later this month by Philosophical Transactions of the Royal Society A (Phil. Trans. R. Soc. A) focuses less on modeling than on empirical data about correlations between temperature, sea level and CO2 going back up to 66 million years.

       
       Given that efforts to exploit available fossil fuels continue to accelerate, the paper's principal finding - that "conceivable levels of human-made climate forcing could yield the low-end runaway greenhouse effect" based on inducing "out-of-control amplifying feedbacks such as ice sheet disintegration and melting of methane hydrates" - is deeply worrying.

       
       The paper projects that global average temperatures under such a scenario could eventually reach as high as between 16C and 25C over a number of centuries. Such temperatures "would eliminate grain production in almost all agricultural regions in the world", "diminish the stratospheric ozone layer", and "make much of the planet uninhabitable by humans."

       
       Hansen seems to think destabilization of the hydrates via a mixture of chronic and multiple large releases over several centuries is a realistic possibility, with final effects far beyond what Chris Colose or David Archer and his collaborators think is possible.

43052. Andy Skuce at 05:15 AM on 5 August 2013
       Toward Improved Discussions of Methane & Climate
       

       TonyW@26

       Indeed there is gas seeping to the surface from deep sources on the ESAS. A paper by Cramer and Franke (2005) documented this very nicely, with sea-bed samples, gas analyses and deep seismic reflection data. I really do not know why this paper is not cited more widely, since it seems to me to be much more through and detailed than subsequent papers on the ESAS.

       Yes, the methane migrates up gas chimneys through the permafrost, some of which are related to faults. However, this gas release is slow and steady, as evidenced by the fact that it is still ongoing in deeper-water parts of the shelf in the northern Laptev Sea, where there is no permafrost. It might well be the case that melting of the permafrost cap will eventually perforate it in places where it is currently continuous, but this will take time and even when it happens, what we will end up with is what we see in the N Laptev Sea and not a sudden outburst.

       Here's a section from the Cramer and Franke paper, showing gas chimneys, deep structure and permafrost in the central Laptev Sea:

       

       I have written about sub-cap methane in a series of SkS articles: Part1, Part2, Part3 and Part4. In the last one, I speculate on the origin of methane on the ESAS and give my (blogger's) assessment of the relative importance and timing of GHG emissions resulting from a thawing cryosphere.  I think that the one we have to worry about most in this century is the thawing of onshore permafrost and the emissions of CO2 and CH4 that will come from biodegradation of thawed organic matter. There will be some additional releases of thermogenic methane coming from perforation of permafrost caps on land and in shallow seas, but the quantities and the timing of these releases is uncertain. Emissions from hydrates in the deep sea, under and within permafrost and (maybe) under ice sheets, may well prove substantial over longer timescales.

       I would have had no problem with the Whiteman et al article if they had portrayed it as a what-if model of an unlikely worst-case-imaginable scenario. But they did not qualify it that way, instead they wrote (my emphasis, references removed):

       As the amount of Arctic sea ice declines at an unprecedented rate the thawing of offshore permafrost releases methane. A 50-gigatonne (Gt) reservoir of methane, stored in the form of hydrates, exists on the East Siberian Arctic Shelf. It is likely to be emitted as the seabed warms, either steadily over 50 years or suddenly. Higher methane concentrations in the atmosphere will accelerate global warming and hasten local changes in the Arctic, speeding up sea-ice retreat, reducing the reflection of solar energy and accelerating the melting of the Greenland ice sheet. The ramifications will be felt far from the poles.

       which I think is irresponsible.

43053. Andy Skuce at 03:13 AM on 5 August 2013
       Toward Improved Discussions of Methane & Climate
       

       People should take the post by Potomac Oracle with a grain of salt since it is scientifically incoherent. Note that the site that it was referenced from is full of anti-vaccine nonsense. 

       I was taken, though, with the image of formaldehyde crawling along the floor into "open widows". 

43054. wili at 03:07 AM on 5 August 2013
       Toward Improved Discussions of Methane & Climate
       

       One more point/set ofquestions:

       
       Hasn't this been a particularly long interglacial?

       Doesn't that mean that the relative warmth from this long period has had thousands of years now to penetrate deep into the permafrost?

       Doesn't that likely make the permafrost more susceptible now to sudden shocks like seismic activity...than it has been in the past, both during the Holocene and during other, shorter interglacials?

       
       Thanks ahead of time for any light anyone can throw on any of these areas.

43055. Rob Honeycutt at 02:57 AM on 5 August 2013
       An accurately informed public is necessary for climate policy
       

       Terranova @63...  The point of asking the question was to suggest that, at least on a certain level, Obama's statement of AGW being dangerous is inclusive of what is represented by the larger body of published research.

       Whether AGW is dangerous was not an explicit aspect of Cook13, but you could easily state that it is implied by the body of research.  Thus, Obama's tweet is not far from the mark, and therefore a justifiable inclusion.

       Moderator Response:

       [JH] We've beaten this horse to death. Let's move on to another topic. 

43056. KR at 02:54 AM on 5 August 2013
       An accurately informed public is necessary for climate policy
       

       I find this entire line of objections rather absurd. If someone is informed about the scientific consensus on climate change to the extent that they understand 97% of scientists studying it agree on AGW, then they are likely informed enough as to the outlook for future warming (given current economics and policy decisions) and the consensus on consequences thereof (IPCC WG II, "Impacts, Adaptation and Vulnerability") to consider those consequences dangerous. 

       I'll note that one of the major threads of denial is "It's not bad", and from the perspective of those denying AGW that's a frequent accompaniment. But understanding the consensus on the causes of global warming includes understanding the consequences, whether they were specfically addressed in the Cook et al 2013 paper or not. Because knowldge about causes leads to knowledge about effects. And from that standpoint the Obama tweet and other reportings on this issue are entirely reasonable. The objections raised on this thread and elsewhere require a schizophrenic separation between cause and effect, a selective blindnesss to consequences. That is entirely unreasonable, a piece of sophistic nonsense. 

       Just my personal point of view...

       Moderator Response:

       [JH] Let's move on to another topic. This one has been exhausted.

43057. Terranova at 01:53 AM on 5 August 2013
       An accurately informed public is necessary for climate policy
       

       MA Rodger @58

       Now you obfuscate and make suppositions based on your misconceptions about my mindset.  Again, you are failing to recognize that I already supplied an answer - there doesn't have to be an adjective.  

       Let me make it clear for you.  Based on my educational background (B.Sc., M.Sc. and second M.Sc. in progress), and the research I have conducted: I firmly believe that AGW does exist and is having an effect on the global climate.  I cannot say it any more clearly than that.  

       Moderator Response:

       [JH] You have made your point. It has been responded to. Let's move on. 

43058. Terranova at 01:45 AM on 5 August 2013
       An accurately informed public is necessary for climate policy
       

       Tom Curtis @59

       Well said.

       Honeycutt @63

       It certainly could be dangerous. But, that is changing the subject from the point of view of the importance of accuracy. Do 97% of "climate scientists" think it is "dangerous"? There would have to be research done to determine that.  The study was not about whether AGW was dangerous, or not.  It was about endorsing the scientific consensus on AGW.

43059. Potomac Oracle at 00:37 AM on 5 August 2013
       Toward Improved Discussions of Methane & Climate
       

       Andrea Silverthorne writes: http://clck.ru/8mXDo
       
       Natural gas is methane gas.
       
       The T. Boone Pickens' of the world have created a terrible monster. The release of methane into our atmosphere has increased geometrically compared to CO2.  Add to this that the method used to make methane in the earth...shale formations, requires 5 mil. gals of water mixed with a carcinogenic cocktail of chemicals for each well they drill. Only 10% of the water is recovered. The rest mixes with natural carbon to create even more CH4.
       
       (This exessive use of water is why there's a growing dust bowl in the West and N.West, S. West and wherever they drill for oil and gas. Google Dust bowl.)
       
       
       Then, if the CH4 is not completely oxidized to CO2 and remains at its first oxidant HCHO formaldehyde, the HCHO contributes to soft tissue evisceration in man and beast. Ergo, bees disappearing, mass fish and bird kills and over the past five to seven years endemic outbreaks in children of nose bleeds and asthma, and an increase in autism. HCHO hides in shallow water, caves, and dew. It is heavier than air and flows along the ground and into open widows and crawls along floors.
       
       You have people out there who have millions and millions of reams of what they call facts and they spin this kind of web of half-truths and misinterpreted truths and lies, and it’s very difficult for a lay person to go through them. So I try to leave that kind of thing to the scientific community, who are really steeped in scientific literature.
       
       But just having one of these kinds of arguments, unfortunately, people like me and you and those of us who feel like this is really a big problem that we are criminally negligent in not addressing, have kind of lost that public debate right now. And that’s really scary I think, to be honest.” That’s the word I would use, not just depressing but downright scary. There happens to be one side, on the scientific front, that’s just unassailable.  
       
       So let us apply our ethical standards to telling the whole scientific story about the formation of methane hydrates; its formation only with fresh water not sea water unless that water is saturated with methane and over a very short time forms Pingoes.  We can carbon date Pingo material to prove that Pingoes never existed in the Beaufort Sea, the Arctic Tundra or elsewhere before 180 years ago. Oil and gas drilling use of fresh water needs through examination as the only source of methane hydrate, CO2 saturation and exess formaldehyde in our world.
       
       

       Moderator Response:

       [DB] Fixed font issues.

43060. wili at 22:44 PM on 4 August 2013
       Toward Improved Discussions of Methane & Climate
       

       Here are some points I got from Chris's well constructed article:

       We don't know exactly how much methane there is in Siberian shelf.

       We don't know how much of this methane may be stored within the permafrost layer (though we do know that this uppermost layer is the one most vulnerable to warming and melting).

       We don't know whether the massive releases of methane that have been observed are continuations of long-term phenomenon or the beginnings of major feedbacks (this from the first two "Responses from Scientists" who admit that this point is already made by Shakhova).
       
       

       ...I am somehow not comforted by any of these unkowns. The inference seems to be that these are not known, so we can safely assume the most benign end of the spectrum. Is that a legitimate scientific approach to unknowns?

       
       There have been times in the past when temperatures were likely warmer in these areas, but those were also times when sea level was rising rapidly, and methane stability depends on both temperature and pressure (and presumably salinity plays some role, which presumably would have been lowered during the same period with water flowing in from melting ice sheets.

       
       I certainly hope that the conclusion is right: that we are not likely to see massive rapid increases in release of methane from the Arctic sea bed any time soon.

       
       But many of the main points intended to support such a certainty do not seem particularly...certain.

        

       Thanks again for the important discussion (and no less a climatologist than Michael Mann has said that it is important to have discussions about the possibility of rapid increases in methane release from ocean bed hydrates).

43061. TonyW at 19:35 PM on 4 August 2013
       Toward Improved Discussions of Methane & Climate
       This article was linked on another site. The point was made that it doesn't cover free methane, only hydrates. The commenter had this to say:"The warning [of catastrophic release] is about free methane on the ESAS dissociated by geothermal flux and submersion of the shelf over the last 8,000 years and subsequent warming that has degraded the permafrost cap and the methane is now finding pathways to escape from the seabed to the atmosphere. No hydrate dissociation is required. 1 to 2% of the methane on the ESAS is enough to cause catostrophic warming and that is all free methane, not hydrates.Also, the Hydrate Stability Zone is now down to a depth of 1400 meters. The maximum depth of the ESAS is 100 meters, with an average depth of 50 meters.The latest research is showing not only is the degradation of the relic permafrost providing pathways, but seismic activity on the ESAS is creating fissures that are providing pathways for free methane to escape."Any response, Chris?
43062. Paul D at 18:54 PM on 4 August 2013
       Where SkS-Material gets used - Coursera's Climate Literacy Course
       

       I think the Richard Alley course also starts in September.

43063. BaerbelW at 17:23 PM on 4 August 2013
       Where SkS-Material gets used - Coursera's Climate Literacy Course
       

       Richard - there is a course which might fit what you are looking for and it starts on August 12:

       Climate Change - University of Melbourne
       "This course develops an interdisciplinary understanding of the social, political, economic and scientific perspectives on climate change."
       Instructors: Professor Jon Barnett, Professor John Freebairn, Professor David Jamieson, Dr. Maurizio Toscano and Rachel Webster

       And, while on the subject of additional courses in this topic area, there is one more I already signed up for. It starts on Sept. 16:

       Energy, the Environment and Our Future - Penn. State University
       "Get Rich and Save the Earth…Or Else! Learn about the past, present, and possible futures of human energy use."
       Instructor: Richard B. Alley

43064. Richard Komorowski at 15:31 PM on 4 August 2013
       Where SkS-Material gets used - Coursera's Climate Literacy Course
       

       Having studied and written about climate change for quite a while, I would call myself knowlegable, although certainly not an expert.

       I too am nearing the end of this course (just the final to go). Have I learned anything fundamentally new to me? Probably not. On the other hand, I have learned a great deal about how everything fits and interacts together, so all in all I understand the science of climate change better now than I did ten weeks ago.

       I would recommend this course for anyone who is looking for a good overview of the subject. It is an excellent foundation for anyone who wants to progress towards a deeper understanding of the many branches of climate science.

       For myself, I would love to see a course geared towards the politics, economics and sociology of climate change.

43065. Doug Hutcheson at 15:25 PM on 4 August 2013
       Toward Improved Discussions of Methane & Climate
       

       Thanks for this article. I am now less alarmed by Arctic methane than I was.

       The point, however, is moot: even if the was a likelihood of devastating, rapid injections of methane into the atmosphere, there is precious little we could do about it. The future under BAU CO₂ emissions is projected to be so bad that adding a methane menace does not materially affect the outcome for our civilisation, or for our species. Homo Stupidus stupidus.

43066. One Planet Only Forever at 14:09 PM on 4 August 2013
       2013 SkS Weekly News Roundup #31B
       

       The focus of the Times Editorial on planet warming and climate change can be broadened. The concern is the sustainability of the economy. Fundamentally, any economic activity that relies on burning non-renewable resources is not sustainable. The accumulating impacts make it even less sustainable by diverting resources to deal with the climate change consequences.

       So, if the concern really is to develop an economy that can sustainably grow the burning of fossil fuels has to end sooner rather than when the economy fails. The current economy is actually struggling because of all the activity within it that is simply not sustainable.

43067. Rob Honeycutt at 11:37 AM on 4 August 2013
       An accurately informed public is necessary for climate policy
       

       Terranova...  If human activities are responsible for >50% of warming, is that dangerous?

43068. JasonB at 11:17 AM on 4 August 2013
       2013 SkS Weekly News Roundup #31B
       

       Forrest,

       I did a quick test for "Industrialised Countries" (red flag there — trying to pretend that everyone else will continue BAU will of course reduce the impact of the actions of a subset of countries), 100% reduction, and 3°C degrees sensitivity, and it said that by 2100 the consequence would be a reduction of 0.278°C compared to A1B (second red flag, since they're really advocating A1FI, and A1B doesn't really equate to "do nothing about climate change", which is precisely what they're trying to suggest).

       The IPCC temperature change for 2090-2099 relative to 1980-1999 for each scenario shows a range of -1.0°C relative to A1B (for B1) up to +1.2°C (for A1FI). That's a difference of 2.2°C depending on emissions scenario, and even B1 with its 1.0°C drop relative to A1B isn't as agressive as their purported scenario from what I can see.

       If it was actual science rather than simply propaganda I'd expect them to explain why they think their results are so small compared to what people might expect rather than just present it as "fact" with no more to say about it.

43069. David Kirtley at 11:14 AM on 4 August 2013
       Where SkS-Material gets used - Coursera's Climate Literacy Course
       

       I took this course too and thought it was very good.  I highly recommend it.  My next Coursera class will be on Statistics.

43070. Forrest at 10:08 AM on 4 August 2013
       2013 SkS Weekly News Roundup #31B
       

       Encouraging to see the NY Times editorial.  However, the comments in the Times include a reference to a "Handy-Dandy Carbon Tax Temperature-Savings Calculator" created by the CATO Institute which claims to calculate the temperature impact in the year 2100 of reducing CO2 emissions by a user-selected amount for the next 50 years.  

       The comment says that eliminating all CO2 for the next 50 years will mean global temperature is 0.28 degrees C lower than it would have been otherwise.  The commenter claims this is equivalent to moving 10 miles south.  This makes no sense.  Assuming 12,000 miles from the pole to the equator, then 0.28 degrees per 10 miles means an average temperature difference of 336 deg C between the pole and equatotor.  

       Would someone more knowledgable than I take a look at the calculator and comment on whatever other "issues" it may have?

43071. Composer99 at 09:28 AM on 4 August 2013
       It's not bad
       

       without appropriate context noting studies like this distorts our necessary perception and responses to climate change

       You mean such as, say, omitting the peak season for influenza in the United States from consideration?

       With studies such as this, or news articles such as this, it appears much of the seasonal mortality in winter is the result of not the weather, but of the seasonal variation in influenza circulation.

       Or perhaps you mean, say, referring strictly to seasonal trends in mortality in a single country rather than from a global perspective?

43072. Sceptical Wombat at 09:04 AM on 4 August 2013
       Where SkS-Material gets used - Coursera's Climate Literacy Course
       

       Also starting in September is a MOOC on Solar Energy being run by Delft University of Technology in the Netherlands on EdX.  This looks like a fairly technical course.

43073. Daniel Bailey at 09:01 AM on 4 August 2013
       It's not bad
       

       Hmm.  Available evidence shows that it is the human adaptation to weather extremes that is key in limiting mortality.  Evidence for that assertion:

       "Adaptation measures have prevented a significant increase in heat-related mortality and considerably enhanced a significant decrease in cold-related mortality. The analysis also suggests that in the absence of any adaptive processes, the human influence on climate would have been the main contributor to both increases in heat-related mortality and decreases in cold-related mortality."

       and

       "With regard to heat-related mortality, projected future increases in the frequency and intensity of heat waves may exert a stress beyond the adaptive limits of the population."

       Causes for the recent changes in cold- and heat-related mortality in England and Wales
       Nikolaos Christidis, Gavin C. Donaldson, Peter A. Stott; Climatic Change, October 2010

        

       That's called supporting an assertion with evidence.

43074. John Hartz at 07:55 AM on 4 August 2013
       It's not bad
       

       @Ray Coleman #352

       You blithely assert, 

       Intermittent Heatwave 'costs' in terms of mortality are insignificant compared to the 'benefit' of a warmer continental US.

        Please provide documentation to support your statement.

43075. Roy Coleman at 07:06 AM on 4 August 2013
       It's not bad
       

       "Increased deaths to heatwaves - 5.74% increase to heatwaves compared to 1.59% to cold snaps (Medina-Ramon 2007)"

       SO? This has no context in terms of the general population mortality. The CDC figures on US death rates (2007-8) are quite clear, 900 more people per million die in cold weather, at temperatures below 12 degrees, that's in excess of 250000 people annually! Intermittent Heatwave 'costs' in terms of mortality are insignificant compared to the 'benefit' of a warmer continental US. You must excuse me but without appropriate context, noting studies like this distorts our necessary perception and responses to climate change.

        

43076. Leland Palmer at 04:49 AM on 4 August 2013
       Toward Improved Discussions of Methane & Climate
       

       By the way, even if most of the methane doesn't make it into the atmosphere, it could still do the biosphere major harm via ocean acidification, as it oxidizes into CO2 in the oceans.

       I seem to recall seeing a modeling paper of this phenomenon in the Arctic ocean, which predicts that chronic methane release from the hydrates would overwhelm the oceans ability to absorb and oxidize the methane, and lead to more direct venting of methane to the atmosphere.

       There are also suspicions that anoxic oceans could increase their production of NOx, I think.

       As gws said, the atmospheric chemistry effects of methane release have to be considered- but so do the oceanic chemistry effects.

       In his book "Under a Green Sky" Peter Ward talks about the truly catastrophic effects of massive methane release on the oceans, including anoxia and proliferation of strange bacteria. We're not there yet, and have a long way to go before things get that bad.

       But, once it starts, could we stop the process? 

43077. gws at 04:26 AM on 4 August 2013
       Toward Improved Discussions of Methane & Climate
       

       I would like to emphasize a point made by Leland, namely that further increasing atmospheric methane will have significant impacts on atmospheric chemistry. Increased atmospheric methane tends to decrease OH radical abundance and increase ozone abundance under current NOx availability, which increases atmospheric pollutant lifetimes and further stresses ecosystems (via ozone).

       A review paper by Wuebbles and Hayhoe can be found here. The potential changes described in the more recent Isaksen paper cited by Leland are indeed "alarming", wherefore the atmospheric chemistry community does place a priority on how methane sources may change, including due to AGW factors.

       Humans have so far approx. trippled the amount of methane in the troposphere (particularly via meat consumption, rice cultivation, and organic waste dumping; aka via boosting methanogenesis, but also via fossil fuel extraction and use), and more adverse atmospheric chemistry effects of that have so far not occurred due to a rather stable cleansing capacity of our atmosphere (supported by our simultaneous pollution of it with NOx). But as its response is non-linear, an out-of-control increasing methane source strength could be devastating, regardless of its speed.

       Meaning, even if the chances of a rapid release are remote from today's point of view, if there is a large reservoir that could be released to the atmosphere, we should be very concerned about that possibility and take any and all preventive action to stop it from actually doing so, regardless of the speed of release.

43078. John Mason at 02:52 AM on 4 August 2013
       Toward Improved Discussions of Methane & Climate
       

       Michael, #21,

       I agree to an extent - what we are doing here WRT atmospheric composition may be unprecedented in the entire Phanerozoic in terms of rate. On that basis, Chris, are we not comparing apples and oranges? It may be completely irrelevant that nothing like the things Wadhams is concerned about appear to have occurred over the past few glacial-interglacial cycles: nothing within them, apparently at the very l;east, occurred so quickly. One to consider!

43079. michael sweet at 02:24 AM on 4 August 2013
       Toward Improved Discussions of Methane & Climate
       

       Glenn,

       Since the forcing today is much greater today than in the PETM (at least 10 times greater), why do you suppose the methane releases during the PETM are the maximum speed possible?  Since the forcing is so much greater, it stands to reason that the methane release will also be much faster.  Can you explain your argument?

43080. acjames76 at 01:31 AM on 4 August 2013
       Where SkS-Material gets used - Coursera's Climate Literacy Course
       

       I started the course near the end, but it will be worthwhile starting it again.  The instructors say:

       We are planning a second offering of Climate Literacy, likely to start in late September. If you have friends, family, or colleagues you think would like to participate, they can currently click the "Add to Watchlist" button on Coursera. Soon there will be a button to actually register for the second offering.

43081. Leland Palmer at 01:25 AM on 4 August 2013
       Toward Improved Discussions of Methane & Climate
       

       Hi Glenn Tamblin at post # 18-

       It's true that methane hydrate dissociation is an endothermic process and that there may be a rate limit to its release. 

       A lot of the total methane release from the hydrates depends on the total methane hydrate inventory, though - the total amount that exists on the earth. 

       Estimates, as you know, range from about 400 billion metric tons to about 77 trillion metric tons - roughly 440 to 85,000 cubic kilometers.

       That's a big range, Glenn.

       Archer and his collaborators estimate we have something like 4,000 cubic kilometers of methane hydrate, while Dickens and his collaborators talk about a consensus estimate of around 10,000 to 20,000 cubic kilometers. I've seen a paper on the End Triassic which talks about roughly 13,000 cubic kilometers released, rather slowly, which in my mind casts doubt on the lower estimates of total hydrate inventory.

       So, first point, we don't know how much hydrate is down there, on the continental shelves. Multiply a low rate of dissociation by a large hydrate inventory, and one can arrive at a high total methane release. This alone argues that complacency is contraindicated.

       Since we are coming out of a series of ice ages, with low ocean temperatures promoting hydrate stability, we could in fact have massive amounts of hydrate in the global hydrate inventory. And hydrate deposits which are uneconomically thin or scattered and useless to the fossil fuel corporations, not worth mapping, really- might release methane even more rapidly than the economically valuable deposits, because of their scattered and porous nature- especially if they are shallow deposits.

       Some of the papers I've looked at  on hydrate dissociation assume that the convoluted three dimensional hydrate deposits, full of chimneys large enough to show up quite well on sonar, will act like a one or two dimensional model spread uniformly over a two dimensional surface- a highly questionable assumption. Complicated real world processes like convection, convoluted geometry, and chimneys, could make such estimates seriously underestimate the rate of methane release from the hydrates.

       I don't want to bet the future of the biosphere on models of hydrate dissociation which could easily be wrong due to the highly fractured nature of hydrate deposits, often full of chimneys from past release of methane. 

       My conviction is that if we surround the hydrate deposits with warmer water, the deposits will find a way to dissociate, via complicated mechanisms including convection and release of pressure build up of associated free methane gas reservoirs. Undersea landslides are a distinct possibility, especially after substantial methane release has weakened the deposits. So, the landslide phenomenon could be an accelerating process.

       The methane gun hypothesis of mass extinctions requires a trigger mechanism, to set off the hydrates- generally a rapid rise in CO2 is postulated. 

       The fact that our modern triggering event is so much more rapid than past triggering events makes me more alarmed rather than less alarmed. The rate that Lee Kump observed for PETM hydrate dissociation might be characteristic of that event given a much slower triggering event, less severe positive feedback effects, and the methane hydrate geographical distribution at the time.

       Regarding geographical distribution- the location of the East Siberian Arctic Shelf, located as it is under the most rapidly warming region on the planet, is particularly worrisome. Another worrisome thing is the current imbalance in ice distribution with most of the ice located in Antarctica. It seems possible that we could have a full blown methane catastrophe occurring in the north, while Antarctica remains relatively intact. This would slow water rise, which in the past has helped stabilize the hydrates due to a rise in hydrostatic pressure by increased water levels.

       There are times in life when alarm is appropriate, and this is one of those times, I believe.

43082. wili at 23:37 PM on 3 August 2013
       Toward Improved Discussions of Methane & Climate
       

       "undersea avalanches"

       Why shouldn't these be one of the mechanisms by which methane may be suddenly released from the ocean floor. IIRC, the sea bed in the ESAS is not perfectly flat. There are deep 'canyons' where such sudden events may take place. Since the permafrost has been warming gradually over much of the Holocene, and much more rapidly lately, its structure is doubtless less solid than it would otherwise be.

        

       We have seen warmed ice start to deform this way in the GIS recently.

        

       http://www.youtube.com/watch?v=qkpFNteryX8&list=UUtZdUYUZr493AUh_EInBYxQ&feature=player_detailpage

        

       And, of course, such weakened ice would also be more susceptible to seismic shocks.

        

       In any case, there do seem to be potential 'pathways' to consider. The proper thing is to analyze the relative likelihood of each, rather than just sweeping the whole thing under the rug.

43083. MA Rodger at 23:19 PM on 3 August 2013
       An accurately informed public is necessary for climate policy
       

       Barry Woods @61.

       (-snip-)?

       Moderator Response:

       [DB] Apologies, but responses to Repetitive & Sloganeering snipped comments must also be snipped.  Barry's comment added nothing to this discussion and was necessarily treated accordingly.

43084. Glenn Tamblyn at 19:24 PM on 3 August 2013
       Toward Improved Discussions of Methane & Climate
       

       Leland @16

       The PETM offers an interesting reference point for just how fast methane release might happen. It isn't clear what all the sources of CO2 released during the PETM were - subsea avalanches exposing methane clathrates, Antarctic permafrost, rupturing of Natural Gas deposits near Brazil are all plausible. But we do know something about the rate that CO2 levels changed.

       Lee Kump and his colleagues were able to use a core taken from near Svarlbad to give us an estimate of how fast CO2 levels were rising during the PETM. The rate was 10 times slower than today.

       Even if we assumed that all the observed CO2 rise back then originated 100% as Methane that was oxidised to CO2 it is still only 10% of current emissions of CO2. This suggests that there is an upper limit to how fast Methane will outgas today at less than 10% or so of current CO2 emissions. Particularly since no one is suggesting such dramatic triggers as undersea avalanches as part of the mix today.

       That isn't to say that the long term total emissions of Methane may not be very substantial. Just that there is a speed limit on the rate.

43085. Barry Woods at 19:07 PM on 3 August 2013
       An accurately informed public is necessary for climate policy
       

         (-snip-)

       Moderator Response:

       [DB] Repetitive & sloganeering snipped.

43086. TonyW at 18:58 PM on 3 August 2013
       Toward Improved Discussions of Methane & Climate
       Good, useful article. Thanks.One point. How would the graph showing what might happen to a nearly instantaneous pulse of methane change if there was a gradual but significant increase in methane release? Is that more likely?I note that CH4 concentration in the atmosphere is increasing at the moment, following a few years of level concentration. Although methane may be 25 times as powerful as CO2 over 100 years, I understand that it may be as much as 100 times as powerful over a few years. Given that methane concentrations are increasing and, therefore, the degradation rate is not even keeping up with the rate of new releases, never mind exceeding it, isn't the more powerful factor of 100 a more realistic one to use? I'm not sure which factor is used in your estimate of ~0.5 W/m2.
43087. John Mason at 16:55 PM on 3 August 2013
       East Antarctica Ice-Sheet more vulnerable to melting than we thought: new research
       

       Agnostic,

       I agree with you that nothing drastic is likely to happen to the EAIS for the time being, with sea-level rise coming from the other sources you cite.

       However, I think we need to take a good hard look at the Pliocene, because we have driven one parameter straight into that era in a matter of a few centuries. How our current climate evolves in response to having a Pliocene atmosphere imposed upon it remains to be seen, but we need to be aware of what is possible....

43088. Leland Palmer at 16:22 PM on 3 August 2013
       Toward Improved Discussions of Methane & Climate
       

       Yes, but Chris, methane catastrophes have arguably happened before, during the End Permian, the End Triassic, a couple of events in the Jurassic, and the End Paleocene (aka the PETM). Certainly, there have been a series of mass extinctions, with similar signatures in the carbon isotope ratios- a massive carbon isotope excursion best explained by the entry of several trillion tons of C12 enriched hydrate methane into the atmosphere. Or, one could postulate much, much larger amounts of CO2- except that the math does not quite work out.

       So, it's not just a theoretical possibility, is it?

       Whatever the source of methane, from decaying permafrost or methane hydrates, it was arguably sufficient to end several geological eras, right? 

       Tell me again why I have to meet your criteria before I become alarmed?

       Shouldn't we err on the side of caution, when we're talking about the fate of the biosphere?

       Isn't climate change in general, and warming in the Arctic in particular, occuring much, much more rapidly than predicted? 

       The hydroxyl radical oxidation mechanism which oxidizes methane into CO2 is also impacted by large releases of methane. Isaksen and his collaborators claim the following:

       Strong atmospheric chemistry feedback to climate warming
       from Arctic methane emissions

       It is shown that if global methane emissions were to increase by factors of 2.5 and 5.2 above current emissions, the indirect contributions to RF would be about 250% and 400%, respectively, of the RF that can be attributed to directly emitted methane alone. Assuming several hypothetical scenarios of CH4 release associated with permafrost thaw, shallow marine hydrate degassing, and submarine landslides, we find a strong positive feedback on RF through atmospheric chemistry. In particular, the impact of CH4 is enhanced through increase of its lifetime, and of atmospheric abundances of ozone, stratospheric water vapor, and CO2
       as a result of atmospheric chemical processes

       It's my alarm, Chris.

       I can't be alarmed without your permission?

        

43089. Robert Marston at 13:00 PM on 3 August 2013
       Toward Improved Discussions of Methane & Climate
       

       The issue I have with this article is that it paints scientists who have found evidence of a potential rapid methane release as a near equivalent to climate change deniers.

       In addition, the article clearly sides with scientists who have a very conservative view on the issue of methane release. So conservative, in fact, that all science indicating a potential for anything other than a very slow release is painted in a light so as to be considered false.

       Though PETM ocean floor heating, slope collapse and methane hydrate release theory as a mechanism for final rapid atmospheric heat increase and coordinate anoxic ocean state are just that, numerous scientific papers support evidence for such events. Wadhams and Shakova are just a few of the scientists who have issued concerns for such events in a contemporary ocean and land system due to human caused warming. Hansen, for example, has mentioned risk of methane release, both from hydrates and from land material, as a reason for keeping human CO2 levels low. So I must ask the question? Is Hansen being irresponsible?

       Further, this particular post seems to fail to take into account contemporary research showing high risk of a substantial contribution from Arctic carbon stores in the form of both methane and CO2 on the order of 43 to 135 gigatons CO2e by 2100. The study, conducted by a number of scientists for the UN is available here:

       http://www.unep.org/newscentre/default.aspx?DocumentID=2698&ArticleID=9338

       Were these scientists being irresponsible by indicating methane as a potent amplifying feedback from now to 2100 and even moreso through 2200?

       Now this particular study does not specifically indicate a potential yearly release on the order of 1-50 gigatons methane, as Shakova warns is possible. But it does indicate methane as an amplifying feedback of significant magnitude on a time scale that includes a more rapid response than that seen in the Eemian or during the most recent interglacial. It also, contrary to what Archer has stated in earlier articles, shows that emissions lower than this level are significant.

       I suppose what I find most concerning is the fact that Skeptical Science seems to have hitched itself to the, albeit professional, opinion of a few scientists who are very conservative on the issue of methane release without attempting to identify probabilities for a catastrophic release or exploring a middle ground, available in a number of reports, in which release is an important addition to CO2 forcing. The science, on this issue, includes all the scientists -- Shakova, Wadhams, Hansen, White, and others showing evidence of potential catastrophic release, others whose models indicate a more modest release, and Schmidt, Archer and others who seemingly believe that methane is almost a non-issue when it comes to climate change.

       To quote NASA scientist and CARVE researcher Charles Miller:

       "Permafrost soils are warming even faster than Arctic air temperatures - as much as 2.7 to 4.5 degrees Fahrenheit (1.5 to 2.5 degrees Celsius) in just the past 30 years," Miller said. "As heat from Earth's surface penetrates into permafrost, it threatens to mobilize these organic carbon reservoirs and release them into the atmosphere as carbon dioxide and methane, upsetting the Arctic's carbon balance and greatly exacerbating global warming."

       Is Charles Miller the alarmist equivalent of a climate change denier or are his points worth considering? I'd, therefore, compell Skeptical Science to widen its scope in coverage on the issue of methane. The breadth of science indicates instances of Arctic emissions happening now, not at catastrophic levels, but at levels indicative of concern. A valid theory supported by top scientists shows potentials for catastrophic releases of hydrates during major ocean warming events. More moderate research indicates a likelihood of significant but not catastrophic releases from now to 2100. Since neither Archer nor Schmidt can provide compelling evidence as to why their theory of 'slow release' should dominate, since they rely on a static rather than dynamic view of Arctic systems (Eemian and Holocene corrollaries), and since they seem to exclude other Earth Systems Sensitivity factors, it would seem that their views require much stronger evidence to be reassuring and that we should still consider Wadhams, Hansen and Shakhova as providing a valid warning worthy of policy consideration.

       Finally, if Schmidt and Archer are correct, then we lose nothing except a little extra effort and gaining more certainty and resiliency by acting. But if Wadhams, Shakhova and Hansen are correct, then in failing to act and gain greater understanding of potential risks, we lose a great deal.

       ....

43090. christopherwrightau at 11:15 AM on 3 August 2013
       Where SkS-Material gets used - Coursera's Climate Literacy Course
       

       Yep I've just finished this MOOC and it was a great course that I can thoroughly recommend. Well structured and presented and the constants testing was actually very good re knowledge application and retention. The intro to climate science was excellent for my social science sensibilities and it was also a lot of fun.

       Running again in September - so well worth doing.

43091. Riduna at 10:20 AM on 3 August 2013
       East Antarctica Ice-Sheet more vulnerable to melting than we thought: new research
       

       It is certainly possible and may be likely for the polar ice sheets to disappear, causing sea level rise (SLR) of 22 +/- 10 metres over coming millennia. Of more immediate concern is what can be expected to occur over the course of this century. The Letter from C.P. Cook et al (2013) implies that what occurred in the Pliocene is a reasonable indicator to what may happen in the immediate future. That seems questionable, as is the suggestion that some 50% of future SLR could come from ice mass loss from the East Antarctic Ice Sheet.

       SLR by 2100 is more likely to come from ice mass loss from West Antarctica (WAIS) where warm ocean currents are already melting ice at glacier mouths and attacking areas of the WAIS resting on the seabed. Atmospheric warming does not appear to contribute to ice mass loss from either the EAIS or WAIS, other than the “Peninsula”.

       This is not the case in the Arctic where loss of ice from the Greenland Ice Sheet (GIS) and Canadian Islands is caused by rising atmospheric temperature and a warming Arctic ocean. The latter is caused by penetration of warmer sea currents and loss of albedo causing increased exposure to sunlight. Further, loss of land based ice is more likely to accelerate due to Arctic amplification contributed to by methane emissions and evidenced by temperature rise at over twice the global average.

       By contrast atmospheric temperature amplification is not evident in the Antarctic which is insulated by relatively stable circumpolar winds, persistent sea-ice coverage and the loss of tropospheric ozone. All have the effect of maintaining the coldest atmospheric temperatures in the world. Warmer bottom currents from the tropics do reach the EA coast and there is evidence that these enable increased ice loss from some EAIS glaciers. However, the EAIS is entirely land based and, unlike the WAIS which is a marine ice sheet, relatively impervious to warm ocean currents.

       Both the WAIS and EAIS are loosing ice mass but the latter is doing so at a much slower rate. For these reasons it is argued that SLR to 2100 is most likely to come from the GIS with exposure to Arctic amplification and WAIS which is vulnerable and exposed to warm ocean currents. EAIS seems unnlikely to be a major contributor this century.

       Finally, is it legitimate to compare conditions during the Pliocene, which took hundreds of millennia to evolve, with present conditions which have taken just a few decades to evolve thanks to human intervention. Do present EAIS conditions equate to those which prevailed in the Pliocene?  

43092. Tom Curtis at 09:56 AM on 3 August 2013
       An accurately informed public is necessary for climate policy
       

       For what its worth, the Bray and von Storch survey show 83.51% of climate scientists to be convinced that most of "recent or near future climate change was, or will be, a result of anthropogenic causes", showing the concensus that GW is dangerous is almost as great as that it is anthropogenic. 

43093. Tom Curtis at 09:52 AM on 3 August 2013
       An accurately informed public is necessary for climate policy
       

       MA Rodger @58, the tweet clearly indicates that 97% of climate scientists agree that gobal warming is real, that it is man made, and that it is dangerous.  That each proposition is true seperately does not make it true that 97% of climate scientists agree with each proposition.  It certainly does not make it true that Cook et al 2013 show them to have believed it.  In fact, Cook et al showed endorsement in the literature, in papers stating an opinion, not being restricted to climate scientists, of the idea that global warming was real and man made.

       Consequently it would not have been out of order for John Cook to have issued a correction on any of those inaccuracies in the tweet.  In particular, it would have been quite appropriate to issue a correction saying that the papers endorsed the concept that climate change was real and man made, but that even though it is dangerous, the study did not examine the endorsement of that view.  Ergo Terranova has a point, and is not quibbling.

       I am not convinced, however, that it was compulsory on Cook or any of his coauthors to issue a correction.  If it was, surely it was compulsory to issue the correction on every point of inaccuracy, yet Terranova only seems vexed by the term "dangerous".  Further, if it was compulsory to issue a correction on Obama's tweet, then surely it is compulsory to issue a correction for every misrepresentation of the study - which is absurd.  There are not enough hours in the day.

       So, if not compulsory, does it not then enter the realm of a judgement call as to whether the inaccuracies were sufficiently misleading require correction.  Claiming the 97% of scientists believe the changes to be beneficial would have a far greater demand on correction than Obama's tweet, for other surveys have established that .  Bray and von Storch's survey shows that 78.92% of climate scientists are convinced that climat change "... poses a very serious and dangerous threat to humanity", with only 1.162% "not at all convinced".  (There is, IMO, a problem with the wording of their survey question that will bias the response low.)  So, correcting terrranova's hypothetical alternative would be correcting a radical mistatement of the facts.  In contrast, correcting Obama's tweet would be correcting inaccuracies in details (though potentially significant details).

       So, yes it would have been nice of Cook corrected those details when acknowledging the tweet.  But not compulsory, and not dishonest to find better things to do with his time.

43094. Lyndal at 09:51 AM on 3 August 2013
       Where SkS-Material gets used - Coursera's Climate Literacy Course
       

       I have done two Coursera subjects and found both to be excellent. Adjusting to the slight differences between the ways the subjects are set up was difficult at first, but the same happens between subjects in real life University studies.

43095. Chris Colose at 09:29 AM on 3 August 2013
       Toward Improved Discussions of Methane & Climate
       

       Phil,

       Yes, CO2 is a product of methane oxidation (along with water vapor, which ends up having a non-negligible climate forcing in the stratosphere). 

       For fairly small perturbations, the "extra CO2" after oxidation isn't really important because there's so little of it.  There's a lot more CO2 in the atmosphere than methane.  So even if you turn methane into an extra ppm of CO2, that's not even a years worth of fossil fuel burning.  For much larger methane releases, however (hundreds to thousands of gigatons), that can add on significantly to the long term radiative forcing, even after oxidizing to CO2.  They key here is the different lifetimes of the two gases, which isn't adequately captured in existing metrics to compare different gases (like GWP).  

       The fate of a big methane injection after it oxidizes comes up in some deep-time discussions, like Snowball Earth.  By the way, for slow releases, you'd sustain higher steady-state methane concentrations during the timeframe that the release is occurring. So a slow release is still an issue.   But it's unclear to me that methane has ever been a "huge" player in climate change on Earth, at least since the planet was filled with lots of oxygen in its atmosphere (I use the word "huge" in a bigger-picture context than the still significant radiative forcings that we're talking about for contemporary global warming, e.g., for the evolution of climate over the last 60 million years, or the deglaciation of a Snowball Earth). For understanding the evolution of global climate, CO2 is much more first order.

        

43096. Tom Curtis at 09:21 AM on 3 August 2013
       2013 SkS Weekly News Roundup #29B
       

       Andy @59, the analogies are poorly designed for your purpose.  When I buy milk for my children, nobody calls that a subsidy because it is just part of my parental responsibility.   In contrast, if the government were to buy milk for my children (at school, for example), there would be no question that that would be a subsidy.  Consequently the entire force of your first analogy depends on a context in which talk of subsidy is simply inappropriate, and has no bearing on the issue at hand.

       With the renewable energy cooperative, the question arises as to the purpose for which the cooperative was established.  If it is to generate energy for sale as a source of income, then there is no question that the below market cost energy is subsidized.  More properly, it means taking profits in the form of cheaper energy rather than in cash payments; and if the result is a different distribution of receipts, it means the cheap energy is subsidizing some members of the cooperative at the expense of the others.

       More commonly, however, renewable energy cooperatives are founded for the primary purpose of providing the members with cheap renewable energy.  In that case it is not a subsidy, but only because the cooperative is fulfilling the purpose for which it was formed, and for which its members paid.

       In either case your analogy is inaccurate.  In the first because it is genuinely a subsidy.  In the second because the constitutional arrangements make specific talk of a subsidy inaccurate.

       As I am sure we will all agree that the Saudi Government was not formed for the purpose of providing cheap oil to Saudi citizens, neither of the analogies shed any light on the issue.

43097. JasonB at 09:17 AM on 3 August 2013
       2013 SkS Weekly News Roundup #29B
       

       Andy, I agree with scaddenp, and these aren't even close to being as tricky as some countries get when trying to avoid the label.

       We also had a dairy cow when I was a kid and, just like any subsidised consumption, we certainly drank a lot more milk than we would have otherwise.

       If a child (citizen) puts milk in the cart and takes it to the checkout, and the father (government) whips out his wallet and pays for the milk, then that is clearly the normal case when people think of the word "subsidy". But the net effect is the same if the father is a farmer who foregoes the income he would have received from selling that milk and gives the milk to the child directly. Milk becomes an artifically cheap commodity, and is over-consumed relative to what its level of consumption would have been had the milk been sold and the money then used to buy whatever was desired at market rates.

       Anyway, the WTO document scaddenp previously linked to clearly states:

       Secondly, the government may provide goods or services at no cost or below market price, such as university education, public transport or food stamps. Such transfers also involve expenses for the government, with the difference being that beneficiaries receive in-kind contributions as opposed to funds they can freely dispose of.

       as one of the three categories of subsidies and it also says that the WTO definition of subsidy includes:

       (ii) foregone revenues that are otherwise due

       To me, this would clearly include Saudi oil. And, has been noted multiple times already, the Saudi government itself considers this to be a subsidy.

       I can think of other examples that are similar and nobody seems to have problems calling them subsidies. In Australia we have subsidised medicine, subsidised health care, subsidised education, and subsidised housing for the poor. In each case the question is simply whether the cost to the end user is below market rates, not how much it cost nor which country it originated in.

       Consider a drug on the PBS (which Wikipedia calls a program "that provides subsidised prescription drugs to residents of Australia") for example; it's considered "subsidised" if I can buy it at the standard rate of $36.10 but the normal market price was higher than that. (If it was lower, it wouldn't be on the PBS — not all drugs are.) It doesn't matter what the actual cost of production of that drug is (which, in general, will be substantially lower, as evidenced by the massive price drop when patent protection expires and competitors start producing it), and it doesn't matter what country that drug was produced in (so if the pharmaceutical company happened to be Australian, then, just like the Saudi oil, we'd be buying our own drugs at below-market rates, and it would still be a subsidy).

       I don't know why Saudi oil being subsidised should be a controversial claim. If BHPB and Rio Tinto were forced to sell iron ore to Australians for $23.50/tonne rather than the going market rate, wouldn't that be a subsidy? (BTW, it's funny how weird that idea sounds, and what an uproar it would provoke about "Sovereign risk" if the government were to try to impose a rule guaranteeing Australian citizens unlimited consumption of iron ore at extraction costs! I suspect the WTO would also take an interest on the effect it would have on the competitiveness of the Australian steel industry.)

43098. Tom Curtis at 09:10 AM on 3 August 2013
       Toward Improved Discussions of Methane & Climate
       

       deweaver @9, the Nature article explicitly cites independent literature to justify the claim of the potentialy large methane release.  It takes that claim from elsewhere and examines the potential economic impacts of such a release.  Given that, the lack of the technical discussion you are looking for is irrelevant.  Science builds on science.  If some other scientist has established a point to your satisfaction, it is not necessary to reestablish that point in any paper you publish seeking to use those results.  Consequently your claim that this is "advocacy science" is unwarranted, and reads like a simple slur intended encourage dismissal without thought.

       Please note that I say this despite being convinced by the evidence Chris Colose adduces that such a release is very unlikely, and also evidence from a David Archer article on Real Climate.  Science does not work be expecting all scientists to be convinced by what convinces you. 

43099. Tom Curtis at 08:57 AM on 3 August 2013
       Toward Improved Discussions of Methane & Climate
       

       Phil @11, the methane (CH4) does oxidize to form a CO2 molecule and and two H2O molecules, the later condensing out of the atmosphere.  The CO2 has a significantly less powerful greenhouse effect per molecule than does CH4.  Therefore the result of the oxidation is to greatly decrease the greenhouse impact of the methane release.  And, yes, this is taken into account in modeling of the effecs of a methane release on climate.

43100. Phil at 08:15 AM on 3 August 2013
       Toward Improved Discussions of Methane & Climate
       

       Excuse the ignorance, but its often stated that methane has a comparatively short residency in the atmosphere, and so I've always assumed that the majority oxidises to CO2. Is this correct ? If not, what is the stable form of carbon that methane decomposes to.

       On the contrary, if so, is the extra CO2 generated by the any methane "plume" (of whatever size/duration) generally taken into account when modelling such scenarios ?

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