There is an enormous amount of methane (CH4) on earth frozen into a type of ice called methane hydrate. Hydrates can form with almost any gas and consist of a ‘cage’ of water molecules surrounding the gas. (The term ‘clathrate’ more generally describes solids consisting of gases are trapped within any kind of cage while hydrate is the specific term for when the cage is made of water molecules). There are CO2 hydrates on Mars, while on Earth most of the hydrates are filled with methane. Most of these are in sediments of the ocean, but some are associated with permafrost soils.
Methane hydrates would seem intuitively to be the most precarious of things. Methane hydrate melts if it gets too warm, and it floats in water. Methane is a powerful greenhouse gas, and it degrades to CO2, another greenhouse gas which accumulates in the atmosphere just as fossil fuel CO2 does. And there is a lot of it, possibly more than the traditional fossil fuel deposits. Conceivably, climate changes could affect these deposits. So what do we know of the disaster-movie potential of the methane hydrates?
Ocean hydrates. Most of the methane hydrate is in sediments of the ocean. Of that, most is what can be called the stratigraphic-type deposits. Organic carbon from plankton is buried over millions of years. Hundreds of meters below the sea floor, bacteria produce methane from the dead plankton. If methane is produced quickly enough, some of it will freeze into methane hydrates. This type of deposit holds thousands of gigatons of carbon as methane [Buffett and Archer, 2004; Milkov, 2004]. For comparison, the most abundant type of traditional fossil fuel is coal, which is typically credited with about 5000 Gton C [Rogner, 1997].
Sometimes the methane moves around in the earth, and collects someplace, forming what are called structural hydrate deposits. The Gulf of Mexico, for example, is basically a leaky oil field [MacDonald et al., 2005]. One implication of gas moving around and pooling like this is that the hydrate concentration can be higher, even to the point of what they call massive deposits, lumps of nearly pure hydrate. The second bottom line is that the hydrate can be found much closer to the sea floor, and even on the sea floor.
Hydrate melts if it gets too warm. The ocean is cold enough in a depth range from say 500 meters down (200 meters in the Arctic). Below the sea floor, the temperature increases with depth, along the geothermal temperature gradient. At some depth it becomes too warm for hydrate, so hydrate melts if it becomes buried deeper than this depth. There is often a layer of bubbles beneath the hydrate stability zone. The bubbles reflect seismic sound waves, and show up clearly in seismic surveys around the world [Buffett, 2000]. Hills and valleys of the bubble layer follow hills and valleys of the sea floor, so this layer is called a bottom-simulating reflector (BSR).
Now let’s warm up the water at the top of the sediment column. Ultimately, the new temperature profile will have nearly the same slope as before, the geotherm. The hydrate stability zone will get thinner with an increase in the sediment column temperature. The important thing to note is that it gets thinner from the bottom, not from the top. Hydrate at the base of the original stability zone finds itself melting.
If the stability zone still exists, it will be shallower in the sediment column than the newly released methane bubbles, and so it could act like a cold trap to prevent the released methane gas from escaping. However, seismic studies often show “wipeout zones” where the BSR is missing, and all of the layered structure of the sediment column above the missing BSR is smoothed out. These are thought to be areas where gas has broken through the structure of the sediment to escape to the ocean [Wood et al., 2002]. One theory is that upward migration of fluid carries with it heat, preventing the methane from freezing as it travels through the nominal stability zone. The sediment surface of the world’s ocean has holes in it called pockmarks [Hill et al., 2004], interpreted to be what these gas explosions look like from the surface.
And there is the possibility of landslides. When hydrate melts and produces bubbles, there is an increase in volume. The idea is that the bubbles might lift the grains off of each other, destabilizing the sediment column. The largest submarine landslide known is off the coast of Norway, called Storegga [Bryn et al., 2005; Mienert et al., 2005]. The slide excavated on average the top 250 meters of sediment over a swath hundreds of kilometers wide, stretching half-way from Norway to Greenland. There have been comparable slides on the Norwegian margin every approximately 100 kyr, synchronous with the glacial cycles [Solheim et al., 2005]. The last one occurred 2-3 kyr years after the stability zone thinned due to increasing water temperature [Mienert et al., 2005], about 8150 years ago. The slide started at a few hundred meters water depth, just off the continental slope, where Mienert calculates the maximum change in HSZ. The Storegga slide area today contains methane clathrate deposits as indicated by a seismic BSR corresponding to the base of the HSZ at 200-300 meters, and pockmarks indicating gas expulsion from the sediment.
However, there is another also apparently plausible hypothesis for Storegga, which doesn’t involve hydrates at all. This is the rapid accumulation of glacial sediment shed by the Fennoscandian ice sheet [Bryn et al., 2005]. Rapid sediment loading traps pore water in the sediment column faster than it can be expelled by the increasing sediment load. At some point, the sediment column floats in its own porewater. This mechanism has the capacity to explain why the Norwegian continental margin, of all places in the world, should have landslides synchronous with climate change.
The Storegga slide generated a tsunami in what is now the United Kingdom, but it does not appear to have had any climate connections. It was not a catastrophic amount of methane loss. The volume of sediment moved was about 2500 km3. Assuming 1% hydrate by pore water volume were released on average from the slide volume, you get a methane release of about 0.8 Gton of C. Even if all of the hydrate made it to the atmosphere, it would have had a smaller climate impact than a volcanic eruption (I calculated the methane impact on the radiative budget here). Actually, the truth be told, the Storegga slide occurred spookily close in time to the 8.2k climate event, but there doesn’t appear to be any connection. The 8.2k event was a century-long cool interval, most probably in response to fresh-water release from Glacial Lake Aggasiz to the North Atlantic and was coincident with a ~75 ppbv drop in methane, not a rise.
Methane can leave the sediment in three possible forms: dissolved, bubbles, and hydrate. Dissolved methane is chemically unstable in the oxic water column of the ocean, but it has a lifetime of decades (shorter in high-flux environments) [Valentine et al., 2001], so if the methane is released shallow enough in the ocean, it has a good chance of escaping to the atmosphere. Bubbles of methane are typically only able to rise a few hundred meters before they dissolve. Hydrate floats in water just like regular ice floats in water, carrying methane to the atmosphere much more efficiently than bubbles [Brewer et al., 2002].
For most parts of the ocean, melting of hydrates is a slow process. It takes decades to centuries to warm up the water 1000 meters down in the ocean, and centuries more to diffuse that heat down into the sediment where the base of the stability zone is. The Arctic Ocean may be a special case, because of the shallower stability zone due to the colder water column, and because warming is expected to be more intense in high latitudes.
Permafrost. You’ve maybe read about permafrost in the paper a lot lately. Permafrost soils are defined as those which remain frozen year-round (actually, the technical definition is a soil which has been frozen for the last two years). There is sometimes a zone near the sediment surface that thaws in the summer. In the permafrost literature, this zone is called the active zone, and it has been observed to be getting larger with time [Sazonova et al., 2004]. Melting of surface soils is one reason why the high latitude Arctic is expected to be a part of the land surface that responds most dramatically to climate change [Bala et al., 2005]. The other reason is that temperature changes are more dramatic in high latitudes than the global average, especially high northern latitudes. There has been a stream of anecdotal reports of the effects of melting permafrosts on the Arctic landscape, tilted buildings and “drunken forests” near Fairbanks, for example [Pearce, 2005; Stockstad, 2004]. Much of the Alaskan oil pipeline is anchored in permafrost soils.
Hydrates are sometimes associated with permafrost deposits, but not too close to the soil surface, because of the requirement for high pressure. The other factor that determines whether you find hydrate is the permeability of the soils. Sometimes freezing, flowing groundwater creates a sealed ice layer in the soil, which can elevate the pressure in the pore space below. Hydrate in a one permafrost core [Dallimore and Collett, 1995] was reported below sealed ice layers. Lakes have been reported to suddenly drain away as some subsurface sealed ice layer is apparently breached.
The grand-daddy of subsurface sealed ice layers is a very large structure in Siberia called the ice complex [Hubberten and Romanovskii, 2001]. The most important means of eroding the ice complex is laterally, by a melt-erosion process called thermokarst erosion [Gavrilov et al., 2003]. The ice layer is exposed to the warming waters of the ocean. As the ice melts, the land collapses, exposing more ice. The northern coast of Siberia has been eroding for thousands of years, but rates are accelerating. Entire islands have disappeared in historical time [Romankevich, 1984]. Concentrations of dissolved methane on the Siberian shelf reached 25 times higher than atmospheric saturation, indicating escape of methane from coastal erosion into the atmosphere [Shakhova et al., 2005]. Total amounts of methane hydrate in permafrost soils are very poorly known, with estimates ranging from 7.5 to 400 Gton C (estimates compiled by [Gornitz and Fung, 1994]).
The Future. The juiciest disaster-movie scenario would be a release of enough methane to significantly change the atmospheric concentration, on a time scale that is fast compared with the lifetime of methane. This would generate a spike in methane concentration. For a scale of how much would be a large methane release, the amount of methane that would be required to equal the radiative forcing of doubled CO2 would be about ten times the present methane concentration. That would be disaster movie. Or, the difference between the worst case IPCC scenario and the best conceivable ‘alternative scenario’ by 2050 is only about 1 W/m2 mean radiative energy imbalance. A radiative forcing on that order from methane would probably make it impossible to remain below a ‘dangerous’ level of 2 deg above pre-industrial. I calculate here that it would take about 6 ppm of methane to get 1 W/m2 over present-day. A methane concentration of 6 ppm would be a disaster in the real world.
The atmosphere currently contains about 3.5 Gton C as methane. An instantaneous release of 10 Gton C would kick us up past 6 ppm. This is probably an order of magnitude larger than any of the catastrophes that anyone has proposed. Landslides release maybe a gigaton and pockmark explosions considerably less. Permafrost hydrates are melting, but no one thinks they are going to explode all at once.
There is an event documented in sediments from 55 million years ago called the Paleocene Eocene Thermal Maximum, during which (allegedly) several thousand Gton C of methane was released to the atmosphere and ocean, driving 5° C warming of the intermediate depth ocean. It is not easy to constrain how quickly things happen so long ago, but the best guess is that the methane was released over perhaps a thousand years, i.e. not catastrophically [Zachos et al., 2001; Schmidt and Shindell, 2003].
The other possibility for our future is an increase in the year-in, year-out chronic rate of methane emission to the atmosphere. The ongoing release of methane is what supplies, and determines the concentration of, the ongoing concentration of methane in the atmosphere. Double the source, and you’d double the concentration, more or less. (A little more, actually, because the methane lifetime increases.) The methane is oxidized to CO2, another greenhouse gas that accumulates for hundreds of thousands of years, same as fossil fuel CO2 does. Models of chronic methane release often show that the accumulating CO2 contributes as much to warming as does the transient methane concentration.
Anthropogenic methane sources, such as rice paddies, the fossil fuel industry, and livestock, have already more than doubled the methane concentration in the atmosphere from pre-industrial levels. Currently methane levels appear stable, but the reasons for this relatively recent phenomena are not yet clear. The amount of permafrost hydrate methane is not known very well, but it would not take too much methane, say 60 Gton C released over 100 years, to double atmospheric methane yet again. Peat deposits may be a comparable methane source to melting permafrost hydrate. When peat that has been frozen for thousands of years thaws, it still contains viable populations of methanotrophic bacteria [Rivkina et al., 2004] that begin to convert the peat into CO2 and CH4. It’s not too difficult to imagine 60 Gton C over 100 years from peat, either. Changes in methane production in existing wetlands and swamps due to changes in rainfall and temperature could also be important. Ocean hydrates have also been forecast to melt, but only slowly [Harvey and Huang, 1995]. Places to watch would seem to be the Arctic and the Gulf of Mexico.
So, in the end, not an obvious disaster-movie plot, but a potential positive feedback that could turn out to be the difference between success and failure in avoiding ‘dangerous’ anthropogenic climate change. That’s scary enough.
I have submitted a more detailed review of hydrates and climate change for peer review and publication, which can be accessed here.
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“Currently methane levels appear stable, but the reasons for this relatively recent phenomena are not yet clear.”
This is very much not-yet-clear. The levels have been rising for hundreds of years, so why stop now?–with things happening we would expect to maintain the increase?
How do we measure those levels? What are the known sources of error? Are other sources of error conceivable?
How does this stuff behave in the atmosphere? Why shouldn’t it separate from heavier gases and rise like water vapor–or does it? Could it be forming ‘clouds’ of tiny droplets at some high altitude, & could these escape notice somehow?
(I assume others are equally puzzled; what’s being considered?)
[Response:Methane is transient in the atmosphere, so if the anthropogenic source stays constant, the methane concentration stays constant. This is different from CO2, which accumulates. Methane is well-mixed in the troposphere. Gets oxidized by OH in the troposphere and zapped by UV light in the stratosphere. Gases don’t sink out very much in the atmosphere because it circulates so quickly. You can measure gravitational settling of gases in stagnant columns of air like in firn above ice cores, but in the atmosphere, gases don’t really settle out. The atmospheric measurements are straightforward, replicated, reliable.
No methane clouds on this planet. Not cold enough. What’s being considered? The thing to watch with methane is the concentration of OH radical in the atmosphere, which determine its lifetime before it gets oxidized in the troposphere. OH is like the flames of the fire of chemistry in the troposphere, and the intensity of this fire could be impacted by smog chemistry or by changes in methane emission.
David]
I just wanted to mention that a number of the presentations at AGU pointed to evidence that the Paleocene-Eocene Thermal Maximum was inconsistent with a large clathrate release.
They preferred the explanation that a large igneous province intruded on a large coal formation to produce CO2 and methane (e.g. Svenson et al. (2004) Nature 429, pp 542). As the PETM has been the best case for catastrophic clathrate release in the last 70 million years, it would be somewhat comforting if the community ultimately decides that this event was caused by something other than clathrates. (On the theory that if it hasn’t happened in the past, it probably isn’t going to happen today.)
[Response:I’m skeptical about methane for the PETM myself, in that the temperature change and pH change seems to require more CO2 than the isotope spike will give you, if it’s methane. Maybe I shoulda mentioned that. David]
I’m looking forward to have this discussion during the next AGU meeting in Baltimore, 23-26 May 2005, during the session “Climate and Clathrate”.
Personally I think that there may be another mechanism tied to clathrate that overwhelms the other and also put all the pieces of the puzzle together.
I haven’t read much on methane hydrates. When there is an ice age, and sea levels drop globally, is it possible for methane to get released? As there is no signal that methane increases during glaciation (I assume), I guess this doesn’t happen in a big way … but why not?
Similarly, there’s the isostatic rebound following deglaciation. Perhaps destabilisation of the hydrates is less likely in this situation because the emerging land is only in cold locations. Still, the thermal regimes of these hydrates must change quite a bit in predictable ways and places sometimes, and I’m curious that your post doesn’t refer to some of these instances that I would have thought to be informative. Thanks for explanations/links.
[Response:Turns out that hydrate preservation is much more sensitive to changes in temperature than it is changes in pressure, so what we might look for is release of methane during deglaciation. The carbon-13 signal is also driven by changes in organic carbon (trees and soil carbon), such that if there were more methane degassing during deglaciation, there would have to be more terrestrial biosphere uptake. Mark Maslin has a paper about this. David]
There seems to be enough known on this subject to take it quite seriously — more that was known about WMDs in Iraq before the invasion. So I would think we should be spending an equal amount of what we’re spending on Iraq to reduce our GHGs so as to avert releasing those various frozen methane sources, if not simply to reduce GW in general with all its more certain horrible consequences (without considering positive feedback scenarios involving frozen methane).
One question: What about the end-Permian extinction of 251 mya? Could melting methane clathrates have played an important role in increasing the GW (as I read in M. Benton’s book, WHEN LIFE NEARLY DIED)? My understanding is that the atmosphere warmed by about 6 degrees C from our current level, and that triggered increasing releases of methane from clathrates in a positive feedback fashion over thousands of years (or was it millions of years??).
Also, does the fact that we’re warming the atmosphere faster than other times in the past mean things might happen somewhat faster? Or add other unknowns?
[Response:I think the question of the end Permian is still up for grabs. The Cretaceous was an impact, the Paleocene Eocene was the 13-C spike attributed by some to methane, the end Permian is still open. David]
People from time to time mention mining the ocean-floor hydrate for a source of hydrocarbons to replace depleting oil and natural gas (the latter depleting in the US, anyway). I’m curious if you’ve considered the feasibility and risks of such mining?
[Response:I’ve got a section on this, plus references, in the review paper I posted above. The stratigraphic type hydrates, which is most of them, are the least minable, because they’re dilute. It’s easier if the sediment is permiable, like in Nankia Trough sediments near Japan, than if they’re not, like the Blake Ridge. Permafrost has already been drilled for hydrate methane, at a site called Messoyakha, and a more recent test hole called Mallik. By analogy of the development of coal-bed methane, hydrates could supply order 10% of our production in order 10 years, is what I’ve read. David]
I have to say that I’m rather unimpressed with what I’ve heard in the way of excuses in relation to the growing discrepancy between SRES-type projections and actual measurements of atmospheric CH4 (it came up a couple of weeks ago in a workshop here). IMO this is developing into quite a credibility gap and I hope that there will soon be a better answer than “we don’t know, so we’ll just keep using the old scenarios even though they all already show a substantial overestimate within 5 years of being published”.
I don’t know if this factor is anywhere close to being a large enough effect to be relevant, but one might expect that the activity of methane-oxidising bacteria in the soil will increase as concentrations of their foodstock grows, other things being equal (here’s a random ref from google). What ideas have the scientists working in this area come up with?
[Response: The problem with methane concentration projections is that they are not solely related to anthropogenic CH4 emissions. The methane sink is affected by ozone precursors (VOCs and NOx) as well as directly by climate (humidity and temperature) (in addition to the soil sink feedback you mention), while the sources are also affected by climate – wetland emissions are affected by wetland extent, water tables and temperature, while hydrates (as seen above) are a big unknown. Of course, VOCs and NOx also have potential climate influences on their sources too. We are a long way from being able to take the anthropogenic CH4 emissions scenarios and being able to produce consistent concentration projections (because of course it will depend on the climate, which will depend on the CO2 emissions and other forcings as well). This would involve running multiple multi-century coupled chemistry-climate OAGCMs which are at present unfeasible. So the only sensible choice is to do a range of scenarios – and as I have said in a previous thread, no group is restricted to the SRES scenarios – for instance we have used ‘alternative’ scenarios where methane declines over the next 50 years. The benefits of the SRES scenarios are of course that the different groups all do the same thing, so that intermodel comparisons can be consistent, and this is important for IPCC-type assessments, but that is not the only science worth doing. – gavin]
r.e.#3
Andre, if I were you I’d avoid trying to tell everyone at AGU that the Younger Dryas wasn’t at all cold. Could be quite embarrasing.
“The juiciest disaster-movie scenario would be a release of enough methane to significantly change the atmospheric concentration, on a time scale that is fast compared with the lifetime of methane…”
Screenwriters looking for a leg up should find John Barnes’ 1994 SF novel Mother of Storms, which posits such a release of sea-floor hydrates. That leads to elevated sea-surface temperatures over very long reaches, which leads to 500-mph hurricanes (never mind yer Navier-Stokes, killjoys) which leads to Florida being scrubbed down to coquina and karst… for starters…
[Response:This was a colorful book, to be sure… David]
If you want disaster movie scenarios I read one version of what might have happened at the Permian extinction that was truly apocalyptic. It started with a buildup of methane on the bottom of large, shallow, stagnant oceans. Then a lake Nyos type event where the the water got overturned and the suddenly supersaturated water formed mathane bubbles, driving further circulation and methane release in a chain reaction. The amount of gas released would be enough to cause a shock wave propagating outwards with increasing velocity and pressure until it reached ignition temperature, and then hell would break loose more or less literary. I don’t know if this is any more realistic than the supersonic storms in Mother of Storms but it is spectacular. (Anyone who likes that book migh consider reading David Brin’s Earth as well. they are similar in style although Brin uses a little black hole falling into the Earth to create the required disasters)
[Response:There have also been proposals of CO2 Lake-Nyos events from the ocean. I for one am skeptical that the ocean could be that stagnant for long enough to make this happen. David]
hello David
I’ll already asked you few months ago, about the sensitivity of methanes clathrates in Arctic zone.
Do you know the total amount (expressed in CH4), and the depth of these arctic chlathrates?
Do you think it’s possible to reach rapidly (in few decades) the 6ppm concentration only with a destabilization in this shalow oceanic zone?
[Response:I’ve tried to answer this question to the best of my knowledge. There are tens or hundreds of Gtons of carbon in permafrost hydrates, but the amount is not very well known. Raising the methane concentration significantly seems like it could be possible, but is difficult to predict precisely. David. ]
When Methane decomposes in the atmosphere, does it absorb oxygen in significant quantities? Peter Ward has a theory that the Permian extinction may have been exacerbated by methane releases coupled with plummeting oxygen levels that further reduced the ability of animals to cope. This ultimately made conditions ripe for dinosaurs, which can function in low oxygen levels much better than the proto-mammals that were predominant at the time.
[Response:The amount of oxygen in the atmosphere is huge, enough to oxidize 400,000 Gton of C in methane. If we start running out of oxygen, that is the least of our problems. I think Peter Ward’s theory probably has O2 sinking for other reasons, an imbalance of the burial and weathering of organic carbon over geologic time for example. Our understanding of the stability of atmospheric oxygen is somewhat rudimentary, I feel. David]
Re #13 – I heard somewhere that during the methane burp at the PETM the mammals all shrank in size due to the lack of oxygen. I have never seen any confirmation of this though. I would be interested if anyone knows of a reliable source for this story.
[Response:Even if it were 5000 Gton of methane, that would only cut O2 down by about 1% (from 20% to 19.8%). That would be the same as going up in altitude about 100 meters. David ]
Gavin’s response (#8) seems a little disingenuous to me. Just saying that no-one is forced to use the SRES ignores the substantial influence that the IPCC has over the international research program. It also presents an open goal for critics of the IPCC process to shoot at. At the level of an individual researcher, I (and others like me) have the option of simply using the SRES and knowing no-one will bat an eyelid at my choice, or trying to find/create credible alternative scenarios, which is far outside my area of competence and will risk adverse comment from referees. Model-model intercomparisons are all well and good, but these projections are routinely presented as realistic forecasts of the Earth’s future climate, and I’m sure we’d all agree that it is the model-reality comparison that really matters!
It will certainly be interesting to see how the AR4 addresses this issue.
[Response: Well I’m not trying to be disingenuous, and I’m not saying that everyone should build their own scenario, alternatives to SRES already exist. However, the real question is what is the scientific point you are trying to address? Since accurate prediction of all the forcing factors is beyond us, the only option is to use a range of scenarios that will hopefully bracket the real course of events. I think we agree that discussion of such projections as if they were precise forecasts for 2080 etc. is a mistake, but it is one that is relatively easy to make – especially by the time the result gets encapsulated in a press release. -gavin]
Gavin,
The point is simply that the SRES scenarios already do not appear to “bracket the real course of events” at least in respect of CH4, and some of the scenarios that are routinely used seem to be diverging rather strongly from reality, especially considering that they are only 5 years old. I would agree that the overall bias isn’t huge (in terms of resulting AGW) but I think it would be better for a number of reasons to deal with the problem rather than try to excuse it. If there are strong arguments in favour of the existing scenarios (other than inertia and convenience), I’ve yet to hear them.
But having made my point, I probably shouldn’t hijack this interesting post about methane hydrates any further – I guess we should try to work out how to extract and burn them to avert the
peak oil crisisrisk of release :-)Re: Oxygen
One major issue with oxygen in the atmosphere is that it is apparently more geological than biological – the net effect of biological processes is (over geological timescales) essentially zero. Oxygen is produced on a net basis by photodissociation of water in the upper atmosphere coupled with hydrogen loss. (Methane also breaks down with a net oxidising effect).
This is balanced over time by the uptake of oxygen at mid ocean ridges, oxidising Fe2+ to Fe3+, and the release of reduced carbon species from the same; it appears that around 2.5 billion years ago, this process sufficiently oxidised the mantle to that carbon dioxide became the dominant volcanic carbon species, thus reducing O2 drawdown and hence allowing atmospheric oxygen accumulation. The equlibrium between drawdown and production hence defines oxygen concentrations.
This oxidation process has also gone to completion on Venus and Mars, which are both highly oxidising at the surface – however, in both cases the lack of water to break down means no free oxygen; without a continuous source, even very slow geological processes will draw down all free oxygen. CO2 photolysis in both cases provides a low level of free O2, but in this case there is no overall effect.
http://www.grisda.org/origins/03066.htm
http://astrobiology.arc.nasa.gov/workshops/1996/palebluedot/abstracts/allen_01.html
Re #17 — note that oxygen from biological sources accumulates when dead biomass is buried in sediments. That’s been the major mode of oxygen accumulation, as I understand it.
[Response:This is my understanding too. The atmosphere was essentially anoxic until oxygenic photosynthesis followed by organic carbon burial in sediments produced enough O2 to oxidize the Fe2+ in the ocean to Fe oxides (banded iron formations), plus oxidize sulfur to dissolved sulfate in the oceans. The amount of buried reduced biologenic carbon is enough to generate the O2 in the atmosphere 50 times over. David. ]
Re #16, I’m not sure what you’re saying, James? Are you saying the upper level projections of TAR may be too low, because they don’t take everything into consideration? That’s sort of what I think, since as a layperson I’m into “expect the worst (& try to avert it), and hope for the best.” Also, each succeeding IPCC report seems to indicate worse things (at least more certain things) re GHGs & GW, so according to that trend, I expect the next report to indicate even worse things (and/or more certain things) than TAR. Too bad we couldn’t have had the Fourth report back in 1990 to jump start some action on mitigating GW.
I’ve been thinking about the PRO-CON FORMAT the media use (which has been discussed earlier), and now think that the format itself is not as bad as the fact that the media have limited the debate between contrarians (who need 99%, perhaps 101% certainty on AGW) and scientists (who require 95% certainty, and even with that, bring all their caveats on screen – as if the scientific devil’s adocates were there with them on TV).
The pro-con format should really be between the scientists (seeking to avoiding the false positive) and the environmentalists/victims (seeking to avoid the false negative) — or at least all 3 (contrarians, scientists, environmentalists/victims). That’s where the media have failed us miserably, and have forced some conscientious scientists to sort of play the role of environmentalist/victim — for which they get roundly thrashed.
Re #14 …”PETM the mammals all shrank in size”…
(but not due to the lack of oxygen)…
An article called “Methane and Mini-horses”… (Feb 16, 2003) discusses PETM dwarfing due to high CO2 and less
…[To understand why dwarf versions of the various animals appeared and then disappeared from the fossil record, Gingerich turned to colleagues at the University of Michigan Biological Station who are studying the effects of elevated carbon dioxide levels— associated with global warming—on plant growth.
“They find that if you grow plants in a carbon dioxide-rich atmosphere,the plants love it. They grow fast. It’s easy for them.” But in the process, the plants incorporate less protein and more defensive compounds than they normally would. Insects that eat these plants grow more slowly, and the same might be true of mammals, Gingerich reasoned.
Furthermore, “the reproductive cycles of mammals that live in seasonal environments are tuned to seasonal cycles,” Gingerich said “If an animal has a one- or two-year period in which to grow to maturity and reproduce, and it’s trying to do that on a diet that’s difficult to digest and not very nutritious, it’s not surprising that it would evolve to be smaller.]
Philip D. Gingerich, professor of geological sciences at the U. of MI
William C. Clyde of the University of New Hampshire and
Scott L. Wing and Guy J. Harrington of the Smithsonian Institution,
http://groups.yahoo.com/group/Paleontology_and_Climate/message/13552
Re #2 and #4
Robert Speijer website…
“A relative sea-level fall (~30 m) immediately preceded the late Paleocene thermal maximum, during which sea-level rose again by ~20 m. This rise may have been eustatically controlled, possibly through a combination of thermal expansion of the oceanic water column and melting of unknown sources of high-altitude or polar ice caps in response to global warming.”
http://www.palmod.uni-bremen.de/FB5/geochron/Robert/RPSabstr.html
[…
* Salinity in the sea fell sharply during the Permian for the first
time, changing oceanic physics to make deep water circulation more
difficult.
* The atmosphere went from very high oxygen content (30%) to very
low (15%) during the Permian.
*
* The evidence shows global warming AND glaciations near the P-Tr.
…]
http://geology.about.com/od/extinction/a/aa_permotrias.htm?nl=1
======
Apparently there were sharp falls in sea level which preceded both the PETM and end of Permian warming.
Clarifaction re #21
The end of Permian reference describes a sharp fall in salinity (not sharp fall in sea level). At the end of Permian there was a large change from cold to warm, but no reference indicating a sharp drop in sea level before the warmth, that I know of.
Re #2
A 25 Nov 2005 article in Science, The Phanerozoic Record of Global Sea-Level Change (Miller, K.G. et. al.): “We propose that the early Eocene peak in global warmth and sea level (Fig. 3) was due not only to slightly higher ocean-crust production but also to a late Paleocene-early Eocene tectonic reorganization. The largest change in ridge length of the past 100 My occurred ~60 to 50 Ma (57), associated with the opening of the Norwegian-Greenland Sea, a significant global reorganization of spreading ridges, and extrusion of 1 to 2 x 10’6 km’3 of basalts or the Brito-Arctic province(58). A late Paleocene to early Eocene sea level rise coincides with this ridge-length increase, suggesting a causal relation. We suggest that this reorganization also increased CO2 outgassing and caused global warming to an early Eocene maximum”. …
Lynn (#19),
No, I’m not suggesting that the upper projections are too low – quite the reverse. That’s not to say that the consequences of a more mainstream projection are not likely to be significant. This is a nice article by James Hansen:
(I think the sea level stuff in his article may be slightly misleading – the 25m rise would surely be a much slower process than the juxtaposed “Within a century…” might be taken to imply.)
Re #22
… “There is a possible connection between falling seas and mass killings on land, however, as Paul Wignall, a paleontologist at the University of Leeds, England, has pointed out in connection with the end-Permian extinction”.
The Sixth Extinction. Richard Leakey an Roger Lewin (1995) p 49.
Notes Ch 4 #8. Paul Wignall, “The day the world nearly died”,
New Scientist, 25 January 1992, p. 55.
Re #25
The most obvious cause of low sea levels and a land mass extinction would be a meteorite impact in the oceans. The resulting tsunami would wipe out the land animals, and fill depressions and soak deserts leading to a fall in sea level. Any impact crater on the sea floor would eventually be removed from the record by subduction. That explains why, when there must have been three times more impacts in the oceans than on land, since their area is three times larger, only the land impacts are preserved.
Many of the links in the “other opinions” section of this website are highly ideological and mostly leftist. What does atheism have to do with science or global warming? A psychological fixation on materialism isn’t scientific. Also an excess of crude sentimentalism about the future is a motivating factor for the leftist attraction to climate change research. These are facts that lend some credence to skeptics of certain claims made by so called researchers.
[Response:My post was about methane hydrates. If you have a science question, I’ll try to answer it. David.]
re #27
A graph at the Museum of Natural History in Denver, photo at:
http://groups.yahoo.com/group/Paleontology_and_Climate_Articles/
shows that global CO2 and temperature were low for 10s of million of years before the end-Permian.
Miller, K.G. et. al. (in #23) says: “Sea-level changes on very long time scales (250 My) are related to the assembly and breakup of supercontinents”. …
Payne J.L. suggests the Siberian Traps for the prolonged instability in the carbon cycle. The longer time scale of excursions suggests a cause other than bolide impact.
I’m thinking that the extensive volcanism might have caused some intial drops in sea level by dust shading the sun. We know that scientists have determined even tiny Mt. P in the early 1990s had cooling global effects for a couple years. Although the Siberian Traps was basalt flooding, other volcanic activity occurring throughout the world as the continents were pushing together probably put a lot of dust in the atmosphere, off and on.
*Payne J.L. et. al. “Large Perturbations of the Carbon Cycle During Recovery from the End-Permian Extinction” 23 July 2004 Science.
>[Response:… Methane is well-mixed in the troposphere. Gets
>oxidized by OH in the troposphere and zapped by UV light in the
>stratosphere.
So if the input of methane and the production of OH radicals (Where do these come from, anyway?) both increase, the result could be steady methane levels(?)
How rapid is the stratosphere breakdown, & how much influenced by the ozone also being produced by that UV?
[Response:OH come from ozone, zapped by UV to make O radical, which reacts with water to make OH. There’s not much OH in the stratosphere because there’s not much water. I don’t know the relative rates of stratospheric UV methane degradation versus tropospheric, but I believe that tropospheric is most of it. David ]
> Gases don’t sink out very much in the atmosphere because it
> circulates so quickly.
I remember reading that temperature differences drive a lot of that circulation, but what about the lightness of water vapor in moist air? CH4 is equally light as a molecule, not normally concentrated enough to significantly lighten the air that contains it–but if anything makes for quick local releases, could these be concentrated enough to make their own brief updraft? Since it isn’t cold enough here to form methane clouds, could a concentrated local “puff” of this stuff get up to heights where it would break down faster than the ~10 years it would take to oxize here?
[Response:I think even water vapor is a small component of the density differences in the atmosphere, and methane is much lower concentration. We are talking about a buoyant gas dragging parcels of air around, now, instead of (what I understood) your original thought was the gases separating themselves by unmixing. About the fate of a large parcel of methane, I can’t help much. I don’t know how big a puff it would have to be; pretty big I would magine. ]
Or could there be areosols greasy enough to be absorbing a significant amount?
>The thing to watch with methane is the concentration of OH radical
>in the atmosphere, which determine its lifetime before it gets
>oxidized in the troposphere. OH is like the flames of the fire of
>chemistry in the troposphere, and the intensity of this fire could
>be impacted by smog chemistry or by changes in methane emission.
More on this?
[Response:I’d recommend Daniel Jacob’s book on atmospheric chemistry, if you’re serious. I was just referring to the same ideas that Gavin wrote in response to a comment above. David]
Re #27, Feldon, you’re not one of those Exxon-paid inflitraters, are you? The ones I’ve been reading about, who go around GW blog pages writing bad things about the environmentalist/victim point of view, and knocking mainstream science on GW? The reason I ask is I’m doing an anthropological study on various stances on GW, including the contrarian view. Since the ultimate forcings of AGW are people, we need to understand the human dimension, which would include considerations of the cultural/ideological, social, psychological (cognitive & affective) aspects of human behavior.
So, if you could tell me a bit about yourself and why you are opposed to believing in AGW (if you are). That would help in my study.
BTW, I’m one of the more extremist on this site. However, I’m not at all materialistic or atheistic. Aside from being an anthropologist, I’m a very religious person, a lay Carmelite (OCDS) who has dedicated my life to prayer and service, a strong believer in God and morality. Not only do I worry about lives that may be lost to GW, but also about all those souls who will end up in a lot hotter place than a globally warmed world, because they refuse to mitigate GW. It seems you’re a religious person, too. So, we have work to do, friend. Saving lives AND saving souls. Are you with me?
I’m a french lecturer in Bordeaux 4 university (France). I have writen a book on the topic(methane and global warming). In french, sorry :
“Terre, fin de partie ? La derive climatique, un risque majeur”.
You’ll find it there :
http://www.eons.fr//main.php?rubrique=Catalogue&idlivre=38
I think the methane peril has been underestimated or neglected by IPCC (3rd report)and numerous anthropic GH gas specialists.
Alain Coustou
[Response:I am ashamed to admit that I cannot read French, but I would be very interested in your ideas, if you would be willing to summarize them. David. ]
Here in Oregon we are the somewhat unwitting hosts of a great deal of methane hydrate research by Oregon State University, some Texas university people (and backing by the good old Houston-based gas industry), of deposits on and near the ocean floor on the Gorda Ridge just off our coast, which is a consequence of the subduction zone geomorphology of the area. See OSU’s web page here, for example. While the researchers have various interests, the involvement of the industry is basically a long-term high-risk research program for potential future hydrate commercialization. I am not qualified to pass judgment on the quality or direction of the research, but presumably it is yielding useful information for assessing the impact hydrates may have at present and in the future on climate change.
[Response:Hydrate Ridge is the name of the place off of Oregon. It’s perhaps the most-studied example of a place where methane moves around in the sediment. Good science. I’m not surprised or shocked or even dismayed that the oil companies are funding this. I’ve gotten funding (not a lot) from the Petroleum Research Fund, to model the long-term lifetime of CO2 in the atmosphere, not at all an Exxon company objective. As far as I have experienced, PRF funds science that has to do very broadly with fossil fuels, without any strings. David. ]
I’ve a question for you folks, though it is perhaps more involved with biology than what you normally consider.
There are organisms (worms, plants), an ecosystem which exploits methane hydrates in the ocean as the basis of their ecology.
There is a sink for methane hydrates. You have the source (decomposition of organic matter) mentioned.
My question is this: we have organisms that exploit methane hydrates. Why do we have vast quantities of methane hydrates in the ocean at all? With a sink available shouldn’t the hydrates have been consumed long ago?
This has puzzled me for a while, and if anyone has any ideas please expound.
[Response:There are bacteria which, if there is some energetically favorable chemical reaction possible, can harvest energy from that reaction. I don’t know for sure but I wouldn’t be surprised if bacteria harvest energy from the reaction of methane and sulfate, for example, or methane and oxygen in the ocean if the two coexist. At hydrothermal vents, anoxic water containing reduced compounds like methane or sulfide mix with oxic seawater and the bacterial harvest energy. The bacterial in turn are eaten by the tubeworms and giant clams and other exotic life forms that are found around these vents. Down where the hydrates are, there is neither sulfate nor oxygen, so there’s no way for bacteria to make a living feeding on the methane. In fact, bacteria here get energy by producing methane from organic matter. So I think the answer to your question is that the rate of methane degradation that biology can mediate is ultimately limited by the availability of the reaction partners, sulfate or oxygen. It would be like us trying to eat lunch without breathing. David. ]
Saturated hydrocarbons such as methane are about the worst possible food sources you could imagine from the thermodynamic standpoint. For one thing to start the reaction you have to bust a C-H bond rather than do something clever such as insert into a double bond, etc
Just as an addition.
Organisms have been found which do exploit methane hydrates as the basis of their ecology.
Do a google on ‘methane hydrates worms.’
That said, I’m no biologist nor chemist.
Hopefully I haven’t misinterpreted you two (as to being aware of their existence), but these organisms are fact, not speculation.
It may as David speculated they need oxygen or sulfates in an area to be viable, and are thus unable to exploit all the methane hydrates on the sea bed. Certainly a topic worthy of study.
Regarding the reference to “methanotrophic bacteria”, it is important to understand the difference between Methanotrophic bacteria and methanogenic bacteria. Methanotrophs use oxygen to oxidize methane into carbon dioxide (CO2). Methanotrophic bacterial systems have received a great deal of attention over the last ten years since it has been found that methane mono oxygenase (the enzyme generated by Methanotrophs to react with methane) can degrade a wide variety of chlorinated hydrocarbons. The process is known as co-metabolism and is definitely an aerobic process.
Methanogenesis is the process of degrading hydrocarbons with the end product being methane (CH4) gas and carbon dioxide.
The general reaction is as follows:
2Corganic + 2H2O = CO2 + CH4
This is a strictly anaerobic process, methanogenic bacteria are poisoned by the presence of oxygen at levels as low as 0.18 mg/L of soluble oxygen (as O2).
As an aside, methanogenic bacteria are one of the three classes of bacteria termed Archaebacteria, which are representative of organisms that first appeared on Earth some 3.5 billion years ago.
While their activity is inhibited by oxygen, these bacteria are robust enough to appear in a wide variety of natural locations such as: the intestinal tracts of ruminant mammals (cows etc.), sewage digesters, groundwater and soil.
The precise mechanisms of hydrocarbon degradation under methanogenic conditions is not entirely understood by current researchers. Theoretically, methanogenic reactions only involve chemicals containing one or two carbons. More complex hydrocarbons are degraded through the synergistic activity of other bacteria that may utilize by products (such as hydrogen) of the methanogenic process. Definitive illumination of these processes has not occurred in the laboratory, as it takes rigorous physical controls as well as a great deal of skill to culture these bacteria. To date no one has been able to grow (in the lab) a complete consortia of degrading anaerobes as conjectured above.
On methane hydrates and the PETM. I find the idea for coal being the source of the carbon signal interesting. Nothing excludes a mixture of hydrate and coal release. Whatever fits the pH, Temperature, and isotope signatures the best. Of course it doesn’t matter in a way. Moving large amounts of carbon from any source into the atmosphere on short time scales is foolish. Thanks for the interesting idea.
what happens when ch4 methane reacts with oxygen?
when an organic compound methane reacts with oxygen they produces carbon dia oxyide and the hydrogen gas which is harmful for humman biengs carbon dia oxyide is used in our drinks like pepsi and it is soulible in water at heavey pressure and hydrogen is used as fuel and the equatoin becomes
ch4+h2—–>co2+2h2
[Response:When methane is combusted, or if it reacts with oxygen in the atmosphere (a very slow type of combustion) the hydrogen in it produces water vapor, rather than hydrogen. David]
> ch4+h2—–>co2+2h2
No, that’s not possible in chemistry, it’d be magic —
left side —–> right side
4 carbons plus 2 hydrogens —–> one carbon, 2 oxygens, 4 hydrogens
Doesn’t balance — it’s transmutation, or alchemy. It doesn’t happen normally.
What normally happens? Let me see what I remember from 1967 chemistry class:
Combustion of methane in oxygen is:
some CH4 ( some carbon and hydrogen) plus some O2(oxygen molecule)
—->
some CO2 ( some carbon and oxygens) plus some H20 (hydrogen and oxygen)
The atoms come as _molecules_ — that limits how many of each element you can have on either side, and they have to come out right on either side of the arrow. Here it’d be:
Methane reacts with oxygen:
two methane molecules — that’s 2(CH4)
which is: two carbon atoms and eight hydrogen atoms
+
four oxygen molecules — that’s 4(O2)
which is eight oxygen atoms
2(CH4) …… + 4(O2) …… –> 2(CO2) ….. +…. 4(H2O)
two carbon……+eight oxygen –> two carbon…+ eight hydrogen
eight hydrogen………………………four oxygen…..four oxygen
or
2 carbon, 8 hydrogen, 8 oxygen –> the same, rearranged
Same number of atoms on left and right sides of the arrow, of each kind. You have to remember to count atoms, AND to count molecules, and know what goes together (or test and find out by trying).
The forum osftware doesn’t like ASCII art, it drops spaces so I tried filling in with dots. Sorry if it’s not clear.
This is NOT easy to understand, and more than a few hundred years ago, nobody in the whole world understood this sort of chemistry at all.
It’s not surprising we are still explaining it, or trying to!