Yes, really helpful to understanding. Thanks to all -- mostly Alvia I think it is Re [[somewhere down this message, not quite sure who said what]]
""> Volcanic SO2 is so efficient at cooling the earth because it reaches a > layer > in the stratosphere with primarily horizontal winds that spread it > efficiently around the globe. The elevation of that layer is set by the > thermal and chemical structure of the stratosphere. If anthropogenic SO2 > was > not delivered to that specific layer, it would not be spread efficiently > around the earth and thus would not have the same cooling effect."" Does this mean that SO2 injected over the Arctic at a different height would not be spread all over the planet? Or to a lesser degree ?? As what we want to cool most urgently IS the Arctic would it not be best to inject the SO2 at an altitude where it mostly stays over the Arctic ? Or would its cooling effect saturate in some way so that 2 x as much SO2 over the arctic yields only [say] 1.5 x as much cooling over the Arctic? And if it spread to a lesser extent, would the undesirable tele-climatic effects (prejudicing tropical monsoons) be reduced ??? Peter ----- Original Message ----- From: "Alvia Gaskill" <[email protected]> To: <[email protected]>; <[email protected]> Cc: <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]> Sent: Tuesday, September 22, 2009 8:18 AM Subject: [geo] Re: Cooling the earth with SO2 > Still researching the question of how much water is required to form the > aerosol, the attached recent paper does disclose that Pinatubo added > around > 100-150Mt of water to the stratosphere, most of which came from the magma > and about 10% from the troposphere itself > http://www.geo.mtu.edu/~raman/Ashfall/Syllabus/Entries/2009/6/21_Formation_of_Ash_files/DartevelleGeo.pdf > > "Previous studies have suggested possible inventories of stratospheric > water > vapour (hence SWV) resulting from volcanic eruptions; between 10 Mt from > magma (Pitari and Mancini, 2002) to 540 Mt from magma and entrainment into > the Plinian column from the atmosphere (Dartevelle et al., 2002) from > Pinatubo's eruption in 1991. However, satellite observations of SWV in the > months following the eruption imply a maximum value of 100-150 Mt up to > that > time (Nedoluha et al., 1998). Estimates from other volcanic eruptions are > ~2 > Gt following Tambora in 1816 (Glaze et al., 1997) and ~27 Gt from the 76 > kya > Toba eruption (Bekki et al., 1996), both from estimates of water in the > magma. The mechanism of sea-water entrainment into the plume (described > above) could potentially significantly add to the amounts of water vapour > injected into the stratosphere depending on the vicinity of the volcano to > bodies of water. SWV can have significant climatic effects; the radiative > forcing due to SWV increases of O (1) ppm in the 20th century have been > modelled as being up to +0.5Wm?2 (e.g. Forster and Shine, 2002). A water > vapour anomaly of 0.95 ppmm, or ~1.5 ppmv in the stratosphere is > equivalent > to a total mass of water of 500 Mt, which is entirely consistent with the > inventories described above. The partial cancellation of volcanic cooling > by > direct injection of water into the stratosphere is therefore entirely > plausible. Moreover, a humidity anomaly in the tropical lower stratosphere > is distributed around the stratosphere by atmospheric motions, eventually > dissipating on a timescale of 5-10 years (Hall and Waugh, 1997). By > comparision, micron-sized sulphate aerosol droplets particles fall out of > the stratosphere on a timescale of 2-3 years; the water vapour anomaly > therefore outlasts the volcanic aerosol loading by some years." > > However, Bekki, S. (1995), Oxidation of volcanic SO2: A sink for > stratospheric OH and H2O, Geophys. Res. Lett., 22(8), 913-916 states that: > > "Oxidation of volcanic SO2: A sink for stratospheric OH and H2O > S. Bekki > > Centre for Atmospheric Science, Department of Chemistry, University of > Cambridge, Cambridge, England > > The oxidation of volcanic SO2 to sulphate in the stratosphere is > investigated for an anomalously large volcanic sulphur loading (~200 Mt) > similar to that generated by the Tambora eruption in 1815. Model > calculations suggest that stratospheric OH levels can be severely reduced > by > the gas-phase oxidation of SO2. One implication of this is that dense > volcanic SO2 clouds may last substantially longer than previously thought. > SO2 oxidation is also found to lead to significant stratospheric > dehydration > because approximatively three molecules of H2O are consumed for each > molecule of SO2 converted to sulphate. Therefore it is possible to view > major volcanic eruptions as a potential sink for stratospheric H2O." > > And existing stratospheric water vapor would be used in forming aerosol: > > http://www.unep.org/Ozone/pdfs/Scientific_assess_depletion/07-Chapter2.pdf > > "Questions have also been raised whether a sufficiently large volcanic > injection could also affect the HOx cycle in the stratosphere. From > simple > consideration of stoichiometry, it can be assumed that one molecule of H2O > is produced per H2S oxidized. For SO2, it is assumed that no net gain or > loss of HOx results from SO2 oxidation (Read et al., 1993; McKeen et al., > 1984). Finally, approximately three molecules of H2O are needed to oxidize > SO2 and condense sulfuric acid to sulfate aerosols (Bekki, 1995). Two > dimensional model simulations (Bekki et al., 1996) showed that a > hypothetical injection of 6000 Tg SO2 could dehydrate the stratosphere. > Given that most large eruptions inject about several tens of teragrams of > sulfur, this effect is probably not important under most conditions." > > This suggests that existing stratospheric water vapor is sufficient to > produce the aerosol. So it still seems that water vapor is not an issue > with regard to formation of a man-made aerosol. I suppose we could try > this > in a vacuum chamber with stratospheric levels of water vapor to see what > would occur. Since the final product, H2SO4/H20 contains 2 molecules of > water plus the one used in oxidation, I think we actually were in > agreement. > But since a mole of water weighs 18g and a mole of H2SO4 98g, much less > water would be required than if the weights per mole were the same. > Basing > this on SO2, 54 g of water would be required to convert 64g of SO2, about > a > 1:1 basis or for 12Mt of SO2, about 10Mt of water, what I estimated > previously. There doesn't seem to be any impact on OH unless a > supervolcano > is involved. > > ----- Original Message ----- > From: "Andrew Lockley" <[email protected]> > To: <[email protected]> > Cc: <[email protected]>; <[email protected]>; > <[email protected]>; <[email protected]> > Sent: Monday, September 21, 2009 1:00 PM > Subject: [geo] Re: Cooling the earth with SO2 > > > > Very informative, thanks. > > I understand that OH radicals may be under significant pressure in the > atmosphere, and that their loss may have significant consequences. > I've not seen the consumption of OH raised as an issue here before. > Is it important, or not? I have no idea how much OH there is, and how > much might be used up by geoengineering. Could more be made if we > needed it? > > A > > 2009/9/19 <[email protected]>: >> Well it is not quite so easy. >> >> Volcanic SO2 is so efficient at cooling the earth because it reaches a >> layer >> in the stratosphere with primarily horizontal winds that spread it >> efficiently around the globe. The elevation of that layer is set by the >> thermal and chemical structure of the stratosphere. If anthropogenic SO2 >> was >> not delivered to that specific layer, it would not be spread efficiently >> around the earth and thus would not have the same cooling effect. >> >> Yes it does take 3 times as much water as SO2 to create the sulfuric acid >> aerosol. Pinatubo ejected 15 to 19 Mt of SO2, thus if we mix 3 times as >> much >> water,we must eject approximately 75 to 95 Mt of material, a significant >> effort. We do not know how much of the volcanic SO2 was needed to form >> the >> aerosol, but there are good estimates from satellites for the volume of >> aerosol produced and my recollection is that a significant amount of SO2 >> somehow made it to this thermal layer. I am traveling right now and not >> in >> a >> position to look up the details. >> >> The well observed destruction of ozone by the Pinatubo eruption may have >> been caused by several mechanisms. To form the aerosol, you need large >> amounts of OH. OH is formed by the effects of ultraviolet sunlight on >> ozone >> which in turn is formed by the effects of ultraviolet light on oxygen. >> The >> rate of formation of the aerosol is controlled by the rate that OH is >> produced. Thus it is possible that the sheer demand for OH caused a >> decrease >> in ozone but this has not been proven. There is also a strong suggestion >> that heterogenous processes on the surface of the aerosol instigated by >> HCL >> and even H2SO4 and various gases produced by man caused destruction of >> ozone >> and enlargement of the ozone hole. Thus the very presence of the aerosol >> enhances ozone destruction. >> >> Adding anthropogenic SO2 to the stratosphere is not as simple as it >> seems. >> We do not understand in detail the atmospheric chemistry that is likely >> to >> ensue. Man has a poor record in trying to modify nature. We need to >> proceed >> with caution. >> Peter >> >> Hi All, >> >> During the second day of the Hazards Colloquium, during the evening >> dinner >> venue , I had opportunity to discuss with Peter L. Ward about the >> much-talked-about geoengineering idea of using stratospheric sulphur >> dioxide to bring down the athmospheric temperatures. >> >> According to Peter the cooling effect of sulphur dioxide in isolation >> from >> water in high stratosphere does not work very well because of the >> stratospheric dry surroundings. Instead of sulphur dioxide, it would have >> to >> be sulphuric acid that is shipped up into high athomosphere. >> >> The volume of water will have to be 3 times the amount of sulphur >> dioxide, >> thus better results would come from using sulphuric acid readily. >> >> Peter also reminded that the sulphuric acid from Mt. Pinatubo destroyed >> about 5% of the stratospheric ozone. It is, therefore, questionnable for >> its large side effects, especially the attack of sulphur on ozone. >> >> To reduce the destruction of ozone layer, may be the spreading of >> sulphuric >> acid should take place just below it to keep it just beneath the main >> ozone >> belt but still a slightly higher than the clouds to prevent it flushed >> down >> too soon. Any comments and opinon on this "opportunity window" just >> beneath >> the ozone layer with a reduced impact to the ozone layer whilst still >> cooling the skies somewhat long? >> >> Hope, I have cited Peter's dinner time comments above accurately - I >> didn't >> drink too much wine, should be more or less put down correctly. >> >> Kind regards, >> >> Albert (the occasional heretic) >> >> >>> > by Bill McGuire, at UCL, London. >> >> >> >>> Date: Fri, 18 Sep 2009 02:02:08 +0100 >>> Subject: [geo] Re: Colloquium report: hazards from global warming >>> From: [email protected] >>> To: [email protected] >>> CC: [email protected]; [email protected] >>> >>> >>> This raises interesting points about the limits of SRM geoengineering. >>> Perhaps the experts on the list could explain why frequent volcanic >>> eruptions cause a warming effect? Can we be sure that H2S >>> geoengineering techniques we propose cannot result in this 'blowback'? >>> >>> A >>> >>> 2009/9/17 John Nissen <[email protected]>: >>> > >>> > This is a press report on the first day of the Hazards Colloquium, >>> > organised >>> > by Bill McGuire, at UCL, London. >>> > >>> > http://planetark.org/wen/54708 >>> > >>> > Global Warming May Bring Tsunami And Quakes: Scientists >>> > >>> > Date: 17-Sep-09 >>> > Country: UK >>> > Author: Richard Meares >>> > >>> > LONDON - Quakes, volcanic eruptions, giant landslides and tsunamis may >>> > become more frequent as global warming changes the earth's crust, >>> > scientists >>> > said on Wednesday. >>> > >>> > Climate-linked geological changes may also trigger "methane burps," >>> > the >>> > release of a potent greenhouse gas, currently stored in solid form >>> > under >>> > melting permafrost and the seabed, in quantities greater than all the >>> > carbon >>> > dioxide (CO2) in our air today. >>> > >>> > "Climate change doesn't just affect the atmosphere and the oceans but >>> > the >>> > earth's crust as well. The whole earth is an interactive system," >>> > Professor >>> > Bill McGuire of University College London told Reuters, at the first >>> > major >>> > conference of scientists researching the changing climate's effects on >>> > geological hazards. >>> > >>> > "In the political community people are almost completely unaware of >>> > any >>> > geological aspects to climate change." >>> > >>> > The vulcanologists, seismologists, glaciologists, climatologists and >>> > landslide experts at the meeting have looked to the past to try to >>> > predict >>> > future changes, particularly to climate upheaval at the end of the >>> > last >>> > ice >>> > age, some 12,000 years ago. >>> > >>> > "When the ice is lost, the earth's crust bounces back up again and >>> > that >>> > triggers earthquakes, which trigger submarine landslides, which cause >>> > tsunamis," said McGuire, who organized the three-day conference. >>> > >>> > David Pyle of Oxford University said small changes in the mass of the >>> > earth's surface seems to affect volcanic activity in general, not just >>> > in >>> > places where ice receded after a cold spell. Weather patterns also >>> > seem >>> > to >>> > affect volcanic activity - not just the other way round, he told the >>> > conference. >>> > >>> > LONDON'S ASIAN SUNSET >>> > >>> > Behind him was a slide of a dazzlingly bright orange painting, "London >>> > sunset after Krakatau, 1883" - referring to a huge Asian volcanic >>> > eruption >>> > whose effects were seen and felt around the world. >>> > >>> > Volcanoes can spew vast amounts of ash, sulphur, carbon dioxide and >>> > water >>> > into the upper atmosphere, reflecting sunlight and sometimes cooling >>> > the >>> > earth for a couple of years. But too many eruptions, too close >>> > together, >>> > may >>> > have the opposite effect and quicken global warming, said U.S. >>> > vulcanologist >>> > Peter Ward. >>> > >>> > "Prior to man, the most abrupt climate change was initiated by >>> > volcanoes, >>> > but now man has taken over. Understanding why and how volcanoes did it >>> > will >>> > help man figure out what to do," he said. >>> > >>> > Speakers were careful to point out that many findings still amounted >>> > only to >>> > hypotheses, but said evidence appeared to be mounting that the world >>> > could >>> > be in for shocks on a vast scale. >>> > >>> > Tony Song of NASA's Jet Propulsion Laboratory in California warned of >>> > the >>> > vast power of recently discovered "glacial earthquakes" -- in which >>> > glacial >>> > ice mass crashes downwards like an enormous landslide. >>> > >>> > In the West Antarctic, ice piled more than one mile above sea level is >>> > being >>> > undermined in places by water seeping in underneath. >>> > >>> > "Our experiments show that glacial earthquakes can generate far more >>> > powerful tsunamis than undersea earthquakes with similar magnitude," >>> > said >>> > Song. >>> > >>> > "Several high-latitude regions, such as Chile, New Zealand and >>> > Canadian >>> > Newfoundland are particularly at risk." >>> > >>> > He said ice sheets appeared to be disintegrating much more rapidly >>> > than >>> > thought and said glacial earthquake tsunamis were "low-probability but >>> > high-risk." >>> > >>> > McGuire said the possible geological hazards were alarming enough, but >>> > just >>> > one small part of a scary picture if man-made CO2 emissions were not >>> > stabilized within around the next five years. >>> > >>> > "Added to all the rest of the mayhem and chaos, these things would >>> > just >>> > be >>> > the icing on the cake," he said. "Things would be so bad that the odd >>> > tsunami or eruption won't make much difference." >>> > >>> > > >>> > >>> >>> >> >> > > > > > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.409 / Virus Database: 270.13.112/2387 - Release Date: 09/21/09 17:55:00 --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
