Peter Ward raised an important, yet to date unanswered question about the efficacy of man-made sulfate aerosols. Whereas water is not limited in their formation from volcanic eruptions because large amounts of water are also injected into the stratosphere, he is correct about the stratosphere being very dry in the absence of significant volcanic contributions.
In fact, the water content is fairly consistent, around 5ppmv from the tropical tropopause (53,000 ft) all the way up to the stratopause (168,000 ft). Aerosol formed below 53,000 ft has a lifetime measured in days and weeks, not months and years as would be necessary for a global climate modification scheme. The Lowermost Stratosphere, the part of the atmosphere between the troposphere and the tropical tropopause has varying amounts of water vapor and clouds and isn't part of this analysis. This means that any injections of SO2 or its precursor H2S will depend entirely on this low level of water to produce the H2SO4 and the hydrated form of this that is the aerosol. Most of the concerns, objections, problems with the man-made aerosol strategy have been concentrated on whether or not the sulfuric acid will have reached a point of supersaturation whereupon new particles of aerosol (I prefer to call them droplets, but the convention is to refer to them as particles, in part because of their size and in part because they also consist of a particle of solid material of meteoritic or crustal origin. Today's cookout or forest fire could produce next year's aerosol droplet as some of the soot will eventually reach the stratosphere.) There is still some uncertainty as to the exact reaction path from SO2 to hydrated H2SO4, but it seems to follow this order: SO2 reacts with OH radical to form HOSO2 radical. O2 then reacts with the HOSO2 to form HO2 radical and SO3. So far, no water has been consumed. The SO3 then reacts with two molecules of H2O to form H2SO4 in a multi-step reaction. However, a net of one water molecule is consumed. The H2SO4 particle then adsorbs more water vapor until a ratio of 75% H2SO4/25% water is achieved. This aerosol particle is then stable until it runs into other ones (coagulation) or sediements (falls out of the stratosphere). The conversion of 6 Mt of S (similar to Pinatubo) would result in 24Mt of sulfate aerosol. S to SO2 a doubling and SO2 to H2SO4 (~ 2H2O) another doubling. So you need one molecule of water to produce the H2SO4 and two more to make the aerosol. Water's contribution to the total aerosol formation is 40%, not 3 times. Then, to make the 24 Mt of aerosol, around 10 Mt of water are required. Is there 10 Mt of water in the stratosphere? The volume of the Earth's atmosphere up to 100Km is 51 trillion cubic meters. The stratosphere ranges from 16Km to 50Km or about 34% of the total volume or 17 trillion cubic meters. 5 ppmv of water vapor is about 50 ug/m3 (based on a temperature of -40C and an air pressure of 8 mm Hg at 100,000 ft). Thus, in the entire stratosphere, the total mass of water vapor is 850 trillion ug which is the same as 850 billion mg or 850 million g. One million g = 1 ton, so the stratosphere contains 850 Mt of water vapor, 90X that required to produce a Pinatubo-scale aerosol burden. However, since only a fraction of the stratosphere would be used for aerosol formation, most likely from 20 to 30Km, the total being from 16 to 50Km, the water vapor would have to come from 30% of the stratosphere or a total water vapor content of 260 million tons. Hence, to achieve a Pinatubo loading of the stratosphere by man-made injection of aerosol precursor would use 3.5% of the available water vapor. Thus, water vapor is not a limiting factor in aerosol formation. I hope these calculations and the underlying assumptions are correct, but if not, please inform as this is an important part of the puzzle we need to understand going forward. It won't be possible to directly inject pure sulfuric acid or a 75/25% mixture with water, so either the gases work or we can forget about it. ----- Original Message ----- From: Veli Albert Kallio To: Andrew Lockley ; John Nissen Cc: Geoengineering FIPC ; Professor William McGuire ; [email protected] Sent: Friday, September 18, 2009 8:04 PM Subject: [geo] Re: Colloquium report: hazards from global warming 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." > > > > > > > > > Upgrade to Internet Explorer 8 Optimised for MSN. Download Now --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
