Winds in the stratosphere (above 53,000 ft) tend to blow from east to west, but periodically reverse. The links below are to simulations of how the Pinatubo eruption gases spread. Release above 90,000 ft is of little value in that the gas will simply settle back down to that altitude due to the density of the air and as noted before, release outside the tropics shortens the lifetime of the aerosol, although in a more complex distribution scheme than the simple ones studied to date, it might offer some as yet unknown advantages. Note the misuse of the word elevation for altitude.
http://www.gsfc.nasa.gov:80/gsfc/newsroom/tv%20page/G02-016_earth.htm (Click on "Volcanic Plume Movie" at bottom of page to see video.) ITEM (2): Volcanic Plume Spreads - This computer model shows the dispersion of the volcanic plume from the Mt. Pinatubo volcano. The 1991 Pinatubo eruption was sulfur-rich, producing volcanic clouds that lasted a number of years in the stratosphere. The Pinatubo eruption widely expanded the area of ozone loss over the Arctic and Antarctic. Red colors indicate higher elevations and blue colors indicate lower elevations for the plume. http://svs.gsfc.nasa.gov/vis/a000000/a000000/a000074/ Another animation of the Pinatubo aerosol spread generated from satellite imagery. Appears to cover period of about 3 months post eruption. ----- Original Message ----- From: Andrew Lockley To: Alvia Gaskill Cc: John Nissen ; [email protected] ; [email protected] ; [email protected] ; [email protected] ; [email protected] ; [email protected] ; [email protected] ; [email protected] Sent: Saturday, May 09, 2009 9:11 PM Subject: Re: [geo] Re: Balancing the pros and cons of geoengineering A few comments on that: 1) Droplet size shouldn't affect chemistry. Both surface area and the cross sectional area are proportional to the square of the radius. Volume affects residence time, and is proportional to the cube of the radius. Big droplets are shorter-lived, and hence more controllable, but less mass-efficient. 2) The Brewer Dobson circulation drives aerosol transport and predominantly acts towards the poles. I am not aware of East-West winds in the stratosphere (but that's probably because I know sweet FA about such things, not cos they don't exist) In the absence of EW circulation, what will force aerosols to India? 3) Release into the high stratosphere would remove the need to release precursor at the equator, as lifting from the BDC would not be needed. What's the peak height of the balloons? 4) On a more general point, should we start a 'wish list' of research papers that need to be done. Eager young PhD students will hopefully come along and pick these up for us. Or is that just fantasy? A 2009/5/10 Alvia Gaskill <[email protected]> This depends on the objective. For a global aerosol program designed to stop the warming of the entire planet, the answer is no. In this case, we want the aerosol to stay suspended as long as possible to get the maximum amount of sunlight scattering and to minimize the quantity of precursor that has to be transported to the stratosphere. The longer lived aerosol would also tend to be less of a problem in ozone depletion as the surface area would be reduced relative to larger shorter lived droplets. If the aerosol precursor is released in the tropical stratosphere, it will circle and cover the entire globe, including India. Releases outside the tropics could be attempted, but this would create uneven warming of a different kind and a good portion of India and all of China is outside the tropics anyway. In the case of an Arctic only aerosol program, the aerosol size issue is probably the same, but the supporters have set as criteria releasing the precursor in the upper troposphere (around 45,000 ft) in the spring with the goal of having it all gone by the end of the summer. This would minimize any ozone depletion as the aerosol would have to be present in the winter for the "dark" reactions to take place. Having the aerosol active only during the summer might lessen or have no impact on monsoons or other seasonal rainfall patterns. There is no data to support this one way or the other. Note also that the limited modeling done to date in addition to the resolution of regional impacts issue mentioned earlier today also has focussed almost entirely on high loading of aerosol precursor to simulate that required to offset a doubling of CO2 from pre-industrial. While these extreme conditions may actually be required at some point decades from now, a more likely scenario is one of a gradual incremental increase in the aerosol to match GHG forcing or to offset loss of tropospheric aerosols. In such cases, the climate system may adjust and there may be no impact on monsoonal flows or precipitation or the effect may be very gradual and so can be dealt with by adaptation. The point is we simply don't know because these studies haven't been done. Thus the risk questions posed by John Nissen represent work that needs to be done. ----- Original Message ----- From: Andrew Lockley To: John Nissen Cc: Alvia Gaskill ; [email protected] ; [email protected] ; [email protected] ; [email protected] ; [email protected] ; [email protected] ; [email protected] ; [email protected] Sent: Saturday, May 09, 2009 8:01 PM Subject: Re: [geo] Re: Balancing the pros and cons of geoengineering Can't we modify the aerosol size, and deployment patterns, to make sure they fall out quickly and don't go anywhere near India? A 2009/5/9 John Nissen <[email protected]> Very good discussion. I'm trying to get a balance of pros (benefits B1-B7) and cons (specific fears S1-S21). What I'd like out of our discussion is some kind of risk assessment for the possible downside of a weaker monsoon, as this is considered the biggest risk in the regional effects (S1). And we could make this reasonably pessimistic, to be on the safe side - i.e. be cautious with the application of geoengineering. On the other hand, we might be able to reduce this risk, e.g. by neutralising sulphate aerosol; if there's a good chance of this working, then we can factor that into the calculation. Or the risk might be offset by a benefit in that region, e.g. improved summer water supply from Himalayan glaciers? So, what kind of impact would a weaker monsoon (ISM) have on India? What is the probability of stratospheric aerosols deployed in the Arctic would produce a weaker monsoon? Can this risk be significantly countered? Can it be significantly offset? Note that the risk on benefit side might be measured in terms of a risk, without geoengineering, of millions or even billions of lives being lost (especially if massive methane release adds several degrees of global warming, B4). Alternatively we could measure in GDP lost - current global GDP (aka GWP) is about $60 trillion I believe. Cheers, John ----- Original Message ----- From: "Alvia Gaskill" <[email protected]> To: <[email protected]>; <[email protected]> Cc: <[email protected]>; "Andrew Lockley" <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]> Sent: Saturday, May 09, 2009 4:50 PM Subject: Re: [geo] Re: Balancing the pros and cons of geoengineering Stephen makes a good point that leads to a more general one. If there are precipitation reductions associated with sunlight blocking schemes, consideration should also be given to mitigating these, analogous to the medications given to patients with Type II diabetes to combat the side effects of the primary drug. This is an oversimplification, but the way summer monsoons work is that in the summer the land gets warmer than the ocean faster, creating a low pressure area and this causes on shore flow as air moves from high to low presssure. For some reason, Laki caused this to be muted. There were no aerosols from Laki over India and it has been suggested there was a teleconnected response (see the paper Stephen attached) although in paleo climate the authors say the effects were direct, but don't give specifics. In the case of Pinatubo, both the land and sea were cooled by the aerosol and the land simply didn't heat up fast enough to generate the on shore flow. If the Arctic only aerosol geoengineering does cause a reduction in the ISM (Indian Summer Monsoon as there are other monsoons that affect India, but this is the most important one), use of the cloud whitening to restore at least some of the temperature differential should be considered. Likewise, in a global aerosol scheme, with a global aerosol spread similar to that of Pinatubo, the cloud whitening could also be used to create a temperature differential, but at some point it becomes a race to the bottom, with the land temperature simply too cool to initiate the low pressure area. In this case, reducing the depth of the aerosol layer over the land may be the most effective way to restore the dynamics. I previously suggested using ammonia released from either planes or balloons to react with the sulfate aerosol and drop them out as ammonium sulfate. This idea as well as Stephen's could be applied to other locations such as the Amazon, Eastern China and Africa where models indicate unacceptable reductions in precipitation are a result of either aerosol geoengineering or global warming. Of course, the ammonia wouldn't be of any value in a global warming/no aerosol scenario. I said in one the earliest papers I wrote on geoengineering that eventually we were going to have to learn how to manipulate the climate to our advantage. That includes both gross scale and fine tuning. In a related issue, last year I posted a link from a group in the UK that was carrying out some 130 different models of aerosol geoengineering. It was a volunteer effort among universities. If they have done even a fraction of the modeling, this work should be taken into account in designing new studies such as Rutgers is proposing. Anyone have an update? You may recall also that we spent some time last year discussing the significance of the "little brown blotches" in absolute terms and now Ken also raises the issue of their resolution. http://en.wikipedia.org/wiki/Monsoon Monsoons are caused by the larger amplitude of the seasonal cycle of land temperature compared to that of nearby oceans. This differential warming happens because heat in the ocean is mixed vertically through a "mixed layer" that may be fifty meters deep, through the action of wind and buoyancy-generated turbulence, whereas the land surface conducts heat slowly, with the seasonal signal penetrating perhaps a meter or so. Additionally, the specific heat capacity of liquid water is significantly higher than that of most materials that make up land. Together, these factors mean that the heat capacity of the layer participating in the seasonal cycle is much larger over the oceans than over land, with the consequence that the air over the land warms faster and reaches a higher temperature than the air over the ocean.[11] Heating of the air over the land reduces the air's density, creating an area of low pressure. This produces a wind blowing toward the land, bringing moist near-surface air from over the ocean. Rainfall is caused by the moist ocean air being lifted upwards by mountains, surface heating, convergence at the surface, divergence aloft, or from storm-produced outflows at the surface. However the lifting occurs, the air cools due to expansion, which in turn produces condensation. In winter, the land cools off quickly, but the ocean retains heat longer. The cold air over the land creates a high pressure area which produces a breeze from land to ocean.[11] Monsoons are similar to sea and land breezes, a term usually referring to the localized, diurnal (daily) cycle of circulation near coastlines, but they are much larger in scale, stronger and seasonal.[12] ----- Original Message ----- From: "Stephen Salter" <[email protected]> To: <[email protected]> Cc: <[email protected]>; "Andrew Lockley" <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]>; <[email protected]> Sent: Saturday, May 09, 2009 6:43 AM Subject: [geo] Re: Balancing the pros and cons of geoengineering Hi All The attached paper by Zickfeld et al shows, in figure 2, what might happen to the Indian Monsoon if we do nothing. Cooling the sea relative to the land should move things in the opposite direction. Stephen Emeritus Professor of Engineering Design School of Engineering and Electronics University of Edinburgh Mayfield Road Edinburgh EH9 3JL Scotland tel +44 131 650 5704 fax +44 131 650 5702 Mobile 07795 203 195 [email protected] http://www.see.ed.ac.uk/~shs Alan Robock wrote: Dear Ken, I agree. We need several models to do the same experiment so we can see how robust the ModelE results are. That is why we have proposed to the IPCC modeling groups to all do the same experiments so we can compare results. Nevertheless, observations after large volcanic eruptions, including 1783 Laki and 1991 Pinatubo, show exactly the same precip reductions as our calculations. Even if precip in the summer monsoon region goes down, how important is it for food production? It will be countered by increased CO2 and increased diffuse solar radiation, both of which should make plants grow more. We need people studying impacts of climate change on agriculture to take our scenarios and analyze them. Alan Alan Robock, Professor II Director, Meteorology Undergraduate Program Associate Director, Center for Environmental Prediction Department of Environmental Sciences Phone: +1-732-932-9800 x6222 Rutgers University Fax: +1-732-932-8644 14 College Farm Road E-mail: [email protected] New Brunswick, NJ 08901-8551 USA http://envsci.rutgers.edu/~robock Ken Caldeira wrote: A few questions re claims about monsoons: 1. How well is the monsoon represented in the model's base state? Is this a model whose predictions about the monsoon are to be trusted? 2. Since the believability of climate model results for any small region based on one model simulation is low, for some reasonably defined global metrics (e.g., rms error in temperature and precip, averaged over land surface, cf. Caldeira and Wood 2008) is the amount of mean climate change reduced by reasonable aerosol forcing? (I conjecture yes.) Alan is interpreting as significant his little brown blotches in the right side of Fig 7 in a model with 4 x 5 degree resolution (see attachment). How does the GISS ModelE do in the monsoon region? If you look at Fig 9 of Jiandong et al (attached), at least in cloud radiative forcing, GISS ModelE is one of the worst IPCC AR4 models in the monsoon region. So, while Alan may ultimately be proven right, it is a little premature to be implying that we know based on Alan's simulations how these aerosol schemes will affect the Indian monsoon. If you look at Caldeira and Wood (2008), we find that idealized Arctic solar reduction plus CO2, on average precipitation is increased relative to the 1xCO2 world. ___________________________________________________ Ken Caldeira Carnegie Institution Dept of Global Ecology 260 Panama Street, Stanford, CA 94305 USA [email protected] <mailto:[email protected]>; [email protected] <mailto:[email protected]> http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab +1 650 704 7212; fax: +1 650 462 5968 > -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. 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