I should have mentioned that it might well be that we could find islands with mountains that reach above the boundary layer so one would not need to heat the plume too much or build too high a stack (one would have to transport the material to above the BL). One would, however, have to vaporize the sulfur that one would presumably start from, so some energy would be needed--maybe we could find mountainous islands that are windswept and so use wind-power.
Mike On 8/5/14 10:47 PM, "David Hawkins" <[email protected]> wrote: > Seems to me that for stack injection above the boundary layer you are going to > need a hot plume or a very tall stack indeed. Have you done calculations of > the materials and energy requirements for a sufficient number of stacks with > thermally buoyant plumes? > > Sent from my iPad > > On Aug 5, 2014, at 4:47 PM, "Mike MacCracken" > <[email protected]<mailto:[email protected]>> wrote: > > Hi Alan (and others as I had another query on this as well)‹Indeed, a bit more > explanation of the suggestion is warranted‹so a few thoughts and quick > reactions, not necessarily fine tuned: > > First, the SO2 would not be emitted from existing sources‹the idea is to > separate the sulfate layer from where people are. So, one would do from a few > stacks (hoses on balloons, etc.) on islands in the middle of oceans, using > sulfur taken out that has been captured by desulfurization or otherwise. > > Second, in that emission is not based on power generation time schedule, one > could emit when most favorable weather to sustain lifetime, etc. By being able > to fine tune time of emission, could likely do a bit of optimization in what > is done‹both to promote longer sulfate lifetime and greater solar effect. > > Third, to get maximum exposure to sunlight, one would want to create sulfate > layer in subtropics over the oceans-so maximum sunlight and darkest surface > albedo. Given injection in this region, air (depending on altitude and > location) would tend to be flowing toward ITCZ region, at least to some > extent. And sulfate deposition to ocean is not considered a problem. > > Fourth, as to amount, emissions would likely be somewhat less than being > emitted at present (doing in favorable locations for sunlight, low loading so > not shadowing lower aerosols, doing over large region, etc.); thus we have > some reasonable information about potential impacts. That the emissions are > being done in relatively remote areas and over larger domain would mean > reduction in impacts would very likely be a good bit greater than fractional > reduction in emissions. On acid rain, main concern in past was wintertime > accumulation of sulfate on snow and then sudden spring melting‹well, these > aerosols will be mainly in low latitudes, and would want to be doing mainly in > summer hemisphere for maximum effect. > > Fifth, in that location of sulfate layer would be mainly over the ocean, one > would not be creating the shadow over land areas that happens with > stratospheric aerosol loading and that, according to your model calculations, > tends to suppress the monsoon and hydrologic cycle; indeed, one would be > tending to slightly amplify the land-ocean temperature gradient. So, yes, some > meteorological effects that would need to be studied in models, but given it > is a bit hard to identify the special meteorological influences of the > regionally concentrated sulfate layers we had over Europe and North America, > and now China, it is not clear to me that the influences on meteorology of a > more widely spread but thinner layer would be that noticeable‹all to be > checked. [On meteorological influence, I would just add that, recalling > studies as far back as Namias in 1970s, it may be that gradients in oceanic > temperatures could influence storm tracks, and so it might be that one might > want to promote gradients in particular regions during particular seasons to > help promote desirable (or less undesirable) shifts‹all to be explored.] > > Sixth, this is not intended as an offset to the CO2, so not at all an > alternative to mitigation‹it would be intended to sustain the cooling offset > of existing sulfate layer so as not to create a penalty for cutting emissions > from coal-fired power plants (right now, if one cuts emissions from coal-fired > power plants, the simultaneous cutback in SO2 emissions actually leads to the > net effect being a warming influence that is not overtaken by the effect of > the CO2 cutback for several decades (by some rough, back of the envelope > calculations‹and a more detailed analysis of one specific situation calculated > in a paper in review). To offset an ongoing CO2 increase of the type GeoMIP is > studying (e.g., 4 times CO2, etc.), one really does have to go to > stratospheric sulfates. > > Seventh, not being in stratosphere, one avoids potential problems with the > ozone layer, astronomy, having aerosol aloft in high winter latitudes with > little sunlight, etc.--so one does have to consider the efficiency of sulfate > (so both time in atmosphere, but also amount of solar reflected while in the > atmosphere). And a chimney type injection to above the boundary layer might > well be less expensive that lofting SO2 into the stratosphere. > > Eighth, given it is quite readily turned off as sulfate lifetime is a week or > two, I don¹t see how this would be riskier than a global stratospheric layer > approach. Once one puts SO2 (or similar substance) into the stratosphere, one > has to live with the consequences/influences for a couple of years, so will be > harder to try to tune by season, etc. With the shorter-lifetime in the > troposphere, there is a bit better potential, although, of course, the ocean > thermal capacity will really dominate. > > Overall, this approach is similar to cloud brightening and sustaining sulfate > cooling might well be a very good and useful objective to which it should be > applied rather than thinking of using cloud brightening for offsetting CO2 > doubling and more. And it might even be that one could use sea salt CCN > instead of sulfate‹note I am proposing going above the marine clouds to try to > get a bit longer lifetime and injecting enough to also have a clear sky > effect‹whether doing that is worth the cost and effort would need to be > evaluated in terms of cost of doing, inadvertent and intended outcomes, etc. > But I don¹t see how this type of approach would be riskier than augmenting the > stratospheric aerosol layer. Of course, this is why we need a good research > program to really explore the various approaches and try to hone and refine > them so as to maximize desired and minimize undesired outcomes. > > Mike > > Michael C. MacCracken, Ph.D. > Chief Scientist for Climate Change Programs > Climate Institute > Suite 430 > 1400 16th Street N.W. > Washington DC 20036-2217 > Tel. 202-552-0163 > Home (and home office): 301-564-4255 > Email: [email protected] > > > On 8/5/14 3:45 PM, "Alan Robock" <[email protected]> wrote: > > > Dear Mike, > > I don't understand this suggestion. Because of the shorter sulfate lifetime > than in the stratosphere (even if it is more than the 1 week you get for > surface injections), you would require a much larger sulfur injection for the > same radiative forcing as compared to the stratosphere, and a much larger > resulting acid deposition in remote areas. And how could you be guaranteed to > maintain the emissions from a lot of stacks from small enterprises that would > keep changing over time based on business variations and local environmental > laws? This seems to be a much riskier strategy even than stratospheric > injections from a centralized operation. > > And why would you think most removal would be in the ITCZ? That would > require the sulfate to enter the ITCZ from the surface in specific tropical > regions. > > Alan > > Alan Robock, Distinguished Professor > Editor, Reviews of Geophysics > Director, Meteorology Undergraduate Program > Department of Environmental Sciences Phone: +1-848-932-5751 > 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 > http://twitter.com/AlanRobock > Watch my 18 min TEDx talk at http://www.youtube.com/watch?v=qsrEk1oZ-54 > On 8/5/2014 2:39 PM, Mike MacCracken wrote: > > > Re: [geo] A Win-Win research program proposal on SRM (sunlight reflection > methods) Regarding this proposal for sustaining the sulfate cooling influence, > the suggestion on this that I have been making for several years (see refs > below, among others) is similar: rather than having a relatively high sulfate > loading concentrated over populated areas, inject SO2 above the boundary layer > (important to promote a longer lifetime) to create thinner sulfate layers over > much larger remote areas of the ocean (e.g., over the Pacific and Indian > Oceans), hoping to promote both clear sky and cloudy sky brightness. Doing > this over the ocean would take advantage of its low albedo so that the > sulfates would not be offsetting reflected solar radiation from the surface. > Doing this over larger areas and at lower loadings would tend to moderate the > change in energy in a given area, although there would need to be testing of > this. Most removal might come in ITCZ rains, mostly over the ocean. > > Mike MacCracken > > > MacCracken, M. C., 2009: Beyond Mitigation: Potential Options for > Counter-Balancing the Climatic and Environmental Consequences of the Rising > Concentrations of Greenhouse Gases, Background Paper to the 2010 World > Development Report, Policy Research Working Paper (RWP) 4938, The World Bank, > Washington, DC, May 2009, 43 pp. > > MacCracken, M. C., 2009: On the possible use of geoengineering to moderate > specific climate change impacts, Environmental Research Letters, 4 > (October-December 2009) 045107 doi:10.1088/1748-9326/4/4/045107 > [http://www.iop.org/EJ/article/1748-9326/4/4/045107/erl9_4_045107.html]. > > MacCracken, M. C., 2011: Potential Applications of Climate Engineering > Technologies to Moderation of Critical Climate Change Impacts, IPCC Expert > Meeting on Geoengineering, 20-22 June 2011, Lima, Peru, pages 55-56 in Meeting > Report, edited by O. Edenhofer, R. Pichs-Madruga, Y. Sokona, C. Field, V. > Barros, T. F. Stocker, Q. Dahe, J. Minx, K. Mach, G.-K. Plattner, S. Schlömer, > G. Hansen, and M. Mastrandrea, Intergovernmental Panel on Climate Change, > Geneva, Switzerland. > > > > On 8/1/14 8:53 AM, "ecologist" <[email protected]> wrote: > > > Currently, anthropogenic tropospheric aerosols present both Dr Jekyll and Mr > Hyde faces. > > On the one hand, tropospheric aerosols play an important role on climate, > with a net cooling radiative forcing effect. > On the other hand, tropospheric aerosols affect terrestrial ecosystems and > human health and are associated with increased heart, lung and respiratory > diseases, which lead to disablement and numerous premature human deaths > (Shindell et al, 2012). > > Consequently, reducing anthropogenic tropospheric aerosols emissions, on the > one hand will lead to a positive forcing (warming) at local and regional > scale, and on the other hand will save numerous lives and significantly reduce > health costs. > > What is proposed is to investigate means whereby the cooling effect of > current emissions is kept unchanged and their deleterious effects are reduced, > using only modifications of existing industrial aerosols emitters. Key > advantages of such investigations are that they avoid most of the roadblocks > associated with SRM. > So, what is proposed is a Win-Win research program that will at the same time > allow indirect geoengineering research, and reduce tropospheric pollution. > (Important remark: it is not proposed to perform CCS, or CDR). > > This is so, because the current anthropogenic tropospheric sulphate aerosol > emissions are estimated to be almost two orders of magnitude larger than > requested by Stratospheric Particle Injection geoengineering schemes to offset > the effects of a 2 X CO2 (carbon dioxide concentration doubling in the > atmosphere). > Thus the strategy to reduce current sulphate tropospheric emissions and at > the same time to keep their current cooling effects will be like performing > indirect climate engineering without the need to artificially inject sulphates > in the stratosphere. > > Now, the radiative forcing due to sulphate aerosols is estimated to be -0.4 > W/m2 with a range of -0.2 to -0.8 W/m2. > On a global average basis, the sum of direct and indirect radiative forcing > at the top of atmosphere by anthropogenic aerosols is estimated to be -1.2 > W/m2 [-2.4 to -0.6 W/m2] (cooling) over the period of 1750 - 2000. This is > significant when compared to the positive (warming) forcing of +2.63 [±0.26] > W/m2 by anthropogenic long-lived greenhouse gases over the same period > [Forster et al., 2007]. > In heavily polluted regions, aerosol cooling overwhelms greenhouse warming > [Ramanathan et al., 2001; Li et al., 2010]. > > The tropospheric aerosol lifetimes are approximately 1 to 2 weeks, which is > quite shorter. Therefore, these current human made aerosols have an uneven > distribution, both horizontally and vertically, and are more concentrated near > their source regions over continents and in the boundary layer. > Emission reductions of aerosols in the troposphere will lead to a positive > forcing (warming), unless the sulphates lifetimes are increased and their > horizontal and vertical distribution are improved. Whilst the particulates are > removed, some part of the sulphates can be lofted higher to where they can act > as a solar-reflective shield to cool larger regions. > > To do so, what is proposed is to model the effects of a theoretical fivefold > aerosols emission reduction (80% removal of sulphates, NOx, and > 95% removal > of soot, black carbon, ashŠ) by adding filters or electrostatic precipitators > to the flue stack of a majority of fossil fuel fired power plants, for > adequate particulate filtering and scrubbing, and at the same time increasing > the height release of sulphates for a reduced number of other power plant > stacks in order to allow these (20% SOx) emissions to over pass the boundary > layer and stay longer in the atmosphere. > > This can be performed by the use of taller chimneys allowing the flue gases > to pass the boundary layer, so that the impact of a regional emission > reduction is not confined to the region itself, by allows intercontinental > transport (long-range transport) of these sulphates produced by existing > anthropogenic aerosols. > Several other possibilities exist to increase the height release and dilution > of gas emissions from flue stacks. > > This strategy was proposed in page 818-819 of an open access article > http://www.sciencedirect.com/science/article/pii/S1364032113008460 Fighting > global warming by climate engineering. > > Two figures are attached to summarize this research proposal > > > Public perception of SRM climate engineering is often presented as Ulysses > choices between the perils of Scylla and Charybdis, despite the very good > cooling potential to mitigate global warming, and the high effectiveness and > accessibility of geoengineering schemes consisting of the stratospheric > injection of sulphate aerosols. > The Win-Win strategy proposed here may change this perception at the same > time as helping to advance CE research... > > > Renaud de_Richter, PhD > http://www.solar-tower.org.uk/ > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/geoengineering. > For more options, visit https://groups.google.com/d/optout. > > > > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to > [email protected]<mailto:geoengineering+unsubscribe@ > googlegroups.com>. > To post to this group, send email to > [email protected]<mailto:[email protected]>. > Visit this group at http://groups.google.com/group/geoengineering. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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