Dear David, You are right! To increase the height of smokestack exit, you either need: 1/ very tall stacks, 2/ hotter plumes... ... 3/ or you can increase the exit velocity by boosting the speed with a fan, 4/ or by taking advantage of the wind, as the horizontal air flow can be used to induce a secondary vertical air flow (there exist commercially available modifications of conventional stacks into a "high plume stacks" see figure attached. Those systems generally apply Bernoulli's principle and by venturi effect boost the speed of the exhaust from the smokestack)... 5/... *or also make profit of natural (or artificial) atmospheric convection processes*... 6/ or a combination of several of the foregoing!
*Convective processes over Asia frequently transport boundary layer air into the upper troposphere (UT) where long range transport associated with movement in the jet stream rapidly redistributes Asian emissions globally* within timescales of days to weeks (Liu et al., 2003 <http://www.sciencedirect.com/science/article/pii/S1352231014004567#bib26> and Turquety et al., 2008 <http://www.sciencedirect.com/science/article/pii/S1352231014004567#bib47>). Maximum convective activity occurs during summer, when the Asian summer monsoon dictates tropospheric circulation over South Asia (Qian and Lee, 2000 <http://www.sciencedirect.com/science/article/pii/S1352231014004567#bib35>). During this period frequent and persistent deep convection over the continent efficiently lofts polluted air masses from the boundary layer to the UT on a large scale, with uplifted pollutants being transported to the west where they contribute to elevated levels of tropospheric ozone over the Mediterranean (Baker et al., 2011 <http://www.sciencedirect.com/science/article/pii/S1352231014004567#bib3>, Lelieveld et al., 2002 <http://www.sciencedirect.com/science/article/pii/S1352231014004567#bib24>, Park et al., 2009 <http://www.sciencedirect.com/science/article/pii/S1352231014004567#bib34>, Randel et al., 2010 <http://www.sciencedirect.com/science/article/pii/S1352231014004567#bib36>, Scheeren et al., 2003 <http://www.sciencedirect.com/science/article/pii/S1352231014004567#bib39> and Schuck et al., 2010 <http://www.sciencedirect.com/science/article/pii/S1352231014004567#bib40>). In winter, convective activity is at a minimum and uplifting of boundary layer air is further suppressed by the Siberian High (Liu et al., 2003 <http://www.sciencedirect.com/science/article/pii/S1352231014004567#bib26>). Warm conveyor belts (WCBs) act to lift air from the Asian boundary layer into the free troposphere where it is then transported across the Pacific, with maximum activity in winter and spring (Cooper et al., 2004 <http://www.sciencedirect.com/science/article/pii/S1352231014004567#bib11> and Eckhardt et al., 2004 <http://www.sciencedirect.com/science/article/pii/S1352231014004567#bib13>). Similarly, WCBs also bring air from North America to the European UT, with maximum activity in winter (Auvray and Bey, 2005 <http://www.sciencedirect.com/science/article/pii/S1352231014004567#bib2> and Eckhardt et al., 2004 <http://www.sciencedirect.com/science/article/pii/S1352231014004567#bib13>). *Extracted from:* Baker, A. K., Traud, S., Brenninkmeijer, C. A., Hoor, P., Neumaier, M., Oram, D. E., ... & Ziereis, H. (2014). Pollution Patterns in the Upper Troposphere over Europe and Asia observed by CARIBIC. *Atmospheric Environment*, Volume 96 <http://www.sciencedirect.com/science/journal/13522310/96/supp/C>, October 2014, Pages 245–256. Cheers Renaud Le mercredi 6 août 2014 05:01:24 UTC+2, Mike MacCracken a écrit : > > 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" <dhaw...@nrdc.org <javascript:>> > 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" > > <mmac...@comcast.net <javascript:><mailto:mmacc...@comcast.net > <javascript:>>> 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: mmac...@comcast.net <javascript:> > > > > > > On 8/5/14 3:45 PM, "Alan Robock" <rob...@envsci.rutgers.edu > <javascript:>> 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: rob...@envsci.rutgers.edu > <javascript:> > > 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" <ecolo...@gmail.com <javascript:>> > 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 geoengineerin...@googlegroups.com <javascript:>. > > To post to this group, send email to geoengi...@googlegroups.com > <javascript:>. > > 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 > > geoengineerin...@googlegroups.com <javascript:><mailto: > geoengineering+unsubscribe@ <javascript:> > > googlegroups.com>. > > To post to this group, send email to > > geoengi...@googlegroups.com <javascript:><mailto: > geoengi...@googlegroups.com <javascript:>>. > > 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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