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. 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