http://www.agu.org/cgi-bin/SFgate/SFgate?language=English&verbose=0&listenv=table&application=fm08&convert=&converthl=&refinequery=&formintern=&formextern=&transquery=geoengineering&_lines=&multiple=0&descriptor=%2fdata%2fepubs%2fwais%2findexes%2ffm08%2ffm08%7c230%7c4919%7cModification%20of%20Cirrus%20Clouds%20to%20Reduce%20Global%20Warming%7cHTML%7clocalhost:0%7c%2fdata%2fepubs%2fwais%2findexes%2ffm08%2ffm08%7c54586034%2054590953%20%2fdata2%2fepubs%2fwais%2fdata%2ffm08%2ffm08.txt
U43A-0044 TI: Modification of Cirrus Clouds to Reduce Global Warming AU: * Mitchell, D L EM: [EMAIL PROTECTED] AF: Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512-1095, United States AU: Rasch, P J EM: [EMAIL PROTECTED] AF: NCAR, P.O. Box 3000, Boulder, CO 80307, United States AB: As far as we know, no studies have addressed the possibility of modifying cirrus clouds to reduce global warming. Here we explore this possibility and associated feasibility issues. To introduce this concept, some background information is needed. The effect of cirrus on climate can be quantified through their predicted impact on climate sensitivity, S (i.e. the equilibrium response of global- mean surface temperature to CO2 doubling) in global climate model (GCM) simulations. A recent study using an ensemble of thousands of "perturbed physics" GCM simulations found that S was most strongly influenced by the entrainment coefficient and the ice fall speed, indicating that S depends more on changes in cirrus clouds than on low-level boundary layer clouds. It may be possible to modify the ice fall speed in cirrus clouds which controls ice removal rates and affects the cirrus ice content, life cycle and coverage, as well as the upper troposphere relative humidity. The main impact of reducing the ice fall speed was an increase in longwave cloud forcing. In a different recent GCM study, we have used the mean size of the ice particle size distribution to change the representative ice fall speed, V. By decreasing V, the cirrus coverage was increased 5.5%, strongly affecting annual zonal means of cloud forcing, heating rates and temperatures in the upper troposphere. This led us to speculate that the introduction of aerosol particles into the upper troposphere (T < -40 C) that efficiently form ice crystals through heterogeneous nucleation may result in larger ice particles with higher fall speeds since the heterogeneous nuclei would outcompete the natural homogeneous freezing ice nuclei for water vapor. This would reduce longwave cloud forcing and lower surface temperatures, as described above. A third recent GCM study supports our speculation, showing that heterogeneous ice nucleation for these conditions produces larger ice crystals with higher fall velocities (relative to ice crystals formed by homogeneous nucleation). These studies and others beg the question of whether the introduction of efficient heterogeneous ice nuclei in regions of the upper troposphere normally dominated by homogeneous nucleation would reduce cirrus cloud coverage through higher ice fall speeds or would increase cirrus coverage by allowing nucleation in otherwise clear-sky regions supersaturated with respect to ice. The introduction of efficient ice nuclei might initially increase cirrus coverage in these regions, but once a new equilibrium of cirrus coverage is established, it is unclear whether cirrus coverage would be more or less than present day conditions. This question could be explored in climate simulations using microphysically advanced GCMs. Should the method appear promising, it could be applied by introducing efficient ice nuclei into the upper troposphere using commercial airliners. Weather modification research has developed ice nucleating substances that are extremely effective at these cold temperatures, are non-toxic and are relatively inexpensive. The strategy is to build-up a background concentration of efficient ice nuclei in the -40 to -60 C zone so that cirrus forming by natural processes will experience these nuclei and grow larger crystals. High level winds would disperse the nucleant aerosol from the flight corridors. While there are risks of affecting the climate system in unforeseen ways, time scales in the atmosphere are relatively short, and this geoengineering experiment could be terminated at any time. UR: http://www.dri.edu/Projects/Mitchell/ DE: 0321 Cloud/radiation interaction DE: 1620 Climate dynamics (0429, 3309) DE: 3310 Clouds and cloud feedbacks DE: 3311 Clouds and aerosols SC: Union [U] MN: 2008 Fall Meeting [Comments. Interesting idea. Cloud seeding in order to destroy clouds. No mention of the scale issues, i.e., how many planes and over what areas and how effective this could be if applied maximally. Commercial air traffic is predominantly over the N.H. and mostly the U.S. and Europe, but obviously, conventional heavy aircraft could be used anywhere. AG] http://www.agu.org/cgi-bin/SFgate/SFgate?language=English&verbose=0&listenv=table&application=fm08&convert=&converthl=&refinequery=&formintern=&formextern=&transquery=keith&_lines=&multiple=0&descriptor=%2fdata%2fepubs%2fwais%2findexes%2ffm08%2ffm08%7c677%7c1995%7cClimate%20engineering%20and%20climate%20stabilization%7cHTML%7clocalhost:0%7c%2fdata%2fepubs%2fwais%2findexes%2ffm08%2ffm08%7c17756638%2017758633%20%2fdata2%2fepubs%2fwais%2fdata%2ffm08%2ffm08.txt This one wasn't listed in the geoengineering section. GC23B-03 INVITED TI: Climate engineering and climate stabilization AU: * Keith, D W EM: [EMAIL PROTECTED] AF: University of Calgary, Energy and Environmental Systems Group, Room 602, Earth Sciences Building, Calgary, AB T2N 1N4, Canada AB: Analysis of tools for "climate stabilization" have traditionally focused on efficiency and fuel substitution as the means to reduce emissions and climate forcing. Over the last decade, a host of new engineering options have begun to receive serious consideration including CO2 capture and storage (CCS), biomass combined with CCS in order to achieve negative emissions, the direct capture of CO2 from air, various geochemical means to engineer negative carbon fluxes, and finally the direct engineering of radiative forcing by the injection of scattering particles into the upper atmosphere. I will review and contrast these technologies focusing on there (i) technical status, (ii) potential scope and (iii) scale of application, the risk of unintended side effects (iv) and finally I will speculate on the ways in which these options might alter the economics and political dynamics of carbon stabilization. DE: 1605 Abrupt/rapid climate change (4901, 8408) DE: 1622 Earth system modeling (1225) DE: 1699 General or miscellaneous DE: 6620 Science policy (0485) SC: Global Environmental Change [GC] MN: 2008 Fall Meeting [Comments. Seems like too much to cover in one talk. AG] http://www.agu.org/cgi-bin/SFgate/SFgate?language=English&verbose=0&listenv=table&application=fm08&convert=&converthl=&refinequery=&formintern=&formextern=&transquery=keith&_lines=&multiple=0&descriptor=%2fdata%2fepubs%2fwais%2findexes%2ffm08%2ffm08%7c384%7c6022%7cPreparing%20Climate%20Engineering%20Responses%20to%20Climate%20Emergencies%20I:%20Aerosol%20Particle%20Design%20and%20Stratospheric%20Delivery%20Options%7cHTML%7clocalhost:0%7c%2fdata%2fepubs%2fwais%2findexes%2ffm08%2ffm08%7c54450088%2054456110%20%2fdata2%2fepubs%2fwais%2fdata%2ffm08%2ffm08.txt : U41E-02 TI: Preparing Climate Engineering Responses to Climate Emergencies I: Aerosol Particle Design and Stratospheric Delivery Options AU: * Keith, D EM: [EMAIL PROTECTED] AF: ISEEE, Energy & Environmental Systems Group, University of Calgary 2500 Unviversity Drive NW, Calgary, AB T2N 1N4, Canada AU: Battisti, D EM: [EMAIL PROTECTED] AF: Dept. of Atmospheric Sciences, University of Washington Box 351640, Seattle, WA 98195-1640, United States AU: Blackstock, J EM: [EMAIL PROTECTED] AF: Risk and Vulnerability Group, International Institute for Applied Systems Analysis 1 Laxenburg, Schlossplatz, A-2361, Austria AU: Caldeira, K EM: [EMAIL PROTECTED] AF: Department of Global Ecology, Carnegie Institution of Washington 260 Panama St., Stanford, CA 94305, United States AU: Eardley, D EM: [EMAIL PROTECTED] AF: Inst for Theoretical Physics, University of California Kohn Hall, UCSA, Santa Barbara, CA 93106, United States AU: Katz, J EM: [EMAIL PROTECTED] AF: Department of Physics, Washington University in St. Louis 1 Brookings Drive - Campus Box 1105, St Louis, MO 63130, United States AU: Koonin, S EM: [EMAIL PROTECTED] AF: BP p.l.c., 1 St. James's Square, London, SW1 4PD, United Kingdom AU: Patrinos, A EM: [EMAIL PROTECTED] AF: Synthetic Genomics, 901 D Street SW Suite 900, Washington, DC 20024, United States AU: Schrag, D EM: [EMAIL PROTECTED] AF: Department of Earth and Planetary Sciences, Harvard University 20 Oxford Street, Cambridge, MA 02138, United States AU: Socolow, R EM: [EMAIL PROTECTED] AF: Mechanical and Aerospace Engineering, Princeton University Engineering Quad D- Wing, Princeton, NJ 08544, United States AB: Although international efforts to stabilize CO2 concentrations may well prove sufficient to prevent or delay severe climate impacts, there is already a non-negligible possibility that the climate will respond rapidly and non-linearly to present concentrations. If climate sensitivity high, it may be too late to avert dramatic consequences for human societies or natural ecosystems even with immediate and aggressive mitigation efforts. Climate engineering that induced rapid changes in the climate system might limit the risks posed by such "climate emergencies," although uncertainty in the climatic response to such interventions makes it difficult to estimate the risk-effectiveness of such engineering. The authors of this abstract thus gathered for a one-week intensive study to explore the question: What program of comprehensive technical research over the next decade would maximally reduce the uncertainties associated with climate engineering responses to climate emergencies? We focused on the possible injection of aerosols into the stratosphere. This presentation (see also Blackstock et al.) focuses on technical evaluation of aerosol particle and stratospheric deployment alternatives. First, the five core (multidimensional) "control variables" for stratospheric aerosol interventions are identified that could be engineered to tailor its climatic impacts: 1) aerosol material composition; 2) aerosol particle size (and shape); 3) amount of aerosol dispersed; 4) geographic and vertical dispersion location; and 5) temporal sequencing of aerosol dispersion. Correlations between other relevant intervention characteristics (e.g. aerosol spectral scattering properties and lifetimes) and these control variables are identified (along with sources of uncertainty therein). We examine fundamental and practical constraints on the range and precision with which these variables can be controlled. Limits imposed by both natural physical and chemical processes (e.g. chemical reactivity and particle agglomeration) and feasible deployment technologies (e.g. high-altitude lofting capabilities and aerosol dispersion mechanisms) are evaluated. This analysis yields insights into new avenues of research in particular, viable aerosol material possibilities and stratospheric dispersion methods (e.g. methods for dispersing mass-efficient volatile hydride compounds which oxidize and coagulate to form aerosols)—along with a better appreciation of the limits and uncertainty governing all such options. DE: 0305 Aerosols and particles (0345, 4801, 4906) DE: 1605 Abrupt/rapid climate change (4901, 8408) DE: 1699 General or miscellaneous DE: 6620 Science policy (0485) SC: Union [U] MN: 2008 Fall Meeting [Comments. Hydride compounds are usually toxic. Also, manufacturing costs would likely be prohibitive and not carbon neutral. Same for any other kind of engineered material. AG] http://www.agu.org/cgi-bin/SFgate/SFgate?language=English&verbose=0&listenv=table&application=fm08&convert=&converthl=&refinequery=&formintern=&formextern=&transquery=keith&_lines=&multiple=0&descriptor=%2fdata%2fepubs%2fwais%2findexes%2ffm08%2ffm08%7c421%7c5724%7cPreparing%20Climate%20Engineering%20Responses%20to%20Climate%20Emergencies%20II:%20Impact%20Detection%2fAttribution%20and%20Field%20Testing%7cHTML%7clocalhost:0%7c%2fdata%2fepubs%2fwais%2findexes%2ffm08%2ffm08%7c54590953%2054596677%20%2fdata2%2fepubs%2fwais%2fdata%2ffm08%2ffm08.txt Preparing Climate Engineering Responses to Climate Emergencies II: Impact Detection/Attribution and Field Testing AU: * Blackstock, J J EM: [EMAIL PROTECTED] AF: International Institute for Applied Systems Analysis, Schlossplatz 1, Laxenburg, A- 2361, Austria AU: Battisti, D EM: [EMAIL PROTECTED] AF: University of Washington, Box 351640, Seattle, WA 98195-1640, United States AU: Caldeira, K EM: [EMAIL PROTECTED] AF: Stanford University, 260 Panama St., Stanford, CA 94305, United States AU: Eardley, D M EM: [EMAIL PROTECTED] AF: University of California, Kohn Hall, UCSB, Santa Barbara, CA 93106, United States AU: Katz, J I EM: [EMAIL PROTECTED] AF: Washington University in St. Louis, 1 Brookings Drive - Campus Box 1105, St. Louis, MO 63130, United States AU: Keith, D W EM: [EMAIL PROTECTED] AF: University of Calgary, 2500 University Drive, Calgary, AB T2N 1N4, Canada AU: Koonin, S E EM: [EMAIL PROTECTED] AF: BP p.l.c., 1 St. James's Square, London, SW1Y 4PD, United Kingdom AU: Patrinos, A A EM: [EMAIL PROTECTED] AF: Synthetic Genomics, 901 D Street SW Suite 900, Washington, DC 20024, United States AU: Schrag, D P EM: [EMAIL PROTECTED] AF: Harvard University, 20 Oxford Street, Cambridge, MA 02138, United States AU: Socolow, R H EM: [EMAIL PROTECTED] AF: Princeton University, Engineering Quad D-Wing, Princeton, NJ 08544, United States AB: Through a one-week intensive study, the authors of this abstract explored the question: What program of comprehensive technical research over the next decade would maximally reduce the uncertainties associated with climate engineering responses to climate emergencies? The motivations underlying this question, our group's focus on climate engineering concepts for manipulating incident short-wave solar radiation, and our in-depth consideration of stratospheric aerosol interventions as a case example are all described in a previous presentation (Keith et al. in this session). This second of two presentations on our study group's findings concentrates specifically on our technical evaluation of the issues associated with climate impact detection and attribution. Our analyses begin by examining the natural variability (noise) and equilibration timescales (temporal response) of a number of specific climate parameters (e.g. surface radiative flux, surface temperature, atmospheric ozone concentrations, etc.) at both the global and regional scales. First, using the assumption of immediate response for all climate parameters, order-of-magnitude signal-to-noise ratio calculations are used to estimate the minimum intervention durations and amplitudes needed for climate impacts of predicted magnitude to be attributably detected. Next, a number of relevant processes (physical, chemical and biological) within the climate system are evaluated to provide order-of-magnitude estimates for the actual temporal response of these climate parameters (e.g. delay in global temperature response due to ocean heat capacity). Cumulatively, these first-order quantitative estimates reveal a number of basic limits to the timescale over which equilibrium climatic parameter impacts of a climate engineering intervention could be detected. Building from these basic results, we examine current climate monitoring capabilities across four broad categories of climate parameters: (1) radiative; (2) geophysical; (3) geochemical; and (4) ecological. The utility of present monitoring capabilities (e.g. the AeroNet network and ARM) for field-tests are considered, including the proposal and quantitative evaluation of methods for achieving maximal understanding from minimal amplitude tests (e.g. intermittent interventions with phase-sensitive "lock-in" detection methods to maximize sensitivity). Finally, large gaps between current monitoring capabilities and the basic detection limits are identified in each of these categories, and new detection systems are proposed to fill those gaps. DE: 1600 GLOBAL CHANGE DE: 1605 Abrupt/rapid climate change (4901, 8408) DE: 1699 General or miscellaneous SC: Union [U] MN: 2008 Fall Meeting [Comments. This is the meeting where one of the modelers said he was opposed to field tests. Trade him to the Red Team! Although most of this is too vague to comment on, few conclusions are given, I would agree that there will be some difficulty in detecting changes in climate or weather from geoengineering until a certain threshold is reached, not just because the climate doesn't react to low levels of changes in forcing, but because we also lack the ability to detect them. Example: the volcanic eruption of Soufriere Hills in Montserrat in 2006 injected 45,000 tons of S into the Overworld stratosphere that was picked up by the Brewer-Dobson circulation about 2 weeks later half way around the world. U.S. monitoring satellites were able to detect and follow the cloud of SO2 as it slowly oxidized into sulfuric acid, but once it was caught by the B-D, it was quickly dispersed and lost by the satellites. No climatic changes were observable as a result. So how big would a field experiment have to be to have a measurable impact on global radiative forcing and on climate? Very big. Detection of aerosol would be less of a problem. Remnants from Pinatubo were found 5 years later. So measuring chemicals and measuring the impact of those chemicals, like in environmental monitoring in general are two different disciplines. I think it unlikely that the sensitivity of detection systems for any of the parameters of interest will improve significantly over the next decade. Adding more monitors will help, however. Bottom line: we will have to make do with what we got, which ain't a lot. AG] --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
