01_Some_Geoengineeri...doc

record 1 of 16author(s): katz, ji (katz, jonathan isaac)title: stratospheric albedo modificationsource: energy & environmental science, 3 (11): 1634-1644 2010abstract: the possibility of offsetting greenhouse gas warming by introducing artificial aerosols into the stratosphere to increase the earths albedo has been widely discussed, but little attention has been given to the details of its implementation. it is usually assumed that the aerosols would be sulfuric acid droplets (hydrated sulfur trioxide), like natural volcanic aerosols. other materials may be more advantageous, but sophisticated engineered particles probably cannot be produced in sufficient quantity. i consider a variety of possible injection vehicles. aircraft are unlikely to have sufficient lift capability to the necessary altitudes, guns are inefficient, and exotic methods like balloons and chimneys face daunting difficulties. simple rockets are proven and economical, and can deliver material to any desired altitude. artificial injection begins at a much higher aerosol (or precursor) density than a volcanic plume, raising novel issues of chemical kinetics and particle agglomeration. detailed experimental and theoretical investigation are required to establish the feasibility of stratospheric aerosol geoengineering. an appendix argues that natural, as well as anthropogenic, climate change may pose challenges that could be met by these methods.doi: 10.1039/c002441drecord 2 of 16author(s): cokinos, c (cokinos, christopher)title: prozac for the planet : can geoengineering make the climate happy again?source: american scholar, 79 (4): 20-33 fal 2010record 3 of 16author(s): moore, jc (moore, j. c.); jevrejeva, s (jevrejeva, s.); grinsted, a (grinsted, a.)title: efficacy of geoengineering to limit 21st century sea-level risesource: proceedings of the national academy of sciences of the united states of america, 107 (36): 15699-15703 sep 7 2010abstract: geoengineering has been proposed as a feasible way of mitigating anthropogenic climate change, especially increasing global temperatures in the 21st century. the two main geoengineering options are limiting incoming solar radiation, or modifying the carbon cycle. here we examine the impact of five geoengineering approaches on sea level; so2 aerosol injection into the stratosphere, mirrors in space, afforestation, biochar, and bioenergy with carbon sequestration. sea level responds mainly at centennial time scales to temperature change, and has been largely driven by anthropogenic forcing since 1850. making use a model of sea-level rise as a function of time-varying climate forcing factors (solar radiation, volcanism, and greenhouse gas emissions) we find that sea-level rise by 2100 will likely be 30 cm higher than 2000 levels despite all but the most aggressive geoengineering under all except the most stringent greenhouse gas emissions scenarios. the least risky and most desirable way of limiting sea-level rise is bioenergy with carbon sequestration. however aerosol injection or a space mirror system reducing insolation at an accelerating rate of 1 wm(-2) per decade from now to 2100 could limit or reduce sea levels. aerosol injection delivering a constant 4 wm(-2) reduction in radiative forcing (similar to a 1991 pinatubo eruption every 18 months) could delay sea-level rise by 40-80 years. aerosol injection appears to fail cost-benefit analysis unless it can be maintained continuously, and damage caused by the climate response to the aerosols is less than about 0.6% global world product.doi: 10.1073/pnas.1008153107record 4 of 16author(s): korhonen, h (korhonen, h.); carslaw, ks (carslaw, k. s.); romakkaniemi, s (romakkaniemi, s.)title: enhancement of marine cloud albedo via controlled sea spray injections: a global model study of the influence of emission rates, microphysics and transportsource: atmospheric chemistry and physics, 10 (9): 4133-4143 2010abstract: modification of cloud albedo by controlled emission of sea spray particles into the atmosphere has been suggested as a possible geoengineering option to slow global warming. previous global studies have imposed changes in cloud drop concentration in low level clouds to explore the radiative and climatic effects. here, we use a global aerosol transport model to quantify how an imposed flux of sea spray particles affects the natural aerosol processes, the particle size distribution, and concentrations of cloud drops. we assume that the proposed fleet of vessels emits sea spray particles with a wind speed-dependent flux into four regions of persistent stratocumulus cloud off the western coasts of continents. the model results show that fractional changes in cloud drop number concentration (cdnc) vary substantially between the four regions because of differences in wind speed (which affects the spray efficiency of the vessels), transport and particle deposition rates, and because of variations in aerosols from natural and anthropogenic sources. using spray emission rates comparable to those implied by previous studies we find that the predicted cdnc changes are very small (maximum 20%) and in one of the four regions even negative. the weak or negative effect is because the added particles suppress the in-cloud supersaturation and prevent existing aerosol particles from forming cloud drops. a scenario with five times higher emissions (considerably higher than previously assumed) increases cdnc on average by 45-163%, but median concentrations are still below the 375 cm(-3) assumed in previous studies. an inadvertent effect of the spray emissions is that sulphur dioxide concentrations are suppressed by 1-2% in the seeded regions and sulphuric acid vapour by 64-68% due to chemical reactions on the additional salt particles. the impact of this suppression on existing aerosol is negligible in the model, but should be investigated further in the real environment so that inadvertent impacts can be excluded.doi: 10.5194/acp-10-4133-2010record 5 of 16author(s): greene, ch (greene, charles h.); baker, dj (baker, d. james); miller, dh (miller, daniel h.)title: a very inconvenient truthsource: oceanography, 23 (1): 214-218 sp. iss. si mar 2010abstract: studies conducted after those that contributed to the intergovernmental panel on climate change (ipcc) fourth assessment report (far) suggest that human society may be facing a very inconvenient truth-that emission reduction efforts alone are unlikely to stabilize greenhouse gas concentrations at levels low enough to prevent dangerous anthropogenic interference with the climate system. here, we discuss reasons why the ipcc process is prone to underestimating the threats of global climate change. we then review some of the critical policy-relevant scientific findings that have emerged since the release of the ipcc far. finally, we discuss how these new findings fundamentally transform the debate on efforts needed to prevent dangerous changes to our climate system. it now appears that to avoid such changes, society will likely need to adopt a mixed strategy of reducing greenhouse gas emissions and employing geoengineering approaches that extract carbon dioxide from the atmosphere and/or reduce the level of incoming solar radiation reaching earths surface.record 6 of 16author(s): macmynowski, dg (macmynowski, douglas g.)title: can we control el nino?source: environmental research letters, 4 (4): art. no. 045111 oct-dec 2009abstract: the question of whether it is possible to intentionally modify the el nino/southern oscillation (enso) cycle is explored as a case study in the dynamics of climate intervention beyond simple temperature adjustment. a plausible control strategy is described, including an estimate of the energy it would require to implement. the intent here is not to suggest that we should do so, but rather that the scale of the required intervention is such that we could intentionally influence enso. simulations use the cane-zebiak intermediate complexity model, and demonstrate that depending on the parameter regime, a feedback strategy that dynamically deflects less than 1% of the sunlight over the nino-3 region of the eastern tropical pacific could be used to reduce the probability of extreme enso events (t 2 degrees c) to near zero, or conversely to enhance the cycle.article number: 045111doi: 10.1088/1748-9326/4/4/045111record 7 of 16author(s): strong, al (strong, aaron l.); cullen, jj (cullen, john j.); chisholm, sw (chisholm, sallie w.)title: ocean fertilization science, policy, and commercesource: oceanography, 22 (3): 236-261 sp. iss. si sep 2009abstract: over the past 20 years there has been growing interest in the concept of fertilizing the ocean with iron to abate global warming. this interest was catalyzed by basic scientific experiments showing that iron limits primary production in certain regions of the ocean. the approach-considered a form of geoengineering-is to induce phytoplankton blooms through iron addition, with the goal of producing organic particles that sink to the deep ocean, sequestering carbon from the atmosphere. with the controversy surrounding the most recent scientific iron fertilization experiment in the southern ocean (lohafex) and the ongoing discussion about restrictions on large-scale iron fertilization activities by the london convention, the debate about the potential use of iron fertilization for geoengineering has never been more public or more pronounced. to help inform this debate, we present a synoptic view of the two-decade history of iron fertilization, from scientific experiments to commercial enterprises designed to trade credits for ocean fertilization on a developing carbon market. throughout these two decades there has been a repeated cycle: scientific experiments are followed by media and commercial interest and this triggers calls for caution and the need for more experiments. over the years, some scientists have repeatedly pointed out that the idea is both unproven and potentially ecologically disruptive, and models have consistently shown that at the limit, the approach could not substantially change the trajectory of global warming. yet, interest and investment in ocean fertilization as a climate mitigation strategy have only grown and intensified, fueling media reports that have misconstrued scientific results, and conflated scientific experimentation with geoengineering. we suggest that it is time to break this two-decade cycle, and argue that we know enough about ocean fertilization to say that it should not be considered further as a means to mitigate climate change. but, ocean fertilization research should not be halted: if used appropriately and applied to testable hypotheses, it is a powerful research tool for understanding the responses of ocean ecosystems in the context of climate change.record 8 of 16author(s): lovelock, j (lovelock, james)title: a geophysiologists thoughts on geoengineeringsource: philosophical transactions of the royal society a-mathematical physical and engineering sciences, 366 (1882): 3883-3890 nov 13 2008abstract: the earth is now recognized as a self-regulating system that includes a reactive biosphere; the system maintains a long-term steady-state climate and surface chemical composition favourable for life. we are perturbing the steady state by changing the land surface from mainly forests to farm land and by adding greenhouse gases and aerosol pollutants to the air. we appear to have exceeded the natural capacity to counter our perturbation and consequently the system is changing to a new and as yet unknown but probably adverse state. i suggest here that we regard the earth as a physiological system and consider amelioration techniques, geoengineering, as comparable to nineteenth century medicine.doi: 10.1098/rsta.2008.0135record 9 of 16author(s): rasch, pj (rasch, philip j.); tilmes, s (tilmes, simone); turco, rp (turco, richard p.); robock, a (robock, alan); oman, l (oman, luke); chen, cc (chen, chih-chieh (jack); stenchikov, gl (stenchikov, georgiy l.); garcia, rr (garcia, rolando r.)title: an overview of geoengineering of climate using stratospheric sulphate aerosolssource: philosophical transactions of the royal society a-mathematical physical and engineering sciences, 366 (1882): 4007-4037 nov 13 2008abstract: we provide an overview of geoengineering by stratospheric sulphate aerosols. the state of understanding about this topic as of early 2008 is reviewed, summarizing the past 30 years of work in the area, highlighting some very recent studies using climate models, and discussing methods used to deliver sulphur species to the stratosphere. the studies reviewed here suggest that sulphate aerosols can counteract the globally averaged temperature increase associated with increasing greenhouse gases, and reduce changes to some other components of the earth system. there are likely to be remaining regional climate changes after geoengineering, with some regions experiencing significant changes in temperature or precipitation. the aerosols also serve as surfaces for heterogeneous chemistry resulting in increased ozone depletion. the delivery of sulphur species to the stratosphere in a way that will produce particles of the right size is shown to be a complex and potentially very difficult task. two simple delivery scenarios are explored, but similar exercises will be needed for other suggested delivery mechanisms. while the introduction of the geoengineering source of sulphate aerosol will perturb the sulphur cycle of the stratosphere signicantly, it is a small perturbation to the total (stratosphere and troposphere) sulphur cycle. the geoengineering source would thus be a small contributor to the total global source of acid rain that could be compensated for through improved pollution control of anthropogenic tropospheric sources. some areas of research remain unexplored. although ozone may be depleted, with a consequent increase to solar ultraviolet-b (uvb) energy reaching the surface and a potential impact on health and biological populations, the aerosols will also scatter and attenuate this part of the energy spectrum, and this may compensate the uvb enhancement associated with ozone depletion. the aerosol will also change the ratio of diffuse to direct energy reaching the surface, and this may influence ecosystems. the impact of geoengineering on these components of the earth system has not yet been studied. representations for the formation, evolution and removal of aerosol and distribution of particle size are still very crude, and more work will be needed to gain confidence in our understanding of the deliberate production of this class of aerosols and their role in the climate system.doi: 10.1098/rsta.2008.0131record 10 of 16author(s): lunt, dj (lunt, d. j.); ridgwell, a (ridgwell, a.); valdes, pj (valdes, p. j.); seale, a (seale, a.)title: sunshade world: a fully coupled gcm evaluation of the climatic impacts of geoengineeringsource: geophysical research letters, 35 (12): art. no. l12710 jun 25 2008abstract: sunshade geoengineering - the installation of reflective mirrors between the earth and the sun to reduce incoming solar radiation, has been proposed as a mitigative measure to counteract anthropogenic global warming. although the popular conception is that geoengineering can re-establish a natural pre-industrial climate, such a scheme would itself inevitably lead to climate change, due to the different temporal and spatial forcing of increased co2 compared to reduced solar radiation. we investigate the magnitude and nature of this climate change for the first time within a fully coupled general circulation model. we find significant cooling of the tropics, warming of high latitudes and related sea ice reduction, a reduction in intensity of the hydrological cycle, reduced enso variability, and an increase in atlantic overturning. however, the changes are small relative to those associated with an unmitigated rise in co2 emissions. other problems such as ocean acidification remain unsolved by sunshade geoengineering.article number: l12710doi: 10.1029/2008gl033674record 11 of 16author(s): bala, g (bala, g.); duffy, pb (duffy, p. b.); taylor, ke (taylor, k. e.)title: impact of geoengineering schemes on the global hydrological cyclesource: proceedings of the national academy of sciences of the united states of america, 105 (22): 7664-7669 jun 3 2008abstract: the rapidly rising co2 level in the atmosphere has led to proposals of climate stabilization by geoengineering schemes that would mitigate climate change by intentionally reducing solar radiation incident on earths surface. in this article we address the impact of these climate stabilization schemes on the global hydrological cycle. by using equilibrium climate simulations, we show that insolation reductions sufficient to offset global-scale temperature increases lead to a decrease in global mean precipitation. this occurs because solar forcing is more effective in driving changes in global mean evaporation than is co2 forcing of a similar magnitude. in the model used here, the hydrological sensitivity, defined as the percentage change in global mean precipitation per degree warming, is 2.4% k-1 for solar forcing, but only 1.5% k-1 for co2 forcing. although other models and the climate system itself may differ quantitatively from this result, the conclusion can be understood based on simple considerations of the surface energy budget and thus is likely to be robust. for the same surface temperature change, insolation changes result in relatively larger changes in net radiative fluxes at the surface; these are compensated by larger changes in the sum of latent and sensible heat fluxes. hence, the hydrological cycle