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Home , Alan Robock, Climate engineering, Future of Earth

Vol. 64, No. 2, p. 14-18, 59 DOI: 10.2968/064002006

20 reasons why geoengineering may be a bad idea dioxide emissions are rising so fast that some scientists are seriously ­considering putting on support as a last resort. But is this cure worse than the disease?

By

he stated objective of the aerosols into the as a means trigger algal blooms; genetic modifica- 1992T U.N. Framework Convention on Cli- to block and cool Earth. Another tion of crops to increase biotic carbon mate Change is to stabilize greenhouse respected scientist, Tom Wigley, uptake; carbon capture and storage tech- gas concentrations in the “at followed up with a feasibility study in Sci- niques such as those proposed to outfit a level that would prevent dangerous an- ence that advocated the same approach in coal ; and planting forests are such thropogenic interference with the climate combination with emissions reduction.1 examples. Other schemes involve block- system.” Though the framework conven- The idea of geoengineering traces its ing or reflecting incoming solar radia- tion did not define “dangerous,” that level genesis to military strategy during the tion, for example by spraying is now ­generally considered to be about early years of the Cold War, when sci- hundreds of meters into the air to seed 450 parts per million (ppm) of carbon di- entists in the United States and the So- the formation of stratocumulus oxide in the atmosphere; the current con- viet Union devoted considerable funds over the subtropical .3 centration is about 385 ppm, up from 280 and research efforts to controlling the Two strategies to reduce incom- ppm before the . . Some early geoengineering ing solar —stratospheric aero- In light of society’s failure to act con- theories involved damming the Strait sol injection as proposed by Crutzen certedly to deal with global warming in of Gibraltar and the Bering Strait as a and -based shields (i.e., mir- spite of the framework convention agree- way to warm the Arctic, making rors or shades placed in orbit between ment, two prominent atmospheric sci- more habitable.2 Since scientists became the sun and Earth)—are among the entists recently suggested that humans aware of rising concentrations of atmo- most ­widely discussed geoengineering consider geoengineering—in this case, spheric , however, some schemes in scientific circles. While these deliberate modification of the climate to have proposed artificially altering cli- schemes (if they could be built) would achieve specific effects such as cooling— mate and weather patterns to reverse or cool Earth, they might also have adverse to address global warming. Nobel laure- mask the effects of global warming. ­consequences. Several papers in the Au- ate Paul Crutzen, who is well regarded Some geoengineering schemes aim to gust 2006 ­Climatic Change discussed for his work on ozone damage and nucle- remove carbon dioxide from the atmo- some of these issues, but here I present a ar winter, spearheaded a special August sphere, through natural or mechanical ­fairly comprehensive list of reasons why 2006 issue of ­Climatic Change with a con- means. Ocean fertilization, where iron geoengineering might be a bad idea, first

troversial editorial about injecting sulfate dust is dumped into the open ocean to written down during a two-day NASA- J O N HAN

14 Bulletin of the Atomic Scientists MAY/JUNE 2008 sponsored conference on Managing Solar shown large impacts on regional climate, geoengineering schemes and found that Radiation (a rather audacious title) in No- but whether these are good analogs for they reduced precipitation over wide re- vember 2006.4 These concerns address the geoengineering response requires gions, condemning hundreds of millions unknowns in response; ef- further investigation. of people to . fects on human quality of life; and the po- Scientists have also seen volcanic 2. Continued . litical, ethical, and moral issues raised. eruptions in the tropics produce ­changes If humans adopted geoengineering as in atmospheric circulation, causing win- a solution to global warming, with no ter warming over in the restriction on continued carbon emis- 1. Effects on regional climate. Geo- Northern Hemisphere, as well as erup- sions, the ocean would continue to be- proponents often suggest tions at high weaken the Asian come more acidic, because about half of that volcanic eruptions are an innocuous and African monsoons, causing reduced all excess carbon dioxide in the atmo- natural analog for stratospheric injection precipitation.6 In fact, the eight-month- sphere is removed by ocean uptake. The of sulfate aerosols. The 1991 eruption of long eruption of the Laki fissure in Ice- ocean is already 30 percent more acidic Mount Pinatubo on the Philippine is- land in 1783–1784 contributed to famine than it was before the Industrial Revolu- land of Luzon, which injected 20 mega- in , India, and Japan. tion, and continued acidification threat- tons of gas into the strato- If scientists and engineers were able to ens the entire oceanic biological chain, sphere, produced a sulfate aerosol inject smaller amounts of stratospheric from coral reefs right up to humans.7 that is said to have caused global cool- aerosols than result from volcanic erup- 3. . Aerosol ing for a couple of years without adverse tions, how would they affect summer in the stratosphere serve as surfaces for effects. However, researchers at the Na- and precipitation patterns? Could chemical reactions that destroy ozone in tional Center for Atmospheric Research attempts to geoengineer isolated regions the same way that water and nitric acid showed in 2007 that the Pinatubo erup- (say, the Arctic) be confined there? Sci- aerosols in polar ­stratospheric clouds tion caused large hydrological respons- entists need to investigate these scenari- produce the seasonal Antarctic ozone es, including reduced precipitation, soil os. At the fall 2007 American ­Geophysical hole.8 For the next four decades or so, moisture, and river flow in many re- Union meeting, researchers presented when the concentration of anthropo- gions.5 Simulations of the climate re- preliminary findings from several dif- genic ozone-depleting substances will sponse to volcanic eruptions have also ferent climate models that ­simulated still be large enough in the stratosphere

MAY/JUNE 2008 Bulletin of the Atomic Scientists 15 impact of in urban areas, but in capitalizing on carbon pristine areas it could be significant. 6. Effects of cirrus clouds. As aerosol ithout market incentives, geoengineering schemes to reflect solar heat are particles injected into the stratosphere still largely confined to creative thought and artists’ renderings. But a few fall to Earth, they may seed cirrus cloud W ambitious entrepreneurs have begun to experiment with privatizing climate formations in the .11 Cirrus mitigation through . Here are a few companies in the market to clouds affect Earth’s radiative balance offset your : of incoming and outgoing heat, although California-based startups Planktos and Climos are perhaps the most the amplitude and even direction of the prominent groups offering to sell carbon offsets in exchange for performing ocean effects are not well understood. While iron fertilization, which induces blooms of carbon-eating . Funding for evidence exists that some volcanic aero- Planktos dried up in early 2008 as scientists grew increasingly skeptical about the sols form cirrus clouds, the global effect technique, but Climos has managed to press on, securing $3.5 million in funding from has not been quantified.12 Braemar Ventures as of February. 7. Whitening of the sky (but nice Also in the research and development phase is Sydney, –based Ocean sunsets). Atmospheric aerosols close to Nourishment Corporation, which similarly aims to induce oceanic , only the size of the wavelength of light produce it fertilizes with -rich urea instead of iron. Atmocean, based in Santa Fe, New a white, cloudy appearance to the sky. Mexico, takes a slightly different tack: It’s developed a 200-meter deep, wave-powered They also contribute to colorful sunsets, pump that brings colder, more biota-rich water up to the surface where lifeforms such similar to those that occur after volcanic as tiny, tube-like salps sequester carbon as they feed on algae. eruptions. The red and yellow sky in The Related in mission if not in name, stationary carbon-capture , which Scream by Edvard Munch was inspired generally aren’t considered geoengineering, are nonetheless equally inventive: ­Skyonic, by the brilliant sunsets he witnessed over a ­Texas-based startup, captures carbon dioxide at power plants (a relatively well- Oslo in 1883, following the eruption of ­proven technology) and mixes it with sodium hydroxide to render high-grade baking Krakatau in .13 Both the disap- soda. A pilot version of the system is operating at the Brown Stream Electric Station pearance of blue skies and the appearance in Fairfield, Texas. To the west in Tucson, Arizona, Global Research Technologies, the of red sunsets could have strong psycho- only company in the dedicated to carbon capture from ambient air, recently dem- logical impacts on humanity. onstrated a working “air extraction” prototype—a kind of carbon dioxide vacuum that 8. Less sun for solar power. Scien- stands upright and is about the size of a phone booth. Meanwhile, GreenFuel Technol- tists estimate that as little as a 1.8 ­percent ogies Corporation, in collaboration with Arizona Public Service Company, is reduction in incoming solar radiation carbon dioxide emissions from power plants by using it to grow stock in the would compensate for a doubling of at- form of—what else?—algae. KIRSTEN JERCH mospheric carbon dioxide. Even this small reduction would significantly affect the radiation available for solar power to produce this effect, additional aero- 5. More acid deposition. If sulfate is systems—one of the prime alternate sols from geoengineering would destroy injected regularly into the stratosphere, methods of generating clean energy— even more ozone and increase damaging no where on Earth, acid deposi- as the response of different solar power flux to Earth’s surface. tion will increase as the material pass- systems to total available sunlight is not 4. Effects on plants. Sunlight scat- es through the troposphere—the atmo- linear. This is especially true for some ters as it passes through ­stratospheric spheric layer closest to Earth’s surface. of the most efficiently designed systems aerosols, reducing direct solar radia- In 1977, Russian climatologist Mikhail that reflect or focus direct solar radiation tion and increasing diffuse radiation, Budyko calculated that the additional on one location for direct heating.14 Fol- with important biological ­consequences. acidity caused by sulfate injections would lowing the Mount Pinatubo eruption and Some studies, including one that mea- be negligibly greater than levels that re- the 1982 eruption of El Chichón in Mex- sured this effect in trees following the sulted from air pollution.10 But the rele- ico, scientists observed a direct solar ra- Mount Pinatubo eruption, suggest that vant quantity is the total amount of acid diation decrease of 25–35 percent.15 diffuse radiation allows canopies that reaches the ground, including both 9. Environmental impacts of im- to photosynthesize more efficiently, wet (acid , , and fog) and dry de- plementation. Any system that could thus increasing their capacity as a car- position (acidic gases and particles). Any inject aerosols into the stratosphere, i.e., bon sink.9 At the same , inserting additional acid deposition would harm commercial jetliners with sulfur mixed aerosols or reflective disks into the at- the , and it will be important to into their fuel, 16-inch naval rifles firing mosphere would reduce the total sun- understand the consequences of exceed- 1-ton shells of dust vertically into the air, light to reach Earth’s surface. Scientists ing ­different ­biological thresholds. Fur- or hoses suspended from stratospheric need to assess the impacts on crops and thermore, more acidic particles in the tro- balloons, would cause enormous envi- natural vegetation of reductions in total, posphere would affect public health. The ronmental damage. The same could be diffuse, and direct solar radiation. effect may not be large compared to the said for systems that would deploy sun

16 Bulletin of the Atomic Scientists MAY/JUNE 2008 shields. University of Arizona astrono- (Boston’s “Big Dig” to reroute an inter- and environmental effects of a given mer Roger P. Angel has proposed put- state highway under the coastal city, geoengineering project, and political ting a fleet of 2-foot-wide reflective disks one of humankind’s greatest engineering leaders could muster the public support in a stable orbit between Earth and the feats, is only one example that was years and funding to implement it, how would sun that would bend sunlight away from overdue and billions over budget.) Angel the world agree on the optimal cli- Earth.16 But to get the needed trillions of estimates that his scheme to launch re- mate? What if Russia wants it a couple disks into space, engineers would need flective disks into orbit would cost “a few of ­degrees warmer, and India a couple 20 electromagnetic launchers to fire mis- trillion dollars.” British economist Nich- of degrees cooler? Should global climate siles with stacks of 800,000 disks every olas Stern’s calculation of the cost of cli- be reset to preindustrial temperature or five minutes for twenty years. What mate change as a percentage of global kept constant at today’s reading? Would would be the atmospheric effects of the GDP (roughly $9 trillion) is in the same it be possible to tailor the climate of resulting sound and gravity waves? Who ballpark; Angel’s estimate is also orders each region of the planet independent- would want to live nearby? of magnitude greater than current glob- ly without affecting the others? If we 10. Rapid warming if deployment al investment in tech- ­proceed with geoengineering, will we stops. A technological, societal, or po- nology. Wouldn’t it be a safer and wiser provoke climate wars? litical crisis could halt a project of investment for society to instead put that 19. Questions of moral ­authority. stratospheric aerosol injection in mid- money in solar power, wind power, ener- Ongoing global warming is the result of ­deployment. Such an abrupt shift would gy efficiency, and carbon sequestration? inadvertent climate modification. Hu- result in rapid climate warming, which 15. Commercial control of technolo- mans emit carbon dioxide and other would produce much more stress on gy. Who would end up controlling geoen- greenhouse gases to heat and cool their society and than gradual gineering systems? Governments? Private homes; to grow, transport, and cook ­global warming.17 companies holding patents on proprietary their food; to run their factories; and to 11. There’s no going back. We don’t technology? And whose benefit would ­travel—not intentionally, but as a by- know how quickly scientists and engi- they have at heart? These systems could product of combustion. But neers could shut down a geoengineer- pose issues analogous to those raised by now that humans are aware of their ef- ing system—or stem its effects—in pharmaceutical companies and energy fect on climate, do they have a moral the event of excessive climate cooling conglomerates whose products ostensi- right to continue emitting greenhouse from large volcanic eruptions or other bly serve the public, but who often value gases? Similarly, since scientists know causes. Once we put aerosols into the shareholder profits over the . that stratospheric aerosol injection, for ­atmosphere, we cannot remove them. 16. Military use of the technolo- example, might impact the ecosphere, 12. Human error. Complex mechan- gy. The United States has a long history do humans have a right to plow ahead ical systems never work perfectly. Hu- of trying to modify weather for military regardless? There’s no global agency to mans can make mistakes in the de- purposes, including inducing rain during require an environmental impact state- sign, , and operation of the Vietnam War to swamp North Viet- ment for geoengineering. So, how should such systems. (Think of Chernobyl, namese supply lines and disrupt ­antiwar humans judge how much climate control the Exxon Valdez, airplane crashes, and protests by Buddhist monks.19 Eighty-five they may try? friendly fire on the battlefield.) Should countries, including the United States, 20. Unexpected consequences. Sci- we stake the on a much have signed the U.N. Convention on the entists cannot possibly account for all of more complicated arrangement than Prohibition of Military or Any Other Hos- the complex climate interactions or pre- these, built by the lowest bidder? tile Use of Environmental Modification dict all of the impacts of geoengineer- 13. Undermining emissions ­miti- Techniques (ENMOD), but could tech- ing. Climate models are improving, but gation. If humans perceive an easy tech- niques developed to control global cli- scientists are discovering that climate is nological fix to global warming that al- mate forever be limited to peaceful uses? changing more rapidly than they predict- lows for “business as usual,” gathering 17. Conflicts with current treaties. ed, for example, the surprising and un- the national (particularly in the United The terms of ENMOD explicitly prohib- precedented extent to which Arctic sea States and China) and international will it “military or any other hostile use of ice melted during the summer of 2007. to change consumption patterns and en- environmental modification techniques Scientists may never have enough confi- ergy infrastructure will be even more dif- having widespread, long-lasting or se- dence that their theories will predict how ficult.18 This is the oldest and most persis- vere effects as the means of ­destruction, well geoengineering systems can work. tent argument against geoengineering. ­damage, or injury to any other State With so much at stake, there is reason to 14. Cost. Advocates casually claim Party.” Any geoengineering scheme that worry about what we don’t know. that it would not be too expensive to adversely affects regional climate, for ex- ­implement geoengineering solutions, but ample, producing warming or drought, there have been no definitive cost stud- would therefore violate ENMOD. The reasons why geoengineering ies, and estimates of large-scale govern- 18. Control of the thermostat. Even may be a bad idea are manifold, though ment projects are almost always too low. if scientists could predict the ­behavior a moderate investment in theoretical

MAY/JUNE 2008 Bulletin of the Atomic Scientists 17 geoengineering research might help scien- an EtHical aSSESSMEnt oF gEoEnginEEring tists to determine whether or not it is a bad idea. Still, it’s a slippery slope: I wouldn’t hile there are many questions about the feasibility, cost, and effectiveness advocate actual small-scale stratospher- of geoengineering plans, my colleague Alan robock has been the most sys- ic experiments unless comprehensive cli- Wtematic and persistent of a number of scientists in raising ethical quandaries mate modeling results could first show about the enterprise. But just how serious are these ethical quandaries? that we could avoid at least all of the po- Most science poses risks of , and lots of science raises tential consequences we know about. issues of commercial and military control. At issue here is whether there is any reason Due to the inherent natural variability of to believe ex ante that these are special or unusually large risks. Merely asserting them the climate system, this task is not trivi- does not ground an objection per se. al. After that there are still the unknowns, Not all of robock’s concerns involve ethics, but of those that do, some involve issues such as the long-term effects of short-term of procedural justice (such as who decides) while others involve of distributive experiments—stratospheric aerosols have justice (such as uneven benefit and harm). To simplify things, let’s assume that inject- an atmospheric lifetime of a couple years. ing aerosols into the stratosphere successfully cooled Earth without any untoward ef- Solving global warming is not a difficult fects and with evenly distributed benefits. one might still object that there are issues of technical problem. As Stephen Pacala and procedural justice involved—who decides and who controls. But such concerns don’t Robert Socolow detail with their popular get much traction when everyone benefits. wedge model, a combination of several let’s pull back from this idealization to imagine an outcome that involves untoward specific actions can stabilize the world’s consequences and an uneven distribution of benefits. We deal with consequences by emissions—although I balancing them against the benefits of our interventions. The issue is whether or not we disagree with their proposal to use nu- can obtain reliable estimates of both risks and benefits without full-scale implementa- clear power as one of their “wedges.”20 tion of the planned intervention. We already know from modeling that the impact of any Instead, the crux of addressing glob- such intervention will be uneven, but again, without knowing what the distribution of ben- al warming is political. The U.S. govern- efit and harm would be, it’s hard to estimate how much this matters. let’s differentiate ment gives multibillion- dollar subsidies two circumstances under which going ahead with the intervention might be judged: one to the coal, oil, gas, and nuclear indus- is where everyone benefits, while the other is a circumstance in which something less tries, and gives little support to alterna- is the case. A conservative conclusion would be to say that beyond modeling and con- tive energy sources like solar and wind trolled, low-level tests (if the modeling justifies it), we shouldn’t sanction any large-scale power that could contribute to a solu- interventions unless they are in everyone’s interest. A slightly eased condition, proposed tion. Similarly, the federal government is by the philosopher Dale Jamieson, would be that at least nobody is worse off. That may squashing attempts by states to mandate not be as farfetched a condition as one might think, since, in the end, we are considering emissions reductions. If global warm- this intervention as a means to balance a risk we all face—global warming. ing is a political problem more than it is But suppose there are isolated livelihoods that only suffer negative effects of geoen- a technical problem, it follows that we gineering. Then numbers begin to matter. In the case that a geoengineering scheme don’t need geoengineering to solve it. were to harm the few, we should have the foresight to be able to compensate, even if The U.N. Framework Convention on doing so requires something as drastic as relocating populations. I don’t mean to over- defines “dangerous an- simplify a complicated issue, but objection to any negative consequences whatsoever thropogenic interference” as inadvertent isn’t a strong enough argument to end discussion. climate effects. However, states must also More trenchant is the worry that the mere possibility of geoengineering would un- carefully consider geoengineering in their dermine other efforts to decrease our carbon output. Such is a familiar pledge to prevent dangerous anthropogen- worry, and we don’t let it stop us in other areas: Antilock braking systems and airbags ic interference with the climate system.  may cause some to drive more recklessly, but few would let that argument outweigh For NoTES, PlEASE SEE P. 59. the overwhelming benefits of such safety features. Alan Robock is director of the under- As robock correctly asserts, the crux of addressing global warming may be a graduate program and associate director of the Center political—not a scientific—problem, but it doesn’t follow that we may not need geoen- for Environmental Prediction in the Department of En- gineering to solve it. If it is a political problem, it is a global political problem, and getting vironmental Sciences at . This work global agreement to curb greenhouse gases is easier said than done. is supported by the National Science Foundation. With geoengineering, in principle, one nation or agent could act, but a challenge arises

if the intervention is certain to have uneven impacts among nations. At this early stage, WWW.tHEbUllEtin.org there is no cost associated with improving our ability to quantify and describe what those inequalities would look like. once we have those answers in hand, then we can engage in our coverage continues online. serious ethical consideration over whether or not to act. MArTIN BUNZl Visit the www.thebulletin.org for an extended discussion of Martin Bunzl is a professor of philosophy at Rutgers University. a geoengineering research agenda.

18 Bulletin of the Atomic ScientiStS MAY/JUNE 2008 NOTES

­Hydrological Cycle as an Analog of Geoengineer- solar radiation, see Balan Govindasamy and Ken 20 reasons why ing,” Geophysical Research Letters, vol. 34, no. 16, Caldeira, “Geoengineering Earth’s Radiation Bal- geoengineering may (2007). ance to Mitigate CO2-Induced Climate Change,” 6. For more on warming over continents of the Geophysical Research Letters, vol. 27, pp. 2,141–44 be a bad idea Northern Hemisphere, see Alan Robock, “Volca- (2000). For the response of solar power systems, continued from p. 18 nic Eruptions and Climate,” Reviews of Geophys- see Michael C. MacCracken, “Geoengineering: ics, vol. 38, pp. 191–219 (2000); Georgiy Stenchikov Worthy of Cautious Evaluation?” Climatic Change, 1. Paul Crutzen, “ Enhancement by et al., “Arctic Oscillation Response to Volcanic vol. 77, pp. 235–43 (2006). Stratospheric Sulfur Injections: A Contribution to Eruptions in the IPCC AR4 Climate Models,” 15. Robock, “Volcanic Eruptions and Climate,” Solve a Policy Dilemma?” Climatic Change, vol. 77, Journal of Geophysical Research, vol. 111, (2006). ­pp. 191–219. pp. 211–19 (2006); Tom M. L. Wigley, “A Combined For more on the effects of Asian and African mon- 16. Roger P. Angel, “Feasibility of Cooling the Mitigation/Geoengineering Approach to Climate soons, see Luke Oman et al., “Climatic Response Earth with a Cloud of Small Spacecraft Near the Stabilization,” Science, vol. 314, pp. 452–54 (2006). to High-­ Volcanic Eruptions,” Journal of Inner Lagrange Point (L1),” Proceedings of the Na- 2. See the chapter on climate modification Geophysical Research, vol. 110, (2005); Luke Oman tional Academy of Sciences, vol. 103, pp. 17,184–89 schemes in Spencer R. Weart, The Discovery of et al., “High-Latitude Eruptions Cast Shadow Over (2006). Global Warming (2007), available at http://www the African Monsoon and the Flow of the Nile,” 17. See Figure 1 in Wigley, “A Combined Miti- .aip.org/history/climate/RainMake.htm; a long Geophysical Research Letters, vol. 33, (2006). gation/Geoengineering Approach to Climate Sta- history of geoengineering proposals in James R. 7. Royal Society, Ocean Acidification Due to bilization,” pp. 452–54, and Figure 3 in H. Damon Fleming, “Fixing the Weather and Climate: Mili- Increasing Atmospheric Carbon Dioxide, June 30, Matthews and , “Transient Climate- tary and Civilian Schemes for Cloud Seeding and 2005, available at royalsociety.org/displaypagedoc Carbon Simulations of Planetary Geoengineer- ,” in Lisa Rosner, ed., The .asp?id=13539 ing,” Proceedings of the National Academy of Sci- (New York: Routledge, 2004), 8. Susan Solomon et al., “The Role of Aerosol ences, vol. 104, pp. 9,949–54 (2007). pp. 175–200; and James R. Fleming, “The Pathologi- Variations in Anthropogenic Ozone Depletion at 18. See for example Stephen H. Schneider, cal History of Weather and Climate Modification,” Northern Midlatitudes,” Journal of Geophysical “Earth Systems: Engineering and Management,” Historical Studies in the Physical Sciences, vol. 37, Research, vol. 101, (1996); Susan Solomon, “Strato- , vol. 409, pp. 417–19, 421 (2001), and Ralph pp. 3–25 (2006). See also N. Rusin and L. Flit, Man spheric Ozone Depletion: A Review of Concepts J. Cicerone, “Geoengineering: Encouraging Re- Versus Climate (Moscow: Peace Publishers, 1960); and History,” Reviews of , vol. 37, (1999). search and Overseeing Implementation,” Climatic Mikhail I. Budyko, Climatic Changes (Washington, 9. L. Gu et al., “Responses of Net Ecosystem Ex- Change, vol. 77, pp. 221–26 (2006). D.C.: American Geophysical Union, 1977); Ralph J. changes of Carbon Dioxide to Changes in Cloudi- 19. James R. Fleming writes eloquently about Cicerone et al., “Global Environmental Engineer- ness: Results from Two North American Decidu- the militaristic history of climate modification ing,” Nature, vol. 356, p. 472 (1992); Edward Teller ous Forests,” Journal of Geophysical Research, schemes in “The Climate Engineers,” Wilson et al., Global Warming and Ice Ages: I. Prospects for vol. 104, no. 31, pp. 421–31, 434 (1999); L. Gu et al., Quarterly, Spring 2007, pp. 46–60. See also Flem- Physics-Based Modulation of Global Change (Law- “Advantages of Diffuse Radiation for Terrestrial ing, “Fixing the Weather and Climate,” and Flem- rence Livermore National Laboratory Publication Ecosystem Productivity,” Journal of Geophysical ing, “The Pathological History of Weather and UCRL-JC-128715, 1997); David W. Keith, “Geoen- Research, vol. 107, (2002); L. Gu et al., “Response Climate Modification.” gineering the Climate: History and Prospect,” An- of a Forest to the Mount Pinatubo 20. Stephen W. Pacala and Robert Socolow, nual Review of Energy and the Environment, vol. 25, Eruption: Enhanced Photosynthesis,” Science, vol. “Stabilization Wedges: Solving the Climate Prob- pp. 245–84 (2000). 299, pp. 2,035–38 (2003). lem for the Next 50 Years with Current Technolo- 3. John Latham first raised this idea in two ar- 10. Budyko, Climatic Changes. gies,” Science, vol. 305, pp. 968–72 (2004); Alan ticles that appeared in Nature, vol. 347, no. 6291: 11. Richard P. Turco et al., “A Study of Meso- Robock, “’s Costs and Perils” (Let- “Control of Global Warming,” pp. 330–40, and spheric Rocket and Clouds Produced ter to the Editor), Physics Today, vol. 60, no. 1, p. “Effect on Global Warming of Wind-Dependent by Liquid-Fueled Rockets,” Space Solar Power 14 (2007). Aerosol Generation at the Ocean Surface,” pp. Review, vol. 3, pp. 223–34 (1982); V. A. Mohnen, 372–73 (1990). Keith Bower offers a numerical “Stratospheric Ion and Aerosol Chemistry and evaluation in “Computational Assessment of a Possible Links With Cirrus Cloud Microphysics— Proposed Technique for Global Warming Mitiga- A Critical Assessment,” Journal of Atmospheric tion Via Albedo-Enhancement of Marine Strato- Science, vol. 47, pp. 1,933–48 (1990). Climate change cumulous Clouds,” Atmospheric Research, vol. 82, 12. K. Sassen et al., “The 5–6 December 1991 pp. 328–36 (2006). FIRE IFO II Jet Stream Cirrus Case Study: Pos- and ­security 4. See Lee Lane, Ken Caldeira, Robert Chat- sible Influences of Volcanic Aerosols,” Journal of continued from p. 24 , and Stephanie Langhoff, eds., “Workshop Atmospheric Science, vol. 52, pp. 97–123 (1993). Report on Managing Solar Radiation,” NASA/ 13. D. W. Olsen et al., “When the Sky Ran Red: 1. Climate Change 2007: Summary for Pol- CP-2007-214558 (2007). The Story Behind The Scream,” Sky & Telescope, icy Makers. Contribution of Working Group 5. Kevin E. Trenberth and Aiguo Dai, “Effects February 2004, pp. 29–35. II to the Fourth Assessment Report of the of Mount Pinatubo Volcanic Eruption on the 14. For the estimate for reducing incoming

MAY/JUNE 2008 Bulletin of the Atomic Scientists 59