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Climate Intervention: Reflecting Sunlight to Cool Earth (2015)

Chapter: Appendix C: Planned Weather Modification

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Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
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APPENDIX C

Planned Weather Modification

PLANNED WEATHER MODIFICATION VERSUS CLIMATE INTERVENTION

Weather modification, which could also be called “weather intervention,” is the intentional alteration of the composition, behavior, or dynamics of the atmosphere occurring over a specified area and time period to accomplish a particular goal (NRC, 2003). The area could be local (an airfield) or regional (a county on the Great Plains or the windward slopes of the Sierra Nevada mountains); the time period could range from a few days to a few months. The goals can be very diverse, including enhancement of water supplies, clearing of fog over an airfield, reduction in the number of lightning-initiated wildfires, or denial of use of trails or rivers (potentially as a military application). It is important to clearly distinguish such intentional, goal-oriented activities from “inadvertent weather modification”—the impacts on local or regional weather that are unintended consequences of human activities. Included in this last are urban heat islands, air pollution, and acid rain.

The most common form of weather modification is the seeding of convective or cumuliform clouds with an appropriate agent to produce or increase rainfall, reduce hail size, or suppress lightning. Wintertime stratiform clouds can also be seeded to attempt to increase snowfall and so enhance the depth of the snowpack on windward slopes of mountains. Clouds within hurricanes have been seeded on an experimental basis with the goals of diverting such storm systems away from coastal areas and/or reducing wind speeds (see Box 2.2). Various glaciogenic (for cold clouds) and hygroscopic (for warm clouds) seeding agents have been tried, including silver iodide, lead iodide, aluminum oxide, barium, soot, frozen carbon dioxide (dry ice), common salt, and water sprays. In the United States, silver iodide, which produces small particles that closely resemble ice crystals, is the commonly used agent for cold clouds.

As discussed previously in this report, climate intervention typically refers to proposed strategies and technologies for diminishing the risk and/or damages from such long-term changes in the global climate (Chapter 1). Even through some weather modification and climate intervention efforts appear similar—for example, the brightening of marine cumulus clouds (Chapter 3)—these two approaches to modify atmospheric processes target atmospheric phenomena operating on very different space and time-

Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
×

scales and, consequently, differ significantly in strategies and technologies.1 The goals of weather modification are to influence precipitation and/or lightning over relatively small areas for short timescales while those of climate intervention are to influence flows of radiant energy through the atmosphere that are global in extent; relevant timescales likely are centuries or even longer.

LESSONS FROM WEATHER MODIFICATION FOR CLIMATE INTERVENTION

Historical Attempts at Weather Modification

There is a long and checkered history of attempted control of weather. The first U.S. national meteorologist, James P. Espy, proposed to modify rainfall along the entire eastern seaboard by lighting gigantic fires along the Appalachian Mountains (Espy, 1841; Fleming, 2010b). The first attempt to actually modify a hurricane occurred in the late 1940s under Project Cirrus, a collaborative effort by the General Electric Company and the three military services (see Box 2.2). Although it was difficult to discern the impact of seeding on an October 1947 hurricane off the Florida-Georgia Atlantic coast, the seeded storm made an abrupt turn to the west and made landfall over the city of Savannah, Georgia. Subsequent investigations and threats of litigation were successfully defended, but further such experiments were delayed for more than a decade.

For over two decades, the federal program Project STORMFURY (1962-1983, with the last actual seeding in 1971) explored the possibility of weakening tropical cyclones by seeding the eyewall clouds (the most active region of the systems) with silver iodide (Willoughby et al., 1985). Although STORMFURY was ultimately judged a failure in terms of development of techniques for modifying hurricanes, its many observations greatly improved understanding of the functioning of these enormous storm systems and provided the basis for today’s federal hurricane research program (which seeks to advance our knowledge of tropical cyclones for the purpose of improving forecasting tools and techniques). The committee has been unable to locate evidence of any federal program attempting to modify hurricanes since the shutdown of Project STORMFURY and the subsequent refocusing of most tropical cyclone research on improving forecasting.

Today, the main technologies in use are seeding from aircraft, explosive artillery shells and rockets, and ground-based burner generators. In an effort to ensure the best pos-

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1 According to the Intergovernmental Panel on Climate Change (IPCC) definition of geoengineering, “Geoengineering is different from weather modification and ecological engineering, but the boundary can be fuzzy” (IPCC, 2012, p. 2).

Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
×

sible weather for the 2008 Summer Olympic Games, the People’s Republic of China put on one of the largest public displays of weather modification technology in recent years. The Chinese government deployed 30 airplanes, 4,000 rocket launchers, and 7,000 anti-aircraft guns to launch a seeding agent into any cloud that threatened an Olympic venue.2 During the hours preceding the opening ceremony, rockets were reportedly fired from 21 sites around Beijing to intercept a potentially disruptive rain belt before it reached the capital. Baoding City, southwest of Beijing, received about 100 mm (4 in.) of precipitation that night but in the capital the rain held off, even though August is normally Beijing’s rainy season.3

Current activities in the United States include numerous cloud-seeding projects4 at the state level (see Figure C.1). At present in the United States, all weather modification is carried out by private companies. The relevant trade and professional organization is the Weather Modification Association5 (WMA); the WMA publishes The Journal of Weather Modification.6 In addition, the American Meteorological Society has provided an information statement7 on weather modification, discussing some of the uncertainties involved and the need for careful risk management.

Cloud-Seeding Activities Continue with No Robust Research Program Supporting Them

Though it is the most common form of weather modification, seeding of convective clouds to produce or enhance rainfall appears to have little if any effect (NRC, 2003). Any project to properly measure the effects of cloud seeding is likely to be expensive because discerning the effects of cloud seeding from natural variability is difficult. However, seeding of convective clouds has been shown to reduce hail damage to crops (producing many small hail stones rather than a few large, damaging ones) and to suppress lightning discharges to reduce the number of wildfires. (In this last case,

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2http://www.latimes.com/news/nationworld/world/la-fg-rain31jan31,0,39372.story#axzz2uqfLW1MA;http://usatoday30.usatoday.com/weather/research/2008-02-29-china-weather_N.htm; http://www.theguardian.com/sport/2008/aug/08/olympics20081?guni=Article:in%20body%20link.

3 For some comments on effectiveness, see http://www.independent.co.uk/sport/olympics/how-beijing-used-rockets-to-keep-opening-ceremony-dry-890294.html and http://www.universetoday.com/16728/the-chinese-weather-manipulation-missile-olympics/.

4 See, for example, http://www.weathermodification.org/projectlocations.php.

5 See http://www.weathermodification.org/index.php.

6 See http://www.weathermodification.org/publications/index.php/JWM.

7 See, for example, the Society’s position statement, “Planned Weather Modification through Cloud Seeding,” available at https://www.ametsoc.org/policy/2010plannedweathermod_cloudseeding_amsstatement.html.

Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
×

image

FIGURE C.1 Self-reported recent and ongoing weather modification project locations on the Great Plains and in the western mountain regions of the United States. SOURCE: Weather Modification Association, https://maps.google.com/maps/ms?ie=UTF8&hl=en&msa=0&msid=210263860280044943005.00047f6342c83772ab091&ll=36.575469,-106.867725&spn=15.220428,16.763863&source=embed&dg=feature.

image

Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
×

thin strips of aluminum foil or “chaff” are used as the seeding agent; they short circuit the natural electrical charging process within the storm.) Seeding of wintertime stratiform clouds has been shown to significantly increase snowpack on mountain ridges (Huggins, 2006; Super and Heimbach, 1983).

Given the threat posed by tropical cyclones in general and hurricanes in particular to the Atlantic and Gulf coasts of the United States, numerous ideas have been advanced for modifying such large weather systems. As examples of these proposals, it has been suggested that soot be used to absorb sunlight and so change the air temperature in such a way that convection currents are reduced.8 Another suggestion is to spread environmentally friendly oil slicks to separate the warm ocean water (the energy source) from the atmosphere (where the energy is released), but maintaining an effective slick in the face of hurricane-force winds would be a challenge.

Despite previous calls for a national research program in hurricane modification or suppression, there is currently no government-funded research effort in this area (NRC, 2003). Both numerical and field explorations—funded by a diverse group of federal agencies including the National Oceanic and Atmospheric Administration (NOAA), the National Aeronautics and Space Administration (NASA), the Office of Naval Research (ONR), and the Department of Homeland Security (DHS)—continue to examine the basic physics underlying the functioning of hurricanes. The field programs include piggy-back experiments on operational NOAA and U.S. Air Force (USAF) “hurricane hunter” flights in the Atlantic and research flights in the eastern and western Pacific by U.S. university researchers using funding from NSF, ONR, and elsewhere.

Such efforts could provide a firm basis on how such systems might be modified. Present-day numerical models incorporating the best-available physical knowledge are capable of simulating many features of both tropical cyclones at different stages of intensity and the likely impact various modification strategies might have on such systems. The most recent comprehensive effort was the Hurricane Aerosol and Microphysics Program (HAMP; Cotton et al., 2011),9,10 which was supported by DHS, Science

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8 See http://www.itwire.com/science-news/climate/15149-boston-area-scientists-study-controlling-hurricanes-with-soot; this notion was investigated in the Hurricane Aerosol and Microphysics Program, described in following text.

9 See http://earth.huji.ac.il/data/file/danny/126_Cotton_JWM_2011.PDF. See also the briefing “The Rise and Fall of the Hurricane Aerosol and Microphysics Program (HAMP),” by J. Golden, W. Woodley, W. Cotton, D. Rosenfeld, A. Khain, and I. Ginis. See http://weathermodification.org/Park%20City%20Presentations/DC%20Program%20Review.pdf.

10 Hurricane Aerosol and Microphysics Program (HAMP): Improving Hurricane Forecasts by Evaluating the Effects of Aerosols on Hurricane Intensity – Final Report, by William L. Woodley. See http://saive.com/911/DOCS/DHS-Final-Report-Operation-HAMP.pdf.

Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
×

and Technology Directorate, Homeland Security Advanced Research Projects Agency/ Infrastructure and Geophysical Division. HAMP was discontinued in 2010 after only about 1 year of active research, though publication of results has continued. Similar but smaller-scale investigations by university researchers continue with support from the National Science Foundation11 and the Office of Naval Research.12 Both NOAA and NASA continue such research in their in-house research centers and support modest university studies.

The current position of NOAA on efforts to modify hurricanes was stated by Dr. Richard Spinard, then head of NOAA’s Office of Oceanic and Atmospheric Research:13

NOAA does not support research that entails efforts to modify hurricanes. NOAA, and its predecessor agency, once supported and conducted research into hurricane modification through Project STORMFURY from 1962 to 1983. Project STORMFURY was discontinued as the result of: 1) inconclusive scientific results, and 2) the inability to separate the difference between what happens when a hurricane is modified by human intervention versus a hurricane’s natural behavior. Since Project STORMFURY’s end 26 years ago, NOAA scientists have gained substantial insight on the complicated and interconnected processes within the overall hurricane environment. Yet, it remains unclear if enough knowledge has been gained to make any new modification attempts practicable.

Regulation and Oversight of Weather Modification Programs

There is a patchwork of regulations and oversight of weather modification programs at the international, federal, and state levels. Some climate intervention strategies face a similar scenario with respect to existing treaties and laws.

International

In 1975, the U.S. and Canadian governments entered into an “Agreement Relating to the Exchange of Information on Weather Modification Activities.” This provided only

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11 See, for example, https://www.nsf.gov/news/news_summ.jsp?cntn_id=104474; http://www.nsf.gov/news/news_summ.jsp?cntn_id=117388.

12http://www.defensenews.com/article/20130701/TSJ01/307010016/Navy-Scientists-Predict-KillerHurricanes.

13 Letter, R. Spinrad, NOAA, to W. Laska, DHS. Subject: Response to Statement of Work - Hurricane Aerosol and Microphysics Program. Dated July 29, 2009. See http://voices.washingtonpost.com/capitalweathergang/noaa_letter_dhs_hurricane_modification.pdf.

Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
×

for the exchange of information where weather modification activities being carried out by one nation might impact the weather in the other.14

Responding to a U.S.-U.S.S.R. initiative, weather modification in support of military operations—weather warfare15—was effectively banned by the United Nations in “UN General Assembly Resolution 31/72, TIAS 9614 - Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques.”16,17 This Convention was signed in Geneva on May 18, 1977, and came into force on October 5, 1978. The U.S. Senate gave its advice and consent to ratification on November 28, 1979, by a vote of 98-0. The Convention was then signed by U.S. President Jimmy Carter on December 13, 1979; the U.S. ratification was deposited at New York on January 17, 1980.18 Although there does not appear to be any active program on weather warfare within the U.S. military, discussions (perhaps better called speculations) continue as to the possibilities for weather warfare in the future.19

Federal

In the United States, routine weather modification (typically cloud seeding) is loosely regulated. At the federal level, several legislative efforts have been made since the 1940s in regard to weather modification. Initially, these were focused on promoting research and development (R&D) on weather modification techniques, reflecting the optimistic views of the time. In recent years, given the lack of significant progress in the 1960s and 1970s, federal efforts to advance weather modification R&D have

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14 See copy of this treaty at http://iea.uoregon.edu/pages/view_treaty.php?t=1975-RelatingExchangeInformationWeatherModificationActivities.EN.txt&par=view_treaty_html.

15 The U.S. military carried out a number of “weather warfare” activities in Vietnam. The most extensive was Operation Popeye, a massive cloud seeding effort over the Ho Chi Minh Trail that had the goal of reducing infiltration down this trail. This USAF effort was reported to have increased rainfall in the seeded areas by an estimated 30% during 1967 and 1968. For details, see Weather Modification: Hearings before the Subcommittee on Oceans and International Environment of the Committee on Foreign Relations, United States Senate, 1974, Folder 01, Box 06, Douglas Pike Collection: Unit 11 - Monographs, The Vietnam Center and Archive,Texas Tech University. http://www.vietnam.ttu.edu/virtualarchive/items.php?item=2390601002.

16 For the text of the Convention, see http://www.fas.org/nuke/control/enmod/text/environ2.htm.

17 It appears that the U.S. military’s position is that the language of the Convention applies only to modification activities that produce permanent changes in the environment, with local, nonpermanent changes still being allowed. See Enclosure D at http://www.dtic.mil/cjcs_directives/cdata/unlimit/3810_01.pdf.

18 For the history of the U.S. involvement in this Convention, see the U.S. Department of State document at http://web.archive.org/web/20070914081350/http://www.state.gov/t/ac/trt/4783.htm.

19 A good example of such speculations is provided by the research paper at http://csat.au.af.mil/2025/volume3/vol3ch15.pdf.

Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
×

generally not been supported by the Congress or the Administration. As will be seen, currently there is only a reporting requirement for weather modification activities.

In 1971, the U.S. Congress passed and the President signed Public Law 92-205. This resulted in the establishment of reporting requirement in Title 15, Chapter 9A—Weather Modification Activities or Attempts; Reporting Requirement. This act requires individuals conducting weather modification activities in the United States to report them to NOAA, which keeps records of such projects on behalf of the Secretary of Commerce. (This authorizing legislation laid out a research program in addition to this reporting requirement, but that program was never funded.)

In 2005 (U.S. Senate Bill 517 and U.S. House Bill 2995) and again in 2007(2007 U.S.

Senate Bill 1807 and U.S. House Bill 3445), bills were introduced in the Congress which would have established a program of expanded experimental weather modification in the United States, set up a Weather Modification Operations and Research Board, and implemented a national weather modification policy. Over the past 20 years, several other bills addressing weather modification have been proposed in the House and the Senate. None of these proposed bills made it into law.

State

It is at the state level, where weather modification is treated as a commercial endeavor, that one finds some oversight and regulation. Standler (2006) reviews many of the state laws in place and related court cases as of the date of his paper.20

As discussed by Standler (2006), many states have some form of statute for regulation and oversight of weather modification activities. Many, perhaps all, of the resulting regulations and procedures are now posted to the Internet. A good example of these state regulations is provided by the State of Texas Department of Licensing and Regulation—Weather Modification.21

Reviewing several of these both indicates some common themes and suggests that the lack of a common federal statute is a potential issue since weather modification activities could easily impact more than one state (recall the U.S.-Canada treaty mentioned above; see also the recent paper by DeFelice et al. (2014) on downstream effects of seeding). Standler (2006) has identified the two features common to most state regulations:

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20 Standler, Ronald B. 2006. Weather Modification Law in the USA. 33 pp. Available at www.rbs2.com/weather.pdf.

21 See http://www.tdlr.state.tx.us/weather/weathermod.htm#url.

Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
×

“1. ensure that commercial weather modification companies are competent (e.g., states often require cloud seeders to have earned at least a bachelor’s degree in meteorology or a related field, plus have experience in weather modification); and

2. require companies to have the resources to compensate those harmed by their weather modification (‘so-called proof of financial responsibility’).”

If these two conditions are satisfied, then the commercial entity may be licensed to do business in the state. As a second step, once a specific weather modification project is identified, then the licensed weather modification company must seek a permit to conduct specific operations at designated times and places. Some states require public notices of such efforts and the holding of public meetings prior to issuing of a permit. An environmental impact statement or documentation that the seeding technique to be used is environmentally safe may need to be provided by the weather modification company.

In some states, the local county government and/or sponsoring agricultural cooperative may be involved in the permitting process and may also assume some of the legal liability.

Lessons from Public Reactions to Weather Modification Activities

Contrail formations from routine airplane activities are ubiquitous. They are from the formation of ice crystals high in the troposphere through inadvertent seeding with jet engine exhaust particles. As such they are a consequence of air pollution. Contrails may have minor impacts on the climate in regions where jet planes are common, such as over Europe and the United States.

The history of weather modification—especially its military applications during the Vietnam War—has led some skeptical individuals to believe that contrails are visible signs of some nefarious plot. This skepticism has led to the notion of “chemtrails”—a widely publicized conspiracy theory (see Box C.1). Supporters of the chemtrail conspiracy believe that some, perhaps all, the contrails left by aircraft are really chemical or biological agents deliberately sprayed at high altitudes by a government agency for purposes undisclosed to the general public. They have speculated that the purpose of these releases may be for weather modification climate intervention through solar radiation management or Earth radiation management, psychological manipulation, human population control, or biological or chemical warfare. Furthermore, they hold contrails responsible for a wide range of respiratory illnesses and other health problems.

Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
×

BOX C.1 CHEMTRAIL CONSPIRACY THEORIES

When aircraft travel through the upper troposphere, the water vapor emitted in the engine exhaust can condense on other exhaust particles to form cirrus clouds. The results are the familiar contrails that can be seen in the upper troposphere trailing behind the generating aircraft. Chemtrail conspiracy believers speculate that contrails are formed by deliberate chemical releases for the purposes of albedo modification, psychological manipulation, population control, weather modification, or biological or chemical warfare, and are the cause of respiratory and other illnesses. Although this conspiracy has been repeatedly debunked,a which has shown that the sometimes persistent high-altitude contrails are simply normal water-based condensation trails from the exhausts of the engines of high-flying aircraft under certain atmospheric conditions in which the crystals and supercooled droplets are very slow to evaporate, this myth persists. Relevant to the topic of this report, Kuhn (1970), Lee et al. (2009), Frömming et al. (2011), and Schumann and Graf (2013) found that contrails have a similar effect as cirrus clouds and therefore, averaged over the globe, increasing the number of contrails would warm the planet.

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a See, for example, http://contrailscience.com/how-to-debunk-chemtrails/; http://sleet.aos.wisc.edu/~gpetty/wp/?p=989;http://conspiracies.skepticproject.com/articles/chemtrails/; http://irishweatheronline.wordpress.com/2013/09/08/contrails-vchemtrails-the-science-that-debunks-the-conspiracy/.

image

This chemtrails theory persists in spite of numerous efforts by members of the scientific community around the world to explain that what is being seen are just artificial clouds produced by normal condensation processes. People demanding explanations have sent thousands of complaint letters to various government agencies, showing the popularity of the chemtrail conspiracy theory and illustrating the possible type of reaction from a portion of the public when and if a climate intervention effort is undertaken.

Most of the state-level regulations related to weather modification foster openness and transparency (public notices, public meetings, and environmental impact statements). Any federal policy related to albedo modification would likely benefit from similar policies. In addition, the involvement of private contractors rather than the military services would likely help promote international buy-in and help minimize conspiracy theories.

Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
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Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
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Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
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Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
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Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
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Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
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Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
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Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
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Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
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Suggested Citation:"Appendix C: Planned Weather Modification." National Research Council. 2015. Climate Intervention: Reflecting Sunlight to Cool Earth. Washington, DC: The National Academies Press. doi: 10.17226/18988.
×
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The growing problem of changing environmental conditions caused by climate destabilization is well recognized as one of the defining issues of our time. The root problem is greenhouse gas emissions, and the fundamental solution is curbing those emissions. Climate geoengineering has often been considered to be a "last-ditch" response to climate change, to be used only if climate change damage should produce extreme hardship. Although the likelihood of eventually needing to resort to these efforts grows with every year of inaction on emissions control, there is a lack of information on these ways of potentially intervening in the climate system.

As one of a two-book report, this volume of Climate Intervention discusses albedo modification - changing the fraction of incoming solar radiation that reaches the surface. This approach would deliberately modify the energy budget of Earth to produce a cooling designed to compensate for some of the effects of warming associated with greenhouse gas increases. The prospect of large-scale albedo modification raises political and governance issues at national and global levels, as well as ethical concerns. Climate Intervention: Reflecting Sunlight to Cool Earth discusses some of the social, political, and legal issues surrounding these proposed techniques.

It is far easier to modify Earth's albedo than to determine whether it should be done or what the consequences might be of such an action. One serious concern is that such an action could be unilaterally undertaken by a small nation or smaller entity for its own benefit without international sanction and regardless of international consequences. Transparency in discussing this subject is critical. In the spirit of that transparency, Climate Intervention: Reflecting Sunlight to Cool Earth was based on peer-reviewed literature and the judgments of the authoring committee; no new research was done as part of this study and all data and information used are from entirely open sources. By helping to bring light to this topic area, this book will help leaders to be far more knowledgeable about the consequences of albedo modification approaches before they face a decision whether or not to use them.

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