early history (1946-51) of cloud seeding; need to support basic scientific research
Copyright 2002 by Ronald B. Standler Table of Contents Introduction Basic Technology Early History of Weather Modification at General Electric Problems with Experiments American Meteorology Society's Policy on Weather Modification Ethical Issues Support of Basic Scientific Research Bibliography About the author Introduction Weather modification is the effort of man to change naturally occurring weather, for the benefit of someone. The best-known kind of weather modification is cloud seeding, with the goal of producing rain or snow, suppressing hail (which can ruin crops), or weakening hurricanes. This essay is a companion to my earlier essay, Weather Modification Law in the USA, which concentrates on a discussion and analysis of court cases in the USA involving weather modification, and contains a detailed review of tort law in the USA that applies to weather modification. This essay is intended only to present general information about an interesting topic in law and is not advice for your specific problem. See my disclaimer. I cite articles and books in the (Author, year, page) format; complete bibliographic data is given below. Basic Technology It is a common misconception that pure water freezes at a temperature of zero celsius (32 degrees Fahrenheit). Zero celsius is actually the temperature at which ice melts. Water freezes at a temperature between 0 and -39 celsius, depending on the type of nuclei (i.e., contaminants) present. Liquid water with a temperature of less than 0 celsius is called "supercooled water". In November 1946, Dr. Bernard Vonnegut discovered that microscopic crystals of silver iodide (AgI) nucleate water vapor to form ice crystals. Vonnegut choose AgI crystals because there is nearly the same distance between molecules in the crystal lattice for both ice and AgI, which makes AgI the optimum material to nucleate ice. (Vonnegut, 1947) Vonnegut's discovery is a classic example of doing the right thing for the right reason at the very beginning of new technology, as a result of scientific knowledge. (Usually, progress is made by a series of small improvements on past practices, as a result of bumbling and guesswork. In contrast to the usual way, Vonnegut used his scientific knowledge to make a giant leap that has persisted as the state-of-the-art for more than fifty years.) Vonnegut not only discovered the ice-nucleating properties of AgI, but he also invented a practical way of generating tiny AgI particles to serve as nuclei for ice crystals. Vonnegut dissolved a mixture of AgI and another iodide in acetone, sprayed the solution through a nozzle to make droplets, then burned the droplets. (Vonnegut, 1949; Vonnegut & Maynard, 1952) In this way, one gram of AgI can produce 1016 nuclei for ice crystals. More than fifty years later, Vonnegut's method continues to be the common way to seed clouds. Release of AgI into an existing supercooled cloud (i.e., air temperature between -39 and -5 celsius) can convert water vapor to ice crystals, which is called sublimation. The ice crystals nucleated by the AgI will grow and local water droplets will shrink. The latent heat released by converting water vapor (or liquid water) to ice will increase vertical air motion inside the cloud and aid the convective growth of the cloud. Raindrops or snowflakes will grow larger by falling through a taller cloud. Also, moist air from evaporated moisture in the soil will be sucked into the base of the cloud by convection (i.e., updraft), thus increasing the total amount of water in the cloud. Perhaps 30 minutes after the AgI release, snow may fall below the cloud. Depending on the temperature and humidity below the cloud, the snow may change to rain, or even evaporate, before reaching the ground. AgI is the most common ice nucleus used in cloud seeding, but it is not the only material used. Substances with temperatures less than -40 celsius (e.g., solid CO2 ["dry ice"] pellets, liquid CO2, liquid propane, liquid nitrogen, etc.) can be dropped from airplanes into the tops of clouds, to induce formation of ice crystals. seeding warm clouds Clouds that do not contain appreciable amounts of supercooled water are known as "warm clouds". In warm clouds, most of the liquid water droplets will have temperatures greater than zero celsius. Seeding warm clouds with AgI or dry ice makes no sense, because the air temperature is too high. Langmuir (1948, p. 170 of Collected Works) proposed that using an airplane to dump liquid water into warm clouds might initiate a chain reaction that would produce rain below the cloud. Later, Langmuir (1951, p. 196 of Collected Works) proposed an alternative technique for seeding warm clouds: using an airplane to dump hygroscopic materials (e.g., NaCl) in the form of a dust particles, with each particle having an approximate diameter of 25 µm, into such clouds to convert water vapor to a droplet of liquid water. These new droplets fall and either collide or coalesce with other droplets, to form rain drops. Seeding clouds with either a water spray or hygroscopic materials requires dumping a large mass (e.g., 1000 kg) of seeding materials from an airplane, in contrast to the much smaller amounts of AgI needed to seed a different kind of cloud. Such use of hygroscopic materials are condensation nuclei, not ice nuclei. While the physics differs in cloud seeding with ice nuclei and with condensation nuclei, both seeding methods have the same legal issues. Earlier History It is commonly stated that cloud seeding was invented in 1946 by employees of the General Electric Research Laboratory. This "fact" is wrong. There were at least three earlier scientific attempts to modify weather: Prof. Emory Leon Chaffee at Harvard University dispensed charged sand from an airplane during 1924, to attempt to modify weather. (McDonald, 1961) W. Veraart in 1930 dropped dry ice into clouds, in an attempt to modify weather. His technique and results were apparently published only in his book, which was in the Dutch language. (Byers, 1974, pp. 5-6) Prof. Henry G. Houghton of MIT sprayed hygroscopic solutions into fogs in 1938 to dissipate the fog. None of these early scientists had adequate financial support for their research, so society was unable to benefit from their ideas. Looking back in time, it is clear that it is not enough to have a good idea or theoretical scientific insight into a problem. One must also have the financial resources to pay both salaries and expenses of scientists with ideas and insight. General Electric provided such resources to Langmuir and Vonnegut, and General Electric management was able to quickly arrange contracts with the U.S. Military. Early History of Weather Modificationat General Electric There was concern about legal liability from the earliest days of cloud seeding. At the time of his discovery, Dr. Vonnegut worked in the research laboratory of Dr. Irving Langmuir at General Electric Company in Schenectady, New York. Their initial work on cloud seeding was funded by the Company, not the U.S. Government. General Electric rented an airplane and released dry ice into clouds on four days during November and December 1946. The last day of seeding coincided with the "heaviest snowfall of the winter" in the Schenectady, New York area, which made the Company management concerned about the possibility of cloud seeding experiments causing harmful weather. (Havens, Jiusto, Vonnegut, 1978, pp. 7-8) A history of early cloud seeding produced by General Electric Company says: It was recognized that the possibility of liability for damage from cloud-seeding experiments was a very worrisome hazard in this new form of cloud experimentation. Since such a threat to the share owner's money would not be balanced by any known gain to the Company's products or business, there was a great reluctance to incur risks of uncertain but potentially great magnitude. This was another – and particularly important – reason that any seeding experiments be conducted under government sponsorship. No further seeding flights were made until such sponsorship was provided. (Havens, Jiusto, Vonnegut, 1978, p. 8) Just two months later, the U.S. Army Signal Corps began a contract with General Electric for cloud modification experiments. Part of this contract stated: ... the entire flight program shall be conducted by the government, using exclusively government personnel and equipment, and shall be under the exclusive direction and control of such government personnel. (Havens, Jiusto, Vonnegut, 1978, pp. 8-9) Management at General Electric Company immediately notified all those involved in the research "that it is essential that all of the General Electric employees who are working on this project refrain from asserting any control or direction over the flight program. The General Electric Research Laboratory responsibility is confined strictly to laboratory work and reports". (Havens, Jiusto, Vonnegut, 1978, p. 9) This rigid division of contractual responsibilities was designed to isolate General Electric from any tort responsibility for harmful weather that might be caused by cloud seeding. seed hurricane On 13 Oct 1947, the U.S. Military (as part of Project Cirrus involving General Electric) dropped 80 kg of dry ice into a hurricane in the Atlantic Ocean, safely off the eastern coast of the USA. (Havens, Jiusto, Vonnegut, 1978, pp. 41-42) The hurricane changed direction and traveled inland, where it did extensive damage to property in Georgia. The U.S. military classified the data from the seeding of this hurricane to frustrate litigation. (Ball 1949, pp. 225-226, p. 233) Attorneys for General Electric reviewed and censored Langmuir's scientific publications to avoid tort liability for damage by this hurricane. A biography of Langmuir says "For the first time in Langmuir's long career [38 years] at GE, officials occasionally wanted to know in advance what he was going to say in his public reports." (Rosenfeld, p. 205) Langmuir (1953, p. 212 of Collected Works) believed that there was approximately a 99% probability that this hurricane's change of direction was the result of the cloud seeding. Langmuir's opinion about the effect of the cloud seeding on this hurricane is not mentioned in any of his publications in scientific journals, but is mentioned in the 1953 final report on Project Cirrus, which was classified by the U.S. Military. It is likely that attorneys for General Electric directed Langmuir not to make any public admission that cloud seeding caused the hurricane to change direction, in order to avoid litigation against General Electric by victims of the hurricane. Subsequent analysis of the data by meteorologists showed that this hurricane had already begun to change its direction when the seeding was done. (Mook, Hoover, and Hoover, 1957) A modern assessment is: "... it seems very unlikely that the 1947 seeding could have had much affect on the hurricane except for the seeded clouds." (Gentry, 1974, p. 506) Langmuir's cloud seeding in New Mexico The General Electric / U.S. Military research project released AgI and dry ice in the vicinity of Albuquerque, NM during October 1948 and July 1949. Langmuir initially claimed that this release caused rain all over the state of New Mexico and possibly in Kansas. Langmuir's group continued to release AgI in New Mexico between November 1949 and July 1951. Langmuir claimed that the release of AgI modified the weather, not only in the state of New Mexico, but also more than 1000 kilometers downwind. (!) Langmuir's claim was rejected by the meteorological community, because Langmuir's evidence was inadequate. [citations] The release of AgI "was discontinued in July, 1951 during the great floods in Kansas and adjacent states." (Byers, 1974, p. 20) This flood was no ordinary flood: the 13 July 1951 flood at Kansas City was described as "the most devastating flood in the nation's history"; 17 people died as a direct result of that flood, despite weather forecasts and warnings. (Alexander, 1951) It is still unknown what effect, if any, the AgI release in New Mexico had on rain and floods in Kansas. The modern consensus of meteorologists seems to be that the release of AgI in New Mexico probably had no effect on the rainfall/floods in Kansas, but if there was an effect, the effect would be only a small enhancement of the total rainfall. As discussed below, perhaps the more interesting lesson is not one of science, but ethics: Langmuir sincerely believed that AgI release was modifying weather at long distances from the point of release, yet he continued to engage in such weather modification for two years, despite the possibility of harm from such modification, and despite the lack of consent by affected people. other historical details On 27 December 1950, the General Electric Company announced that it would no longer enforce its patents on weather modification methods. (Havens, Jiusto, Vonnegut, 1978, p. 53) By effectively putting its weather modification patents into the public domain, General Electric further isolated itself from tort liability for harm that might arise from weather modification technology that was developed by employees of General Electric. (Rosenfeld, p. 205) Dr. Vonnegut, appearing in 1952 before a U.S. Senate committee that was considering legislation on weather modification, said: Theory has predicted and experiments are confirming the fact that a few pounds of silver iodide released into the atmosphere in the form of fine particles can exercise a profound influence over the weather hundreds of miles away from the point of release. Clearly no private individual or group can be permitted to carry on operations over thousands or hundreds of thousands of square miles. The potentialities, both for good and bad, which attend silver-iodide seeding are so large that the development and use of this technique must be placed in the hands of the Federal Government. (Havens, Jiusto, Vonnegut, 1978, p. 53) Despite Dr. Vonnegut's clear insight into the nature of the problem, the U.S. Congress never passed a statute regulating weather modification. Problems with Experiments Before one can understand legal problems of cloud seeding, including tort liability for cloud seeding, one must first understand something about cloud seeding experiments. The following terse discussion is a summary of some of the problems associated with cloud seeding. Because I have not had the time to make a thorough review of the meteorological literature, but only looked at some review articles, I have not provided citations to the original sources. The traditional cloud seeding experiment randomly selected clouds to seed (or not to seed) and measured precipitation in the target area as the sole criterion of the effect of seeding. Such experiments reported in the meteorological literature superficially appear to give contradictory results: some experiments show a significant enhancement of precipitation, other experiments show no effect, and some experiments show a decrease in precipitation. Cotton (1986) has clearly explained why such a simple experiment is not adequate. Most importantly, we lack detailed scientific knowledge on the natural production of rain, hail, or snow. Without such knowledge, we can not predict the best time and place to seed clouds. Different physical processes may be important at different times in each cloud's life cycle, which may give a narrow window of opportunity for intervention via injection of AgI nuclei. Further, we can not accurately predict when and where the effect (if any) of seeding will occur. Some cloud seeding has used smoke containing AgI from generators on the ground to provide nuclei for clouds. The AgI is supposedly transported to approximately the -10 celsius region of a cumulus cloud by naturally occurring updrafts. However, there is concern whether the AgI actually reaches this region of the target cloud and, if it does reach that region, whether the AgI is uniformly dispersed over this region of the target cloud. While ground-based AgI generators are less expensive to operate than AgI generators aboard airplanes, airplanes are a much surer way to deliver the AgI to the appropriate region of the target cloud. AgI does not magically disappear a few hours after its release. There have been sporadic suggestions in meteorology journals and symposia that enhanced rainfall may [also] occur between 100 and 300 kilometers downwind from the point where the AgI was released. Aside from possibly modifying the weather at great distances from the intended target area, such effects could contaminate scientific experiments so that "natural" clouds in the control (i.e., nonseeded) group may contain some AgI. Such contamination would make it more difficult to prove that AgI is effective in modifying clouds. However, even with our limited knowledge of atmospheric physics, we know that different types of clouds behave differently. For example: isolated orographic clouds differ from large, multi-celled clouds associated with a front on a surface pressure map, and both differ from tropical cumulus clouds with a top warmer than -5 celsius. Therefore, one must be careful not to apply successes (or failures) with one type of cloud to another type of cloud. Current knowledge suggests that cloud seeding produces a small perturbation (e.g., perhaps 10% extra rainfall as the result of cloud seeding) of a phenomena that has much larger natural fluctuations [e.g., in the range from 250% to 400% (Grant, 1977, p. 13)]. While a 10% increase in rain can be economically significant, this small increase superimposed on much larger natural fluctuations poses a very difficult problem for statistical analysis of cloud seeding experiments. There are hundreds of articles in the scientific literature on the subject of cloud seeding, but few are available on the Internet. Dr. William R. Cotton, a professor of atmospheric science at Colorado State University in Fort Collins, has posted a comprehensive review of weather modification experiments during 1989-1997. There is also a good critical review of cloud seeding experiments in Australia, written in May 1995 by Brian F. Ryan and Brian S. Sadler. American Meteorology Society'sPolicy on Weather Modification In anonymous policy statements without any bibliographic citations, the American Meteorological Society declared: Operations that dissipate supercooled fog and low stratus (clouds containing water droplets at subfreezing temperatures) by seeding with ice-forming agents (e.g., dry ice, liquid nitrogen, compressed air, silver iodide, etc.) have become routine at some airports. .... There is statistical evidence that precipitation from supercooled orographic clouds (clouds that develop over mountains) has been seasonally increased by about 10%. The physical cause-and-effect relationships, however, have not been fully documented. .... Some experiments with warm-based convective clouds [bases about 10 celsius or warmer] involving heavy silver iodide seeding have suggested a positive effect on individual convective cells, but conclusive evidence that such seeding can increase rainfall from multicell storms has yet to be established. (AMS, 1998, p. 2771) There are indications that precipitation changes, either increases or decreases, can also occur at some distance beyond intended target areas. Improved quantification of these extended (extra-area) effects is needed to satisfy public concerns and assess hydrologic impacts. (AMS, 1992, p. 333). Similar words at (AMS, 1998, pp. 2771, 2775). The efficacy of projects intended to mitigate the severity of hailstorms remains indeterminate. Statistical assessments of certain operational projects indicate successful reduction of crop hail damage, but scientific establishment of cause and effect are incomplete. Results of various operational and experimental projects provide a range of outcomes. (AMS,… truncated (24,726 more characters in archive)
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