5

HOT TOWERS

Joanne Gerould, aged twenty-one, stood in front of a roomful of aviation cadets at the University of Chicago. The year was 1943 and the United States was at war. Though she was young, and more unusually still, a woman, she had good reason to be standing where she did. She knew more than the cadets did about the movement of air and moisture through the atmosphere. That one thing was reason enough to grant her the authority to lecture them. The men needed to learn, as quickly as possible, the fundamentals of weather forecasting.

What the young woman needed was less clear, but she already had a strong sense of what she didn’t want. She didn’t want to be dependent on a man. She’d learned from her mother the emotional damage it could do to be bright and unable to follow one’s dreams. Her own mother had trained to be a journalist but never managed to pick up the threads of that ambition after she’d given birth to Gerould. She’d taken out her frustrations on her daughter, and Gerould, in turn, had struggled with the weight of that bitterness. She’d searched for escape, finding it in the teeming confusion of the marshy estuaries in which she’d played as a child on Cape Cod, in the coastal waters upon which she’d sailed and in which she’d swum, and finally, in the skies through which she’d flown. Aged just sixteen, Gerould had obtained a pilot’s permit. It was both a metaphorical and a very real form of escape, out and up, into the skies.

When it came time to choose a college, Gerould had followed the same urge, flying away from her home in Cambridge, Massachusetts, and from Radcliffe, where both her mother and grandmother had studied. She went west, to the University of Chicago. There, a course that included plenty of science classes appealed to her. She thought she might study astronomy. But the time was right not for the study of the heavens, but of earthly skies. World War II was, famously, an airman’s war. Flat navigational charts, plotted with straight rulers, were set aside in favor of spherical globes on which bits of string were laid to trace the curving paths taken by planes that found their target with unerring directness. Old European battle lines looked set to disappear in the face of the new Pacific arena and the northern pathways that touched the whitest parts of the planet. The geography of the world looked as if it could be remade by these airmen, and the countries for which they flew, if only they could win the war.

At the start of the war, the Germans had more than 2,700 trained meteorologists available to advise their pilots on how to stay safe in the air. The United States had just thirty.1 To rectify this alarming imbalance, the air force had gone straight to the person who could make the fastest and greatest difference. Carl-Gustaf Rossby was a maelstrom of meteorological theory and administration, a thinker and a doer, with energy to spare. A Swede, he’d received his own meteorological education in Bergen, Norway, at the time and place in which meteorology had come of age professionally and started to deliver on promises long in the making.

In Bergen, a man named Vilhelm Bjerknes had managed to cleave the practical necessity for daily forecasts to the clarifying mathematical equations of physics. The theories of the weather that Bjerknes had helped develop, and which Rossby had learned better than anyone else, were well suited to explaining the skies above Scandinavia. Having come of age during World War I, these men naturally saw the battlegrounds of northern Europe projected on the cold skies overhead. “We have before us,” wrote Bjerknes, “a struggle between a warm and a cold air current. The warm is victorious to the east of the centre . . . The cold air, which is pressed hard, escapes to the west, in order suddenly to make a sharp turn towards the south, and attacks the warm air in the flank; it penetrates under it as a cold West wind.”2 These organized lines of clouds could be deduced from observations at regularly spaced intervals, then tracked as they moved across Britain, the Netherlands, and into the skies above Denmark, Sweden, and Norway.

Rossby was the man the U.S. Air Force trusted to bring the necessary meteorological know-how to the pilots in time for it to matter. To do that meant getting training programs (one would not be enough) up and running as soon as possible.3 And to do that, as was so often the case during wartime, meant calling upon women to do jobs that they would not ordinarily be offered. So when Gerould went to see Rossby about the possibility of doing some meteorology courses alongside her astronomy degree, she ended up with an offer instead: to teach on the cadet training course that Rossby had established to quickly boost the military’s forecasting capability. While she had not gone seeking such an opportunity, she was more than ready for it when it arose. And while she had not yet, in fact, fallen in love with the study of the clouds, stepping into Rossby’s office was a fateful step on her journey toward an intellectual passion that would last a lifetime.

FIG. 5.1. Carl-Gustaf Rossby with the rotating tank used to study the motion of fluids in the atmosphere and ocean. Credit: NOAA/Department of Commerce.

FIG. 5.2. Graduation and commissioning of U.S. Army Air Force meteorology cadets at the University of Chicago, September 6, 1943. Credit: University of Chicago Library, Special Collections Research Center.

Clouds, Gerould would later write, were more complicated than almost anything else. The only thing more complicated, she conceded, were human beings. “The mysteries of cloud formation, and the precipitation that can follow, have proven to be one of the most challenging aspects of the global climate system. Except for man himself, the weather is probably the most variable, unreliable, and fluctatory phenomenon of which human intelligence has dared to attempt a science.”4 A cloud suffers the buffets of the atmosphere around it, retaining its shape for a while before becoming utterly changed. To become entrained, in meteorological terms, is to be taken up by a pre-existing air current or cloud. It is what happens to air in the environment that comes close to a cloud. “Within ten minutes, I was entrained in his orbit,” was how Gerould described her first meeting with Rossby.5 It is no accident that Gerould used this term, since she herself had used the concept it described (though she did not invent it) to create a completely new way of thinking about clouds and, as a consequence, a new way of thinking about the circulation of the entire atmosphere.

Part of what Bjerknes and Rossby had begun, which Gerould would continue, was the project of moving the study of clouds beyond the scientific equivalent of stamp-collecting. By the 1930s, when Rossby arrived in America, the study of meteorology had different ambitions. Those were twofold: first, and most urgently, to provide operational support to the military in order to help pilots make informed decisions about where and when to fly. Second, Rossby and those who worked with him wanted to transform meteorology into a physical science. By this, they meant a science at the heart of which lay physical equations that described the movements of the atmosphere. There were obvious linkages between these two desires, but they were also, perhaps to a surprising extent, distinct. It was possible to make meteorological forecasts in the absence of physical theory. And physical theories were not always that useful when it came to making practical forecasts. It wasn’t clear, then, in which direction progress would first be achieved, and by whom.

Gerould taught for a year on the course, from the fall of 1943 to the summer of 1944. That was enough. After that, she’d been entrained by the study of meteorology. She then enrolled in a one-year master’s program and continued to take classes after it ended. So it was that she found herself still studying in 1947, listening to a series of lectures on a topic that had been more or less ignored by the Scandinavians who’d put together the modern science of frontal weather systems: tropical meteorology. What Gerould heard electrified her and caused her to abandon once and for all her ambivalence about a field that she had good reason to doubt could ever provide her with an all-important steady income and intellectually rewarding work. The sense of an exciting new area of study opening up before her eyes was almost palpable and too compelling to resist. “Almost immediately,” she later remembered, “a bolt of lightning struck me and I said to myself and my colleague, ‘This is it—tropical cumuli are what I want to work on.’”6

The lecturer to whom Gerould owed this electric realization was Herbert Riehl, a man just eight years her senior. A Jew, he had been forced to flee Germany as a young boy, traveling first to England and then to America, where he himself became entrained by meteorology, almost by chance. He’d come to the United States with the idea of becoming a screenwriter and had pursued that passion for a few years. But success was not forthcoming and, seeking more practical employment, he applied to enter a U.S. Army Air Corps training program. The electrical engineering course he applied to was full, so he settled for meteorology. After completing the one-year program at NYU, he too went to see Rossby, and Rossby offered him the same opportunity he’d offered Gerould. Riehl accepted, and he taught on the training course at the University of Chicago the year before Joanne Gerould, from 1941 to 1942.

By 1942, the war in the Pacific had taken a dangerous turn. The Japanese had taken Burma, Malaysia, the Dutch East Indies, the Philippines, and Thailand. To combat the Japanese threat, military pilots desperately needed a much better understanding of the meteorology of the tropics. Thousands of military sorties over the tropical Pacific made it glaringly obvious that the weather worked very differently there than it did in Northern Europe. Sudden squalls arose in the absence of obvious fronts and demanded explanation. Rain fell from skies far too warm to sport ice crystals. The situation wasn’t simply confusing; it was potentially dangerous. To fly safely, pilots needed better predictions of bad weather. The U.S. Army Air Corps agreed when Rossby proposed adding a special tropical institute to the nine-month cadet program. Arrangements were made as quickly as possible, and in the summer of 1943 the Institute for Tropical Meteorology in Puerto Rico was created in hopes that new observations and concerted effort might come up with something useable in time to help the war effort.

Riehl spent just two years in Puerto Rico, first as an instructor and then as director of the fledgling institute, before being sent back to Chicago at the war’s end. His time there was transformative. The meteorology that had been so proudly and confidently pioneered in Bergen was almost completely useless in the tropics. Tor Bergeron’s theory of rain formation, the pre-eminent such theory of the Bergen school, required the presence of ice crystals. Without ice, Bergeron had theorized, rain could not fall.7 That may have been true in Norway, but a single evening in Puerto Rico was enough to demonstrate how patently false that theory was in the tropics. Riehl vividly remembered such an evening, his first in Puerto Rico, when “some of the staff walked along the beach, and admired the beauty of the trade-cumuli in the moonlight. Well-schooled in the ice-crystal theory of formation of rain, they had no suspicions about clouds with tops near 8,000 feet where the temperature is higher than +10 C. Suddenly, however, the landscape ahead of them began to dim; then it disappeared; a roar approached as from rain hitting roof tops. When some minutes later they stood drenched on a porch, drenched and shivering, they had realized that cloud tops with temperatures below freezing were not needed for the production of heavy rain from trade-wind cumulus. There and then the question arose: How is it with the other theories in so far as they concern the tropics?”8

Back in Chicago, with his tropical experiences still fresh in his mind, Riehl raised this question with the students sitting in front of him. He described how at the end of the war, the navy had allowed a small group of researchers based at Woods Hole Oceanographic Institution (WHOI) to use some of their planes and ships to undertake some research on the trade winds of the North Atlantic. The project was charmingly informal, an example of the kind of do-it-yourself ethos that characterized WHOI at the time. Together, Jeffries Wyman, a physical chemist, and Al Woodcock, a self-taught jack-of-all-trades, made some of the first measurements of temperature and velocities both inside and outside the so-called trade-wind cumulus clouds (the clouds found in the region just north and south of the equator where the winds blow consistently from east to west, and toward the equator).9 Their data put to rest forever the idea that the tropical atmosphere was organized into fronts. Instead, Woodcock and Wyman had demonstrated that the equatorial atmosphere displayed what one scientist later described as a “disconcerting sameness,” with endless fields of trade-wind cumuli—isolated puffy clouds, like those in a children’s storybook—stretching to the horizon.10 This in itself was a strikingly different meteorological visage from that displayed by northern skies, where storms were common and clouds organized in long frontal systems. And there was more. Hidden within this seemingly calm atmosphere was the capacity for sudden, violent storms. Unlike in upper latitudes, when squalls arose in the tropics, they did so without any apparent provocation. Rarely, but unforgettably, they gave rise to a monster storm known in the Pacific as a typhoon and in the Atlantic as a hurricane. What caused these storms to arise when and where they did remained highly uncertain.

The data gathered by Woodcock and Wyman raised more questions than it provided answers. What caused the puffy trade-wind cumulus to form? Did the sea surface play a role in their formation? When and why did storms develop out of this seemingly uniform sea- and airscape? Like the atom, tropical clouds seemed to contain the hidden potential for dramatic transformation. The challenge was to explain what caused a seemingly harmless patch of tropical atmosphere to change into a violent squall and from there into an even more violent hurricane.

Listening to this news from a distant part of the planet, and the seemingly endless questions it raised about the basic workings of the atmosphere, Gerould had felt a rising sense of excitement, akin to an epiphany, that this was the work to which she wanted to devote herself. It remained far from clear whether that would be possible. In 1944, she had married a fellow University of Chicago student, Victor Starr, who had recently become the second person to be awarded a PhD in the University of Chicago meteorology program. Joanne Gerould had become Joanne Starr. She’d given birth to their son, David, in June, at the end of her master’s degree. When she told Rossby of her plans to study tropical cumulus clouds, his response was cutting: “That’s fine. An excellent problem for a little girl to work on because it is not very important and few people are interested in it, so you should be able to stand out if you work hard.”11 Undaunted, Starr immediately wrote to a friend of the family at Woods Hole, asking for a summer job. She got the job and spent the summer working on the Wyman and Woodcock cumulus data Riehl had lectured about.12

For Starr, it was an exceptionally busy time. Soon after David’s birth, she started teaching physics to students at the Illinois Institute of Technology, spending summers at WHOI continuing her research on the cumulus cloud data. She convinced a somewhat reluctant Riehl, who claimed to know little more than she did about these clouds, to supervise her doctoral work. Given this level of activity, it is little wonder that something had to give. That something was her marriage. Joanne and Victor Starr were divorced in 1947, leaving Joanne with a young son to look after and the challenge of maintaining a research career that had barely begun. By now, she was deeply committed to a career in meteorology. Her chances of succeeding were not improved by her status as a divorced mother of a young child. In 1948, she married yet again within the circle of University of Chicago meteorology department, this time to Willem Malkus, a physicist studying for his PhD under Enrico Fermi. Now Joanne Starr Malkus, she received her PhD in 1949, and with it became the first woman in the nation to be awarded the advanced degree in meteorology. Another son, Steven, followed in 1950. All the while, she continued teaching at the Illinois Institute of Technology and traveling to Woods Hole in the summers to continue her research on cumulus clouds. Only in 1951 was she offered a paid research position—her first ever such job—at Woods Hole, which had already become a favorite location for both work and home life. At twenty-eight years old, she was returning to the skies she had left as a teenager just nine years earlier, with paid work as a research meteorologist.13

As a mother of two young children, Malkus might have chosen to continue doing the theoretical work on cloud models that she’d already begun. But she would never be satisfied simply analyzing other people’s data, and in any case, there was too little of it to answer the questions she wanted to answer. Years later, she remembered the moment that she realized she would need to do her own airborne studies, during a conversation with Henry Stommel, then a young oceanographer at Woods Hole:

One day we were sitting there sort of talking at the blackboard and beating our heads around. You know we can’t go any farther in this until we get some new observations. Why don’t we see if the Navy still has any of those PBY aircraft and maybe we can not only put back the instruments we had in the Wyman expedition, but also make measurements of a few more things, particularly to get vertical velocities and liquid water . . . We sat around . . . saying “Do we really want to do this, are we willing to commit all the time to undertaking all the instrumentation of the aircraft, and installing the instruments and using screwdrivers, flight tests, calibration tests, and so on.” We finally decided that we had to, there really wasn’t any choice about it; that we were not going to get any farther understanding the physics of clouds with making models of clouds without making further observations and taking what we had learned from previous observations and models. . . . We went into it quite consciously, realizing it was going to eat up a big part of our lives. It was with a certain degree of ambivalence.14

FIG. 5.3. Joanne Malkus analyzing data from the Pacific Cloud Hunt at Woods Hole Oceanographic Institution, with a long roll of cloud prints draped across the table. Credit: Schlesinger Library, Radcliffe Institute, Harvard University.

FIG. 5.4. Joanne Malkus in a DC-3 on a field trip to the Caribbean from Woods Hole Oceanographic Institution in 1956. Credit: Schlesinger Library, Radcliffe Institute, Harvard University.

FIG. 5.5. Joanne Malkus loading instrumentation aboard the Woods Hole Instrumental DC-3 for cloud flights over and near Bermuda, c. 1955, with colleague Andrew Bunker. Credit: Schlesinger Library, Radcliffe Institute, Harvard University.

* * *

She may have been ambivalent, but she did not remain still. She managed to gain access, as she had hoped, to an old navy airplane, and off she went, flying out from Woods Hole into the open skies and open waters south of Cape Cod. The closest tropical waters were near Bermuda, and that is where she headed. She was not alone. The airplane itself was kitted out with as many instruments as could be made to work on it and, in addition to the pilot, there was a photographer on board to help capture the clouds.

The ride was noisy and bumpy, but it was noisier than it was bumpy, and so Malkus and the photographer communicated by written note. She began, “The first run we got should be pretty valuable (fingers crossed) despite other subsequent difficulty. The nose camera contribution will be a vital part—because I do think we did get in to the most active part of the bubble and the film will show that—so things could be one whale of a lot worse!!” The response followed, written just below: “But how about the lens being ‘less dry’ (courtesy J. S. M.) that it sees nothing but droplets? Ah! The misery of this life (joking, we are in the beautiful tropical atmosphere).” And Joanne came back again: “Silly creature—it didn’t get wet until we first went in the cloud did it???” And received the following response: “Yeah! Yeah, but the PBY didn’t bounce either until we got inside, or at least not much until then.”15

The notes are full of acronyms and banter. J. S. M. is of course Joanne Starr Malkus. The beautiful tropical atmosphere refers to the skies around Bermuda. The PBY is an amphibious plane developed by the navy for use during the war. Attached to it were a number of devices, including a nose camera for recording the size and location of the clouds, as well as a set of instruments for measuring temperature, humidity, and density of the clouds and the surrounding atmosphere as the aircraft stitched its way into and out of the cloud, observing it at a range of altitudes. The plan was to study these clouds in order to better understand how an apparently calm atmosphere could give way periodically to violent storms.16 Flying in and out of the same cloud five or six times, Malkus and her crew performed the seemingly impossible task of fixing a cloud, rendering permanent the evanescent collection of water droplets. Without the airplane and, more specifically, the instrumented airplane, she would never have been able to achieve her objective. Key were the decisive movements of the airplane itself, which traveled not quickly, as might have been expected to capture the evanescent cloud forms, but slowly, to lessen the impact of aircraft speed on the measurements.

The notes describing the challenge of keeping the lens dry and the airplane stable survive because they recorded another similarly evanescent phenomenon—the burgeoning relationship between Malkus and the photographer, a man she referred to only as “C.,” even fifty years later. Malkus kept these notes for the rest of her life because they captured a fleeting moment that mattered deeply to her, the burgeoning moments of a relationship that was to become one of the most important of her life.

FIG. 5.6. Joanne Malkus with the crew of her first research aircraft, which was on loan from the navy to Woods Hole Oceanographic Institution. Credit: Schlesinger Library, Radcliffe Institute, Harvard University.

The first time she’d seen C., she’d felt an instant attraction. It was “truly love at first sight in my case,” she recalled in 1996. “This emotion is still strong 52 years later, 15 years after his death.”17 But this was not a conventional love story. In 1951, when these notes were made, Malkus was married to Willem Malkus. She had met C. when they found themselves working in the same institution, and soon, on the same project. Malkus had learned to see the atmosphere as a place whose tranquility belied a potential for rapid and dramatic change. And so it was with other people. With C., she learned how in an instant a relationship could shift from one of distance to breathtaking intimacy.

She probed her feelings in a diary she kept at the time with the same attention to detail and the same desire to follow an investigation to its logical conclusion that she demonstrated in her cloud studies. She wrote in pencil in a simple black-and-white ruled notebook and addressed her thoughts directly to C. “Why am I planning to write numerous letters to you, when it is highly unlikely that you will ever read them?”18 Her answer to the question was that the diary entries could constitute half of an imaginary conversation with C. “By recording fragments of these,” she writes, “I, at least, may learn something.” In the same way, by observing a cloud from every angle, she hoped to learn “what makes the cumulus clouds grow, how they grow, what stops them from growing and the role they play in trapping moisture, heat and momentum.”19 For Malkus, learning about people and clouds was similar, requiring many observations taken at many angles. And just as clouds could only be understood in relation to their environments, people could really only be understood in relation to others.

One of the key scientific outcomes of the project was to prove that it was possible, using a slow-flying airplane, to gather useable data about the clouds. A more substantive conclusion, based on that data, was that it seemed to be the case that larger cumulus clouds were formed by the interaction and aggregation of smaller clouds.20 It wasn’t simply that small clouds grew into bigger clouds, in other words, but that big clouds were formed out of the groupings of smaller clouds. That meant that in order to understand clouds, it would be necessary to consider their interactions at multiple scales.

* * *

Malkus now began thinking about how and whether individual clouds and cloud behavior could be connected to larger-scale weather. What, she wanted to know, was the function played by small-scale convection—the movement of hot air—on larger-scale processes such as the movement of air from the tropics into higher latitudes?21 In 1954, she used money from a grant she received to travel to the UK, where she presented her findings and sat in on lectures on cloud physics and precipitation at Imperial College with the aim of establishing “exchange of ideas and persons” in order to bring about “the vitally needed merging of the fields of cloud dynamics and cloud physics.”

Malkus was not alone in wondering about the relationship between scales ranging from the molecular to the planetary or in finding inspiration in Woodcock and Wyman’s data.22 The first glimpses of the complexity of the tropical atmosphere had also fired the imagination of Henry Stommel, then twenty-seven years old and looking for good problems to work on. He wrote his first scientific paper on entrainment, presenting the then-controversial and counterintuitive idea that it was impossible to separate the study of clouds from the study of their surroundings.23 In the mid-1950s, the entire field of meteorology was grappling with the question of scale, some of which had been raised by Stommel’s paper on entrainment.24 Much as oceanographers had once focused on the Gulf Stream as a phenomenon separate from the basin in which it occurred, meteorologists had long focused on clouds as discrete objects that could be analyzed separately from their surroundings. It was becoming apparent that it would never be possible to understand parts of the atmosphere in isolation. Only by looking at the overall circulation could individual parts be truly understood. Or, as Victor Starr had put it, “attempts to formulate ad hoc explanations for individual details of the general circulation without due cognizance of their role as functioning parts of a global scheme” would be doomed to failure. Something more was needed: an appreciation of the total meteorological picture. Meteorologists wanted to know how what happened within clouds affected what happened in the massive storms known as cyclones or anti-cyclones, and how such storms themselves related to the so-called general circulation of the atmosphere. What connections and feedbacks existed, and where did the discontinuities lie? This was a daunting proposition, but in 1951, Starr approvingly noted a new focus on the “essential oneness of the atmosphere which must be studied as an internally integrated and coordinated unit.”25

FIG. 5.7. U.S. Army Air Force meteorologists prepare to launch a hydrogen-filled balloon with a radiosonde that measured temperature, humidity, and pressure. Credit: NOAA Photo Library.

The biggest reason for this change in the kinds of questions meteorologists were asking was the amount of new data becoming available. The airplane was essential, but another airborne device—the radiosonde—proved just as important. It consisted of a hanging basket of meteorological devices connected to a weather balloon that could transmit data on temperature, humidity, and pressure via radio to a receiver on the ground.26 With radiosondes and airplanes, meteorologists could soar up to 30,000 feet into the atmosphere. It was now possible to imagine a global meteorology in which the motions of the entire atmosphere of the entire planet—along both vertical and horizontal dimensions—might be observed. No longer would meteorology be bound simply to a thin slice of atmosphere at ground level or to a specific region, as the Bergen school and the Institute of Tropical Meteorology had been. To transform global data into a global science, however, more than just observations were needed. Both novel theories and new ways of manipulating data were also needed to create what Rossby called, in the title of a landmark 1941 article, the “scientific basis of modern meteorology.”27

* * *

In addition to the airplane and the radiosonde, there was one other great new meteorological instrument of the postwar era which would come to be essential for Malkus, as it would be for nearly every other working meteorologist. By 1946, its moment had arrived. In that year, the New York Times revealed plans for a “new electronic calculator, reported to have astounding potentialities.”28 The machine, measuring some eighteen by twenty feet long, would be capable of performing the “the most incredibly complicated and advanced equations in inconceivably minute fractions of a second.” Though the super-calculator had been initially conceived as a tool for calculating the trajectories of ballistic missiles, almost immediately its meteorological potential came to the fore. John von Neumann, a professor at Princeton and the leading theorizer—and promoter—of electronic computing, argued that it could have “a revolutionary effect” on weather forecasting. These new machines were especially suited to repeating the same set of operations on an ever-changing set of data, precisely the kinds of calculations that were needed to solve the “nonlinear, interactive and difficult” problems that faced those trying to predict the weather.29

For those who had read Richardson’s 1922 paper imagining the processing power of 64,000 human computers, it seemed as if the future had finally arrived. But while Richardson had dreamed only of forecasting the weather, the prospect of controlling weather and even climate was both an exciting and a potentially troubling new twist. The very first news report on the planned supercomputer noted that not only would it soon be possible to forecast the weather more accurately than ever before: It might even make it possible to “do something about the weather.”30 From the start, the purpose of the weather-calculating supercomputer would be to indicate not only likely future weather, “but also the points at which fairly small amounts of energy could be applied to control the weather.”31 The super-calculator, in other words, was always, at least theoretically, a weather-control machine.

Though von Neumann passionately believed in the redemptive possibilities of computing, he understood that fear was as important as hope in generating support for the project. Weather and climate control was a classic dual-use technology. In the right hands, it could lead to the alleviation of drought and famine, safer aviation, and even the improvement of climate for leisure and enjoyment. But it could also be used to wreak havoc on previously unimaginable scales. “Present awful possibilities of nuclear warfare may give way to others even more awful,” he warned. “After global climate control becomes possible, perhaps all our present involvements will seem simple.”32 This moment of control, simultaneously feared and anticipated, seemed imminent. Not only was computer power sure to identify the necessary triggers, but the scale of the technological intervention that would be needed to affect climate at the global scale was no greater, von Neumann estimated, than that which had built the railway and other major industries.33

Just as a small nudge could send a boulder caroming down a mountain, relatively small inputs of energy could work on the atmosphere to produce massive effects. “The pull of a trigger is enough to release the energy in an enormous mass of air,” explained a reporter in the New York Times. “Pull the trigger at the right place and we could ride the whirlwind and divert it to regions where it can do no harm.”34,35 A hurricane could potentially be diverted by igniting oil in key locations. Rain could be summoned by sprinkling coal dust on land to absorb heat. The details remained to be worked out, but already in 1947 it seemed clear that “the weather makers of the future are the inventors of calculating machines.”36

* * *

For all the visceral horror and Promethean ambition such climate fantasies provoked, the computer was not only a tool for world-making or -unmaking. It was also a cerebral device that had the potential to extend the realms of thought—rather than action—in previously unimaginable directions. Once brute calculations could be organized along scientific principles, the computer became a tool for thinking about the atmosphere.37 As such, it had the potential to transform meteorology into an experimental science. Not only could the computer enable the sorts of direct modification of weather or climate that could serve as experiments, but something more novel would become possible—a new kind of meteorological thought experiment, also known (with quotes in the original) as a “weather model.” In this way, the computer enabled experiments to be done on a controlled atmosphere, safely removed from the realm of geopolitics where any atmospheric experiments raised special concern in the wake of Hiroshima and Nagasaki. “Nothing in plaster or wood,” as an early commentator clarified, “but something that lies more in the mind and on the plotting board.” This mental space enabled “an assumed earth” to be shaped according to the questions “we wish to ask of it, with an increasingly complex imaginary earth slowly built up of the constituent parts we add to it, a simple ocean, a series of rudimentary mountain ranges, a certain amount of water vapor.” Thanks to the understanding such models facilitated, “we can begin to think of making weather to order on a regional scale.”38 If the model reproduced observed phenomena, it was a good indication the science was on the right track, “just as the birth of a child who resembles a paternal grandfather legitimizes both itself and its father.”39

Such “imaginary” uses were implicit in the early plans for the application of electronic computing to numerical weather prediction. Weather forecasts—which is what the computers were initially conceived of being able to do—are, after all, imagined futures. The difference between numerical weather forecasts and so-called “weather models” is that models were intended to be used as tools for understanding the weather processes, while forecasts were usually addressing much more immediate and practical questions.

In Woods Hole, Malkus was applying these new ideas and new computing power to the tricky task of describing the growth of individual clouds. Using data she had gathered in the bumpy PBY flights, she created the first numerical cloud model that described, using a series of physical equations, how clouds grew and developed.40 This was groundbreaking work—the first such “model” to attempt to reduce cloud growth to a series of equations. But it was only a start. Her studies of individual clouds only deepened her curiosity about how the process of convection acted on the larger scale. Both the temporal and spatial scale of regional or even global atmospheric motions required much more computing power than was available. And even if the computing power did become available, the problem remained much too complex to solve fully using the brute force of numerical computation. Better physical understanding was needed before more complex models could be contemplated.

Malkus took another tack. First, she convinced Herbert Riehl, her former supervisor, to join her as a partner on the project. Together, they started to look at data not just about tropical clouds. Instead, they looked at a vastly increased scale, the entire tropical zone, which stretched ten degrees on either side of the equator all the way around the planet. This was a scale of investigation that had previously been impossible. Now, thanks to the data streaming in from airplanes and radiosondes and plotted on global maps, Malkus and Riehl were able to form a clearer picture of how the atmosphere was moving around the entire planet—and to identify a gaping hole in theories of the general circulation. They identified this hole by tracking the movement of the sun’s energy around the planet and in the process stumbling on an unexplained gap in that transfer—like a missing participant in a game of telephone. Somehow energy was moving around the planet, but the details remained fuzzy about where and how.

The sun is the source of all the energy on our planet. When its rays hit the earth, the angle and shape of the planet determine how much light is received by different parts of the planet. At latitudes higher than thirty-eight degrees in both hemispheres, the earth loses heat. Only between thirty-eight degrees and the equator—roughly the latitudes occupied by the African continent—is the radiation balance positive. But the planet generally maintains its average temperature at a fairly stable level. So the planet as a whole must act to transfer heat from the region around the equator to the poles; otherwise it would begin to cool off. To complicate matters, sea-level winds at the equator—the so-called trade winds upon which sailors had long depended—blow very consistently toward the equator. While it was generally accepted that the heat was carried aloft over the equatorial regions, and then transported poleward at higher altitudes, it was unclear what the precise mechanism for this transfer was. Somehow heat must be getting from the surface of the equatorial ocean—where the heat so efficiently absorbed by the water was in turn radiated upward—to the higher levels of the atmosphere known as the troposphere where the winds blew toward the poles. But measurements had shown that the middle layers of the atmosphere—between the surface of the ocean and the troposphere—did not have nearly enough energy to transfer the heat upward. The middle layers were a kind of dead zone, energetically speaking. This left a mystery. How was the hot air getting from the sea surface up to the troposphere?

In addition to the “weather models” in which an increasingly complex earth was constructed out of equations representing physical phenomena, a new breed of studies had been developing since 1920 or so.41 It was to these studies that Simpson and Riehl now turned. Called bookkeeping studies, they worked on the principle that in order to understand the planet, it was sometimes advisable to (momentarily) set physics aside. Just as an accountant processes transactions in order to balance a business’s account books, so too was it possible to “process” the heat in the earth’s climate in order to reach a certain balance, or equilibrium. In these studies, all that mattered was the increase or decrease of a chosen variable, be it heat, angular momentum, carbon dioxide, or any number of other quantities (such as, for example, ice, ozone, tritium, methane, and sulfur).

As suggestive as these papers were about the role played by small-scale phenomena such as eddies in larger-scale atmospheric features, no one had yet considered that cumulus clouds could play a role in large-scale circulations. This was the task Malkus and Riehl now set themselves. Their guess, based on their study of the radiosonde data and a rather bold intuitive leap made in the absence of other evidence, was that the heat was traveling upward from the ocean’s surface in narrow regions of exceptionally buoyant air. These columns, or “hot towers,” in which water vapor was condensed into droplets and released its heat, were the “overgrown brothers” of ordinary trade-wind cumulus clouds. They were giant—commonly reaching up to 35,000 feet high and sometimes as high as 50,000 feet—but relatively sparse. At any given moment, there might be only a few thousand active across the entire planet. These could serve as escalators for an enormous amount of heat, which was thereby able to bypass the lower layers of the atmosphere in which the winds were blowing back toward the equator. The lopsidedness of the situation struck Malkus and Riehl forcefully. “The most striking conclusion from this work,” they summarized, was the fact that “only about 1500–5000 active giant clouds are needed to maintain the heat budget of the equatorial trough and thus, implicitly, to provide for much of its poleward energy transport!”42

The hypothesis—and it remained only a hypothesis, with little direct evidence to support it—solved the mystery of how heat from the surface of the tropical oceans could be transported high enough in the atmosphere to be carried on winds blowing away from the equator. It also linked the energetics of the ocean and the atmosphere in a way that very few meteorologists (or oceanographers) had yet done. Hot towers showed that the atmospheric circulation could only be understood in relation to the ocean that supplied most of its heat. Clouds could play an outsized role in the climate system, just as the impresarios of climate control had imagined. Even without proof and a rather wide degree of uncertainty, the hypothesis was suggestive enough that Malkus and Riehl did not hesitate to publish.43 Cumulonimbus clouds of the necessary height—some 40,000 to 50,000 feet—had been observed. The question remained whether there were enough of them transporting enough heat to resolve the paradox. They ended their paper calling for more observations, during the upcoming International Geophysical Year, to enable their theory to be refined and tested.

The challenge for Malkus and Riehl, and for others, was to generate not separate meteorologies—of fronts, of hot towers, of the tropics, and of cyclones—but a single science that could, somehow, describe the linkages between these scales. The theory of hot towers had seemed to solve the mystery of how energy was transferred from lower to higher altitudes in the tropics, but it had created another. How would it be possible to characterize (or understand) a “system” in which large-scale regularities—the general circulation—were in part determined by the most seemingly ephemeral and fickle of phenomena?

“What we were doing that no one else had ever done before was to put in the cloud systems as a key part of tropical energetics,” explained Malkus, “and thus have energy move up scale in the circulation size hierarchy, rather than down as in classical hydrodynamics.”44 She was keenly aware of how strange, and theoretically complex, such a system was. “It is no small wonder,” wrote Malkus, “that the global circulation system operates in fits and starts, with its evanescent cylinders, of transient numbers, whose very existence depends upon the vagaries of the flow itself!”45 Malkus and Riehl had put their finger on a weather trigger, just the sort of thing the promoters of weather control were after. But what good was an evanescent, difficult-to-locate trigger that seemed, somewhat paradoxically, to depend for its existence on the large-scale phenomena that it might be said to affect? Here was a confoundingly circular and dynamic world of multiple scales that seemed to lack any reassuring hierarchy. The prospect of control seemed remote.

FIG. 5.8. Joanne and Herbert Riehl puzzling over hurricanes, in a cartoon by Margaret LeMone. Note the “real hand-analyzed data” and the big question: “Why are there so few hurricanes?” Credit: Margaret LeMone.

Malkus and Riehl’s first impulse, after publishing this suggestive paper, was to do some more observing. Given the complex relationship between wildly disparate scales, they thought the only way to make further advances would be to “study these widely different scales of motion in their context to each other.” They set out to make the “first attempt, largely descriptive, to relate synoptic and cloud scale phenomena.” With this research program, Malkus was moving a step toward her goal of linking small-scale phenomena, such as clouds, with larger-scale phenomena such as storms, hurricanes, and finally the general circulation of the entire atmosphere. It was an exciting time. The long era during which the cry had always been “we need more observations” seemed to be finally coming to a close, as airplanes and radiosondes began gathering more data in more places than ever before.46 Drawing on the Wyman and Woodcock trade-wind expedition, Stommel’s 1947 entrainment paper, and a series of other papers demonstrating how important the surrounding atmosphere was in the formation of clouds, Malkus and Riehl summarized their findings in a book titled Cloud Structure and Distributions over the Tropical Pacific Ocean. In it, they demonstrated why it was no longer be possible to look at the tropics and see a boring, steady-state atmosphere. Henceforth, the tropics would be seen as a tumultuous place, far more variable than it was stable.47 Rain fell in the tropics far more erratically than anyone had imagined. In regions where the majority of rain fell on just two or three days a month and even annual averages varied significantly, averages were not merely unhelpful but actively misleading.48

* * *

Underlying this optimism, for those who cared to notice, was a groundswell of doubt and uncertainty. It was one thing to have observations and the means to make calculations based upon them, but would “mere” observations ever really be enough to crack the atmospheric code? Physical insights, not just observations, were required to reduce an otherwise potential deluge of data into a usable current. “It is only through the leaven of some purely physical hypothesis,” cautioned Victor Starr, “that we are guided to the appropriate mathematical use of these principles.”49 Where to find that leaven? The most useful tool in the scientific arsenal for reducing complexity was the experiment, a controlled intervention that enabled a researcher to isolate and test aspects of an otherwise overwhelmingly complex problem. Computers had raised the possibility of identifying likely points for experimental intervention. But the ability to perform controlled physical (rather than computer) experiments in which certain variables were held stable while others were manipulated had long eluded atmospheric scientists, partly for the reasons that Victor Starr had underlined. The atmosphere was so big, so unruly, and so “essentially one” that it was almost impossible to render it a pliable experimental subject.

Clouds could be—and had been—reproduced in the laboratory, including memorably by John Tyndall himself, but these miniature artificial clouds failed to capture all of the salient features of natural clouds. The motions of fluids more generally had been fruitfully investigated by Dave Fultz in a laboratory at the University of Chicago beginning in 1950. There he’d set up what were affectionately called rotating dishpan experiments. By heating a round tank of water, rotating it, and then dropping dyes into it, Fultz captured pictures of changes in the flow that reproduced some of the large-scale features of the general circulation of the atmosphere and ocean, such as the jet stream and other atmospheric waves. Using this apparatus, Fultz and others were able to reproduce some atmospheric phenomena artificially.50

The laboratory work by Fultz and others was useful but also frustrating, precisely because of how important scale was to matters both oceanographic and atmospheric. Much could be learned from reducing the ocean or atmosphere to a dishpan-sized model, but much was inevitably missed from such a set-up. The only way to truly understand the atmosphere, many felt, would be to experiment on it directly. The idea of an atmospheric experiment was almost unavoidable in these years, following a war that had been brought to a close by a grand and terrible atmospheric experiment that had produced, in the skies over Hiroshima and Nagasaki, an entirely new cloud.

As darkly potent as the radioactive clouds released by atomic weapons were, other, less obviously powerful technologies made surprising and important contributions to the growing sense that experimenting on the planet was not only inevitable but a necessary part of the progress of human knowledge. It was specifically the domestic freezer, a new appliance designed by General Electric to meet the growing demand of America’s housewives for convenient and nutritious food with which to feed the postwar baby boom, which heralded a transformation in meteorological practice.

In 1946, in the laboratories of GE, a young engineer named Vincent Schaefer had been playing around with creating supercooled clouds inside one of these consumer freezers. After generating clouds made up of the supercooled water vapor expelled from his lungs, he experimented with dropping bits of dry ice into them. Immediately, and dramatically, the clouds precipitated into snow. His colleague Irving Langmuir predicted that atmospheric clouds found outside GE freezers would respond in the same way. Bernard Vonnegut (brother of author Kurt) then demonstrated that silver iodide could be a very effective cloud seeder (more effective, per gram, than dry ice). In 1946, Schaefer succeeded for the first time in seeding a cloud in situ with dry ice. It was the beginning of a bonanza of cloud seeding, in which states across America (mainly in the dry Western states) sought to solve their agricultural worries with the expeditious application of a few kilograms of silver iodide.

In 1947, under the auspices of Project Cirrus, Langmuir seeded the first hurricane using this technique. The effects were disastrous. The storm, which had been headed northeast over the Atlantic off the coasts of Florida and Georgia, abruptly reversed track and headed west, making landfall in Georgia and South Carolina. Though the observers on-board the aircraft which had seeded the storm did not measure any changes in the structure or intensity of the storm (which might have indicated that the seeding had been the cause of the change in its direction), Langmuir nevertheless could not resist claiming “success” in this instance, even though the landfall had resulted in damage.51 The local towns sued, and cloud seeding was flagged not as a source of knowledge but one of potentially limitless liability.

Such episodes demonstrated how strong was the desire to exploit what remained a little-understood aspect of cloud physics—the role played by seeds, or nucleators, in prompting precipitation. Bernard Vonnegut’s brother, Kurt, was inspired by these events to write Cat’s Cradle. Ice-9, Kurt Vonnegut’s imaginary corollary to silver iodide, turned everything it touched not to water, but to ice. The consequences were terrible, and the message of the tale was as clear as the destructive ice: Interfere with the dynamics of nature at your peril.

The distance between visionary dreams and inadvertent consequences was shorter than most imagined. In 1957, Roger Revelle and Hans Suess published an article in which they described the widespread emission of carbon dioxide via the burning of fossil fuels as a “large scale geophysical experiment.”52 This now-famous sentence is often presented as a prescient call to arms, one of the first to alert humanity to the risks of an uncontrolled intervention into the planet’s climate system. Revelle and Suess did emphasize the novelty of the situation, noting that this experiment “could not have happened in the past nor be reproduced in the future.” But rather than warning of the danger of unchecked emissions, Revelle and Suess were urging their fellow scientists to take advantage of an unprecedented opportunity to study the ocean, much as Rossby had mused on the possibility of covering the polar caps with coal. They used the term experiment in the classical sense of a scientific test designed to eliminate as much uncertainty as possible. “This experiment, if adequately documented, may yield a far-reaching insight into the processes determining weather and climate.” Careful measurement and observation, in other words, could transform a merely unwitting (and uncontrolled) intervention into a proper scientific experiment. Revelle and Suess accordingly urged, as Malkus and Riehl had, that data be collected during the International Geophysical Year which could be used to track the path taken by this excess carbon dioxide as it traveled through the “atmosphere, the oceans, the biosphere and the lithosphere.”53

* * *

Ever on the lookout for opportunities to do more observations, Malkus quickly realized that hurricane studies could be a continuation of her cloud studies by other means. A new opportunity presented itself in the wake of a series of natural disasters. In 1954 and 1955, a series of harsh hurricanes pummeled the East Coast of the United States. In quick succession, hurricanes Carol, Edna, Hazel, Connie, and Ione battered the coast, destroying more than six billion dollars’ worth of property (in 1983 dollars) and killing nearly 400 people. In response, Congress appropriated funds for a National Hurricane Research Project (NHRP), to be headed by Robert Simpson, a meteorologist who had been a forecaster during the war and had helped set up a wartime weather school in Panama. Intervention was written into the plans for this government laboratory just as it had been for the first supercomputers.54 The mission was explicitly tasked with studying how to modify hurricanes artificially, along with more basic research into the formation, the structure and dynamics, and the means of improvement of forecasts of hurricanes. The new funds meant airplanes and airplanes meant government scientists could now, for the first time, do in situ cloud studies on tropical clouds that stretched from the surface of the ocean all the way up to the troposphere.

Malkus saw that the NHRP could be a platform for a more genuinely experimental research program into the link between cloud and atmospheric dynamics she had been hoping to pursue. In 1956, she flew to Miami, where she met Bob Simpson for the first time. Here, finally, was a chance to help turn meteorology into an unambiguously experimental field science, with the rigor and attention to documentation and control that had been missing from most previous cloud-seeding projects.

While the NHRP was established in an attempt to distinguish hurricane research from the seat-of-the-pants, under-theorized, and overhyped work done by Schaefer, it was impossible to start with a clean slate. The memory of the hurricane that had slammed into Georgia possibly as a result of intervention was fresh, and when it came time to draw the boundaries within the Atlantic where hurricanes would be fair game for intervention, an excess of caution was applied. The result was that only one or two hurricanes a season passed through the area in which seeding was allowed.

Still, the chance to use the new instrumented aircraft funded by the NHRP was too good for Malkus to pass up, and while she had focused on clouds up until that point, she didn’t see the sense in making distinctions between what were obviously related phenomena. “So I thought, well gee, I’d better get into this too. Hurricanes are, after all, systems of tropical clouds. Systems of tropical clouds that somehow get together and run wild. Why did they happen in that way?”55 She started reading up on hurricanes, and soon she had come up with an idea that linked the hot-tower hypothesis she and Riehl had developed with the formation of hurricanes.

She was fascinated in particular by the “calm central eye, surrounded by furious winds.” What, she wondered, explained this phenomenon? Relatively little was known about hurricanes, because radiosonde and aircraft sounding were scant. She pored over the data there was, including a film made by MIT which pioneered the use of weather radar to probe the eyewall of the 1954 hurricane Edna. Looking carefully at the film, she realized that most of the air in the hurricane eye came from the cloudy eyewall.56 With Riehl, she developed a model of how a hurricane develops which emphasized the importance of the ocean as an “extra” heat source.57

* * *

At the same time that Malkus was using hot towers to think about hurricane formation, Robert Simpson had begun developing his own theory about how to modify hurricanes. He thought that if you could seed certain key clouds (equivalent to hot towers) in the eyewall, then you could force it to re-form farther out in the storm, thereby reducing the intensity of the wind and weakening the storm. On September 16, 1961, Robert Simpson was able to test his theory when a naval aircraft dropped eight canisters of silver iodide into the eyewall of Hurricane Esther. Instead of continuing to grow as it had been, the storm maintained a constant intensity. Thanks to the coordinated observations of crew aboard six airplanes monitoring the storm, the response of the storm to the seeding was recorded in great detail. These synchronous radar observations showed that kinetic energy had been somewhat reduced in the eyewall. The next day, another load of canisters was dropped, but they missed the eyewall. Subsequent observations indicated that the storm had retained the same intensity it had after seeding the day before. From the difference in the storm’s evolution in response to seeding and no seeding on successive days, they deduced that the seeding had been successful. In an article for Scientific American, the two researchers wrote with no small measure of pride that instead of “merely observing” the formation of a hurricane, they had attempted to “interfere in a critical area with the delicately balanced forces that sustain a mature hurricane.” They took some pains to point out the novelty of the work, noting that their experiments were among the few “ever performed on an atmospheric phenomenon larger than a single cumulus cloud.” Despite the potential risks, there were good reasons to experiment with hurricanes, not all of which involved modification. Better forecasting seemed an almost guaranteed outcome once hurricane research had graduated from an “observational discipline to an experimental one.”

But forecasting was only the start. Hurricanes were the perfect place to test assumptions about weather and climate triggers. Precisely because they are so massive, any attempt to modify one will fail unless it is precisely targeted. Failure to modify, then, would prove a theory’s limitations, while successful modification would mean the theory was likely correct. For this reason, attempts at hurricane modification seemed like ideal tests of hurricane theory, with the bonus that if the theory proved good enough and a hurricane could be precisely targeted, truly staggering amounts of energy would be within human control. In practice, it was extremely difficult to know if in fact an intervention had been successful. If you don’t know what it would have done otherwise, how can you know if you have changed a hurricane’s behavior?

There was a paradox here. Successful intervention required precisely the advanced understanding of hurricanes that such an intervention was designed to help generate. Despite this limitation, those in charge of government funding deemed the seeding of Hurricane Esther a success. Soon after, a new project was established which was explicitly, and solely, aimed at modifying hurricanes: Project Stormfury, founded in 1962 as a joint undertaking of the U.S. Navy and Department of Commerce. Malkus’s numerical cloud models were critical to the justification of the project, providing a tool for testing assumptions and generating predictions against which modification attempts could be checked.

Malkus herself had mixed feelings about weather modification. Though she was attracted by the research possibilities and the more distant potential for humanitarian applications, she was also wary of the corners that were often cut when it came to cloud seeding. Asked in 1961 to comment on the potential for hurricanes to be diverted, she said, “I wouldn’t say we’re on the threshold, but weather control is not a totally ludicrous idea.”58 The problem was that interventions were often staged “with too many claims, with an underestimation of the enormous natural variability of the system, and with impatience on the part of the management to get a positive result in a short period of time.”59

Despite her doubts, two things convinced her to come on board as an advisor. The project was relatively inexpensive and had potentially huge benefits to humanity. And, just as importantly, Stormfury offered a way to improve her models and learn more about hurricanes. “I believed the Stormfury Project would be the only way I could do the experiments on cumulus clouds which I had been thinking about for some time.”60 Rather than trying to seed hurricanes in order to modify their courses, Simpson saw seeding as a tool for doing experiments in the atmosphere. “People should be placing their emphasis on weather modification as atmospheric experiments and I’ve said so all along.” While it was feasible to change the development of individual clouds with seeding, the modification of hurricanes with the intention of benefiting humankind was, she thought, always a “very long shot.”

With this in mind, Malkus signed on to Project Stormfury. The plan was to bend the practical goals of project to her own scientific aims—to make of modification both a scientific tool and a practical intervention. She would never otherwise be able to muster the number of aircraft necessary to monitor an experiment well enough to determine if it had been successful.61 In 1963, she got exactly what she wanted, when she carried out a seeding experiment that “changed my life and that of many others.”62 Stationed in Puerto Rico in mid-August of that year, Malkus and the rest of the Stormfury team were waiting for Hurricane Beulah to develop an eye well-formed enough to be modifiable. In the lull before the storm, Malkus saw a chance to test her ideas about cloud growth.63

During the experiment, a total of six aircraft and several dozen technicians enabled Malkus to make successful measurements on eleven non-hurricane clouds, of which six were seeded and five were controls. “When that first cloud exploded,” she remembered, “I was never more excited in my life.”64 The scientists and crew of the several aircraft also broke into wild celebrations on seeing the growth. All save one of the seeded clouds grew explosively, while the control clouds did not. The results were just as Malkus’s model had predicted. She had managed to do what she had long hoped for—to use seeding as a tool for atmospheric experimentation, and to get the full force of the navy’s aircraft backing her as she did so.

Malkus and Simpson published the results of their cloud-seeding efforts in Science, and the magazine put a dramatic series of pictures of the exploding clouds on its cover in the summer of 1964. The response from the public was instant and intense. It was, in Malkus’s words, “an immense storm” for which neither of them was prepared. The “intensely interesting effects” that had been produced in the seeded clouds stoked hopes and fears that the time for weather control had finally arrived. Some greeted the arrival of a hoped-for utopia of weather control, while others saw a repeat of the hubristic meddling with nature that had led to the bomb.

FIG. 5.9. Cover of Science for August 7, 1964, illustrating the results of Joanne Malkus and Robert Simpson’s cloud-seeding experiment.

As exciting as it had been to watch the seeded clouds surge upward, Malkus and Simpson were careful to make it clear that the most significant outcome of the experiment was not the explosive growth but the demonstration that the experiment itself was possible. They wrote an article for Scientific American explaining the nature of the cloud-seeding experiments and trying to pin down the meaning of control. On the one hand, the seeding had shown that “now a real atmospheric phenomenon is at last subject to a relatively controlled and theoretically modelled experiment.” It was true, they thought, that clouds could finally be turned into experimental subjects. But the kind of control needed for scientific experiment was preliminary to—and less complete than—that needed to be able to manipulate hurricanes to human ends. That kind of control—what Malkus and Simpson called “real control”—would be longer in coming. Rather than a giant leap forward, they cautioned that “here meteorology is taking the first small steps toward becoming an experimental science, which it must become if man is ever to exert real control on this atmosphere.”65

The navy and the Department of Commerce were not interested in theoretical models but in modifying real hurricanes. The same weather system that had enabled Malkus and Simpson to test their model using cloud seeding also proved amenable to more practically oriented interventions. Just a few days after the successful cloud seeding, Hurricane Beulah had obligingly developed a more mature eyewall. The entire hurricane—not just a nearby cloud—was now ready for seeding. Using many more aircraft and significantly more silver iodide to massively seed the eyewall, the navy pulled out the stops to see if modification was possible. On the first day that seeding was attempted, the special silver iodide bombs missed the eyewall and no effects were seen. The next day conditions for seeding had improved, and this time the bombs hit their target. Measurements of the core of the storm showed that the pressure dropped precipitously following the second seeding and the cloud pattern of the storm changed dramatically, with the eyewall dissipating and forming ten miles farther away from the center of the storm, much as Malkus and Simpson had predicted.

Despite the seeming success, it was impossible to say on the basis of one modification attempt whether the seeding had definitely caused the changes to the hurricane. The natural fluctuations of hurricanes were so big, and the nature of cloud patterns so little understood, that much remained unknown. Repeating the experiment was one way to test the hypothesis, but given how much these storms varied naturally, it could take centuries to “separate statistically the man-made changes from the large natural fluctuations.”66

In 1964, the National Academy of Science (NAS) convened a panel on weather modification to provide advice on how best to proceed in an area that was both scientifically and ethically challenging. Malkus was a member of the panel, along with Jule Charney, Ed Teller, Ed Lorenz, Joe Smagorinsky, and others. The panel cautioned against haste and noted that evidence to support the efficacy of seeding remained thin. There was as yet no data to suggest, for example, that so-called winter orographic storms, such as those in Colorado which were the subject of great interest on the part of farmers and ranchers in the state, could be made to produce significantly more rain, nor that hurricanes could be steered, nor that black dust or other surface coverings could produce rain. The evidence did not exist to support a leap into weather modification on an operational basis. Most present efforts were characterized by a “seed first, analyze later” approach from which very little reliable information could be gleaned. Patience, counseled the panel, was needed. It could take decades, not years, before the physics was well-enough understood to support widespread weather control. A split developed between research scientists and state legislators of arid states, some of whom accused the scientists of being more interested in producing papers than water.67 Much remained unresolved, even as experts like Malkus gave good reasons to proceed cautiously. In the same year that the NAS panel advised restraint, Congress passed a special resolution appropriating $1 million for operational weather modification programs.

The first small steps toward “real control” of the weather which Malkus and Simpson described in 1964 are today reminiscent of those taken most famously by Neil Armstrong five years later as he stepped onto the moon. But it was to another momentous speech that the scientists may have been referring. That speech, given by President John F. Kennedy on July 26, 1963, occurred just weeks before the cloud-seeding experiments were carried out. In the televised address, Kennedy, speaking in a measured voice in a tone of somber hope, announced the partial ban on nuclear tests in the atmosphere, ocean, and outer space that he and Soviet statesman Nikita Khrushchev had been able to engineer after years of difficult negotiations. Kennedy called the agreement a “shaft of light” in a time otherwise characterized by suspicion and tension, and “an important first step—a step toward peace—a step toward reason—a step away from war.” He reiterated the metaphor in the closing lines of his speech, ending with what felt like an audacious hope: “and if that journey is a thousand miles, or even more, let history record that we, in this land, at this time, took the first step.”68

For Malkus, life changed dramatically in 1965. She had left Woods Hole in 1961 to take a position at the University of California, Los Angeles. That same year, she gave birth to Karen, her daughter with Willem. In the meantime, her relationship with Bob Simpson, which had developed over the course of the shared work at the NHRP and on Project Stormfury, turned into something deeper. The cloud-seeding experiments and the modification of Beulah gave rise to what Malkus called the “Malkus/Simpson collaboration and increasing close friendship.”69 In 1964, Malkus divorced Willem Malkus and left her tenured position at UCLA for a research position at the U.S. Weather Bureau. That career move, an unlikely one at first glance, was necessary because nepotism laws prevented a husband and wife from working at the same institution. On January 6, 1965, Joanne and Bob Simpson were married. With the wedding, Joanne took the name of Joanne Simpson and the directorship of Project Stormfury, at the Weather Bureau. Thus began what she called her second great love, and a partnership of mind and spirit that would last until her death.

If Joanne Simpson had finally found contentment in her personal life, the controversy over weather modification raged on. In 1963, she had celebrated in the skies above Puerto Rico as she watched the seeded clouds explode upward, and shared in the sense that hurricane modification was possible when Beulah seemed to respond to seeding. The Stormfury hypothesis that seeding the supercooled water around the eyewall of a hurricane could cause it to release latent heat and migrate outward, weakening the storm, seemed to be correct. These early days of optimism and excitement turned out to be misplaced. Circumstances would conspire to make it impossible to carry out the research necessary to determine whether the hypothesis was, indeed, correct. As difficult as it was to coordinate six or even ten aircraft flying through a hurricane, it turned out to be much more difficult to create a statistically powerful enough program of experiments to tame the natural variability of these great storms. Hurricanes are extremely variable objects. In order to understand their motions—both natural and modified—it is necessary to study a lot of them. This is always an expensive undertaking, and sometimes an impossible one. From 1963 until 1968, no eligible storms passed through the experimental area. Meanwhile, the controversy over weather modification continued. By 1967, Joanne Simpson, no longer willing to put up with the tension surrounding the program, resigned. Stormfury continued, with uneven but ultimately unconvincing results. When, in 1969, Hurricane Debbie finally obliged the researchers and five seeding runs were made, the results were deemed consistent with a revised Stormfury hypothesis (which required less instability in the eyewall and deployed massive, repeated seeding just outside the eyewall instead). But eligible hurricanes that passed through the safe zone remained frustratingly rare, making it impossible to further verify the eyewall hypothesis. Over the course of the 1970s, research into hurricane modification tailed off, and when eventually the project was canceled in 1983, it was deemed a failure.

* * *

There were to be no easy answers to the question of whether modification could be done, much less whether it should be done. Nevertheless, weather modification was, already, a reality. Both intentional and inadvertent modification of the atmosphere was already happening, in places both near and far. In order to have any hope of distinguishing the artificial state of the atmosphere from its natural state, basic atmospheric processes would need to be understood. Simpson and her fellow panel members noted (in 1964) that the major barrier to figuring out which clouds could be seeded was the “great natural variability” of clouds themselves, which included differences in drop sizes, water content, ice content, temperature structure, internal circulation, and electrification.70 This natural variability made careful statistical evaluation both necessary and “very difficult.”

What was very difficult on the small scale was both vexing and potentially catastrophic on the larger scale. Though it was not yet possible to “induce perturbations to trigger massive atmospheric reactions,” such a day might be foreseeable. What was not yet within reach was the capacity to predict the effects of such a major modification with “continent scale or larger” extent. Until that was possible, the committee concluded that “to embark on any vast experiment in the atmosphere would amount to gross irresponsibility” (italics in original).71

In order to understand the effects of artificial modifications to weather and climate, the committee suggested that a theory of natural climatic change was needed. Instead of performing experiments in the atmosphere, where their effects would be hard to interpret and which could have unintended consequences, the committee suggested the safe space of the computer model within which “the consequences of artificial perturbations could be assessed.”72 The boundary between the earth and the air, and the sea and the air, was a crucial and understudied aspect of what they still called the large-scale atmospheric circulation (rather than the coupled ocean atmosphere). Field experiments here seemed feasible and much needed, along with numerical studies.

The panel included a section on inadvertent atmospheric modification, a problem with no sign of abating. “We are just now beginning to realize that the atmosphere is not a dump of unlimited capacity, but we do not yet know what the atmosphere’s capacity is or how it might be measured.”73 The committee also noted that the pollution caused by cities was capable of affecting the local climate. As Rossby and Revelle had, they remarked on the scientific potential of such a “continuing experiment in climate modification.”

When Simpson left the Weather Bureau, she returned to academia, taking a job as professor of atmospheric science at the University of Miami and taking on the directorship of an experimental meteorology laboratory at Coral Gables. There she continued the work she had started on Stormfury, convinced that if she applied her dynamic seeding technique to small-scale cloud structures, she would be able to generate a testable hypothesis about the potential for generating rainfall from seeded clouds. But this project, too, was to be stymied. If individual clouds could be seeded with her technique, she wondered if seeding could cause more so-called cloud mergers, groups of clouds that were naturally productive of the most rainfall in Florida. Simpson calculated that she would need to do several hundred seeding experiments to detect a fifteen percent increase in rain in the target area. Her boss was unwilling to fund even a hundred cases. Thus the pattern set in Stormfury of research projects handicapped by a lack of data continued. Simpson felt that one of the fundamental assumptions of Stormfury—that supercooled water was present in abundance in hurricanes—had been somewhat slanderously called into question. According to her, data gathered by the NHRP that demonstrated the presence of such water was later thrown away, and new results suggesting no such water was present were used to justify the cancellation of the project.74

Simpson’s personal involvement in weather modification—both at Stormfury and on the Florida experiments—was a source of regret for her. Weather modification for her had always been a means to an end. That end was not the transformation of clouds or storms, but the gathering of data. She deeply regretted the cancellation of the weather modification programs even as she had distanced herself from them. In a speech she gave as American Meteorological Society President on October 4, 1989, she remarked on the bitter irony that many meteorologists had celebrated the demise of weather modification programs—which they viewed as unscientific—since it was the cloud physics community which suffered from the demise of weather modification research the most, as “badly needed new observational data on clouds is much slower and harder to come by than in the heyday of weather modification experiments.”75

Simpson’s own thirst for new data sent her toward the last great project of her long career. She moved to a new Laboratory for Atmospheres at NASA’s Goddard Space Flight Center, and in 1986 became the lead for the science team in charge of a Tropical Rainfall Measuring Mission. This satellite was the first of its kind, carrying a space-based rain radar that could peer deep into the heart of the clouds through which Joanne had so painstakingly flown. She worked on this project for eleven years before it finally launched. The satellite exceeded the goals the NASA scientists had set for it five years after its launch. In 2002, it measured the profile of latent heat released by tropical systems, providing a space-based confirmation of the work she and Riehl had done some fifty years before.

* * *

Joanne Simpson participated actively in the preparation of her archive for deposit at the Schlesinger Library at Harvard University. She annotated hundreds of photographs and wrote numerous short essays to accompany documents from different parts of her life. Much of the archive relates to her long and active career. She also decided to deposit some very personal documents, including the notes and journal she kept during her relationship with C. She explained her decision to share this intimate material in a letter to the archivist. “My work life is well known but I have deliberately kept my personal life as private as possible and hence if I should die before I finish, the material I am starting to send you now on my personal life would be lost, as little of it is known by anyone else.”76 She decided to forfeit the privacy she had guarded for a lifetime because she believed it was critical to portray the full complexity of her life in science.

As a woman in an otherwise almost entirely male profession, her personal choices had always been subject to public scrutiny—at least those personal choices that she could not hide from outside view. News stories breathlessly reported on her ability to cook and keep a house as well as maintain her professional career.77 Her bold habit of flying through the clouds—and even hurricanes—was all the more surprising since Simpson was, by one writer’s estimation, “a rather wispy and timid-looking blonde,” who, in addition to being one of the top five meteorologists in the world, “runs a big home in Woods Hole, Mass, does all the cooking for her husband and two sons.”78 Despite the sexism, the journalists who wrote these pieces were correct when they noted how entangled Simpson’s home and work lives were. Each of her three marriages was to a man who had emerged from the same small sphere of research meteorology, and her relationship with C. was likewise rooted in their shared experience of scientific work. To deny the centrality of these relationships to her life would be to miss something important. Simpson’s decision to make this intensely personal material available to scholars was taken deliberately. She wanted to make it possible for the full story of her life, in all its complexity, to be told. And she hoped that a time would come when the so-called work/life balance was no longer seen to be a problem only for women, but for all working people.79

For this to happen, the archives will need to reflect the reality of life as it is lived. For now, the evidence of the multiple roles played by male scientists as fathers, husbands, and lovers remains frustratingly hard to come by. In Simpson’s archive, a fuller portrait emerges, of a woman who lived intensely, and indeed passionately, throughout her long and productive life. If she chose to conceal much of the storminess of her private life during her life, in the afterlife she envisioned for herself the true complexity of her life was finally given space to breathe. Like the great clouds she studied, Simpson had allowed herself to grow expansively, sometimes with dramatic speed, into areas that had been presumed to be off limits. Her passions and her science were inseparable. “I think I am generally perceived as a pretty cool character,” wrote Simpson. “Nothing could be farther from the truth. To understand how a woman, or a man, for that matter, creates original work in any field, it is necessary to penetrate the emotional masks, and my masks have intentionally been hard to penetrate.”80