8

CONCLUSION

Arriving at the Bretherton diagram after spending time in the company of the scientists I have profiled, it is possible to see it as an amalgam rather than a singular thing. In a quite literal sense, one can locate within it (and its accompanying text) much of the work with which this book has been concerned. Here, for example, is the Tropical Rainfall Measuring Mission, NASA’s first mission to measure rainfall on Earth, which Joanne Simpson was recruited to run in 1986, the same year that the diagram itself was published. Here too is a mention of the World Ocean Circulation Experiment (WOCE), the global project for which Henry Stommel had laid the conceptual foundation and about which he was deeply ambivalent. Also present is Gilbert Walker’s Southern Oscillation, whose erratic occurrences were still, in 1986, unpredictable (and remain so today), and which exemplifies the importance of studying climatic processes on a global scale. Less explicitly but perhaps more fundamentally, the climatic roles played by clouds and water vapor remain a subject of pressing mystery in the Bretherton diagram just as they did for Charles Piazzi Smyth. And here too is the need to understand the way ice moves and changes shape: whether, as Tyndall had also wondered, it slides on liquid water at its base, and how, in a warming world, its motions might lead to the detachment and melting of the massive West Antarctic ice sheet.

The lives and work of John Tyndall, Charles Piazzi Smyth, Gilbert Walker, Joanne Simpson, Henry Stommel, and Willi Dansgaard were lived, as we live our own lives, in a stream of constantly shifting desire, intention, and chance. As Tyndall felt so acutely, a misplaced step in the Alps could have brought him tumbling down. Piazzi Smyth’s life might have been very different if he hadn’t rashly resigned from the Royal Society. Gilbert Walker had a nervous breakdown from which he recovered, but what if he hadn’t? These counterfactual stories are useful as reminders that the contingency of individual lives has influenced the creation of what might otherwise seem to be a natural object—the system of the earth, the vision of the globe.

Both Tyndall and Piazzi Smyth demonstrated that it was possible and sometimes necessary to make knowledge about the planet alone. The nature of that knowledge, and what it meant to be alone, was negotiable. When he was on top of Tenerife, Piazzi Smyth was imaginatively supervised by a congregation of his scientific peers. Tyndall often climbed “alone” in the Alps in the presence of guides. Making reliable knowledge out of an amalgam of field and laboratory work was never straightforward. Gilbert Walker, in many ways a useful anomaly here, sat at the center of a web of imperially enabled statistics like a calculating spider. His failure to predict the monsoon is less significant than his success at showing how certain powerful modes of calculation depend on unimaginably large networks of observations, networks which are today even more important, and arguably even less visible, than they were for Walker. Understanding how such hidden numbers produce highly visible and influential knowledge—such as the global temperature index—is critically important.

A full history of our understanding of the planet cannot be told solely from the perspective of individuals. Indeed, since World War II the sciences of climate have become bigger and bigger, and the role played by any one individual smaller and smaller. This was the change that Stommel foresaw and lamented. As he saw it, it entailed the loss of freedom that he considered necessary for solving the big conceptual problems. Joanne Simpson encountered the same paradox when she sought to build alliances with government funding bodies in order to do the science she really wanted to do. Cloud modification, much less hurricane modification, was never going to be a solitary endeavor. Similarly, no ice cores get drilled without serious money being expended. Willi Dansgaard had to find a way to harness the budgetary and logistical might of national governments. Piazzi Smyth and Walker, too, both relied on extensive networks to provide them with the necessary equipment and authority to do their work. Realizing that individuals cannot function alone does not mean that individual lives no longer matter to the telling of history. By looking at the interaction between individuals and institutions—between energy at different scales of the system—we come closest to understanding how the system works.

The tools with which scientists study—and then describe—the planet in global terms are influential. They generate knowledge that contains within it both assumptions about who gets to know—who has the training and skill, the moral authority, and therefore the trust to do so—and what that knowledge is good for. This book has conveyed the stories of how scientists have created tools for global knowledge and what was consequential about those tools. While my protagonists are almost all English speakers and nearly all men, they belong to different times, different places and, perhaps most challengingly, different disciplinary histories. I have chosen to do this deliberately, as I wished to show how the thing we today refer to quite casually as climate science is an amalgam of different ways of knowing the earth. This is, in one sense, a good thing, a source of resilience, in that it offers multiple pathways for generating knowledge. For decades, calls for the need for interdisciplinarity have been common, sometimes more strident than others. Despite this, truly interdisciplinary working remains elusive across the natural and social sciences. A recent meta-analysis of twenty scientific assessments of global climate science noted that “only a fifth of the case studies analysed attempt to integrate practical elements [or] consider socio-economic and geophysical aspects across spatial scales.”1 And yet, as this book makes clear, climate science was always interdisciplinary. For better or worse, there never really was a singular discipline of climate science.

Global visions are necessarily made up of unglobal things—individuals, places, moments in time. This is, in itself, neither a bad nor a good thing, but it is a fact about which it is important to be aware. The concept of global knowledge is a powerful one. It may be one that we feel we need today, but this does not make it either neutral or natural. All our global visions are, like the visions described in this book, the products of individual minds working in particular places at particular times—histories that might have turned out differently. Put differently, the same Earth is there for all of us, but, to use a phrase Tyndall might have appreciated, it wears many veils. The tools with which we pull back the veils go, in this book, by the names of the various scientific disciplines into which humans have divided the study of the planet: geology, physics, astrophysics, cosmic physics, atmospheric physics, meteorology, oceanography, paleoclimatology, climate science. Those disciplines organize the methods for thinking and doing science, and in this way they, too, determine what can be known by the people who work within them. There are circles within circles of structure and chance, of painstaking preparation and the unpredictable contingencies of the day. Together, it adds up first to individual lives and the knowledge thereby produced, then to disciplinary consolidation of knowledge, and finally to something like the Bretherton diagram, a synthesis of not just the entire planet but multiple ways of knowing the planet.

* * *

Interdisciplinarity can take many forms. The Bretherton diagram represented the integration of knowledge from across many scientific disciplines. It also gestured toward the need for integrating the social sciences as a means of modeling the role of human factors in the system. The awareness of planetary change that prompted the series of workshops out of which the diagram emerged also prompted a call for another flavor of interdisciplinarity, this time for bringing the science of climate and the traditional discipline of history together.

This awareness was prompted directly by ice cores. Thanks to the magic of isotope chemistry and Dansgaard’s “one really good idea,” ice cores became frozen annals. The earth, it turned out, not only had a history but had kept its own, remarkably detailed, archive. Ice cores, just one member of a remarkable family of paleo-proxies, stand out for their ability to register very long time spans with remarkably high resolution. Indeed, it is possible in some ice cores to read the earth’s history on an annual basis, as a historian might read a church register. This special feature of ice cores made it possible to align human history and climate history in a way never before possible. The earth now had a history that could be directly calibrated to human history. This raised questions, foremost among them how climate affected human history. It was precisely to “evaluate the effects of climate and weather on human affairs in the past” that a 1979 conference on “Climate and History” held at the Climatic Research Unit at UEA brought together 250 researchers from across the sciences, social sciences, and humanities.2

At the conference, several things were clear. One was that the question of influence was a complex, multidimensional one. Different human cultures had responded very differently to changes in climate in different times and places. There was no longer any case for the anyway often-derided species of environmental determinism espoused most prominently by Ellsworth Huntington. Also clear was the need for humans to better understand climatic changes in order to prepare for the future. Less clear was whether humans had themselves also influenced climate. In 1979 at UEA, there was no mention of human-induced climate change. The arrow of influence seemed to point decisively from climate to humans, even as scholars emphasized the contingent nature of that influence. There was no room either for environmental determinism or a possible link between human activity and changes in climate. Such a state of affairs did not last long. Increasing evidence about the effects of human activity on rising carbon dioxide in the atmosphere and new indications that global temperatures were rising made the arrow pointing from humans to climate harder to ignore. But in 1979, at the UEA, such concerns could be, and were, pushed to the side.

Ice cores generated a felt need for communication across the aisle that famously separated the two cultures. “‘Climate and history,’ as a field of study is located at the point of intersection of many different disciplines,” asserted the editors of the conference proceedings, “and progress in the field demands interdisciplinary cooperation.” History here was a term laden with meanings. “Our approach,” explained the editors disingenuously, “is simply to study the history of climate itself, to attempt to reconstruct the pattern of climatic changes and fluctuations over past centuries and millennia.”3 The history of climate, in this sense, could be and often was considered an almost purely scientific endeavor then (save, the editor’s note, for a few special historians, Le Roy Ladurie chief among them, who addressed the question of climatic influences on human history).

In asserting that the history of climate was self-evidently scientific, the editors were stating what they believed was an anodyne truth, a mere cliché. But assertions of self-evidence often betray deep uncertainties. Despite the claim to the contrary, there was nothing natural (in the sense of necessary) about the historical nature of climate as represented by these twentieth-century researchers. It was, instead, the product of its own disciplinary history, as contingent and as un-self-evident as any product of humanity.

Geologists like Charles Lyell and James Hutton discovered the earth’s “deep time” in the late eighteenth century. But, as Martin Rudwick has convincingly shown, perhaps even more important than the discovery of deep time was the simultaneous creation of a new way of thinking about the earth’s past, a new form of historical consciousness that Rudwick calls Earth’s “deep history.” Much more important for our understanding of the planet than a merely expanded amount of time (what geologist James Hutton famously described as having “no vestige of a beginning and no prospect of an end”), argues Rudwick, was a new sense of “the historicalness or historicity of nature.”4 The Bible, with its complex and contingent histories, provided early geologists with a ready model for how change happens over time. From scripture, they borrowed the presiding assumption that the unfolding of the geological history of the earth was a set of contingent events that resembled human history much more than it did the unchanging orbits of the planets described by Isaac Newton.5 This borrowing from scriptural models of history was itself far from accidental. The sense that at every point events could have turned out differently was, argues Rudwick, “deliberately and knowingly transposed into the world of nature” from that of human culture and human history. Among other things, Rudwick’s argument gives lie to the simple conflict stories of science and religion. Far from obstructing the discovery of a deep history of the planet, scriptural understanding “positively facilitated it,” argues Rudwick. Though the editors of the UEA conference volume reduced the historicity of climate to something self-evident (“simply . . . the history of climate itself”), geology was “born” historical in a richer and more meaningful sense. Geology was, from its very beginnings, a science built self-consciously on the model of the most human of all histories, that of the Bible.

Climate science today, inasmuch as it has been built partially on the foundations of geology, contains within it some of this historicity, this contingency. But it also contains a different approach to history, one closer in spirit to Newton than to Hutton. The Newtonian time of planetary objects—history that unfolded in precise cycles rather than stories with surprising turns—has always also been a part of what we can now, retrospectively, label climate science. It informed the calculations by which men like James Thomson estimated the melting of ice under pressure. These physical methods gave rise to the kind of thinking that enabled Broecker and others to start working out the global mechanisms responsible for the rapid transformations in the ice records. This work helped create a new way of thinking about the internal history of climate that came to be called climate dynamics.6 Climate dynamics did not draw explicitly upon traditional historical methods or seek collaboration, as the scientists at the 1979 UEA conference did, with traditional historians in building time lines. Nevertheless, it was a new way of thinking about the climate. Unlike those geologically indebted disciplines which were more or less content to simply describe the unfolding of climate history (for example, classical climatology and many aspects of meteorology and oceanography before the postwar period), scientists interested in physical dynamics wanted to generate a causal understanding of how the pieces of a system connected and how those connections generated phenomena that could be measured. Doing climate history here entailed understanding the causal relations between physical phenomena rather than “merely” describing them. According to this way of thinking, the movements of water, air, or ice had histories that could be generated not through observation and description alone but through the correct application of physical principles. Henry Stommel’s paper on the westward intensification of boundary currents is the locus classicus for this sort of thinking within oceanography. It not only captured the drive toward understanding physical phenomena that lay at the heart of this kind of climate history, but demonstrated the value of simplicity in this new arena.

In this sense, scientists who studied the dynamics of climate were also self-consciously historical. While there was always uncertainty about the precise path that the climate system followed—a real sense that things could easily have unfolded differently—the science of climate dynamics emphasized not this uncertainty, but the links between elements of the system. In other words, they were more concerned with what could be explained causally, in terms of physical dynamics, and less with what was—at least theoretically—fundamentally unpredictable. In that sense, it seems fair to consider them to be historical in their approach, different as it was from the chronological descriptive framework of the classical climatologists. When the uncertainty became more than noise, new theories to account for it had to be developed. Chief among these was the meteorologist Ed Lorenz’s description of the chaotic features of certain systems, atmospheric ones in particular. Chaos, as Lorenz understood it, was a way to introduce unpredictability into a system without descending into randomness, “mere” contingency. Chaotic systems are far from random. Instead, they circle around certain stable states while never setting into a fixed rut. But they are unpredictable, confounding the physicist’s ambition to make good on the Newtonian promise of perfect knowledge predicated on a keen enough knowledge of initial conditions. Lorenz showed that in chaotic systems, initial conditions could never have been fine enough to preclude the possibility for uncertain outcomes. In exchange for some knowledge, perfect knowledge was ceded.

* * *

The search for simplicity is a recurring theme in much scientific effort, not least when facing the confounding complexities of swirling air and water. If the grail of simplicity had a home, it would be a wooden cabin at the tip of Cape Cod, on the campus of the Woods Hole Oceanographic Institution. There, every summer since 1959, a group of scientists have gathered to hash out the simplest ways to describe the motions of fluids on planetary scales. This seminar is called GFD, for geophysical fluid dynamics, and it is an approach to understanding the motions of planetary fluids that has influenced (and been influenced by) much of the science described in this book.7 It is significant that this conceptually reductive approach to earth science has been nurtured in an un-insulated wooden shack into which can fit no more than two dozen researchers crammed in a motley assemblage of folding chairs and surrounded on three sides by chalk boards. The size of the cabin is important because it has constrained the size of the community. There are not too many scientists who focus on geophysical fluid dynamics, compared, say, to the number of people involved in computer modeling or the even larger numbers of field scientists studying the multifarious aspects of climate. Most have attended the GFD summer school, which has been running for fifty-nine years. The walls of the cabin can remain uninsulated because GFD is only a summer school. It exists from June to August each year and goes quiescent, save for a minimum of administrative functions, until the next year. The aim (and result) is that GFD sits between a variety of disciplines—the very disciplines described in this book. Oceanographers, meteorologists, atmospheric physicists, and glaciologists are among those who apply to study or lecture here. They leave having absorbed a particular way of seeing the planet, which they apply in the course of their doctoral work, postdocs, and subsequent careers.

The GFD seminar emerged out of a joint seminar series hosted in the fall of 1956 by WHOI and MIT. On the MIT side, the seminar was attended by Norman Phillips and Jule Charney, both of whom had recently moved to MIT from the Institute for Advanced Study in Princeton, where Charney had been running the numerical weather prediction work that John von Neumann had championed. Ed Lorenz, a meteorologist, also attended. On the WHOI side, seminar attendees included Henry Stommel, Joanne Malkus, her then-husband Willem Malkus, and Fritz Fuglister (who did the early observations on eddies in the Gulf Stream). Carl-Gustaf Rossby, then visiting WHOI, also participated. Thus a high concentration of the mathematically inclined oceanographic and meteorological community (who might be called, for convenience’s sake, theoreticians) spent two hours together every two weeks, alternating between Woods Hole and Cambridge, MA, not including the dinner afterward and the car ride between the venues.

At these seminars, a shared language and shared set of interests in understanding the fluid dynamics of the atmosphere and oceans emerged. So too did the idea for a summer school to train graduate students in this way of thinking. In the fall of 1958, George Veronis, Henry Stommel, and Willem Malkus drafted a proposal for a GFD summer school on the topic of “Theoretical studies in geophysical hydrodynamics.” Both Joanne Malkus and Henry Stommel were early advisors, though Joanne stopped attending after her divorce from Willem Malkus, who remained closely involved. Stommel attended for several years. Both exemplified the ethos of GFD. They sought physical insights into the motions of air and water that could explain the complexities of the world in the simplest terms possible.

The first program consisted of four students and six invited staff, in addition to WHOI members. Rather than teaching a set curriculum, the program consisted largely in seminars describing the work currently being tackled by the staff. Questions were not merely tolerated but encouraged, and the emphasis was not so much on conveying a set body of knowledge but on students and staff together exploring interesting research questions. Stommel and Alan Robinson talked about their recently developed theory of the so-called thermocline, or strata of the ocean in which the temperature dropped dramatically. Joanne Malkus gave a talk on cloud physics. The presiding ethos was of equality. This egalitarian spirit remains as strong as ever as the seminar completes its sixtieth anniversary, with constructive interruptions welcomed at the seminars and a spirit of constant questioning that breaks down barriers between students and faculty.

* * *

The impact of the GFD seminar on shaping our understanding of how oceans, ice, and atmospheres move has been large. But the history of climate science has been just as much a story of increasing complexity as it has been of the simplified visions of the GFDers. As important as the Bretherton diagram was, it has long since been surpassed in importance by another kind of global vision in which the values of both simplicity and complexity can be inscribed. It is this global vision—even more than the glamorous image of our “blue marble” against the inky black of space—which has been responsible for shaping how we think about the earth’s climate. This is the General Circulation Model (GCM), a complex simulation that tries to reproduce the dynamics of the earth system by calculating how a grid of data points respond to a set of physical equations. Like Jorge Luis Borges’s ironically “perfected” art of cartography in which a map of an empire occupies the entirety of an empire, these GCMs aim to cover the globe as completely as possible. Instead of paper, they use imaginary grids whose resolution improves with each rise in computer processing power.8 Time is another factor in climate models. While it would be possible to run a more highly spatially resolved climate model by taking bigger increments of time, scientists have generally used time steps of thirty minutes to run models over a century or more. This translates into 1,753,152 steps at each of the grid points of any given model. For each grid point, a series of what are called model parameters—values for temperature, wind speed, pressure, humidity, and so on—would also need to be calculated. Multiplying these three sets of numbers by each other—the number of time steps, the number of points on a grid, and the number of values for each point—quickly generates an almost unimaginably huge number of calculations. For the most finely resolved GCMs currently in use, the number of calculations needed to run the model for a century taxes even the fastest and most powerful computers in the world. As a rule, doubling the resolution of the model results in ten times more calculations being required.9 Like thirsty behemoths, these models suck up all the available computing power with each advance of Moore’s famous law.

GCMs have had notable success in reproducing certain aspects of the climate system, such as the great ocean and atmospheric currents, the pulsing growth and decay of ice caps, and the distribution of atmospheric carbon dioxide. Other features—particularly those operating on small spatial or temporal scales—are harder to capture, even using the largest computers available. The resolution of these kinds of GCMs is currently some 100 kilometers. Anything smaller—a cloud or a small ocean eddy—gets missed out. (Since clouds are key aspects of the global climate system, scientists have worked hard to find other ways of including them. They do this by parameterizing—by finding mathematical shorthands for summarizing the effects of clouds. These are useful tools and better than ignoring such small-scale features altogether, but they are also limited.) The complexity of these model worlds (and there are dozens of them, to complicate matters even more) is such that climate scientists now worry that they are in danger of forgetting that they are not studying the actual earth but a model version of it. Getting lost in the byways of a GCM, they are at risk of losing sight of the real aim of these models—to understand our own planet.10

There are other climate models that sit at the other end of an imaginary spectrum of models. These simple models seek not so much to simulate climate as to provide a useful medium for exploring it. A good example of one of these is the energy–balance model of the kind Joanne Simpson and Herbert Riehl used to “discover” hot towers. By eliminating as much detail as possible, these models obey an opposite epistemology to the GCMs. Taking away as much as can be taken away to leave the essential features of the climate system intact offers a powerful kind of vision. This tradition is an old one—stretching back to the work of men such as Croll, Ferrell, and James Thomson. It often has a counterfactual quality, playing around not with the aim of approximating the earth but of imagining alternative earths. Oceanographer John Marshall’s aqua planet models do this well.11 Marshall asks what the earth’s climate would be like if its entire surface were covered with water. Letting this model spin out through 5,000 years, he finds that it eventually falls into a settled climate regime—an ice cap forms on both of the poles. Marshall runs the experiment four times, each time adding a line to represent the simplest possible landmass, which serves to interrupt the flow of water around the planet. With four simple variations, Marshall is able to test the importance of landmass distribution on ocean circulation and climate regime—to better understand whether a planet will experience fixed ice ages, oscillating ice ages, or descend into a permanent snowball state.

In theory, between simple models like these aqua planets and complex GCMs lies a series of intermediate models of increasing complexity. The climate system is so complex, according to those who promote the so-called “hierarchy of models” approach, that we need a system of nested models to understand the many scales on which energy flows through the system. The “answer” to the big questions of climate science, according to this view, lies not in any particular model but in the different understandings that each of these hierarchically arranged models enable.12

* * *

Today, climate scientists are intensely self-conscious about not only their disciplinary but also their epistemic identities—how they know what they know. At conferences which aim for interdisciplinary thinking, it is normal for scientists to preface comments by saying “as a modeler” or “as a theoretician,” and so forth. Such thinking was also present, in a different guise, in the dispute between Tyndall and Forbes over the nature of glacier motion. Walker struggled with the limitations of statistics to generate physical understanding. And so too was it present in the concerns of Stommel and Simpson to find the correct balance between observing the complex phenomena of the ocean and atmosphere and finding ways to describe it using the special pithiness of math and physics. The interplay between people “doing” observing, people “doing” theory, and people “doing” modeling has been a central theme to this book. A self-consciousness of the need for balance (where what counts as balance is itself a moving target), rather than a recipe for precise ratios, is a consistent feature of the 150 years of history covered here.

While it is tempting to assert an increasing mathematization of the earth sciences—along the lines of GFD—it seems more accurate to say instead that the need for iteration between theory, observation, and modeling has intensified, and the cycle has sped up. Theorists need data, as much if not more of it than they ever did. And those who generate data—through observations or through modeling—need theory with which to shape their research focus and even, as Paul Edwards has convincingly explained, to see their data at all.

Historians tend to be jumpy about the risks of something that goes by the name of presentism. The tendency to see the past in light of the present is seen as a Bad Thing—blinding us to the truth of the past by seeing it with our foreign eyes. But presentism is inevitable. We cannot escape from the perspective from which we view the past—that is, right now. Rather than struggling to deny this perspective, we need to face it head-on. In light of the environmental challenges facing the world today, we urgently need to think hard about the relationship between the present and the past. Any fears about how we are blinded by our present prejudices seem increasingly less significant than the risk of depriving ourselves of the best tools we can use for imagining the future.

The uses of history to imagine possible futures can go by many names. The past is sometimes looked to as a source of lessons, or case studies, like the climate analogues sought by paleoclimate scientists or old weather patterns used to make new forecasts. We can learn from equivalent moments in the past and (the implicit suggestion seems to be) avoid making the same mistakes. A somewhat more nuanced approach seeks to use the past not as a cheat sheet for future events but as an exercise in imaginative stretching—a way to prepare us to see differently, to use the difference of the past to help us conceive of the future with more options in mind. Anticipatory history is one term for this, developed by those engaged in thinking about how to manage real things—often heritage sites—whose location in the landscape makes them literally susceptible to imminent change.13 This forces the mind to focus on the issue when it might otherwise skirt it. When it comes to history of climate, the problem and the application are less clear—our scientific practice doesn’t feel under threat by climate change in the same way that our landscape does.

But if we think about this harder, perhaps science is under threat. Not, I think, only from those who seek to undermine its authority to speak, though this threat is real and stubbornly hard to dispel. Instead, climate science may be at risk from a lack of self-consciousness. What climate science seems to need is a vocabulary for making explicit what are usually implicit assumptions about the values that inform it. There are many such values embedded in the doing of science, but the historian in me would like to make a special plea for examining the nature of the histories implicit in our view of climate.14 What, for example, counts as history in climate? Which tools, both conceptual and material, are used to generate such histories? What moments do they render meaningful, and which are ignored or erased? These questions—which we’ve only just begun to ask—are essential to determining what we care about when it comes to climate, and the answers to them will form the basis—whether we realize it or not—of our responses to the changes we face.

The historical senses that are embedded in climate help determine what counts as normal when it comes to climate. Determining what is a natural climate is a key focus within climate science and policy today. As we learn more about how the climate has changed in the past and consider how it might change in the future, we rely on assumptions about what a “good” or “natural” climate might be. These assumptions have so far been defined by those who study the earth’s past. These are not historians but scientists who look to past records of climate change to determine both what we can expect and what we should be happy to accept. How much change is acceptable may be a partly scientific question, but it is not only that. What counts as acceptable changes depends signally on where you draw your frame.15 The past 12,000 years of history, called the Holocene, have been, in the context of the preceding millions, both unusually stable and unusually warm. This happens to be the period in which human beings evolved. Do we have a responsibility to maintain this particular climate? There are even more versions of normal if we broaden our population of those who have the right to determine the answer to this question beyond climate scientists alone.

Stating that there are many different kinds of knowledge would seem to be a recipe only for dispute of the partisan kind that has caused a crisis of trust, or in some cases an outright rejection of the values of science. Science, in this point of view, is under threat and must be saved by its own methods—by proving with evidence that it “works,” which is to say that it can make meaningful predictions. In another sense, understanding the many-strandedness of science can offer a way toward understanding something even more fundamental—the limitations of science. To acknowledge the limits of science need not be an exercise in abnegation. It can open up new ways forward. Identifying the presence and necessity of various values within science, such as the importance of interestedness, commitment, emotional connection, and self-determination, provides a better understanding of what science is. This clears the way to recognizing that the decisions which we make as a society about how we live on the planet can be informed by scientific values without being determined by them. Our choices about how we use energy, how we dispose of our goods, how we live with and in the landscape, have always been about so much more than, for example, our understanding of the ice ages, or our ability to predict the weather.

* * *

The nature of the relationship of climate and history has become both a key political issue and an unresolved scientific question. The earth is now self-evidently a planet of change. The past is now always a resource for the future. Scientists now seek to understand the dynamics of the climate in the past, based on paleo records, in order to better understand how it might change in the future. Politically, the question of what futures are available to us—of what futures we imagine—is also partly constrained by this scientific understanding of climate dynamics in the past and future.

The dance goes on. The Bretherton diagram, influential as it once was, now looks dated and clunky. From a focus on understanding the components of the earth “system,” as the NASA engineers considered it, a new way of looking at the planet emphasizes not the boxes, so to speak, but the arrows between them.16 Feedback loops and their associated tipping points have come to the fore. The artificiality of distinctions between elements of the system have given way to a new sense that there can be no substantive distinctions between aspects of the whole. It is all connected in such deep and complex ways that only by studying the connections can any sense of it be made. Some may argue that a study of connections implies also a study of discrete elements, but the emphasis seems to have shifted. The “essential oneness” which Victor Starr drew attention to some sixty years ago is a recurrent theme, but one which, it seems, every generation must arrive at independently.

The scientists whose work I’ve described in this book were each, in their own ways, playful in their approaches to knowledge—they treated the planet as an arena for exploration. Walker’s throwing of the boomerang is the most literal form of play described here, and all the more striking against the austere backdrop of his mathematical intensity. Tyndall was playful, too, in ways that were always testing—his own appetite for risk, the forbearance of his peers with his tendency to dispute, the delicacy of his apparatus as he asked it to answer increasingly difficult questions. Piazzi Smyth played with authority—his own, his instruments’, and what we might now call the “truthiness” of images. In seeking knowledge in the most evanescent of phenomena, he played with his own desire for understanding, challenging himself ultimately to accept on faith what he could not prove. Joanne Simpson played in the arena of the sky, using whatever tools she needed—from airplanes to hand-calculated models to her own cloud photographs—to get to the physics she sought. Henry Stommel was playful in his making and his thinking, tinkering with things as he tinkered with ideas, using his mind as a telephoto lens that zoomed in and out, and across the oceanic landscape, seeking problems he thought worth thinking about. For Willi Dansgaard, the icy landscape of Greenland hid a frozen past across which his mind could wander at will, thanks to his one “really good idea.”

Work, for these individuals, was a quest, at once playful and completely serious, that took place across decades and landscapes both mental and physical. Following water, and the heat it held (or held traces of), they drew trajectories through time and space just as the molecules they studied did. Their playful exploring was, in its seeking, searching quality, elevated by a poignant sense of longing—for more knowledge, more time with which to study the planet, more freedom in their work, and more tools with which to see deeply. Play, for these individuals, was an avenue for something serious, something big. They each, in their own way, sought something deeply meaningful from their engagement with the planet. So should we all.