The Green Marble

In every age there is a turning point, a new way of seeing and asserting the coherence of the world.

—J. Bronowski (1974)

THE CHALLENGE OF GLOBAL ENVIRONMENTAL CHANGE

Planet Earth can seem quite small. It takes only 90 minutes for an Earth-orbiting satellite to accomplish one global circuit. A single photograph can capture the entire Earth, with recognizable continents and oceans. Google Earth can take the virtual you nearly instantaneously to the top of Mount Everest or the depths of Death Valley.

Size is relative, of course, and in a sense our planet is rapidly becoming ever smaller. With the existing global transportation and communication networks, we can physically make our way to almost any location on the face of the planet within a day or two. The Internet allows us to communicate in text, sound, and images with billions of people around the world. The media keep us informed of breaking news locally and globally. In my professional life, satellite data give me near real-time information on weather and major biosphere disturbances everywhere on the planet.

The Earth is getting smaller in other fundamental ways. Until very recently, our species had only a minor influence on the global biogeochemical cycles of water, carbon, nitrogen, and other elements critical to life. However, in the past century we have become one of the dominant forces in those cycles (W. C. Clark, Crutzen, and Schellnhuber, 2004; Vitousek, Mooney, Lubchenco, and Melillo, 1997b). We are increasing the atmospheric carbon dioxide (CO2) concentration by burning fossil fuels and converting forest land to cropland. Industrialized agriculture and fossil fuel combustion are now introducing into the environment more plant-available nitrogen per year than is produced by natural processes. We now use in one way or another 50 percent of global freshwater flow in streams and rivers. These anthropogenic impacts on the environment are changing the operation of the Earth system in ways unfavorable to advanced technological civilization (Barnosky et al., 2014). Perhaps more ominous in the long run than our influences on the global biogeochemical cycles is that we are driving species of plants and animals extinct at a vastly higher rate than is indicated in the paleorecord over much of evolutionary history.

As ecologists have said for decades, the problem starts with a human population that has been increasing for roughly the past 10,000 years—since the end of the last ice age. There are now over seven billion of us, and the projected balance of births and deaths will likely continue to favor population increase throughout this century. Equally significant, the ecological footprint per individual—i.e., per capita resource consumption—has increased dramatically in parallel with the number of people. About 20 percent of the global population has achieved a moderate to high standard of living (albeit leaving billions living quite precariously), but the cost in terms of environmental degradation has been enormous (MEA, 2005). If several billion additional people attain what is considered the modern lifestyle by exploiting resources in a manner similar to the lucky two billion, humanity will soon be living on a planet of weed-like species with a warmer climate than has been found on Earth in over 30 million years.

In recent decades, we have begun casting around for ways of thinking that might ameliorate our perverse impact on the environment and change the current trajectory. In broad terms, one aspect of the solution is to “think globally.” That slogan traces back at least as far as the “think global, act local” motto of Friends of the Earth, an environmental organization founded by activist David Brower in 1969. “Think Global, Act Local” was also the title of an influential essay published in 1972 by French microbiologist René Dubos (1901–1982). He promoted the concept at the United Nations Conference on the Human Environment in 1972.

The meaning of the “act local” part of the aphorism is straightforward. It means to work at saving specific geographic areas from environmental degradation. Friends of the Earth is built around the concept of people in specific areas organizing to protect those areas. To “think global” is the other side of the coin (Mol, 2000). It could be interpreted as an admonition to be aware of global-scale environmental problems, such as climate change, that are a manifestation of many local decisions. The expression serves as a reminder to foster solidarity on environmental issues among the wide variety of human cultures dispersed around the planet (N. Gough, 2002). However, to think at the global scale remains a challenge. In part this is likely because our brains were designed by biological evolution primarily to apprehend and respond to local events over short time frames, usually involving small groups of people and simple cause-and-effect relationships (Ehrlich and Ehrlich, 2009). Thinking about global environmental change inevitably requires us to stretch our capacity for imagination and for abstraction. This book is an effort to develop a foundation for thinking globally.

IMPACTS, FEEDBACKS, AND GOVERNANCE

We will pay special attention to three intertwined themes.

The first is human impacts. Earth has existed for more than four billion years. At the time of our recent arrival, it had evolved a well-established biosphere and a complex web of global biogeochemical cycles. However, humanity is rapidly changing how the Earth system operates. We are said to be entering a new geological period—the Anthropocene (Crutzen, 2002; Crutzen and Stoermer, 2000). In seeking to manage our global-scale impacts, we must understand the background functioning of the Earth system and the relative magnitude of our influences on it. Reciprocally, human-induced changes in the Earth system are beginning to negatively impact human welfare, and projections to 2100 and beyond suggest much worse to come.

Second is the concept of feedback. In common usage, the term refers to a reply or comment that conveys an evaluative message. A teacher gives students feedback on their essays. More formally, it refers to reciprocal interactions between different components of a system. In a negative feedback relationship, a change in one part of a system induces a change in another part that dampens the original change. This type of feedback is seen when an increase in the atmospheric CO2 concentration induces an increase in biosphere photosynthesis, which then increases the rate of CO2 uptake from the atmosphere and dampens the CO2 rise. The alternative is a positive feedback relationship in which the original change induces a change in another part of the system that amplifies the original change. This is seen when climate warming causes more forest fires that increase emissions of greenhouse gases. With respect to the Earth system, we are especially interested in feedback relationships that regulate the global climate; these include biophysical processes that change with climate warming and serve to amplify or dampen the warming. The study of Earth’s history and recent dynamics offers many clues.

The last theme is governance—specifically, global environmental governance. The meaning of “governance” is more inclusive than “government” because the former accounts for a broader range of actors in the self-regulation of a social body. A system of global environmental governance will ultimately include intergovernmental organizations, states, civil society, and engaged citizens. A critical question here is how to build an institutional framework to manage the relationship between humanity and the rest of the Earth system.

THINKING METAPHORICALLY

Considering our inherent difficulty in thinking globally, perhaps a good way to start is simply in terms of familiar similes and metaphors.

Probably the most deeply rooted metaphor about Earth is the vision of Earth as mother. We can intuit that cave painters of the prehistoric era, by going underground, were attempting to connect with the generative power of the Earth—possibly in the belief that through their drawings they were fertilizing it (Frankl, 2003) or releasing the animal spirits within (Lewis-Williams, 2002). We of course cannot know for sure what they were thinking, but even among extant hunter-gatherer cultures there is often a sentiment of reverence for Earth’s fecundity. The mother metaphor is still used widely in contemporary culture: Mother Earth was referred to in the Paris Agreement on climate change, James Lovelock chose Gaia (the Greek goddess of Earth) as the name of his revolutionary hypothesis about planetary homeostasis (which we will examine in chapter 3), and one of historian Arnold Toynbee’s mighty tomes was titled Mankind and Mother Earth.

Cultivation of plants for food began about 10,000 years ago, a step that introduced a fundamental change in the relationship of humans to their environment. In the hunter-gatherer era, the bounty of nature was there for the taking. With cultivation, the change was made to actively managing nature. At that point, the reigning metaphor became Earth as garden. This was not the Garden of Eden, but rather the garden that produces dinner. In a sense, cultivation began our separation from nature because we became the subject and Earth became the object that we sought to control. But cultivation also requires a certain intimacy with nature because we are motivated to understand it (albeit to exploit it more efficiently), and possibly protect it (to ensure a harvest).

The urge to understand nature, so as to better manipulate it, led to the discovery and rapid expansion of the scientific worldview in recent centuries. The dominant metaphor has thus become Earth as machine. Enlightenment-era French philosopher René Descartes (1596–1650) described both the human body and Earth itself as machines. In that view, we have a mostly instrumental relationship with the natural world and manipulate it as needed for our own objectives. The key feature of the machine metaphor is reductionism. We take nature apart, identify the mechanisms that drive it, and reorder them to meet our needs. A key weakness is that a machine is made by an agent outside the machine, but in the case of Earth, humanity is a part of the Earth system.

In recent decades, the consequences of the machine metaphor have become manifest on a global scale through pollution, natural resource degradation, and environmental change. The latest mythological figure evoked to characterize our relationship with the Earth is Medea (Ward, 2009). She was the mother in Greek mythology who killed her children. Along with the Gaia hypothesis, we will consider the Medea hypothesis in chapter 3.

Alternative models that have emerged as antidotes to the reductionist thinking of the machine metaphor include Earth as home and Earth as system. The iconic image of sunlit Earth against a background of endless dark space (the “blue marble”) has become a reminder of Earth’s beauty and fragility. An especially poignant early photograph of Earth from space was made from the Apollo 13 spacecraft as it limped back from an unsuccessful mission to the moon. Traditionally, a home is worth preserving and, if necessary, worth fighting for.

The power of the system metaphor is in identification of structures composed of parts and wholes, and finding the causal relationships and feedback relationships among the parts and between each whole and its environment. Humans are just one part of a larger system in this view. The emerging field of Earth system science aims to disentangle the hierarchy of parts and whole that make up the Earth system, to model the dynamics of this system’s behavior, and to inform the evolution of a sustainable global civilization.

THE SEMANTICS OF THE SPHERES

One way to think about parts of the Earth system is in terms of spheres, and to continue our project of thinking globally in a more scientific sense, let’s consider the sphere. Perhaps the most characteristic feature of Earth is its roughly spherical shape. This geometric form is quite common in nature and remarkable in any of its manifestations (Volk, 1995). The most startling thing about the sphere is its symmetry. From the perspective of energy balance and materials cycling, the sphere is a satisfying object of study because there is closure; i.e., it can readily be studied as a whole. An additional intriguing feature of a sphere is what happens on its surface as substances or energy forces grow and distribute themselves. First, density gradually increases; but once the surface is covered, the pressure of interaction increases, and the likelihood of new phenomena is enhanced.

Awareness in the Western world that we live on a sphere traces back to the Greek philosophers. Pythagoras (570–490 BCE) observed that mast tops appeared first when ships came into view on the horizon. Aristotle (384–322 BCE) knew that different stars became visible as a person traveled south, and observed that the Earth cast a curved shadow on the moon. Eratosthenes (276–194 BCE) estimated the circumference of Earth based on simple observations of shadows and use of trigonometry. Other early civilizations also had well-developed astronomical theories that included a spherical Earth. After the Copernican revolution in sixteenth-century western Europe (tracing back to Islamic astronomers), the idea that the Earth is a planet orbiting a star became part of the foundation of our global intellectual heritage.

The basics are that we live on a rock (the geosphere), the third rock from the sun. Earth’s surface is two thirds water (the hydrosphere) and one third land, with 10 percent of the total land area currently covered by snow and ice (the cryosphere). Above us is the atmosphere, a layer of gases some 60 kilometers thick that consists mostly of an inert form of nitrogen, a reactive form of oxygen, and small concentrations of CO2, methane, and other trace gases. Below us are the pedosphere (the soil) and the lithosphere (the Earth’s crust). Several other spheres that greatly concern us in this book include the biosphere, the technosphere, and the noösphere. Later chapters explore these concepts in depth, but the following overview will briefly introduce them. A Lexicon of the Spheres appearing after chapter 11 defines these and other terms.

The Biosphere

Within the geophysical sciences tradition, the concept of the biosphere denotes the totality of life on Earth. The biosphere is an entity in the sense that it plays a major role in the global biogeochemical cycles. Life originated on the Earth relatively soon after the planet coalesced, between four and five billion years ago. Beginning about two billion years ago, there is evidence in the paleorecord of something that could be called a biosphere. By that time, microbial photosynthesis had led to a major change in the chemistry of the Earth’s atmosphere—the conversion from an atmosphere most likely dominated by methane to one that included significant oxygen and CO2. Since microorganisms were the source of the oxygen, this transformation was unequivocal evidence that living organisms were altering the physical and chemical environment at the global scale. As we shall see, the biosphere has strongly influenced the concentration of greenhouse gases in Earth’s atmosphere throughout its history.

The spontaneous emergence of the biosphere from the geosphere was an extraordinary cosmic event (more about that in chapter 2). Such a thing could not be predicted from the laws of physics and chemistry as we know them (Kauffmann, 1995, 2008). James Lovelock noted the equally remarkable fact that the biosphere has gone on to survive for billions of years since its origin despite numerous devastating collisions with asteroids and comets; episodes of “Snowball Earth,” when ice covered most or all of the planetary surface; episodes of much warmer climate than our current conditions; and a 25 percent increase in the intensity of solar radiation associated with an aging sun (Lovelock, 1979).

The biosphere is now enduring a form of disruption to which it has not previously been subjected. Notably, Earth’s climate and the ocean chemistry are being rapidly altered, and extensive land cover change and resource exploitation are causing a wave of extinctions. The driving force this time is not the impact of an asteroid or an episode of intense volcanism, but instead the activities of a particularly industrious primate species known as Homo sapiens. Humans evolved like any other species, but developed a new trait—capacity for language—that initiated a new form of evolution, i.e., cultural evolution. Language introduced the ability to transmit information efficiently both vertically (across generations) and horizontally (among individuals across space), and that trait has created a new world order (McNeil, 2000). Whether you call it management or mismanagement, humans have begun to exert a strong influence on the Earth system as a whole.

The Technosphere

Although various animals use tools on occasion, modern humans have taken tool use to a level that is qualitatively different from anything else found in the animal kingdom. Over the last few hundred years, a layer of physical artifacts associated with tool use has gradually accumulated on Earth’s surface (Zalasiewicz et al., 2016). This “technosphere” began with objects such as stone axes and primitive dwellings. However, as human populations grew and technology evolved, the technosphere has morphed into a ubiquitous mesh of buildings, machines, and infrastructure for communication and transportation. The image of the Earth at night (the “black marble”) nicely captures the density of the technospheric web.

Again, from a geosciences perspective, we can think of the technosphere as a component of the Earth system, even as a kind of living thing. Cities are the organs of its body, highways are its blood vessels, and wires are the conduits of its nervous system. The technosphere ingests matter and energy. It consumes prodigious amounts of fossil fuels and appropriates a significant proportion of the biosphere’s primary and secondary (i.e., consumer) production. Its outputs include the cornucopia of food and manufactured objects we associate with contemporary civilization. Its outputs also include large quantities of waste products, many of which are accumulating in the atmosphere, geosphere, and biosphere rather than being recycled (Haff, 2014). Of particular note, of course, is CO2, a greenhouse gas and the product of fossil fuel combustion that is driving global climate change.

Like all living things, the technosphere grows. Although that growth was relatively slow from generation to generation over many centuries, it has greatly accelerated since World War II (Hibbard et al., 2007). This recent growth of the technosphere has raised standards of living for billions of people, but at a high cost to the biosphere. An increasingly urgent question confronts us: Can the technosphere be transformed into something that continues to provide goods and services to billions of people without degrading the biosphere and disrupting the climate system?

The Noösphere

French paleontologist and priest Pierre Teilhard de Chardin (1881–1955) is the writer most commonly associated with the development of the noösphere (NOH-uh-sfeer) concept (Sampson and Pitt, 1999; D. P. Turner, 2005). The “noos” part of the word is a Greek root referring to mind. For Teilhard, the noösphere was a sphere of mind, the totality of all human thought (Teilhard de Chardin, 1959/1955).

Teilhard’s ideas about the noösphere were influenced by World War I (he was a stretcher-bearer). He saw that rapid advances in the technology of communication and transportation were in a sense “compressing” humanity. Teilhard observed that we live on the surface of a sphere and that the increasing density of humanity and the technology-driven intensification of interactions among us were creating a kind of psychic pressure. World War I was a manifestation of that pressure. Teilhard imagined that when the pressure became great enough, a transformation or unification would occur—the noösphere would coalesce.

Teilhard’s book The Phenomenon of Man introduced the noösphere concept to a broad audience and was widely read. His writing received enthusiastic responses from some philosophers and scientists (e.g., Huxley, 1958), one appeal being its broad scope. Teilhard took a mostly scientific view of the history of the universe, and there is an undeniable philosophical comfort in his notion that humanity is a product of cosmological and biosphere evolution, thus in a sense at home in the universe. Systems theorist Stuart Kaufmann has elaborated on that perspective more recently (Kaufmann, 1995). In popular culture, Teilhard’s noösphere concept has been evoked in relation to the development of the Internet (Kreisberg, 1995). His ideas about the tightening social integration across all of humanity, driven by advances in communication technology, fit well with the emerging role of the Internet as a reservoir of information and a means for global communication.

Russian biogeochemist Vladimir Vernadsky (1863–1945) conceived of the noösphere in a way that was radically different from Teilhard’s concept. Vernadsky was one of the first scientists to quantitatively study the global biogeochemical cycles, and he offered a refreshing nondualistic interpretation of noösphere (Vernadsky, 1945). He recognized the growing magnitude and pervasiveness of human impacts on the planetary surface, likening them to a geological force. This new geological force was guided by mental phenomena rather than by strictly physical, chemical, or biological processes. Thus, a new way of characterizing the Earth system was needed. Vernadsky envisioned the noösphere as a new form of the biosphere, a biogeochemical cycling entity that included all life as well as its associated atmosphere and lithosphere. His noösphere was one dominated by human influences and serving primarily to meet the needs of humanity.

Vernadsky’s noösphere concept, like Teilhard’s, has received significant criticism. In the late 1950s, American ecologist Eugene Odum categorized the notion as “dangerous” because it implied that humanity was ready to take over management of the biosphere (Odum, 1959). Odum worked several decades after Vernadsky’s death and was perhaps in a better position than Vernadsky to see that humanity’s dominion over the biosphere might not be so benevolent. Homo sapiens needed no encouragement in believing it was wise enough to manage the Earth at a global scale. Anthropologist Gregory Bateson (1979) noted that there may well be a global system, but the nature of systems is such that a part (humanity) cannot control the whole (the Earth system). Nevertheless, the arrival of human consciousness does represent a qualitative change in how the Earth system functions, and it seems worthwhile to retain the term noösphere in that context. We may well wonder, too, if other noöspheres exist in the universe, in galaxies where self-aware life forms have evolved and come to manage (or mismanage as the case may be) their planetary biogeochemical cycles.

The Technobiosphere

Since Vernadsky’s time, we have made considerable progress in quantifying the chemical pathways and the flux magnitudes of the global biogeochemical cycles. It is now obvious that human activities profoundly alter these cycles. In effect, there is a growing coupling of the technosphere and the biosphere. One might refer to this contemporary fusion as the “technobiosphere” (D. P. Turner, 2011). Energy inputs to the coupled system are a combination of solar energy and fossil fuels, and a key mode of interaction between the biosphere and the technosphere is the global carbon cycle. Anthropogenic (human-initiated) transfers of carbon to the atmosphere by way of fossil fuel combustion and deforestation have become a significant flux (i.e., flow) relative to background biologically driven fluxes such as global vegetation growth (Roy, Saugier, and Mooney, 2001). Much of the primary and secondary (consumer) productivity of the biosphere is now ingested by the technosphere in one way or another (Vitousek et al., 1997b). Through management of natural resources, the coupling of the biosphere and technosphere is becoming ever more integrated.

Whether the technobiosphere can become sustainable is an open question that we will examine is this book. Sustainability is admittedly something of a poorly defined buzzword. According to the Rio Declaration (United Nations, 1992), promulgated by the international gathering in 1992 to examine global change issues, sustainable development will “equitably meet developmental and environmental needs of present and future generations.” The term is commonly applied at a range of spatial scales, including the global scale (Sachs, 2015). However, the prospects for achieving sustainability at the global scale are as yet unclear.

BIG HISTORY

Given these key structural terms, let’s consider the dynamics of the Earth as a whole, as an entity. The history of the geosphere, the biosphere, and the technosphere can be cast as a narrative. This chronicle includes the geological history of Earth, the biological evolution of life and the biosphere, and the cultural evolution of humanity. Thinking at the global scale thus forces us to juxtapose the astronomer’s time frame of cosmic evolution (14 billion years), the geoscientist’s time scale of Earth history (four billion years), and the historian’s time frame of human development (approximately 10,000 years). The emerging field of “big history” has taken on this challenge (Chaisson, 2002; D. Christian, Brown, and Benjamin, 2013). The theme of increasing complexity is often used as the organizing framework in the big history literature, especially in academic courses designed to give students a cosmic perspective on the human condition. Increasing system complexity here is loosely defined as an increase in the number of interacting, self-organizing components within the system, often operating over a broadening range of spatial and temporal scales. In the context of global environmental change, we are practically forced to embrace the complexity paradigm because the problems range across multiple disciplines, notably including the biophysical sciences, social sciences, and, indeed, philosophy. This approach is increasingly referred to as “transdisciplinary.” A question we must ask is whether humanity is capable of extending the evolution of complexity to a new level—that of a sustainable high-technology planetary civilization.

In the parlance of postmodernism, there is a “grand narrative” covering the origin and evolution of Western civilization. This model features the human conquest of Nature and the steady progress of technology and social organization toward our current glorified state. This grand narrative is, of course, now questioned for many reasons, not least among them the nascent threat that humanity poses to its own life support system.

TABLE 1.1 Phases of the Anthropocene Narrative

NAME		DISTINGUISHING FEATURES
Evolution of a Gaian Biosphere (prehuman geological period)		Establishment of the global biogeochemical cycles that contribute to regulation of Earth’s climate and the chemistry of its atmosphere and ocean
Great Separation (early human history)		Biological evolution of language-using Homo sapiens, control of fire, invention of simple tools, and domestication of plants and animals
Building the Technosphere (world history period)		Urbanization, construction of global transportation and communications networks, the Industrial Revolution
Great Acceleration (post–World War II)		Exponential increases in human population and use of natural resources, rapid advances in science and technology, and evidence of human impacts on the global environment
Great Transition (current)		Bending of the curves for global population size and natural resource use, emergence of a global awareness of limits on conversion of natural capital to technosphere capital
Equilibration (future)		Humanity learns to self-regulate and to manage the Earth system

We might thus pose a new master narrative for humanity, one more attuned to the planetary scale. Indeed, this new narrative—the Anthropocene narrative—provides a framework for this book (table 1.1). It begins with evolution of a self-organizing Gaian (if you will) biosphere. The next stage is the evolution of humans and their separation from Nature (i.e., the Great Separation). Through the acquisition of language, the taming of fire, the invention of simple tools, and the development of agriculture, we came to view Nature in mostly instrumental terms, and set ourselves apart from it. A subsequent Building of the Technosphere phase relied on gradual advances in technology and social organization, and produced global communications and transportation networks. The post–World War II Great Acceleration follows—an exponential phase of technosphere growth and influence on the Earth system. Up next may be the Great Transition; economist Kenneth Boulding (1964) and physicist Paul Raskin (2016) have employed this phrase to evoke a qualitative change in civilization in which rates of growth for global population and fossil fuel consumption would be stabilized and then reversed. Key to this concept is reconnection of the human enterprise with the biosphere. Lastly, we might imagine an Equilibration phase in which humanity learns to manage the biosphere and the global biogeochemical cycles—in effect, building a sustainable high-technology global civilization. As we shall see, there are no guarantees about fulfilling that aspiration (Ehrlich and Ehrlich 2012).

EARTH SYSTEM SCIENCE

The first scientific hint that the human technological enterprise had begun to have global-scale impacts on the environment came from observations of atmospheric CO2 concentration in the late 1950s. During a postdoctoral fellowship at the Scripps Institute in San Diego, Charles David Keeling developed an instrument capable of reliably measuring the CO2 molecule in a gas at very low concentrations. He then set out to study the spatial and temporal patterns in the atmospheric CO2 concentration (technically, the CO2 mixing ratio). At that time, there no way of estimating global fossil fuel emission of CO2 or total CO2 release from deforestation, so no one really knew to what degree they were influencing the CO2 concentration in the atmosphere.

Keeling’s first step was to set up a monitoring station high on the flanks of the Mauna Loa volcano on the Big Island of Hawaii. He reasoned that by situating his instrument in Hawaii, in the middle of the Pacific Ocean, local vegetation and fossil fuel sources would have a limited effect on the measurements. He was hoping to monitor the whole atmosphere from one sampling station. After taking daily measurements for a few years, Keeling made two major discoveries (figure 1.1). The first involved the recognition of a seasonal oscillation in the CO2 concentration in the northern hemisphere, resulting in a decrease of about 10 ppm (parts per million; i.e., molecules of CO2 per million molecules of dry air) in summer. That decrease turns out to be driven by a natural excess of carbon uptake through terrestrial photosynthesis (a carbon “sink”) over plant residue decomposition (a carbon “source”). The biosphere could thus be said to breathe.

Keeling’s second discovery was that the concentration of CO2 in the atmosphere was rising. He didn’t, by any means, know much about the various terms in the atmospheric carbon “budget,” but it seemed likely to Keeling that the rise was caused by fossil fuel combustion. In 1957, geophysicist Roger Revelle famously characterized the rise in CO2 as a global-scale experiment being conducted by humanity (Revelle and Suess, 1957). Scientists knew there might be impacts on the biosphere and climate system, but there was little certainty about how high CO2 might go, or the magnitude of the associated climate change. As we shall see in subsequent chapters, the sign of a human footprint on the atmosphere in 1955 was indicative of pervasive human impacts on the geosphere, hydrosphere, and biosphere.

FIGURE 1.1

Historical record of the observations of CO2 concentration at Mauna Loa. Adapted from NOAA (https://www.esrl.noaa.gov/gmd/ccgg/trends/full.html).

We should step aside from the science of global change here to register what a truly profound discovery it was that humanity was altering the global atmosphere. Before the scientific era, the Western monotheistic religions had codified a creation myth that elevated humanity above the rest of creation. As retold in this myth, we had been given dominion over the Earth by an omnipotent deity and it was now our garden (i.e., the Great Separation). The Copernican revolution in the sixteenth century dealt a major blow to this belief system by establishing that Earth was not the center of the universe, but instead orbited the sun. This concept was contrary to Church dogma and significantly undermined Church authority. More than 200 years later, Darwin deduced that human origins were the same as any other animal’s—i.e., we were the product of biological evolution. Through the lens of this theory, our facility with language was now viewed as just another adaptation, like sharp teeth for eating meat. This new perspective was rightfully humbling.

Keeling’s discovery changed all that. It effectively placed humanity back into the mode of having dominion over the Earth. Whereas in earlier centuries that dominion was believed to have been bestowed on us by a creator God (in the Western tradition), geophysical observations by Keeling and others have made evident that we recently bestowed it on ourselves by the magnitude of our impacts on the planet (i.e., the Great Acceleration).

Today most people in both developed and developing countries have probably heard the idea that changes to the atmosphere are promoting global climate change. The big bang on this issue, in the United States, at least, seems to have occurred in the summer of 1988. The weather that year was unusually warm, and congressional hearings on climate change took place in midsummer in Washington, D.C., with temperatures near 100 degrees Fahrenheit outside the hearing room. Amid considerable debate and drama, there was a fever pitch of media arousal around the statement by climatologist James Hansen that the recent warming of the global climate could be attributed with high certainty to effects of rising greenhouse gas concentrations. On the cover of Time magazine, Planet Earth was depicted with a thermometer sticking out of it, and the temperature rising into the red zone. Congress was not ready to start limiting carbon emissions, but legislators took heed of scientists’ warnings and made big commitments to more research, notably by funding an array of NASA’s Earth Observing System satellites.

Earth system science subsequently emerged as a new scientific discipline that aimed to “capture all processes in nature and human societies as one interlinked system” (Lovbrand, Stripple, and Wiman, 2009, p. 12) at the global scale (Schellnhuber, 1999). Over the past 25 years, a burst of Earth system science research performed all over the planet has led in several directions, some of which point toward an ominous end (Clark et al., 2004). One of the core specialized fields in Earth system science is paleoclimate research. Through examination of the paleorecord (e.g., as found in ice cores and marine sediment cores), we have gained a clearer understanding of the role of greenhouse gases in Earth’s climate over geological time scales (see chapter 2). There is no question that these gases have been dominant players in the dramatic swings in climate that have occurred in Earth’s history. The associated environmental changes have had major consequences for life on Earth and are often drivers of extinction events. Examination of the paleorecord has also made it clear that the biosphere is an active influence on the atmospheric composition (see chapter 3). A key question for the purposes of our collective future is the degree to which the biosphere dampens or amplifies directional changes in the climate system. Specifically, could the biosphere compensate for human influences on the climate system? Or will it amplify the human influences and perhaps even precipitate a major extinction event?

A second focus in Earth system science has been on the current state of the climate and the global biogeochemical cycles (see chapters 4 and 5). Humanity was characterized by Vernadsky as a geological force primarily because it had begun to widely alter the cycles of carbon, nitrogen, and water. Scientists now use an array of global monitoring systems, ranging from networks of stream gauges to satellite-borne sensors of vegetation phenology, to track the human footprint on the global environment. The “green marble” is an image of Earth with plant productivity mapped by satellite remote sensing.

A third focal research area in Earth system science has been development of Earth system models that simulate the global biogeochemical cycles and the global climate (see chapter 6). Business-as-usual scenarios of CO2 emissions and accumulation in the atmosphere point toward levels on the order of 500–1,000 ppm by 2100, up from approximately 280 ppm at the beginning of the Industrial Revolution. Earth system models are tools for evaluating the climate consequences associated with those concentrations. Despite variation among the models in their sensitivity to greenhouse gas increase, there is now wide agreement among climate modelers that anticipated increases in CO2 and other greenhouse gases (driven primarily by fossil fuel emissions) will profoundly alter global climate, sea level, and vegetation distribution. As more information and theory are introduced into development of these models, the evidence is increasing for a variety of positive (amplifying) feedback responses to the initial human-induced greenhouse gas warming. The outcomes extend from mostly manageable environmental changes, if emissions are rapidly reduced, to doomsday scenarios, if business-as-usual emissions continue and strong carbon cycle feedbacks are engaged. Remarkably, it appears that humans have managed to divert upward the slow global cooling trend evident in the paleorecord that was leading toward the next ice age (figure 1.2).

The implications of improved understanding of Earth’s climate system and the human impact on it have inspired researchers to apply Earth system models in evaluating the prospects for climate change mitigation. This field addresses both what can be done to reduce net greenhouse gas emissions, e.g., create carbon sinks by afforestation (the planting of trees in an area where they had not grown before), and what might be done to minimize climate change impacts once the greenhouse gas concentrations have already risen. Thus far, geoengineering solutions such as shading Earth by mechanical or chemical means are perceived as too impractical or polluting. The danger of unintended consequences lurks behind many of the technological fixes potentially applied to mitigate human impacts on the environment, which highlights the importance of a whole Earth modeling framework to evaluate them.

A last critical element of Earth system science is the study of the human dimension of global environmental change (explored in chapters 7–10). Here the concern is how people perceive and experience global environmental change, how they respond, and how we might organize ourselves for possible mitigation and adaptation. The social sciences come to the forefront as we seek to understand how people interact economically and politically at various levels of organization (Palsson et al., 2013). Ecological modernization theory (see chapter 7) suggests that global environmental change issues are addressable if ecological considerations rise to the level of economic and security considerations in all societal deliberations. The ecological sciences have developed a subdiscipline (anthroecology), which seeks to “to investigate and understand the ultimate causes, not just the consequences, of human transformation of the biosphere” (Ellis, 2015, p. 321). That project requires close attention to the history and prospects for linked socioecological systems (Angelstam et al., 2013).

FIGURE 1.2

Humans have likely diverted the global climate trajectory from its path toward the next ice age. The background trend, driven by slowly changing solar forcings, was pushing Earth toward a return to glacial period temperatures. Anthropogenic greenhouse gases are now propelling the global mean temperature above the range of most previous interglacial periods, and toward the “Hothouse Earth” warmth of the mid-Cenozoic era over 30 million years ago. Adapted from Ruddiman (2005).

German sociologist Ulrich Beck hypothesized that as global-scale threats such as nuclear holocaust and stratospheric ozone depletion become more prominent, universal exposure to the risks they represent will induce a new force for social cohesion (Beck, 1992). The risks at the global scale are so great that both rich and poor individuals, as well as nations, share vulnerability. Global environmental change may thus push humanity toward the kind of collective identity and global-scale institutions needed to manage ourselves and the global environment (see chapters 8 and 9). Certainly, it will require coupling of humans and natural resources (socioecological systems) at multiple levels of organization to arrive at something sustainable (see chapter 10).

Practitioners of Earth system science are, for the most part, motivated by a deep curiosity about the structure and function of the Earth system. Research scientists are generally supported by governmental funding, and the traditional social contract was that their research should produce an increasingly deeper understanding of how the world works. Earth system science is now in a position in which society is asking for more. Besides characterizing the impacts of humans on the Earth systems, practitioners of Earth system science must “work to provide the underpinnings for workable solutions at multiple scales of governance” (DeFries et al., 2012, p. 603). The policy community is in need of “actionable, sustainability-relevant knowledge” (Lubchenco, Barner, Cerny-Chipman, and Reimer, 2015). That thinking is increasingly reflected in the budget priorities of the major science funding agencies.

CONCLUSIONS

Our project of thinking globally is both an interdisciplinary and a transdisciplinary endeavor. The interdisciplinary part draws on fields in the geosciences such as paleoecology and climatology. These disciplines share a common foundation in physics, chemistry, and biology. The transdisciplinary part combines information and ways of knowing from the biophysical realm with knowledge from social science disciplines (especially sociology, economics, and political science). Here, the attribution of causality is more complicated and the capacity to model fundamental processes is more limited. Yet only by understanding both the biophysical and the human dimensions of global environmental change can we hope to design and operate a sustainable, high-technology, global civilization.