said that his research on ozone had convinced him that the balance of forces on Earth had changed dramatically. It was now “utterly clear,” he said, “that human activities had grown so much that they could compete and interfere with natural processes.”3 His interjection at the IGBP meeting in 2000 crystallized that insight in a single word, Anthropocene. “I just made up the word on the spur of the moment,” he says. “Everyone was shocked. But it seems to have stuck.”4
Crutzen was something of a scientific superstar: according to the Institute for Scientific Information, between 1991 and 2001 he was the world’s most-cited author in the geosciences.5 There is no question that his high profile drew attention to his articles on the Anthropocene, and eventually helped win broad acceptance for the idea.
Steffen, Crutzen, and environmental historian John McNeill subsequently explained the need for a new word this way:
The term Anthropocene … suggests that the Earth has now left its natural geological epoch, the present interglacial state called the Holocene. Human activities have become so pervasive and profound that they rival the great forces of Nature and are pushing the Earth into planetary terra incognita. The Earth is rapidly moving into a less biologically diverse, less forested, much warmer, and probably wetter and stormier state.6
“A no-analog state,” “planetary terra incognita”—these phrases are not used lightly. Earth has entered a new epoch, one that is likely to continue changing in unpredictable and dangerous ways. That’s not an exaggeration or a guess: it’s the central conclusion of one of the largest scientific projects ever undertaken, one that requires us to think about our planet in an entirely new way.
Earth as an Integrated System
Though it has gone unnoticed by most people and unmentioned in mainstream media, scientific understanding of our planet has radically changed in the past three decades. Scientists have long studied various aspects of Earth, using the methods of geology, biology, ecology, physics, and other disciplines. Now many are studying Earth as an integrated planetary system—and discovering that human activity is rapidly changing that system in fundamental ways:
Crucial to the emergence of this perspective has been the dawning awareness of two fundamental aspects of the nature of the planet. The first is that the Earth itself is a single system, within which the biosphere is an active, essential component. In terms of a sporting analogy, life is a player, not a spectator. Second, human activities are now so pervasive and profound in their consequences that they affect the Earth at a global scale in complex, interactive, and accelerating ways; humans now have the capacity to alter the Earth System in ways that threaten the very processes and components, both biotic and abiotic, upon which humans depend.7
Studying Earth as a system became possible and necessary in the 1980s. It became possible when new scientific instruments became available—in particular, satellites designed to gather data about the state of the entire Earth and computer systems capable of collecting, transmitting, and analyzing vast quantities of scientific data. It became necessary when scientists and others realized that nuclear weapons, ozone-destroying chemicals, and greenhouse gases could radically remake the world: human activity was causing not just change but global change, with potentially disastrous consequences.
Following discussion of global change at meetings of the International Council of Scientific Unions (ICSU) in Warsaw in 1983 and Ottawa in 1985, a series of international symposia and reports recommended creation of a coordinated international research program on global change. As a member of the American Geographical Union wrote, the need went beyond scientific curiosity:
It was noted that stresses on the support systems that sustain life were building up at an ever-increasing pace as the result of increases in world population, industrial activity, waste products, pollution, and resource exploitation, as well as because of long-term trends in regional climatic change. To preserve or expand the life-support systems during the 21st century, governments of all nations would have to design long-term plans that, while addressing their own specific national goals, would have to be based on basic scientific knowledge of the global terrestrial environment and on anticipated natural and anthropogenic change. The required detailed and quantitative scientific knowledge simply does not yet exist.8
In 1986, the ICSU initiated the International Geosphere-Biosphere Program, “the largest, most complex, and most ambitious program of international scientific cooperation ever to be organized.”9 The IGBP’s objective was to “describe and understand the interactive physical, chemical, and biological processes that regulate the total Earth system, the unique environment it provides for life, the changes that are occurring in that system, and the manner in which these changes are influenced by human actions.”10
A secretariat was established in Stockholm in 1988, and some 500 scientists worldwide began planning initial projects. By the early 1990s, the IGBP was coordinating the work of thousands of scientists studying the Earth System, a term that has been well defined by Frank Oldfield and Will Steffen:
In the context of global change, the Earth System has come to mean the suite of interacting physical, chemical, and biological global-scale cycles (often called biogeochemical cycles) and energy fluxes which provide the conditions necessary for life on the planet. More specifically, this definition of the Earth System has the following features:
• It deals with a materially closed system that has a primary external energy source, the sun.
• The major dynamic components of the Earth System are a suite of interlinked physical, chemical, and biological processes that cycle (transport and transform) materials and energy in complex, dynamic ways within the System. The forcings and feedbacks within the System are at least as important to the functioning of the System as are the external drivers.
• Biological/ecological processes are an integral part of the functioning of the Earth System, and not just the recipients of changes in the dynamics of a physico-chemical system. Living organisms are active participants, not simply passive respondents.
• Human beings, their societies and their activities are an integral component of the Earth System, and are not an outside force perturbing an otherwise natural system. There are many modes of natural variability and instabilities within the System as well as anthropogenically driven changes. By definition, both types of variability are part of the dynamics of the Earth System. They are often impossible to separate completely and they interact in complex and sometimes mutually reinforcing ways.11
As Hans Schellnhuber of the Potsdam Institute for Climate Impact Research wrote, this was a revolutionary shift in the scientific view of Earth, comparable to the sixteenth-century discovery by Copernicus that Earth orbits the Sun.
Optical magnification instruments once brought about the Copernican revolution that put the Earth in its correct astro-physical context. Sophisticated information-compression techniques including simulation modeling are now ushering in a second “Copernican” revolution….
This new revolution will be in a way a reversal of the first: it will enable us to look back on our planet to perceive one single, complex, dissipative, dynamic entity, far from thermodynamic equilibrium—the “Earth system.”12
Global Change and the Earth System
An overarching goal of the IGBP’s work was to develop “a substantive science of integration, putting the pieces together in innovative and incisive ways toward the goal of understanding the dynamics of the planetary life support system as a whole.” By early in the twenty-first century, they were confident that “an integrative Earth System science is already beginning to unfold.”13
