Anthropocene Science: There May Be Trouble Ahead

Now and then scientists act in concert to speak truth to power. Back in the 1970s, for example, they invented and used the idea of a “nuclear winter,” which became a semantic weapon that helped de-escalate the Cold War arms race between the communist countries and members of NATO. Today the daily war against Earth is a prime focus: teams of scientists have coined new terms to sound the alarm about humanity’s various misuses of the nonhuman world. Chief among them is the Anthropocene. It describes human impacts on Earth of such scope, scale, and magnitude as to initiate a new phase of the planet’s 4.5-billion-year history. “Anthropo” means people, “cene” an extended period: “the age of humans,” as a rough translation. Originating in environmental science at the turn of the millennium, the Anthropocene may soon graduate from an academic buzzword to a keyword—that is, one of those terms that animates inquiry within and between a plethora of disciplines over a long period of time (in the ways that “globalization” and “genetic modification” have done since the mid-1990s).

The term has already escaped its scientific moorings and is enlivening discussions of environment across the social sciences and humanities. But the Anthropocene barely features in public discourse and has only made fleeting appearances in the news media and in high level political arenas. Compared to anthropogenic climate change, it remains a strange sounding academic label (despite being nearly twenty years old). For those excited by its potential to alter human self-understanding and behavior, the Anthropocene concept needs rapid and widespread promulgation beyond academic conferences, journals, books, and websites. However, the chances of that happening are, at present, greatly diminished by the very scientists responsible for assessing its suitability as a description of changes to the hydrosphere, cryosphere, biosphere, lithosphere, and atmosphere. Before I explain this paradoxical claim, let’s consider the context.

In most countries, science is still regarded as the most authoritative guide to matters of fact. Since 2007 to 2008, a growing number of scientists in several disciplines have devoted their energies to assembling and assessing evidence to determine if the current Holocene epoch is ending (in geology, an epoch is a short period nested within much longer term periods of change). Recent months have been significant in this regard. First, a string of high-profile papers about the Anthropocene have appeared in the prestigious journals Nature and Science. They assemble evidence to suggest that humans are now, in effect, part of the Earth system—not merely subject to large natural forces like weather systems.

Second, alongside this a number of geologists have been collaborating with environmental scientists to determine if the Anthropocene can be proven to be a new epoch. The Anthropocene Working Group (AWG), established in 2009, seems poised to make formal recommendation to the International Commission on Stratigraphy (ICS) via the Subcommission on Quaternary Stratigraphy. The ICS uses very exacting criteria to determine whether significant biogeophysical changes have occurred in Earth’s long history, visible as stratigraphic boundaries between layers of rock. By making the Anthropocene a matter of science in the first instance, all these scientists have ensured that answers to questions about biophysical change must precede normative questions concerning how humans ought to respond to such change. This is hardly unusual, of course, and follows a linear “is-ought” pattern that has characterized climate policy for thirty years. However, given the monumental implications of the Anthropocene hypothesis, the scientists involved should steel themselves for trouble ahead. The attacks on climate experts, especially in the United States, are a precedent that could very likely be repeated in several countries if Anthropocene scientists declare that the Holocene is a thing of the past. That would be nothing to worry about if the scientific consensus were as wide as it is about climate change, and if a global, authoritative body like the Intergovernmental Panel on Climate Change (IPCC) were advancing the Anthropocene concept. But things are far more complicated. Therein lies the vulnerability of scientists who proclaim that humans are now a “geological force” taking the planet into terra incognita. A plethora of problems lies in two areas.

First, the ICS is accustomed to assessing evidence about changes to Earth in the distant past. But the AWG is investigating very recent changes to Earth’s surface caused by human activity—geologically speaking we’re talking about the blink of an eye. Questions therefore arise about the suitability of using stratigraphic criteria to demonstrate the unprecedented impact of humans on our planet. If the AWG does recommend formal recognition of the Anthropocene, it will almost certainly walk into a barrage of criticism. Scientifically, some geologists have seriously questioned the group’s remit for the reason just mentioned. Chief among them is Stanley Finney, who happens to be the current chair of the ICS. With Lucy Edwards, he has recently published a searing critique of the AWG’s work, not because its members lack professional integrity but because it is not, in their view, work relevant to geology. In this light, seeking the imprimatur of the ICS seems to Finney and Edwards to be a political strategy used by leading group members like Jan Zalasiewicz to secure authority for scientific claims about an errant humanity.

On a related note, a senior geologist resigned from the AWG in 2014, while an equally senior scientist (Cambridge University’s Phil Gibbard) has publicly expressed doubts while remaining a group member. As if this were not enough, because the group’s work is unusual in stratigraphic terms, not all of its members are geologists. One is the American journalist Andrew Revkin. What’s more, the AWG does not possess the international spread of members that the IPCC learned early in its life is very important if globally relevant scientific assessment is to be taken seriously. Indeed, it is not entirely clear to outsiders how the current membership was selected out of a larger pool of potential members. It is also arguably problematic that leading members are acting as both judge and jury. Zalasiewicz and a core group within the AWG have been treading an uneasy line between doing research about the Anthropocene proposition and assessing the stratigraphic significance of their own and others’ research. At times, they have been advocates for the Anthropocene concept, even as its geological validity remains undetermined.

In light of this, anyone minded to inquire into the credibility of an AWG recommendation in favor of the Anthropocene would soon entertain serious doubts about process and outcome. Those threatened by the radical economic and ethical implications of the Anthropocene proposition would have a field day. Without looking too hard, they could claim that the group is an impostor, in stratigraphic terms, and has been staffed and run in a problematic way that comprises the quality of its work. Even if none of this applied, if the ICS does not uphold an AWG recommendation made this year, then it will be another decade until a further recommendation can be submitted to the commission. Such an outcome could leave people with the false message that the human impact on Earth (along with associated social injustice) is not nearly as bad as some make it out to be.

This brings us to a second arena in which Anthropocene science is being undertaken. The concept first attracted interest not among geologists but rather a set of environmental scientists associated with the International Geosphere-Biosphere Programme (IGBP), founded in 1987. The program, recently closed, fostered research into the Earth system as a whole. It enabled synthetic descriptive, explanatory, and predictive investigations of changes to, and connections between, all the major components of the planet’s outer layer. In this context, the Anthropocene has been repeatedly used by leading IGBP players—notably Nobel Prize winner Paul Crutzen and American-Australian climate scientist Will Steffen —to designate the “game changing” effects of humanity on the Earth system. This is not a stratigraphic issue. It is a question of demonstrating alterations to the hydrosphere, cryosphere, biosphere, lithosphere, and atmosphere that manifestly depart from Holocene norms. In the past few years, Crutzen, Steffen, and co-investigators have published papers in world-leading scientific journals whose message is clear: humanity is taking itself into a “no analogue” situation in a biogeophysical sense. One of their core descriptors is the “Great Acceleration” occurring post-1950 as Western lifestyles have been globalized. The implication is made very clear: humans, especially in the wealthiest parts of the world, need to entirely rethink their way of life before we cross what are called “planetary boundaries.”

This research has the virtue of not needing to be assessed by exacting stratigraphic criteria. But it faces other problems should anyone seek to question its validity in the public arena. First, though the IBGP was geographically inclusive, those publishing synthesis papers about the Anthropocene may appear as a self-selecting group of Anglo-European “concerned scientists” with “environmentalist” sympathies. What is more, their findings have not been independently assessed in the way the IPCC assesses peer-reviewed research into climate change. In addition, questions arise about how one would robustly assess these findings in the first place. The Earth system is exceedingly complex, and even the best computer models can only approximate its dynamics; potential tipping points and thresholds add extra layers of uncertainty. For some this implies the need for precaution since things could soon be much worse than the scientists believe, but for others it could easily mean that we need to gather more evidence before we accept the “hasty” conclusions arrived at by Crutzen, Steffen, and their collaborators. When one considers the formalities involved in getting the newish Intergovernmental Platform on Biodiversity and Ecosystem Services established as a legitimate scientific assessment body, it’s clear that both the AWG and the scientists emerging from the IGBP/Earth system context will have their work cut out to avoid robust challenges to their high-stakes claims about our planetary condition. Indeed, a Platform precursor—the 1995 Global Biodiversity Assessment—struggled to achieve extra-scientific legitimacy precisely because it did not attend closely to how its work would be regarded by governments, publics, and others.

A debate that bridges the two arenas of Anthropocene science concerns the date of the new epoch’s onset. There are some fairly sharp disagreements involving geologists like Zalasiewicz and people in the wider environmental sciences, like American Bill Ruddiman. It would be convenient if these disputes could be settled with reference to “best evidence”—the strongest working hypothesis would then win out. But, again, nothing is straightforward with Anthropocene science. First, what is the “baseline” against which “significant” biogeophysical change caused by humans is being measured? And how is “significant” to be defined? Neither question has a purely objective answer since change is partly defined relative to what we humans, in our various societies, take to be stable, normal, desirable, and consistent. This is why widely separate dates are being proposed (1400, 1500, 1780, and 1950). Here is yet more room for people outside science to ask awkward questions about the validity of any scientific claims about the end of the Holocene, with all this implies.

It often takes a long time for power to acknowledge the conditional truths ventured by science. The glacial progress of global climate policy, even after five IPCC assessment reports, testifies to that. The scientists who have proposed, and are now assessing, the Anthropocene hypothesis deserve our respect. But they may want to pause for thought as they proceed. As I have intimated, there are potential issues about how the science is conducted, what its findings are, and what those findings are said to signify. In each case, those outside science can find reasons to push back if allowed to. Skepticism in and about science is healthy, and the sign of a functioning democracy. But not all skepticism is warranted, and debates and decisions can only occur once some agreement on salient “matters of fact” have been achieved.

In this light, the AWG would be advised to wait before making any positive recommendation—maybe several more years. Meanwhile, IGBP-inspired groups might now spend more time preparing a defense of their methods and findings lest noisy or well-funded skeptics come knocking at their doors. If not, I fear that the more visible and vocal Anthropocene scientists become, the more likely they are to attract the attention of critics who may find it all too easy to call the procedures and conclusions of the science into question. This is likely to occur even in the absence of well-funded Anthropocene skeptics determined to poke holes in the science for nonscientific reasons. Even in a global environmental emergency, science has to be sufficiently slow and methodological to persuade outsiders that its messages are robust. This is especially true when those messages imply a wholesale change to our economies, cultural norms, and ethical compasses. Though some claim that in the face of environmental danger we need action, not more science, it’s essential that action be founded on science that commands widespread respect across ideological lines. To achieve global credibility, it could be that Anthropocene science needs to press the reset button. Removing it from stratigraphic debates might be a wise first move, while channeling science through a procedurally rigorous assessment body might be an equally wise second one. Otherwise, it risks being seen as a rather ad hoc pursuit that’s eliding science and political claims making to the detriment of both. That would make it far too fragile to bear the normative weight of its own alarming conclusions.

I realize that this argument may seem surprisingly traditional—even naïve—coming from a “critical social scientist.” After all, the sort of people I identify with professionally have been criticizing the “Anthropocene narrative” for being too science-led and a form of politics by other means (see, for instance, Bonneuil and Fressoz’s new book The Shock of the Anthropocene [Verso]). “People like us” are normally skeptical of the ideas of scientific objectivity and a fact-value dichotomy. But, just to be clear: I am endorsing neither. Instead, I’m arguing that the world in which we live still believes in both, by and large. In this world, critical social scientists are a distinct minority. This means that what is perceived to be “sound science” is still imperative if we’re to ask important extra-scientific questions about things that matter to us, to other people and to nonhumans.

Indeed, much of the growing social science and humanities discourse about the Anthropocene takes it as read that at some level the science is to be believed. While we question the narrative, we trust the underpinning science in its fundamentals. Australian philosopher Clive Hamilton’s writings are a case in point—he is adamant that scientific claims about the changing Earth system are to be taken seriously but extremely critical of any science-led framing of “problems” and “solutions.” Faith in science will need to apply more widely if publics, governments, and businesses are to be convinced that we truly do now have the whole world in our hands. Skepticism is a necessary ingredient to good science and any thriving democracy. But when science contains uncertainties and focuses on things that might ultimately be unknowable, the wrong sort of skepticism can weaken its messages and debase democracy in the process. Critical social scientists and humanists now find allies in the world of international geoscience. But before we criticize the narrative while accepting the fundamental science, we might consider the downsides of announcing the Anthropocene’s arrival when the science is still open to fundamental challenge by those who dislike the normative implications.

Noel Castree is a Professor of Geography at the University of Wollongong, Australia, and an Honorary Professorial Research Fellow at the University of Manchester, England. His most recent writings, focused on global change research, can be found in the journals Antipode, Dialogues in Human Geography, Environmental Humanities, Geographical Research, and the Transactions of the Institute of British Geographers.