A Brave New Epoch?
Once again, scientists propose that planet Earth has been so altered by human activity that we are entering a new geological time period—the Anthropocene. A viewpoint article by some stratigraphic heavy hitters, just published in the journal Environmental Science & Technology, has proclaimed a new age caused by anthropogenic global warming and man's savaging of the environment. According to these experts, the effects of human activity have become so pervasive that Earth has been transformed and the 11,000 year old Holocene epoch is now a “lost world.” Is this really the start of a brave new epoch, one of our own making?
The name Anthropocene is not new. Nobel Prize-winner Paul Crutzen, a co-author of the ES&T paper “The New World of the Anthropocene,” first proposed it a decade ago. It was not immediately accepted, but periodically the term seems to resurface. Crutzen's intention was to call attention to the “unprecedented” changes humans have inflicted on the planet in the +200 years since the industrial revolution began. Indeed, the term has been picked up by some practicing scientists to denote the current interval of time dominated by human activity. Here is how the authors described the quest for mankind's own epoch:
The notion that humankind has changed the world is not new. Over a century ago, terms such as the Anthropozoic, Psychozoic, and Noosphere were conceived to denote the idea of humans as a new global forcing agent. These ideas received short shrift in the geological community, seeming absurd when set aside the vastness (newly realized, also) of geological time. Moreover, the scarring of the landscape associated with industrialization may appear as transformation, but the vicissitudes of the geological past—meteorite strikes, extraordinary volcanic outbursts, colliding continents, and disappearing oceans—seemed of an epic scale beyond the largest factories and most populous cities.
Along with Paul Crutzen, who is Professor emeritus at the Max-Planck-Institute for Chemistry and was awarded a Nobel Prize in Chemistry in 1995 for his work on atmospheric ozone, the other authors are prominent members of the UK geological community. Jan Zalaziewicz is Vice-Chair of the International Subcommission on Stratigraphic Classification. Mark Williams leads the palaeoclimate team of the British Geological Survey. Both Zalasiewicz and Williams are members of the Stratigraphy Commission of the Geological Society of London. Will Steffen served as Director of the International Geosphere-Biosphere Programme, and is now Director of the ANU Climate Change Institute. Together, they argue that the time for declaring the beginning of the Anthropocene Epoch has come:
It helps that the term is vivid, as much for the public as for scientists. More importantly, it was coined at a time of dawning realization that human activity was indeed changing the Earth on a scale comparable with some of the major events of the ancient past. Some of these changes are now seen as permanent, even on a geological time-scale.
In 2008, the Stratigraphy Commission of the Geological Society of London decided, a body of independent geologists, voted in favor of considering the possible formalization of the term Anthropocene. This means that some day, Anthropocene “might eventually join the Cambrian, Jurassic, Pleistocene, and other such units on the Geological Time Scale.” But The Geological Time Scale is held dear by geologists (the authors' term), and amending it is no small matter. For now, the term Anthropocene remains an informal, imprecisely defined one.
Has mankind really made a large enough impact on Earth that our presence will be detectable in the far distant future? It is the stated purpose of the paper's authors to “outline the scale of human modification of the Earth on which the concept of the Anthropocene rests, describe the means by which geological time units are established, and discuss the particular problems and implications of discussing the Anthropocene as a formal geological time term.” So let us review the case for the Anthropocene.
Damn Dirty Apes
If the designation of an Anthropocene epoch is to be accepted, scientists will first have to identify and define a stratigraphic marker or boundary line, that is identifiable in Earth's rocky crust. “The key thing is thinking about how—thousands or hundreds of thousands of years in the future—geologists might come back and actually recognize in the sediment record the beginning of the Anthropocene,” explained paleoclimatologist Alan Haywood of the University of Leeds in the UK.
Named stratigraphic or geological time periods are identified by changes in the rock record. Within the rock of Earth's crust is recorded the comings and goings of all the lifeforms to inhabit this planet. Major changes in climate, often associated with mass extinction events, can also be captured by Earth's strata. Even events of cosmic origin, such as major asteroid impacts, can create a marker in stone. Zalaziewicz et al. put it like this:
In common language, epochs and eras are largely interchangeable. Not so in geology. An era is a very large-scale unit—the Mesozoic, the entire near-two-hundred-million-year time span of the dinosaurs, is made up of the Triassic, Jurassic, and Cretaceous periods, for instance. Epochs are much more modest, being subdivisions of geological periods. As well as duration, what is important is distinctiveness—and that reflects the scale of environmental change across the boundaries. The Mesozoic is bracketed by the two largest and most abrupt mass extinctions known (the Permian-Triassic, or P-T, boundary when over 90% of species were killed off, and the Cretaceous-Tertiary, or K-T, when the dinosaurs—and much else—disappeared), while epoch boundaries represent smaller-scale changes.
Have the actions of humans altered the course of Earth’s deep history? Would visitors to Earth a million years hence find any sign of our existence and what telltale markers would we leave behind? Here are some possibilities listed in the ES&T paper:
- Permanent traces of pollution—lead particles released when leaded gasoline is burned and other substances not normally found in high concentrations could mark strata lain down during mankind's time on Earth.
- A shift in carbon isotope ratio in ocean sediment—studies suggest that marine plankton now have a different carbon isotope signature than they did before humans began burning fossil fuels on a wide scale.
- The distinctive radioactive signature left by atom bomb tests—the use of atomic weapons at the end of WWII and subsequent atmospheric testing during the Cold War spread tiny but measurable amounts of artificial radionuclides.
Mankind's legacy may be nuclear in nature.
The term Anthropocene seems to be gaining momentum among greens and those promoting the theory of anthropogenic global warming. Past AAAS President James J. McCarthy, in his 2009 AAAS Annual Meeting keynote address, openly stated that mankind's impact on Earth is “sufficiently profound to declare that we have transitioned from the Holocene era of Earth history to the Anthropocene.” National Geographic reports: “An expert panel called the Anthropocene Working Group has already been formed within the International Union of Geological Sciences to consider the matter.” Adding that “any decision would then have to pass a series of review committees before going to the wider union for ratification.”
Many scientists say that declaring the beginning of a new epoch is premature. In fact, some say the Holocene isn't really an epoch—just another warm period within the Pleistocene, which began about 2.6 million years ago. “The period we're living in is the Ice Age, basically,” says geologist Philip Gibbard of the University of Cambridge in the UK. “There is no reason to think it has finished.” It may turn out that the current period is not the Anthropocene Epoch or the Holocene Epoch but simply a brief warm stretch during the Pleistocene Ice Age—one of many in the recent past. According to Gibbard, we can expect the alternating periods of warm and cold, interglacials and glacials, “to continue for at least a period of one million years.”
Ignoring the possibility that declaring a new epoch at all may be premature, when should the Anthropocene Epoch begin? The authors suggest that it be linked with the Industrial Revolution or with accelerated global environmental change following World War II—the latter being associated with the first detonations of atomic bombs. These could serve as a boundary marker for some future geologist. Strangely, it is not thought that the remains of human settlements would be distinct or pervasive enough to form a recognizable boundary. Our towering cities and thriving civilization will disappear with the passage of time but evidence of our wars, and possibly our pollution, will serve as mankind's marker. And that realization gets to the heart of this move to christen the new age of man the Anthropocene.
Humanity leaves a mark, but it will not last. Photo by Okinawa Soba.
The term serves to accentuate the many environmental impacts that the nearly seven billion people living on Earth are causing. “The concept of the Anthropocene might, therefore, become exploited, to a variety of ends,” Zalaziewicz et al. state. “It has the capacity to become the most politicized unit, by far, of the Geological Time Scale—and therefore to take formal geological classification into uncharted waters.” The true motivation behind the Anthropocene Epoch movement is not geological but political. Talking up the new Anthropocene Epoch is merely the latest excuse to bash industrial civilization, the technological world and humanity in general. For many eco-activists, we are the damn dirty apes.
I have a suggestion for Crutzen, Zalaziewicz, McCarthy and all the rest of the Anthropocene fan club—leave the identification of the current geological time period, its timing and naming, to future generations of geologists. The Anthropocene, if it is ever recognized, will simply be the ruins of human hubris writ in stone. Given that science is hard pressed to explain the vagaries of climate and the environment during the present, there is little hope of correctly identifying what permanent impact humans will have on Earth, if any.
Be safe, enjoy the interglacial and stay skeptical.
All species leave their mark on the planet. Photo by Robb Kendrick/Getty Images.
[ Thanks to Gabriel Rychert of ClimateRealists.com for pointing out the ES&T article to me. You were right, it is my sort of thing. ]