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Introducing the Anthropocene

A brand-new name for the geologic present

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Big-name scientists often add to the language. Usually they do this by becoming a geologic eponym—having something named after them. In Earth science it's most often the name of a fossil species, a mineral, or a geologic concept. But Paul Crutzen, a Nobel Prize winner for his work on the ozone layer, has set out to give the future a new name.

The Anthropocene Epoch: In Favor

In a stirring 2000 paper, Crutzen pointed to the many ways that today's Earth is no longer "natural" thanks to the effects of human civilization. Global warming is only the latest and best-known example. Truly, he says, humans have become a geologic agent comparable to erosion and eruptions, and accordingly "it seems to us more than appropriate to emphasize the central role of mankind in geology and ecology by proposing to use the term 'anthropocene' for the current geological epoch." He repeated his proposal to a much larger audience in a January 2002 Nature article.

This is a well-worded and precise proposal. The geologic time scale extends from the Earth's formation, in the Hadean Eon, to the current Holocene Epoch, which began with the latest interglacial period about 11,500 years ago. So Crutzen wants the Holocene to end and the Anthropocene to begin, a new time period of the same rank as the Holocene. We would still be in the Quaternary Period of the Cenozoic Era in the Phanerozoic Eon.

You notice that I capitalize all those names whereas Crutzen did not. That's because his name is only a proposal, which would have to be ratified by the world's major scientific organizations first.

The Anthropocene Epoch: Opposed

If I were them, I might reject his proposal because it doesn't follow the rules. But something very close to it would be a good thing.

The smallest, most basic unit of geologic time is the age, and an epoch is a series of ages. The familiar time units Holocene, Pleistocene, Pliocene, Miocene and so on going back in time are epochs that consist of ages. The Miocene Epoch, for instance, consists of the Aquitanian, Burdigalian, Langhian, Serravalian, Tortonian and Messinian ages. (Nobody has seen fit to name an age for the Holocene.)

Here's my point: Time units traditionally have been precisely defined by fossil evidence—the appearance or extinction of particular species in particular rocks. Lately, especially for young time units, the boundaries of units come from more objective physics-based things like orbital cycles, which leave their signs in climatic cycles that affect the detailed chemistry of sediments. But the biggest exception is the definition of the Holocene, which was supposed to be 10,000 radiocarbon years old until the radiocarbon yardstick turned out to be crooked. The absolute calendar date is something close to 11,800 years ago.

Crutzen's would-be Anthropocene Epoch isn't based on fossils or physics. He would start it in the late 1700s, at the start of the Industrial Revolution. That's a good choice to mark the beginning of one thing: the carbon-dioxide pulse that underlies the current global warming. But you could only determine that point with exact dating methods, which include things like historical records, which aren't really geological, or tree rings, which aren't easy to find for most of the planet.

Proposal: The Anthropocene Age

Crutzen mentions that others have proposed starting the Anthropocene much earlier. That's what I would do too, because the widespread human influence on the Earth began long before the 1700s. The ancient Mediterranean and Near Eastern civilizations, for instance, deforested their region and turned it dry thousands of years ago. The inhabitants of Australia and the Americas, even earlier, used (or misused) fire to manage their local ecosystems, and they slaughtered many of the larger animal species as well.

To me, the best way to respond to Crutzen's proposal is to add the Anthropocene Age under the Holocene Epoch. That is already established by traditional geologic methods, so nothing would change in the field or in the lab.

And this action would acknowledge the real point Crutzen is making: "An exciting, but also difficult and daunting task lies ahead of the global research and engineering community: to guide mankind towards global, sustainable, environmental management." I would use the punchier formulation of Stewart Brand, the American visionary: "We are as gods and might as well get good at it." Who knows? Once we have achieved global, sustainable environmental management we can start a new, post-Anthropocene age named the Planeteering.

The Experts' Proposal for the Anthropocene

A group of 21 researchers from the Geological Society of London has taken a closer look than I did at Crutzen's proposal. The GSL group's conclusion, published in the February 2008 GSA Today, is that the world really did change around 1800. What we have wrought—universal damming of rivers, a quantum step upward in erosion, soaring carbon dioxide levels, widespread extinction and ecosystem disturbance, and an ongoing pulse in ocean acidification—has pushed Earth in a fundamentally new direction.

Thus they argue that the Holocene Epoch is effectively over: "it [is] likely that we have entered a stratigraphic interval without close parallel in any previous Quaternary interglacial." They even consider whether the very ice-age era, the Quaternary Period, is over, but conclude that it's a few millennia too soon to say.

But what about a geologic marker? The worldwide radioactive surge from the 20th-century atomic bomb tests might do. The GSL group argues that if a geologic marker is needed for the base of the Anthropocene, the global sulfate pulse and tree-ring disturbance from the Tambora eruption of 1815 is also great and would suffice.

First published 4 August 2002; last updated 18 February 2011

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