Core Concept: Are we in the "Anthropocene"?

In 2000, some two dozen top scientists gathered south of Mexico City to discuss the implications of their multidisciplinary Earth sciences research, and Paul Crutzen was getting frustrated. The work, part of the International Geosphere-Biosphere Program (IGBP) (www.igbp.net), had documented vast planetary changes caused by humans, such as soaring levels of carbon dioxide in the atmosphere. However, many of the scientists continued to refer to the present day as the Holocene Epoch, the geological period that began when the ice sheets started to retreat 11,700 years ago. The Earth is not in the Holocene anymore, asserted Crutzen, a Dutch atmospheric chemist and Nobel laureate. Instead, he said pausing to find the right word, we’re in the “Anthropocene,” a new epoch in which the Earth’s geology has been fundamentally changed by humans (hence the description “anthropo,” meaning human). It was a pivotal moment. “We all looked at each other and thought, wow, that really sums it up,” recalls Will Steffen, former head of the Australian National University Climate Change Institute and Executive Director of the IGBP in 2000. “The Anthropocene is an incredibly powerful unifying concept.” As Crutzen explained in a 2000 IGBP newsletter (1), the justification for the new term is to “emphasize the central role of mankind in geology and ecology.”And in fact, it has inspiredmany papers, such as a recent one in Science in January 2016 (2), which present detailed evidence for major geological and ecological changes caused by human activities. The notion of the Anthropocene has also has captured the public’s imagination, with cover stories in magazines like the Economist (3). But it’s also been hard to pin down. “People are using it with great abandon, but no one knows what it means,” says Colin Waters, principal mapping geologist at the British Geological Survey. “That devalues the concept and confuses the science as well.” And that’s why a small group of members of the Geological Society of London and other global experts created an Anthropocene Working Group (AWG) about seven years ago, to decide precisely what the word means. The working group will report to the Subcommission on Quaternary Stratigraphy in the International Commission on Stratigraphy (ICS) (www.stratigraphy.org), which is responsible for officially dividing the Quaternary— the last 2.6 million years—into distinct epochs and ages. After running on a shoestring and staying in touch remotely and informally for years, the now 37-member AWG held its first meeting in Berlin in 2014 and plans to submit a preliminary proposal to the ICS this August to declare the Anthropocene a new geological epoch. Such a determination would be a big deal. “Geologists do not tinker with the geologic stratigraphic time scale lightly,” says Georgetown University historian and AWG member, John McNeill. It’s also highly controversial. “Yes, humans are changing the Earth, and yes, you can call it the Anthropocene,” says ICS chair Stan Finney, a geologist at California State University, Long Beach. But adding it as a new chapter to the official geologic record “misrepresents what we do,” he says. “We are set up to define rock units, not to declare some big change in the Earth’s systems.” The Anthropocene is better used as a cultural term, like Neolithic, rather than as a geological one, Finney and others argue. Another concern is that geologists’ formal embrace of the term would be a political football. “It could have very important political implications,” says PhilipGibbard, Professor of Quaternary Paleoenvironments at Cambridge University, who originally proposed creating the AWG. He adds that advocates of action on climate change are already harnessing the idea to argue for reducing carbon emissions. But the Working Group “should deliberately avoid getting involved in politics,” he says, keeping its focus on the science. Some argue that massive manmade changes to the environment, such as this oilsands field in Northern Alberta, are indicative of a new epoch called the Anthropocene. Image courtesy of Shutterstock/Chris Kolaczan.