Back when I was a kid, I sometimes daydreamed about traveling back in time to the exotic Age of Dinosaurs in order to liven up what I thought was a relatively plain and insignificant existence in suburban Connecticut. It's easy to overlook the exceptional qualities of a familiar setting in this way unless someone calls attention to them. That's what has happened recently with our present-day position on the geologic time scale, thanks to a trendy new title.
Other more ancient epochs represented early phases of post-dinosaur evolution (Paleocene and Eocene) or multiple ice ages (Pleistocene). But this latest epochal name, originally coined by ecologist Eugene Stoermer and widely promoted by Nobel laureate Paul Crutzen, recognizes humankind as a transformative force of nature. No, it's not the "Plasticene." It's the "Anthropocene," which translates to "The Age of Humans."
I recently asked Stoermer about his term. "I used it in conferences here and there," he explained, "and it eventually caught people's attention." That's an understatement; the concept is now widely used in scientific circles and is seeping into mainstream culture, as well. Does he mind that the label is often incorrectly attributed to Crutzen? "No, the origination of ideas or terms isn't an issue with me. It's my own fault, anyway; I've got a big mouth but a lazy pen." And how does one pronounce it? "I say AN-thro-po-cene," Stoermer said, "although an-THROP-o-cene works, too."
The case for naming this segment of Earth's history after us is compelling. Farmers now spread more nitrogen fertilizer annually than all of the planet's forests, grasslands, and bird rookeries combined. The shadowed half of the planet now glows artificially as though covered with fireflies, and human-driven species invasions and extinctions are beginning to rival any in history. But perhaps the most pervasive influence of all comes from our heat-trapping fossil fuel emissions.
Geohistorical records show that natural greenhouse gas buildups triggered an intense warming period shortly after the demise of the dinosaurs, holding global mean temperatures at least 20°F higher than today for thousands of years. Forests cloaked both polar regions, sea levels stood hundreds of feet higher than today, the oceans acidified, and the carbon chemistry of all living bodies was distorted in ways that still show up clearly in fossils. Now, 55 million years later, we seem to be heading backwards in time toward that ancient greenhouse event as tree-lines once again shift poleward, the oceans rise and acidify, and a new global "carbon isotope excursion" contaminates our flesh and bones, skews chemical analyses of ecosystems, and even changes the apparent carbon-14 ages of recent artifacts.
The cause of that former hothouse is unclear, perhaps something to do with undersea volcanism. But we know exactly what's causing it now: Homo sapiens.
When did the Anthropocene begin? Some experts say it started when paleolithic hunters exterminated mammoths and mastodonts after the last ice age. Paleoecologist Bill Ruddiman suggests that deforestation and agriculture have been boosting CO2 and methane concentrations for the last 8,000 years, while still others say that the epoch began with the Industrial Revolution.
But even more interesting is what it will be like from here on out. The University of Chicago's pioneering climate modeler David Archer, along with a growing corps of like- minded visionaries, have some shocking things to tell us about that.
Using powerful new computer models with names like CLIMBER, GENIE, and LOVECLIM, Archer and others are peering beyond the horizon of 2100 AD that now limits most discussion about global warming to sketch outlines of the Anthropocene future that are truly geologic in scope. Though few non-specialists yet realize it, a sizeable fraction of the fumes leaking from our tailpipes and smokestacks will linger in the air not just for a few centuries but for tens of thousands of years, long enough to interfere with future ice ages.
According to the latest simulations, most of our CO2 will dissolve into the oceans within the next several millennia, but a fair bit of it will remain stranded aloft until slow geologic processes finally scrub the air clean. Even in the most moderate scenarios, the Earth will become significantly warmer than now all the way out to 100,000 AD. As Archer sometimes puts it, "global warming is essentially forever."
If this view of the Anthropocene is correct, then we who live in this century are endowed with the power—some might say the honor—to determine the climatic future of the planet. If we switch to non-fossil fuels soon, a long, slow recovery from a relatively modest warming peak of an additional 4°F or so will follow. But if we continue to burn coal, oil, and gas until resource depletion forces the switch later on, our emissions will drag the Earth back into a primeval super-warm state for much longer, maybe half a million years.
We are both the products and the producers of this new epoch, and within our lifetimes we will do much to determine its course into the deep future. In a literal sense that can be understood with or without a religious perspective, we're participating in a new creation, in the genesis of a world over which we hold a surprising degree of influence even as it continues to exert its own age-old influences on us.
Welcome, everyone, to this remarkable Age of Humans. Welcome to the Anthropocene.
Curt Stager is an ecologist, paleoclimatologist, and science journalist with a Ph.D. in biology and geology from Duke University. His new book is DEEP FUTURE: The Next 100,000 Years of Life on Earth (St. Martin's Press, March 2011).