Five years ago I considered the proposal, by Nobel laureate Paul Crutzen, that we should declare ourselves in a new geologic age, the Anthropocene. I was skeptical: couldn't we make the same point by naming the Anthropocene as a time unit of age rank within the Holocene epoch, without doing violence to the current order? I thought that would raise consciousness enough about our power to change the planet.

But a group of researchers who know better than I have looked hard at Crutzen's idea and at the Earth. And in the February issue of GSA Today they argue that Earth really has entered a new era since the Industrial Revolution. Wherever the Earth is headed, it is no longer in the ordinary interglacial period that marks the Holocene Epoch. That is a sobering thing to conclude. It may well come to pass that science will write large Walt Whitman's insight about America, "here at last is something in the doings of man that corresponds with the broadcast doings of the day and night." This would be epochal in the old-fashioned sense.

But where would be the base of this new time unit? The researchers consider some heavy-duty markers, like the radioactivity pulse of the 20th-century atomic bomb tests or the fateful rise in atmospheric CO₂. But their favored event, the global geochemical signals and tree-ring disturbance from the 1815 eruption of Tambora, is also great and will suffice.
A contribution to Accretionary Wedge #6