By Elizabeth Kolbert
A few years ago, in an essay in Nature, Nobel Prize-winning Dutch chemist Paul Crutzen coined a term. (1) Instead of the Holocene, he wrote, we should think of ourselves as living in the Anthropocene, an age defined by one species—man—that had become so dominant it was capable of altering the planet on a geological scale. Because he’s such a towering figure—Crutzen was the first scientist to warn that humans were damaging the ozone layer—his 2002 essay was read around the globe, and the term passed almost immediately into popular usage.
Crutzen has now published another essay (2) that is getting a lot of attention. In it, he suggests that dangerous climate change is closer than is generally acknowledged and that now is the time to start considering geoengineering. As is well known, volcanoes emit huge quantities of sulfur dioxide, producing a cooling effect that, at least temporarily, counteracts global warming. Crutzen proposes that sulfur could be injected into the stratosphere to create, in effect, a huge man-made volcano. In this way, one form of human interference in the climate could be balanced by another.
As Crutzen himself acknowledges, this is a scary prospect for many reasons, the first being that no one knows exactly what the side effects of injecting sulfur into the stratosphere would be. (One likelihood, ironically enough, is damage to the ozone layer.) Meanwhile, if greenhouse gas levels in the atmosphere continue to increase, the amount of sulfur needed to offset their effects will also keep rising. Then there’s the problem that, even if the warming effects of CO2 emissions could be offset, other negative consequences, such as ocean acidification, would continue unchecked. Many climate scientists regard geoengineering as a dangerous delusion, the moral equivalent of a smoke-free cigarette. In a response to Crutzen’s proposal that appeared in the same issue of Climatic Change (3), Michael MacCracken called geoengineering “in essence, an enabler for [an] undiminished addiction to fossil fuels.”
Whether or not geoengineering is feasible—let alone desirable—what strikes me as most frightening about Crutzen’s proposal is that he felt compelled to offer it. When one of the world’s leading atmospheric scientists says it’s time to start purposefully altering the atmosphere, you know that the alternatives must be pretty awful.
1. Crutzen, P.J. 2002. Geology of mankind. Nature 415(3):23.
2. Crutzen, P.J. 2006. Albedo enhancement by stratospheric sulfur injections: A contribution to resolve a policy dilemma? Climatic Change 77(3-4):211-220.
3. MacCracken, M.C. 2006. Geoengineering: Worthy of cautious evaluation? Climatic Change 77(3-4):235-243.
Elizabeth Kolbert is a staff writer for The New Yorker. She began reporting on climate change in 2001 after traveling to a research station on top of the Greenland ice sheet. Her three-part series on global warming, “The Climate of Man,” won this year’s National Magazine Award for public service. Her book on the subject, Field Notes from a Catastrophe, was published in March 2006.