Earth scientists at the turn of the century, Gavin Schmidt among them, were enthralled by a 56-million-year-old segment of geologic history known as the Paleocene-Eocene Thermal Maximum (PETM). What most intrigued them was its resemblance to our own time: Carbon levels spiked, temperatures soared, ecosystems toppled. At professional workshops, experts tried to guess what natural processes could have triggered such severe global warming.
During one such affair, Schmidt, now the director of NASA’s Goddard Institute for Space Studies, couldn’t resist the comparison. If modern climate change — unambiguously the product of human industry — and the PETM are so alike, he mused, “Wouldn’t it be funny if it was the same cause?” His colleagues were charmed by the implication. An ancient race of intelligent, fossil-fueled… chickens? Lemurs? “But,” he says, “nobody took it seriously, obviously.” Until, nearly two decades later, he took it seriously himself.
Take the analogy where the planet’s entire history is compressed into a single day: Complex life emerged about three hours ago; the industrial era has lasted only a few thousandths of a second. Given how rapidly we are rendering our home uninhabitable, some researchers think the average lifespan of advanced civilizations may be just a handful of centuries. If that’s true, the past few hundred million years could hide any number of industrial periods.
With Adam Frank, a University of Rochester astrophysicist seeking insight into whether civilizations on other planets would inevitably alter their climates like we have, The conversation and the thought experiment ensued, Surely we would know if another species had colonized the globe like Homo sapiens did. Or. . . . would we?