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. At the dinner parties that followed, they indulged in less conventional speculation.
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.
One day in 2017, Schmidt received a visit from Adam Frank, a University of Rochester astrophysicist seeking insight into whether civilizations on other planets would inevitably alter their climates like we have. Truth be told, Frank expected his alien conjecture to come across as mildly outlandish.
He was surprised when Schmidt interrupted with an even stranger idea, one he’d been incubating for years: “What makes you so sure we’re the first civilization on this planet?”
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