Like other similar heat waves deep in Earth’s past, the crisis was accompanied by sweeping extinctions. A menagerie of lumbering beasts (many of them unfairly consigned to the C-list of natural-history museums), like rhynchosaurs and dicynodonts, was all but exterminated; while in the ocean the disaster is marked by a massacre of reefs, sea lilies, shelled octopus relatives, and a sinuous group of marine reptiles called thalattosaurs.
Oxygen isotopes from the fossil teeth of tiny sea creatures reveal that the entire episode was kicked off by warming of only about 4–7 degrees Celsius—roughly the same magnitude predicted for our own world under a business-as-usual carbon-emissions scenario.
“We don’t need an experiment in a laboratory to tell us what happens when CO2 rises quickly, because it’s there in the rocks,” Bernardi told me about this ancient natural experiment that the planet ran all on its own. “It is written.”
But perhaps the most extraordinary aspect of the Carnian Pluvial Episode was not the crisis itself, but the world that came after. Until then, dinosaurs had been a puny and obscure lineage confined to the furthest southern reaches of Pangaea. But by the time the crisis was over, they had spread all over the world—perhaps using the oddly humid pulse to hopscotch across the previously arid wastelands of Pangaea—and rapidly diversified, using the extinction of their competitors to experiment with new lifestyles. The planet would never be the same.
Bernardi pulled the museum truck up next to a typical tree-frosted colossus of beige rock that loomed over the valley floor. Halfway up, the cliff face was improbably interrupted by a crumbling medieval castle that had somehow been built into it more than 800 years ago. The castle apparently belonged to an older woman who waylaid us from her car window to complain to Bernardi in Italian about some teen trespassers, before driving away. Bernardi strapped on a helmet.
“You should not go up there, it’s not the safest place,” he said, pausing to size up the cliff before us. “It can be done.”
With that, we began climbing.
The rocks before us, some studded with seashells, were from sometime in the middle of the Triassic—an endlessly fascinating period that lasted from 252 to 201 million years ago. The Triassic was one of the most unstable periods in the history of life. It kicked off in the wretched and scorching aftermath of Armageddon, as the planet struggled to recover from the greatest mass extinction it would ever endure, the dread End-Permian mass extinction. (Earth’s cruelty to its own creatures knew no bounds in this terrible age, as a mere 3 million years after the apocalypse another minor mass extinction, the “Smithian-Spathian,” would punish the survivors for their courage.) And the Triassic concluded 50 million years later with a terrifying runner-up to doomsday: the End-Triassic mass extinction (like the Carnian Pluvial Episode, both the End-Permian and End-Triassic mass extinctions were carbon dioxide–driven global-warming disasters). But sometime between these bookending nightmares came the impressive rise of the dinosaurs, mammals, and crocodilians, as well as modern conifers, corals, and even plankton. The Carnian Pluvial Episode has long been seen as something of a stratigraphic curio buried in the middle of this stack of time, dismissed by some geologists as a local or unimportant event. But amazingly, as the fossil record has come into finer resolution in recent years, not only has an overlooked mass extinction been uncovered in the Episode, but the closer the dramatic origin of all these creatures has edged toward the immediate aftermath of the mysterious event as well. It marked just as much a planetary birth as death.