The Ends of the World: Volcanic Apocalypses, Lethal Oceans, and Our Quest to Understand Earth's Past Mass Extinctions

by Peter Brannen

The End-Permian mass extinction is the absolute end-member—the worst-case scenario—for what happens when you jam too much carbon dioxide into the atmosphere.

“The headlines are not just inaccurate,” writes futurist Stewart Brand on the premature obituary for the planet that has become de rigueur in some circles. “As they accumulate, they frame our whole relationship with nature as one of unremitting tragedy. The core of tragedy is that it cannot be fixed, and that is a formula for hopelessness and inaction. Lazy romanticism about impending doom becomes the default view.”

I had written to Erwin to get his take on the now-fashionable idea that there is currently a sixth mass extinction under way on our planet on par with the Big Five. Many popular science articles take this as a given, and indeed, there’s something emotionally satisfying about the idea that humans’ hubris and shortsightedness are so profound that we’re bringing down the whole planet with us. Erwin thinks it’s junk science. “Many of those making facile comparisons between the current situation and past mass extinctions don’t have a clue about the difference in the nature of the data, much less how truly awful the mass extinctions recorded in the marine fossil record actually were,” he wrote me in an email. “I am not claiming that humans haven’t done great damage to marine and terrestrial extinctions, nor that many extinctions have not occurred and more will certainly occur in the near future. But I do think that as scientists we have a responsibility to be accurate about such comparisons.”

While Erwin’s argument that a mass extinction is not yet under way might seem to get humanity off the hook—an invitation to plunder the earth further, since it can seemingly take the beating (the planet has certainly seen worse)—it’s actually a subtler and possibly far scarier argument. This is where the ecosystem’s nonlinear responses, or tipping points, come in. Inching up to mass extinction might be a little like inching up to the event horizon of a black hole—once you go over a certain line, a line that perhaps doesn’t even appear all that remarkable, all is lost. “So,” I said, “it might be that we sort of bump along where everything seems okay and then . . .” “Yeah, everything’s fine until it’s not,” said Erwin. “And then everything goes to hell.” Or put another way, mass extinctions may unfold the same way that a dissolute character in Hemingway’s The Sun Also Rises explains that bankruptcies do: “Two ways. Gradually and then suddenly.” “The only hope we have in the future,” Erwin said, “is if we’re not in a mass extinction event.”

But for the very worst-case emissions scenarios, heat waves would not merely be a public health crisis, or a “threat multiplier,” as the US Pentagon calls global warming. Humanity would have to abandon most of the earth it now inhabits. In their paper, Huber and Sherwood write: “If warmings of 10°C were really to occur in the next three centuries, the area of land likely rendered uninhabitable by heat stress would dwarf that affected by rising sea level.” Huber said, “If you ask any schoolchild, ‘What were mammals doing in the age of the dinosaurs?’ they’d say they were living underground and coming out at night. Why? Well, heat stress is a very simple explanation. Interestingly, birds have a higher set point temperature—ours is 37 degrees Celsius, birds’ is more like 41. So I actually think that’s a very deep evolutionary relic right there. Because that wet-bulb temperature was probably maxing out around 41 degrees Celsius in the Cretaceous, not 37.”

His hopes for technology are nearly limitless—and, to others I would imagine, terrifying—and he wants to live to experience as yet unimagined technologically mediated states of being far more expansive than those allowed by the limited wet meat in our skulls. The human brain was shaped haphazardly by the ruthless (and goal-less) filter of natural selection and the limits of metabolism, but imagine what states of awareness and subjectivity could be achieved with a synthetic brain limited only by the ambition and imagination of its super-intelligent creators. With so much at stake, it’s not surprising that Sandberg spends the rest of his time wondering about what could foreclose such an expansive future and destroy the planet. These are the existential risks.

he wrote, in the best tradition of aspirational science fiction, about the expansive potential of humanity and of the generations of the far future: They will know that before them lie, not the millions of years in which we measure the eras of geology, nor the billions of years which span the past lives of the stars, but years to be counted literally in trillions. . . . But for all that, they may envy us, basking in the bright afterglow of Creation; for we knew the universe when it was young.

But when she was near the end, she was fond of quoting the English medieval mystic Julian of Norwich. “All shall be well, and all shall be well and all manner of thing shall be well,” she said. I didn’t buy it. The headlines made it daily more difficult to believe. At the same time that the only known habitable planet in the galaxy seems to be careening into geologic catastrophe, beheadings and crucifixions over centuries-old creeds, pandering nativist demagogues, and tribal recriminations dominate the newscasts. As a species, we seem so ill equipped for what lies ahead. Perhaps the trying changes of the coming centuries will prune us of our adolescent stupidity and superstition, and we’ll emerge as worthy and capable stewards of the world for millions of years to come. Perhaps we’re at the dawn of the Sapiezoic Eon*—a wild flourishing of intelligence and creativity, a new epoch as wondrous and different from the age of animals as that age was from the age of bacteria that preceded it. Or maybe the whole bizarre fever dream of humanity will be nothing more than a single strange sliver of stratigraphy, capped by mass extinction and buried in the canyons of the far future.