This is “Climate week” in New York City, and my inbox has been awash recently in the latest press releases about start-ups and noble initiatives and venal greenwashing. Much of it’s important, and I’ll get to some of it later, but there’s a big new study that came out last week in Science that sets our crucial moment in true perspective. Let’s step back for a moment.
This new study—a decade in the making and involving, in the words of veteran climate scientist Gavin Schmidt “biological proxies from extinct species, plate tectonic movement, disappearance in subduction zones of vast amounts of ocean sediment, and interpolating sparse data in space and time”—offers at its end the most detailed timeline yet of the earth’s climate history over the last half-billion years. That’s the period scientists call the Phanerozoic—the latest of the earth’s four geological eons (we’re still in it), and the one marked by the true profusion of plant and animal life. It’s a lovely piece of science, and it’s lovely too because it reminds us of all we’re heir to in this tiny brief moment that marks the human time on earth. So staggeringly much—strange and extreme and fecund—has come before us.
But it’s also scary as can be, for two big reasons.
The first is that it shows the earth has gotten very very warm in the past. As the Washington Post explained in an excellent analysis yesterday, “the study suggests that at its hottest the Earth’s average temperature reached 96.8 degrees Fahrenheit (36 degrees Celsius).” Our current average temperature—already elevated by global warming to the highest value ever recorded—is about 60 degrees Fahrenheit, or 15 degrees Celsius. For most of the 500 million years the study covers, the earth has been in a hothouse state, with an average temperature of 71.6 Fahrenheit, or 22 Celsius, much higher than now. Only about an eighth of the time has the earth been in its current “coldhouse” state—but of course that includes all the time that humans have been around. It is the world we know and we’re adapted to.
In every era, it’s increases in carbon dioxide that drive the increases and decreases in temperature. “Carbon dioxide is really that master dial,” Jess Tierney, a climate scientist at the University of Arizona and co-author of the study, said. And so the study makes clear that the mercury could go very high indeed as humans pour carbon into the sky. We won’t burn enough coal and oil and gas to reach the very highest temperatures seen in the geological record—that required periods of incredible volcanism—but we may well double the amount of carbon in the atmosphere, and this study implies that the fast and slow feedbacks from that could eventually drive temperatures as much as eight degrees Celsius higher, which is more than most current estimates. Over shorter time frames the numbers are just as dramatic
Without rapid action to curbgreenhouse gas emissions, scientists say, global temperatures could reach nearly 62.6 F (17 C) by the end of the century — a level not seen in the timeline since the Miocene epoch, more than 5 million years ago.
Now, you could look at those numbers and say: well, the earth has been hotter before, so life won’t be wiped out. And that’s true—there’s probably no way to wipe out life, though on a planet with huge numbers of nuclear weapons who knows. But these temperatures are much higher than anything humans have experienced, and they guarantee a world with radically different regimes of drought and deluge, radically different ocean levels and fire seasons. They imply a world fundamentally strange to us, with entirely different seasons and moods—and if that doesn’t challenge bare survival, it certainly challenges the survival of our civilizations. Unlike all the species that came before us, we have built a physical shell for that civilization, a geography of cities and ports and farms that we can’t easily move as the temperature rises. And of course the poorest people, who have done the least to cause the trouble, will suffer out of all proportion as that shift starts to happen.
But that’s not the really scary part. The really scary part is how fast it’s moving.
In fact, nowhere in that long record have the scientists been able to find a time when it’s warming as fast as it is right now. “We’re changing Earth’s temperature at a rate that exceeds anything we know about,” Tierney said.
Much much much faster than, say, during the worst extinction event we know about, at the end of the Permian about 250 million years ago, when the endless eruption of the so-called Siberian traps drove the temperature 10 Celsius higher and killed off 95 percent of the species on the planet. But that catastrophe took fifty thousand years—our three degree Celsius increase—driven by the collective volcano of our powerplants, factories, furnaces and Fords—will be measured in decades.
Our only hope of avoiding utter ruin—our only hope that our western world, in the blink of an eye, won’t produce catastrophe on this geologic scale—is to turn off those volcanoes immediately. And that, of course, requires replacing coal and gas and oil with something else. The only something else on offer right now, scalable in the few years we still have to work with, is the rays of the sun, and the wind that sun produces, and the batteries that can store its power for use at night.
Another new analysis this week, this one from the energy thinktank Ember, shows that 2024 is seeing another year of surging solar installations—when the year ends there will be 30% more solar power on this planet than when it began. Numbers like that, if we can keep that acceleration going for a few more years, give us a fighting chance.
That’s what all those seminars and cocktail parties and protests in New York over this week will ultimately be about—the desperate attempt to keep this rift in our geological history from getting any bigger than it must. As this new study once more makes clear, raising the temperature is by far the biggest thing humans have ever done; our effort to limit that rise must be just as large.
We need to stand in awe for a moment before the scope of earth’s long history. And then we need to get the hell to work.
