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If all three realms are ruined—sea and land and sky—
Then we shall be confounded in old Chaos.
Save from the flames what’s left, if anything can still be saved.
Think of the Universe!
—Ovid, Metamorphoses
From 2016 onward, the fire seasons in both hemispheres have been relentless. In 2017, British Columbia, a huge coastal province bigger than Alberta, bigger than Chile, and more than twice the size of California, set a new global record. On July 7 alone, 142 separate wildfires ignited; by the end of the day, the province was in a state of emergency. A familiar combination of high heat, drought conditions, and wind caused many of those fires to grow rapidly into uncontrollable blazes. A month later, many of them were still burning. On August 12, four of the larger fires, along with one across the border in Washington State, erupted almost simultaneously into pyroCb thunderstorms, a phenomenon never observed before. David Peterson, a meteorologist at the U.S. Naval Research Laboratory in Monterey, California, speaking to the CBC, declared it “the most significant fire-driven thunderstorm event in history. Nothing else even comes close.” Once in the stratosphere, the mass of particulate was swept into the jet stream, where it circled the globe for four months.
The only mercy shown British Columbia that summer was that most of the fires ignited in sparsely inhabited areas. Even so, more than forty thousand people were displaced across the province, firefighting costs alone exceeded half a billion dollars, and almost five thousand square miles of forest burned. Though it was hundreds of miles from the biggest fires, the sky in Vancouver turned a burnt-orange color for weeks, and the air quality was rated some of the worst in the world. British Columbia’s historic aerosol injection, which has come to be known as the “Pacific Northwest Event,” was more than twice the size of any previously documented pyroCb.
But if twenty-first-century fire has taught us anything, it’s that there is no top end. It wasn’t long before the Pacific Northwest Event, “the mother of all pyroCbs,” had company. In 2020, the—once again—record-breaking fire seasons in Australia, California, and Oregon generated similarly volcanic pyroCbs. Australia’s, however, was—how many times can one say this?—unprecedented. Most readers will be familiar with the horrific fires that appeared to envelop that country in December and January of 2019–20, and with the shocking number of animals that perished. But high above Earth, something else was happening, too. An abstract describing it in the journal Communications Earth & Environment reads like a scientist’s description of a cataclysm from the Old Testament:
The Australian bushfires around the turn of the year 2020 generated an unprecedented perturbation of stratospheric composition…The resulting planetary-scale blocking of solar radiation by the smoke is [three times] larger than any previously documented wildfires and of the same order as the radiative forcing produced by moderate volcanic eruptions. A striking effect of the solar heating of an intense smoke patch was the generation of a self-maintained anticyclonic vortex measuring 1000 km. in diameter and featuring its own ozone hole. The highly stable vortex persisted in the stratosphere for over 13 weeks, travelled 66,000 km and lifted a confined bubble of smoke and moisture to 35 km altitude.
In other words, ferocious heat convection drove a climate-altering quantity of ash and particulate eight miles into the stratosphere, where it then formed an aerosol blob, six hundred miles wide and two miles thick. Because it contained so much water vapor and black carbon, it absorbed solar energy, which caused it to heat up and rise still further—en masse, like a black balloon the size of Texas—until it was more than twenty miles above the earth, twice as high as any previously known pyroCb injection. Once there, this half-million-cubic-mile pyrogenic carbon blimp drifted for more than three months around the Southern Hemisphere, covering forty thousand miles before finally dissipating.
In the 1990s, pyroCbs were a disturbing but exhilarating novelty wondered at, and discussed by, a small group of meteorologists. Now, they are not only a signature of major wildfires, they are actively growing in size and frequency—to the point that they are mimicking volcanoes, previously Earth’s most rapid and powerful climate-changing agents. PyroCbs are now being observed all over the world in places they have never been reported before. As these events multiply, they are altering, in significant and measurable ways, the chemical composition of what atmospheric scientists refer to as the “stratospheric overworld.”
This is the power of atmospheric CO2. It expresses itself through heat retention, and its “vocabulary” appears to be growing, most obviously through variations in weather, fire, and related phenomena, but in other, less visible ways as well, most notably in the oceans. The oceans absorb approximately 30 percent of all emitted carbon dioxide. Over the course of the Petrocene Age, this global system, home to more than half of the world’s species, has grown 30 percent more acidic, signaling the most rapid shift in ocean chemistry in the past 50 million years.
What the atmosphere and oceans are telling us is that carbon dioxide doesn’t get the respect it deserves. Others have been saying this, too—for a long time. Roger Revelle said as much to a congressional subcommittee in 1956. Eunice Foote said it to the American Association for the Advancement of Science in 1856. Any climate scientist or environmental studies teacher will tell you every chance they get. Until very recently, most of them have been tuned out, brushed off, or appeased in ways that bear a strong resemblance to the experience of people reporting incidents of sexism or racism: “Where? I can’t see it.”
The conclusion arrived at by the Communications article’s dozen authors is that a big enough pyroCb “eruption” could inject enough carbon into the stratosphere to alter the planet’s climate, just as large volcanic eruptions have done in the past. Pollution and air quality aside, the carbon dioxide generated by events of “planetary scale”—like twenty-first-century wildfires—exceeds the annual CO2 output of many states and countries. To put this in perspective, the CO2 emitted by the Australian bushfires of 2019–20 more than compensated for the global reduction caused by the coronavirus pandemic.
It hardly needs to be said that more CO2 leads to more heat retention, which leads to more fires, which leads to more pyroCbs…We are, right now, witnessing the early stages of a self-perpetuating and self-amplifying feedback loop, accompanied by myriad “cascade effects.”[*1] In human terms, this has been a long time coming, but in geologic terms it has taken place overnight—roughly seven human generations, or two life-spans. So limited are we by the brevity of our lives and, lately, by the kaleidoscopic swirl of technological advancement, further amplified by a twenty-four-hour news cycle, that it’s hard to appreciate how far we’ve come (and gone) in such an extraordinarily short time.
I was born in the 1960s, but I personally knew people born in the 1870s and ’80s, when the petroleum industry was in its infancy and Standard Oil was a start-up. The Civil War, waged by horse- and manpower, was a raw and recent memory then; Queen Victoria reigned over a global empire held together by sailing ships, and the climate visionaries Svante Arrhenius and Arvid Högbom were still in high school. In 1875, Chicago was still rebuilding after its great fire, the battle at Little Big Horn had not yet been won or lost, and boreal explorers were still fantasizing about how men might one day turn Alberta bitumen into money. Back then, 1.3 billion people walked the planet—literally, because there were no cars. Nor was there plastic, and the Keeling Curve of CO2 had only just begun its relentless upward bending. That world—the same one into which people whose hands I touched were born—is so close temporally (I looked into their eyes; I felt their breath), and yet it is so remote chemically, biologically, atmospherically, technologically, anthropogenically from the world we inhabit now, the world we are currently unmaking, the world our children are inheriting that resembles, less and less, the one that made us.
Our unprecedented success (and emissions) are due first to our mastery of fire, and second to our exploitation of fossil fuels in all their varied forms. In terms of its implications for life on Earth, our historically brief experiment with a fossil fuel–driven civilization is, in essence, a high-intensity carbon release project. Nature accomplishes the same thing with forest fires and volcanoes, but not nearly as efficiently, or as quickly, as we are doing now. Every year, this global industry releases ten gigatons of carbon in the form of coal, oil, and gas formerly sequestered in the planet’s crust.[*2] This is a rate roughly ten times faster than anything scientists can find in the geological record for the past 250 million years, and about one hundred times faster than natural systems were releasing it in more recent pre-industrial times. This is how Earth will remember us: thanks to fire and our appetite for its boundless energy, we have evolved into a geologic event that will be measurable a million years from now.
Viewed through this lens, twenty-first-century fire is not so much an aberration as a by-product of our principal accomplishment. Setting aside the ephemeral distractions of culture and civilization, modern humanity—Homo flagrans—will be remembered, above all, for building, and for being, the greatest combustion engine ever devised. In terms of heat, energy, and emissions, we are a supervolcano representing the largest, most rapid release of combustive energy, carbon dioxide, and methane since the Permian Age.
And that is saying something.
The Permian Age commenced roughly 300 million years ago, and it started well enough. Jungles and forests of ferns, cycads, and conifers flourished across the landscape. Into this oxygen-rich environment evolved the first truly massive creatures, including sail-backed reptiles like dimetrodon, and ambiguous proto-mammals like the gorgonopsids, whose saber teeth were set in jaws that opened as wide as bear traps. Flying overhead were the largest insects the world has ever known. Meganeuropsis was a dragonfly-like creature with a thirty-inch wingspan whose four thrumming wings must have sounded like the rotors on a quadcopter drone. Down below, the Permian ocean, though poorly represented in the fossil record, supported fish and squid in sufficient abundance to feed whale-sized sharks, some with continually cycling teeth oriented like buzz saws (or bucketwheels). But what makes the Permian noteworthy, and relevant now, is not how it began, but how it ended.
During this period of 50 million years, Earth’s landmass was a supercontinent, a compressed jigsaw puzzle now called Pangaea. There was ice at the poles then, too, and in its Northern Hemisphere, in what is currently Siberia, a series of massive volcanic eruptions began at the tail end of the Permian Age, about 250 million years ago. Without them, the Permian might have continued for another 50 million years. As the planet tore open, and magma jetted to the surface like an arterial wound, millions of square miles of the surrounding landscape was inundated by flowing lava, which hardened over time into basalt layers more than a mile thick, forming what geologists now call a “large igneous province.” These planetary growing pains also drove magma horizontally through seams in the planet’s crust, effectively fracking vast fossil fuel deposits laid down by even older seas and forests. The results were spectacular; according to geologists, some of these molten injections detonated gas explosions that left craters a half mile wide. This pressurized magma also found its way into ancient coal beds, where it smoldered and burned for hundreds of millennia.
While not as systematic or as broadly distributed as our fossil fuel emissions, this period of extended, volcano-driven combustion did the same thing we are doing today: it burned everything it came across as rapidly as possible. Then, as now, the inevitable result was an extraordinary amount of smoke, ash, water vapor, and carbon dioxide in the atmosphere—thousands upon thousands of gigatons, far more than existing plants, oceans, and chemical weathering could absorb and process. Thousands of gigatons may sound like a lot, but for most readers (and this writer), it is a meaningless measure, especially in the context of air, which doesn’t appear to weigh anything, or the atmosphere, which appears infinite. Simply put, it’s the carbon that gives carbon dioxide its weight, and carbon dioxide weighs about two ounces (fifty grams) per cubic foot (the Chevy Silverado emits about two pounds of CO2 for every mile driven).
Numbers aside, we’ve all seen a polluted city, and we’ve all been in a smoky room, and we’ve all seen a surface coated with soot. We can imagine that it takes an extraordinary quantity of carbon dioxide to register as weight on a scale—in grams or ounces, let alone gigatons. And we all know that the smokier a room gets the smaller it feels and the harder it is to see, to breathe, to think, to live. Imagine this room filling with so much ash, methane, and CO2 (from your barbecue, from your vehicle, and from the pig farm, the coal-fired power plant, and the oil refinery up the road) that virtually everything (plants, animals, birds, fish, and insects) overheated, suffocated, and died.
That’s how the Permian ended.
Paleontologists call it the Permian-Triassic Extinction Event. Lee Kump, dean of the College of Earth and Mineral Sciences at Pennsylvania State University, calls it “the worst thing that’s ever happened.” It left behind a planet unrecognizable and virtually uninhabitable. In addition to an Alaska-sized slab of lifeless basalt in Siberia, the geologic record reveals Martian red rock and vast deposits of salt in Kansas. In between, in all directions, more than 70 percent of all terrestrial species went extinct. Then, as now, roughly 30 percent of all emitted carbon dioxide is absorbed by the oceans, where it is converted into carbonic acid. At the end of the Permian, with CO2 levels in the thousands of parts per million and ocean temperatures above 100°F at the equator, those ancient seas became so acidic, and so hot, that more than 90 percent of all marine species died out. In recent times, the mysterious tooth whorls of the “buzz saw” shark, helicoprion, have turned up on riverbanks in western Australia and in phosphate mines in Idaho, but little else remains. There have been five major extinctions in Earth’s history, but only the end-Permian has been called “the Great Dying.”
It is to this terminal catastrophe—caused, not by meteorites, or by shifts in Earth’s orbit, but by unrelenting combustion—that geoscientists are comparing our own Petrocene Age. Our fire-powered civilization is now in the early stages of replicating that “once-in-a-lifetime” extinction event. It is widely understood in the scientific community that a sixth major extinction is under way, and that it is wholly due to human activity. As confronting as this idea may be, it shouldn’t come as a surprise: never in Earth’s history has there been a disruption like us: billions of large, industrious primates whose evolving behavior is almost entirely dependent on the universal burning of hydrocarbons. Nor has Earth ever had to carry (at the same time, no less) billions of methane-emitting livestock the size of pigs and cattle.[*3][*4]
There is a terrible symmetry in this. What we are allowing to happen now with carbon dioxide and methane is what cyanobacteria did with photosynthesized oxygen billions of years ago: gassing the planet to death.
Men have become the tools of their tools.
— Henry David Thoreau
In his delightful and illuminating book The Botany of Desire, Michael Pollan demonstrates how four local plants with pleasing and useful qualities—potatoes, apples, tulips, and marijuana—harnessed human beings to propagate them globally, thereby changing the world. Fire is the ultimate expression of this “domestication” of desire. As Orkney Islanders and voyageurs did for the Hudson’s Bay Company, and as Newfoundlanders have done for the bitumen industry, human beings are doing for fire: we are its willing servants, working for a pittance compared to the fabulous and world-changing “profits” (increased flammability and carbon dioxide) being derived from our labors. As far as Pollan’s plants, or our fire, are concerned, humans are simply zombie hosts obediently disseminating their seeds, tubers, sparks, and gases around the globe. In the end, the geologic record will show that it is we who served fire, who enabled it to burn more broadly and brightly than it ever has before. Fire, thus far, has mastered us.
We are still a long way from Permian levels of carbon dioxide and temperature, but we are currently on pace to replicate the much more recent mid-Pliocene Warm Period, which ended 3 million years ago. With the seas and continents close to their current configuration, the mid-Pliocene offers a useful analog for our near future. At that time, our ancestors were still in Africa. Lucy (Australopithecus afarensis) was laying the groundwork for us in present-day Ethiopia, walking upright and experimenting with the crudest of stone tools. The Pliocene world was certainly habitable, but in a dramatically different way—not so much because of who lived in it, but because of the amount of atmospheric carbon dioxide. In Lucy’s day, CO2 levels were in the 400 ppm range, commensurate with ours right now, but average temperatures were 4–6°F warmer, the current prediction for the end of this century. With far less year-round ice, global sea levels were about eighty feet higher than they are today. Currently, almost half of the human population lives in coastal areas that were underwater when Lucy lived.
Just as the elders among us knew people who lived in the pre-Anthropocene climate, young people today are going to experience a version of this new Warm Period scenario, which has already begun. In this sense, the generations alive today represent a bridge between the lost world of a pre-industrialized atmosphere and a future defined ever more sharply by the rapid, increasingly violent discontinuities we are experiencing now. We may be a force of Nature, but we are not a mature one: like adolescents through all of time, petroleum burners want the power, but not the responsibility. In this way, we (the species) are not so different from a fire.
The immediate future—the next decade or so—is a kind of ultimate test: Are we, in our teeming, burning billions, capable of achieving some kind of equilibrium with the planet’s carrying capacity, and with its ability to buffer methane and carbon dioxide? The long-lost creatures of the Late Permian had no choice, and no recourse, and the same is true for every species alive today—except us. The current moment is the greatest challenge humanity has faced since we (almost) mastered fire. This time, it is not fire we have to master, but ourselves. If we fail this test, there will be another one, and another after that, but each time the stakes will be higher and the price of failure steeper. On the bright side, life—in one form or another—has always won out against the unregulated, hyper-consuming impulses of fire and its most durable by-products, ash, methane, and carbon dioxide. That there will be life at the end of the Petrocene Age is a certainty, but whose, how much, and where is less clear.
In 1959, almost a decade before the Great Canadian Oil Sands plant was opened, Robert Dunlop, the president of the company that built it, was warned, explicitly, by one of the most influential scientists of his day, about the warming effects of carbon dioxide generated by fossil fuel. Two years before that, the oceanographer and climate scientist Roger Revelle had warned Representative Albert Thomas and members of his House subcommittee of an impending phase shift in the rain and climate patterns of the southwestern United States. Variations on these warnings have been repeated, in every medium and format, ever since. If the powers that be couldn’t see it coming, it was not because they weren’t warned. Lucretius might just roll his eyes and say, “What did you expect?”
Those early predictions, along with many others like them, have come to pass, and with devastating consequences that intensify by the year. In the summer of 2021, the U.S. Bureau of Reclamation, which manages water resources for 40 million people in the Colorado River Basin, issued its first-ever water shortage declaration. Recent photos of reservoirs across the Southwest and California show trees and lake bottoms that haven’t been visible since they were submerged many decades ago. Farther north, on the Oregon-California border, the Bureau of Reclamation shut down the Klamath River Basin’s extensive irrigation system for the first time in its 115-year history, impacting everything downstream from waterfowl and salmon habitat to agriculture and cattle ranches.[*5]
“This isn’t a ‘drought,’ ” wrote the climate journalist Bob Berwyn in 2020, “because that implies recovery. This is aridification.” Aridification precedes desertification.
This is what Revelle saw coming in the 1950s: a persistent new regime with no foreseeable endpoint. Based on tree ring analysis, it has been determined that the American West is currently in the most severe drought of the past 1,200 years. Rainfall cycles are naturally variable and difficult to predict, but CO2, it has been said, is like steroids for the atmosphere: as fossil fuels have empowered us, so have our emissions turned a heavy hitter (the heat-retaining capacity of our atmosphere) into a record-breaking slugger. The implications for fire go without saying.
Evidence of a similar drying trend has been observed in Canada’s boreal forest, also since the 1950s. In the meantime, scientists have determined that for every 1°C of warming (about 2°F) a 15 percent increase in precipitation is necessary to compensate for the increased evaporation. This is the exact opposite of what is happening in the boreal forest. Around Fort McMurray, average temperatures for the coolest months (October–April) have warmed by 3.4°C (about 6°F) over the past fifty years while precipitation has dropped by half. A similar phenomenon is being observed across Russia and Alaska, and it goes a long way toward explaining why fires in the circumboreal are burning earlier, faster, hotter, longer, and farther north: the boreal forest is no longer the same forest. This is not proprietary information; it is available to anyone interested in the boreal ecosystem, or in protecting the people who live and work there.
In the twenty-first century, not even tundra is immune. During the summer of 2007, Alaska saw what was then the largest tundra fire ever recorded. Ignited by lightning, the Anaktuvuk River fire burned a treeless area covering four hundred square miles, in spite of the permafrost that lay melting beneath it. With the scientist’s characteristic understatement, Syndonia Bret-Harte, a coauthor of a Nature article on this landmark event, pointed out, “Fire has been largely absent from tundra for the past 11,000 or so years.” Her colleague Michelle Mack dropped another bomb: “The amount of carbon released into the atmosphere from this fire is equivalent to the amount of carbon stored [annually] by the [pan-arctic] tundra biome. This was a boreal forest-sized fire.”
A decade later, in 2017, Greenland experienced its first significant wildfire, a stunning development given that Greenland is treeless and frozen solid save for tenuous patches of tundra on the coastal margins of the ice cap. In 2016, Tasmania, on the opposite end of the planet, experienced its driest spring and hottest summer in recorded history, during which rain forests that have not burned in a thousand years caught fire. In 2015, fires in Indonesia, many of which were associated with land clearing for palm oil plantations, burned ten thousand square miles of forest. In 2012, wildfires burned more than eight thousand square miles of boreal forest in Siberia. In 2010, pan-Russian wildfires burned more than three thousand square miles of forest, impacting heavily populated areas around Moscow. According to the global reinsurer Munich RE, 56,000 deaths that summer were attributable to smoke and record-breaking temperatures. All of these fires may have ignited several years and thousands of miles apart, but the link between them is persistent heat and drought.
That, and peat.
Underneath the trees, grass, and shrubs that compose many forests from Alberta to Siberia, and from Indonesia to Tasmania, lies a layer of compressed, decayed plant material. Like tundra (and muskeg), peat functions like a sponge, and its natural state is to be wet, often underlaid by permafrost—in other words, unburnable. However, when dried sufficiently, peat burns very well indeed, and households across northern Europe have heated with it for millennia. Prior to the twenty-first century, it took a lot of human intervention—digging, cutting, and drying—to make peat flammable, but now it is drying out and igniting in situ. Once lit, peat fires are extraordinarily difficult to put out. In Russia, following the worst fire season in the country’s history (2021), smoldering peat was reported in the dead of winter at -76°F.
Like the Anaktuvuk River tundra fire, one of the principal reasons the Tasmanian, Canadian, Russian, and Indonesian fires burned as they did is because the peat beneath them has dried in place, transforming these historically soggy forest floors into vast beds of fire-ready biofuel. Trees are no longer necessary to sustain fire. Troy O’Connor, the owner of a commercial firefighting company in Red Deer, Alberta, who was on hand for the Fort McMurray Fire, described to me muskeg bogs that have desiccated lately to depths of eight feet. Under these conditions, peat bogs (or tundra) can smolder indefinitely, like a coal seam fire. And, like coal dust, peat dust is explosive. The Indonesian peat fires of 2015 emitted nearly a billion tons of CO2, comparable to the annual emissions of New York, Texas, and California combined. According to Mike Flannigan, research director of the Western Partnership for Wildland Fire Science at University of Alberta, the boreal forests of Canada and Alaska contain thirty times as much peat as Indonesia.
With every degree of warming, there is a 12 percent increase in lightning[*6] activity, a common cause of wildfires (and the only cause in the uninhabited Arctic and boreal regions). The drier and hotter peat bogs and forests become, the easier they are to ignite by lightning and other means and, with milder winters, the earlier in the season they are able to do so. The drier the fuel and the hotter the air, the more explosive the fires, the more intensely they burn, the harder they are to extinguish, and the more likely they are to produce their own weather in the form of wind and pyrocumulus clouds, which can generate fire whirls, tornadoes, and more lightning, resulting in yet more fires that will perpetuate themselves for as long as fuel and weather conditions allow. Over the past several decades, this feedback loop has been tightening, not only in the circumboreal forest but across virtually every major forest system from Norway to Chile. In southern British Columbia, in 2021, Troy O’Connor saw fire weather drought codes over 1,000 (the forest fuel equivalent of a fifty-inch rainfall)—a number that would have been simply inconceivable even a decade ago.
Truly sobering in consideration of our current circumstances is that, even 120 years ago, early climate scientists recognized and accounted for what was then referred to as “mutual reaction,” now commonly known as positive feedback. Should the feedback loop of heating and drying continue to intensify as it has been, there is in our future a potentially winter-less scenario in which fire weather is the only weather, and “fire season” never ends. Australia and the American West are facing this reality already.
The influence of feedback is measurable with rain gauges, thermometers, and calendars, but its effects can be quantified in more oblique ways as well. In Kyoto, Japan, where cherry blossom season has been a national event celebrated for centuries, the date of peak blooming has grown steadily earlier over the past 150 years, tracking almost perfectly with Guy Callendar’s and NASA’s temperature graphs, and with Keeling’s CO2 curve. March 26, 2021, was the earliest date for peak blooming in 1,200 years of continuous record-keeping. Meanwhile, in the Arctic and subarctic, tree species have been migrating northward ever since the end of the last glaciation, a natural response to retreating ice and warming soils. In Alaska, this northward march has occurred at a rate of roughly half a mile per century. In the past few decades, however, the pace has quickened, with one result being that landscapes that have not known trees in more than 100,000 years, since before the last ice age, are now hosting young forests. These new forests, which may be only a decade old, are already burning down as landscapes that have never known fire become increasingly susceptible to combustion due to radical increases in temperature, evaporation, and lightning strikes. This heat-driven acceleration has been observed in other contexts as well. During the summer of 2019, a record-breaker in Alaska, where wildfires and smoke filled the state, hundreds of thousands of salmon died of heatstroke before they had an opportunity to spawn. At the same latitude, Greenland’s ice cap is now melting at a rate ominously described as “nonlinear”—that is, out of phase with any known precedent, pattern, or cycle. Over the past three decades, the average temperature there has increased by 5°F, with summer temperatures soaring 40°F above normal. During this same period, the rate of melting has increased by a more than a third. “What seems clear now,” wrote Jon Gertner, historian and author of The Ice at the End of the World, “is that Greenland is no longer changing in geological time. It is changing in human time.”
This is a first.[*7]
Starting around 1980, when atmospheric CO2 hit 340 ppm for the first time in a million years, annual global temperatures began rising more steadily, with smaller deviations. Since 2000, every year has been trending warmer than the last, and, since 2010, these annual increases have been steadily greater. By almost any measure, anyone born after 1990 is finding themselves in a new geological era, navigating a world fundamentally different from the one Baby Boomers and Gen Xers inherited. The chances of anyone alive today experiencing a year as relatively cool as 1996 are effectively nil.
Cristi Proistosescu, a professor of climate dynamics at the University of Illinois, suggested a more forward-looking way to conceptualize this warming trend. After posting a graph of rising global temperatures, he tweeted, “Just wanna make sure everyone understands what we’re looking at here: Don’t think of it as the warmest month of August in the last century. Think of it as one of the coolest months of August in the next century.”
Two decades into the twenty-first century, the Anthropocene Epoch is proving itself to be one of radical, hitherto unimaginable, planetary shifts. Pick almost any system or species—glaciers, oceans, birds, insects, fish, even seasons—and there is clear evidence of rapid change and intense stress. The heat-death of coral reefs, shellfish, and spawning salmon is calamitous and devastating, but for most people, it is remote—one more abstract tragedy that is painful to dwell on, and hard to identify with in a visceral way. But something analogous is happening in the world’s forests, where many of us live. Like coral reefs, forests are “metropolitan” organisms: complex, sprawling, slow-growing armatures of life that support thousands of other species from virtually every genus, including ours. For a couple of generations now, we have been told that, in addition to producing much of the oxygen we breathe, forests absorb carbon dioxide and store it, thus helping to modulate Earth’s climate. This is true, but not as true as it used to be. Roughly half the weight of a given tree is composed of stored carbon, which returns to the atmosphere quickly when that tree is burned, and more slowly if the tree rots away in the forest, or in the form of discarded paper, cardboard, or furniture in a landfill.
Since roughly 2000, an inversion has begun: the world’s great terrestrial carbon sinks—the Amazon rain forest and the circumboreal forest, along with many other less famous forest systems around the world—have become net carbon emitters. In other words, what used to be a reliable source of carbon storage is now generating more CO2 than it is sequestering. This grave reversal is one of the most pernicious developments of the Petrocene Age. As forests heat up and die—from disease, beetle infestation, fire, logging, land clearing, and drought, they skew the CO2 balance even further. It is not that living, growing trees don’t continue to absorb carbon, it is that they are no longer keeping pace with the emissions of their sick, dead, and burning neighbors.
Something similar is happening above the tree line in the tundra, and other regions where permafrost is melting. As these environments grow warmer (for the first time since the last glaciation), the frozen, inert organic matter beneath them thaws and then decays, releasing still more CO2. Tundra may be the least charismatic of terrestrial ecosystems, but it possesses hidden depths: there is twice as much carbon dioxide bound up in frozen Arctic soils as is currently in our atmosphere. For the first time since the Ice Age, this process of thaw-and-release is currently under way across the Northern Hemisphere. Vast quantities of methane are trapped in these ice formations as well. In 2020, we saw the greatest annual increase in methane release since systematic measuring began in the 1980s.[*8]
It is impossible to overstate the gravity of these developments or their implications for the future of Earth’s climate, and for the beings who depend on it. For its entire brief history, human civilization has been able to count on the oceans, forests, tundra, and grasslands to offset emissions, whether from volcanic eruptions or our own fires. Then, around 1900, we crossed a threshold. While we have been burning through our vast and ancient fossil fuel inheritance with astonishing speed, we have also been borrowing against the planet’s ability to absorb and process its by-products—carbon dioxide and methane, among many other gases and toxins. Despite decades of repeated, informed warnings, large, for-profit companies, together with their host (and sometimes captive) governments, have persisted in promoting and financing fossil fuels while downplaying the consequences. In so doing, the energy business, in conjunction with elected officials and the wealthiest 10 percent of the population, has mortgaged the atmosphere.[*9] Now, the “bank”—our climate—is collecting on those overdue, overleveraged loans. As Walter “Wally” Broecker, the pioneering climate scientist and early advocate for climate action, said back in 1998, “The climate system is an angry beast, and we are poking it with sticks.”
One of the things so dismaying to people who study and advocate on behalf of our atmosphere is that greenhouse gases aren’t like dust, or ash, or diesel exhaust. They don’t go away or settle out after a few days or months; it’s not like banning cars in Beijing for a couple of weeks and then hosting the Olympics. Once you hit, say, 400 ppm (which we did in 2015), that becomes the new baseline for lifetimes to come. In 2021, we reached 420 ppm, a 50 percent increase over pre-industrial CO2 levels. If you increase anything important by 50 percent—house prices, blood pressure, rat population, rainfall—it will be very noticeable, and often bad.
Currently, we are on pace to re-create—in a couple of centuries—climatic conditions that previously took millions of years to bring about. Such a cataclysmic rate of change will outrun most species’ ability to adapt, and a new equilibrium will be a long time coming. Whatever that new world looks like, it will be a lonelier place, inhabited by a relict fraction of today’s biodiversity. The true impact of the Petrocene Age represents a legitimate Lucretius Problem: no one has been here before, or seen its consequences. No one can truly imagine what this means for life on Earth.