Some economists argue that these figures are exaggerated; indeed, I have cited the researchers’ worst-case scenarios, to emphasize the stakes. But the same economists also point out that some of the most threatened areas are irreplaceable parts of the world’s cultural and natural patrimony. Venice is an obvious example, but so are places like central London, New Orleans and the Mississippi Delta, the vast ancient complex of Chan Chan in coastal Peru, and the great Sundarbans mangrove forests in India and Bangladesh.
To avoid this damage, cities would either have to shift their population to higher ground, construct networks of protective baffles, canals, dikes, and floodwalls, or both. All would be difficult and costly. Shanghai, with an average altitude of thirteen feet, is among the many Asian cities vulnerable to rising waters. Its 14.35 million inhabitants live on the low, flat delta of the Yangzi River. Because the city has withdrawn groundwater too rapidly, it has sunk more than nine feet in the last century. Meanwhile, sea levels are rising. In 1993 the city built a floodwall designed to block the surge from a once-in-a-thousand-years storm; within four years stormwater was lapping at its top. The nearest higher land is about thirty miles away, in the outskirts of the city of Hangzhou, population 2.45 million. Relocating part of Shanghai there would involve building a second or third Hangzhou atop the first.
Cities have adapted to rising waters in days gone by. Chicago, founded almost at the water level of Lake Michigan and the Chicago River, discovered that its land was too flat, low, and wet to install a sewer system. Beginning in 1856, the city installed six-foot sewage pipes in the middle of its streets, then raised the buildings around them. Some structures were jacked up as much as ten feet. Eventually the entire city was lifted into the air. In our era Venice has constructed lines of floodwalls around itself. The system began construction in 2003 and is intended to be operational in 2019.
These cities were small enough to make one wonder about their use as precedents. Chicago then had about 100,000 inhabitants; Venice and its surrounding communities have about 265,000. No one knows how much Chicago spent; Venice’s defenses will cost $6.1 billion to construct, about $23,000 for every man, woman, and child in the area. Many of the at-risk cities are much bigger, especially those in Asia: Bangkok, Tianjin, Manila, Guangzhou, Jakarta, Taipei, Mumbai, Dhaka, Kolkata, Ho Chi Minh City. One report suggests that by the year 2100 a hundred-year storm in Southeast Asia could flood out 362 million men, women, and children. Protecting people in such numbers would be an unprecedented task.
What if Vaclav Smil is right, and the world’s energy system cannot be remade fast enough to avoid flooded cities? Suppose that Smil’s scenario has come to pass by 2050—our civilization has cut the amount of carbon it sends into the air, but not by enough. Suppose further that climate sensitivity has turned out to be on the high side. In this scenario we are racing toward an increase in global temperatures of 7°F, perhaps even 9°F. (Nothing known today rules this out.) What to do? The waters are lapping higher.
Tomorrow’s leaders, whether Wizards or Prophets, would face a dance of impossibilities: the extraordinary cost and effort of rapidly replacing the world’s energy infrastructure versus the extraordinary cost and effort of moving cities versus the extraordinary cost and effort of continuing on the same path. Facing this dizzying choice, who wouldn’t look for an escape hatch? To save the future, some would look at the past. Two pasts, in fact—one preferred by Wizards, the other by Prophets.
The first past goes back to Mount Pinatubo, a volcanic eruption in the Philippines in 1991. The explosion killed several hundred people, covered several thousand square miles in debris, and shot gas, dust, and ash into the stratosphere. That plume of volcanic pollution contained at least 20 million tons of sulfur dioxide, a pungent, toxic gas. Water vapor in the stratosphere combined with Pinatubo’s sulfur dioxide, producing shiny, microscopic droplets of sulfuric acid. Taken together, the journalist Oliver Morton has calculated, these aerosols had a surface area similar to that “of a large desert—definitely bigger than the Mojave, likely smaller than the Sahara.” Like a diffuse, airborne desert of blazing white sand, the field of sulfuric acid droplets reflected sunlight into space. For two years the amount of sunlight that reached the surface dropped by more than 10 percent. Average global temperatures fell by about 1°F.
Mount Pinatubo, June 12, 1991. Geoengineering advocates argue that buying time to stave off the worst effects of climate change could begin by pumping the rough equivalent of a Pinatubo per year into the upper atmosphere. Credit 74
To Wizards, numbers like these are an irresistible excuse for performing some elementary arithmetic. Keeling’s carbon dioxide measurements tell us that the air today contains a bit over 400 parts per million of carbon dioxide. Each part per million is equivalent to 7.8 billion tons of carbon dioxide. Four hundred parts per million times 7.8 billion comes to 3.1 trillion tons of airborne carbon dioxide. In 1880, before people began burning coal in large quantities, the carbon dioxide level was about 280 parts per million. Doing the same kind of multiplication, that is equivalent to 2.19 trillion tons of carbon dioxide in the air. Subtracting the pre-industrial number from today’s number leads to the conclusion that our antic consumption of fossil fuels has added 0.91 trillion tons of carbon dioxide to the atmosphere. Call the number 1 trillion, for simplicity’s sake. The result of that post-Pithole trillion has been to raise global temperatures by about 1.4°F (0.8°C), with most of that warming since 1975. A bit more back-of-the-envelope arithmetic: 650 billion tons of carbon dioxide is, roughly speaking, equivalent to 1°F of warming.
Pinatubo offset that 1°F of warming with about 20 million tons of sulfur dioxide. Doing the arithmetic again, sulfur dioxide is, molecule by molecule, more than thirty thousand times more effective at lowering temperatures than carbon dioxide is at raising them.
Actually, this understates the comparison. Here Wizardly attention shifts from arithmetic to the science of raindrops. One ton of water in a single round blob has a surface area of roughly fifty feet. Divide that same ton of water into droplets a few ten-thousandths of an inch in diameter. The volume of water remains the same, but the surface area increases—to more than two square miles. Cut each of these little droplets into five identical but even smaller pieces. Now the surface area is about ten square miles—ten square miles of thinly spread mirror. (I have lifted this calculation from Morton’s fine book The Planet Remade [2016].) The smaller the droplets, the bigger the mirror; the bigger the mirror, the more the reflection. Equally important, the droplets must be separated by enough space so that they don’t bump into each other and merge into big droplets, which fall out of the sky faster than small ones.
The cooling from Pinatubo’s 20 million tons of sulfur dioxide was geophysical happenstance; the droplets it formed were not of the optimal size. By making smaller, more effective droplets, geoengineers could achieve the same reduction by spraying just a few million tons of sulfur dioxide into the air in a year. Actually, they would probably spray sulfuric acid directly, rather than having the atmosphere convert sulfur dioxide, but the principle is the same. The most direct method to accomplish this task would be to launch specialized delivery vehicles from Earth, each with a payload of sulfuric acid.
Services already perform such tasks. They are called commercial airlines. A new Boeing 747 carries as many as 600 passengers. The average weight of a U.S. person is about 175 pounds. To make figuring easy, assume that each 175-pound passenger has 25 pounds of luggage and thus represents a unit of 200 pounds. Each 600-person flight on a 747 thus carries 120,000 pounds—60 tons—of human weight. To send aloft 2 or 3 million tons would require flying about a hundred or so flights a day. Today the world’s airlines fly more than 100,000 flights a day. Ryanair, an Irish budget airline, operates 1,800 flights a day; Alaska Air, a regional U.S. airline, has almost 900. Recreating Pinatubo would require a service about a tenth the size of Ryanair or possibly a fifth of Alaska Air.
For better or worse, a fifth of
an Alaska Air would not be expensive. One well-known estimate from 2012 suggested that fourteen big cargo aircraft—Boeing 747s, for example—could pull a Pinatubo for a little more than $1 billion a year. But commercial jets are not designed to fly into the stratosphere (the higher one places the sulfur, the longer it will stay aloft). Specially designed planes could be more effective and cost only $2 to $3 billion a year to operate. Either way, it is financially feasible. The cost for a decade of counteracting most of the impact of carbon dioxide, the Harvard physicist David Keith has written, “could be less than the $6 billion the Italian government is spending on dikes and movable barriers to protect a single city, Venice, from climate-change-related sea level rise.”
To governments looking at rising seas, experiments with sulfur dioxide could seem worth the risk. Should carbon emissions not fall quickly enough, the idea goes, the world might dump sulfuric acid into the air for a couple of decades, buying enough time to finish the transition from fossil fuels. In theory, the injections could be focused on the skies above the poles, creating a reflective shield over the Arctic and Antarctic ice sheets. The goal would not be to eliminate all global warming, but to take the edge off, reducing it by a fifth or a fourth until it reaches the relatively safe level of 3°–4°F.
Since the 1980s such plans to alter Earth’s climate deliberately have been called “geoengineering.” Geoengineering fights climate change with more climate change. It is, in the jargon, a “technical fix.” It replaces the idea of staying within natural limits with the goal of creating a balance on terms set by humankind. It is an audacious promise to fix the sky. It is one of the logical endpoints of the Wizards’ dream of human empowerment and grandeur.
Geoengineering is an ancient idea with some old baggage. Ancient religions promised for millennia to control the weather by negotiating with heavenly powers. When the rise of science downgraded the role of priestly intercession, lunatics, imposters, and bunco artists filled the vacuum. Flotillas of phony rainmakers traveled through the nineteenth-century Middle West, taking advantage of drought fears to sell mysterious engines, bottles of vile, foamy liquids, and pamphlets filled with scientific-sounding gabble to credulous farmers. On the West Coast, Charles Mallory Hatfield, the self-proclaimed Moisture Accelerator, spent years building towers in remote locations from which he evaporated pans of chemicals. The chemicals, Hatfield claimed, used a “subtle attraction” to “woo” rain clouds. When the director of the U.S. Weather Bureau denounced Hatfield as a fake in 1905, he shrugged it off. “Censure and ridicule are the first tributes paid to scientific enlightenment by prejudiced ignorance,” he said.
Perhaps the most energetic charlatan was Robert St. George Dyrenforth. An engineer, patent lawyer, and Civil War major, Dyrenforth was certain that rain was caused by thunder. In federally funded tests in West Texas in 1891, Dyrenforth and a cohort of rain-obsessed amateurs tried to simulate peals of thunder by taping explosives to balloons and kites, filling prairie-dog holes with gunpowder, emplacing ranks of improvised mortars (the barrels were sawed-off iron tubes), and festooning mesquite bushes with sticks of dynamite. All were rigged to go off at the same time. Rain fell heavily before the experiments and continued afterward. Dyrenforth reported this as proof of success and asked Congress for more money.
Legitimate experiments in “cloud seeding”—sprinkling tiny crystals of dry ice in clouds, to stimulate raindrop formation—began in the 1940s. They effectively ended the reign of the con artists, but gave rise to another breed of fraud, the overly optimistic intellectual. Promising that “[w]e will change the Earth’s surface to suit us,” the physicist Edward Teller proposed that atom bombs be used to shake loose recalcitrant petroleum deposits, create a second Panama Canal, and manipulate weather patterns. The most wild-eyed schemes came from Moscow, where Soviet dreamers unfurled one grandiose, loopy stratagem after another. Melting Arctic ice by bombing it with soot. Building a causeway off Newfoundland to redirect the Gulf Stream. Damming the Congo River to irrigate the Sahara. Pumping warm water from the Japanese Current into the Arctic Ocean, shrinking the ice cap. Launching thousands of rockets full of potassium dust to create Saturn-like rings around Earth that would somehow induce a “perpetual summer.”
From these brainstorms came proposals to offset climate change from carbon dioxide—toss-offs at first, then more serious suggestions. In the late 1950s John von Neumann half-seriously proposed creating a planet-wide dust shroud with nuclear weapons; the haze would cool Earth, which he suspected humans were overheating with power plants and blast furnaces. Less enamored of bombs, Roger Revelle in 1965 suggested scattering millions of little floating mirrors on the sea to reflect sunlight into space. Few paid attention at the time. But in 2006, when the Nobel Prize–winning chemist Paul Crutzen resurrected the idea of geoengineering, people were ready to listen, however reluctantly.
Gone were the days of Soviet-style gusto; Crutzen’s tone was anything but triumphant. “The very best would be if emissions of the [climate-changing] gases could be reduced so much the stratospheric sulfur release experiment would not need to take place,” he wrote at the end of his article. “Currently, this looks like a pious wish.” Other Wizards have echoed his tone. Geoengineering might be the culmination of Borlaugian dreams of power and control, but its advocates have drawn back, chastened, from the implications; their support for geoengineering is mixed with regret. A prominent geoengineering advocate, the Harvard physicist David Keith, has likened it to chemotherapy for the planet—a treatment that nobody would want to have unless forced by circumstance, because it deliberately makes the patient sick to cure a greater disease. Tinkering with the atmosphere, in the phrase of the writer Eli Kintisch, may be a bad idea whose time has come.
The potential pitfalls are many. Sulfur compounds would interact with stratospheric ozone, which protects surface-dwellers like us from the sun’s dangerous ultraviolet radiation. The sulfur soon falls to the earth, contributing to lethal air pollution. (For this reason, some have suggested using particles of titanium, aluminum oxide, or calcite, which are more expensive but less likely to interact with ozone and unable to form acid.) In reflecting sunlight, sulfuric acid droplets in the stratosphere reduce the amount of energy coming into the atmospheric layers below, which affects wind and rainfall. Because wind currents are unevenly distributed around Earth, the changes in rainfall will be unevenly distributed, and temperatures along with them. Geoengineering may reduce temperatures globally, but there will still be local losers and winners—places that experience too much or too little rainfall, places subject to sudden temperature extremes. And no matter how much sulfur dioxide humankind throws into the heavens, the carbon dioxide will remain; to counteract the ever-increasing total, more sulfur must be launched into the air every year. Indeed, stopping it suddenly would be disastrous; all the hidden-away warming would emerge in a few months.
The greatest danger posed by planet-hacking comes from its greatest virtue: its low cost. Wagner and Weitzman, the economists, call it a “free-driver” problem; driving the car is so cheap, anyone can take it for a spin. Spraying sulfur is cheap and easy enough that a single rogue nation could reengineer the planet by itself. Or two countries could separately decide to alter the climate in conflicting ways. China, worried about drought, could seek to increase its monsoon; India, fearful of flooding, could try to decrease rainfall. “Both are nuclear weapons states,” Keith reminds us. According to Forbes magazine, the world has 1,600 billionaires. Each could sponsor a course of geoengineering single-handedly. A Bill Gates could pay for it many times over by himself. “A lone Greenfinger, self-appointed protector of the planet and working with a small fraction of the Gates bank account, could force a lot of geoengineering on his own,” remarked the Stanford international-relations specialist David Victor.
Strange Forests
Prophets go on tilt when they hear these ideas. Viewing climate change as a prime example of exceeding carrying capacity, they regard the idea of fighting
pollution with pollution as marching precisely in the wrong direction. Not only is it crazy to begin with, Vogtians say, it’s a distraction from the urgent social reforms needed for the future. Worse, geoengineering forever desacralizes Nature; it puts the final seal on the replacement of the authentic, billion-year-old natural world by a new, artificial world whose every surface bears the greasy human fingerprint. But the specter of drought, flooded cities, and ruined ecosystems is so imminent that some Prophets have begun thinking, however anxiously, about their own form of geoengineering. Like Wizard-style geoengineering, it is animated by a vision of the past. In the Prophets’ case, though, the past is ancient: the end of the Carboniferous epoch.
Diverse plant and animal life has existed for about 550 million years. For almost all of that time, carbon dioxide levels have been high—sometimes twenty times higher than they are now—and the world was, by today’s standards, unbearably hot. Only twice during this period has the world experienced prolonged periods of lower temperatures: our own epoch—more exactly, the last 50 million years—and the end of the Carboniferous. The Carboniferous, one recalls, was the period in which large land plants emerged: lepidodendrons, horsetails, giant ferns, and a host of other now-vanished species. Forests grew in such proliferation that they sucked huge amounts of carbon from the air. Average temperatures fell from 75°–85°F to something like 50°F, lower than today’s average of 55°–60°F—low enough to set off not one but two ice ages, killing huge numbers of plants and setting in motion the creation of coal.