SuperFreakonomics

by Steven D. Levitt

  That said, most current climate models tend to produce similar predictions. This might lead one to reasonably conclude that climate scientists have a pretty good handle on the future.

  Not so, says Wood.

  “Everybody turns their knobs”—that is, adjusts the control parameters and coefficients of their models—“so they aren’t the outlier, because the outlying model is going to have difficulty getting funded.” In other words, the economic reality of research funding, rather than a disinterested and uncoordinated scientific consensus, leads the models to approximately match one another. It isn’t that current climate models should be ignored, Wood says—but, when considering the fate of the planet, one should properly appreciate their limited nature.

  As Wood, Myhrvold, and the other scientists discuss the various conventional wisdoms surrounding global warming, few, if any, survive unscathed.

  The emphasis on carbon dioxide? “Misplaced,” says Wood.

  Why?

  “Because carbon dioxide is not the major greenhouse gas. The major greenhouse gas is water vapor.” But current climate models “do not know how to handle water vapor and various types of clouds. That is the elephant in the corner of this room. I hope we’ll have good numbers on water vapor by 2020 or thereabouts.”

  Myhrvold cites a recent paper asserting that carbon dioxide may have had little to do with recent warming. Instead, all the heavy-particulate pollution we generated in earlier decades seems to have cooled the atmosphere by dimming the sun. That was the global cooling that caught scientists’ attention in the 1970s. The trend began to reverse when we started cleaning up our air.

  “So most of the warming seen over the past few decades,” Myhrvold says, “might actually be due to good environmental stewardship!”

  Not so many years ago, schoolchildren were taught that carbon dioxide is the naturally occurring lifeblood of plants, just as oxygen is ours. Today, children are more likely to think of carbon dioxide as a poison. That’s because the amount of carbon dioxide in the atmosphere has increased substantially over the past one hundred years, from about 280 parts per million to 380.

  But what people don’t know, the IV scientists say, is that the carbon dioxide level some 80 million years ago—back when our mammalian ancestors were evolving—was at least 1,000 parts per million. In fact, that is the concentration of carbon dioxide you regularly breathe if you work in a new energy-efficient office building, for that is the level established by the engineering group that sets standards for heating and ventilation systems.

  So not only is carbon dioxide plainly not poisonous, but changes in carbon-dioxide levels don’t necessarily mirror human activity. Nor does atmospheric carbon dioxide necessarily warm the earth: ice-cap evidence shows that over the past several hundred thousand years, carbon dioxide levels have risen after a rise in temperature, not the other way around.

  Beside Myhrvold sits Ken Caldeira, a soft-spoken man with a boyish face and a halo of curly hair. He runs an ecology lab at Stanford for the Carnegie Institution. Caldeira is among the most respected climate scientists in the world, his research cited approvingly by the most fervent environmentalists. He and a co-author coined the phrase “ocean acidification,” the process by which the seas absorb so much carbon dioxide that corals and other shallow-water organisms are threatened. He also contributes research to the Intergovernmental Panel on Climate Change, which shared the 2007 Nobel Peace Prize with Al Gore for sounding the alarm on global warming. (Yes, Caldeira got a Nobel certificate.)

  If you met Caldeira at a party, you would likely place him in the fervent-environmentalist camp himself. He was a philosophy major in college, for goodness’ sake, and his very name—a variant of caldera, the craterlike rim of a volcano—aligns him with the natural world. In his youth (he is fifty-three now), he was a hard-charging environmental activist and all-around peacenik.

  Caldeira is thoroughly convinced that human activity is responsible for some global warming and is more pessimistic than Myhrvold about how future climate will affect humankind. He believes “we are being incredibly foolish emitting carbon dioxide” as we currently do.

  Yet his research tells him that carbon dioxide is not the right villain in this fight. For starters, as greenhouse gases go, it’s not particularly efficient. “A doubling of carbon dioxide traps less than 2 percent of the outgoing radiation emitted by the earth,” he says. Furthermore, atmospheric carbon dioxide is governed by the law of diminishing returns: each gigaton added to the air has less radiative impact than the previous one.

  Caldeira mentions a study he undertook that considered the impact of higher carbon-dioxide levels on plant life. While plants get their water from the soil, they get their food—carbon dioxide, that is—from the air.

  “Plants pay exceedingly dearly for carbon dioxide,” Lowell Wood jumps in. “A plant has to raise about a hundred times as much water from the soil as it gets carbon dioxide from the air, on a molecule-lost-per-molecule-gained basis. Most plants, especially during the active part of the growing season, are water-stressed. They bleed very seriously to get their food.”

  So an increase in carbon dioxide means that plants require less water to grow. And what happens to productivity?

  Caldeira’s study showed that doubling the amount of carbon dioxide while holding steady all other inputs—water, nutrients, and so forth—yields a 70 percent increase in plant growth, an obvious boon to agricultural productivity.

  “That’s why most commercial hydroponic greenhouses have supplemental carbon dioxide,” Myhrvold says. “And they typically run at 1,400 parts per million.”

  “Twenty thousand years ago,” Caldeira says, “carbon-dioxide levels were lower, sea level was lower—and trees were in a near state of asphyxiation for lack of carbon dioxide. There’s nothing special about today’s carbon-dioxide level, or today’s sea level, or today’s temperature. What damages us are rapid rates of change. Overall, more carbon dioxide is probably a good thing for the biosphere—it’s just that it’s increasing too fast.”

  The gentlemen of IV abound with further examples of global warming memes that are all wrong.

  Rising sea levels, for instance, “aren’t being driven primarily by glaciers melting,” Wood says, no matter how useful that image may be for environmental activists. The truth is far less sexy. “It is driven mostly by water-warming—literally, the thermal expansion of ocean water as it warms up.”

  Sea levels are rising, Wood says—and have been for roughly twelve thousand years, since the end of the last ice age. The oceans are about 425 feet higher today, but the bulk of that rise occurred in the first thousand years. In the past century, the seas have risen less than eight inches.

  As to the future: rather than the catastrophic thirty-foot rise some people have predicted over the next century—good-bye, Florida!—Wood notes that the most authoritative literature on the subject suggests a rise of about one and a half feet by 2100. That’s much less than the twice-daily tidal variation in most coastal locations. “So it’s a little bit difficult,” he says, “to understand what the purported crisis is about.”

  Caldeira, with something of a pained look on his face, mentions a most surprising environmental scourge: trees. Yes, trees. As much as Caldeira personally lives the green life—his Stanford office is cooled by a misting water chamber rather than air-conditioning—his research has found that planting trees in certain locations actually exacerbates warming because comparatively dark leaves absorb more incoming sunlight than, say, grassy plains, sandy deserts, or snow-covered expanses.

  Then there’s this little-discussed fact about global warming: while the drumbeat of doom has grown louder over the past several years, the average global temperature during that time has in fact decreased.

  In the darkened conference room, Myhrvold cues up an overhead slide that summarizes IV’s views of the current slate of proposed global-warming solutions. The slide says:

  Too little

  Too later />
  Too optimistic

  Too little means that typical conservation efforts simply won’t make much of a difference. “If you believe there’s a problem worth solving,” Myhrvold says, “then these solutions won’t be enough to solve it. Wind power and most other alternative energy things are cute, but they don’t scale to a sufficient degree. At this point, wind farms are a government subsidy scheme, fundamentally.” What about the beloved Prius and other low-emission vehicles? “They’re great,” he says, “except that transportation is just not that big of a sector.”

  Also, coal is so cheap that trying to generate electricity without it would be economic suicide, especially for developing countries. Myhrvold argues that cap-and-trade agreements, whereby coal emissions are limited by quota and cost, can’t help much, in part because it is already…

  Too late. The half-life of atmospheric carbon dioxide is roughly one hundred years, and some of it remains in the atmosphere for thousands of years. So even if humankind immediately stopped burning all fossil fuel, the existing carbon dioxide would remain in the atmosphere for several generations. Pretend the United States (and perhaps Europe) miraculously converted overnight and became zero-carbon societies. Then pretend they persuaded China (and perhaps India) to demolish every coal-burning power plant and diesel truck. As far as atmospheric carbon dioxide is concerned, it might not matter all that much. And by the way, that zero-carbon society you were dreamily thinking about is way…

  Too optimistic. “A lot of the things that people say would be a good thing probably aren’t,” Myhrvold says. As an example he points to solar power. “The problem with solar cells is that they’re black, because they are designed to absorb light from the sun. But only about 12 percent gets turned into electricity, and the rest is reradiated as heat—which contributes to global warming.”

  Although a widespread conversion to solar power might seem appealing, the reality is tricky. The energy consumed by building the thousands of new solar plants necessary to replace coal-burning and other power plants would create a huge long-term “warming debt,” as Myhrvold calls it. “Eventually, we’d have a great carbon-free energy infrastructure but only after making emissions and global warming worse every year until we’re done building out the solar plants, which could take thirty to fifty years.”

  This hardly means the energy problem should be dismissed. That’s why IV—along with inventors all over the world—are working toward the holy grail: cheaper and cleaner forms of energy.

  But from an atmospheric perspective, energy represents what might be called the input dilemma. How about the output dilemma? What if the greenhouse gases we’ve already emitted do produce an ecological disaster?

  Myhrvold is not blind to the possibility. He has probably thought about such scenarios in greater scientific detail than any climate doomsayer: a collapse of massive ice sheets in Greenland or Antarctica; a release of huge amounts of methane caused by the melting of arctic permafrost; and, as he describes it, “a breakdown of the thermohaline circulation system in the North Atlantic, which would put an end to the Gulf Stream.”

  So what happens if the doomsayers turn out to be right? What if the earth is becoming dangerously warmer, whether because of our fossil-fuel profligacy or some natural climate cycle? We don’t really want to sit back and stew in our own juices, do we?

  In 1980, when Myhrvold was a grad student at Princeton, Mount St. Helens erupted back home in Washington State. Even though he was nearly three thousand miles away, Myhrvold saw a thin layer of ash accumulating on his windowsill. “It’s hard not to think about volcanic dust when it’s raining down on your dorm room,” he says, “although to be honest, my room was messy in many other ways.”

  Even as a kid, Myhrvold was fascinated by geophysical phenomena—volcanoes, sunspots, and the like—and their history of affecting the climate. The Little Ice Age intrigued him so much that he forced his family to visit the northern tip of Newfoundland, where Leif Eriksson and his Vikings reputedly made camp a thousand years earlier.

  The connection between volcanoes and climate is hardly a new idea. Another polymath, Benjamin Franklin, wrote what seems to be the first scientific paper on the topic. In “Meteorological Imaginations and Conjectures,” published in 1784, Franklin posited that recent volcanic eruptions in Iceland had caused a particularly harsh winter and a cool summer with “constant fog over all Europe, and [a] great part of North America.” In 1815, the gargantuan eruption of Mount Tambora in Indonesia produced “The Year Without a Summer,” a worldwide disaster that killed crops, prompted widespread starvation and food riots, and brought snow to New England as late as June.

  As Myhrvold puts it: “All really big-ass volcanoes have some climate effects.”

  Volcanoes erupt all the time, all over the world, but truly “big-ass” ones are rare. If they weren’t—well, we probably wouldn’t be around to worry about global warming. The anthropologist Stanley Ambrose has argued that a supervolcanic explosion at Lake Toba on Sumatra, roughly seventy thousand years ago, blocked the sun so badly that it triggered an ice age that nearly wiped out Homo sapiens.

  What distinguishes a big-ass volcano isn’t just how much stuff it ejaculates, but where the ejaculate goes. The typical volcano sends sulfur dioxide into the troposphere, the atmospheric layer closest to the earth’s surface. This is similar to what a coal-burning power plant does with its sulfur emissions. In both cases, the gas stays in the sky only a week or so before falling back to the ground as acid rain, generally within a few hundred miles of its origin.

  But a big volcano shoots sulfur dioxide far higher, into the stratosphere. That’s the layer that begins at about seven miles above the earth’s surface, or six miles at the poles. Above that threshold altitude, there is a drastic change in a variety of atmospheric phenomena. The sulfur dioxide, rather than quickly returning to the earth’s surface, absorbs stratospheric water vapor and forms an aerosol cloud that circulates rapidly, blanketing most of the globe. In the stratosphere, sulfur dioxide can linger for a year or more, and will thereby affect the global climate.

  That’s what happened in 1991 when Mount Pinatubo erupted in the Philippines. Pinatubo made Mount St. Helens look like a hiccup; it put more sulfur dioxide into the stratosphere than any volcano since Krakatoa, more than a century earlier. In the period between those two eruptions, the state of science had progressed considerably. A worldwide cadre of scientists was on watch at Pinatubo, equipped with modern technology to capture every measurable piece of data. The atmospheric aftereffects of Pinatubo were undeniable: a decrease in ozone, more diffuse sunlight, and, yes, a sustained drop in global temperature.

  Nathan Myhrvold was working at Microsoft then, but he still followed the scientific literature on geophysical phenomena. He took note of the Pinatubo climate effects and, one year later, a 900-page report from the National Academy of Sciences called Policy Implications of Greenhouse Warming. It included a chapter on geoengineering, which the NAS defined as “large-scale engineering of our environment in order to combat or counteract the effects of changes in atmospheric chemistry.”

  In other words: if human activity is warming up the planet, could human ingenuity cool it down?

  People have been trying to manipulate the weather forever. Just about every religion ever invented has a rain-making prayer. But secularists have stepped it up in recent decades. In the late 1940s, three General Electric scientists in Schenectady, New York, successfully seeded clouds with silver iodide. The trio included a chemist named Bernard Vonnegut; the project’s public-relations man was his younger brother Kurt, who went on to become a world-class novelist—and in his writing, he used a good bit of the far-out science he picked up in Schenectady.

  The 1992 NAS report gave a credibility boost to geoengineering, which until then had largely been seen as the province of crackpots and rogue governments. Still, some of the NAS proposals would have seemed outlandish even in a Vonnegut novel. A “multiple balloon screen,” for insta
nce, was meant to deflect sunlight by launching billions of aluminized balloons into the sky. A “space mirror” scheme called for fifty-five thousand reflective sails to orbit high above the earth.

  The NAS report also raised the possibility of intentionally spreading sulfur dioxide in the stratosphere. The idea was attributed to a Belarusian climate scientist named Mikhail Budyko. After Pinatubo, there was no doubt that stratospheric sulfur dioxide cooled the earth. But wouldn’t it be nice to not have to rely on volcanoes to do the job?

  Unfortunately, the proposals for getting sulfur dioxide into the stratosphere were complex, costly, and impractical. Loading up artillery shells, for instance, and firing them into the sky. Or launching a fleet of fighter jets with high-sulfur fuel and letting their exhaust paint the stratosphere. “It was more science fiction than science,” says Myhrvold. “None of the plans made any economic or practical sense.”

  The other problem was that many scientists, particularly nature-friendly ones like Ken Caldeira, found the very idea abhorrent. Dump chemicals in the atmosphere to reverse the damage caused by…dumping chemicals in the atmosphere? It was a crazy, hair-of-the-dog scheme that seemed to violate every tenet of environmentalism. Those who saw global warming as a religious issue could hardly imagine a more grievous sacrilege.

  But the best reason to reject the idea, Caldeira thought, was that it simply wouldn’t work.

  That was his conclusion after hearing Lowell Wood give a lecture on stratospheric sulfur dioxide at a 1998 climate conference in Aspen. But being a scientist who prefers data to dogma—even if the environmental dogma in this case lay close to his heart—Caldeira ran a climate model to test Wood’s claims. “The intent,” he says, “was to put an end to all the geoengineering talk.”

  He failed. As much as Caldeira disliked the concept, his model backed up Wood’s claims that geoengineering could stabilize the climate even in the face of a large spike in atmospheric carbon dioxide, and he wrote a paper saying so. Caldeira, the most reluctant geoengineer imaginable, became a convert—willing, at least, to explore the idea.