These approaches have one thing in common: They’re more difficult than simply burning fossil fuel. They force us to realize that we’ve already had our magic fuel and that what comes next will be more expensive and more difficult. The price tag for the global transition will be in the trillions of dollars. Of course, along the way it will create myriad new jobs, and when it’s complete, it may be a much more elegant system. (Once you’ve built the windmill, the wind is free; you don’t need to guard it against terrorists or build a massive army to control the countries from which it blows.) And since we’re wasting so much energy now, some of the first tasks would be relatively easy. If we replaced every incandescent bulb that burned out in the next decade anyplace in the world with a compact fluorescent, we’d make an impressive start on one of the 15 wedges. But in that same decade we’d need to build 400,000 large wind turbines-clearly possible, but only with real commitment. We’d need to follow the lead of Germany and Japan and seriously subsidize rooftop solar panels; we’d need to get most of the world’s farmers plowing their fields less, to build back the carbon their soils have lost. We’d need to do everything all at once. </p>
<p>As precedents for such collective effort, people sometimes point to the Manhattan Project to build a nuclear weapon or the Apollo Program to put a man on the moon. But those analogies don’t really work. They demanded the intense concentration of money and intelligence on a single small niche in our technosphere. Now we need almost the opposite: a commitment to take what we already know how to do and somehow spread it into every corner of our economies, and indeed our most basic activities. It’s as if NASA’s goal had been to put all of us on the moon. </p>
<p>Not all the answers are technological, of course-maybe not even most of them. Many of the paths to stabilization run straight through our daily lives, and in every case they will demand difficult changes. Air travel is one of the fastest growing sources of carbon emissions around the world, for instance, but even many of us who are noble about changing lightbulbs and happy to drive hybrid cars chafe at the thought of not jetting around the country or the world. By now we’re used to ordering take-out food from every corner of the world every night of our lives-according to one study, the average bite of food has traveled nearly 1,500 miles (2,414 kilometers) before it reaches an American’s lips, which means it’s been marinated in (crude) oil. We drive alone, because it’s more convenient than adjusting our schedules for public transit. We build ever bigger homes even as our family sizes shrink, and we watch ever bigger TVs, and-well, enough said. We need to figure out how to change those habits. </p>
<p>Probably the only way that will happen is if fossil fuel costs us considerably more. All the schemes to cut carbon emissions-the so-called cap-and-trade systems, for instance, that would let businesses bid for permission to emit-are ways to make coal and gas and oil progressively more expensive, and thus to change the direction in which economic gravity pulls when it applies to energy. If what we paid for a gallon of gas reflected even a portion of its huge environmental cost, we’d be driving small cars to the train station, just like the Europeans. And we’d be riding bikes when the sun shone. </p>
<p>The most straightforward way to raise the price would be a tax on carbon. But that’s not easy. Since everyone needs to use fuel, it would be regressive-you’d have to figure out how to keep from hurting poor people unduly. And we’d need to be grown-up enough to have a real conversation about taxes-say, about switching away from taxes on things we like (employment) to taxes on things we hate (global warming). That may be too much to ask for-but if it is, then what chance is there we’ll be able to take on the even more difficult task of persuading the Chinese, the Indians, and all who are lined up behind them to forgo a coal-powered future in favor of something more manageable? We know it’s possible-earlier this year a UN panel estimated that the total cost for the energy transition, once all the pluses and minuses were netted out, would be just over 0.1 percent of the world’s economy each year for the next quarter century. A small price to pay.</p>
<p>In the end, global warming presents the greatest test we humans have yet faced. Are we ready to change, in dramatic and prolonged ways, in order to offer a workable future to subsequent generations and diverse forms of life? If we are, new technologies and new habits offer some promise. But only if we move quickly and decisively-and with a maturity we’ve rarely shown as a society or a species. It’s our coming-of-age moment, and there are no certainties or guarantees. Only a window of possibility, closing fast but still ajar enough to let in some hope.