…Over the past year, the debate over nuclear power has increasingly been framed as an environmental one, as several commentators … have stepped forward to assert that global warming requires an embrace of new nuclear plants, because unlike gas- or coal-powered plants, nuclear reactors produce electricity without emitting greenhouse gasses.

The nuclear industry, in turn, has capitalized on the chance to adopt a green tinge, or at least greenish one; among its recent slogans is the exhortation to “Go nuclear: because you care about the air.” Most environmental groups have not softened their opposition, however. “This is more a propaganda exercise than a serious discussion of the viability of the industry,” Jim Riccio, the nuclear policy analyst at Greenpeace, told me. By using global warming, he added, “the nuclear industry is trying to find some fear greater than the nuclear fear to be their selling point.”

Nonetheless, whether any new nuclear plants are built in the United States depends less on the sentiments of the American public than on the country’s individual utilities. And for conglomerates like the Southern Company, which runs Vogtle as well as two other nuclear plants in Georgia and Alabama, the determining factor is not air quality. It’s money. Over the next 12 to 24 months, as utilities like Southern determine what to do, their fundamental concern is the bottom-line cost. And the feeling among many in the industry is that the financial prospects are almost certainly looking up.

… the industry, in a way, is in a race against time. Recently, Paul Joskow, a professor of economics at M.I.T., sent me a chart that looks ahead to the output of America’s reactors over the next half-century. As the current 103 nuclear reactors continue to generate electricity for the next few decades, the line on the chart remains mostly flat. But then the plants’ electricity production falls off a cliff. “I think this is the first time in many years, perhaps 20 years, that the combination of government policy, economic conditions and environmental constraints are reasonably favorable for nuclear,” Joskow told me. “If they can’t move forward now, it would be very difficult in the longer run.” It may even be more urgent than that. One conclusion to be derived from the chart is that nuclear power in this country is dying. Unless someone starts building soon, it will begin to disappear in 15 or 20 years, as one plant after another exhausts its operating permit and goes dark. And it will effectively be extinguished as an energy source by around 2050.

For those with deep misgivings about the safety and expense of nuclear plants, life without them may indeed be a cause for celebration. Yet their absence would probably pose tremendous challenges for the United States. The first is where 20 percent of our power would come from; the second is whether a substitute fuel for that power would emit carbon dioxide. It is, in many ways, a long-term dilemma, one closely related to global warming, and one that is poorly suited to a society that focuses on short-term results.

…to spend a few months listening to those who study the earth’s energy resources is to get the feeling that we are in for a very difficult century — and one that depends on an immediate future of difficult and unpleasant choices. “If you want a different energy system in 2050, you really have to start changing it now,” says John Holdren, a Harvard professor and one of the country’s most esteemed thinkers on energy and the environment. “You can’t get there and say, ‘Oh, I want a different energy system.’ ”

Pick Your Poison

When it comes to America’s future energy needs, one of the larger points of confusion is the somewhat tangled relationship between fossil fuels and electricity. Current prices at the gas pump, for instance, or the possibility that we are approaching a moment of “peak oil” — the point at which the global supply of crude peaks and then diminishes forever, with cataclysmic consequences for transportation, trucking and the economy in general — actually have little to do with the future supply of power. Making electricity is generally about creating a source of heat and steam, and using that steam to turn giant turbines and generate power. Less than 3 percent of our electric power is generated from oil. Besides the 20 percent contribution from nuclear power, 50 percent of our electricity comes from burning coal, 18 percent from burning natural gas and (in a heat-free method that is often the cheapest) 6.5 percent by harnessing the energy of water moving through dams. Wind and solar power make up less than one-half of 1 percent of what we use on a typical day.

… what makes the choice of fuels such a knotty problem is that something that is cheap now, like coal, may not be so cheap in 10 years. This isn’t because we’re running out; we probably have at least a century’s worth of coal reserves in the United States alone. But if the government were to impose a tax or a cap on carbon emissions, something that almost everyone I spoke with in the energy industry believes is inevitable, or if new laws mandate that coal plants must adopt more expensive technologies to burn the coal cleaner — or to “sequester” the carbon-dioxide byproducts underground — the financial equation will change: a kilowatt-hour generated by coal suddenly becomes more expensive. There are other contingencies at play, too: fuels, like natural gas, could experience a supply interruption that leads to enormous price spikes. As for the hope that wind and solar power will generate large amounts of clean, affordable electricity in the near future? I encountered great skepticism inside and outside the utility companies. “Maybe in 40 years,” Paul Joskow, of M.I.T., told me.

Meanwhile, nuclear power has several appealing factors: the cost of uranium is fairly low, the supply is abundant (and mostly found in countries friendly to the United States) and big plants like Vogtle can generate large amounts of inexpensive electricity. …. On the other hand, the list of negatives is long…

The most immediate challenges, at least for the utilities, are the capital costs of building new plants…

There is a counterargument to building large new power plants. One view — voiced most forcefully, perhaps, by Amory Lovins, a physicist who runs Rocky Mountain Institute, which advises corporations and utilities on energy efficiency — is that we don’t need to increase our electrical supply. We need to decrease demand by rewarding utilities for getting customers to reduce electricity use by, say, updating their appliances, furnaces and lighting. ….

When I asked John Holdren at Harvard whether the potential for efficiencies is as large as Lovins says, he replied, “The savings could be huge.” Yet Holdren also maintains that creating a clean and reliable energy supply for the future is going to be so daunting that nothing should be taken off the table. Clean coal, renewables, nuclear — we’ll need them all. To those in the electricity business, this is known as creating an energy portfolio: build everything, use everything and rely on nothing exclusively. “I’ll be very happy if Amory’s right,” Holdren added, “but I’d like to hedge my bets.”

… The [current] so-called renaissance [of nuclear power] may turn out to be just a brief flurry of enthusiasm, entailing the construction of a few new plants over the next decade. But if nuclear power does catch on again — and there are a number of reasons to think it might, the most obvious being strong government encouragement driven by the attitude that a portfolio of energy options creates a more stable economy — then the seeds of its revival would almost certainly date back to the late 1980’s and early 1990’s.

…No two factors have been quite so important to the revived prospects for nuclear power as the high price of natural gas and large incentives offered by the Department of Energy, amounting to several hundred million dollars, to help finance the first few reactors. But there have been a great number of helpful factors inside the industry too….

A Different Sort of Wedge Issue

To John Holdren of Harvard, the essential problem with nuclear power is that it is “too unforgiving of either human error or human malice.” At the same time, Holdren points out, every source of electricity has its negatives. In the case of oil and gas, the question is whether there are enough reserves. For other fossil fuels like coal and tar sands, the question is whether our atmosphere can tolerate the emissions. For ethanol, the question is whether there is enough land to grow the necessary crops. For wind and hydropower, the question is whether there are enough good sites. Enough sunlight hits the planet to power civilization 2,000 times over, Holdren says, but solar power from photovoltaic cells is too expensive. “I can design a world that runs on photovoltaics,” he says, “but at current costs, electricity would be three or four times what it costs today.” That would wreak havoc on the world economy.

What complicates things further is the specter of great climate changes. This month, Jim Hansen, a NASA scientist, declared that we have, at most, 10 years to alter the trajectory of global greenhouse emissions. Holdren, similarly, says he believes that the problems from global warming could become so acute so quickly — as in a few years, rather than a few decades — that there really isn’t much time to decide which way to go.

Among the most influential ideas these days about how to change the system are those from the research of two Princeton professors, Stephen Pacala and Robert Socolow, who wrote an academic paper in 2004 on what they called “stabilization wedges.” It is an encouraging document, in that it presents a manageable way to think about how to address global warming — basically, to approach it on many fronts simultaneously — without suggesting we need one big, magical fix. Pacala and Socolow looked at what we can do now, using current technologies, and barring any sort of startling new scientific developments, to freeze carbon dioxide production and thus slow down global warming. They assert that we could reduce carbon emissions incrementally. In pursuing one of these “wedges,” we would reduce carbon emissions slightly; but in pursuing all of them, we could succeed in flatlining the growth of carbon emissions entirely by the century’s midpoint.

There are 15 different wedges. These include increasing vehicle efficiency, reforestation, improving the efficiency of buildings, capturing carbon in power plants, replacing some coal power with wind power and replacing some coal power with solar power. Nuclear power is a wedge, too. It is curious, though perhaps unsurprising, that to various advocates some wedges have proved more appealing than others: supporters of nuclear power, for instance, stressed its environmental wedge potential to me while playing down the viability of wind and solar power. The opposite is true as well. In the film “An Inconvenient Truth,” Al Gore refers to the Pacala and Socolow research, citing several wedges, but not the nuclear one. He stresses renewable energies.

To consider nuclear energy in the environmental framework, though, may be the same as asking whether the utilities that pursue new plants might be giving us a valuable wedge. Because without the environmental contribution from new nuclear plants, we may need to find a wedge somewhere else. And ultimately, the essential, agonizingly difficult question of nuclear power is not whether it’s good or bad, or whether it’s worse than wind and better than coal, but whether we will have a better future with or without it. “By 2015, I think everyone in the world will be convinced that our interventions in climate are going to be intolerable,” Holdren says. “I’m often asked, ‘Can you solve the climate problem without nuclear energy?’ And I say, ‘Yes, you can solve it without nuclear energy.’ But it will be easier to solve it with nuclear energy.” …

Jon Gertner, a contributing writer for the magazine, last wrote about student-loan forgiveness.