Good, I was sitting around waiting for my chance to play the unreasonable environmentalist. And lo, Patrick Moore writes in the Washington Post over the weekend that the U.S. needs to start ramping up production of nuclear power plants if we ever want to reduce carbon emissions. And he's certainly not going to let a bunch of tree-hugging Naderites get in the way:

When I attended the Kyoto climate meeting in Montreal last December, I spoke to a packed house on the question of a sustainable energy future. I argued that the only way to reduce fossil fuel emissions from electrical production is through an aggressive program of renewable energy sources (hydroelectric, geothermal heat pumps, wind, etc.) plus nuclear.

….Here's why: Wind and solar power have their place, but because they are intermittent and unpredictable they simply can't replace big baseload plants such as coal, nuclear and hydroelectric. Natural gas, a fossil fuel, is too expensive already, and its price is too volatile to risk building big baseload plants. Given that hydroelectric resources are built pretty much to capacity, nuclear is, by elimination, the only viable substitute for coal. It's that simple.

Well, that's nice. But I want numbers first. How many power plants are we talking about? In 2004, Stephen Pascala and Robert Socolow argued in a much-discussed Science article that the world's carbon output will rise from about 7 billion tons today to 14 billion tons in 2054. In order to keep carbon concentrations under 500 ppm by mid-century, and avoid bad global warming scenarios, the world should be emitting only 7 billion tons of carbon by 2050.

Now in order to replace one billion tons of those emissions with nuclear energy, Pascala and Socolow estimate that the world would have to add an additional 700 GW in nuclear capacity, double what's produced at present by 440 reactors. So that means 880 new reactors, unless technology makes our plants much more efficient and the like. Since the United States is responsible for roughly a fourth of all carbon output, we'll say that the U.S. would need to build around 220 new nuclear reactors by 2050. Just to cut future emissions by a seventh.

(Keep in mind, too, that Pascala and Socolow are using only one set estimates of the carbon impact of nuclear power. That's totally valid, but opinions do differ. The Chartered Institution of Water and Environmental Management in Britain, for instance, estimates that the total carbon footprint of nuclear power, once you factor in extraction, decommissioning, and waste storage, could be much greater than once believed. There's also a question of whether there's enough uranium in the dirt to power all those new plants; granted, that problem could be solved by building fast-breeder reactors, but those have serious proliferation issues.)

How much would all those new reactors cost? A nuclear power plant currently being proposed in Calvert County, near Washington D.C., is estimated to cost $2.6 billion—and that's likely a low estimate (this new plant in South Carolina will cost "$4 to $6 billion"). The Department of Energy is chipping in $300 million for licensing costs, but critics already fear that the federal government will be forced to pick up cost overruns down the road. During debates over the energy bill, pro-nuclear Senators like Pete Domenici were proposing subsidies to pay for half of all nuclear construction costs, since private investors shy away from building reactors. A rough guess is that helping to fund 220 reactors would cost taxpayers $300-500 billion or more, at minimum. And that's not counting security and the like.

Now fine, if that's what it takes to avert global warming, that's what it takes. But there's also a question of opportunity costs. Every dollar spent building nuclear reactors is a dollar not spent funding other renewable energy sources. And that might be a poor trade-off. I'll quote British journalist Hannah Bullock:

The [British] government has done its sums and reckons that, by 2020 – the earliest time a new nuclear programme could come on stream – it’ll be cheaper to cut a tonne of carbon dioxide emissions through wind or combined heat and power (CHP) technologies – or simply through energy efficiency. These greener options could even have a negative net cost, the Performance and Innovation Unit (PIU) worked out. But if an expensive new nuclear build programme draws investment away from the development of clean technologies like these, we could see higher, rather than lower, emissions in the medium term.

I don't know exactly what study Bullock's talking about here, but it's something to consider. The choice isn't just between building new nuclear reactors or keeping all our carbon-spewing coal plants in place, which is what David Roberts is getting at here.

At any rate, I wouldn't rule out nuclear power completely, but everything I've seen indicates that it could only ever be a very small yet fairly expensive part of a larger plan to reduce carbon emissions, and that the opportunity costs may be quite high. And that's without diving into the very real concerns about nuclear safety and disposal of radioactive materials—all areas that need real improvements, as this paper by Matthew Bunn of the Belfer Center summarizes in a non-shrill fashion.