Hansen looks at everything according to CO2 emissions. The life cycle CO2 emission profiles of nuclear and gas power plants are very different, due to the CO2 emitted during construction. The overnight cost of a nuclear plant is 5 to 6 times higher than an IGCC plant, so the CO2 emissions of construction can be expected to be higher by a similar factor. So it takes a while for the construction emissions of a nuclear plant to be offset by its lower operating emissions.
I can't imagine that the carbon footprint of nuclear power plant construction has escaped Hansen's notice - he's a fairly astute guy, after all. I suspect what's happened is he's concluded that it's a short term price worth paying for a long-term gain. I noticed a radical shift in my own assessment of nuclear power as I came to accept the high probability of a near-term loss of structural integrity in global civilization (how’s that for a fancy dance to avoid saying the word “collapse”?).
When I still thought things were going to keep on trucking for quite a while I was much less opposed to nuclear power. Then I figured out three things: we are in the grips of climate change, with the threat that poses to social stability; we are losing integrity already because of rising net energy costs (part of which is due to peak oil); and I finally understood that an unattended nuclear plant is a monumental due to the impact of environmental accidents (which brings up the “400-Fukushima” scenario). In the face of all that, nuclear power is an absolute non-starter.
Hansen gets climate change, but he hasn't yet grokked near-term collapse and the risk it poses to reactors. So he’s against fracking because of the climate, but he’s willing to accept the short-term carbon cost of a nuclear build-out. He believes that nuclear is the only scalable, high-density, low-operating-CO2 energy source that will keep civilization’s lights on. His risk assessment of fracking is correct, but his risk assessment of nuclear power is faulty. Such is the nature of belief – it gives rise to all kinds of inner contradictions. His cognitive dissonance in the face of Fukushima must be enormous.
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