When the facts change, I change my mind – what do you do?
This quote is attributed, perhaps spuriously to Keynes. A sharper version of the same point is made here by Noah Smith, exploring the concept “Derp”, “”the constant, repetitive reiteration of strong priors”, where “strong priors” in the technical Bayesian sense, mean that ” … you really, really believe something to be true. If your start off with a very strong prior, even solid evidence to the contrary won’t change your mind. ”
A notable example of this, very relevant on this blog, and cited by Smith, is the cost of solar energy. Roughly speaking, the cost of solar modules has fallen by a factor of 10 over the past few years, and the cost of installed systems by a factor of three. If that hasn’t changed your mind about the relative merits of alternative policy option, then you must have really strong priors, and in that case, you shouldn’t be engaging in debate, since your mind can’t be changed by evidence. As Smith observes, “That is unhelpful and uninformative, since they’re just restating their priors over and over. Thus, it is annoying. Guys, we know what you think already.”
But, it’s easy to throw stones, so I thought I would check my own archives to see if I was guilty of Derping on this point. Here is what I thought in 2004
Nuclear (fission) power is probably the cheapest large-scale alternative electricity source (there are some sites where wind is cost-competitive, and similarly for geothermal) but it is still a good deal more expensive than coal or gas. How much more expensive is hard to tell because the industry is riddled with subsidies, but I’d guess that the full economic cost is about twice as high for nuclear electricity as for coal or gas. Moreover, most recent construction has been in places like China and Korea where safety standards may not be as high as they would have to be to get nuclear energy restarted in the developed world as a whole.
What this means is that nuclear power won’t enter into calculations until we have a carbon tax (or equivalent) steep enough to double the price of electricity. It’s clear though, that much smaller increases in costs would make a wide range of energy conservation measures economically viable, as well as reducing final demand for energy services. Implementing Kyoto, for example, would not require anything like a doubling of prices. Whether or not a more radical response is justified, it’s clearly not going to happen for at least a decade and probably longer.
Nevertheless, if mainstream projections of climate change turn out to be correct, and especially if, as Lovelock suggests, they turn out to be conservative, we’ll eventually face the need for new sources of electricity to replace fossil fuels. Solar photovoltaics are improving fast but still a long way from being cost-competitive. So it may well be that, at least for an interim period, expansion of nuclear fission is the best way to go.
I didn’t mention carbon, capture and storage, but I also supported that as a good option for Australia, assuming it could me made to work.
The facts have changed, and I have changed my mind. I now think the role of renewables, and particularly solar is going to be much larger than seemed likely ten years ago, nuclear much less, and CCS marginal.
Update Obviously, this post was intended to provoke a reaction from the critics of renewable energy (normally, also advocates of nuclear) who regularly comment here, challenging them to say how they had adjusted their views in the light of the evidence of the last decade. Most commenters responded thoughtfully. But our single-topic nuclear fans, Hermit and Will Boisvert, responded by herping even more flerps of derp. Despite being reminded of the topic, they just kept on pumping out the same constant, repetitive reiteration of their priors that defines derp. This does, at least provide me with some guidance. From now on, comments from single-issue pro-nuclear commenters (specifically, the two mentioned) will be deleted unless they contain a point that has not been made previously or (highly improbably) a change of view.