Efficiency isn’t just some economists’, or accountants’, insistence on doing things cheaply. As Stern himself notes, if we do this inefficiently then we’ll avert less of that warming. The more resources we devote to growing mushrooms the fewer we’ll be able to expend upon the real problem. The more you worry about global warming the more you should be pushing for the most efficient solution — market forces properly incentivised — and the further you’d like politicians from the subject.
That, unfortunately, is not how things have worked out. The biggest problem with the climate change debate is that those most insistent that something must be done are those most insistent that the wrong something is done. That isn’t quite the way we’d hope to deal with the greatest threat to our civilisation. Or even the manner we’d like to deal with any problem at all.
Now that we’ve made the mistake of trying those centralised plans, can we get on with solving that climate change problem? Stick on the carbon tax and allow market forces to chew through the problem? As Hayek would have told us to, as Stern actually did insist, as the manner we’ve splashed the cash so far tells us we should have done.