The Economist has an excellent briefing on climate change science. It makes a central point that often seems to get lost, that the laws of thermodynamics and the nature of carbon dioxide alone provide a good basis to expect the world to heat up if human beings pump more carbon dioxide into the atmosphere. It then looks at the question of how much the world should be expected to heat up, given the amount of carbon dioxide that we have in fact emitted. The answer is “not very much” if the world is modelled as a simple object with an uninteresting atmosphere, and ranges from “rather more” to “far too much” if climate models are extended to include various feedback effects. The academic debate about climate change is about the climate models.

The Economist, as it sometimes does, reaches the same conclusion as me about climate change: given the current state of science, the probability of very bad outcomes from continued carbon emissions is sufficiently high to justify action to reduce global emissions. The question then becomes — how much action? The answer cannot be purely scientific, because it depends on both the predictions of climate models and the discount rate on future unpleasantness. The latter is a political question.

Update: If you have a subscription, the link is here. The piece is so good that it’s worth buying the magazine this week just to read it.