Where did Stern get that: Rapid climate change

Avoiding economics, one of the places where critics of the Stern report are ..... ummm... unsatisfied is the high probability of catastrophic change that is assumed. The roots of this go back to the position paper by Arnell commissioned by Stern. Unfortunately this too has very cursory discussions of the probability of such events being more concerned with their consequences (awful as you might imagine). Two possible catastrophes are considered, collapse of the thermohaline circulation and rapid global temperature rise driven by whatever (for example large releases of methane).

As Arnell notes, almost all modeling considers collapse of the thermohaline circulation as improbable although a slowdown may occur. Arnell points to two modeling studies which hold that collapse has a significant probability, one by Schlesinginger, et al (Yohe being one of the al) and the other by Challenor, et al. , both from the conference on Avoiding Dangerous Climate Change. The third strand in Arnell's argument is a survey of experts where the panel was all over the place (mostly at the exits), but whose results were spread all over the spectrum. Both of the modelling papers were very careful to say that the models they used were too simple, and that the results could be overturned by more detailed calculations.

So where does that leave us who know it all? Well, probably at the point where we begin to think that those who know there is no risk of catastrophic climate change don't know it all, but not convinced. A Scotch verdict (not proven) is probably the right judgement, but this is of no real help right now. A better question might be how much insurance should we take out.