Notes on a catastrophe - surface albedo feedbacks and the descent into a Snowball Earth (Invited)

The language of feedbacks is ubiquitous in contemporary Earth Sciences, and the feedbacks framework is a powerful analysis tool for diagnosing the relative strengths of the myriad mutual interactions that occur in complex dynamical systems. The ice albedo feedback is widely taught as the classic example of a climate feedback, and its potential to initiate a collapse to a completely glaciated “Snowball” Earth is widely taught as the classic example of a climate tipping point. A feedback analysis of the Snowball Earth phenomenon in simple energy balance models clearly reveals the physics of the snowball instability, and can be used to illustrate some fundamental properties of climate feedbacks: how feedback strength changes as a function of mean climate state; how small changes in individual feedbacks can case large changes in the system sensitivity; and finally, how the strength and even sign of the feedback is dependent on the climate variable in question.