Mechanisms for Decadal-to-Centennial Climate Variability

We really don’t understand what causes decadal-to-centennial climate variability although we have some rudimentary ideas about the possible mechanisms. Which mechanism operates implies the existence and range of possible predictability. These lectures, therefore, have two purposes: 1) to look at the evidence for the various proposed mechanisms and see if any can be chosen as most likely (or if any can be rejected and thereby eliminated from further consideration) and 2) to see which of the mechanisms imply predictability of the decadal variability and which are intrinsically unpredictable. The variety of mechanisms is diverse, and, to save the reader from turning to the end to see how the story turns out, none can be totally eliminated at this stage. Indeed, more than one mechanism may apply at any given time at various places on the globe. It is impossible to be exhaustive in lectures of this type, so it is hoped that these lectures will serve as a guide to the ideas and literature of a field that is rapidly catching on as the realization takes hold that natural variability of the climate is omnipresent and important, and may be predictable.