Conclusion

In this book we have reviewed empirical methods in short-term climate prediction. We devoted a whole chapter to the design of two of these methods, Empirical Wave Propagation (EWP, Chapter 3) and Constructed Analogue (CA Chapter 7). Other methods of empirical prediction were listed in Chapter 8, with brief descriptions and examples and references. One chapter is devoted to EOFs, as such a diagnostic topic, but widely used in both prediction and diagnostics, and thoroughly debated for a few decades. Two brief chapters, written in support of the subsequent chapter, Teleconnections (Chapter 4), should make the discussion on EOFs more interesting, and the topic of effective degrees of freedom (Chapter 6) is indispensable when one wants to understand why and when natural analogues would work (or not), or how an analogue is constructed, or how any method using truncation works. Most chapters can be read largely in isolation, but connections can be made of course between chapters. EWP is claimed to be useful, if not essential, in understanding teleconnections. Dispersion experiments, featuring day-by-day time-scales, link the CA and EWP methods. Examples of El Nino boreal winter behavior can be found in (a) the examples of EOFs on global SST and 500 mb streamfunction (Chapter 5), (b) specification of surface weather from 500 mb streamfunction (Chapter 7), and (c) the ENSO correlation and compositing approach (Chapter 8). The noble pursuit of knowledge may have been as important in the choice of some material as any immediate prediction application. Chapter 9 is different, less research oriented, and more an eyewitness description of what goes on in the making of a seasonal prediction. This eyewitness account style spills over into Chapter 8 here and there, because in order to understand why certain methods have survived to this day some practicalities have to be understood. The closeness to real-time prediction throughout the book creates a sense of application. However, the application in this book does not go beyond the making of the forecast itself; we completely shied away from such topics as a cost/benefit analysis or decision-making process by, for example, a climate sensitive potato farmer or reservoir operator.