Notes to chapter

1. As argued by Czaja & Frankignoul (2002).

2. Few acronyms are pleasing to the ear, perhaps because they are forced words. Think how ugly the acronyms ENSO, QUANGO, SAT, NASDAQ, GIF, JPEG, and MS-DOS are. A few exceptions, notably radar and laser, do have a certain euphony and have become accepted as true words with no need for capitalization.

3. The name El Niño was originally used by fishermen along the coasts of Ecuador and Peru to refer to a warm ocean current that usually appears around christmas and lasts for several months. These days, the name has come to refer only to those events in which the warming is particularly strong.

4. For example, the definition given by Trenberth (1997) is that an El Niño occurs if the five-month running means of sea-surface temperature (SST) anomalies in the Niño 3.4 region (5° N-5° S, 120° W-170° W) exceed 0.4°C for six months or more.

notes to chapter 7

5. Figure kindly provided by A. Wittenberg. The observations are mainly from satellites and are passed through a NOAA optimal interpolation analysis.

6. Figure kindly provided by Andrew Wittenberg, with data from http://www.cgd.ucar.edu/cas/catalog/climind/ soi.html. See also Wittenberg (2009). The SOI index is probably quantitatively unreliable before about 1935.

7. See Tudhope et al. (2001) for discussion of a long coral record, and DArrigo and Jacoby (1991) for a tree-ring record.

8. Gilbert Walker (1868-1958) may also be credited with discovery of the Southern oscillation and the North Atlantic Oscillation. Walker began his career as an applied mathematician but made greater contributions, and gained greater fame, by analyzing meteorological observations.

9. The onset of an El Niño involves the westward propagation of Rossby waves and their reflection at the western boundary and return as Kelvin waves. More detailed accounts are to be found in books by Philander (1990), Clarke (2008), and Sarachik and Cane (2010).

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