“Consider Fig. 1 showing the negative of the anomaly of atmospheric pressure in Darwin, Australia and used by Trenberth and Hoar (1997) as a measure of the strength of the Walker circulation. Fig. 2 displays the sea surface temperature (SST) Niño3.4 index commonly used as a measure of the strength of El Niño. Trenberth and Hoar(1997) infer that ENSO behavior shifted after about 1970 to more frequent and larger El Niño events. (The change was interpreted as the result of global warming and to be “unprecedented” in the historical record.) Solow (2006), however, noted that their anomalous test period, 1992-mid-1995, in Fig. 1 was not independent of the earlier interval of supposedly normal behavior; he used the subsequently longer record to recalculate the probability that the nature of ENSO had changed in some significant way. His conclusion was, in contrast, that while the test period appears different from the earlier one, subsequently there was essentially no evidence that the nature of the physics had changed. The comparatively dramatic story of the original authors is thus replaced by a much more ambiguous and unexciting, but presumably more soundly-based,description of the nature of ENSO.”
Abstract: The human eye and brain are powerful pattern detection instruments. Coupled with the clear human need to perceive the world as deterministic and understandable, and the often counter-intuitive results of probability theory, it is easy to go astray in making inferences. In particular, many examples exist where attention was called to apparent extreme behavior, whether in time or space series, or in the appearance of unusual patterns, that are just happenstance. Used carefully, and with a residual open-mindedness, it is possible to employ some simple statistical tests to avoid the outcomes of inferring unusual behavior where none is present, nor in rejecting a major finding as being insignificant.
Climate Audit: ‘Carl Wunsch on Self-Deception’