Introduction - The Global Climate System: Patterns, Processes, and Teleconnections - page 14

Figure 1.7 The wide range of weather and climate conditions in Australia during an El Ni˜o year. (Based on information
originally from www.bom.gov.au)
used. However, as Katz (personal communication) noted, ''the entire record
is more often relied on when estimating extremes (as opposed to averages)''.
The better the instruments that are used to measure climate characteristics,
the more reliable the information collected. The longer the record, the better the
analysis is likely to be. Data for many places, however, are not very reliable,
because data collection can be and has been disturbed by (a) moving the location
of measurement, (b) urban modification of the local climate, (c) disruption of
data collection as a result of conflict, or (d) failure of the measuring devices, etc.
Nevertheless, the past hundred years or so of data is considered to be relatively
robust and reliable for a statistical definition and assessment of normal local to
national climates for several countries. Normal climate, however, can also be
based on an individual's perceptions of actual climate conditions.
Perceptual definition
Most people weigh the climate anomalies that occurred earlier in history less
heavily than recent events. They also weigh more heavily the ones they have