The Regional Impacts of Climate Change

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9.2.3.2. Extreme Events and Interannual Variability

Various studies have attempted to assess possible climate change-related changes in extreme events, but few assessments have focused specifically on small island states. Several models, for instance, project an increase in precipitation intensity, runoff, and possible flooding for latitudes within which many of the islands are located. In a few cases, the possibility of change in the occurrence of droughts also has been projected. Given the constraints of scaling and resolution in the models with respect to small islands (see Section 9.2.3.1.) and the current status of inter-model agreement, however, such projections must be considered inconclusive at this stage.

A major ongoing concern for many small island states is whether global warming will lead to changes in the character and pattern of tropical cyclones (i.e., hurricanes and typhoons). Unfortunately, model projections suggest no clear trend, so it is not possible to state whether the frequency, intensity, or distribution of tropical storms and cyclones will change (IPCC 1996, WG I, Sections 3.5.2.3, 3.5.3.1, 3.5.3.2). Within the past few decades, an increase in the number of tropical cyclones also has been reported in the southWest Pacific, with the greatest increase in stronger cyclones (see Figure 9-2f). It should be noted, however, that some doubts exist about the homogeneity of the data base, due in part to recent improvements in observation capabilities (Thompson et al., 1992; Radford et al., 1996).

Gray (1993) reports that, based on historical data for the Caribbean Sea, increases in sea-surface temperature of 1.5C have been associated with an increase in hurricane frequency. Although there is some uncertainty in the data base, projected increases of this magnitude represent approximately 40% more hurricane activity than normal. More recently, Holland (1997) projects that the intensity of tropical cyclones could increase by 10-20% under 2xCO2 conditions. In contrast, observed data suggest that, in the vicinity of longitudes 105-160E (in the region of Australia), the total number of tropical cyclones between 1969-70 and 1995-96 has decreased, although there were slight increases in the number of strong systems and the duration of the cyclones (Nicholls et al., 1997).



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