Hurricane Intensity Prediction System (CHIPS) is described and used to simulate hurricane behavior in the western Atlantic basin. In a first step, the points of origin for thousands of synthetic TC tracks were generated by randomly drawing from a probability distribution estimated from the post‐1970 best track Atlantic hurricane data. These synthetic TCs were then moved according to a set of prescribed winds varying in space and time (Figure 6.19). In a final step, local environmental conditions (SSTs, wind shear, etc.) were then used to calculate the intensity of each hurricane along its path.
Using this method, Emanuel (2006b) showed: (1) that the frequency distribution of synthetic TCs in the current simulated climate as a function of peak wind speed, Vmax, is very similar to the corresponding distribution for observed TCs (Figure 6.20, left); (2) that a 10% increase in potential intensity, corresponding to a future SST increase of approximately 2.5°C, leads to a noticeable increase in the relative number of intense hurricanes (as characterized by peak wind speed along the synthetic track; Figure 6.20, right), and; (3) the PDI increases by 65% in response to the 10% increase in potential intensity.
Figure 6.19. Sixty random tracks from the synthetic hurricane generator (left), and (right) historical TC (HURDAT) data. Source: Emanuel et al., (2006).
As noted in Sec. 4.3.1, most TC modeling studies spanning the historical and future periods do not predict noticeable trends in number, intensity, and other properties until the mid-21st century. This is consistent with the above results, which are representative of conditions projected for the late 21st century. Based on these studies and many others addressing TCs and extratropical cyclones, the recent literature reviews by Knutson et al., (2010) and the IPCC-SREX Report (2012) found remarkable consistency with regard to projected TC properties. According to the SREX-SPM (emphasis in the original): Average tropical cyclone maximum wind speed is likely to increase, although increases may not occur in all ocean basins. It is likely that the global frequency of tropical cyclones will either decrease or remain essentially unchanged. … There is medium confidence that there will be a reduction in the number of extratropical cyclones averaged over each hemisphere. While there is low confidence in the detailed geographical projections of extratropical cyclone activity, there is medium confidence in a projected poleward shift of extratropical storm tracks.
Determining the Impact of Climate Change on Insurance Risk and the Global Community
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