11.2.4.5. Tropical Cyclone and Storm Surges

Asia is close to the warm pool of the west equatorial Pacific Ocean, and tropical cyclones and associated storm surges strongly affect coastal zones of tropical and temperate Asia. Tropical cyclones and storm surges are one of most critical factors affecting loss of human lives in India and Bangladesh (Sato and Mimura, 1997). Approximately 76% of the total loss of human lives from cyclonic storms has occurred in India and Bangladesh (Ali, 1999). Several Asian countries are faced with cyclones and associated storm surges every year, which causes serious economic losses (Ali, 1999; Huang, 1999; Kelly and Adger, 2000).

There is concern that global warming may affect tropical cyclone characteristics, including intensity, because SST plays an important role in determining whether tropical disturbances form and intensify. Several researchers have used modeling techniques to examine the possible effects of global warming on tropical storms (Lighthill et al., 1994; Sugi et al., 1996; Henderson-Sellers and Zhang, 1997; Holland, 1997; Tonkin et al., 1997; Henderson-Sellers et al., 1998; Knutson et al., 1998; Krishnamurti et al., 1998; Royer et al., 1998). Lighthill et al. (1994) conclude that there is no reason to expect any overall change in global tropical cyclone frequencies, although substantial regional changes may occur. Recent studies indicate that the maximum potential intensities of cyclones will possibly undergo a modest increase of as much as 10-20% in a warmer atmosphere (see Chapter 3 and TAR WGI Chapter 9). More recent analyses (Nakagawa et al., 1998; Walsh and Pittock, 1998; Jones et al., 1999) support the possibility of an increase in cyclone intensity. Coastal erosion in Asia should increase with sea-level rise, and storm surges could still exacerbate hazards, even if the number and intensities of tropical cyclones do not change (IPCC, 1998; Walsh and Pittock, 1998).

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