11.9.5 Tropical Cyclones

Fewer models have simulated tropical cyclones in the context of climate change than those simulating temperature and precipitation changes and sea level rise, mainly because of the computational burden associated with the high resolution needed to capture the characteristics of tropical cyclones. Accordingly, there is less certainty about the changes in frequency and intensity of tropical cyclones on a regional basis than for temperature and precipitation changes. An assessment of results for projected changes in tropical cyclones is presented in Section 10.3.6.3, and a synthesis is given at the end of the section. Regional model-based studies of changes in tropical cyclone behaviour in the southwest Pacific include works by Nguyen and Walsh (2001) and Walsh (2004). Walsh concludes that in general there is no clear picture with respect to regional changes in frequency and movement, but increases in intensity are indicated. It should also be noted that ENSO fluctuations have a strong impact on patterns of tropical cyclone occurrence in the southern Pacific, and that therefore uncertainty with respect to future ENSO behaviour (see Section 10.3) contributes to uncertainty with respect to tropical cyclone behaviour (Walsh, 2004).