Stimulating investment in pearl farming in ... - World Fish Center

Water Temperature and Cyclone Frequency in the Pacific: Implications for Pearl Farming Final, June 20083.3 The Influence of Climate Change on Tropical CyclonesThe effects of global warming on the characteristics and behaviour of tropical cyclones alsoneed to be considered. On a global scale, there is considerable uncertainty about theinfluence of global warming on cyclone frequency, but a general acceptance that tropicalcyclone intensities will increase. The latest report on climate change in Australia indicatesthat there is likely to be an increase in the proportion of the tropical cyclones in the moreintense categories, but a possible decrease in the total number of cyclones (CSIRO 2007). Thecomputer modelling studies undertaken by Walsh et al. (2004) and Leslie et al. (2007) suggestthat there will be no significant change in the number of tropical cyclones off the east coastof Australia to the middle of the 21 st Century. The simulations made by Abbs et al. (2006),however, indicate that there will be a significant decrease in numbers of cyclones,particularly off the west coast. All three studies agree that there will be a marked increase inthe frequency of severe tropical cyclones. The projections made by Abbs et al. (2006) andLeslie et al. (2007) suggest that cyclones will be more long-lived on the east coast. Abbs et al.(2006) indicate that there will also be a decline in long-lived cyclones off the west coast.In the South Pacific region, global warming is predicted to have some or all of the followingeffects on tropical cyclone activity:• Change the origin of cyclones so that there is less clustering and more spreading to theeast than at present;• Little change in total cyclone numbers or frequencies, but more storminess east oflongitude 180°;• Increase in the intensity of tropical cyclones, with lower central pressure and greatermaximum wind speeds;• Greater precipitation;• Longer cyclone lifespans;• More southerly trend in cyclone tracks; and• Longer cyclone tracks with greater southward movement prior to decay (Terry 2007).3.4 Impact of Tropical Cyclones3.4.1 General ImpactsThe gale force winds accompanying cyclones can cause extensive property damage, turnairborne debris into potentially lethal missiles, and produce heavy seas which are dangerousto vessels at sea and in harbours and cause serious erosion of foreshores (Bureau ofMeteorology, Australia 2007a). The heavy rainfall that occurs as the cyclone passes over canproduce extensive flooding which can in turn cause damage. Heavy rain can persist as thecyclone moves into central and southern parts of Australia and cause flooding inland. Themost potentially destructive phenomena associated with tropical cyclones are storm surges,raised domes of water about 60 to 80 km across and 2 to 5 m higher than the normal tidelevel. If the arrival of a storm surge coincides with a high tide it can cause extensiveinundation of the coast, particularly in low-lying areas.The Ecology Lab Pty Ltd – Marine and Freshwater Studies Page 14