The relationship between climate change and ENSO is not yet well understood (e.g. Hoerling and Kumar 2003). This has significant implications for the possible effects of climate change on tropical cyclones, since cyclone formation in a number of basins strongly depends upon ENSO variations (Lander 1994; Goldenberg and Shapiro 1996; Chia and Ropelewski 2002). For instance, in the Australian region, the number of tropical cyclones affecting the east coast is four times as large in La Nina conditions than during El Ninos (Walsh and Syktus 2003). Thus any substantial change in ENSO characteristics in a warmer world has the potential to affect tropical cyclone occurrence in many parts of the world.

Walsh (2004) recently reviewed the general topic of the influence of climate change on tropical cyclones. While several different techniques suggest an overall increase in tropical cyclone intensity in a warmer world, there is little consensus on the influence of global warming on tropical cyclone numbers. Crucial to our improved understanding of this issue are achieving climate model simulations of ENSO that closely resemble observed ENSO. Another significant task is to achieve climate model simulations of tropical cyclones that are genuinely realistic. Here, new simulation results are presented from an improved version of a regional climate model, examining the simulated variations of tropical cyclones in the current climate and their possible changes in a warmer world.

References

Chia, H.H., and C.F. Ropelewski, 2002: The interannual variability in the genesis location of tropical cyclones in the northwest Pacific. J Climate, 15, 2934-2944.

Goldenberg, S.B., and L.J. Shapiro, 1996: Physical mechanisms for the association of El Niņo and West African rainfall with Atlantic major hurricane activity. J Climate, 9, 1169-1187.

Hoerling M., and A. Kumar, 2003: The perfect ocean for drought. Science, 299, 691-694.

Lander, M.A., 1994: An exploratory analysis of the relationship between tropical storm formation in the western north Pacific and ENSO. Mon. Wea. Rev., 122, 636-651.

Walsh, K., 2004: Tropical cyclones and climate change: unresolved issues. Climate Research, in press.

Walsh, K.J.E. and J. Syktus, 2003: Simulations of observed interannual variability of tropical cyclone formation east of Australia. Atmospheric Science Letters, 1-4, 28-40.