Tropical Cyclone Changes in the Western North Pacific in a Global Warming Scenario

Abstract The influence of global warming on the climatology of tropical cyclones in the western North Pacific basin is examined using the high-resolution International Pacific Research Center (IPRC) regional climate model forced by ocean temperatures and horizontal boundary fields taken from the NCAR Community Climate System Model version 2 (CCSM2) coupled global climate model. The regional model is first tested in 10 yr of simulation with boundary forcing taken from observations and is shown to produce a reasonably good representation of the observed statistics of tropical cyclone numbers and locations. The model was then run for 10 yr with forcing from a present-day control run of the CCSM2 and then for 10 yr with forcing fields taken from the end of a long run with 6 times the present-day atmospheric CO2 concentration. The global-mean surface air temperature warming in the perturbed run is 4.5 K, while the surface warming in the tropical western North Pacific is about 3 K. The results of these experiments reveal no statistically significant change in basinwide tropical cyclone numbers in the peak season from July to October in response to the CO2 increase. However, a pronounced and statistically significant increase in tropical cyclone occurrence in the South China Sea is found. While the basinwide total number of storms remains nearly unchanged in the warm climate, there is a statistically significant increase in the average strength of the cyclones and in the number of the storms in the strongest wind categories.