The finding was reached by Johnny C L Chan, a meteorological expert from Hong Kong, who have studied the relationship between the sea-surface temperature (SST) and observed tropical cyclone intensity over the western North Pacific for the past 50 years.

The intensity of tropical cyclones was greatly affected by the change of SST over the equatorial eastern Pacific Ocean, but had no obvious and direct connection with the effect of global warming, said Chan.

However, global warming modified the large-scale weather circulations that were responsible for the development, intensification and movement of tropical cyclones, he said.

Tropical cyclones with violent winds, torrential rain and fierce storm surges are typical weather events. China has suffered more serious tropical cyclone damage than other countries, said Chen Lianshou, an expert with the Chinese Academy of Meteorological Sciences.

Figures show about 40 percent of 753 typhoons in the Asian-Pacific Region, or 347, had struck China from 1949 to 1997. This extreme meteorological phenomenon has cost the country several billion US dollars each year.

"Sudden changes of the tropical cyclones, such as the turning of storm motion direction, the speeding up or slowing down of motion velocity and the increased storm rainfall after landing are critical issues for disaster prevention and preparedness," Chen said.

Some other reports at the symposium suggested that besides the SST, tropical cyclones also have close relations with El Nino and La Nina events and the variation of atmospheric general circulation.

"All of those are strongly influenced by global warming," said Chen, "so we should study what trends of tropical cyclone frequency and intensity will be in the next few decades under this global trend."

Experts at meeting urged the study in this field should be encouraged by the World Meteorological Organization and be carried out with more international cooperation.

(Xinhua News Agency April 2, 2003)