Global warming will cause the amount of heavy rain dumped on Taiwan to triple over the next 20 years, facing the government with the urgent need to beef up flood defences, a scientist warned Tuesday.

The projection is based on data showing the incidence of heavy rain has doubled in the past 45 years, coinciding with a global rise in temperatures, said Liu Shaw-chen of Taiwan's leading research institute Academia Sinica.

The estimate comes two months after Taiwan was lashed by Typhoon Morakot, the worst to hit the island in half a century, leaving more than 600 deaths in its wake.

"The government will need to enhance its land planning and flood prevention measures since we'll be seeing more and more Typhoon Morakots in the future," said Liu, who heads the institute's Research Center for Environmental Changes.

The island's temperature has also been going up, reflected in figures from the capital city Taipei, where the number of days with "excessive heat" over 36 degree Celsius (97 degrees Fahrenheit) has doubled since 1961, he said.

Morakot struck Taiwan in early August, unleashing a record three metres (10 feet) of rain, triggering widespread flooding and massive landslides.

The island's government faced a wave of public anger over its handling of the disaster, plunging President Ma Ying-jeou into his worst political crisis since taking office in May 2008.