The Tokyo-based university issued the warning as it prepared to open an institute in Bonn, Germany, to study the impact of the environment on human security. The institute's goal is to help governments better cope with natural disasters.

The world will be warmer and wetter by mid-century, and the northern part of the Northern Hemisphere will likely see more storms, said Dr. Janos Bogardi, founding director of the new institute, in the study made public by the university.

Sea levels could rise, fed by melting glaciers and ice caps, and extreme high-water levels could become more common, menacing small islands and coastal lowlands, he said.

Floods already kill as many as 25,000 people a year and - along with other weather-related disasters - cost the world economy up to $60 billion a year, much of it in developing nations ill-equipped to cope with such huge costs, the experts said.

"Most urgently needed to adapt to the growing risk of flood disasters is greater global capacity to monitor and forecast extreme events," Bogardi said. "Armed with better information, superior early warning systems and infrastructure can be installed and new planning strategies devised," he said.

The U.N. University was established by the 191-nation General Assembly in 1973 to foster an international community of scientists looking into global problems.