The unchecked progress of global warming would increase the risk of flooding at the end of this century in 42 percent of the Earth's land surface, mainly in Asia and Africa, according to a study published Sunday by British science journal Nature Climate Change.
The number of people exposed to the risk of flooding would increase from the current estimate of 5.6 million to 80 million by 2100 if temperatures rise by 3.5 C degrees during the period, said a research team led by Yukiko Hirabayashi at the University of Tokyo's Institute of Engineering Innovation.
The frequency of flooding would increase "across large areas of South Asia, Southeast Asia, Northeast Eurasia, eastern and low-latitude Africa, and South America," the study said.
But flood frequency is projected to decline in certain areas covering 18 percent of the land surface, it said.
The research team made the projections based on the output of 11 existing climate models and its own program designed to forecast river inundation.
If global warming progresses without effective countermeasures, many of the world's 29 major rivers would see massive floods, which currently occur once a century, at an increased frequency of every 10 to 50 years, the team said.
It pointed to the need to consider flood risks in setting targets for reducing greenhouse gas emissions.