The risk of river flooding might grow fourfold by the end of the century if global warming reaches its maximum estimate, according to a government report summarizing a study on the impact of climate change on Japan.

Tide-based risks also may climb because rising ocean levels are set to increase the amount of land at sea level around Tokyo, Osaka and Ise Bay, between Mie and Aichi prefectures, by some 50 percent, the report released Friday by the Environment Ministry, the science ministry and the Meteorological Agency said.

According to the findings, Japan's average temperature is forecast to rise between 2.1 and 4.0 degrees by 2100 compared with the end of the 20th century, depending on progress in combatting global warming.

An official at the Environment Ministry said the report showed the severity of the potential domestic impacts of climate change. The government is aiming to compile a plan by March 2015 on measures to reduce damage from global warming.