Just after 5 a.m. on Aug. 30, water began flooding a vast underground chamber called the "cathedral" in Saitama Prefecture. The gushing water, captured by security cameras, was the rain that was drenching the region around Tokyo as Typhoon Shanshan lashed southwest Japan, 600 kilometers away.
The cathedral and its vast network of tunnels did their job: they prevented a vulnerable river basin in the metropolis from flooding. But as global warming causes more severe weather, authorities are having to give the system a major upgrade.
"As the temperature rises, the amount of water vapor in the atmosphere increases, resulting in relatively larger quantities of rainfall," said University of Tokyo professor Seita Emori, who is a member of a climate science group that won a Nobel Prize in 2007.
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