More than $400 billion needed to build seawalls to protect U.S. cities

Three Arch Bay, Laguna Beach, California, 2015. Credit: D Ramey Logan/CC BY 4.0.

It would cost $416 billion to build enough seawalls to protect American cities against rising sea levels. That's according to a new report by the Center for Climate Integrity. It says protecting California alone would cost an estimated $20 billion.