This idea should work, it's called a heat sink, and it's discussed in the book Superfreakonomics . The proposal here in the US is for huge rings (of recycled material, maybe old car tires) surrounding a center tube that reaches down into the ocean. As the waves wash over this giant jellyfish-like structure, the warm water at the surface gets cooled by the colder water below, and the big Atlantic hurricanes lose power. No one has built one here yet, but if the Japanese put their idea out there and it works, I'm sure we'll be trying it too.